BOUGHT WITH THE INCOME OF THE SAGE ENDOWMENT FUND THE GIFT OF Mcnv^ M. Sage 1891 BL^'^:i=ryj^>o- :- ib\A>Jl.\jb> The original of tiiis book is in tine Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924003893074 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS UNDER THE CONTROL OF THE TREASURY DEPARTMENT (THIRD REVISED EDITION) BY NELSON S. THOMPSON Chief Mechanical and Electrical Engineer, Office of the Supervising Architect, Washington, D. C. NEW YORK HEATING AND VENTILATING MAGAZINE CO. 1123 BROADWAY In presenting to the public the basic data used in designing the Mechanical Equipment for buildings under the control of the Treasury Department, I desire to give credit to N. R. Stansel, M. S. Cooley, H. M. Price, D. F. Atkins, A. R. Horn, H. C. Russell, E. L. Wilson, E. C. Stanton, C. R. Bradbury, J. L. Vawter, Myers Hand and L. A. Warren for their valuable contributions. NELSON S. THOMPSON Chief Mechanical and Electrical Engineer, Office Supervising Architect, Treasury Department Copyright, 1915, by Heating and Ventilating Magazine Co. CONTENTS CHAPTER I. Heating and ventilation 1 II. Commercial practice in regard to heating factory and other buildings 75 III. Commercial practice in regard to heating by forced circulation of hot water from a central station 124 IV. Plumbing, drainage and water supply 137 V. Gas piping 193 VI. Conduit and wiring systems 197 VII. Lighting fixtures 225 VIII. Elevators 235 IX. Small power plants 278 X. Motors and controlling apparatus 306 XI. Vacuum cleaning systems 316 XII. Operating data 343 Appendix — General instructions 363 Suggestions to superintendents 373 Miscellaneous data 383 Index 399 CHAPTER I HEATING AND VENTILATION The office of the Supervising Architect, Treasury Department, used to install gravity indirect steam or hot water in practically all the smaller buildings which it erected, except where conditions precluded gravity indirect, and then direct-indirect was installed. In the large buildings mechanical ventilation supplemented with direct radiation was installed. All office rooms in all buildings and all assembly rooms were provided with he at and vent flues, and the entire building (except corridors) was ventilated. During this period designers had no opportunity to inspect the installations, which was a serious drawback in their work. Ob- servation of the various steps in the care and operation of the mechanical and electrical equipment of completed and occupied buildings would have been of special value to them. When such opportunity was later granted it was discovered that the theo- retical advantages of the system outlined above as applied to the smaller buildings were not secured in practice. In most instances it was found that the fresh air ducts and the base of the gravity indirect radiator chambers were seldom or never cleaned and in most cities there was so much soot and dust in the atmosphere that the walls around registers were black. The air coming out of the registers had a bad odor, and in gen- eral the system was not satisfactory. The dry air fflters, which are alone practical with this system, proved most unsatisfactory.^ The manner of supplying air to the direct-indirect radiators was not satisfactory, and that system fell into disrepute on that account. Also, radiators froze in extreme cold weather. Duriug this period the Federal buildings were of massive con- struction, and the cost of the heating and ventilating apparatus in the smaller buildings was not disproportionate to the total ' It must be understood that the office of the Supervising Architect did not at this time have the power of selecting the engineers or firemen, and had no direct control of them after their appointment. 1 2 MECHAIsflCAL EQUIPMENT OP FEDERAL BUILDINGS cost of the building. Later, the massive masonry construction was abandoned and much cheaper buildings provided for, neces- sitating a reduction in the cost of the mechanical equipment. Contrary to the impression of the general public, unlimited funds are not available for the erection and equipment of goverimient buildings, and in the very large majority of cases it is necessary to reduce the cost of the mechanical equipment to the lowest point, eliminating everything not absolutely essential. Under the present policy in regard to new buildings, all the rooms have at least 1800 cubic feet of space for each and every occupant, and in most cases electricity is used for illumination; and the area of the exposed windows and doors is always at least one-fourth the area of the floor. The main assembly room (post- office workroom) is frequently flushed out by the opening of ex- terior doors to admit and dispatch mails. In view of the foregoing it was decided to eliminate the venti- lating apparatus in the smaller buildings which were not provided with court rooms. In practically all the smaller buildings the steel smokestack of the boiler is placed inside of a brick shaft, and into this shaft openings provided with top and bottom reg- isters are made which serve to draw air from the post-office work- room, the large basement toilet-room, and the room in the base- ment in which the letter carriers remain when off duty. The small private toilet-rooms are used infrequently, and as they are provided with generous exterior windows vent flues are seldom installed. When a building contains a court room, gravity-indirect radia- tion is installed sufficient to change the air not less than twice an hour 'in court room, which is provided with a vent flue or flues, connected with the vent shaft. The court room is heated by direct radiation, the indirect merely heating the air to 75° F. Where conditions preclude the installation of gravity-indirect stacks for the court room direct-indirect radiators are installed to supply ventilation and vent flues as above noted are installed also. In the large buildings all the heating is done by direct radia- tion, and the fresh air is admitted to the rooms to be ventilated at about 75° F. The ventilation in the large buildings is con- HEATING AND VENTILATION 3 fined mainly to the postoffice workrooms and the court rooms (rooms in which a number of people assemble), and the principal office rooms. The advantages of this system are that the ventilating appara- tus may be shut down from, say, 6 p.m. to 8 a.m., and the direct radiation kept in service continuously in order to prevent the building cooling off. An accident to the fan motor does not cripple the entire heating and ventilating system as is the case with the straight hot-blast system. In the larger buildings the post-office section is in operation night and day continuously, and it is imperative that sufficient heat be obtainable at all times. In several of the large buildings constructed by the office in earlier days the vent flues from the office rooms were omitted, and the fresh air which was forced in by the fan found an outlet through crevices around windows and entrance doors. This is now overcome by installing metal weather-strips in all buildings provided with mechanical ventilation, and, wherever the con- struction permits, installing vent flues from the apartments sup- plied with fresh air. Even with metal weather strips, when air is admitted for ven- tilation only, it is not deemed absolutely necessary to install vent flues in each office room. The vent flues or registers provided in the assembly rooms and main toilet-rooms are ample to carry off all the air forced in by the fan. Vent registers installed in entrance doors from corridors are regarded as useless and unsightly. In all buildings equipped with a plenum fan the practice is to install an air washer, as such a device is looked upon as the most essential feature of a successful ventilating apparatus. The old ventilating apparatuses were a failure on account of the inability of the dry air filter to cleanse the air properly. In a test recently made by a representative of the office of the Supervising Archi- tect a new cheese-cloth filter reduced the delivery of the fan 25 per cent when air was passing through the filter at the rate of 2 feet per second. No heating and ventilating apparatus is complete without some means of absolutely and automatically controlling the tempera- ture of the apartments, and when funds are available a first-class 4 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS automatic temperature-controlling apparatus is installed in the larger buildings. Aside from the comfort thus assured, a saving of not less than 10 per cent in the coal pile may be secured. When it is certain that an automatic temperature-controlling apparatus is to be installed, the radiation is not split into small units as is the case when hand control only is to be used, and the reduction in the number of units offsets in a measure the cost of the automatic temperature-controlling apparatus. The method adopted by the office for controlHng the tempera- ture of the tempering and reheating coils when air for ventilation only is to be supplied is as follows: Provision is made for a by-pass damper or dampers under both the tempering and reheating coils. The dampers are made equal in area to not less than 10 per cent of the gross area of the coils and not larger than 15 per cent of said gross area. All dampers larger than 20 inches x 36 inches are made of the louvre type. The tempering coils are made deep enough to heat the air from the lowest local temperature on record to 67° F., and the reheat- ing coils deep enough to heat the air from 50° to 80° F. This arrangement allows for a 20° temperature drop due to air passing through the air washer. To control the tempered air a thermostat is installed in the cold-air chamber, and is set to open the first row of coils when outside air is 40° F. This' is a refinement which may be omitted if desired and hand-control valves only used on this section. Two thermostats are installed between the air washer and the secondary or reheating coils. One is set at 45° F. to shut off the inside row or rows of tempering coils when air reaches that tem- perature after passing through the air washer; the other is set at 47° F. and operates the by-pass damper under the tempering coils. These thermostats are placed beyond the air washer so that the air will not become too saturated in cold weather. The secondary coils are generally two or three sections deep, and one two-point thermostat is set near the fan inlet to control the steam inlet valves on same. One point of this multiple ther- mostat is set at 71° F. and shuts off the first row when air reaches that temperature; the second point is set at 7.3° F. and controls the second row of coils, or the second and third rows, as the case may be. A thermostat is also placed near the fan inlet and set HEATING AND VENTILATION 5 at 75° F., and when air reaches that temperature it opens the by- pass damper under the secondary heating coils. All thermostats have a range of 15° on each side of the point set, and those on the steam valves are positive and have a quick movement to open or shut the valves. The by-pass damper thermostats are of the gradual-moving or intermediate type. The control where a plenum chamber or school-house system is used is the same as noted above in so far as the tempering coils and the by-pass under same are concerned, but on the reheating coils no automatic control is used and the valves on coils are hand- control type, or diaphragm type controlled by hand by .three-way cocks. The temperature of the hot air is read on a thermometer in the hot-air chamber, and the engineer controls the reheating coils by hand. In the ordinary office rooms one thermostat is placed to control the direct radiation. In large court rooms and in post-office work- rooms two or more thermostats are placed, according to the judg- ment of the engineer in charge of the drafting room. When a hot-water heating system is equipped with an auto- matic temperature controlling apparatus, the diaphragm valve is placed on the return end of radiators. Complaints may be expected during the first season an auto- matic temperature-controlling apparatus is in use in a building, as the occupants throw the thermostats out of adjustment, owing to unfamiliarity with the workings of the system. As soon as they have acquired sufficient experience to avoid this, the appara- tus invariably gives satisfaction. Attention is called to the fact that the automatic temperature- controlling apparatus must be of the very highest grade, or it will be worse than useless. In connection with installing automatic temperature control on a low-pressure heating apparatus, the office will install an air- removal system with a water-operated vacuum pump on jobs con- taining 2000 square feet and less, and for over 2000 square feet, an electrically-operated air exhauster. The patents have ex- pired on this system where no pressure-reducing valve is used; therefore no royalty is required. This system is especially desirable when automatic temperature control is used, and is being placed in the large buildings where D MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS low-pressure steam is generated, even when not provided with automatic temperature control, to assist in air removal and in- sure quick heating. In large buildings where an electric generating plant is to be installed an air-line system, or one of the standard vacuum sys- tems with special valve on return end of each radiator is installed. This reduces the back-pressure on the engine and insures quick heating of a large amount of radiating surface. These devices, under the conditions noted above, are a satisfactory and econom- ical adjunct to the mechanical equipment. The office does not regard with favor the various atmospheric or vapor systems of steam heating on the market as applied to plants in small Federal buildings, for the reason that under the usual operating conditions few or none of the advantages claimed for these systems would be secured. As an experiment, the office has installed a number of vapor systems of different makes, and their operation in actual service will be checked against the claims made for them. The argument advanced for most of the vapor systems, i.e., that a certain amount of temperature control is thereby secured, is not given much weight by the office, as prac- tical heating engineers are aware that hand manipulation of valves by individuals to secure temperature control is generally unsatisfactory. In the smaller buildings the standard one-pipe gravity-return steam heating apparatus, such as installed by the office, gives first-class results, as it is simple in construction and operation, and will circulate at atmospheric pressure. When automatic temperature control can not be used, the office endeavors to secure a certain amount of temperature control in connection with its steam heating systems by installing at least two radiators in all apartments with two or more windows, so that in mild weather one radiator may be shut off and remain out of service. This is, of course, a makeshift, but it is the best solution when funds are limited. When money is available for the purpose, the practice of the office will be to use hot air as the heating medium for buildings located on the Pacific coast south of Los Angeles, and on the Florida peninsula; otherwise direct steam will be used. In localities where the lowest recorded temperature is not be- HEATING AND VENTILATION 7 low 10° F., and sudden changes are not common, direct hot water will be used; and in cities where there is a district heating com- pany, using hot water as the heating medium, hot water will be used without reference to climatic conditions. With the above exceptions, steam heating is used, and experi- ence has demonstrated that under all conditions it is generally- more satisfactory in operation than any other system in Federal buildings. If a district heating system is in operation in a city in which a Federal building is to be erected or remodeled, the heating ap- paratus is so designed that it may be operated from the district heating system or from boilers installed in the building. The boilers are always installed, to serve as a check on the cost of outside service and for use in case of a break-down in the district system; but usually it is equally economical and more satisfac- tory to purchase steam or water for heating rather than to gener- ate it in the boilers provided. The practice of the office is to ascertain the amount of radia- tion required by the B.t.u. method, and the results are checked by the experience and judgment of the chief mechanical and electrical engineer. BASIS FOR CALCULATING RADIATING SURFACE Lowest temperature on record in the locality is ascertained from the Weather Bureau reports. If the city has no station the re- sults are taken from the nearest station thereto. In southern cities, where the lowest recorded temperature oc- curs infrequently, and then only for a day or two, the calculation is based on a temperature 10° in excess of the lowest on record for the previous ten years. In northern cities where the temperature goes below 10° and remains around zero for several days, the calculation is based on lowest temperature recorded during the previous ten years. All office rooms, the post-office workroom, court rooms, corri- dors, lobbies, letter carriers' swing room, and all toilet-rooms con- taining bathing facilities are heated to 70° F. General toilet- rooms which do not contain bathing facilities are never heated above 60° F. In southern latitudes where the calculation is O MiliUMAJNIUAJj iiyUlFJVlKJNT Ol' i'JUDJSKAJj ±iUlIjUlJNUfS based on 20° F. or above heat is not provided for any toilet room except that for the carriers. Small toilet-rooms which open from office rooms are not provided with heat where lowest re- corded temperature is not below zero. After determining the temperature upon which the calculation is to be based, the heat losses are ascertained by the B.t.u. method, using the following coefficients for glass and wall, etc., based on Prof. Homer Woodbridge's calculations of heat transmission per degree difference in temperature between inside and outside air : SOLID BRICK WALL Inches One wall exposed Two walls exposed 12 0.265 • 0.232 18 0.210 0.205 21 0.187 0.185 24 0.167 0.150 27 0.152 0.140 30 0.140 0.130 33 0.130 0.120 36 0.120 0.113 40 0.112 0.103 HOLLOW BKICK WALL Inches One wall exposed Two walls exposed 12 0.220 0.170 18 0.175 0.137 21 0.160 0.125 24 0.147 0.115 27 0.135 0.105 30 0.125 0.097 33 0.117 0.090 36 0.110 0.084 40 0.100 0.077 SOLID GBANITE OR MARBLE WALL Inches One wall exposed Two walls exposed 12 0.400 0.335 18 0,340 0.290 21 0.315 0.275 24 0.295 0.260 27 0.280 0.245 30 0.265 0.232 33 0.250 0.220 36 0.235 0.210 40 0.220 0.200 HEATING AND VENTILATION 9 HOLLOW GRANITE OB MAEBLE WALL ■''"'^^' One wall exposed Two walls exposed 12 0.305 0.245 18 0.270 0.215 21 0.255 0.202 24 0.240 0.190 27 0.228 0.180 30 0.218 0.172 33 0.208 0.164 36 0.200 0.157 ^ 0.190 0.149 BRICK WALLS WITH SANDSTONE PACES, PLASTERED ON INSIDE Brickwork Thickness o£ sandstone face Inches i inches 8 inches 12 inches 4 0.31 0.29 0.26 8 0.22 0.20 0.19 12 0.17 0.16 0.15 Concrete or Inches sandstone Limestone 12 0.45 0.49 16 0.39 0.43 20 0.35 0.38 24 0.31 0.35 28 0.28 0.31 32 ■ 0.26 0.28 36 0.24 0.26 40 ■ 0.22 0.24 Above constants are for walls furred and plastered on the in- side with 2-inch terra cotta or wood furring. For walls not furred or plastered add 20 per cent; plastered only add 15 per cent. Outside walls of frame buildings, lath and plaster inside, out- side construction as below: Ordinary overlapping clapboards — ife inch thick 0.44 Same with paper lining 0.31 Same with f-inch sheathing 0.28 Same with |-inch sheathing and paper .23 Inside partitions consisting of 4-inch studs with lath and plas- ter on one side and the other side as below : Nothing 0.60 Lath and plaster .34 iU MEUHAJNiCAlj JDti U IJi'MIiilN T UF ± JKUJiiKAJU JJ U lljJJ J.iM uo For various roof surfaces, as follows: Slate on wood for framing only .80 Slate on tight wood sheathing 0-30 Iron on wood for framing only 1-32 Iron on tight wood sheathing . 17 Patent roof (tar and gravel, paper, etc.) 0.30 Tiling f-inoh to 1-inch thick 0.80 Six-inch hollow tile— 2-inch concrete and tar and gravel covering 0-36 Eight-inch hollow tile— 2-inch concrete and tar and gravel covering . 40 Four-inch concrete with cinder fill . 60 Six-inch concrete with cinder fill 0.54 For various floor surfaces, as follows, assuming temperature of unheated spaces as 40°: Cement or tile ( no wood above) .31 Cement or tile (wood floors above) .08 Dirt (no floor whatever) . 23 Ordinary, single, wood near ground 0.10 Wood, single, no plaster beneath joists 0.10 Wood, double, no plaster beneath joists 0.08 Wood, single, with plaster beneath joists 0.08 Wood, double, with plaster beneath joists 0.06 For various ceilings as follows, assuming temperature of attics as 30° above lowest outside temperature : Cement or tile (no wood above) . 39 Cement or tile (wood floor above) . 10 Lath and plaster (no floor above) .32 Lath and plaster (single floor above) 0.26 Fireproof ceiling (metal lath, no wood above) .49 Fireproof ceiling (metal lath, wood floor above) . 15 For various glass surfaces as follows, assuming exterior doors same as glass, and measuring the openings in brickwork for glass surface : Glass in single windows 1 .00 Glass in double windows 0.50 Glass in single skylight 1 .50 Glass in double skylight . 50 Glass in single monitor 1 .35 HEATING AISTD VENTILATION 11 In rooms over 12 feet high the heat loss is increased by an amount due to the rise in the mean internal temperature, and by the increased rate of air movement over the interior surface of the wall. This increase is practically 2 per cent for each foot of ceiling height over 12 feet. The preceding tables are for southern exposure. Maximum allowance for other exposures should be made as follows : Per cent North, add 25 West, add 15 East, add 10 To this add the following for loss due to leakage : Per cent For office rooms 35 For main lobby, post-ofSce workroom, and court-room 50 Allow for direct steam radiation, standard 3-column radiator, 250 B.t.u., for 2-column 260 B.t.u., and for single-column 270 B.t.u. per square foot per hour; and for water, 160 B.t.u. for 3- column, 170 B.t.u. for 2-column, and 180 B.t.u. for single-col- umn radiation. If a direct radiator is inclosed in a window breast with a proper arrangement for circulating air over it, allow 200 B.t.u. for steam and 120 B.t.u. for water. Three square inches net area in regis- ters or grills to concealed radiators are allowed per square foot of radiating surface. If a direct" radiator is to be placed under a window seat, 220 B.t.u. are allowed for steam, and 140 B.t.u. for hot water radiation. The foregoing rules are not applicable when a building is pro- vided with metal weather strips. In such cases the following formula is used : G = area of glass in square feet. W = area of wall in square feet, less glass. 10 = A constant for all brick walls up to 24 inches thick. 30 = a constant for ceilings. T = temperature of room (70°). Ti = temperature of steam (210°). t = lowest outside temperature. 12 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS The square feet of direct steam radiation required for all aver- W . C\ T-t I W age-size office rooms = ( ^ + Tfj + ; 30/ T, - T' For first-floor lobbies, post-office workrooms, court rooms, and large office rooms add 25 per cent to the result obtained above. If there is a skylight in the room, divide the area of skylight by 5 if steam is the heating medium and add the result to the above formula. No allowance is made for exposure to north, west, or east. As a rule the above will check closely with the results obtained by ascertaining the radiation required by the B.t.u. method pre- viously given and then deducting 10 per cent for use of metal weather strips. The rule used for Federal buildings by the representative of one of the most prominent metal weather-strip manufacturers is as follows: G = area of class in square feet. W = area of wall in square feet, less glass. C = ceiling in square feet. yV = a constant. 4 = a constant. 12 = a constant. 0.44 = a constant idr steam. . 6 = a constant for hot water. Direct radiation =(-j7^+x"'~T9)'^ ^"'^^ ^°^ steam and 0.6 for hot water. This rule is used by the company where the lowest temperature on record is — 10° to 0°. No allowance is made for exposure. Direct-indirect radiation. For direct-indirect heating, a speed of 5 feet per second through the cold-air inlet duct to the radiator is assumed, to ascertain the amount of air which must be raised from exterior temperature to that of the room. This speed has been observed in several anemometer tests of these systems. The heat losses through wall and glass are ascertained by using the exposure factor the same as in direct radiation, but in lieu of using leakage factors the number of B.t.u. required to raise the temperature of air introduced through radiator from lowest re- HEATING AND VENTILATION 13 corded exterior temperature to room temperature is ascertained. Three hundred B.t.u. per square foot for steam radiators and 200 for hot water are allowed. In selecting the boiler the direct- indirect is reduced to direct equivalent by adding 20 per cent to the actual direct-indirect radiation installed. Vent flues with a positive outflow, such as is created by a fan or an aspirating coil, must be provided to assist the inflow of air through the direct-indirect radiators. A speed of 3 feet per sec- ond in vent flues coimected to a properly located roof ventilator without aspirating coil is allowed. This system is sometimes employed with hot-water heating apparatus, but where the lowest temperature on record is below 5° F. its use is not desirable on account of the danger of freezing the radiators. Gravity indirect radiation. Assume that the temperature of entering air under extreme outside conditions will be 120° F. for steam and 100° F. for hot water. The amount of radiation to install is ascertained by the B.t.u. method, taking into account the heat losses through wall, glass, and ceiling, and making allowance for exposure; and in addition allowing 10 per cent for loss of hot air through window cracks if metal weather strips are not used. The B.t.u. ascertained as above, multiplied by 55, and divided by 50 for steam and 30 for hot water, will give the number of cubic feet of air which must be admitted to the apartment per hour to heat it. The number of B.t.u. required to raise the temperature of the air from the lowest outside temperature to 120° F. for steam and 100° F. for water, plus 5° allowance for temperature drop in flue, is ascertained and the resulting number of B.t.u. divided by 350 for steam indirect, natural draft, and by 220 for hot water indi- rect, natural draft. The size of hot-air flues and ducts to be installed is ascertained by assuming the following speeds: Air speed to first floor, 200 feet per minute. Air speed to second floor, 300 feet per minute. Air speed to third floor, 400 feet per minute. The vent flues (which are always installed with this system) and cold-air ducts are made the same size as hot-air flues. 14 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS . In climates where the lowest temperature is — 10°F. and be- low, 12-inch or 15-inch deep extended-pin radiators are used for steam, and in all climates similar radiators are used for water. For climates where temperature is below — 10° F. two 12-inch deep radiators are used for hot water. The allowable speed through cast-iron pin-indirect radiators for natural draft is lunited to approxunately 2 feet per second through one section deep. High speeds necessitate the placing of one sec- tion on top of another with a space of about 4 inches between the sections. Five feet per second through the radiator is the limit with natural draft. The check rule for indirect flues when room is to be heated by- hot air is to make same equal in square inches to the area of glass in square feet plus one-fourth the area of exposed wall in square feet; no flue to be wider than three times its depth. The check rule to determine amount of indirect radiation is to divide the cubic feet of air to be delivered per hour by 200 when air must heat and ventilate the room and by 300 when air is for ventila- tion only. None of the cast-iron extended-pin indirect radiators (except the "Vento") contain the amount of surface given in the manu- facturers* catalogues, and, to be conservative, 20 per cent of the amount claimed should be deducted in making the layout. DIMENSIONS OF PIPING One-Pipe Steam Mains fob Runs up to 200 Feet in Length SIZE OF FLOW PIPE RADIATION DET EETURN WET RETURN" inches inches inches 2 286 U 2i 535 li 3 890 1* 3i 1,360 2 4 1,950 2 5 3,600 2i u 6 5,900 3 H 8 12,700 4 2 10 22,900 5 21 12 37,000 6 3 HEATING ANT) VENTILATION 15 For other lengths of runs see formula given with the 2-pipe schedule. In patent steel steam boilers two tappings are used of such size as to keep velocity of steam in the verticals down to not over 20 feet per second. ONE-PIPE DIRECT RADIATOR TAPPINGS, ARMS AND RISERS SQUARE FEET TAPPING EISEB AND ABM IN BASEMENT AKD RADIATOR ARM inches inches 0- 20 1 1 21- 24 1 u 25- 40 li n 41- 60 li li 61- 80 li 14 81-100 H 2 101-200 2 2 TWO-PIPE HOT-WATER BASEMENT MAINS, GRAVITY CIRCU- LATION, DIRECT RADIATOR TAPPINGS FIRST FLOOR SECOND FLOOR THIRD FLOOR FOURTH FLOOR PIPE SIZE inches 40 50 60 70 f 70 80 90 100 1 110 120 135 150 u 180 195 210 230 li 300 350 400 500 2 At ends of mains increase tapping one size. No main to be less than IJ inches. To get size of mains and risers serving more than one radiator, add area of tappings together and use the following: EQUALIZING TABLE Inches > Inches 1 equals 2 3 equals 175 I equals 5 31 equals 260 1 equals 10 4 equals 380 IJ equals 20 5 equals 650 li equals 30 6 equals 1,050 2 equals 60 7 equals 1,600 2i equals 110 8 equals 2,250 16 MECHANICAL EQUIPMENT OF FEDEEAL BUILDINGS To get size pipe to serve a f-inch pipe and a 1-inch pipe : J inch equals 5 1 inch equals 10 15 equals IJ inch Expansion tanks are made 1 gallon to 30 square feet radiation up to 1000 square feet; 1 gallon to 40 square feet 1000 to 2000 square feet; 1 gallon to 50 square feet 2000 to 5000 square feet and 1 gallon to 60 square feet for jobs above 5000 square feet in radiators. SCHEDULE OF SIZES TO BE USED ON DOWN FEED SINGLE DKOP RISERS, RADIATORS, TAPPING, ETC. In the case of down flow single risers, tap radiators for all floors above the first, top and bottom on the same end, first floor radia- tors to have top floor connection on one end and bottom return on opposite end. Radiators 50 square feet and smaller to have f inch connection. Radiators 51 to 80 square feet to have 1 inch connection. Radiators 81 to 120 square feet to have IJ inch connection. Radiators 121 to 195 square feet to have IJ inch connection. MaiUng vestibule radiators to be tapped one pipe size larger than the above. Drop risers to be made one size from flow to return main with standard cast iron tee fittings used at the branch connections. The return branch from first floor and basement radiators to be connected to return main and not to risers, except in special cases where such branch connections would be of excessive length. Consult assistant engineer if such connections are over five feet. Make branches in attic and drop risers in accordance with the following schedule: 50 square feet | inch. 80 square feet 1 inch. 120 square feet IJ inch. 195 square feet 1| inch. 350 square feet 2 inch. HEATING AND VENTILATION 17 The attic distributing mains to be proportioned by adding to- gether the values given each size pipe in the equalization table, beginning at the far end of the main and adding together the risers values as you proceed. If the length of run to the last riser on the line exceeds 10 feet said run to riser must be increased one size above that of the riser up to IJ inches in size. Riser 1§ inches diameter will not require such increase. Retiirn mains in the basement are to be reversed so that the first riser on the attic main becomes the last on basement main. Return mains are to be proportioned the same as above described for attic mains, care being taken to disregard the separate return branches from first floor and basement radiators, which are really provided for in the sizes of the riser bra,nch. Radiators to be valved on both flow and return connection. The size of main riser may be taken from the following table, and may be greatly reduced in size if a proper chamber, or the expansion tank, is placed at the top of the main riser. Square feet Square feet direct direct Inches radiation Inches radiation li 300 3i 2,600 2 600 4 3,500 21 1,200 5 6,000 3 2,000 6..., 10,000 Expansion tanks are made 25 per cent larger than for two-pipe basement mains. One-pipe circuit hot water. Use the same tappings and risers as given for 2-pipe hot water. To arrive at size of 1-pipe circuit hot-water mains, the follow- ing sizes are used: Pipe 200-foot 300-foot Pipe 200-foot 300-foot sizes runs runs sizes runs 2 200 180 5 2,300 1,800 2? 400 300 6 3,600 3,000 3 600 500 7 5,200 4,000 3i 900 700 8 6,800 6,000 4 1,200 1,000 A 1-inch or IJ-inch starting pipe is used with this system. The length of mains is measured back to' boiler. 18 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS Tees on main are kept 2 feet apart. Risers are taken out of main on 45° and first floor connections out of top of main. All returns are taken into side of main. No special fittings are used except twin ells on mains where they branch. Two-pipe gravity steam. Radiators assumed to transmit 250 heat units per square foot per hour. The following table is for pipes 200 feet in length. For pipes of greater length, multiply results in table by , in which "e" equals length in feet. The e values of this expression for different lengths of pipe are: For 300 feet multiply by 0.66f ; for 400 feet, by 0.50; for 500 feet, by 0.40; for 600 feet, by 0.33; for 800 feet, by 0.25; for 1000 feet, by 0.20. TABLE FOR MAINS, RISERS, AND TAPPINGS FOR TWO-PIPE DRY RETURN STEAM HEATING SYSTEM, TWO POUNDS AND FIVE POUNDS STEAM PRESSURE TWO POUNDS FIVE POUNDS DIAMETER DIAMETER OF PRESSURE, RADIATING SUE- PEESSURB, BADIATINQ SUR- OF SUPPLY RETURN IN" TOTAL HEAT FACE IN TOTAL HEAT FACE IN IN INCHES INCHES TRANSMITTED , B.T.U.PERHOUR SQUARE FEET TRANSMITTED, B.T.U.PERHOUR SQUARE FEET 3 4 3 4 5,000 20 10,000 40 1 3 4 9,000 36 15,000 60 u 1 18,000 72 30,000 120 li li 30,000 120 50,000 200 2 li 70,000 280 120,000 480 2i 2 132,000 529 220,000 880 3 2i 225,000 900 375,000 1,600 3i 2i 330,000 1,320 550,000 2,200 4 3 480,000 1,920 800,000 3,200 4i 3 690,000 2,760 1,150,000 4,600 5 3i 930,000 3,720 1,550,000 6,200 6 3i 1,500,000 6,000 2,500,000 10,000 7 4 2,250,000 9,000 3,750,000 15,000 8 4 3,200,000 12,800 5,400,000 21,600 9 ^ 4,450,000 17,800 7,500,000 30,000 10 5 5,800,000 23,200 9,750,000 39,000 12 6 9,250,000 31,000 15,500,000 62,000 14 7 13,500,000 54,000 23,000,000 92,000 16 8 19,000,000 76,000 32,500,000 130,000 Cast-iron boilers. As the experience of the office has demon- strated that cast-iron sectional boilers are usually unsatisfactory HEATING AND VENTILATION ' 19 in maintaining a steady water line and frequently crack and break under service conditions, they are used only where struc- tural reasons forbid the installation of steel boilers, and in such cases the proper size is ascertained by adding to the actual direct radiation installed 25 per cent for mains if anthracite coal is used, and 35 per cent if soft coal is used; and installing two boilers, each rated to carry two-thirds of the required service. Either boiler will then, if forced, carry the radiation for a few days in case of a breakdown in the other boiler. To obtain the size of the stack when cast-iron sectional boilers are used, the formula is: . . . , area of grate in square feet X 0.75 Area m square feet = V height of stack in feet The tappings for steam connections are made not less than two in number, and their area must be such that the velocity of steam will not be over 12 feet per second in the verticals. Returns are connected into both sides of each cast-iron boiler. A 2-inch equalizing pipe from the bottom of the main header into the main return header is always installed on patent steel or cast iron boilers. Fire box boilers. After an extended experience the office has adopted steel fire box boilers as a standard for all jobs of less than 3600 square feet steam radiation or 6000 square feet water radia- tion. Above this two such boilers are used or horizontal return tubular brickset boilers are used. The fire box boilers are brickset with return smoke passage over top. One reason for the adoption of the fire box boilers was the ease and cheapness with which they are equipped with an effective down draft furnace and the low water line obtainable in such cases thus avoiding a pit in almost every case. These boilers have proven to be very efficient as to fuel and are no more expensive to install than the portable steel boilers and, ratings considered, but little more expensive than cast iron. Equipped with a down draft furnace they are cheaper than the portable steel boilers or horizontal return tubular either. These fire box boilers are drawn and specified on miscellaneous drawings No. 303A and 304A, Supervising Architect's Ofiice. 20 ■ MKCHANICAL EQUIPMENT OF FEDERAL BUILDINGS Portable steel boilers. In small buildings in which a down draft furnace is not used, consideration is given to a round vertical steel boiler. Except in certain special cases, the maximiun size used of this type of boiler has a 28-inch diameter grate. In order to comply with local smoke ordinances, now existing in nearly every city of any size, down-draft furnaces are installed where soft coal must be used, except where the size of horizontal boiler required is such as to serve less than 1600 square feet of direct steam radiation. In such cases the Federal building is approximately the same size as a large residence, and, like a resi- dence, local smoke ordinances are not applicable thereto. The down-draft type of furnace is peculiarly suited to low- pressure heating boilers, as it has no moving parts, and a low grade of labor can be taught to fire it properly. Where small size anthracite coal is the cheapest fuel, the maxi- mum openings in the grate bars are specified not to exceed j^ inch. The size of boiler when small anthracite coal is to be used is ob- tained by adding ^5 per cent to the actual direct radiation in- stalled. When the cost of 20,000 cubic feet of natural gas is cheaper than one ton of coal, the boiler is equipped with burners, pilot light, and governor. The rating of boiler for use with gas is as- certained by adding 25 per cent to the actual direct radiation installed. When bituminous coal is the cheapest fuel, the boiler rating is obtained by adding 25 per cent to the actual amount of direct radiation installed. When three times the cost of oil per barrel plus the cost of seven kilowatt-hours of electric current per day (generally 70 cents) is less than the cost of one ton of coal, oil is used and the boiler is equipped with oil burners, pumps, tanks, etc. The office is reluctant to install oil burning apparatus, as it involves the use of motor and pump, which the class of labor employed in the small Federal buildings is not, as a rule, competent to handle. Unless the annual saving of oil over coal will amount to at least $200 per year, coal is used. The size of boiler for use with oil is ascertained by adding 25 per cent to the actual direct radiation installed. When the size of the steel boiler required exceeds 3300 square HEATING AND VENTILATION 21 feet, consideration is given to the advisability of installing (1) two small, steel boilers, (2) or a horizontal return-tubular brick-set boiler. All the ratings given above are direct steam ratings, but the remarks apply to hot water boilers of equivalent capacities. If a horizontal, return-tubular, brick-set boiler is to be installed, it is proportioned as follows : R = total direct radiation in building, in square feet. RM.S. = heating surface in boiler, in square feet. G = area of grate in square feet. B.H.S. = — for small and — for large steam boilers = — for o lU 15 water. ^ _ B.H.S. . B.H.S. , . tr gQ— to — gg— Plam grate. Lower grate of a down draft furnace is made same size as upper grate, which is never specified, it being preferred to allow the manufacturer to fix the size of the down draft furnace for the work to be performed. A down draft furnace increases the steaming capacity of a boiler 15 per cent over ratings given above. H = height of stack in feet. A = area of grate in square feet. S = area of stack in square feet. S = ~y=ior anthracite coal, lump coal, oil, and gas. S = yjj X 1.25 for bituminous and small anthracite. For anthracite, pea, or rice coal, the tube area must be not less than one-eighth grate area and be always larger than stack area. For boilers with down-draft furnace attached, the tube area must be not less than one-sixth area of lower grate, and be always larger than stack area. Maximum length of tube must generally not exceed 48 diame- ters. 22 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS Maximum length of boilers 54-inch diameter and under must generally not exceed 3 diameters; over 54-inch 2| diameters. Tubes an odd number of feet long are not used. Coal consumption for low-pressure heating apparatuses in tons per heating season may be found for Government buildings by multiplying by 5 the area of grate or grates in square feet, which will give the number of tons of coal burned per heating season of 240 days. A safe rule is that for each cubic foot of contents of building one pound of coal will be required for heating season of 240 days. The district steam heating companies usually estimate thajfc each square foot of direct steam radiation will require 500 pounds of steam per season. To find size of coal storage room for a government building, ascertain maximum consumption of coal for entire heating season and allow 8 square feet of floor space per ton. To ascertain boiler horse-power for direct heating of a building in New York City or a similar climate, allow 100 boiler horse- power for each 1,000,000 cubic feet of coijtents for zero weather, and in average winter weather two-thirds of this will be the horse- power required. Between 40 and 50 per cent of the maximum will be the boiler horse-power required for the full heating season of 5700 hours. The boiler horse-power in Federal buildings with a heating and ventilating apparatus will average one boiler horse-power for each 7000 cubic feet of contents. FAN SYSTEMS As a general rule the fan is used to supply air for ventilation alone, and the trunk main system of distribution of air is used, but in exceptional cases where the fan is used for heating as well as for ventilating the plenum chamber system is used for the distri- bution of the hot air. In other cases where requirements as to ventilation are not so exacting, but where it is desired to use fans for heating, sometimes on account of the construction of the building and again for rea- sons of control in climates of rapidly varying temperatures, the trunk main system is used; and if funds are available the air supply to the various rooms is automatically controlled by ther- mostats located in said rooms. HEATING AND VENTILATION 23 Amount of air to be circulated. When air is used for ventila- tion alone, and the number of occupants of any given room is not known, three to five changes of air per hour are allowed in post-office work-rooms, court rooms, and carriers' swing rooms (depending upon the size, location, and opportunities for natural ventilation), and four air changes per hour in office rooms. When the number of occupants ife known, 2000 cubic feet of air per hour is allowed for each occupant. When air is used for heating as well as for ventilation, the B.t.u. lost from the building are estimated exactly as heretofore given. The amount of air given above for ventilation is taken as the amount of air to be put into the room, and the tempera- ture at which the air must enter the room to heat it is estimated. If this temperature is above 125° F, more air is to be circulated, 125° F. being taken as the maximum temperature of air entering a room, except in special cases. Kind and size of fans. The regular style of steel plate or multi- blade fans is used exclusively for plenum work. Disc fans are used only for ventilation without a heater, and then the total length of inlet and outlet pipe must be equivalent to not more than 100 feet of straight pipe of the diameter of the fan; and they are never required to work against any strong natural aspirating tendencies. In such cases the motor is usually provided with a reversing switch, or rocker arm, so that the fan may be easily reversed and made to supply fresh air or to exhaust air, as desired. Curved blade fans are generally specified, and required to be of a type that when running "backwards" will handle not less than 75 per cent of the amount of air they will handle when ruiming "for- ward." Cone fans are used very seldom, and only where it is desired to reduce the power to a minimum at the expense of large ducts and much floor space. On exhaust ventilation, where owing to length of ducts or other reasons a disc fan is not wanted, the steel plate or multiblade fan is generally used, although a cone fan if it can discharge freely, is admirably adapted for this work. Capacity and power. The capacity of any fan may be expressed by the formula: 24 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS C.F.M. = ADW, in which C.F.M. = cubic feet of air per minute. D = diameter of wheel in feet. N = number of revolutions per minute. A = a constant depending upon the kind of fan and the conditions under which it operates. The horse-power may be expressed by the formula: B.H.P. = ^-^, in which D and N are as given above and B.H.P. = horse-power applied to fan shaft; C = a constant depending on the kind of fan and the conditions under which it operates; S = a, constant depending on the temperature of air handled by fan, which is =v. s -' 4^0 The values for A and C will be given for each of the following conditions for the various fans : Case I. For a fan used for plenum ventilation only, and with- out an air washer. Case II. Same as Case I, except that an air washer is used. Case III. For a fan used for both heating and ventilation, and without an air washer. Case IV. Same as Case III, except that an air washer is used. Case V. For a fan used for exhaust or forced ventilation, when no resistance is encountered but the duct system. Case VI. For a fan on free suction and discharge. Steel plate fans. Proportions are assumed to be as follows : Width periphery = 40 per cent diameter of wheel. Width housing = 57 per cent diameter of wheel. Diameter inlet in case = 62| per cent diameter of wheel. Eight blades, set radially, not curved. Multiblade fans. Width periphery = one-half diameter of wheel. Width casing = two-thirds diameter of wheel. Diameter inlet in case = diameter of wheel (practically). HEATING AND VENTILATION 25 Wheels above 9-inch diameter have 64 blades, curved slightly forward in the direction of rotation. Cone fans. Width periphery = 25 per cent diameter of wheel. Diameter inlet = 75 per cent diameter of wheel. In the following table are given the values of A and C to be sub- stituted in the general formulae given above for capacity and power of fans : CASE NUMBER I II III IV V VI I II III IV V VI I II III IV V VI V VI VI KIND OF FAN Steel plate Steel plate Steel plate Steel plate Steel plate Steel plate Multiblade.... Multiblade.... Multiblade.... Multiblade.... Multiblade.... Multiblade.... Cone type. . . . Cone type. . . . Cone type .... Cone type .... Cone type. . . . Cone type. . . . Propeller type Propeller type Disc A 0.50 0.42 0.44 0.40 0.56 0.62 1.45 1.34 1.38 1.10 1.70 1.95 0.55 0.48 0.48 0.45 0.60 0.73 0.50 0.70 0.70 12,000,000,000 12,500,000,000 12,500,000,000 13,000,000,000 11,500,000,000 11,000,000,000 1,700,000,000 1,800,000,000 1,750,000,000 2,250,000,000 1,500,000,000 1,250,000,000 13,000,000,000 14,000,000,000 14,000,000,000 12,000,000,000 11,500,000,000 11,000,000,000 33,000,000,000 37,000,000,000 42,500,000,000 VELOCI- TIES The group "Propeller type" may be taken to cover the David- son, American Sirocco, or Sturtevant propeller fans. The group "Disc" itncludes all straight-blade disc fans having twelve or more wide blades. It does not, of course, cover the ordinary desk fan. The column headed "Ratio of velocities" in the table refers to the peripheral velocity of fan wheel divided by the mean velocity of air in the heating coils. The ratios given are maintained as nearly as practicable. 26 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS Speed of fans. Steel plate fans are run at a peripheral speed of 3000 to 4000 feet per minute, except when an air washer is used, when the speed must be about 4500 feet per minute. Multiblade fans are run at a peripheral speed of 2200 to 2500 feet per minute, and about 3000 feet when an air washer is used. Cone fans are run at a peripheral speed of 3600 to 4600 feet per minute, and at least 5000 feet when an air washer is used. Propeller type fans to operate at a peripheral speed of 2500 to 6500 per minute and disc fans from 3000 to 8000 feet per minute. The formulae for power are based on 8-blade wheels about 6 feet diameter; sirocco wheels 4 feet diameter; cone wheels 6 feet diameter; and disc and propeller wheels 4 feet diameter. The horse-power should be increased about 5 per cent for each foot in diameter less than these diameters, to cover decrease in efficiency. No decrease in power for larger wheels. Heaters. Heaters used with fans are usually of cast-iron base, miter type, with wrought-iron pipe surface, or the all cast-iron heaters, such as the "Vento." The data published by the American Radiator Co. on tem- perature rise and condensation in Vento Heaters has been found to be thoroughly reliable. The heaters are designed on this basis and wrought iron heaters when used are required to have the same heating surface and same free area as would be required for "Vento." These data are given hereinafter. Friction. The friction in pipe coils on 2|-inch centers is as follows : AIR VELOC- ITY FEET PER MINUTE 4 ROWS 8 ROWS 12 H0W3 16 EOWS 20 ROWS 24 BOWS 600 0.04 0.06 0.09 0.12 0.14 0.15 800 0,06 0.10 0.15 0.19 0.23 0.26 1,000 0.09 0.15 0.21 0.30 0.37 0.41 1,200 0.12 0.21 0.31 0.43 0.50 0.58 1,400 0.17 0.30 0.45 0.60 0.75 0.90 Friction is inches of water, and for any other velocities may be taken as varying as the square of the velocity. The free air space with pipes on 2f -inch center = total number lineal feet of pipe in the heater, divided by the number of pipes deep, divided by 8.4. HEATING AND VENTILATION 27 All the above is for 1-inch diameter pipes. One and a quarter inch pipes at same air velocity will give practically the same B.t.u. per square foot per hour. Sections should be tapped as follows: POtTNDS STEAM PER HOTJR PER SECTION STEAM TAP DRIP TAP BLEEDER TAP iriches inches inches 80 2 li 1 4 160 2i n 3 4 320 3 2 U 480 31 2i li 960 4 2i n Vento heaters. The free area in square feet = the total number of square feet of heating surface divided by the number of sections and this quotient divided by 17.6 for standard sections and by 12.1 for the narrow type sections. Long spacing (5f-inch cen- ters) increases the free area 18 per cent over the standard spacing, and short spacing (4f-inch centers) decreases it to 85 per cent of the standard. The following table gives the friction in inches of water for various depths of coils and various velocities. BEGULAR SECTION NAKHOW SECTION PER MINUTE One Section Add for Each Ad- ditional Section Two Sections Add for Each Ad- ditional Section 600 700 800 900 1,000 1,100 1,200 1,300 1,400 1,500 0.022 0.030 0.040 0.051 0.063 0.076 0.090 0.105 0.122 0.140 0.018 0.025 0.032 0.040 0.050 0.060 0.072 0.085 0.102 0.112 0.028 0.037 0.048 0.061 0-.075 0.090 0.107 0.126 0.147 0.170 0.015 0.020 0.027 0.034 0.042 0.050 0.060 0.070 0.082 0.093 Sections are on standard spacing (5-inch centers) . Velocity is volume of air measured at 70° F. Standard "Vento" tappings are 2J inches, but the feed sections can be tapped 3 inches or 3§ inches. Use tapping schedule given for wrought-iron coils. Bush the returns to one-half diameter of 28 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS steam tap plus one pipe size. Not over 480 pounds steam per hour is condensed in one group. One-half or three-quarter inch air valves are installed at each end of each group about 8 inches from bottom of sections. Use the "standard" spacing (5-inch center to center) unless otherwise instructed. The "narrow" spacing, which is 4f-inch centers, and the "wide" spacing, which is 5f-inch centers, are not to be used except under special conditions. The free area for standard spacing is 44 per cent of the area of face; the narrow 37 per cent; and the wide 52 per cent. The 40-inoh high 9|-mch deep section contains 10.75 square feet. The 50-inch high 9|-inch deep section contains 13.50 square feet. The 60-inch high 9|-inoh deep section contains 16.00 square feet. The 40-inch high 6f-inch deep section contains 7.50 square feet. The 50-inch high 6J-inch deep section contains 9.50 square feet. The 60-inch high 6i-inch deep section contains 11.00 square feet. For example, if a 60-inch high heater is desired with 22 square feet free area: 22 4- 44 per cent = 50 square feet gross area -f- 5 feet (high) = 10 feet = 120 inches wide -f- 5 = 24 sections wide. After size of heater is found by the free area method, check same by the B.t.u. method by estimating the total B.t.u. required and dividing same by the condensation; the B.t.u. per square foot per hour being taken from the tables and corrected for difference in temperature (same as outlined for correction of temperature rise). Hot water. With water at a mean temperature of 180° F. the rise in temperature with wrought-iron coils and the B.t.u. trans- mitted are about 75 per cent of what they would be with steam at 227° when the velocity of air leaving the coil, number of pipes deep, spacing, etc., are the same. To get the same rise in temperature with incoming air same temperature, same sections, same depth, etc., the velocity of air will be 40 per cent of what would be estimated for steam at 227°. With hot water, forced circulation must be used in fan blast coils. If high-pressure steam is used, the rise in temperature and con- densation are estimated on the principle that these quantities are in proportion to the difference in temperatures of steam and en- tering air. HEATING AND VENTILATION 29 FRICTION OF AIR THROUGH VENTO HEATERS Friction Loss— In Inches op Water — Due to Air Passing through Vento Stacks. (Mbastjbed at 70°) Regular Section — 4i, 5 and B^-Inches Spacing as > 6 m m 1 STACK 2 STACKS 3 .STACKS 4 STACKS 5 STACKS 6 STACKS 7 STACKS 8 STACKS a 5 51 0.022 0.021 0.019 0.043 0.040 0.034 0.063 0.058 0.049 0.084 0.076 0.064 0.105 0.094 0.079 0.126 0.112 0.094 0.147 0.130 0.109 600 0.149 0.124 700 6 61 0.031 0.028 0.025 0.059 0.054 0.046 0.087 0.079 0.066 0.116 0.105 0.087 0.143 0.130 0.108 0.172 0.165 0.128 0.200 0^80 0.149 0.205 0.170 4f 5 61 0.040 0.037 0.033 0.077 0.070 0.060 0.114 0.103 0.087 0,150 0.135 0.114 0.187 0.167 0.140 0.224 0.200 0.167 0.269 0.232 0.194 800 0.265 0.221 5 51 0.051 0.047 0.042 0.097 0.088 0.076 0.144 0.129 0.110 0.190 0.170 0.144 0.237 0.211 0.178 0.283 0.252 0.212 0.329 0.293 0.246 900 0.336 0.280 41 5 51 0.063 0.069 0.052 0.120 0.109 0.094 0.178 0.160 0.136 0.235 0.211 0.178 0.293 0.262 0.220 0.350 0.313 0.262 0.407 0.364 0.304 1000 0.415 0.346 4i 5 5f 0.076 0.071 0.062 0.146 0.132 0.113 0.214 0.193 0.164 0.284 0.255 0.215 0.363 0.316 0.265 0.422 0.377 0.316 0.491 0.438 0.367 1100 0.601 0.418 4| 5 61 o;d9o 0.084 0.074 0.172 0.167 0.134 0.255 0.230 0.195 0.337 0.303 0.255 0.420 0.376 0.316 0.502 0.449 0.376 0.584 0.522 0.437 ■^- 1200 0.596 0.497 6 51 0.105 0.099 0.087 0.202 0.186 0.158 0.299 0.271 0.229 0.396 0.356 0.300 0.493 0.442 0.371 0.590 0.628 0.442 0.687 0.614 0.513 1300 0.701 0.584 1400 41 6 51 0.122 0.115 0.101 0.234 0.214 0.183 0:347 0.314 0.266 0.459 0.414 0.348 0.672 0.513 0.430 0.684 0.612 0.612 0.796 0.712 0.595 0.813 0.677 4f 5 51 0.140 0.132 0.116 0.269 0.246 0.210 0.398 0.360 0.305 0.527 0.474 0.399 0.656 0.588 0.493 0.785 0.702 0.587 0.914 0.816 0.682 1500 0.932 0.776 4! 5 5i 0.160 0.150 0.132 0.306 0.280 0.239 0.453 0.410 0.347 0.600 0.640 0.454 0.746 0.1670 0.561 0.893 0.800 0.668 1.040 0.930 0.776 1600 1.060 0.883 41 5 51 0.180 0.169 0.149 0.346 0.316 0.270 0.512 0.463 0.391 0.677 0.609 0.512 0.843 0.766 0.634 1.009 0.903 0.766 1.174 1.049 0.876 1700 1.197 0.997 41 5 61 0.202 0.190 0.167 0.387 0.354 0.303 0.573 0.518 0.439 0.759 0.683 0.575 0.944 0.848 0.710 1.130 1.012 0.846 1.316 1.177 0.982 1800 1:342 1.118 30 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS FRICTION OF AIR THROUGH VENTO HEATERS Friction Loss — In Inches op Water — Dub to Air Passing through Vento Stacks. (Measured at 70°) Narrow Section — 41, 5 and 5| Inches Spacing fa . H H 3° 1 STACK 2 STACKS 3 STACKS 4 STACKS 5 STACKS 6 STACKS 7 STACKS 8 STACKS 9 STACKS 10 STACKS 4| 5 5i 0.018 0.017 0.015 0.032 0.030 0.026 0.047 0.042 0.036 0.061 0.055 0.047 0.076 0.067 0.058 0.090 0.080 0.069 0.104 0.093 0.079 0.119 0.105 0.090 0.164 0.143 0.124 600 0.118 0.101 0.131 O.IU 4J 5 5i 0.025 0.023 0.021 0.045 0.040 0.036 0.065 0.057 0.050 0.085 0.074 0.065 0.105 0.092 0.080 124 0.109 0.095 0.144 0.126 0.109 700 0.160 0.139 0,178 0.153 41 5 51 0.032 0.030 0.027 0.058 0.052 0.046 0.083 0.074 0.065 0.109 0.097 0.084 0.135 0.120 0.103 0.160 0.142 0.123 0.186 0.165 0.142 0.212 0.187 0.161 800 0.210 0.180 0.232 0.199 4{ 5 55 0.041 0.038 0.034 0.073 0.066 0.058 0.106 0.095 0.082 0.138 0.123 0.107 0.171 0.151 0.131 0.203 0.180 0.155 0.236 0.208 0.179 0.268 0.237 0.213 900 0.265 0.228 0.293 0.252 4| 5 61 0.050 0.047 0.042 0.090 0.082 0.072 0.131 0.117 0.102 0.171 0.152 0.132 0.211 0.187 0.162 0.251 0.223 0.192 0.292 0.258 0.221 0.332 0.293 0.251 1000 0.328 0.281 0.364 0.311 4J 5 5i 0.061 0.057 0.051 0.109 0.099 0.087 0.158 0.141 0.123 0.207 0.184 0.159 0.255 0.226 0.195 0.304 0.269 0.232 0.352 0.311 0.258 0.401 0.354 0.304 1100 0.396 0.400 0.438 0.376 4j 5 5t 0.072 0.067 0.061 0.130 0.118 0.104 0.188 0.169 0.147 0.a46 0.219 0.190 0.303 0.269 .0.233 0.361 0.320 0.276 0.419 0.371 0.318 0.477 0.422 0.361 1200 0.472 0.404 0.522 0.447 4f 5 51 0.085 0.079 0.072 0.153 0.139 0.122 0.221 0.198 0.173 0.289 0.2S7 0.223 0.356 0.317 0.273 0.424 0.376 0.324 0.492 0.436 0.374 0.560 0.495 0.424 1800 0.554 0.474 0.6U 0.525 41- 5 5i 0.098 0.092 0.083 0.177 0.161 0.141 0.256 0.230 0.200 0.335 0.299 0.258 0.413 0.368 0.317 0.492 0.437 0.375 0.571 0.506 0.4.33 0.655 0.579 0.497 0.650 0.574 0.492 1400 0.643 0.550 0.712 0.609 41 S 5i 0.112 0.105 0.095 0.202 0.184 0.162 0.293 0.263 0.229 0.383 0.342 0.296 0.474 0.421 0.363 0.564 0.500 0.430 0.745 0.658 0.564 IbOO 0.737 0.631 0.816 0.698 41 5 51 0.128 0.120 0.108 0.231 0.210 0.184 0.334 0.300 0.261 0.437 0.390 0.337 0.539 0.480 0.413 0.642 0.570 0.490 0.745 0.660 0.566 0.848 0.750 0.642 IbOO 0.840 0.718 0.930 0.795 4i 5 5f 0.145 0.136 0.122 0.261 0.237 0.208 0.377 0.339 0.294 0.493 0.440 0.381 0.610 0.542 0.467 0.726 0.644 0.553 0.842 0.745 0.639 0.958 0.847 0.725 IV 00 0.948 0.812 1.049 0.898 41 5 5i 0.162 0.152 0.137 0.295 0.266 0.234 0.422 0.380 0.330 0.552 0.494 0.427 0.683 0.608 0.523 0.813 0.722 0.620 0.943 0.835 0.716 1.073 0.949 0.813 1800 1.063 0.909 1.177 1.006 NARROW SECTION— RATINGS AND FREE AREAS 40-Inch Section — 7.S Square Feet . Height ^l-jt inch . Width 61 inches g ss 51 INCH CENTERS 5 INCH CENTERS 4S INCH CENTERS b. DO a EH OF SECTIONS OF SECTIONS OF SECTIONS s NUMBER OF SEO- 52% of Face Standard 44% of Face 37% of Face Hg P g] ra H 3 S Net Air Space in Square feet tWidth of Stack in Inches Net Air Space in Square Feet tWidth of Stack in Inches Net Air Spacein Square Feet tWidth Of Stack in Inches P e < 7 52.5 158 6.12 38 4.34 36 3.67 32 8 60.0 180 5.85 43 4.96 40 4.20 37 9 67.5 203 6.57 48 6.68 46 4.72 42 10 75.0 226 7.29 54 6.20 50 5.25 46 11 82.5 248 8.02 59 6.82 56 5.77 51 ■ f„ 12 90.0 270 8.74 65 7.44 60 6.30 55 r% 13 97.6 293 9.47 70 8.06 65 6.82 60 ■§ M 14 105.0 316 10.19 75 8.68 70 7.36 65 •" ft 15 112.6 338 10.91 81 9.30 75 7.87 69 ti 16 120.0 360 11.64 86 9.92 80 8.40 74 n« 17 127.5 383 12.36 91 10.54 85 8.92 79 A ^ 18 136.0 405 13.09 97 11.16 90 9.46 83 Po 19 142.5 428 13.82 102 11.78 95 9.97 88 °°-S 20 150.0 450 14.54 108 12.40 100 10.50 92 OS 21 157.5 473 15.26 113 13.02 105 11.02 97 22 165.0 496 16.98 118 13.64 110 11.55 102 23 172.6 518 16.71 124 14.26 115 12.07 106 24 180.0 540 17.43 129 14.88 120 12.60 111 50-Inch Section — 9.5 Square Feet. Height 50^ inches. Width 6J inches 5J INCH CBNTEHS 5 INCH CENTERS 4f INCH CENTERS 7 66.5 200 6.36 38 6.37 35 4.56 32 8 76.0 228 7.26 43 6.14 40 5.20 37 9 85.6 257 8.16 48 6.91 45 6.85 42 10 96.0 286 9.05 54 7.68 SO 6.60 46 11 104.5 314 9.95 69 8.46 56 7.15 51 s 12 114.0 342 10.85 65 9.22 60 7.80 65 ■3'e 13 123.5 371 11.75 70 9.99 65 8.45 60 3 a 14 133.0 399 12.65 76 10.76 70 9.10 65 ■" ft 16 142.6 428 13.65 81 11.53 75 9.76 69 i-S 16 162.0 466 14.45 86 12.30 80 10.40 74 «£ 17 161.5 486 15.35 91 13.07 85 11.05 79 ^" 18 171.0 613 16.26 97 13.84 90 11.70 83 °s 19 180.5 642 17.16 102 14.59 96 12.36 88 "i 20 190.0 670 18.06 108 15.36 100 13.00 92 Oi 21 199.5 699 18.95 113 16.13 106 13.66 97 22 209.0 627 19.85 •118 16.90 110 14.30 102 23 218.5 656 20.75 124 17.67 115 14.96 106 24 228.0 684 21.65 129 18.44 120 16.60 111 31 32 MECHANICAL EQUIPMENT OP FEDERAL BUILDINGS NARROW SECTION— Continued 60-Inch Sech on — 11 Square Feet. Height 60^ inches . Width 6i inches CO g £^ a a H J Oi 5| INCH CENTERS OF SECTIONS 5 INCH OBNTBBS OP SECTIONS 4| INCH CENTEHS OF SECTIONS S NUMBER OF SEC- 52% of Face Standard 44% of Face 37% of Face o TIONS IN STACK Net Air Space in Square Feet tWidth of Stack in Inches Net Air Spacein Square Feet tWidth of Stack in Inches Net Air Spacein Square Feet tWidth of Stack in Inches < D 7 77,0 231 7.62 38 6.45 35 5.47 32 8 88.0 264 8.70 43 7.37 40 6.25 37 9 99.0 297 9.77 48 8.29 45 7.03 42 10 110.0 330 10.85 54 9.21 50 7.81 46 11 121.0 363 11.93 59 10.13 55 8.59 51 1. 12 132.0 396 13.00 65 11.05 60 9.37 55 II 13 143.0 429 14.08 70 11.97 65 10.15 60 14 154.0 462 15.15 75 12.89 70 10.93 65 s'l 15 165.0 495 16.23 81 13.81 75 11.71 69 CO m • 16 176.0 528 17.31 86 14.73 80 12.49 74 |£ 17 187.0 561 18.39 91 15.65 85 13.27 79 S " 18 198.0 594 19.46 97 16.57 90 14.05 83 19 209.0 627 20.54 102 17.50 95 14.83 88 CO "-^ 20 220.0 660 21.62 108 18.42 100 15.61 92 Oi 21 231.0 693 22.70 113 19.34 105 16.39 97 22 242.0 726 23.78 118 20.26 110 17.17 102 23 253.0 759 24.85 124 21.18 115 17.95 106 24 264.0 792 25.93 129 22.10 120 18.73 111 fNoTE. — Add to the width of stack 2J inches for staggering of stacks. *NoTE. — The actual length of one-inch pipe per square foot of outside surface is 2.9 lineal feet but is nominally figured at 3 lineal feet, as shown in the third column of above table. KJiJGuJLAK bJiiUiiuivi— kaiiInGS AND FREE AREAS 30-Inch Section {Steam only) — 8 Square Feet. 9s inches Height 30 inches. Width i CO « a D a > J M < g H [l] hJ 0H ^ INCH CENTERS OF SECTIONS 5 INCH CENTERS OP SECTIONS 4| INCH CENTEH3 OF SECTIONS 4 INCH OENTEBS OF SECTIONS 52% of lace Standard 44% of Face 37% of Face 24% of Face Net Air Space in Square Feet tWidth ot Stack in Inches Net Air Space in Square Feet tWidth of Stack in Inches Net Air Spacein Square Feet tWidth of Stack in Inches Net Air Spacein Square Feet Width of Stack in Inches 7 66 168 3.81 38 3.22 36 2.73 32 1.79 28 8 64 192 4.35 43 3.68 40 3.12 37 2.04 32 9 72 216 4.88 48 4.14 46 3.62 42 2.30 36 10 80 240 5.42 54 4.60 50 3.90 46 2.26 40 11 88 264 5.96 59 5.06 66 4.29 61 2.81 44 1. 12 96 288 6.50 65 5.52 60 4.68 55 3.06 48 11 rt 13 104 312 7.04 70 5.98 65 6.07 60 3.32 52 14 112 336 7.67 75 6.44 70 5.46 65 3.57 66 .-s 15 120 360 8.11 81 6.90 75 5.86 69 3.83 60 <*^ 16 128 384 8.65 86 7.36 80 6.24 74 4.08 64 17 136 408 9.19 91 7.82 85 6.63 79 4,34 68 18 144 432 9.73 97 8.28 90 7.02 83 4.59 72 19 152 456 10.27 102 8.76 95 7.41 88 4.85 76 o6 m 20 160 480 10.81 108 9.21 100 7.80 92 5.11 80 21 168 504 11.35 113 9.67 105 8.19 97 6.36 84 22 176 528 11.89 118 10.13 110 8.58 102 5.62 88 23 184 552 12.42 124 10.59 116 8.97 106 5,87 92 24 192 576 12.96 129 11,05 120 9.36 111 6,13 96 40-Inch Section {Steam or Water) — 10.75 Square Feet. Height 41-^ inches. Width 9\ inches 5f INCH CBNTEHS 5 INCH CENTERS 4f INCH CENTERS 4 INCH CENTERS 7 75.26 226 6.12 38 4.34 35 3.67 32 2.45 28 8 86.00 258 5.86 43 4.96 40 4.20 37 2.80 32 9 96.76 290 6.57 48 5.58 46 4.72 42 3.15 36 10 107.50 323 7.29 54 6.20 50 5.26 46 3.60 40 11 118.25 355 8.02 69 6.82 55 5.77 51 3.85 44 f« 12 129.00 387 8.74 65 7.44 60 6.30 55 4.20 48 3'^ 13 139.75 419 9.47 70 8.06 66 6.82 60 4.56 62 s?f 14 150.50 452 10.19 75 8.68 70 7.35 65 4.90 66 ^ 18 193.60 681 13.09 97 11.16 90 9.45 83 6.30 72 19 204.25 613 13.82 102 11.78 95 • 9.97 88 6.65 76 CO ro 20 215.00 645 14.54 108 12.40 100 10.50 92 7.00 80 OS 21 226.75 677 15.26 113 13.02 105 11.02 97 7.36 84 22 236.50 710 16.98 118 13.64 110 11.56 102 7.70 88 23 247.25 742 16.71 124 14.26 115 12.07 106 8,05 92 24 268.00 774 17.43 129 14.88 120 12.60 111 8,40 96 33 34 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS REGULAR SECTION— Continued 50-Inch Section {Steam or Water) — 13.5 Square Feet. Width 9i inches Height 50^ inches. o O H z a 5J INCH OENTEHS O* SFCTIONS 5 INCH CENTERS OF SECTIONS 4f INCH CENTERS OF SECTIONS 4 INCH CENTERS OF SECTIONS 52% of Face Standard 44% of Face 37% of Face 24% of Face o O \4 SI a u aS 0) p a a (3 Z, a. H 3 S Net Air Space in Square Feet tWidth of Stack in Inches Net Air Space in Square Feet tWidth of Stack in Inches Net Air Space in Square Feet Width of Stack in Inches Net Air Space in Square leet Width of Stack in Inches 7 94.5 284 6.35 38 5.37 35 4.55 32 8 108.0 324 7.25 43 6.14 40 5.20 37 9 121.5 365 8.15 48 6.91 45 5.85 42 10 135.0 405 9.05 54 7.68 50 6.50 46 fl 11 148.5 446 9.95 59 8.45 55 7.15 51 o ^3 ,J3 12 162.0 486 10.85 65 9.22 60 7.80 55 22 —.9 la 13 175.5 527 11.75 70 9.99 65 8.45 60 14 189.0 567 12.65 75 10.76 70 9.10 65 (B S' ti'a 15 202.5 608 13.55 81 11.63 75 9.75 69 it 16 216.0 648 14.45 86 12.30 80 10.40 74 g2 l« 17 229.5 689 15.35 91 13.07 85 11.05 79 9 fl .2 S Pi . 18 243.0 729 16.25 97 13.84 90 11.70 83 Si ^ 19 256.5 770 17.15 102 14.59 95 12.35 88 CO ta 20 270.0 810 18.05 108 15.36 100 13.00 92 21 283.5 851 18.95 113 16.13 105 13.65 97 22 297.0 891 19.85 118 16.90 110 14.30 102 23 310.5 932 20.75 124 17.67 115 14.95 106 24 324.0 972 21.65 129 18.44 120 15.60 111 t Note — Add to the width of stack 2J inches for staggering of stacks — except 4 inch centers not staggered. * Note. — The actual length of one-inch pipe per square foot of outside surface is 2.9 lineal feet but is nominally figured at 3 lineal feet, as shown in the third column of above tables. REGULAR SECTION— RATINGS AND FREE AREAS 60-Inch Section {Steam or Water)— 16 Square Feet. Height 60^ inches. Width 9 J inches. O H b, m a SS li H hJ S * 5| INCH CENTERS OF sections' 5 INCH OENTEES OF SECTIONS 4| INCH CENTERS OF SECTIONS CQ NUMBEK OF SEC- 52% of Face Standard 44% of Face 37% of Face 3 Net Air Space in Square Feet tWidth of Stack in Inches Net Air Space in Square Feet tWidth of Stack in Inches Net Air Space in Square Feet tWidth of Stack in Inches 7 112.0 336 7.62 38 6.45 35 5,47 32 8 128.0 384 8.70 43 7.37 40 6.25 37 9 144.0 432 9.77 48 8.29 45 7.03 42 10 160.0 480 10.85 54 9.21 60 7.81 46 11 176.0 528 11.93 59 10.13 55 8.59 51 S 12 192.0 576 13.00 65 11.05 60 9.37 55 if 13 208.0 624 14.08 70 11.97 65 10.15 60 14 224.0 672 15.15 75 12.89 70 10.93 65 d'S 15 240.0 720 16.23 81 13.81 75 11.71 69 ■«■% 16 256.0 768 17.31 86 14.73 80 12.49 74 ^£ 17 272.0 816 18.39 91 15.65 85 13.27 79 "g 18 288.0 864 19.46 97 16.57 90 14.05 83 ^l 19 304.0 912 20.54 102 17.50 95 14.83 88 CO m 20 320.0 960 21.62 108 18.42 100 15.61 92 a> 21 336.0 1008 22.70 113 19.34 105 16.39 97 22 352.0 1056 23.78 118 20.26 110 17.17 102 23 368.0 1104 24.85 124 21.18 115 17.95 106 24 384.0 1152 25.93 129 22.10 120 18.73 111 72-Inch Section {For Steam or Water) — 19 Square Feet. Height 7% inches. Width 9i inches 5| INCH CENTEHS 5 INCH CENTEHS 4f INCH CENTEHS 7 133 399 9.14 38 7.74 35 6.56 32 8 152 456 10.44 43 8.85 40 7.50 37 9 171 513 11.72 48 9.95 45 8.45 42 10 190 570 13.03 54 11.04 50 9.37 46 11 209 627 14.31 59 12.17 55 10.30 51 5 12 228 684 15.60 65 13.27 60 11.25 55 ll 13 247 741 16.90 70 14.35 65 12.18 60 Ig' 14 266 798 18.19 75 15.46 70 13.11 65 4i"a 15 285 855 19.49 81 16.58 75 14.06 69 t'4 16 304 912 20.78 86 17.70 80 14.99 74 te.S 17 323 969 22.07 91 18.78 85 15.92 79 »§• 18 342 1026 23.34 97 19.88 90 16.86 83 S» 19 361 1083 24.64 102 21.00 95 17.80 88 CO 03 20 380 1140 25.95 108 22.10 100 18.73 92 a> 21 399 1197 27.25 113 23.20 105 19.67 97 22 418 1254 28.52 118 24.31 110 20.60 102 23 437 1311 29.80 124 25.40 115 21.54 106 24 456 1368 31.10 129 26.50 120 22.47 111 * t See notes bottom of previous page. Note. — 60-Inch Sections can be assembled on 4-inch centers. 35 36 MECHANICAL EQUIPMENT OF FBDEKAL BUILDINGS CONDENSATION AND TEMPERATURE TABLES, ETC. The tables presented on the following pages are the result of the most thorough test ever applied to blast heaters. The data represent nearly 50,000 calculations. The results of the tests on temperatures and condensations were incorporated in a mathe- matical deduction which properly represents the theory of con- vection of heat. The tests covered a range of velocities of air through the heater from 60 feet per minute up to 2500 feet per minute. In these tests velociti^ were derived from actual air measurements with a manometer, and these velocities checked within an average of 2 per cent with the velocities calculated from the amounts of con- densation weighed. The data presented cover tests of six different Vento Heaters with steam at 5 pounds gauge pressure, and air entering at vari- ous temperatures below zero, at zero, and above zero. Data are also given of the performances of the heaters with steam at 30 pounds pressure, and with hot water circulation. % (A P m < I B % (A 1^ g H M o p O P5 g o o o g M d 2.82 2.89 2.66 2.31 2.05 2.69 2.50 2.37 a. 05 1.92 2.52 2.35 2.22 1.97 1.80 2.37 2.21 2.08 1.83 1.70 2.23 2.10 1.98 1.72 1.59 2.09 1.97 1.86 1.62 oor-co OSOOt- r- cDio ■ ooi-eD - gS§|S 3SOSO.-,M Z) .-,.-, (MM saal ■ III : c-oeo • CO-*"* ■ 8 00 d 2.65 2.54 2.42 2.19 1.96 2.54 2.37 2.27 1.96 1 79 2.38 2.23 2.08 1.85 1.69 2.08 1.96 1.85 1.62 1.50 1.96 1.85 1.75 1.52 »-t iH 1-J ■ t^CDiO ■ TflwlOSrlH^ cot-V-oso ggssss OJOO^-HW Oioooin MCqcOCO ■ : C0»OOS ', 332; : o s d 2.56 2.46 2.26 2.05 1.85 2.36 2.21 2.10 1.85 1.69 2.22 2.08 1.95 1.71 1.57 2.08 1.95 1.82 1.59 1.49 COOOOO oaoor-mitt oo*-< • l>.cOiO ; E^ fe COCOi-HCOCO cor-oooso 00 OS en .-,<-' •-H COi-hCO 00 OOrHCOCO SSSss S§S3 i sss • als 1 d 2.42 2,33 2.16 l.«9 1.71 2.20 2.06 1.93 1.71 1.57 2.06 1.91 1.79 1.58 1.46 i-IOoOCDt- OSOOcO-iJICO 00 t- CD CD I— t-CDiOCOCO SS^S^ : s^s CD coos Ttieoeo H f^ -^iraeooooo QO-*OMOS OOCftO.-,^ ioow:)»Oi-i O'-H^COCO oscojf-eo»-i ^(M&OCOTt- ssas : 323 ocom iO»OlO i d 2.23 2.17 2.00 1.69 1.54 2.00 1.89 1.77 1.54 1.42 SKS3:5^ COCOMCOCO C-cDiOCOCO Oi-Hcqco-iH CDiO-eJiNi-H OSOCCIO ■ OStH-* cocoes OCOIO COG'S—* 1^ osoocop^o ^lO CO 00 OS t-t~00OO CO CO 3; CO CO OS OS 0-,*-t CO' OiOOOS-^JH SSS3S COOSCOO ■ COCO-^VO ■ SSa 22I 8 o d OiC«OTt<'-H OSOSOOiO '^ Sg^SJSS ■OeOt-ooO COiOiJHjRiCO COtJIUSOSCO lO^COi-HO ^COCDCS'-H TJICOCOOO ^ ^ T-I »H y-i oeoifscq ■ eocO'-HO ■ -HID CO co^o ^°° i-IOQO"*CO IOCOCOOOC3S CD cooeoo t-COOSOi-H t-cogsoco C3SOOC0C^ lOO'^-^OO i-H CO CO CO CO O-^OOIOOS COCOCOTtH ^ C0U5COIO ■ ;33^i3 : (MU5CO lOiOiO TicoiO CO CO CO 1 d lO -tH ^ -tH CO I>-COiOCO(M t-COOS>-- lo in CD CO t-OSl-t COCOf- lOb-CJi 8 CO d 0»OC^"ii<0 r-coeD"5»o OOOOO 0.59 0.56 0.52 0.46 0.42 -HOOOOC- la.-n -# -# CO OOOOO »Oi-t 00n ^ ^ ^co« OOOOO OQOCDMOS ^_ CO CO CO CO OOOOO 0.34 0.32 0.30 0.27 0.25 COOCOOSIO 00 00 OSQ-^ ■^csscocqcD Meoco^'* (^^lOoo■^^- inioificocc o o Cond. Lbs. per Sq. Ft. per Hour COOOOCOi-1 ■*Ti< cococv; un CO r-Mr^ Hi CO CO CO OS (M OOOCOCO'-I fisrw (M c ooooc CO CO-* CD l> 00000 C0CO^COI>- p T— I CO CO Tj \< ir 5 C£ 5 1> - GO 37 k a a w •< f P M h \» M s w u g g O O iJ IM 6 ■ t-OQlO ■COOOS ■CO CO CO 3.42 3.24 3.08 2.90 2 78 3.17 3.11 2.88 2.76 2.63 2.98 2.85 2.72 2.69 2.46 2.82 2.69 2.56 2.44 2.33 2.66 2.65 2.44 2.33 2.22 2.62 2.40 2.29 2.1s 2.07 ■^00 CO -coco-^ CDC* 00 10 ■* ■* iO lO iCi 01 'ROCOCO CDi-HCDt^ CO I- 00 00 01 OS oaosOOO sgsss t-oeocOO> '^ i 6 ■ eg ■* t- ■i-iOil>. cooooo t— eg COOooi^eO O=O0t-CO"* 05lO"*C0i-l C- CO ID-* CO ■* ea oosr- cotrtrfcoTi CO CO CD coco •*COCO-T-IO SSiSSS ■coegei CO CO eg CO CO eg eg CO CO CO CO CO eg eg eg CO CO CO coco CO e^ eg CO CO egcocoe^iH H fi : ■■^r-HOO ■ co^ -* -^Ouoegoo ■* 10 10 CO CD cooo-^oco coco t- 00 00 Sooosoio t-i-HOOSCO OSOOOi-l Oeot-^'D i-li-H WCOCO CO ID 00 w* eg CO CO CO CO o s 6 igRg T-H t~0 OCD OQOt-cD-* t-coS^co 00 CO "*■»*<■* iD-*coefl^ coeiegcoeq "*COCO^O 000000010 eg--ioc»o» 2g§S5K -eg eg CO CO CO CO eg eg eg CO CO eg eg egcoe-H ID CO CD t- 00 OiOOlDO OOOOOS OiO gssss iDOOi-iiDCJi .-i.-Hegegco CO CO CO CO-* ocgTjfr-o 'J* "*■*■* 10 6 "* TjH-*cg(Mc; TtH CO CO --< C3S C^-* COCO ■* CO'-iOOJOO ■^.* CO 000 OOiOOt-t- t-OCO'*CO 00Q0 1r~COiD ■*i-0)eg-* C-COiOiO'* COlO t-.-.iO COlD-*'*CO >D*eoeoDi eg- M eg CO eg 1-1 CO eg cDOCO cot^-r^oooo t- i-i CO --> CD 000s 000 COO-* 00 eg O*-" i-li— c CO CO coo: CO ID CO CO CO CO CO t-osi-i-* r». eoco-**-:tH t-C3S.-ICOCD i d ID OS cocoeginrt* ^ O OiOO t- T-H CO-* CDOi OiOO t— coio COiO00.-«lD r- CO ID»D-* osco CD oeo U5iO'*'*CO COO"* 00 eg ■* ■* COCOCO CD 1-1 ID 0; CO cocoeg^^ ^SiSSg ^ egveg »-( i-h -< rHl-IW,-.^ 1^ CO coo:ioD ID t-Oli-l'* ifMCiiDCOCD o 6 igs 1CI--0 CO rjf C-_ CDCD lO ■* ID 03 eg coo 10-* ■* coco OiDOsCO CO -* CO CO eg 1-1 CD eg i>- CO CD coe]i--"i-(o s;::§gfe t-C0 00'*O OOi OSOS O0"*0t-C0 OS OS OS 00 00 ooooo . :^^ lo 1ft -to O t- 00 00 0=050 COO-* t-— 1 Oi-li-l -rt7-ib-coci 03 Ol CO CO tr— 0:1 CO eg Oi ID 1-- t^lr~ CO CD OOiDCg OiO coco CD 10 ID ooooo OOOOO ooooo B ri "TjH^OO'raCS) CO-* -Iff lO CD CO 00 CO t~ CO oococncjo c»co>DO=eg r-^CqcO coco o d CD CD CD »0 iS »o in'^ 'Tt* -* iDcoegooo ^ .^ rti ■5* CO OOOOO ooooo ooooo 1^ Ol »iO »-< l>- CO IsiSS CD oseg »Doo CO CO -*■*-<*' s Cond. Lbs. per Sq. Ft. per Hour OCO-*^^ C3S »r3»« inu^ ■* 00 t- "D-* CO CO CO CO CO CO ooooo ooooo ooooo Final Temp. Air Leaving Heater e^oo^ocD lOiocDr^i:^ »0 Oieo i>- 1— 1 OO^i-HCO CO CO CI eg ■*"*^-*>o HIV DKIHaXNa o o p o o ^eotg-H OOOOO ^coco^ OOOOO ooooo ■*COCO>-' .0 ■*coeg-H 1 1 1 1 ooooo 7=777 ssgs° m E O ^ H E- a i-H cq CO ^ LO CD t- 00 38 o < f P z K g EH (^ g M 13 W tij o c § & s cq 6 tH COi-li-l<0 t- U5 T* ,-( Oi iO'«*<(NO00 1— 1 CO i-H T-H CD lOCOMOlt- OOCOi-ti-l CON^OOt- lcO-*OSift CO cq .-( C3S c- CO cO-*i-iQOeO i-lOOSCDlft CO-*.-lt-t- 00s 00 Ift-* oosr-ifti ■ OOOt-lO ■ MMMM^ CqiMIMMrt Me-Hi-H[MeqMi-ir-i|Mc- CO ■* tNOt-lft iftCOt^OOOi i>-ir^ooc»o SggggS Ift >-( cDCO-j' osooi— 1 cq C0 1-1 cot- eg Oi-i.-0 ^cqcMco* 01 cot- 10 OS cqcoco** OCOCOCOt- ***ift >ft oseg 100 • *iftiOCO • s d C7a C-- >— 1 CO ^H cooiococq "*iOCOO5 00 io-*-<0 ^1-1 1-100 w,-ii-<00 t-H 1-1000 — -10il 00 CO 00 00 CO 0^--MCO cqcqco-*-* CDOCOO* co-*-*ioin cDoscq cQcq -*-ttHlftlft CO CDCOi-o ift .-HM C^tCO* CO CO CO ■* 10 ■^-^IftlftCD CO coos »0 00 Ift Ift m CO CO cococDcS : « d cn iftO cooo OICO iM CO Cil CM01>-.-l 00 10 ift^nHco 00000 00000 00000 E-i fa' SSggg CS OOC^ M ■*Osco.-i CO o d sssss ^H 00 COM CI ■IJHCOCOCOM coeocoiMM 00000 00000 00000 fa -JtO t— "-I 00 t- 00 0000 OiOOOiO .-l^MCOCO t— 1-1 10 CO b- CO -rtl ■* lO 10 I Cond. Lbs. per Sq. Ft. per g CO^OOCOO ■*}( T»( CO CO CO CO -^ (M 00 CD CO CO CO (NM ocsir--*co COMMCMtN 00000 00000 00000 Final Temp. Air Leaving Heater I--rf 000 I^-QOOi-*'-' u^iOSrfCOOO •-I >— f IM COCO .-(Ift OICDO ■*"**ift«D V o NiaaxNa ivaadwai 00000 (McO"^or* ggsgg 00000 (MCO^COI-- sssse 00000 cqeo-^cor- gssss ssssg 00000 eqco*eDt- « n s a (A T— 1 (M CO -^ CO t- 00 39 QQ iz; o S P O O H a (0 < f s z s « g Q Eh ■«! g O K M h § CM d ■CM-* ■OOS ■CO CM 3.22 3.07 2.92 2.77 3.20 3.05 2.90 2.75 2.64 3.04 2.89 2.74 2.62 2.50 2.92 2.79 2.66 2.54 2.41 2.80 2.67 2.54 2.41 2.30 2.66 2.54 2.43 2.32 2 91 2.66 2.44 2.34 2.24 2.14 2.44 2.35 H ri OOS MM »Oi-H t— MO ■ CM CM CM CM [:-cDtH-M ■^lOCDCOt- cDi-HCD i-ir^ cor- t--ooco .-HiOO-^OS CO 00 en OS OS »"ssS ssS5S t-OT|<00CM .-•CMCMcqcf ss i d -( OS cm' CM OS CO CO m ■"*< CM C COM-*-*-* as o d S2gS CMCMC^i-C (Mt-HOOSOO CI CM CM — ■ T-( t^OOOSOStN OC3S CO t— t— N 1-1 T-i i-i .-H Osooc-Sco sss:gs?s s^^^^ CM»OOSCM«D COiO-^-^M 3^-i'SSS "OOS ■*co "■ ^COiOCM MM"^ lO OSiO w t-,-* ■ttiiOCOCO t- OiO O »Oi-H f— t~- 00 CO OS OiMCOCM t— CO OS OS O O CO CJSCM CDO 00.-i^CM i-cgit-OM CM CMCMMM CM lO COi— 1 ■* MPOeo-* ^ SSSss .f^ 1 d 2 ^H OOi-i CM ^OaOiCOt^ OaOOt-SS sgsss C-0>C<)iOOS ^ iom-*M CDOiCM inOS lO-^ ■* COCM cDO-*C---i -^■*cO(MCM CD »-< ira OS ■* MMCMi-li-( t-CMr-cMh- CMCMi-li-iO -HrH CQ H fe ^CM o.-l.-i IflCOi— 1 ■* 00 .-1 .-KM CM CM OiCq lOOO— ' CMCOMM-* — i"*cDOOi-l ■*rK^-cM- OO CO CJSMt-i-HiO OOOSOSOO CO CM too-* O— 1— ICMCM 10 00.-H -^OO CM(MMMM OS C-0 lO "5 lO >0 CD riCpCDCDCD OS-i-l g d CO Oi eO'-H OO cncocooot- dcsoocJ o d o d o o^--:J^.-lco t^-CDCDcD lO d o d d d o ■■Si T H h cMdi--".^^ en CD coo CD lO >0 docsdd to C^ --I CO CD ddood QOlO CO -H 0= ■*-*'*-^ M ddddd ■■s C5 1-C1CDW □0 00 OS OS o 00O-5HI— .-i ^(MCMCM M o C3 ddddd COcD-^JHcqO .— 1 OS t- CD ■»*( -^MMCOM ooood g. ^ (^eOOCDM M-* lOiCO OOCM CD OiO COOS OiOO MCDOS C<1 m <*^CqWMM HIV ooooo 1 1 r 1 ooooo ooooo 1 1 1 1 I 1 1 1 r>oooo 1 1 1 1 OOOOO OOJDOO 7??°° OOOOO 7777 DO *eo 1 1 B n S c fe o a O ^i-ti-lOO 1 0000^ 0000 00000 00000 00000 00000 00000 00^00 00000 00000 00000 (M CO ''tl 10 CO 41 rn S- M ^ ■^ i^ O H ^ S «i ^' i m n ^ G f. W S tt fO O l^ e ( ) M u 4^ ?; ^ i ^ m CO ^ W W g o n <1 Pi w ^J tH PL, F1 § w 3 H f- < O ^ f^ ^ 0^ B fe F=4 (M(M M MW ■^(MtMCqiMrMNfM M (M (M -■ (M W CO W(Mt- <0 t— CO ■ Ocnoo CI 1-1 1-1 lO "* CO CQ 'i <1 M M N cq cfl c0 lO lOcO ' ooooo eoococo o C-- t- CO CD (D ooooo ooooo ooooo ooooo CO cocoon ooooo ooooo ooooo ooooo ^w HIV oNiaaxNa Lio aaaiiVHadHai m fe 5 w S o <; H !3 t- n O OQOO 1 (M CO ^ »o CD 42 D % 3 « h fa 1 a a g § g (if] i 6 2.95 2.76 2.58 2.21 2.03 2.76 2.68 2.49 2.21 2.03 2.64 2.52 2.40 2.09 1.91 2.53 2.39 2.26 1.98 1.84 MOOt^ gj; 2.34 2.21 2.09 1.81 1 69 egegcfl "* e^ CO 001>-CD-* CO OSOOOi ooo D-CO W3 CC c-I ooi-Toeg ^^-colOcoeg com-* CO H ri locor-osm SSSSgg OO "Oi-t CO OS OOOSQ v-< I— 1 .-(COM e^oo 0_0 v.^ M »o -^ e] i-H t-r-ooo iQ^-^cgiM coco oeg »o "^Hcoegi-io 1.37 1.28 1.21 1.06 0.97 1.28 1.20 1.14 1.01 0.93 0"*r- cgi-*o 3 H ti uscoeqoco TffiOCOCOCO loegoioeg o C— OOOSO -#Ot-oair5 OOOSOSO 1-1 OS-^Oi-l t- osOi— 1 eg eg cor>Mcqco ■* 00 CO eg CD Megco^^ "*Qoeg coco-* ■* o g d 1.49 1.39 1.33 1.22 1 11 1.38 1.30 1.24 1.08 1.00 1.29 1.22 1.14 0.99 0.92 1.19 1.12 1.06 0.93 0.86 1.10 1.04 0.98 0.86 0.80 1.03 0.97 0.92 0.81 0.76 o'cDO OS o' Eh t-io-tf0 eg »o s eg d ooooo U.64 0.61 0.58 0,50 0.46 COiOCil lOiOlO ooco H N o t— »ooco CO cor- OS OS ococo-*0 3=oso-.eg U5010 i-iegcg a d coocoor- u:.u3-^-*co o o o' o O locgo-*— 1 Tp-*^eoco ooooo' CO coco o"oo. p4 gssss ^Hco egcg r- oo— >ejeg r-^co eg CO CO I Cond. Lba.per Sq. Ft. per Hour O o o d O o" o o' o o Tftegi-i CO CO CO o'o'o Final Temp. Air Leaving Heater iOOcDCOi-i -HiOO coco^- JO aaniVHaJKaii ooooo OOOOO eg CO-* cor- ^^5§S OOOOO eg CO-* cot- ooooo cqco-^tor- ooooo eg CO-* cot- ooooo Cqco-*cDi^- ooooo eg CO-* cot- n S P 15 tH (N CO ^ H ir 5 «3 l> a 3 43 o f i H Oi [i. g PJ n a o g g s ;> o i d ■ ■ - ■ CO ■ . CD l-~ to ■ -CViOCTi "*CM001CO CO CO 00-* OS (M-hOOOCO sssgs Ot--'*i-ICO OOOt-cD-* ggssss : : : ;" . .COCOCN CO CO CO (N (N C0C0 1M.t^00 00OS sgsss ... -co § CO d ■ ■ - -00 . . . .OJ - -OCON • •t-lCS.OO CO t-ocom .»fs-()«eoN ■ ■ • -N ■ -COtMtM C0CO(N-l t^ lOiOCOb-t^ c— cq t— cgoQ CD t- t— oooo OJ CO 00 CO CO t-QOOOOSOl OSOS0900 o o CO d 1 : . ^o ■-*OlOiO •Ocnir-cD O CO t- co»o OOt-COiOCO sssss i-HOSOOOOt^ cO"*coeqi-i iO-*Ni-<0 •COMMW coiMcqcqcsT (Meqo SSSSSg ifSCOCOt^OO KRSSsg rJICOCOGQCO CO OO OS OS o sssgs g d ■■-(DiO I-iO"*CO(M ■^ CO(N T-ICO lO-*COCMi-l SSSgg CO CO CD t- 00 (M .-100=00 CD t--t>00O 1— I O OS CO 00 SSfeSS '■ '■ l^M . . .- COt-I>-00Oi COt-Ml-.h-COO3 D4<-l OQSOO ^■^lOcDb- 1-I005 00C.- Or- CO-* CO OOiOOt-CO OSOOt-CO Ui oor-cDio-* ■ "(MfMM (MM(M(M(M c-l>-00 00 lOOlCOOOCO OO 00 OlOSO aicot--i--CnM t-coio-*-* OCOCDOCO COiO-^ ^ CO ooc^iocn CO "*.=SHCO.i-liOO-* COCO(M sssss sssgs "*b-OCOCO IM C<1 COCOCO ■*i>-oeoco CO CO ■*■*■* ■ttl»-*-*rf CO ■oooo ooooo ooooo ooooo fa ■coo t^TiH -H CD 1-1 CD 1-1 C-l>-00 00Oi |gSS| OCM»OCOi-i coco coco-* o o Cond. Lbs. per Sq. Ft. per Hour CD =D 1^ lO lO sssss OCO t— ii3CO ^CO CO CO CO O O O O O ooooo ooooo ooooo Final Temp. 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O H O a, tia 0>^H f^^D li aiv jaaa S30VX9 (N CO 50 lO CO 00 05 HBATING AND VENTILATION 51 Prime movers. When engines are used, which is seldom, they are vertical, single or double-cylinder. Engines are direct-con- nected where possible and are provided with throttling governor. Motors, if direct-current, are direct-connected when speed of fan is 300 turns per minute or more. If current is alternating, the motor is belted to the fan or connected by a silent chain drive. Flange or flexible couplings are used for direct-connecting motors and engines. Steam and return piping. D = diameter of pipe in inches. L = length of pipe in feet (one way) . W = pounds of steam per minute. P = loss of pressure, usually one pound per 300 feet. if = a constant as follows : Diameters (inches) 1 2 3 4 5 6 7 8 K= 104 140 160 169 173 180 183 187 For steam above 30 pounds pressure pipe is made half the diameter given by the formula, and for pressures of 10 to 30 pounds main is made two-thirds that given. Return main one-half diameter of steam main, and make it "wet." Place the bottom of coil as high as possible above water line in boiler, pump governor, or trap; never less than 18 inches and preferably 24 inches. AIR DISTRIBUTION SYSTEMS Trunk main system. Trunk mains are used for Cases I, II,. and V, except where cone fan is used. Where continuous ven- tilation is not necessary or where air change is much greater than necessary for proper ventilation, this system is used for Cases III and IV, except for cone fans. The following instructions are to be observed in laying out the duct systems: Main duct at fan is to be made the same size as fan outlet, which has been given heretofore. Refer to the equalization table 52 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS given hereafter and note how many pipes 1-inch x 1-inch are given as being equal in carrying capacity to this main duct. Di- vide this number of 1-inch x 1-inch pipes by the capacity of the fan in cubic feet per minute. This will give a fraction which is the portion of a 1-inch x 1-inch pipe to be allowed for each cubic foot of air. Now multiply the amount of air delivered to the base of each flue by the distance of said flue from the fan (dis- tance means the length of duct, adding equivalent for turns, etc.), and divide this product by the amount of air handled by the fan. This will give the "average distance" of all outlets from the fan. Next multiply the amount of air to each flue by the fraction above obtained in dividing the total cubic feet per min- ute by the number of 1-inch x 1-inch pipes in the main duct at fan. This will give the number of 1-inch x 1-inch pipes to be allowed to each flue. This number of pipes is subject to correc- tion as follows : For each one foot by which the distance (includ- ing equivalent for bends) from fan to base of flue exceeds the "average distance" previously obtained, one-third of 1 per cent is to be added to the number of 1-inch x 1-inch pipes previously allowed for each flue. If the distance is less than the "average distance" the correction is to be deducted instead of added. Now refer to equalization table and find the size of square pipe equivalent to the corrected number of 1-inch x 1-inch pipes for each flue. This is the size of the branch pipe at the base of the flue. Add all the branches back to the fan on the equalization table, and if the work is correct it will add up the size of main duct you started with. Take an example : Fan with 54-inch x 54-inch outlet to handle 28,000 C.F.M. 54-inch x 54-inch pipe = 21,000 1-inch x 1-inch pipes, 21,000 -^ 28,000 = 0.75. OUTLET NUMBER DISTANCE FROM FAN IN FEET C.F.M. C.F.M. TIMES DISTANCE NUMBER 1 INCH X 1 INCH PIPES 1 2 3 50 50 60 110 6,000 2,000 10,000 10,000 300,000 100,000 600,000 1,100,000 4,500 1,500 7,500 7,500 4 2,100,000 2,100,000 -e- 28,000 = 75 feet (the average distance). HEATING AND VENTILATION 53 OUTLET NUMBER DISTANCE TO BE CORRECTED FOR AMOUNT OP CORRECTION CORRECTED NUM- BER OF 1 INCH X 1 INCH PIPES SIZE OF BRANCH 1 -25 -25 -15 +35 -375 -125 -375 +875 4,125 1,375 7,125 8,375 inches 28x28 18x18 2; 3 35x35 4 37x37 The main to carry branches Nos. 3 and 4 would be 8375 + 7125 = 15,500 = about 47-mch x 48-inch, etc. Rectangular pipes to he same area as square pipe when ratio of width and depth is not more than 3 to 1. When this ratio is greater, add to area as follows: 10 per cent for a ratio of 4 to 1, 20 per cent for a ratio of 6 to 1, 30 per cent for a ratio of 10 to 1, etc. If round pipes are used in some places the diameter of same = 1.10 times side of square pipe. If roupd pipes are used throughout they can be handled just as we handle square pipes, for the equalization table applies to round as well as square pipes, but not to both at the same time. In starting from the fan it is only necessary to make main pipe same area as fan outlet. Plenum chamber. Section of plenum chamber to be large enough to produce a velocity of not over 250 feet per minute, across it, and should be as nearly square as possible. Velocity in ducts from chamber to be about 800 feet per minute for cone fans and from 900 to 1200 for steel plate and other fans. By-passes, etc. By-passes around heating and tempering coils to be not less than 10 per cent nor more than 15 per cent of the gross area of the coil when they are provided withthermostatically controlled dampers. By-passes under heating coils of plenum chamber and double-duct systems have no dampers and should be not less than 25 per cent of the gross area of the coils. Vertical flues and registers. Velocity in vertical flues to regis- ters to be about 600 feet per minute, and through registers to be 200 feet through gross area, which gives about 300 feet over the net area. When air is admitted over 10 to 12 feet above the floor the speed through registers may be increased to 400 feet per minute of net area. Floor registers are never used. 54 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS Resistance of ducts. The following formula, which is accepted as good practice, is used: P = loss of pressure in ounces per square inch. I = length of pipe in feet. V = air velocity in feet per second. d = diameter of round duct in inches. (To reduce ounces to inches of water multiply by 1.73.) Should the duct be rectangular the size of equivalent round duct is found by the formula: "-V^ Z2a?h^ {a+h)' when D = diameter of round duct, and a and h = the dimen- sions of rectangular duct. The resistance can then be figured as for a round duct. The following formula is more generally used : A ' in which the symbols are the same as used above except : S = rubbing surface in square feet. A = area of duct (regardless of shape) in square inches. K = 0.00012 for galvanized piping. K = 0.00022 for brick or concrete ducts. V = air velocity in feet per second. Bends. Bends in square and rectangular pipe should be turned on a true circle; it is entirely practical to make them in this way. Branches from mains are made on easy curves as a true warped surface from outlet in main duct to point where branch duct as- sumes its true section. When so constructed the resistance of each elbow is equivalent to a certain number of diameters or (in case of rectangular ducts) widths, as follows: HEATING AND VENTILATION 55 Radius of throat to diameter or width of pipe 0. (square turn) 2 and above Equivalent number of diameters, or widths, of straight pipe 100 65 30 10 6 5 Great care must be taken to insure that air ducts run as directly as possible and that changes in relative dimensions, offsets, etc., are avoided, as each such change adds a small amount of friction. Branches should in general be taken from the side of main and the depth of branch at main should be same depth as main and be connected to main as nearly tangent to main as possible. Example: A 12-inch x 12-inch branch to be taken from a 20- inch X 48-inch duct, the branch at main to be 7f inch x 20-inch and the taper made to 12-inch x 12-inch before the 90° turn in the branch is started or taper made in the bend. EQUALIZATION TABLE "A" ■■b" ■A" "b". "A" •■b" 1 1 20 1,788 39 9,498 2 5 21 2,020 40 10,119 3 15 22 2,270 42 11,432 4 32 23 2,537 44 12,842 5 60 24 2,821 46 14,351 6 88 25 3,125 48 15,963 7 129 26 3,446 50 17,678 8 181 27 3,788 52 19,499 9 243 28 4,148 54 21,428 10 316 29 4,528 56 23,468 11 401 30 4,929 58 25,620 12 498 31 5,351 60 27,886 13 609 32 5,793 62 30,268 14 733 33 6,256 64 32,768 15 871 34 6,741 66 35,388 16 1,024 35 7,247 68 38,131 17 1,191 36 7,776 70 40,996 18 1,374 37 8,327 72 43,988 19 1,573 38 8,901 74 47,106 56 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS Column "A" is the diameter or side of the square pipe in ques- tion. Column "b" is the number of 1-inch diameter or 1-inch x 1-inch square pipes equivalent to the pipe in question. Dampers and deflectors. At each branch a deflector with easy and quick adjusting device should be provided. Deflector should be large enough to close branch completely. When this is not practicable, place a damper in the branch duct. In exhaust piping (when exhaust fan is used) place damper in each branch duct. Example : If a 12-inch diameter pipe will carry a certain amount of air a certain distance with a certain loss of pressure, there would be required 498 1-inch diameter pipes, or 498 -^ 88 = 5J 6-inch diameter pipes, to carry the same amount of air the same distance with the same loss of pressure, or 498 1-inch x 1-inch pipes would have the same carrying capacity as one 12-inch x 12-inch pipe, etc. A more extended table of this kind is given in Trautwine's Pocketbook under the heading of "Square Roots of Fifth Powers." The formula is : N= W/^V, when V(4)' A = diameter if round, or side if square, of larger pipe. b = diameter if round, or side if square, of smaller pipe. N = number of smaller pipes to equal in carrying capacity one large pipe. Air washers. Air washers are installed except in very unusual cases. In any event the apparatus is arranged and designed for the future installation of an air washer. Most of the standard makes of washers and ehminators are about 8 feet total depth and the cross section is such as to give through them about 500 feet per minute velocity, excluding the portion cut off by the settling tank. A good washer will saturate the air passing through it to 60 to 70 per cent of the dew-point. It is desirable to carry as much moisture in the air of the rooms as possible, to avoid condensing same on windows. The maximum percentage of saturation that HEATING AND VENTILATION 57 can be carried to avoid such trouble appears to be about a mean proportional between the inside and outside temperatures. Thus with 70° inside and 10° outside this percentage of saturation would be (70 + 10) -r- 2 = 40 per cent. Frictional resistance. The following data covering a well- known air washer are taken as representative of the standard makes : VELOCITY, FEET PEK MINDTE IN WASHER PROPER IN ELIMINATOR TOTAL 450 0.10 0.14 0.24 500 0.12 0.17 0.29 550 0.13 0.21 0.34 600 0.14 0.24 0.38 650 0.19 0.26 0.45 The friction is inches water guage. Preferable velocities. A speed of 450 for small washers to 550 for large ones is used as a standard. Pumps. Each washer has a separate centrifugal pump, driven by a direct-connected motor used for no other purpose. The following table is used as a guide in selecting pumps and motors: o.r.M. BnCTION DISCHARGE SPEED B.H.P. inches inches 5,000 2 n 900 n 10,000 2i 2 900 If 16,000-25,000 3 2J 750 2i 30,000-50,000 3 3 750 31 55,000-70,000 3i 3i 650 4 80,000-100,000 4 4 650 4i There is considerable variation in the speeds and B.H.P. of pumps of the various makes, therefore when laying out the wiring the motors are wired for about twice the B.H.P. given. Humidifying systems. Humidifying systems are generally installed with air washers. These consist of a closed feed water heater between the pump and washer, the steam supply to which 58 MECHANICAL EQUIPMENT OF FEDEBAL BUILDINGS is regulated by a humidostat, a steam coil in the air washer tank or a steam jet in the washer tank. Unless steam at a pressure of 5 poimds or more is always available one of the two former are necessary. Different makers of air washers vary somewhat in their methods of humidifying and control of same and with this in view the office does not go into details as to these points but states the conditions to be met and the result that must be secured. The results that must be secured are that the air must never leave the washer above 70° and the controlling devices must be capable of easy adjustment to vary the percentage of relative humidity anywhere from 45 per cent to as high as the outside tem- perature will permit. The manufacturers generally do this. Temperature losses. The loss in temperature of the air pass- ing through an air washer is capable of rather exact determina- tion for a given set of conditions, but conditions are so variable that the worst conditions that may be expected are used as the basis of calculation. It has been found in practice that the loss in temperature is 8|° F. for each grain of moisture absorbed per cubic foot of air. It is the moisture absorbed that is the uncertain part. The fol- lowing example will illustrate: Inside temperature 70°. Outside air 0°. Outside humidity 50 per cent. Maximum humidity that can be carried is 70 h- 2 = 35 per cent. At 35 per cent satu- ration and 70° each cubic foot of air contains 2.8 grains. We may assume that the air will be 80 per cent saturated on leaving the washer. Outside air at 50 per cent saturation and 0° contains 0.25 grain per cubic foot. Now 2.8 —0.25 = 2.55 grains moisture absorbed by each cubic foot of air. By figuring the heat required to evaporate one grain it will be found that it is just sufficient to drop the temperature 7.6°. But there is a further loss due to cooling effect of the water, etc., making the total loss 8§° for each grain evaporated per cubic foot. We had 2.55 grains evaporated and our temperature loss would be 2.55 X 8| = 21.6°. Since each cubic foot of air at 80 per cent saturation is by our hypothesis to contain 2.8 grains water, the amount of water at 100 per cent saturation would be 2.8 -r- 80 = 3.50 grains. The temperature of air required to maintain a HEATI>fG AND VENTILATION 59 dew-point of 3.5 grains is 45°, which is to be the temperature leaving the washer. Our tempering coil must then raise the air to 45° + 21.6° = 66.6°, and our heater coil must raise it from 45° to whatever temperature we have assumed at the fan. In view of the varying outside air conditions it is the practice of the office to have sufficient tempering coils (not less than three sections deep) to raise air from minimum outside temperature to about 67|° and have it under accurate thermostatic control, axid assume a temperature loss of 17|° in passing through the air washer. Automatic control of coils when air washers are used is dis- cussed under that heading. Double inlet fans. It has been found that so long as the area of the inlet is smaller than the area of the outlet the capacity of the fan varies directly as the cube of the diameter of the inlet. A fan with two inlets will handle twice as much air as with one inlet of the same diameter, provided the "equivalent" of the two inlet areas is not greater than the outlet of the fan. If we had a fan the standard inlet to which is, say, 60-inch di- ameter, and wanted to put two inlets and have the capacity of the fan remain the same, the diameter of each inlet should be 60 H- ■\/2= 48 inches. In other words, two 48-inch diameter inlets are equivalent to one 60-inch diameter inlet. The horsepower for the fan would not be materially changed by this change in inlets. If we should take the fan above, in which the one 60-inch di- ameter inlet is about the same area as the fan outlet, as is usually the case, and put another inlet of the same size, the capacity of the fan would be increased by \/2 as a multiple. It would not be doubled as above, because the equivalent of the two 60-inch in- lets is much larger than the standard outlet. The pressure would be doubled, the capacity increased nearly 50 per cent, and, as the power varies as the product of pressure and capacity (assuming the efficiency to remain the same), the power would be increased by three times. Shop testing of fans. Shop tests' of fans are not now required to be made in the presence of a representative of the office except when a style of fan is to be used upon which the office has no ac- curate data based upon a shop or other satisfactory test under 60 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS conditions applicable to the case in question. The standard method of specifying a fan when such test is required is to state the peripheral velocity of wheel, the minimum diameter of wheel, the maximum brake horse-power, and the capacity; and, if re- quired by structural conditions (such as ducts of a given size to which connections are to be made), the size of inlet or outlet, as the case may be, together with any other necessary dimension, is specified. The total friction loss is carefully estimated; and, in testing, the outlet is fitted with a straight pipe about 50 feet long of same size as fan outlet. A blast gate made of slats not over 2 inches wide is placed at the end of the pipe. The fan is then run at the peri- pheral velocity specified. The Pitot tube is inserted about 25 feet from the fan and the slats in the blast gate are withdrawn until the average static pressure at the Pitot tube is equal to that specified (allowance being made for friction between fan outlet and Pitot tube according to formulae hereinbefore given) . When these conditions are adjusted, the capacity and power are meas- ured. Capacity is measured by high-speed anemometer at end of pipe just inside the blast gate, and is checked by the Pitot tube. Ordinarily, measurements made at the inlet are useless on account of the whirl of the air giving unreliable readings, but sometimes reliable anemometer readings can be made on the inlet side, as in the air intake to cold-air room, etc. Power is measured in the most convenient and accurate manner. It is generally preferable to have the fan driven by the motor that is to run it after installation, measure input to motor and correct for motor efficiency and transmission loss. The cross section of the duct is divided into a number of rect- angles of equal area if rectangular, and if circular it is divided into concentric rings of equal area; and readings are taken in the center of each subdivision. The average static pressure is the average of all the static readings and the average dynamic pressure is the average of all dynamic readings. The average velocity in the duct is the average of all the ve- locities. The velocity at any given point can be determined by the following formula: HEATING AND VENTILATION 61 7=15.9 V#^ X Vel. (in.) in which Y = Air velocity in feet per second. T = Temperature Fahrenheit. Bar. in. = Barometer inches mercury. Yel. in. = Velocity pressure inches water (water at 72°). This formula is based air at 50 per cent saturation. For air temperature of 62° and barometer of 29.91 inches mer- cury the formula becomes . 7 = 67.50 VVdliT. An easy rule to remember for temperatures about 60° is 1- inch water velocity pressure = 4000 feet per minute air velocity. For other velocity pressures the air velocity varies directly as the square root of the pressure; thus \ inch water = 1000 feet per minute air velocity and 4 inches water pressure = 8000 feet per minute air velocity. If the different velocity pressure readings in the different sec- tions of the pipe are very close together it will be sufficiently ac- curate to compute the average velocity from the average velocity pressure, but if there is considerable variation, as there nearly always is, the air velocity for each reading should be computed and the average velocity arrived at as an average of all velocities. From the known area of the section the volume in cubic feet per minute can be computed. The Air Horse Power (A.H.P.) or work done by the fan can be computed from the formula , „ ^ C.F.M.XD.P . , . , ^•^■^■= 635^ ^°^^'°^ C.F.M. = cubic feet air per minute. D.P = Dynamic pressure inches water = static pres- sure plus velocity pressure. This last formula is good for any air temperature and any barometer reading with water at 72°. 62 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS This air horse power divided by the brake horse power gives the efficiency of the fan. There is always a little static head at the fan inlet. This sta- tic head exists to very nearly the same extent whether the fan has its resistance on the outlet or the inlet. It is very hard to con- vert it into any useful work and in such tests it is charged up against the fan, no allowance being made for it. A Pitot tube made similar to the one described below has re- cently been put through an elaborate calibration test by the America Blower Co. of Detroit. Their standard was the Thomp- son electric air meter, the accuracy of which has never been ques- tioned. These tests proved conclusively that for the practical purpose of fan testing such a tube may be considered absolutely correct. The Pitot tube used by the office has a foot about 8 inches long, with an outer tube f-inch diameter and an inner tube j^- inch diameter. The inner tube is turned against the current of air and at the U tube registers the dynamic pressure. This inner tube is continuous. The outer tube has a ^-inch diameter hole on each side about 5 inches from the toe to receive static pressure and at the heel a ^^-inch tube runs to the same U tube as the inner tube, and, being connected to the opposite leg, the air ve- locity pressure can be read on the U tube. A "Y" may be in- serted in the rubber connection and run to another U tube to read static pressure. The outer tube at the toe is about 2| inches shorter than the inner tube, and a bevel (of a piece of cast brass or solder) is made for this length and ground until the end of the inner tube comes to a sharp edge. All tubes are brass and the whole burnished smooth; and they must be tested statically for leaks. A tube as above described, carefully made, will give reliable results. The writer has tested such a tube by revolving it on a shaft in still air and found readings exactly as calculated. Vacuum systems. Mechanical vacuum systems, i.e., those having a vacuum pump attached to the return mains, are installed by the office only when exhaust steam is intended to be used for heating, or when a district heating service using this kind of sys- tem is available. In the latter case it is customary (except in HEATING AND VENTILATION 63 the largest buildings) to install a 2-pipe system, with a special arrangement of the return valves at the radiators, so that it will operate as a gravity-return system from boilers installed in the building, or as a vacuum system when the outside service is used. The steam mains are proportioned for a gravity-return 1-pipe system. The vacuum valves on the return of the radiators are of the automatic type, designed to pass air and water readily, but only a minimum amount of steam. The pumps for producing the vacuum are the ordinary type of vacuum pumps having an automatic control of the vacuum car- ried in the return at the pump by controlling the steam supply to the pump. Pumps are installed in duplicate, and are invaria- bly steam-driven. The pumps discharge into an air-separating tank so located that the water will flow to the boiler feed-pumps through the feed-water heater by gravity. No definite rule can be given as to the size of tanks. About 1 cubic foot capacity to 2000 square feet of radiation would be conservative, using a tank 18 inches di- ameter by 36 inches long as a minimum. A 2-inch vent line should be carried to the atmosphere to allow the air to escape. The make-up water for the boilers should be fed into the inlet of the pump; but there should be a make-up feed connection to either the air-separating tank or the feed-water heater, controlled by a float valve, to insure water for the feed-pumps in the event that the makeup valves at the pump inlets should be neglected. The steam and return mains are sloped in direction of flow when possible. The base of each riser and the ends of mains are dripped into the return through a special valve, same as is used on radiator returns; but if the building is less than seven stories high the drips at base of risers may be safely omitted. The return mains are usually not covered unless necessary for temperature control. It is not considered advisable to lift the water of condensation, but it can be done successfully if a separate return main is run for the low radiators. In the post office at New Orleans, La., the return main is at the first-floor ceiling and takes care of radiators about 9 feet below, and operates satisfactorily. The following sizes of steam and return mains are reliable for 64 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS vacuum systems. The quantities given are in square feet direct radiation per hour, and the distance is from the engine to the heater, one way: SUPPLY PIPING RETURN PIPING to O QJ IPs = 1 •"EH o ca^ Length of Supply Piping in Feet, from Source of Supply- to Farthest Radiator. Allowance for Elbows and Valves must be added to Measured Distance. Pipe Capacities in Square Feet of Direct Cast Iron Radiation given for each Length ■ St a 3 h W Jl S 100 200 400 600 1000 1500 2000 in. in. in. i 2 2 65 50 40 35 30 25 20 h 1 20 1 2 3 120 100 80 70 60 50 45 h 1 45 li 2 3 240 190 150 130 110 90 80 i 1 80 n 3 5 390 310 250 210 180 150 136 i 1 136 2 5 7 870 670 540 460 390 330 290 i 1 290 2i 6 9 1,600 1,250 1,000 870 740 620 550 3 1 550 3 9 14 2,590 2,040 1,650 1,430 1,210 1,020 900 1 1 900 3i 10 15 3,900 3,100 2,500 2,190 1,850 1,570 1,390 1 1 1,390 4 14 21 5,480 4,390 3,530 3,120 2,630 2,230 1,960 1 u 1,960 5 19 28 9,720 7,900 6,460 5,680 4,810 4,110 3,630 U li 2,710 6 24 36 12,870 10.680 9,390 7,980 6,720 5,740 n n 3,630 7 29 44 19,090 15,930 14,120 12,040 10,290 9,130 u 5,740 8 35 53 26,910 22,680 20,180 17,120 14,330 12,720 2 9,130 g 41 61 35,580 30,170 26,920 23,160 19,790 17,380 2 12,720 10 47 70 46,710 40,050 35,860 30,890 26,540 23,610 2 17,380 12 59 88 73,210 63,870 57,660 49,950 43,080 38,400 2J 23,610 14 71 106 86,400 75,430 65,310 68,290 ■Jl 38,400 IS 85,770 71,910 3 68,290 3 71,910 When blast coils are on the system, the equivalent direct radia- tion equals the total B.t.u. per hour put into the air, divided by 250. Pumps. Sizes of vacuum pumps for vacuum systems may be found as follows : "Factor" equals 100 times the number of water- seal motor valves plus the actual square feet of direct radiation. In case of indirect radiation, or blast coils, reduce the radiation to equivalent direct surface by multiplying the actual square feet by the B.t.u. condensation per hour and dividing the pro- duct by, 250 (the usual condensation of direct radiation in B.t.u. per square foot per hour). After the "factor" is found refer to the following table and choose the pump corresponding to the "Factor." HEATING AND VENTILATION 65 In the table make the steam, exhaust, and discharge pipes the size given. Make the suction the size of the main return and bush at the pump to size given. All pumps are single-cylinder double-acting. SIZE OF PTJMP STEAM "WATER STROKE STEAM EXHAUST SUCTION DISCHAKGE FACTOR FLOOR SPACE inches 4x4x6 inches inches inches inches 6,830 7,270 8,000 10,680 11,350 12,500 15,125 15,390 17,215 18,000 19,390 28,250 30,600 34,410 36,620 43,627 48,957 57,220 60,250 82,397 90,713 122,500 133,000 161,270 173,720 219,870 233,640 271,440 inches 4x4x6 4x4x8 4x5x5 f 3 8 i 1 2 24 24 2 2 11 x34 11 x34 4x5x6 4x5x8 4fx 6Jx 8 4J X 6 X 5 4i X 6 X 7 3 8 3 8 1 2 4 i 3 4 3 3 3 24 24 24 13x36 13x38 13x38 4ix 6 X 8 5 X 6 xlO 7 X 7ixlO 6 X 7}xl0 7 X 8 xlO 6 X 8 xl2 fi Tc Q X 10 1 2 3 4 1 3 I 1 i 1 1 li 1 3 4 5 5 5 5 24 3 4 4 4 4 13x38 18x50 18x52 19x54 18x52 19x54 8 X 9ixl2 8 xlO xl2 8 xlO xl4 10 xl2 xl2 10 xlO xl6 10 xl4 xl6 12 xl4 x20 12 xl6 xl6 14 xl6 x20 16 xl8 x20 16 xl8 x24 18 x20 x20 1 1 6 6 5 5 20x58 20x58 li u 6 5 20x62 U 2 10 8 2 2i 2i 3 12 12 10 10 3 34 14 12 In the foregoing table the steam cylinders of the pumps are pro- portioned for about 100 pounds steam pressure. Pressures dif- fering materially from this would require proportionally different steam cylinders. Capacity of the automatic return valves: 66 MECHANICAL EQUIPMENT OF FEDEEAL BUILDINGS One-half inch diameter, 80 pounds water per hour = 265 square feet direct radiation. Three-quarter inch diameter, 400 pounds water per hour = 1330 square feet direct radiation. One inch diameter, 800 pounds water per hour = 2660 square feet direct radiation. The office does not adopt the practice of running a separate return system to take care of the drips from risers and mains. No horizontal branch, either stream or return, is made less than I inch. It is especially important to observe this if branch is to be buried in floor construction. All special attachments necessary for the operation of the ap- paratus are required to be furnished by the contractor when a vacuum system is used by the office. The specification for such a system must, of course, be some- what general to permit free competition. MECHANICAL SYSTEMS OF AIR REMOVAL These systems are sometimes installed in the larger buildings where automatic temperature control is used, or in buildings where outside steam service operating on an atmospheric system is to be used. In the latter cases it has been found that the me- chanical air-removal systems are usually acceptable to the dis- trict service companies. The office does not often use an atmos- pheric system. The steam and return piping is laid out in exactly the same manner and with the same sizes as for a 1-pipe gravity-return system, and all connections are made in the usual way. The exhausting apparatus for plants less than 2500 square feet direct radiation, or its equivalent in indirect, is a water-operated vacuum pump. The water pressure should be over 20 pounds per square inch to insure satisfactory operation. In larger systems where high-pressure steam is made, a steam jet is used to induce a partial vacuum in the air lines. Velocity of steam at jet should be about 900 feet per second. In systems above 2500 square feet where no high-pressure steam is made a small vacuum pump driven by an electric motor is used. HEATING AND VENTILATION 67 The motor has an automatic regulating device, and if water or steam is used there should be an automatic control valve so arranged as to carry constant vacuum on the air lines. The discharge line from the ejector or pump is discharged over a cesspool or some such receptacle. Care must be taken in the grading of the air lines to insure that no pockets are sealed with condensed vapor. Each rising air line should have a gate valve. In this class of systems, and also in the larger installations of the mechainical vacuum type, it is the practice of the office to di- vide the radiation into groups and to bring the air lines and va- cuum return lines back separately, valving each at the pump or ejector. Proper adjustment of these valves will overcome the "robbing" of one group by another. The steam mains to the respective groups should be valved to correspond, if possible, but these valves need not be centrally located as in case of the valves on returns. The amount of steam used by the ejector varies widely, some authorities reporting as little as one-tenth of 1 per cent, and others as much as 5 per cent of the total amount of steam condensed. The following is a sample specification (all material and labor included) for attaching an air-removal system to a system of di- rect radiation where the radiation exceeds 2500 square feet and no high-pressure steam is available. SPECIFICATION Air-removal system. Furnish and install an automatic me- chanical air-removal system in connection with the heating sys- tem of the building. For this purpose an electric-driven air exhauster is to be fur- nished and installed in suitable manner on concrete foundation with cast-iron bedplate. The motor is to be direct connected to air exhauster or to drive same by means of silent chain or spur gear running in oil bath, or by suitable leather belt. Motor to be of proper size and speed and wound for — volts, — current. Motor must conform to specification for motors in general in another part of this specification. There must be an automatic governor designed to start and stop motor to maintain a constant predetermined vacuum on air 68 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS lines. A storage tank and separator which will automatically discharge any condensation to waste pipe must be provided on air line near pump. The air exhauster must have a capacity suf- ficient to keep the entire system free from air and to maintain any desired vacuum in the system between 6 and 12 inches. Output of motor at full load must not be more than — brake horsepower. Air valves, air lines, etc. All direct radiators, the ends of all steam mains, and the return from coil in hot-water tank are to be fitted with approved automatic type air valves of the highest grade specially designed for air-exhausting systems. Air valves to be nickel plated, provided with union couplings, and not less than |-inch pipe connection. To have all metal thermostatic ele- ments, no carbon post valve is acceptable. Piping in connection with air-removal system is not indicated on drawings. Contractor must run same as direct as possible and follow runs of steam mains in basement. Horizontal runs from air valves to be run in floor construction to risers or at ceiling below to mains, same as steam piping. Pipe sizes to be not less than the following: Vertical connection to air valves j-inch di- ameter; horizontal branches from air valves to risers or mains f inch; risers | inch and mains in basement 1 inch diameter unless otherwise shown on drawing. All pipes to be galvanized wrought iron or galvanized mild steel and all fittings to be galvanized cast iron. Ends of all pip- ing to be reamed after cutting. All joints to be made up with asphaltum. Gate valves to conform with valves on steam piping to be placed on mains and riser connections in basement. The dis- charge from exhauster is to terminate over cesspool located near exhauster. Hangers, tubes, floor, and ceiling plates to be as specified for steam pipes. Air lines are not to be covered. Exposed air piping above base- ment is to be painted as specified for steam piping. Air piping in basement is to be painted same as other galvanized pipe. Test of air lines. All air piping run in chases, furred spaces, or floor construction must be tested in the presence of the super- intendent to a hydrostatic pressure of 80 pounds to the square inch and proved tight under this pressure before same is concealed. HEATING AND VENTILATION 69 On completion of the heating system the entire air-removal sys- tem is to be tested to a vacuum of 7 inches. This vacuum must be obtained by the pump, the pump is then to be stopped, and the vacuum must be maintained for one hour without showing a decrease of more than 2 inches. During test of air lines all communication between air lines and steam piping must be closed, but hand valves at pump must remain open. Painting. Exhauster, motor, tank, etc., to be filled and rubbed at factory and after erection painted two coats lead and oil paint tinted as directed by superintendent. ESTIMATING DATA FOR HEATING AND VENTILATING APPARATUS IN NEW FEDERAL BUILDINGS Cost of boiler. Take off 50 per cent from price list Kewanee Boiler Com- pany's "Fire box." Labor to install and test steel boiler 150 ,00 Foundations, brickwork for boiler and pit in place, per M 20.00 Foundations, concrete for boiler and pit, per cubic yard. . 8.00 Stone coping for boiler pit per cubic foot, in place 4.00 Breeching and stack in place, per pound .08 or per foot, 4.00 Cast-iron base plate for stack, per pound 0.03 Direct steam radiators (all heights) set in place, but not connected per square foot .20 Painting and enameling, per square foot of radiator 0.03 Highest grade radiator valves and air valves (steam), per radiator 3 .50 Highest grade radiator valves and air valves (water) per radiator (two regular steam type radiator valves are used on each hot water radiator) 4 .50 Air valves at ends of steam mains in place, each 12.00 Labor on one-pipe steam jobs, per radiator exclusive of boiler and breeching 6 .60 Labor on two-pipe hot water jobs, per radiator exclusive of boiler and breeching 800 Freight and drayage, 3 per cent total cost of boiler, radia- tors, pipe, and fittings. Superintendence, 1 per cent cost of labor and material. Nonconducting covering for pipes and fittings, per square foot of radiation (this also includes the boiler and breech- ing covering) 0. Pipe and fittings, one-pipe steam, per radiator 7.00 Pipe and fittings, two-pipe hot water, per radiator 10.00 70 MECHANICAL EQUIPMENT OF FEDEBAL BUILDINGS Return pipe trench and cover complete in place, per lineal foot $1 .50 Blow-off pot with pipe and valves in place 35 .00 Forty-gallon expansion tank in place with pipe 25.00 Thermometers in place, each 1 .00 Sylphon damper regulator in place (water) 20.00 Board and lodging for men, per day 3.00 Railroad fare for Federal jobs, average conditions 50.00 Profit, 20 per cent. Cast iron blowoff pots in place exclusive of blowoff valve, sewer connection, and vapor vent pipe. Size Price Size Price 18x24 $20.00 30x42 $51.00 18x30 23.00 30x48 57.00 18x36 26.00 36x36 53.00 24x30 31.00 36x42 59.00 24x36 37.00 36x48 65.00 24x42 41.00 42x42 67.00 30x30 39.00 42x48 73.00 30x36 45.00 42x54 79.00 The following table gives cost in place of pipe, fittings, etc., for low pressure heating work. Cost of threads is included in cost of pipe in place. Cost of floor and wall sleeves and hangers includes cost of cutting in ordinary fire proof construction. All pipe and fittings are black and screwed unless otherwise stated and are standard weight for 125 pounds pressure. Prices for flanged work includes bolts and rubber gaskets suitable for low pressure. Radiator valves are the highest grade nickel plated rough bodies and finished trimmings. o ] >-l IM 05 ^ 10 00 iO to CO OJ CO CM 1— 1 r-l rl< 00 CO in T-H 1— I CO 00 rH CO CO CM t^ CO (— > CO T-H i-H CO CO Oi ^0 10 10 00 ■ • rH CO 00 CO OS 00 10 Th CO cq (M O) ^ CO to <-> 10 IC CO ^ =" o> CO T-H CO 10 CO (N (M ^ CM CM T— t T— 1 CO r^ (-1 in 10 "5 • 1-1 (M CO CO 1-H OJ 'l* (N cq I-H tH CM T-H 1-H 1-1 h- 10 10 r-1 »o ^ ■* to t^ 10 CM CO t^ CO 1-1 ■-1 l> I>- T-H T-H K5 10 m 10 (-1 lO lO Hn CO 00 CO • CO TjH -* 00 CO 10 CM --^ .-1 CO 10 T-H T-H Oi IC (N 10 10 f-1 CO •o "T^ CM -^ ^ lO ■* T-H T-H >0 t-- rq >o in r-) <- fT 10 -HiN (r r~ . CM T-H c*: ir t> rf C c^ CO t CM CM c c 1— ( ct CO ^ ^ c ) c > T-H ^ i> lO t- 10 ir (~> „ J cr > 10 «W S (N 't IM Tf CO t_ C c t— ( (N CM c^ c > c T-H (N C (T ^ 10 c: Of 1 ic ) ":■ rHl^ 1-H C^ (N 00 Ttl C^ c T-H T-H C C '" T-H OJ »-H c > c oc cr >r <-> r- 1- . Tt U5 lO T-H 1— t t— c^ t> cc i-H cc T-H < 05 T-H c c - T-H T— 1 c ) c > r- ^ c ^- . 0- ) WW 1— (M 10 t_ cc c •• ^ c C - C T-H c ) c J 00 IM rr ^ "T <- c r- - c ) lO rtiN T- -n oc tc ■* '- c c c c c > c ) 5 F- ^ : ^ t- ^-i 1^ B t/ ■*- a a 3 C 3 to ■ OJ — = -^ s 1 a > 1 > c a 1. i C ^ fc 3 CD ^1 3 t> ^ M PC "1 C a. p: 3 h cc i ^ bD e c3 a a 'p. o m 03 ;3 y3 tJO s CM g s 00 s 5 CO T-H CO CO § OJ CO lO 01 lO T-H g T-H CM CO 0: CO s 10 § lO CO 10 00 CM 10 T-H ?5 l> s CO CO 8 g § § ^ T-H 10 T-H 10 01 l-H cq ^ 10 00 CO T-H tH T-H CO lO 10 10 10 CO T-H CO CM T-H CM l-H s s T-H § K 1« 03 CO T-H 1—1 T-H CO U5 g s T-H 10 00 CM 02 a> to 2 bo q=l g q=l S 2 p. (3 S '^ O ft ° a th O 1 " o3 t3 ^ 03 o m a a OJ +3 o bc 5. a ffl bD bf) o d 03 O 'fcT'd la m O bO TJ d ■a q=l c/? l-l lU > r> (J a i> 0I i> Of S n 71 72 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS High grade automatic air valves in place $1.00 Check, safety and blow off valves in place. SIZE SWING CHECK VALVE LEVEB SAFETY VALVE ASBESTOS PACKED BLOWOFF COCKS (IKON) i 0.85 1.25 1.25 i 1.05 1.45 1.55 1 1.55 1.75 1.85 U 2.05 2.60 2.55 li 2.90 3.30 3.50 2 4.20 4.50 7.00 2i 5.05 4.75 8.45 3 6.85 6.35 12,60 34 8.20 8.40 18.75 4 9.85 10.50 21.00 For handling fans and heating coils and placing on foun- dation, allow for labor, per ton $12.00 Standard galvanized-iron air washer complete in place, exclusive of freight and foundation. Capacity per minute, cubic feet. 15,000 $900.00 20,000 1050.00 25,000 1250.00 30,000 1500.00 40,000 2000.00 Air washer complete, including air-washer pump and motor complete, f.o.b. factory, per 1,000 cubic feet of air capacity specified $45 .00 Erection (average) 100 .00 Freight and drayage (average) 100.00 Brickwork in cement, per M in place 20 .00 Trench plates in place, fitted and painted, per pound... 0.05 High-pressure all-steel water-tube boilers, Government specification, and tested complete in place and set, but no pipe work or breeching, per H.P 20.00 Feed water heaters in place on foundation, no pipe work, per H.P 1 .50 Boiler feed pump, 6-inch x 4-inch x 6-inch, with drip pan, brass fitted, in place on foundation, no pipe work 150.00 Nonconducting covering in place, with solid brass bands and painted two coats fireproof paint, take 50 per cent off the 85 per cent magnesia list. This will aver- age per square feet radiation 0.10 HEATING AND VENTILATION 73 Covering on boiler and breeching, per square foot, in Pla'Ce $0.20 One hundred pound pressure, standard design, horizontal return-tubular boilers, with all castings, will average f.o.b. factory the following prices: r^-S?''/"" , P'*' setting and founda- Inclies feet Price tion in place 42 X 12, without down draft furnace. $300 . 00 $300 . 00 48 X 12, without down draft furnace . 350 . 00 350 . 00 48x14, without down draft furnace. 400.00 400.00 54x16, without down draft furnace. 475.00 450.00 60x16, without down draft furnace. 600.00 500.00 72x18, without down draft furnace. 850.00 650.00 To get freight, take square feet of radiation at 10 pounds which will cover weight of radiation, pipe, fittings, etc. When estimating on freight call 5,000 square feet of direct radiation a car-load, and 36,000 pounds of pipe a car-load. Take freight on Government job at 10.20 per 100 pounds and drayage at $3.00 per ton. Galvanized ducts, etc., in place, per pound 0.12 Registers, take 60 per cent off Tuttle and Bailey's list. Special valves on return ends of radiators, the receiving tank, the automatic vacuum and relief valves on re- ceiving tank of atmospheric systems such as the "Dun- ham," per radiator 10.00 This figure is about correct for the Webster Modulation system and the Thermograde system, and should also cover the cost of all so-called "Vapor" systems. For placing registers, each, add 1 .00 Labor erecting ordinary indirect stack, each 5.00 Cast-iron pin indirect, delivered in basement, per square foot 0.20 Blast coils, per lineal foot in place on foundations, exclu- sive of freight 0.12 (To get weight multiply lineal foot by 3.) Engine and fan foundations in place, including excava- tion, per cubic yard 8 .00 Full housed steel-plated fans in place on foundation, exclusive of motors and belts: 3 feet inch diameter wheel 130.00 4 feet inch diameter wheel 185 .00 5 feet inch diameter wheel 250 .00 6 feet inch diameter wheel 325.00 74 MECHANICAL EQUIPMENT OP FEDERAL BUILDINGS 7 feet inch diameter wheel $430 .00 8 feet inch diameter wheel 565 .00 9 feet inch diameter wheel 710 .00 10 feet inch diameter wheel 930.00 In estimating the cost of vacuum systems it will be safe to as- sume for the average Federal building that each vacuum pump on its foundation, complete with governor and suction strainer, will cost $350, as the size will average 10 inches x 12 inches X 12 inches. Take the special valves on return end of radiators and at drip points in piping at |6 each in place. This allows for valve and return piping. For air line systems allow $5 per radiator for air valve and air piping. Electric air exhauster, including separator and auto- matic vacuum governor, $400 in place. Water-operated exhausters cost $150 each. In estimating cost of first-class automatic temperature-control systems, allow $15 for each thermostat, $20 for each damper con- trolled, and $10 for each steam or water valve controlled. Allow $250 for an electric driven compressor and $75 for a water oper- ated compressor. For humidity control exclusive of water heater allow $200. A hydraulic pump will handle fifty thermostats if necessary, but in the larger jobs an electrically-operated air compressor is used. A hydraulic air exhauster is used on "Paul" systems with 2000 square feet direct surface; above that, electrical or steam exhaust- ers are used. Especial attention is called to the fact that the foregoing figures are correct for certain special conditions in new Federal buildings, but are not applicable under all conditions. Used with judg- ment, they give accurate results. CHAPTER II COMMERCIAL PRACTICE IN REGARD TO HEATING FACTORY AND OTHER BUILDINGS While the following two chapters are not strictly appHcable to Federal buildings, they are incorporated herein as containing much valuable information of general interest. The papers were written by heating and ventilating engineers in the office of the Supervising Architect, the first by Mr. H. C. Russell and the second by Mr. Leon A. Warren, who are specially qualified to treat of their respective subjects, the former by reason of several years' employment with one of the leading fan manu- facturers, and the latter through his connection with a firm specializing in the forced hot-water system of heating. FACTORY HEATING [Note : Most of the calculations in this paper were made on a slide rule, which accounts for insignificant arithmetical errors. References will frequently be made to the section of this book which treats of the heating and ventilation of Federal buildings, and to curves and tables which will be found in the back of the book.] Systems in use. Practically there are only two systems for heating factory buildings, i.e., the fan system, and direct steam or hot water, each having its various modifications. The fan system as a general rule has the following advantages : Great flexibility, in that air can be cut off from unexposed por- tions of a building and a large part of it forced to the more exposed portions: absence of leak pipes overhead; less liabihty of freezing affords positive ventilation; the humidity of the air inside the building can be controlled; and lower steam pressure is required to maintain circulation, which is an important consideration if exhaust steam is used for heating without a vacuum system. Direct radiation has certain advantages in places where a fan might stir up dust to settle upon freshly painted or varnished surfaces. 75 76 MECHANICAL EQUIPMENT OP FEDERAL BUILDINGS FAN SYSTEM Apparatus. The apparatus usually consists of a fan to circu- late the air, a prime mover to drive the fan, a heater to heat the air, and a set of distributing ducts to carry the hot air to the de- sired points. Air washers are seldom used except where food products are handled, or where there are special considerations, such as humidity control, etc. Fans. Centrifugal fans are usually employed, although the disc fan is used in small buildings where the ducts are very short. The ordinary type of centrifugal fan is known as the "steel plate" fan. It usually has 8 blades. The capacity of fan is expressed in cubic feet of air per minute handled by the fan. The conditions under which a fan works must be known, because they have a preponderating influence upon its performance. Tests by the writer, coupled with data from various sources indicate the formula given below when proportions of fans are as hereinbefore stated for 8-blade fans. Capacity. C.F.M. = 0.44DW, as a formula for ordinary factory heating. C.F.M. = cubic feet air handled per minute by the fan. D = diameter of wheel in feet. N = revolutions of wheel per minute. Power required. B.H.P. = 12 500 000 ' ^°^ average factory heatmg. Symbols same as before, except S, which equals 1.00 for air handled at 0°, and for any other temperature as t — ■ i S^.: 460 460 + 1! If T should be below 0° it would of course be considered negative. The B.H.P. is the power actually applied to the fan shaft. The above formula for power is for a wheel about 6-foot diame- ter. For smaller wheels add 5 per cent for each one foot differ- ence in diameter. Sirocco fans. The proportions of these fans have been pre- viously stated. The capacity and power for ordinary factory COMMERCIAL PRACTICE IN REGARD TO HEATING BUILDINGS 77 heating are as follows, the symbols being the same as used here- tofore : C.F.M. = I.IODW. B.H.P. = 2,250,000 A test of an 8-foot multiblade fan showed that the fan deliv- ered 75,600 C.F.M. at 149 R.P.M. against a static pressure on the outlet of 1.11 inches of water (inlet free), with a B.H.P. equal to 33.9, at 74° temperature and barometer at 29.76. In this case the outlet was 64 inches x 64 inches instead of the standard size used by the manufacturer. The above formulae for capacity and power given for heating work are based on having a set of discharge ducts which shall equal- ize to the standard fan outlet (not blast areas, which is usually about 40 per cent of the area of fan outlet), as explained here- after. Or, to put it in another form, the formulae are correct when the pressure due to the velocity of air at the fan outlet is about 40 per cent of the total friction losses in the heater and ducts. Double-inlet fans. Double-inlet fans are not often used in factory work, as single-inlet fans usually make a more compact outfit. Cone fans. These fans have a large field of usefulness in heat- ing and ventilating work where the power must be reduced to a minimum. They require large ducts and much floor space and are seldom used in factories. The reason for the low power consumption is that in the case of a steel plate fan the air is taken from the periphery of the wheel by means of a scroll, the outlet of which must be relatively small to prevent a so-called "back-lash" of air, resulting in a high velocity of air through this outlet. If large ducts are used this velocity will be reduced and a great part of the pressure in the fan, required to produce this high velocity in the beginning, will be lost. In the case of the cone fan this high velocity is never produced, as the inlet, which represents the highest velocity, is usually about 50 per cent greater in area than the inlet or outlet of a steel plate fan which would be selected to do the same work. However, a steel plate fan of which the standard outlet equals the area of the discharge ducts will handle the air with less power 78 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS than a cone fan, because its true mechanical efficiency is higher than that of a cone fan. The following formulae apply to cone fans : C.F.M. = 4:8DW. B.H.P = 14,000,000 Care should be exercised in every detail of cone fan installations. The combined area of the air ducts should not be less than the dis- charge area of the wheel, i.e., the circumference times width of periphery, and the free area of the heater should be about the same as the area of air ducts. The following facts have been determined both theoretically and practically for all kinds of centrifugal fans : The C.F.M. varies directly as the speed; the pressure varies directly as the square of the speed; and the brake horse-power varies directly as the cube of the speed. The above are true, of course, only so long as conditions of the inlet and outlet resistance are maintained the same. The indicated horse-power of the prime mover may vary about as the square of the speed, depending upon the kind of prime mover used; but this discrepancy is due to a change in the efficiency of the prime mover at different loads. The power actu- ally applied at the fan shaft will vary exactly as the cube of the speed. At the same speed as the resistance is inserted in the inlet or outlet, as by the closing of a damper, the capacity and power will decrease and the pressure will increase. The "blast area" of a fan is the area of discharge opening over which the fan will maintain a dynamic pressure equal to the pres- sure corresponding to the peripheral velocity of the fan tips. When this area is increased the pressure will decrease, and vice versa. Many authorities state that the pressure does not in- crease on reduction of the area of discharge below blast area, but the writer has always found that it does with 8-blade fans. The blast area need not be considered in ordinary heating or ventilating work, as the restriction should never be great enough to cut the effective area of discharge down to blast area, which is about 40 per cent of the area of fan outlet, as previously stated. COMMEECIAL PRACTICE IN REGARD TO HEATING BUILDINGS 79 DISC FANS In this type of fan much depends upon the number of blades, their angle, whether straight or curved, etc. Disc fan outfits are uniformly constructed as "blow through" type. In small build- ings these fans will give satisfaction for heating, but a large mar- gin of safety must be allowed, as their operation is materially affected by many apparently trifling things. For fans with about twelve blades the following formulae may be used : C.F.M. = ADm. B.H.P. = C All symbols are the same as previously given except A and C, which are as follows : Case I. Free inlet and delivery, as a fan set in a window to supply air or to exhaust from a large room. Case II. Delivering or exhausting air through not more than the equivalent of 100 feet of straight pipe the diameter of the fan. Case III. Delivering air through same amount of piping and a heater not more than 20 pipes deep and with velocity through heater not over 1000 feet per minute. STRAIGHT-BLADE DISC FAN "A" "C" Case 1 0.70 42,500,000,000 Case II 0.60 33,000,000,000 Case III 0.50 27,000,000,000 PROPELLER TYPE "A" "C" Case 1 0.85 46,000,000,000 Case II 0.65 40,000,000,000 In Case II the peripheral velocity of wheel should be not less than 5000 feet per minute, and in Case III not less than 7500 feet. The free area of the heater should not be less than the area of the fan, and the main air duct about equal to free area of the heater. 80 MECHANICAL EQUIPMENT OF FEDEBAL BUILDINGS With the same fan and the same conditions as to inlet and out- let, the capacity, pressure, and power vary in the. same manner as given for steel plate fans of the centrifugal type; but when a disc fan is running at a set speed and the inlet or outlet is re- stricted (as by the closing of a damper) the power will increase, which is just the reverse of what happened with a steel plate fan. The increase is so rapid that it is perfectly possible for the fan to take three times as much power with the damper fully closed as it would with the damper fully open. An engine on this increased load would slow down without damage, but a motor not protected by some kind of overload-release would be burned up in short order. This feature therefore requires care, especially in connection with motor-driven fans. In the case of some of the curved-blade disc or propeller fans the increase of power with the insertion of resistance would not be so noticeable, as such fans have to some extent the properties of centrifugal fans. HEATING COILS Heaters used for steam are usually the cast-iron sectional-base type, with heating surface composed of 1-inch wrought-iron pipe, or the all cast-iron heaters such as the "Vento" made by the American Radiator Company. In some makes of the sectional-base type the base is divided into two compartments by a horizontal partition, one compart- ment being for steam and the other for condensation. This par- tition may be solid, or water seal inside the base may connect the two chahabers. In the former case, which is the preferable arrangement, a third connection called the bleeder is necessary to take care of the water of condensation which drains back into the steam compartment. If pipe coils are to be used mitre type coils are always preferable on account of the less liability of air binding. In some cases a plain box base is used which has no interior partitions of any kind. The data given in a preceding chapter on heating and ventila- tion, give all data required as to temperature rise, condensation, friction, etc. For factory work the velocity through the heater is usually about 1200 feet per minute, and the heater 20 to 24 pipes deep. COMMERCIAL PRACTICE IN REGARD TO HEATING BUILDINGS 81 Tappings. For exhaust or low-pressure steam with gravity returns the tapping of the base should be as follows : POUNDS STEAM PER HOUR PER SECTION STEAM TAP DHIP TAP BLEEDER TAP 80 inches 2 2i 3 34 4 inches li 1* 2 2i 2i inches 3 4 3 160 320.... li li li 480... 950 The standard "Vento" tapping is 2| inches for steam and re- turn, but 3 inches or 3| inches tappings for the feed sections may- be obtained on special order. The "Vento" has, of course, no bleeder connection. The drip connection should be one-half the diameter of steam connection plus 1-pipe size. The writer has seen successful installations in which the quan- tities of steam supplied by tappings were almost double those given above. If the mains are short and the water line is 3 feet or more below the coils the quantities may be increased 25 per cent; and another 25 per cent may be added if the coil are "Vento" or "top feed." Steam and return piping. The steam pipe is usually carried overhead from a convenient point on the exhaust line or from the boiler. The return is usually carried in a pipe trench discharg- ing into a pot trap, a hot well, a feed pump and receiver, or a return trap. Sometimes it is wastefully trapped into the sewer. For gravity work the writer uses D'Arcy's formula, which when simphfied for steam entering at 5 pounds pressure is D=:^: KP when D = diameter of pipe in inches. L = length of pipe in feet. W = pounds steam per minute. P = loss of pressure allowed, usually taken as 1 pound per 300 feet of steam travel. K = a. constant varying with the size of pipe as follows: 82 MECHANICAL EQUIPMENT OP FEDERAL BUILDINGS Diameter (inches) 1 2 3 4 5 6 7 8 K equals 104 140 160 169 173 170 183 187 For steam above 30 pounds pressure, make steam main one- half of the diameter given above; between 15 pounds and 30 pounds make diameter two-thirds that given by the formula; below 15 pounds same as given by formula. Return main one-half diameter of steam main plus 1 pipe size and make it "wet." As a rough rule the bottom of the coil should never be less than 2 feet above the water line in receiver, pump governor, trap, or whatever is used. High and low pressure steam. Most authorities agree that pressure on coils should not be over 5 pounds for best circulation. Arrangements should always be made to use live steam through a pressure-reducing valve to supply the heaters when the main engines which normally supply the exhaust steam are not running. PRIME MOVERS Engines are quite generally used in factory work. They are usually direct-connected to the fan without fly wheel or governor, as the fan wheel is a good fly wheel and prevents the engine from speeding because the power required increases so rapidly as the speed increases. Vertical engines are generally used except the very largest fans. On the direct-connected or flxed-eccentric engines, most makers set the cut-off at 50 per cent, but in figuring for sizes the cut-off should be taken as about 5-16. If exhaust or low-pressure steam is used in the coils the fan engine exhaust should be connected through an oil separator into the low-pressure main. If steam at high pressure is used in the coils the fan-engine exhaust is usually connected through an oil separator into a separate section of the heater-coil, usually the outside section. This section would of course have to have sepa- rate return trap, etc., from the sections on high pressure. No engine exhaust should be connected to a heating system with- out a back pressure valve at a convenient point on the exhaust line to regulate the back pressure carried on the engine. If motors are used they should be direct-connected to the fan when the speed is high enough to warrant it. COMMERCIAL PRACTICE IN REGARD TO HEATING BUILDINGS 83 Flange couplings are quite generally used for both engines and motors, although some forms of flexible coupling is often used, and sometimes where heavy loads are to be carried the fan and prime mover shaft is in one piece. Belts. Belts should have the "pulling" side on the bottom if possible. The horse-power transmitted per inch of width by a leather belt J inch thick at various speeds is as follows : Velocity in feet per second Horse-power 10 0.84 20 1.75 30 2.58 40 3.32 50 3,98 60 4.51 70 4.91 80 5.15 90 5.20 For other commercial thicknesses of belt the horse-power trans- mitted varies directly as the thickness, but the maximum velocity for any belt for good operation may be considered as 90 feet per second. Pulley centers should be preferably 10 or 20 feet apart, depend- ing upon relative sizes of pulley. Long slow-moving belts give best service. Centers less than 8 feet apart will seldom be satis- factory. Chain-drives. For short centers and considerable reductions in speed some of the patented chain-drives give good results, al- though they are not always entirely noiseless. Sprockets should generally not be more than 4 feet apart. Gears, etc. Occasionally back-geared motors are resorted to, but gears should be avoided where possible. Humidifiers. In textile mills and certain other kinds of fac- tories the humidity of the air must be under absolute control. This can best be accomplished by an air washer and humidifier. In one well-known system the air is first drawn through a spray- type air washer and eliminator. The water supplied to the washer is heated, the temperature of this heated water being controlled automatically by a special controlling apparatus. 84 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS The conditioning of air for textile mills as regards its relative humidity has been reduced to a science. When such problems are encountered it is best to obtain the advice of some of the reliable firms which manufacture such apparatus and guarantee results. Spinners have found that the cost of installation and operation of the best humidifying apparatus is small compared with the consequent profits in better yarns and the reduced loss in manu- facture. In factories where the humidity control need ncft be so exact, some of the simpler and cheaper devices may answer the pur- pose. When designing fans, etc., for this kind of work it is important to remember that the weight of air per cubic foot decreases very markedly as the point of saturation is approached. Any engi- neer's handbook will give the necessary information. Ducts and flues. Ducts and flues are usually made of galvan- ized iron of the following gages: ROUND DUCTS To 15 inches dia. No. 26 U.S.S. gauge 16 inches to 30 inches dia. No. 24 U.S.S. gauge 31 inches to 42 inches dia. No. 22 U.S.S. gauge 43 inches to 54 inches dia. No. 20 U.S.S. gauge 55 inches to 72 inches dia. No. 18 U.S.S. gauge 73 inches and up No. 16 U.S.S. gauge RECTANGULAR DUCTS Up to 18 inches wide No. 26 U.S.S. gauge 19 inches to 26 inches wide No. 24 U.S.S. gauge 27 inches to 40 inches wide No. 22 U.S.S. gauge 41 inches to 72 inches wide No. 20 U.S.S. gauge 73 inches to 84 inches wide No. 18 U.S.S. gauge 85 inches and up No. 16 U.S.S. gauge By "wide" is meant the longest dimension No. 26 U.S.S. gauge weighs 0.91 pounds per square foot No. 24 U.S.S. gauge weighs 1.16 pounds per square foot No. 22 U.S.S. gauge weighs 1.41 pounds per square foot No. 20 U.S.S. gauge weighs 1.66 pounds per square foot No. 18 U.S.S. gauge weighs 2.16 pounds per square foot No. 16 U.S.S. gauge weighs 2.66 pounds per square foot In estimating weight allow 15 per cent for allowable over- weight, laps, and waste in the making, according to the simplicity of the work. COMMERCIAL PRACTICE IN REGARD TO HEATING BUILDINGS 85 Underground ducts when used are usually made of brick, built rectangular in shape, with arched top, and plastered smooth on the inside. Terra cotta sewer pipe is sometimes used. Vertical flues are usually made of galvanized iron, but in textile mills and the like they are usually built in the walls and plastered inside. Flues when built in outside walls should be, if possible, lined with fire-clay flue lining, which has some insulating qualities. Air outlets. When overhead ducts of galvanized iron are used an outlet is usually a branch taken from the main pipe and turned at such an angle as to discharge toward the wall at a point about 8 feet above the floor. Each outlet should be equipped with an adjustable spring damper controlled by a pair of jack-chains reaching to about 7 feet above the floor. When brick or tile vertical flues are used and so spaced (as is usually the case) as to require no branch piping, a screen or mill damper is used. Systems of distribution. This is the most difficult part of the work, where experience is at a premium and a knowledge of what has failed is worth even more than a Icnowledge of what has been successful. It is specially important to refrain from trying to make the air perform any unusual "stunts." Make it a general rule not to get over 30 feet from an exposed wall and not over 20 feet above the floor. This would apply to a one-story factory building with no ceiling, and say, a saw-tooth roof construction. Such a building up to 60 or 70 feet wide could be heated with one line of piping in the center. From this up to about 150 feet wide the heating could probably be done with two lines. Under a smooth ceiling air blown from an outlet toward an ex- posed wall, even with a low velocity, will heat evenly from 50 to 150 feet away, depending on conditions, chief among which is the location of the foul-air outlet, which should be at the floor line on the same side of the room as the hot-air inlet. Usually the foul-air or vent ducts are omitted in factories, but many such buildings are tightly constructed and the heating will be more uniform if foul-air ducts are used. When air is to be re- circulated a system of openings for the return of air to the fan should be provided if necessary. Such openings should be ar- ranged to give a circulation of air in the rooms. 86 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS Care should be taken in regard to allowing for stair wells, ele- vators, etc., that might short circuit the air back to the fan. It often happens that apparatus must be on a platform some distance above the floor. In such cases when the air is to be re- circulated the discharge branches must be led down columns, etc., to about three feet above the floor, or a return circulating duct must be dropped from the inlet of the heater to about three or four feet above the floor; this duct to equal in area the free air space in the heater. One or the other or both of these things must be done, otherwise the air will circulate around the top of the building and never reach the breathing line. If both are done it may be possible to keep the breathing line warmer than the roof trusses. Cone connections. The fan inlet is usually connected to the heater casing by a "cone;" a "collar" should never be used. Plenty of room must be allowed between the fan inlet and the heater, and as a rule no part of the connection must be allowed to form an angle of less than 60 degrees with the side of the fan. If this is not observed a considerable portion of the heater may be "dead." Heat losses. The following heat losses have been extensively used with good results. They will be found somewhat higher than those applicable to Federal buildings on account of the uni- formly inferior construction of factory buildings. The losses given are B.t.u. per square foot per hour per de- gree of difference in temperature inside and outside. VARIOUS WALL SURFACES 4-inch brick .68 8-iiich brick 0.46 12-inoh brick 0.33 le-inch brick 0.27 20-inch brick 0.23 24-inch brick 0.20 28-inoh brick 0.18 32-inch brick 0.16 36-inch brick 0.15 40-inch brick 0.13 Above is for brick walls not plastered. COMMERCIAL PRACTICE IN REGARD TO HEATING BUILDINGS 87 Heat loss through concrete walls, as given by Mr. W. W. Ma- con in Metal Worker, March 11, 1911, is as follows: 2-inch concrete _. 0.69* 4-inch concrete 0.55* 6-inch concrete 0.47* 8-inch concrete . 49 10-inch concrete 0.35* 12-inch concrete 0.43* 16-inch concrete 0.37 20-inch concrete 0.33 24-inch concrete .30 28-inch concrete 0.27 32-inch concrete 0.25 36-inch concrete 0.23 Those marked * are ascribed by Mr. W. W. Macon to Prof. Rietschel, and for ordinary construction should be increased 25 per cent at least. Unlined corrugated iron or metal 0.84 Corrugated iron or metal over t. and g. boards 0.17 For roof surfaces : Unlined slate 0.82 Slate over t. and g. boards 0.30 Unlined metal 1 . 30 Iron over t. and g. boards . 17 Patent roof (tar, gravel, etc.) over t. and g. boards 0.30 For floors: Concrete on ground . 30 Wood close to ground 0.10 Dirt 0.23 For glass: Single window 1-20 Single skylight 1 . 50 Single monitor : 1 40 Double window 0.56 Double skylight 0.62 88 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS All the above are for south exposure. Add as follows: 10 per cent to the north, east, and west exposure; 10 per cent to the total exposure in addition to this if heated in daytime only; 30 per cent to the total exposure in addition to the first if heated in day- time only and unusually exposed; 50 per cent to the total exposure in addition to the first named if heated only at long intervals. The loss of heat from galvanized ducts carrying hot air can be determined by the formula ti ~ 'k = 50 S{U - U)r when V^ ti = temperature of air entering duct. h = temperature of air leaving duct. U = temperature of air outside of duct. S = square feet of surface of duct exposed. C = cubic feet of air per hour passing through duct. C{U - U) The B.t.u. lost per hour = 55 MECHANICAL VACUUM SYSTEMS These systems are often used on the larger heating installations in factories. They are able to reduce the back-pressure on the engine to little above atmospheric pressure by removing air and condensation by means of a vacuum pump attached to the return lines. MECHANICAL AIK-REMOVAL SYSTEMS These systems are often used in factory work. They are able to carry the back pressure on the engines slightly above atmos- pheric pressure in that they keep the air removed from the sys- tem. It may be well to call attention to the fact that with any of the vacuum or air removal systems there will always be a back-pres- sure on the engines equal to the friction head of the steam in the mains; but when the air is quickly and effectively disposed of this friction head is comparatively small. Example. Let us assume the data for an imaginary building and go through the various steps in the design of a factory heating system. COMMERCIAL PRACTICE IN REGARD TO HEATING BUILDINGS 89 Asstimed data: 32,100 square feet concrete floor. 12,250 square feeb wall glass. 6,200 square feet 12 inch brick wall. 5,400 square feet single skylight. 31,500 square feet tar and gravel roof. 710,000 cubic feet contents. Steam main 200 feet long. Return main 200 feet long. Recirculated air. Heat to 55° in 0° weather outside. Dimensions of huilding 321 feet x 100 feet x 22 feet. Calculations for exposure : Floor, 32,100 X 0.30 X 25 = 214,000 B.t.u. per hour. Glass, 12,500 X 1.2 X 55 = 805,000 B.t.u. per hour. Wall, 6,200 X 0.33 X 55 = 112,000 B.t.u. per hour. Skylight, 5,400 X 1.0 X 55 = 302,000 B.t.u. per hour, Roof, 31,500 X 0.30 X 55 = 520,000 B.t.u. per hour, Contents, 710,000 X 55 H- 55 = 710,000 B.t.u. per hour, Total = 2,689,000 B.t.u. per hour. Add 7.5 per cent for total exposures = 202,000 B.t.u. per hour. Add 10 per cent factor safety = 268,900 B.t.u. per hour. Total exposure = 3,159,000 B.t.u. per hour. Assumed temperature of air at outlets, 120°. 120° — 55° = 65° which is the drop in temperature of the air called "dif- fusion." 65° X .2375 (the specific heat of air at constant pres- sure) = 15.4 B.t.u. given off from each pound of air circulated, to heat the building. 3,159,900 -V- 15.4 = 205,000 pounds air per hour to be circu- lated by the fan. Allow about 10° drop of temperature in the ducts and if a "draw through" apparatus is used, as is always preferable, our fan will be handling air at 120° + 10°= 130°. 205,000 pounds per hour X 14.8 -=- 60 = 49,400 C.F.M. handled by the fan at 130°. 90 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS FAN REQUIRED Our formula for 8-blades fans is C.F.M. = 0.44 DW. The peripheral velocity in factory work with 8-blade fans is usually about 5600 feet per minute for factory work. Therefore N = 5,600 -i- tt D = 1,785 -v- D and C.F.M. = 0.44 X 1,785 D' = 786 D^ from which D2 = C.F.M. H- 786, substituting, we get D2 = 49,400 ^ 786 = 63 therefore D = V 63 = (say) 8 feet. N = 5,600 ^ TT D = 223 Revolutions per minute DWS _ {Sy X (223)3 X 0.89 _ ■ ■ ■ 12,500,000 12,500,000 ENGINE REQUIRED Assumed pressure at the throttle 80 pounds. A 10 x 12 engine at this pressure and at 223 R.P.M. will indicate about 32 H.P. Sirocco fan required. About 3500 feet per minute is the usual peripheral velocity with this style of fan in factory work. C.F.M.= 1.1 DW But N =5^ = 111^ from which is obtained C.F.M. = 1.10 DW = li^!^^ = 1220D^. C.F.M. _49400_ 1220 1220 ■ ■ D = V4L6 = 6| feet = 78 inches. ^. ^, C.F.M. 49400 T^-DTv/r J ^°"^=TlD^=LlX6:5-3 = ^-P-^-'""^ D^N'S _ (61)^ X (164)3 X 0.89 _ ■ ■ 2,250,000 2,250,000 Heater. As 205,000 pounds of air per hour are handled by the fan and raised from 55°, the temperature of the room, to 130°, COMMERCIAL PRACTICE IN REGARD TO HEATING BUILDINGS 91 the temperature at the outlet of the heater, this will require 205,000 X 75° X 0.2375 = 3.650,000 B.t.u. per hour. Heater. Reference to the data on "Vento" heaters will show that for 5 inch centers standard-depth section with air entering at 50° a 5-section depth heater would raise the air from 50° to 125° at a velocity of about 1400 feet per minute. This is practically equivalent to raising air from 55° to 130°, which was the required rise of temperature in the case cited. The air quantity, 205,000 205,000 pounds per hour, equals „ = 45,600 C.F.M. at 70 . (The Vento curves are based on air volumes, measured at 70°.) Now 45,600 -^ 1400 = 32.6 square feet free area in the heater. See table of free areas of Vento heaters and note that a heater 21 sections front, 50 inches high sections and two tiers high would have 16.13 X 2 = 32.25 square feet free area and 283J X 10 = 2830 square feet surface. Steam and return piping. 3,650,000 ^ 965 (the latent heat of steam at low pressure) = 3800 pounds of steam per hour. The formula for steam mains was : D= J- Kp Substituting L = 200 feet, Tf = 63 pounds (steam per minute), and p = 0.67 pounds, and trying first K = 180, which is assum- ing for trial that D will come 6 inches : D= U 180 X 0.67 For a vacuum system a main 200 feet long to carry 3800 pounds of steam per hour should be 7 inches diameter. 3800 pounds steam per hour -i- 5 sections = 760 pounds per hour with pipe coil for each section and 3800 ^ 10 = 380 pounds steam per hour with the "Vento" coil, for each group. Referring to gravity work the steam connection to each section of 4-row pipe coil should be 4 inches and the connection to each group of "Vento" coil should be 3f inches diameter. If in the pipe coil 92 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS the style of section having a "bleeder" connection to the base i used use a 2| inch diameter drip and IJ inch diameter bleeder fo gravity : Vacuum pump. 3,650,000 -f- 250 = 14,600 square feet equiva- lent direct radiating surface. 3800 pounds h- 400 = 10 — | inch water-seal motor valves. The "pump factor" (10 X 100) + 14,600 = 15,600. Refer t( table for pump factors and note that a 4§ x 6 inch x 8 inch pum] will be the size to use. Proportioning air pipes. Air pipes are usually proportioned b] the formula: N = J(—] in which =v B A = Diameter of larger pipe. B = Diameter of smaller pipe. N = The number of pipes of the smaller size to have the same "carrying capacity" as one pipe of the large: size. By "carrying capacity" is meant the amount of air carried, re- gardless of velocity, which will give the same loss in pressure due to friction per unit of length in each case. The diameter of a round pipe to have the same carrying ca- pacity as a rectangular pipe of dimensions A and B is given bj the formula : -^. " 32A''B'' (A + B) The method usually followed in laying out factory work is as follows: Refer to the equalization table which is applicable foi either round or square pipes, but not for both at the same time This table gives the number of 1 inch pipes to equal in carrying capacity the various sizes given. Thus, if 1 — ^12 inch pipe wiL carry a certain amount of air a certain distance with a certair loss of pressure due to friction, there would be required 501 — 1 inch pipes to carry the air the same distance with the same loss of pressure, or there would be required 501 h- 244 = 2 +, pipes each 9 inches diameter or say 1 — 9 inch pipe and 1 — 10 inch pipe. COMMERCIAL PRACTICE IN REGARD TO HEATING BUILDINGS 93 Going back to the example and noting that the width of the lOusing is 57 per cent the diameter of the wheel : The outlet of 8- ilade fans is usually made square with each dimension equal to he width of the housing. The fan has a wheel 8 feet = 96 inches iiameter, X 57 per cent = 54 inches which is one side of the out- et, 54 inches X 54 inches = 2916 inches square = pipe 61 inches iiameter. Suppose the fan is set in the roof trusses near the center of the >uilding and that is has two outlets, both the same size. From he equalization table 1 — 61 inch pipe = 29,000 — 1 inch pipes; !9,000 -f- 2 = 14,500 — 1 inch pipes; 1—46 inch pipe = 1562 quare inches area = 31 inches x 54 inches, the size of each fan )utlet. The mains should be carried along the roof trusses and the air ihould be discharged about 3 feet above the floor. The branch jipes should be carried down along columns, etc., preferably 15 )r 20 feet away from the outside walls and be discharged down- ward toward the floor and in the direction of the outside walls. Assume it is convenient to take 15 outlets off each 46 inch main ^which would be about the correct number making them about 20 feet apart). Each outlet would therefore be 14,500 h- 15 = )70 — 1 inch pipes = one 16 inch pipe for each branch. As to ;he size of mains, add the branches together according to the jqualization table as the fan is approached. Thus, to carry three 16 inch pipes would require 970 X 3 = 2910 — 1 inch pipes, which s equivalent on the equalization table to one 25 inch main. By using the fifteen outlets each 16 inch diameter on each Dranch as obtained above, we would perhaps get 10 per cent more lir out of the outlet nearest the fan than we would from the out- let furthest from the fan. This is not a serious error, and it would ;asily be taken care of by adjustments of the dampers; but to offset this, and to allow for a cooling of the air before it has reached ts most distant outlet, it is usual to make the outlets larger as we get farther away from the fan. In this case, taking each 46 nch branch, starting from the center of the building and having ifteen outlets, instead of making them each 16 inches diameter rt^e would make the four most distant from the fan about 17 inches iiameter, the next six approaching the fan 16 inches diameter, 94 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS and the five nearest the fan 15 inches diameter, adding the branch( on the equalization table to get the mains. The method just given is the one usually followed in factoi work. There is so much uncertainty in this class of work that seems unnecessary to attempt more refinements. The best a( vice in factory work is to get the fan large enough. If the heat( is inadequate it is usually a simple matter to add an addition; section or so of coil, or if you "fall down" on the duct system it often a case of merely making extensions to the piping; and eith( item will cost little more after the system is installed than if pi in with the balance of the work. The most exact method consists in laying out a duct systei with a certain loss of pressure due to friction, and then designir the fan to suit the conditions. Sufficient information on such duct system is given in other parts of this book. Here follo\^ the design of a fan, assuming that the duct system is as follows The longest run of duct is : Feet One-half the length of building = 160 One-half the width of building = 50 Drop to floor = 30 Total =240 Each fan outlet is 46 inches diameter = 1662 square inches = 11^ square feet. The amount of air through each outlet is 49,4C -^ 2 = 24,700 C.F.M. Velocity in duct = 24,700 4- 11| squai feet = 2150 feet per minute = 36 feet per second. As we are using a cone between fan inlet and heater, and ha'v not sudden enlargements, we may neglect the entrance head, etc and assume the static pressure to be composed entirely of frictioi A very safe formula for friction in ducts is as follows : ^ = ^^;ooo:d' ^^"^ P loss of pressure in ounces per square inch. L = length of galvanized iron duct in feet. D = diameter of duct in inches. Substituting D = 46 inch, L = 240 feet, and F = 36 feet, w have COMMERCIAL PRACTICE IN REGARD TO HEATING BUILDINGS 95 p 240X36X36 ^ „. n ar ■ u ^ = 25,000X46 = ^-^^ °'- = ^-^^ ''''^'' ^•^- This is the loss due to friction in ducts. The friction in 24 rows of 1 inch pipe coil at 1250 feet velocity per minute = 0.65 w.g. The inlet of the 8-foot wheel would be 96 inches X 0.625 = 60 inches diameter = 19| square feet. The velocity through inlet, which in this case represents the highest velocity in the sys- tem, = 49,400 -^ 19| = 2400 feet per minute = 40 feet per sec- ond. The pressure necessary to create any velocity is given by the formula ^•■^^•^-=81(^ + 460)'^^^^^'^ A.V.P. = the pressure required in inches w.g. V = the velocity per second to be created. t = the temperature of the air handled. Substituting in the formula above "F = 40, t = 130°, we get 40X40 ^•^•^ = 8i (130 + 460) = O-^^ i^^hes w.g. Inches w.g. Duct friction 0.46 Heater friction 0.65 A.V.P 0.33 D.P. or dynamic pressure 1.44 As this is a "draw through" apparatus and the larger part of the resistance is on the inlet side, we will use the table for restricted inlet. A.V.P -^ D.P- = 0.33 H- 1.44 = 23 per cent. Refer to table and note that when this ratio is 23 per cent the following condi- tions will prevail: A.V.P. +P.V.P 20 D.P.H-P.V.P 86 S.P.H-P.V.P 66 Ko = 0.55, Ka = 3.10, andM.E 54 96 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS P.V.P. = D.P. -^ 86 per cent = 1.44 ^ 86 per cent = l.( Referring to the formula given before connecting pressure a velocity we get, transposing the formula for velocity: Peripheral velocity = VS.S (130° + 460°) X 1.60 = 92 feet i second = 5500 feet per minute. The formula for capacity given in the explanation of the tabic WND^T C.F.M. = — = , the symbols being there given. W m tl case = OAD. Substituting, the formula becomes C.F.M. 0.4iVDV Now DN = peripheral velocity ^ t = 5500 -=- 3.1416 = 1.7; _ 0.4.J^(1750) _2200i)^_ ■ 3.10 3.10 Therefore D^ = C.F.M. ^ 710 = 49,400 ^ 710 = 70, and D V 70 = 8.3 feet = 100 inches. Area inlet = — y^ — = — — , , = 22.65 square feet = 32 VdP \/1.44 square inches = 64^ inches diameter. The standard inlet i 8-foot wheel is 59 inches diameter. N = 5500 -^ 8. Sir = 211 revolutions per minute. Note that our former solution, which we might call appro: mate, gave us an 8-foot diameter wheel at 223 revolutions j minute, which, after all uncertain conditions are taken into i count, is probably as nearly correct as this one. POWER REQUIRED Brake H.P. = Air H.P. h- M.E. Air H.P. = force in pounds x distance in feet per minute 33,000. Now the distance in feet per minute = velocity per minute C.F.M. -^ area of duct in square feet ; and the force in pounds area of duct in square feet X 144 X total pressure in inches w 4- (16 X 1.73). Therefore COMMERCIAL PRACTICE IN REGARD TO HEATING BUILDINGS 97 D IT p _ C.F.M . Xarea duct in square feet X 144 X total pressure area duct in square feet X 16X1.73 X33,000XM.£?. C.F.M. X total pressure in inches ws. „, • • , ,• = M.^.x6350 • This IS a general for- mula applicable to all kinds of fans, and in our particular case substituting M.E. = 54 per cent, C.F.M. = 49,400, and pressure = 1.44 inches w.g., we get: _ 49400 X 1-44 _ ■ ■ 6350X0.54 By "total pressure" above is meant not the peripheral velocity- pressure, but the djmamie pressure. Many kinds of buildings, by reason of the nature of the work carried on in them, or the more or less sedentary occupations of the employees, require special treatment. Textile mills. Textile mills are generally heated from one side of the rooms. The heat flues are brought up in the outside walls, being plastered on the inside or lined with fire-clay flue lining. There is usually an abundance of exhaust steam for heating, but often a considerable quantity of the exhaust steam is used in the dye-rooms, etc. As a rule, the air should not be recirculated on account of the fine lint which fills it and the comparatively large number and sedentary positions of the operatives. About four air changes per hour gives the minimum amount of fresh air to be put into the rooms. The velocity of air in the vertical flues is usually about 900 feet per minute, and the velocity through the mill dampers should not exceed 400 feet per minute. Foul-air ducts are sometimes provided, but no exhaust fan is necessary. Paper mills. In the machine rooms of paper mills the amount of air supplied should be about 100 per cent more than is required for the heating figured on a B.t.u. basis. This is on account of the large amount of moisture given off by the machines in the form of steam. If all this vapor had to be absorbed by the air, the air quantities would be tremendous. There should be a hood over the machine, with an exhaust fan connected thereto, the object being to re- move the steam before it has had a chance to condense. The capacity of this exhaust fan should be about 75 per cent of the 98 MECHANICAL EQUIPMENT OP FEDERAL BUILDINGS total amount of air forced into the room. It is said that thi are about two pounds of water evaporated for each pound paper made, and that the capacity of an average machine is fr( one to one and a half tons of paper per hour. This, however a very general rule. On account of the rapid deterioration of the galvanized ii ducts, they should be made out of iron two gauges heavier th the ordinary, should be soldered with as little punching and riv ing as possible, and should be hung with copper or brass bands Foundries. In foundries a large amouat of steam and otJ gases is given off during the pouring stage. Many of these ga are heavier than air and will not rise to the roof. There shoi be not less than three changes of fresh air per hour, but un( suitable circumstances arrangements may be made for recir^ lating the air at times when no processes are going on to contai nate it. If possible aii exhaust fan should be provided, anc disc fan will often answer this purpose. The inlets to this exha' fan should terminate in bell-shaped orifices about three feet abc the floor line. The hot-air outlets should be about as in an or nary factory job, about 15 or 20 feet above the floor. The abc remarks apply to iron foundries. In some of the large br: foundries it seems simply impossible to get anything like sa1 factory ventilation. The same system is about the best one a brass foundry, but the air quantities should be at least th: times that given above. The exhaust fan should in either case of about the same capacity of the heating fan. Distillery warehouses. In this class of buildings, on accoi of the high specific heat of the spirits which are constantly bei removed and replaced by fresh goods, the heating proposition 1 comes somewhat special. Good practice is to increase the i pacity of both fan and heater about 25 per cent over that requii for the heating alone. This will usually give pretty close to fc air changes per hour. Even then, starting up the apparatus wh the weather is cold, it will be found that several days will be quired to get the building and contents up to the temperati figured on. The construction of such a building usually lends itself V€ admirably to heating. Generally parallel brick or concrete ws are built about four feet above the ground and about five f( COMMERCIAL PRACTICE IN REGARD TO HEATING BUILDINGS 99 apart for the full length of the building. These walls are used to support the racks in which the barrels are piled to the top of the building, sometimes forty feet or more high. There are usually about three aisles, one on either side and one in the center of the building. These aisles are open all the way to the top of the building and are the only portions of the building that are floored. The spaces under these aisles are used for hot-air ducts. They may have a concrete floor unless galvanized iron ducts are run in them. In any event the aisle floor just above, which is of wood, should be protected by a sheet of galvanized iron or bright tin. The air is admitted to the room through heavy cast-iron gratings placed in the floor of the outside aisles about 30 feet apart. These gratings must be extra-heavy, as a truck with a barrel of spirits will often pass over them; and they should have a suitable deflector placed in the duct below so that a correct distribution of air may be assured. Air is always recirculated as there is nothing what- ever to contaminate it, the space under the center aisle being generally used for this purpose. Similar gratings are arranged in this aisle for removing the air, and the total area of gratings should be the same as the hot air gratings, which should allow an inlet velocity of, say, 500 feet per minute. The entire air system out- side the building should be closed tight, and this recirculating duct should be carried back to the inlet of the heater coil. An exhaust fan system is very seldom necessary, as the ducts are usually large, owing to the construction of the building. The apparatus is usually placed in a separate building, and the system will be very simple and inexpensive if this building can be placed at the end of the warehouse so that the fan can draw air directly out of the recirculating duct, and a double discharge fan is used with one discharge, going to each of the hot-air ducts. The ducts from fan to warehouse will of course be underground, and are- constructed usually of brick or concrete. Exhaust steam is sel- dom available, and the general practice seems to be to use live steam on the coils at boiler pressure and return this condensation to the boiler in the most feasible manner. The engine exhaust is connected into a separate section of the coil and this condensation is returned to the boiler, through a separate return system. Planing mills, etc. In woodworking plants in general there is usually ample exhaust steam, so that little would be gained in 100 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS recirculating the air, except in cost of the heater. Often the are exhaust systems carrying out considerable quantities of a and there is usually much opening and closing of large doors, ai the construction of the building is often rather poor. At least much fresh air should be put into the building as is carried out 1 any exhaust system. Railroad round-houses. This is about the most uncerta class of buildings in regard to heating. The ventilation is quite serious proposition, the locomotive doors are open half the tir and often the locomotives have considerable snow on them to 1 thawed off before they can be inspected. These uncertainties p the round-house in the "guess" class. Never less than ten air changes per hour should be allowe always fresh air. The heating surface should be able to raise th amount of air from the outside temperature to about 140° whi( will require as a general rule about 300 to 400 square feet of hea ing surface per stall. All hot air should be delivered through underground ducts in the locomotive pits. Sewer pipe laid in the. usual manner may 1 used for the smaller size ducts. Ducts should be proportioned ; previously explained. Velocity at outlets into pits should not 1 over 600 feet per minute. In the average round-house each p will take four openings each 20 to 22 inches diameter. Aboi one length of pipe may be used as an outlet and behind this £ "increaser" should be used, for in "equalizing" the fan outlet will generally be found that each of these outlets should be f( by a branch from the main about 15 inches or 16 inches diamete A suitable adjustable blast-gate should be set in each outlet to 1 operated from inside the locomotive pit it supplies. Ventilators, smoke-jacks, and the opening of doors will gi'' ample means for the escape of air. Apparatus is usuallj^ required to be outside the building, ar when possible should be located near the center,, on the outside ' the round-house. In case of small round-houses the apparati may be set at the end of the building, but it will often be four that with this arrangement there is not sufficient room for tl main duct from the fan to pass between the footings of the ou side wall and the locomotive pits. COMMERCIAL PRACTICE IN REGARD TO HEATING BUILDINGS 101 Systems of exhaust ventilation. Systems of exhaust ventila- tion have been mentioned several times in connection with the heating- question. In many kinds of industrial works such as foundries, dye-houses, etc., gases are generated, often times heavier than air, which must be removed at once. This can be accomplished satisfactorily onlj' bj- exhaust ventilation. Disc fans may be used for this pur- pose where the runs of ducts are short or no ducts at all are required. When the offensive gases are local to the fixtures, as in dye- rooms, kitchens, etc., a hood suspended over the entire fixture the top of which is connected to the inlet of the exhaust fan is usually the best solution. Where the odors or gases are not local to any particular fixtures, as in a foundry, a system of bell-mouthed openings with inlets connected to the exhaust fan inlet will be found most effective. As to the amount of air to be removed, judgment "must be dis- played. No definite rule can be given, except that the amount of air handled should be as great as conditions permit. It is best not to blow air into kitchens, toilets, etc., from which offensive odors might find their way into other parts of the build- ing, but preferably exhaust from them as with exhaust fan pulling on them there will be an inrush of air whenever a large opening into the room exists. If, however, such rooms are very large, as the kitchen in a large hotel, it may be necesary to blow some air into the room, but the capacity of the exhaust fan should be at least 25 per cent greater than that of the plenum fan. Toilet-rooms. For a large number of fixtures local ventilation, supplemented by a register in the ceiling and another in the side wall near the floor, is a good arrangement. The local vent horns on closets are usually two to three inches in diameter. Connect each local veirt full size, and add the pipes according to the equali- zation table. In hotels and office buildings the private bath rooms are usually one above another on the various floors for convenience in making plumbing connections. In these rooms where there is but one closet it is not the custom to resort to local ventilation, but to place about 6 inch x 6 inch lock-face register in the wall just above 102 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS the closet seat and connect this register in the wall to the mair exhaust riser passing up the pipe shaft just behind. These vari- ous risers are collected at the attic and connected to the exhausi fan. In fine work is it desirable to have a separate riser from each private bath room to the main gathering duct in the attic to pre- vent noises passing from one room to another, but this will often be found impossible for structural reasons. Considerable care must be exercised in determining the size of ducts, as they will be somewhat small and the friction is liable to be excessive. In local venting, an adj ustable damper should be placed in the branch to each fixture and the closets should of course have no covers. Kitchens, boiler rooms, etc. In kitchens, laundries, boiler rooms, etc., the foul air should be removed for the most part by hoods placed over the ranges, stoves, etc., and in front of the boilers. When supplying air to such rooms some care must be exercised to see that a blast of relatively cold air is not blown directly to- wards a workman. If the system is to be used in winter it may be necessary to temper the air slightly. Serious lung affections are often the result of working in a blast of air which is cold com- pared to the air of the room, and as it feels refreshing, workmen are apt to run the risk. The writer has observed that when fresh air is supplied to boiler- rooms, engine-rooms, kitchens, etc., it must be supplied near the floor and exhausted from the top of the room if the system is to be a success. In hospitals, exhaust fans should in general be provided from kitchens, contagious wards, toilets, etc., and in the case of the contagious wards the duct from each room should be extended in- dependently to the main gathering duct in the attic, so as to re- move the remotest possibility of germ-laden air passing through the ventilating system into other rooms. Often electrically- controlled dampers are desirable in such ducts, arranged to close automatically if the fan stops for any reason. Such dampers when properly installed will prevent the transfer of air from one room to another under all circumstances. COMMERCIAL PRACTICE IN REGARD TO HEATING BUILDINGS 103 THE PLENUM CHAMBER SYSTEM This system is used almost universally in schools, hotels, etc., where the warming is done by hot air and continuous ventilation is desired. The fans discharge into a large closed chamber which is divided by a horizontal partition into two portions, the upper portion being generally used for the hot air and the lower portion for the tempered air. The cold air- is usually taken from the top of the building by air shafts built for that purpose. Thence it passes through a tempering coil of sufficient capacity to raise the air to about 60°, if no washer is used. If an air washer is used the temperature should also be raised to about 60°; but the washer will reduce the temperature to about 45°, and another section Of coil should be introduced to raise the air to about 60° before the air enters the fan, although this is not often done. The use of bypass dampers is discussed under the subject of automatic temperature control. Thence the air is drawn through the fan and forced over the heating coils. Under the heating coil is a bypass without a damper. The air which goes through the heater passes into the hot air portion of the plenum chamber, and that which goes through the bypass passes into the tempered air chamber. The temperature of the hot air chamber may vary from 100° to 140°, and that of the tempered air chamber from 45° to 70°. There is a separate duct leading from this chamber to each room, or perhaps several ducts lead to a large room. In each duct, at the plenum chamber, a set of mixing dampers is installed. Each duct has a full size connection to both the hot and tempered air portions of the plenum chamber, and the mixing dampers are so arranged that the sum of the openings from both portions of the plenum chamber into the duct shall remain the same; and the pressure in the two portions being prac- tically equal (as a matter of fact the pressure in the tempered air portion is always a little greater than that in the hot air portion due to the friction in the heater coil) the same amount of air will flow regardless of the positions of the mixing dampers. These dampers are usually arranged to swing parallel with each other 104 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS at all times. Each set of these mixing dampers is comiected to a motor-valve which is operated by a thermostat located in the room supplied by the duct. In addition to the mixing dampers which affect the temperature of air supplied but not its quantity, there is placed in each duct near the plenum chamber a volume damper, the object of which is to regulate the amount of air in each duct. By-passes under heating and tempering coils are usually made about 50 per cent the free area of the coils above them. School houses. The boilers operate as a rule on 30 to 40 lbs. pressure. The fan is usually driven by a direct-connected low- pressure engine operating on boiler pressure. This is decidedly the cheapest way of operating the engine, because the exhaust steam is used in the heater and it may be said that the steam to operate the engine costs nothing, for it is well known that exhaust steam is worth nearly as much for heating purposes as live steam. When electric power is to be purchased it is entirety possible for the electric current to cost as much as the steam to heat the air. The cost of the electric current is simply wasted, and that much might have been saved. Small vertical engines for driving fans are made today that are almost as near "fool proof" as an electric motor and requires as little attention. The coils are fed direct from the boiler through a pressure- reducing valve. The engine exhaust passes through an oil separa- tor into the low pressure side of the heating main. Steam pres- sure on the heater is about 2 to 3 pounds, or atmospheric. The condensation is usually returned to the automatic feed pump and receiver by gravity and then to the boiler by the pump. Sometimes a system of return traps is used. In this case there is generally required one trap below the coils into which the water can drain by gravity, and a second trap on top of the boiler which receives the discharge from the first tap and returns the water to the boiler. The live steam connections to these re- turn traps must be made from the high pressure side of the steam main. Hotels, etc. Generally in buildings of this character there is a power plant in the basement, for operating generators, ice plant, pumps, etc., and fans are then usually driven by electric motors, direct-connected, and the heaters are supplied with steam COMMERCIAL PRACTICE IN REGARD TO HEATING BUILDINGS 105 from the exhaust of the various engines, pumps, etc. There is often a variety of uses for exhaust steam, and the pipe lines are long; and it will nearly always be found necessary to use some of the reliable mechanical vacuum systems. Heaters and tempering coils. The heating and tempering coils, combined, are usually 16 to 24 rows of pipe deep or equiva- lent depth of cast-iron sections. The velocity is usually about 800 feet per minute. Air shaft. The velocity in the air shaft should not exceed 600 feet per minute. Ducts and flues. As a general rule ducts are figured for a velocity of 900 to 1200 feet per minute and the vertical flues from 600 to 900 feet per minute. Capacity and power of fans. Formulae for capacity and power of fans may be found under cases III and IV, depending upon which is applicable. Foul air removal. For the removal of foul air vent ducts should always be provided. In schools and small office buildings vent rises the same size as the hot-air flues should be provided, leading directly to the attic where means of escape should be arranged, preferably by common ventilators of ample size. As a general rule it is not necessary to collect piping systems in the attic. In hotels, large office buildings, club houses, etc., the runs of both heat and vent ducts are long and tortuous. It is usually the case that the foul air is removed through the basement and to the outside through exhaust flues provided for the purpose. In such cases the foul air ducts may as well be omitted if they are expected to remove the foul air without a special exhaust fan for the purpose. The subject of exhaust ventilation is hereinafter discussed. The typical school-room is about 28 x 32 feet, and allowing one pupil for each 15 square feet of floor space (the general rule) and 30 C.F.M. to each pupil, we get 1800 C.F.M. to each room. This requires 3 square feet of duct area, and at 300 feet velocity per minute 6 square feet of screen area. Often a cloak-room is just off the class-room and so located that a screen can be placed in the connecting door, allowing the warm air from the class-room to circulate through the cloak-room on its way to the foul-air duct, which has its inlet at the far end of the cloak-room. This warm 106 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS air serves the double purpose of ventilating this room and dry- ing the children's clothing. Avoid such myths as gossamer checks, etc., as occupants of the rooms often imagine that they are getting no ventilation when these checks are closed (as they usually are), when as a matter of fact the air is escaping by more convenient channels than the foul air ducts. Registers, grilles, etc. As a general rule wire screens made of about No. 12 wire, 1-inch diamond mesh, wired in |-inch channels, and the whole enameled black after being finished and in place, are used in school-rooms. These screens are cheap, present a neat appearance, offer the freest possible passage to the air, and (so desirable in school-room work) contain fewer corners in which dust can find lodgment than any other contrivance. In office buildings, etc., register faces are generally used when the temperature is controlled automatically. As a general rule the bottom of the hot-air outlets should be about 8 feet above the floor, blowing straight toward the exposed wall. The foul-air outlet should be at the floor line as nearly under the hot-air outlet as possible. In hotel lobbies, caf^s, etc., a system of exhaust outlets for summer use is usually desirable at the top of a room. The ducts from such outlets may be connected to the same exhaust fan as the other vents, and either set of vents may be used by a suitable arrangement of dampers. Floor registers should usually be avoided, as they are extremely unsanitary. However, in school work it is a good plan to put a floor register about 48 inches x 60 inches or larger in each entrance hall as a "foot warmer." THE DOUBLE DUCT SYSTEM In this system, which has little to commend it, the plenum sys- tem is dispensed with and two ducts, a hot-air duct and a tem- pered-air duct, are carried to the base of each vertical flue. The arrangement of fan, heater, tempering coil, air washer, by-pass, etc., is exactly as explained for the plenum-chamber system. The air which goes through the heater passes into the hot-air duct, and the air which goes through the by-pass passes into the tem- pered-air duct. The hot-air duct, which is usually on top, is COMMERCIAL PRACTICE IN REGARD TO HEATING BUILDINGS 107 large enough to carry the entire amount of air; and the tempered- air duct is just below it and is about two-thirds the size of the hot-air duct. The mixing dampers are installed at the base of each vertical flue, instead of at the plenum chamber as in the plemmi-chamber system. These dampers regulate the temperature of the air de- livered to the rooms, but not the quantity. To regulate the quantity the usual volume dampers are installed in both pipes of each branch from the main. The pipes of the system are clumsily arranged and unwieldy. One of the double ducts should be on top of the other for conveni- ence in making the double connections, and this often takes up too much headroom unless the ducts are made very shallow, which is objectioiiable. The dampers are scattered all over the building, and it is almost impossible to get this kind of a system into a complicated building, such as a hotel. It has, however, the advantage of permitting hand control of the temperature with continuous ventilation. This hand control is accomplished by haAdng a suitable arrangement of levers extending down inside the air flue, and so arranged that the positions of the mixing dam- pers can be controlled from the various rooms. Of course this arrangement is possible only in buildings of the simplest con- struction. With the double duct system it is possible to use some of the inexpensive and effective systems of automatic tempera- ture control, which, as hereinafter explained, are not applicable to the plenum-chamber system. AUTOMATIC TEMPERATURE REGULATORS For a plenum-chamber system the systems of automatic tem- perature control working through the agency of compressed air or electricity are the only practical ones, compressed air being preferable. For a double duct system, where the mixing dampers are placed at the base of the vertical flues, some of the cheaper systems in which the mixing dampers are operated by a lever extending down from the thermostat in the room through the vertical flues to the mixing damper will probably give satisfaction, if proper care is given to the design of the levers and dampers. 108 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS In the pneumatic systems there are two kinds of thermostat one operating the damper with a gradual motion backward ai forward, seldom closing it off entirely, and another kind operatii the damper with a so-called positive motion in which the damp is either entirely open or entirely closed. There are argumen for and against both systems. Tempering coils. With the plenum chamber and double du systems the tempering coils are controlled in the manner herei: before described, whether an air washer is used or not. Heating coil. As a general rule, automatic control is not pr vided on heating coils, the sections beinig separately valved f hand control. Mixing dampers. These dampers are controlled by therm- stats in the various rooms, one thermostat to a room being ord narily all that is required. The thermostats should be of a tyj that will operate the dampers with a graduated or gradual!; moving motion. Cloth filters. Cloth filters are inefficient, and have greater ri sistance than is generally supposed, and their use should be di couraged. The writer recently observed a case where a new, dec filter of the texture of ordinary cheese-cloth was in use, and a v locity of 1 foot per second through same reduced the capacity i the fan exactly 25 per cent, all other conditions remaining tl same during both tests. AMOUNT OF AIH FOR VENTILATION The following table represents good practice as to the amoui of air required for the ventilation of various classes of buildings Hospitals 50 to 75 cubic feet per minute per occupant High Schools 30 cubic feet per minute per occupant College class-rooms 25 cubic feet per minute per occupant Theatres, etc 25 cubic feet per minute per occupant Churches 20 cubic feet per minute per occupant Public waiting-rooms 4 air changes per hour Public toilet-rooms 10 air changes per hour Locker rooms 6 air changes per hour Small convention-hall 4 air changes per hour Public offices 3 air changes per hour Private offices 4 air changes per hour COMMERCIAL PEACTICE IN REGARD TO HEATING BUILDINGS 109 Ball-rooms 4 air changes per hour Public dining-halls 4 air changes per hour Banquet halls 5 air changes per hour Public libraries 3 air changes per hour Private libraries 4 air changes per hour Railroad round-houses 12 air changes per hour Textile mills 4 air changes per hour Foundries 3 air changes per hour Hotel lobbies 4 air changes per hou* Hotel kitchens 4 to 6 air changes per hour Boiler-rooms 2 to 6 air changes per hour Engine rooms 3 to 6 air changes per hour When it is desired to keep the air in a room at a certain stand- ard of purity, which is usually expressed in so many parts of CO2 per 10,000 parts of air by volume, the amount of air to accom- plish this may be estimated as follows : It is always necessary to make an assumption as to the amount of CO2 in the outside air. This is usually taken as 4 parts in 10,000. a = number parts of CO2 allowable in the air of room. b = number parts of CO2 in external air. C = cubic feet of CO2 per hour to be dissipated. Cubic feet of fresh air per hour = [C h- (a - b)] X 10,000. a = about 7| in schools. b = about 4 in ordinary external air. C = about 0.6 cubic foot per hour per person. RELATIVE TEMPERATURES In contract work a guarantee is generally required that the plant will heat the building to a certain temperature when the outside temperature is a certain degree. As it is usually incon- venient to postpone the final tests until the low outside tempera- ture named in the guarantee is reached, it is desirable to have some means of arriving at results with outside temperature above that point. When the plant is tested, if it meets the guarantee, the resulting temperature in the rooms will be equal to or greater than <2 given by the following formula : 110 MECHANICAL EQUIPMENT OF PBDEKAL BUILDINGS h = [Tit - h) + tziT -t) H- (r - fi), when t = inside temperature named in the guarantee. ti = outside temperature named in the guarantee. ti = inside temperature maintained during test. ta = outside temperature during test. T = temperature of steam or water assumed to be t same in test as in guarantee. The accuracy of the above formula depends on the followin The heat losses from the building are in direct proportion to i. temperature difference inside and outside; the condensation fro direct radiation is proportional to the difference in temperatu of steam or water in the coil and that of the room; and in cas of indirect or blast coils the condensation is proportional to t] difference in temperature of steam or water in the coil and th, of the entering air. There has been considerable argument recently as to the co rectness of the above hypotheses, without advancing any that a more reasonable. One reason for a plant in a newly constructed building failii to produce the expected temperature may be that so large a pa of the heat given off by the coils is taken up in drying out tl brickwork, etc. This is especially noteworthy in concrete buiL ings. In making the test the boilers should be run on the guarantee pressure; and in case of fan work the dampers should be set 1 give the predetermined distribution of air and the fan should 1 run at the specified speed with all vent ducts open. COSTS The following table gives figures by which a rough preliminai estimate may be made of the approximate cost of a job. All a] paratus given is erected complete. Steel plate fans: If cents per C.F.M. for factories with foundations. IJ cents per C.F.M. for schools, etc., with foundations. Engines (direct-connected) : 1 cent per C.F.M. for factories including foundations. COMMERCIAL PRACTICE IN REGARD TO HEATING BUILDINGS 111 1| cents per C.F.M. for schools, etc., including foundations. Plenum chambers, f to 1 cent per C.F.M. Heating surface (iron pipe or cast iron), 40 cents per square foot of surface. Galvanized iron work, 10 to 12 cents per pound. Registers, If cents per C.F.M. Register faces, 1 cent per C.F.M. Boilers and piping, .ifl.SO per square foot indirect surface, and 50 cents per square foot direct surface. Miscellaneous steam specialties, 2 cents per C.F.M. Contractor's profit and miscellaneous expenditures, add one-third of total of above. PROPERTIES OP FANS The object of discussing this subject is not to advocate special fans, but to enable the engineer to choose a fan to do a certain work when the conditions are known, but are too far out of the ordinary to permit the use of the general formulae given in other parts of this book. An example will be given for each style of fan discussed, and a different set of conditions will be assumed in each case to illustrate the elasticity of the tables. Steel plate fans. These are the ordinary type of eight or ten- blade fans, in which : Diameter of inlet = 0.61 diameter of wheel. Width of periphery = 0.40 diameter of wheel. Width of housing = 0.54 diameter of wheel. In the following table the symbols are as follows : A.V.P. = pressure due to actual velocity of air at inlet or outlet, called "air velocity pressure." S.P. = total friction loss in entire system, i.e., heater, washer, ducts, etc., called "static pressure." This must also include all loss of pressure due to any cause, as sudden enlargement in ducts, entrance head, etc. This entrance head is not always easy to estimate. An open pipe of 112 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS short length placed in the outlet of a ii will show practically no static pressure, bi place the same pipe on the inlet of the ii and a considerable static vacuum will I found, which is the entrance head. Th head depends, of course, on size of pipe, v locity of air flow, and the condition of tl free end of the pipe. A cone in the end wi reduce this head and increase the air flow, et Each case in this respect will have to be fij ured out on its own merits, reference bein had to the various handbooks which contai data not necessary or desirable to reprodu( here. In the tables based on free inlets an restricted outlets, the entrance head into th inlet is not to be considered, as it has bee taken account of in the tables. D.P. = dynamic or total pressure = A.V.P. plus S.P. M.E. = mechanical efiiciency. P.V.P. = pressure due to velocity of air if it is moving a same velocity as fan tips, called "peripher£ velocity pressure." All pressures are in inches water gauge. The "ratio of open ing" is in fact an arbitrary term. Experimentally, it is the rati of the area of a circular opening in a flat plate close to the fan, am through which it discharges, to the area of fan outlet. if a = constant for blast area. Ko = constant for orifice to be used in the following for mulae : Area inlet = -^; B. = ^; and C.F.M. = ""^^'^ , in whicl VDP Xa K, D = diameter of wheel in feet. W = width of periphery in feet. N = revolutions per minute. C.F.M. = cubic feet of air per minute. Q = C.F.M. H- 1000. COMMERCIAL PKACTICE IN REGARD TO HEATING BUILDINGS 113 Pressure of air due to any velocity is . T^ „ Barometer X V^ , ^■^•^- = 253(460+0 ' ^^'" V = velocity in feet per second, and t = temperature of air. For a barometer of 29.92 inches mercury, the formula becomes 72 A.7.P.= ZT 8i (460 + EATIO OF OPENING A.V.P. D.P. A.V.P. P.V.P. S.P. P.V.P. D.P. P.V.P. M.E. Ka Ko per cent per cent per cent per cent per cent per cent 117 117 10 1 1 116 117 15 20 2 1.5 114 115.5 26 11.3 2.36 30 4 3.5 109 112.5 35 7.5 1.53 40 7 6 102 108 40 5.7 1.10 50 11 10 91 101 43 4.5 0.87 60 15 13 78 91 45 3.8 0.70 70 21 17 63 80 41 3.2 0.55 80 32 23 44 67- 38 2.9 0.46 90 52 28 23 51 31 ■ 2.6 0.35 100 100 33 33 22 2.3 0.26 The above table is based on free inlet and all restriction on the outlet side. The "entrance head" into fan inlet is not to be con- sidered in using this table. For example : Assume we had a heating system in which the total friction loss, etc., in heater, washer, ducts, etc., is 1 inch water, and that we fix 5000 feet per minute as the velocity of fan tips. C.F.M. = 25,000 at 70°, peripheral velocity in feet per second = 5000 4- 60 = 83.3, and P.V.P. = 83.3' 8§ (460 + 70) = 1.54 inches. Now S.P. 4- P.V.P. = 1.00 4- 1.54 = 65 per cent; when this ratio exists, by interpolation in the above table we get: Ratio 114 MECHANICAL EQUIPMENT OP FEDERAL BUILDINGS opening = 69 per cent; A.V.P. -r- D.P = 20 per cent; A.V.. P.V.P. = 16 per cent; D.P. -^ P.V.P. = 83 per cent; M.j 41 per cent; K^ = 3.3; and Ko = 0.56. Since we fixed the pheral velocity at 5000 feet per minute, irDN = 5000, and ^ „ , , tNDW . „,„ C.F.M. X K, 25,000 X i C.F.M. = -^-,wehaveW= ^^^^^— = —^^^ 16.5, and now, since the usual proportions are W = we get 0.4 D^ = 16.5, or D^ = 41.25, and D = 6.43 feet inches. Use a 6|-foot diameter wheel, as this is a standard and W = 16.5 -f- D = 2.54 feet = 30| inches. Now D.P. = P.V.P. = 0.83 X 1.54 = 1.28 inches water, and area inL KcQ 0.56X25 ,„. , . ,„„„ . , = 12.4 square loet = 1780 square inch VD.P. Vl.28 47i inches diameter, and outlet = 1780 square inches = inches X 42 inches. The brake horse-power is 5.2 X D.P. X C.F.M. ^ 5.2X1.28X25,000 ^ ' ■ ■ 33,000 XM.E". 33,000X0.41 Check inlet by A. 7.P. = 0.16 P. 7.P. = 0.16 X 1.54 = inch, and the velocity to give this pressure is: Velocit -v/0.246 X (460 + 70) + 8| = 33.3 feet per second = 200( per minute, which, divided into the 25,000 C.F.M. , gives square feet against 12.4 square feet by the other method. E will be correct. N can, of course, be figured by irDN = 5000 and N = 50' irD = 5000 -^ GJtt = 245 turns per minute. The following table has been calculated from a careful te several 8-blade fans with the outlet practically free and tl striction placed in the fan inlet. It simply means, when pared with the foregoing table, that a given fan will handle air through a given orifice on the inlet side than it will if the orifice is on the outlet. COMMERCIAL PRACTICE IN REGARD TO HEATING BUILDINGS 115 RATIO IKLET OPENING Ka A.V.P. P.V.P. A.V.P. D.P. D.P. P.V.P. S.P. P.V.P. M.E. Ko per cent per cent per cent per cent per cent per cent 10 11.60 1.5 1 150 149 37 2.75 20 6.00 5.0 5 100 95 51 1.16 30 4.55 9.0 11 81 72 54 0.79 40 3.75 13.0 18 ■ 72 59 55 0.61 50 3.10 20.0 23 86 66 54 0.55 60 2.§0 24.0 27 89 65 53 0.51 70 2.56 29.0 31 94 65 53 0.48 80 2.45 32.0 34 95 63 53 0.46 90 2.35 34.0 35 97 63 52 0.45 100 2.30 36.0 36 100 64 52 0.44 Assume that it is desired to exhaust 25,000 C.F.M, through a set of orifices and a pipe in which the friction loss in the pipe plus the static head necessary to be maintained just inside the ori- fices is 1.1 inches water, and to discharge it into free air at 70° temperature; fan to run at about 5000 feet per minute. Velocity, 5000 4- 60 = 83.13 feet per second, and P.V.P- (83.3)2 8| (460 + 70) = 1.54 inches; and now S.P. -^ P.V.P. = 1.10 -4- 1.54 = 72 per cent, and re- ferring to table above, note that: Ratio opening = 30 per cent; K^ = 4.55; A.V.P. -i- D.P. = 11 per cent; A.V.P. ~ P.V.P. = 19 per cent; D.P. -i- P.V.P = 81 per cent; M.E. = 54; K^ = 0.79. KoQ 0.79 X 25 Area inlet = y/D.P. Vl.25 -= 17.6 square feet = 2540 square inches = 57 inches diameter; the D.P., = being 81 percent of P. 7.P. = 0.81 X 1.54 = inches 1.25. Check inlet by A. V.P. = 0.11 D.P. = 0.11 X- 1.25 = 0.137, and air velocity = \/0-137 X 8| X 530 = 24 feet per second = 1440 feet per minute. 25,000 -^ 1440 = 17.4 square feet = 2510 square inches = 56| inches diameter, which is a good check. 116 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS Assume wheel to be D = 57 -^ 0.61 = 94 inches = 7.8: say 8 feet, and N = 5000 -^ Sir = 200. From the formula C.F.M. = — ^^ — , we get ^ C.F.M. X K. ^ 25,000 X 4.55 ^ ^.gs feet = 34 ina 7riVI>2 5,000 X 8 _ 5.2 X D.P. X C.F.M. _ 5.2 X 1.25 X 25,000 _ 33,000 X M.E. 33,000 X 0.54 In the design of 8-blade fans it should be remembered thai diameter of the inlet is more than two-thirds the diameter wheel, the blades may be too shallow for maximum effic therefore the standard proportions should be adhered to as c as possible. Arbitrarily varying the width of the periphery without sponding change in size of inlet and outlet will affect the j mance but little, so long as the discharge area of the whee tDW) is greater than the inlet or outlet area, which is u the case. Double-inlet 8-blade fans are constructed in two ways as re their performance with reference to single-inlet fans, disc heretofore. The first method is as follows: If a double-inl( is to be designed to handle a given amount of air against a pressure, a fan is designed and speed, horse-power, wheel determined for a single-inlet fan to handle one-half the ar of air at the given pressure; and then the width of periph doubled, size of outlet is doubled, and width of housing is inci by an amount equal to the increase in periphery. At the speed the fan will handle twice the amount of air handled t single-inlet fan, and will require practically twice the powe: The second method is to design a single-inlet fan to deli'^ per cent of the volume of air required at one-half the static sure or friction loss, and then, without changing any dimei of the fan (except adding another inlet of same size) it w the work required without change of speed, and the power v three times that estimated for the single-inlet fan. This is COMMERCIAL PRACTICE IN REGARD TO HEATING BUILDINGS 117 on a theory, borne out by experiment, that two inlets, without any other change in fan or_ so-called "ratio of opening," will in- crease the capacity of \/2 as a multiple, and as the pressure varies as the square of the velocity, this will be doubled, and further, since the horse-power varies as the product of capacity and pressure it will be increased by 2 X 1.41 = 2.82 as a mul- tiple, but as there is some loss in efficiency we will call this factor 3. The capacity of an 8-blade fan at same speed and same ratio of opening varies about as the cube of the inlet diameter; therefore to make a double-inlet fan to do the same work as a given single- inlet fan, we have merely to divide the diameter of inlet by \/2 and use two inlets instead of one. In selecting motors or engines for driving fans it is always well to be liberal as to sizes. Cone fans. The following table gives the properties of the ordi- nary type of 8-blade cone fan. The usual proportions are: W = 0.25 D, and diameter of inlet = 0.75 D. This table is based on free outlet and a vacuiun chamber on inlet side in which S.P. is the total static vacuum in chamber necessary to overcome friction, entrance head, etc. RATIO OF OPENING A.V.P. D.P. A.V.P. P.V.P. S.P. P.V.P. D.P. P.V.P. M.E. Ka Ko per cent per cent per cent per cent per cent per cent 88 88 10 3 2 77 79 37 20 6 4 69 73 43 2.9 1.15 30 9 6 64 70 46 2.3 0.90 40 13 11 58 69 48 1.7 0.66 50 17 14 54 68 49 1.5 0.58 60 22 19 49 68 SO 1.3 0.51 70 28 22 45 67 60 1.2 0.46 80 34 24 41 65 50 1.15 0.44 90 39 26 38 64 50 1.1 0.42 100 45 29 34 63 50 1.0 0.38 Assume we were exhausting 15,000 C.F.M. through a 36-inch diameter pipe in which the friction loss and entrance head are es- timated to be 0.50 inch water. Temperature of air 70°. Sup- 118 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS pose we wanted to use a fan to run at a peripheral velocit about 4400 feet per minute = 73| feet per second. p.V.P. = (^3.5)^ ^ 1.20 inches. 81X530 Now S.P. -^ P.V.P. = 0.50 -^ 1.2 = 0.42 per cent, and : the table we find: Ratio of opening = 77| per cent; A.V.I D.P. = 33 per cent; A.V.P. -h P.V.P. = 23| per cent; D.l P.V.P. = 65^ per cent; M.E. = 50 per cent; K^. = 1.16; an = 0.44. ttNDW From C.F.M. = Z. we get ^„, C.F.M. X K 15,000 X 1.16 „ _ „ , . , T)W = = — '- = 3.96, and smce 1 ttND 4400 0.25D, we get D^ = 3.96 -^ 0.25 = 15.7, and D = say 4 fe Now D.P. = 65| per cent P.V.P. = 0.655 X 1.2 = 0.78 i and A.V.P. = 23i per cent P.V.P. = 0.235 X 1.2 = 0.28 : 5.2 X P.P. X C.F.M. _ 5.2 X 0.78 X 15,000 _ 33,000 X M.E. 33,000 X 0.50 KoQ 0.44 X 15 __ „ f . Area mlet = , = , = 72.2 square feet = VD.P. VO.78 square inches = 36| inches diameter. Ch eck inlet by air velocity = y/ A.V.P- X 8i X 53 •v/0r28 X 81 X 530 = 35.4 feet per second = 2125 feet per ite, which, divided into 15,000 = 7.1 square feet = 1020 sc inches = 36 inches diameter against 36| inches above. Us inch diameter inlet, 48-inch diameter fan, 12 inches wide, R.P.M. = 4400 H- 47r = 350. The following table is given for same type of cone fan as al except that all resistance is on the outlet, as for a fan dra free air and discharging into a plenum chamber, the S.P 1 the static pressure in plenum chamber to overcome friction trance head, etc. The ratio of opening is with respect t( inlet. All symbols the same as before. COMMERCIAL PRACTICE IN REGARD TO HEATING BUILDINGS 119 RATIO OF OPENING A.V.P. D.P. A.V.P. P.V.P. S.P. P.V.P. D.P. P.V.P. M.E. Ka Ko per cent per cent per cent per cent per cent per cent 105 105 10 2 2 91 93 51 3.9 20 5 3.5 79 82.5 49 3.0 1.28 30 7 6 69 74 43 2.5 1.00 40 11 6.5 59 65.5 39 2.2 0.82 SO 14 8 62 60 36 2.0 0.72 60 17 10 46 56 34 1.8 0.63 70 21 11 42 53 33 1.7 0.58 80 23 12 38 50 32 1.6 0.53 90 24 12 35 47 31 1.6 0.51 100 26 13 31 44 31 1.6 0.50 Assume we had a heater, ducts, etc., on the outlet of fan in which friction loss and entrance head had been estimated at 1 inch water, 20,000 C.F.M. at 0°. What size fan is to be used if the peripheral velocity is to be 6000 feet per minute, or 100 feet per second? P.V.P. = (100)^ 8i (460) = 2.56 inches, and S.P. P.V.P. 1.00 „„ = 216= ''P^' cent. Refer to the table, and note that: Ratio of opening = 78 per cent; A.V.P- -h D.P. = 23 per cent; A.V.P. -f- P.V.P. = 12 per cent; D.P. -^ P.V.P- = 51 per cent; M.E. = 32 per cent; K^ = 1.6; and Ko = 0.54. A.V.P. = P .V.P. X 0.12 = .12 X 2.56 = 0.308 inch; and air velocity = \/0.308 X 8i X 460 = 34.6 feet per second = 2175 feet per minute; 20,000 -^ 2175 = 9.2 square feet = 1325 square inches = 42-inch diameter inlet. Check inlet by the formula. Area inlet = KoQ 0.54 X 20 ^/D.P- VLSI 9.25 square feet = 1335 square inches = 42-inch diameter inlet. The D.P. being 51 per cent of P.V.P. = 0.51 X 2.56 = 1.31 inches. Since -kDN = 6000, we may find DW by the formula. tNDW= C.F.M. X Ka,from which we get, DPT ■■ C.F.M. X Ka irND 120 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS 20,000 X 1.6 6,000 = 5.33; and since W = -— we 4 get D'- = 5. D^ = 21.3, and D = 4.6 feet = 55 inches. Make D = 54 inches, and 42-inch diameter inlet. A'' = 6C ttD = 6000 -T- (xX 4|) = 425 revolutions per minute. B.H.P. = 5.2 X P.P. X C.F.M. _ 5.2 X 1-31 X 20,000 33,000 X 0.32 = l: 33,000 Xikf.^. "Sirocco" fans. The following tables give the properti "Sirocco" fans under different conditions of outlet restrictii The symbols are as follows : A.V.P. = air velocity pressure at fan outlet. S.P. = static pressure = total friction loss plus 1( pressure due to any other cause. D.P. = dynamic or total pressure = A.V.P. + S. M.E. = mechanical efficiency. All pressures are in inches water. The ratio of opening is with respect to the fan outlet, perature of air handled is 62° F. The standard proportio "Sirocco" fans are: Width of periphery = one-half diamet wheel, outlet is square and each side = two-thirds diamet wheel, the diameter of inlet in the casing is 1 inch to 2 h larger than the wheel, tapering in a cone to the inlet in ts which is equal to the diameter of the wheel less the depth c blades. DYNAMIC OR TOTAL PRESSURE-INCHES WATER o 0.25 0.375 0.50 0,625 0,75 0.875 1.00 1.25 1.50 Per cent 100 95 90 1.000 0,802 0.647 0.528' 0.555- 0.678' C.F.M. S.P. R.P.M. B.H.P. C.F.M S.P. R.P.M. B.H.P. C.F.M. S.P. R.P.M. B.H.P. 2000 303 0.149 1790 0,050 296 0,127 1609 0.088 292 0.110 2450 371 0.274 2194 0,074 363 0.233 1970 0.133 357 0.301 2820 428 0.422 2534 0.099 419 0.360 2275 0,177 413 0,310 3164 478 0,591 2836 0.124 469 0.503 2544 0,221 461 0.434 3467 525 0.776 3105 0.149 513 0,661 2788 0.265 506 0.570 3744 567 0.979 3352 0.173 554 0,832 3010 0.309 546 0.718 4000 605 1.193 3585 0.198 592 1.017 3218 0.353 584 0.878 4475 677 1.670 4013 0.248 661 1.423 3596 0.441 653 1.226 4903 741 2.195 4390 0,297 726 1,868 3940 0,529 716 1.610 ( \ ( COMMERCIAL PRACTICE IN REGARD TO HEATING BUILDINGS 121 CJ 1 a i ii DYNAMIC OB TOTAL PHESSUEE-INCHES WATER o 0.25 0,375 0,50 0.625 0.75 0.875 1.00 1.25 1.50 1.75 2.00 C.P.M. 1451 1777 2050 2295 2512 2715 2900 3243 3555 3840 4105 85 0.526 0.590' S.P. 0.118 0.178 0,237 0,296 0.355 0.415 0.474 0.592 0.711 0.829 0.941 R.P.M. 290 355 410 458 502 541 579 648 710 766 819 B.H.P. 0.097 0,178 0,274 0,383 0,503 0.734 0.775 1.082 1.423 1.794 2.19 C.F.M. 1305 1597 1845 2063 2258 2440 2610 2920 3195 3450 3690 0.595 ' S.P. 0.144 0,216 0,268 0,359 0,431 0.503 0.575 0.718 0,862 1.006 1.151 80 0.426 R.P.M. 288 353 407 455 499 539 576 644 706 762 814 B.H.P. 0.086 0,159 0,245 0.342 0,448 0.566 0.692 0.967 1,27 1.599 1.95 C.F.M. 1179 1442 1666 1863 2040 2205 2358 2635 2888 3120 3335 0.590 ■ S.P. 0.163 0.245 0.327 0.408 0,490 0,672 0.653 0.816 0,980 1.143 1.30 75 0.347 R.P.M. 288 353 407 455 499 539 575 644 705 762 814 B.H.P. 0,079 0,144 0.222 0.311 0,408 0,515 0.630 0.880 1.157 1.458 1.7» C.F.M. 1071 1312 1515 1693 1855 2005 2143 2395 2625 2840 3030 S.P. 0.178 0.288 0.357 0,446 0.535 0.624 0.713 0.891 1.07 1.248 1.421 70 0.287 0.581 ' R.P.M. 290 355 410 459 502 542 580 64« 709 706 819 B.H.P. 0.073 0.133 0.205 0.287 0.377 0.476 0.581 0.812 1.068 1.348 1.64 C.F.M. 980 1200 1386 1550 1698 1833 1960 2192 2402 2593 2773 65 0.240 0.567' S.P. R.P.M. 0.190 293 0.285 359 0.380 414 0.475 463 0.570 507 0.665 548 0.76 586 0.95 655 1.^14 718 1.33 775 1.52 828 B.H.P. 0.068 0.125 0.193 0.269 0.354 0.446 0.545 0.761 1.001 1.26 1.63 C.F.M. 895 1096 1265 1414 1550 1674 1790 2000 2193 2367 2530 60 0.200 0.548' S.P. R.P.M. 0.20 298 0.30 264 0.40 421 0.50 471 0.60 516 0.70 557 0.80 595 1.00 665 1.20 729 1.40 788 1.60 842 B.H.P. 0.064 0.118 0.182 0.254 0.334 0.421 0.515 0.719 0.946 1.19 1.45' C.F.M. 813 996 1150 1285 1408 1520 1625 1818 1990 2150 2300 55 0.165 0.531' S.P. R.P.M. 0.209 302 0.313 371 0.417 428 0.522 479 0.626 525 0.731 566 0.835 605 1.044 677 1.253 741 1.461 800 1.671 855 B.H.P. 0.06 0.111 0.171 0.238 0.313 0.395 0.482 0.674 0.887 1.116 1.36i C.F.M. 729 892 1030 1151 1261 1361 1457 1628 1783 1927 2060 50 0.133 0.517' S.P. R.P.M. 0.217 305 0.325 373 0.434 431 0.542 482 0.651 528 0.759 570 0.868 609 1.084 681 1.301 747 1.518 807 1.73. 862 B.H.P. 0,055 0.102 0.157 0.219 0.288 0.363 0.444 0.620 0.815 1.026 1.25' C.F.M. 643 787 910 1015 1112 1202 1285 1435 1572 1700 1818 S.P. 0.224 0,336 0.448 0,561 0.673 0.785 0.897 1.121 1,345 1.57 1.79' 45 0.103 0.503 ' R.P.M. 305 373 431 482 529 550 610 681 748 807 863 B.H.P. 0.050 0,093 0.142 0,199 0.261 0,33 0.402 0.562 0,740 0.903 1.13 C.F.M. 566 694 800 895 981 1059 1131 1265 1386 1497 1600 40 0.080 0.490' S.P. R.P.M. 0.23 304 0,345 372 0.460 430 0,575 481 0,690 526 0,805 569 0.920 609 1.150 681 1.380 745 1.610 805 1.841 860 B.H.P. 0.046 0,084 0.129 0,180 0,237 0,298 0.364 0.509 0.669 0.843 1.02 C.F.M. 426 623 604 675 740 799 854 955 1046 1129 1.20 30 0.046 0.451' S.P. R.P.M. 0.239 298 0.358 366 0.477 423 0,597 472 0.716 513 0.835 559 0.955 597 1.193 668 1.432 732 1.670 790 1.90 845 B.H.P. 0.037 0.069 0.105 0.147 0.194 0.244 0.298 0.417 0.548 0.689 0.84 C.F.M. 290 356 410 458 502 543 580 640 711 768 820 20 0,021 0.352' S.P. R.P.M. 0.245 288 0.367 353 0.490 407 0.612 455 0.734 , 499 0.857 539 0.979 575 1.224 644 1.468 705 1.713 762 1.95 814 B.H.P. 0.032 0,060 0.002 0.128 0.169 0.213 0.260 0.363 0.478 0.602 0.72 C.F.M. 167 205 237 265 290 313 335 374 410 443 480 10 0.007 0.212' S.P. R.P.M. 0.248 273 0,372 334 0.497 386 0.621 432 0.745 473 0.869 511 0.993 546 1.241 610 1.490 670 1.738 723 1.98 773 B.H.P. 0.031 0.057 0.088 0.123 0.162 0.204 0.249 0.348 0.457 0.576 0.71 122 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS The following table gives certain factors varying with s: fan wheel. WHEEL VOLUME AND B.H.P. CONSTANT R.P.M. CONSTANT SIZE OF Number Diameter inches inche 1 2 3 0.0278 6.00 2x 3 4i 0.0625 4,00 3x 1 6 0.1111 3.00 4x u 7i 0.1736 2.40 5x H 9 0.2500 2.00 6x If lOi 0.3403 1.714 7x 2 12 0.4444 1.500 8x 2i 15 0.6944 1.200 10 x 3 18 1.000 1.000 12 x 3i 21 1.3611 0.857 14 X 4 24 1.7778 0.750 16 x ^ 27 2.2500 0.667 18 X 5 30 2.7778 0.600 20 X 6 36 4.000 0.500 24 X 7 42 5.444 0.429 28 X 8 48 7.1111 0.375 32 X 9 54 9.000 0.333 36 X 10 60 11.111 0.300 40x 11 66 13,444 0.273 44x 12 72 16.000 0.250 48 X 13 78 18.778 0.231 52 x, 14 84 21.778 0,214 56 x, 15 90 25.000 0.200 60 x^ 16 96 28.444 0.188 64 x( 17 102 32.111 0.176 68 xi 18 108 36.000 0.167 72 x' 19 114 40.111 0.158 76 x' 20 120 44.444 0.150 80x1 21 126 49.000 0.143 84 xi 22 132 53.778 0.136 88x1 23 138 58.776 0.130 92 X) 24 144 64.000 0.125 96 x! Example: Assume it be required to force 32,000 C. through a 48-inch X 48-inch duct in which friction loss, ei 1-inch water gauge, using a 72-inch diameter wheel which hi outlet 48 inches x 48 inches. Temperature of air 62° — Ai COMMERCIAL PRACTICE IN REGARD TO HEATING BUILDINGS 123 locity = 32,000 -^ 16 = 2000 feet per minute = 33f feet per second. 3312 ^■^■^- = 8^(460 + 62) = ^-^^ ^^'^"'• D.P. = S.P^ + A.V.P. = 1.00 + 0.25 = 1.25 and A.V.P. ~ D.P- = 0.25 -^ 1.25 = 20 per cent. In the table note that the ratio of opening is 60 per cent, and when D.P. = 1.25 inches the C.F.M. = 2000; S.P- = 1.00; R.P.M. = 665; and B.H.P. = 0.719. Multiplying these quan- tities by the factors taken from the table above we get: C.F.M. = 2000 X 16 = 32,000; B.H. P. = 0.719 X 16 X 11.5; and i2.P.ilf. = 665 X 0.25 = .166 to do the work assumed. "Sirocco" fans are made double-inlet, double-width wheel, double-width casing, and double-size outlets, which, of course, have twice the capacity and twice the power of single-width fans at the same pressure. The tables above refer to single-width fans. Should pressures higher than those given in the table be en- countered, the quantities can be calculated by the fact that the C.F.M. and R.P.M. vary directly as the square root of the dyna- mic pressure; that static pressure varies directly as the dynamic pressure; and the B.H.P. varies directly as the product of dyna- mic pressure and C.F.M. For example : Assume 70 per cent ratio of opening, 2.5 inches D.P. Find C.F.M., S. P., and B-H.P. At 2 inches D.P. the C.F.M. = 3030; S.P. = 1.426; R.P.M. = 819; and B.H.P. = 1.643. Now 2.4 -^ 2.0 = 1.25, and vT25 = 1.12. The new C.F.M. = 3030 X 1.12 = 3388; the new S.P = 1.426 X 1.25 = 1.782; the new R.P.M. = 819 X 1.12 = 916; and the new B.H.P. = 1.643 X 2.5 X 3380 _ 2.0 X 3030 ■ ■ Of course these new quantities are subject to correction ac- cording to size of wheel, the same as quantities taken directly from the table. The table can also be interoolated bv the method above given. CHAPTER III HEATING BY FORCED CIRCULATION OF HOT WATER FRO CENTRAL STATION Heating from a central plant is most common in localities -w the general run of buildings are not of sufficient size to justif; expense of private plants; and even where no exhaust stea available and all the heating is done directly from the co saving in cost of labor and fuel is effected. In generating stations where the electrical energy is use lighting the buildings, the utilization of the exhaust steam : the power units results in a marked degree of economy. Requisites for successful operation. The power plant woul located as near as possible to the center of gravity of the dis served, to avoid excessive loss of heat in the underground trans sion lines, and there must be a large connected heating load large plant should be located on a railroad siding or by a r gable river to insure economical delivery of coal, and a plen supply of good water must be available. Advantages of hot water over steam, where condensing enj or turbines are used. With condensing e» les the water he; are placed between the engines and condensers, and heat otherwise would be thrown away in the condenser overflo utilized, and a saving effected in amount of condenser watei Less heat is dissipated by radiation from the piping with v, at an average temperature of 160° than with steam at 212°, hot water is best adapted to undulating ground, the mains fol ing the contour of the surface, and branch mains or surface nections being taken off at the highest points to prevent formation of air pockets. Economy of operation with hot water is not dependent i the adjustment of delicate parts, such as thermostats, etc., the same efficiency is maintained year after year. Regulation. With all systems of heating the radiating sui is proportioned to obtain the desired room temperature 124 HEATING BY FORCED CIRCULATION 125 minimum outside temperature and with all radiation in use. Steam as the heating medium (unless a vacuum system is used) must entirely fill the system at a temperature of 212°, requiring a large amount of heat. The average outside temperature dur- ing the usual heating season of 200 days is 35°F., hence on the majority of days only a small amount of heat is required, and hot water will distribute this evenly throughout the entire system. Thermostatic control and vacuum systems give close regulation for steam, but these devices generally require careful adjust- ment, with frequent inspection to maintain efficiency, while hot water, regulated from the power house, has been found to be very satisfactory without automatic temperature control. The tem- perature of the circulating water is proportioned to suit varying weather conditions, and the following temperatures of circulating water have been found to be satisfactory: TABLE I TABLE II WITH OPEN EXPANSION TANK WITH CLOSED EXPANSION TANK Outside Temperature Water Temperature Outside Temperature Water Temperature degrees F. degrees F. degrees F. degrees F. 50 140 50 150 45 140 45 155 40 150 40 160 35 160 35 166 30 165 30 170 25 170 25 175 20 180 20 180 15 185 15 ■ 186 10 190 IQ 190 5 195 5 195 200 200 - 5 206 - 5 210 -10 210 -10 220 -15 215 -16 230 -20 215 -20 240 Limitations of hot water system. Water at 180° weighs 60.5 pounds per cubic foot and produces a static pressure of 60.5 -^ 144 = 0.42 pound per foot or 42 pounds per square inch per 100 126 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS feet of head, and this head should rarely be exceeded due tc excessive pressure on the pumps, piping, and radiators, anc tendency to produce leaks and rupture of joints. Quality of material. Selection of materials is determine( considerations of efficiency, durability, and first cost, in the c named. Quality of materials and workmanship especially ir conduit line, should be of the best. Conduits. Five to 12 per cent of the total heat transmitt lost by radiation from the distributing mains, and as this crt an operating expense which is continuous year after year it sh be made as small as possible. Where funds are available, Crete tunnels not less than 5 feet inch wide by 6 feet 6 in high should be used to receive the piping, but when funds limited material for the trenches may be wood, tile, brick, concrete. The best and most recent commercial types of cone comprise the use of hollow tile, brick, or concrete walls restin a concrete base, with hollow tile or reinforced concrete co' the whole made as waterproof as possible by a 1-inch laye cement mortar on sides and top. The piping is provided sectional covering of magnesia, asbestos, or wool-felt, or the tire air space around pipes is packed full of mineral wool, asbe or magnesia. All piping in conduits is supported on pipe rollers. Service connections vary from 1^ to 2J inches in diameter are laid at an average of 3 feet below the surface of the gro Conduits for service connections should compare favorably the main conduits in quality of materials, though 4-inch t wood log pipe covering, lined with tin or asbestos, is genei used and answers every requirement. The drainage of conduits is secured through lines of 4-incl] placed at side of foundations, with outflow to sewer or catch b; Expansion. The expansion of wrought iron is 0.00008 o inch per foot per degree rise of temperature, which for a water main under ordinary working conditions would equal inches per foot of length. Experience has shown, however, an increase in length of 1 inch for each 100 feet will approxir actual results. Offsets made with 90° pipe bends, right-angle turns or ex sion joints spaced from 350 to 500 feet apart, with anchors ] HEATING BY FORCED CIRCULATION 127 way between are used to take up the expansion. Spacing of offsets for district heating in cities is determined by the length of blocks, an offset usually being made in each street crossed by the mains. Straight runs of pipe between anchors are laid and se- cured in place, and are of such lengths that the last joint to be made up in the offset is open an amount equal to one-half the computed expansion between adjacent anchors. The drawing together of this joint provides a stress in the offset when cold equal to that which will be developed when the pipe becomes hot. The pipes are offset from 25 to 30 times the diameter of pipe, the length of the offset usually being equal to the width of the street crossed, and as all turns are made with long-radius pipe bends no great amount of friction is introduced by their use. A maximum movement of 5 inches is allowed for expansion joints which determines the maximum spacing; and they should be simple and of the slip-joint type, with cast-iron body, brass sleeve, and a type of metallic packing, which may be easily renewed. Anchors. The spacing of anchors is determined almost en- tirely by the conditions governing the location of the devices to take up expansion, though in general the mains should be anchored at or near each branch and at important service pipes. Anchors are of two general types, one integral with the joint at which it is used, such as expansion joints or anchor tees bolted to the floor of the conduit, and the other in the form of pipe bands bolted around the pipe. The latter should be applied on each side of a coupling or other fitting to ensure against slippage, and should extend at least 9 inches into the brick or concrete walls of the conduit. Special piers of brick or concrete are often constructed to provide a secure fastening for anchors. Valves. Only straight-way gate valves are used, and these are placed on the trunk mains at the central plant and at such points throughout their length as will allow certain portions of the sys- tem to be shut off for repairs without cutting out the entire dis- trict; on all the branch mains as they leave the trunk; on all by-pass lines; and on all service connections to buildings. Manholes. Manholes are placed at all valves on mains and at expansion joints, and are constructed of brick or concrete with cast-iron frame and cover. Frames should have not less than 128 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS 22 inches diameter clear opening, and joint between frame cover should be practically water-tight. Radiation in individual buildings. The heat lost by expos from each building in British thermal units is found by es1 lished rules, a temperature 10° above the lowest recorded for locality being used as a basis, and the result divided by 170 equal the square feet of direct cast-iron radiation required, diators are placed under windows where possible, and in basement approved types of wall radiators or wrought-iron j coils are suspended from the ceiling. In many systems now in sucpessful operation a water tempi ture as high as 212° has been used in proportioning the amoun radiating surface required for minimum outside weather coi tions, the British thermal units lost from the building being vided by 250 to find the square feet of direct radiSjtion requii since water at 212° will transmit the same amount of heat square foot as steam at the same temperature. During mosi the heating season the outside temperature is considerably hig than the minimum for which the radiation is. proportioned, i the water qan be circulated at a temperature of 180° or lov The larger line losses which occur at the higher water temperat are thus limited to a few days only of the heating season, and more than compensated by the decrease in size and cost of whole installation. A closed expansion tank is used with i system, and for extreme weather conditions the water may circulated at temperatures considerably in excess of 212°. Layout of mains. A drawing showing the location of power-house ajid the buildiings to be served should be prepar and the square feet of radiation required or the heat to be s plied in British thermal units should be noted for each buildi The mains are then laid out to serve the buildings with ■ shortest possible runs, conducts being run in alleys and unpai streets wherever possible, by reason of the lower cost for insta tion and repairs. Valved by-passes are provided between i portant points, and the main trunk lines are cut as little possible. Two systems of mains are in common use, the 1-pipe circuit a the 2-pipe circuit. One-pipe mains are used generally wheri small number of buildings, often at considerable distance aps HEATING BY FOBCED CIRCULATION 129 be heated, the water making a complete circuit through a B main of a uniform diameter, the service pipes to the in- ual buildings being shunts from the main itself. Individual ts are the same pipe-size from end to end, radiator connec- being taken off at necessary intervals and "Y" fittings ided where each shunt leaves and returns to the main, to 56 flow through the building. The supply and return con- ons of each shunt are kept as far apart in the main as the h of the buildings will allow, to provide sufficient resistance use the water to flow through the shunt, and a valve is some- ; inserted in the main between the connections to control resistance. Occasionally the main itself is carried through building, the radiation being supplied by risers frohi shunt its of uniform size taken off within the building, a valve ! placed in the main between supply and return connection lunts to control the flow in same. In individual buildings e the radiation will never be shut off, the entering main is ed into a number of circuits of radiators in series (the com- 1 sectional area of the pipe connection being made 50 per greater than that of the main) which re-unite into a single on leaving the building at the far end. Circulation in low ings may be forced by arranging all the radiation in one or series circuits, the return from one coil continuing as the ly to the next, between the supply and return service connec- . In high buildings the water is carried upward through a riser to the distributing main in the attic, thence downward igh 1-pipe risers to the return mains in basement and out to in street, the circulation in individual radiators being caused avity only. Radiator connections enter radiator at top and same at bottom, "Y" fittings or distributing tees ofteo : used to ensure positive circulation. rtical offsets over doors and at all other points where a hori- I main turns downward are provided with air valves of the type. ^■elocity of flow up to 12 feet per second is maintained in the e mains since the cooled water from one building becomes in the supply water for the next; and as the force producing ation in the service pipes is small, larger sizes are used for than with the 2-pipe system. 130 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS The 2-pipe system is used for large installations and is best adapted to serve contiguous buildings, as in city blocks. Supply and return mains of equal size and in same conduit radiate from the central plant, with suitable reductions in size as the total out- lying radiation becomes less. Circulation in the service pipes and mains of individual buildings is caused by the difference in pressure between the supply and return mains. The size of mains for either system is dependent upon the amount of water to be circulated and the velocity of flow, which, as previously stated, is made 2 to 3 feet higher per second for the 1-pipe tTian for the 2-pipe system. Radiator connections. The size of supply and return connec- tions to radiators and pipe coils depends upon the force produc- ing flow through same, and hence upon the layout of piping and connections. Radiators dependent entirely upon gravity for circulation are tapped according to standard practice for gravity work, the size varying with basement mains and overhead mains, and according to whether a 1-pipe or a 2-pipe system of risers is used. Where the radiators or coils are arranged in series the size of pipe for the whole circuit is proportioned according to the amount of radiation and the friction loss in the total length of circuit, a 2-inch pipe carrjdng generally from 500 to 700 square feet of radiation; and the total area of connections, where a 1-pipe main divides into a number of series circuits, is made 50 to 100 per cent greater than the area of the main itself. Due to the widely varying conditions with different systems found in actual practice, the size connections for all except grav- ity circulation are largely determined for each individual case by the judgment and experience of the designing engineer. Water required to be circulated. In estimating a branch from a main the assumption is made that the difference in temperature between the flow and return pipes is 30°F. Water in coohng from 180° to 150° gives up 30 B.t.u. per pound, hence the total heat lost per hour from the group of buildings supplied by each branch, or contemplated by future extensions to the system, plus 10 per cent additional for transmission loss, divided by 30 will give the pounds of water required for the branch. Water at 180° weighs 60.5 pounds per cubic foot, hence the pounds of water HilATING BY FORCED CIRCULATION 131 ed divided by this figure will give cubic feet per hour. 5ross-sectional area, and hence commercial size, of any s then found by dividing the total cubic cubic feet per jy 3600 X allowable velocity in feet per second, or pounds water per hour ^ = Cross sec- < 3600 X allowable velocity in feet per second area of pipe in square feet. ! area of trunk mains is found by dividing the total cubic if water per second from branch mains by the allowable ty of flow. This velocity is ordinarily made from 5 to 10 er second, the smaller values being used for branch connec- and outlying mains, where they serve to compensate thfe increase in frictional resistance with decrease in diameter of Velocities should be limited to 10 feet per second as a max- , in connection with the largest amount of radiation contem- l by future extensions to the system, due to the rapid increase 3tion with increase of speed as shown by Table III, values 32 y^^* ich are found by the formula for hot water, h = " ^^ h is the loss in friction in feet per 100 feet of length, D is iameter of pipe in feet, and V is the velocity in feet per i. TABLE III Velocity in feet per second : SIZE ^CHES 23456789 Friction head in feet per 100 feet of pipe 2 1.09 2.32 4.06 6.02 8.46 11.25 14.43 17.96 21.88 3 0.658 1.40 2,45 3.62 5.08 6.76 8.70 10.80 13.20 4 0.459 0.980 1.70 2.52 3.54 4.70 6.04 7,60 9.17 6 0.349 0.742 1.29 1.92 2.70 3.57 4.60 5.70 6.97 6 0.276 0.588 1.03 1.52 2.14 2.83 3.64 4.53 5.53: 7 0.228 0.485 0.848 1.25 1.75 2.34 3.00 3.72 4.56 8 0.193 0.411 0.717 1.06 1.50 1.98 2.54 3.17 3.86 9 0.166 0.354 0.617 0.913 1.28 1.70 2.19 2.72 3.33 10 0.146 0.311 0.541 0.800 1.12 1.50 1.93 2.37 2.92 12 0.116 0.246 0.431 0.638 0.900 1.19 1.53 1.91 2.32 132 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS 144 The friction head in feed divided by -— — or 2.38 becomes the head in pounds per square inch. Pipe bends instead of fittings are used wherever possible, and where runs of pipe between fittings are short, 10 per cent is added to the friction loss in the pipe to cover the additional loss in the fittings. In a well-designed plant with a static head not larger than 45 pounds, average outflow and return gauge pressures of 65 and 20 pounds respectively will be found, and the differential pressure due to friction between the supply and return mains, which the pump must constantly overcome, will vary with the size of instal- lation from 25 to 50 pounds, and on account of the tendency to produce leaks and rupture of joints should never exceed the last- named amount. Pipe sizes should be made large enough to assure this. The static heads on suction and delivery sides are equal, hence the only work required of the pump is to overcome the friction due to the velocity of the moving water in the piping system. For example, the size supply and return pipe required to carry 20,000 square feet of radiation, transmitting 170 B.t.u. per square foot, at a distance of 100 feet, with a loss in head of 1 foot, and water in radiation cooled 30°, is found to be 6 inches as follows: 20,000 X 170 -I- 5 per cent line loss = 3,570,000 B.t.u. per hour. 3,570,000 4- 30 X 60.5 X 3,600 = 0.546 cubic foot water per second. Area of 6-inch pipe = 0.196 square foot, hence 0.546 -e- 0.196 = 2.8 feet per second and from Table III, by interpola- tion, the loss of head for 200 feet of 6-inch pipe and velocity of 2.8 feet per second, is 1 foot, equal to 0.42 pounds, per 200 feet of pipe. Wlien buildings can be reached by a circuit with the far end re- turning to the power house, there is less friction loss with the 1-pipe than with the 2-pipe system, hence the former should be used. In 2-pipe work a tabulation of the loss in head for each section of main will show the circulating pressure between the supply and return mains at any point, and the friction loss in all laterals should be proportioned to the circulating pressure at the point where the lateral begins. A throttling union, consisting of an ordinary union enclosing a hardened steel disc with a round ori- HEATING BY FORCED CIECULATION 133 . its center, is often installed on each branch return connec- lear the controlling valve, the frictional resistance being bted to the desired amount by varying the size of the opening 1 disc. This device is particularly useful to prevent short- ting in branch mains which are installed with excessive ca- T in contemplation of future extension, irculating pressure of at least one pound should be maintained i of each branch. jle IV gives average values for the drop in pounds per 100 f flow and return main, per 1,000 square feet of radiation the commercial sizes of pipe up to 10 inches. Average ties are used, increasing as the pipe size becomes larger, lue consideration is given to the fact that, with a 2-pipe n having branch connections at frequent intervals, from 50 per cent only of the total volume of water is transmitted ull 100-foot lengths, the friction being correspondingly ised. TABLE IV ING SUKFACE PIPE SIZE IN INCHES 2 3 3i 4 5 6 7 8 9 10 12 0.50 1.10 2.50 4.00 8.00 0.09 0.25 0.40 0.62 0.85 1.20 1.60 2.00 2.60 0.13 0.20 0.30 0.43 0.64 0.84 1.04 1.30 1.60 3.10 0.16 0.24 0.30 0.40 0.50 0.60 0.75 0.85 1.70 2.85 4.30 0.10 0.13 0.15 0.19 0.24 0.30 0.60 1.00 1.50 2.20 3.00 4.00 0.10 0.12 0.15 0.25 0.40 0.60 0.85 1.20 1.50 2.00 2.50 5 50 0.12 0.20 0.28 0.38 •0.50 0.65 0.84 1.05 1.25 2.40 4.00 0.09 0.15 0.22 0.30 0.39 0.50 0.62 1.30 2.25 0.10 0.14 0.19 0.25 0.31 0.38 0.82 1.35 0.10 0.14 0.18 0.22 0.45 0.75 0.09 0.15 0.25 0.40 lause of the widely different conditions for each installation, roportioning of pipe sizes is determined largely by the judg- and experience of the designing engineer. It is suggested 134 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS by the writer that a curve be plotted for each pipe size with friction drop in pounds per 100 feet, and square feet of radiation, respectively, as ordinate and abscissa. A few ordinates may be computed for each pipe size from Table III, due allowance being made in 2-pipe work for the decrease in friction resulting from the loss of water at each branch connection between the 100-foot points, and intermediate values being given directly by the curve. Central plant equipment. The equipment of the central plant for forced hot-water circulation system of heat consists in general of apparatus for reheating and circulating the water, and is the same for either type of system. A plant designed for heating only is provided with steam boilers to supply high-pressure steam to drive the circulating pumps; an exhaust heater in which the exhaust steam is condensed, the latent heat being absorbed by the circulating water; and water heating boilers to furnish the additional heat needed. The water is forced from the pump through the heaters, thence through the heating boilers to the flow main in the street. Where heating is done in conjunction with the generation of electricity, the exhaust steam from all units is used to reheat the water of the heating system. Where sufficient exhaust steam is not available at all times a live-steam heater is installed as a booster, and by which the whole system can be taken care of temporarily. Many plants have been equipped with economizing coils in the smoke duct between boilers and stack, but because of a rapid decrease in efficiency with length of service, and constant need of repairs, their use has been generally abandoned. Co-minglers or injectors in which the exhaust steam and cir- culating water are mixed directly, as in an open-pipe feed-water heater, are used to some extent, and where they do not intro- duce oil into the heating system have proved very efficient. The return water is passed through one or more units, carry- ing live or exhaust steam or flue gases, either in series or parallel. Two or more combinations are provided and serve as a means for regulating the temperature of the water. Exhaust and live steam heaters. Both types of heaters are cylindrical steel shells with heads bolted on, and with IJ-inch charcoal iron, or 1-inch corrugated copper or brass tubes, ex- HEATING BY FORCED CIRCULATION 135 I into steel plate partitions. Tubes are generally staggered e placed far enough apart to prevent weakening the tube Heaters are placed on end to economize floor space, ated close to the circulating pump on the discharge side, 3 by-passed so that either one or both may be used as con- warrant. Steam enters the heaters near the top and sur- the tubes, through which the water flows upward, the } water coming in contact with the hottest steam thus .g the highest temperature of water possible with a given ty of steam. 1 return water at 150° F., a transmission of 6000 B.t.u. per foot per hour with steel tubes and 7000 B.t.u. with cop- brass tubes is allowed, and the size of exhaust heater de- ed accordingly. The heat transmitted by the live steam will vary with the pressure of the steam, and as a water 'ature as high as 240° is often desired for abnormal outside !r conditions the live steam heater is designed to with- the full boiler pressure, the tube surface usually being one- ;o one-half that of the exhaust heater. Standard practice er design is followed in determining thickness of shells and g of rivets. t available per pound of exhaust steam. The heating Df exhaust steam will average 85 per cent of that of satur- ;eam at the same pressure or 850 B.t.u. per pound. of heater connections. Exhaust steam at atmospheric re occupies a volume of 26 cubic feet per pound, and a y of 6000 feet per minute is allowed in piping, hence B steam per minute X 26 ^ ^^^^ ^^ ^^^^^ connection to 6,000 in square feet. 1 pound of water absorbs 30 B.t.u. in becoming heated from ) 180°, therefore 850 ^ 30 = 28 pounds of water per pound aust steam. iilating pumps. Pumps are usually of the centrifugal type )erate with an average efficiency of 70 per cent against up to 125 feet. For small installations, provision for con- s operation in case of break-down or necessity for repairs le by instalHng pumps in duplicate, each of a capacity 136 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS equal to two-thirds the maximum requirement. In large installa- tions pumps capable of circulating 200 cubic feet of water per minute, and rated at 75,000 square feet of radiation each, are installed in parallel, additional pumps being added as the system is extended. Pumps are direct-connected to steam turbines or electric motors. Expansion tank. An expansion tank, with a capacity of 2 to 5 per cent of the total volume of water in the system, is installed in the power house or in the highest building on the line. A closed type of expansion tank is used when the water is circu- lated at temperatures over 212°, a pressure of 3 to 5 pounds above the static head on the system being maintained from the city water-mains through a regulating valve, or by a small elec- trically-driven air compressor, which is arranged to start and stop automatically. A 2-inch safety valve with waste pipe is also provided. Wherever possible the expansion pipe is taken from the return main as near the suction side of the pump as possible. Water heating boilers. Boiler headers are arranged so one or more boilers of the battery may be used to supply additional heat to the out-going water, and in many plants the entire heat- ing is done by water boilers with electric motors to drive the circulating pumps. A boiler horsepower equals 34.5 pounds of steam evaporated from and at 212° = 34.5 X 970 = 33,465 B.t.u. 33,465 1^^ , 77: 7 =180 square feet radiation per boiler horse 170 + 10 per cent ^ ^ power. 33,464 "30" = 1115 pounds water to be circulated per boiler horse power. Gauges and thermometers. Pressure gauges are provided on the supply and return to each pump and on the mains where leaving the power house. Thermometers are placed on the flow and return connections to each heating unit, and on the flow and return mains where same enter the central plant. CHAPTER IV PLUMBING, DRAINAGE AND WATER SUPPLY re the acquisition of property upon which a Federal build- o be erected, a local engineer is employed to prepare a sur- the site and note thereon the size and location of all sewers ,ter and gas mains; also the elevation of the inverts of the below or above city datum. rder to determine from the survey whether the sewers lie are sufficiently low to drain plumbing fixtures to be in the basement, the first step is to decide which way the g will face, and then find the elevation of the top of the ;urb midway of the lot; assuming that, as usual, the base- loor will be established 6 feet 6 inches below that level, it the basement toilet-room will be located in the furthest of the building from the sewer it is decided to enter. The )e in this toilet-room is assumed to be 8 inches to center }he basement floor at the start, and a grade of |-inch in fall is assimied for the measured run from the basement 3om to the sewer. The estimated fall plus the 8 inches aoted is subtracted from the assumed basement floor ele- and comparison of the result with elevation of the center the city sewer will show at once whether it is feasible to he sewer selected, and, if not, whether any of the other it sewers may be used. is found to be impracticable to enter any sewer which will asement fixtures, the architectural draftsman is so advised, arranges to place all plumbing fixtures on an upper floor. ;re are no public sewers the local engineer who prepares the ascertains and reports whether any sewers owned by pri- iizens are in the vicinity of the Federal property, and if fist, gives all data in connection therewith and states r permission to connect could be secured. If satisfactory can be obtained at a suitable yearly rental, the building are discharged into the private sewer. 137 138 MECHANICAL EQUIPMENT OF FEDEEAL BUILDINGS In the event there is neither a city nor a suitable private sewer, the engineer reports whether the government can install its own sewer through the city streets to some outfall where nuisance will not be created at the point of discharge; and if such a sewer is feasible he submits a drawing showing the proposed route and profile. The government will not build its own sewer unless the city will grant an irrevocable license to install and control same. In the event no public or private sewers exist, and no feasible route or outfall can be secured, the engineer reports whether a cesspool would be feasible, and describes the manner of construct- ing cesspools in that locality. If there are neither city nor private sewers, and on account of a clay soil a cesspool is not feasible, the engineer reports whether there is near the building a small cjeek or normally dry ravine into which it would be possible to discharge the effluent from a septic tank without any filtering. Before resorting to the last expedient special permission is always obtained from the local authorities, who are advised that the effluent from a septic tank is very offensive to eye and nose. In a very limited number of cases it is found that there is no sewer of any description and that none can be constructed ; that a cesspool is not feasible, and that no point of discharge can be secured for a septic tank. Under these adverse conditions a septic tank is installed and the effluent is discharged by gravity only (due to the level ground of site) into subsoil drains surrounded by gravel laid about 14 inches below the surface of the ground. The office is very reluctant to employ either a septic tank or a cesspool, and rather than do so will go to heavy expense in install- ing a sewer for exclusive use of the Federal building. In designing a sewer the following basic data are used : Sewer must never be less than 8-inch diameter, and (except one length outside of each manhole where it passes under car tracks, and at the outfall into a stream or river where the sewer is con- structed of extra-heavy cast-iron) it must be of salt-glazed earthen- ware pipe, with joints made with an oakum gasket and one-to-one Portland cement and sand. Manholes are placed at each change in direction, and on straight runs are spaced 300 feet apart. Manholes are made 3 feet inside diameter, and 9-inch-thick walls PLUMBING, DRAINAGE AND WATER SUPPLY 139 er brick are used until manhole is 12 feet deep; and over 1-inch walls are used. The floor of manhole is concrete and ie 12 inches thick, wiith a channel hollowed out in the con- connect the inlet and outlet pipes. The floor is made on ;le to grade to this open channel. In manholes over 6 feet ron ladders are installed. All manhole covers are solid, th frame weigh not less than 315 pounds each. earth cover over sewer is never less than 18 inches deep and le at least 3 feet deep if possible. The sewer outfall at ream or river where earth banks exist is protected by a wall of concrete. a sanitary wastes and roof water are conveyed in this sewer grade of J-inch in 10 feet is desirable, but if conditions de- 1 inch in 10 feet may be u^ed. A velocity of over 8 feet cond is not allowed if it can be avoided without great ex- for excavation. :ic tanks are constructed on the following basic data: ks are made rectangular and with a depth of liquid of not lan 5 feet; and are of sufficient capacity to contain all the 3 discharged by the building for a period of 8 hours based I gallons per day per occupant, or on 500 gallons per plumb- ture per day if number of occupants is not known, ks are constructed of concrete with walls and bottom 8 thick and with 6-inch-thick reinforced concrete cover with )le. While the present practice commercially permits the open tanks, covered tanks are demanded by conditions in ition with the buildings under discussion, spools are generally constructed of hard-burned common and are usually 8 feet to 10 feet in diameter and 20 feet If there is a sand or gravel stratum, the walls of cesspool n down into same 3 or 4 feet, or far enough to penetrate 1 water if same exists. Where ground water stands at a e level in the cesspool, as is sometimes the case in western and and Pennsylvania, the inlet pipe is turned down below vel of ground water to favor septic action. A solid 315- manhole frame and cover is placed on cesspool and a vent I taken from near top of cesspool and run up inside of build- above the roof. 140 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS When cesspools are used an effort is made to have all plumbing fixtures located on upper floors, as fixtures in basement will over- flow by reason of filling up of cesspool. It hardly seems credible that cesspools would be tolerated in any civilized community, but a large number of prosperous towns still cling to their use. For use in cases where a combined system of sewers is provided in a city, and also in proportioning a drainage system for roof water and sewage or for roof water only, the following table, which is sufficiently accurate for all practical purposes, was made some years ago by the writer and has ever since been used with success by the office. It is based on the very conservative data of sewer running full when the rainfall is at the rate of 6 inches per hour, and on a speed in sewer of approximately 3 feet per second, the minimum speed permissible, and which requires a grade of not less than 1 inch in 10 feet for all sizes up to 6 inches. Even in the larger sewers the grade is made not less than 1 inch in 10 feet. A speed of 8 feet per second should not be exceeded in a strictly sanitary sewer, as an intermittent flow, such as these sewers are subjected to, will cause the liquid to deposit the solids held in suspension. Area of roof Diameter of pipe Square feet Inches 1,000 3 2,000 4 3,000 5 4,500 6 9,000 8 16,000 10 25,000 12 35,000 14 50,000 16 75,000 18 The distance between outlets in roof gutters should not exceed 60 feet. Three-inch diameter downspouts from main roof may be used with safety. When a drainage system is proportioned for disposal of sani- tary wastes only, the office employs the following data : PLUMBING, DRAINAGE AND WATER SUPPLY 141 Connection Inches a,ter-oloset 4 Dhon jet slop sink 4 dinary slop sink and floor drains and stall type urinals 3 tchen sink 2 phon jet urinal bowl 2 ower-bath 2 tth-tub 11 Qgle lavatory IJ vo to twelve lavatories 2 e box floor drain 3 ximum number of water-closets to connect to various size Nuniber of pipe water-closets 12 24 42 70 105 200 355 all fixtures in number not exceeding twice the number of -closets given above may discharge into the lines without ze being increased. the event a separate rainwater disposal system is to be de- i with no sanitary connection or area drain connections near lent floor the following tables may be used with safety: Diameter of pipe in inches Area of roof ' with ^ inch falJ Square feet per foot 2,200 4 3,500 5 5,000 6 13,500 8 19,000 9 31,000 10 51,000 12 Diameter of pipe in inches Area of roof with } inch fall Square feet per foot 2,500 4 4,500 5 8,000 6 18,000 8 41,000 10 69,000 12 142 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS One-quarter of an inch per foot is the standard grade for which recessed drainage fittings are pitched, but this can not be obtained in fireproof buildings when pipes are run in floor construction, and said pipes are run practically level and give good service. When a combined system of sewers is in use in a city, it is im- portant to protect the fixtures located in the basement of the Fed- eral building from overflow which may result from backing up of the city sewers. This is accomplished by connecting the drain pipe serving the basement flxtures independently to the main house drain and installing near the point of junction a back-water valve and a hub-end gate valve on the basement toilet-room drain. Then if city sewer backs up the basement fixtures may be cut off and the roof-water continue to enter city sewer, and the fixtures on the upper floors be kept in use. A |-inch diameter vent pipe is taken from the back-water valve or near same, and connected near ceiling of basement to a vent pipe so as to relieve the piping system of air when the back-water valve closes. The back-water valves are specified to stand open normally. Base- ment window areas are protected with back-water cesspools, or back-water traps. Under adverse conditions, where city sewers are inadequate and overflow constantly, or where the fixtures in basement must be located below any city sewer, then the "Shone" or equal type of sewage ejector is used, together with a motor-driven air com- pressor and air tank for the purpose of automatically discharging the low-level sewage into the city sewers. These devices have proved most satisfactory in service, with practically no shut- downs for repairs. Where sanitary sewers exist in a city, or a cesspool or septic tank is in use and there are no sewers for the disposal of rain water from roof, the roof-water is discharged on the surface of the ground. As a general rule, the discharging of roof-water on driveway in rear of building is prohibited on account of danger to horses dur- ing freezing weather. The down-spouts are nearly always brought down on inside of building and discharge on drip stone or a grass plot, or enter rectangular cast-iron gutters set in sidewalk with covers flush with surface of walk. These cast-iron gutters dis- charge into street gutters. In all cases where downspouts are collected in the roof space or PLUMBING, DRAINAGE AND WATER SUPPLY 143 unheated attic, the pipes exposed in said space are covered 2 inches of hair-felt with a canvas jacket to prevent freezing, len the local engineer who prepares the survey reports that id water exists within 8 feet of the surface of the site, the ice of the office is to install around the exterior of the build- n. agricultural or subsoil drain consisting of 4-inch-diameter lazed earthenware hub sewer pipe laid at a grade of J inch nch in 10 feet and surrounded on bottom with a 3-inch bed in both sides with a 6-inch bed of gravel or 2-inch broken . This stone or gravel fill is carried up to within 1 foot of and covered with hay or burlap, and then sodded over, mmmit of the agricultural drain is made not less than 3 3 below basement floor, and the joints in the pipe are ited on the bottom and half way around to maintain a chan- The upper part of the joint is open and covered with a of burlap. 3 agricultural drains discharge into a brick manhole 3 feet iter with concrete bottom and manhole cover similar to a ir city-sewer manhole. The inlet pipe to manhole is pro- with a cast-iron quarter-bend, turned down to form a seal and prevent sewer air entering the sub-drains. The i pipe is provided with a back-water valve, and said pipe ne'cted to the building sewer. local and state ordinances do not apply inside the Federal .e, the office is not hampered thereby in the design of plumb- id drainage systems, but outside the property limits com- mth local regulations, such as those which prohibit discharg- of -water into sanitary sewers, or which require the installa- f a running trap on main house drain. The office is strongly ed to the last-named device, and installs it only under pro- i towns which continue to cling to this antiquated expedient. les are frequent where only sanitary sewers are in use, and lecessary to drain into same the small basement entrance vindow areas. Permission to do this is always readily ;d by the local authorities. , basement entrance or window area is to be connected to ■ainage system of building under basement floor, a cesspool lit a bell trap is placed in the area and the pipe connection ught into the building below basement floor and provided 144 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS with a running trap with clean-out screw flush with basement floor. This trap prevents water being held in the cesspool and freezing (as with the common cesspool with bell trap), and also prevents the escape of drain air at this point when cesspool covers are removed. If the area cesspools connect to a drainage system located on exterior of the building, as may be the case where separate storm- water sewers exist, the bell trap is omitted as before noted and a "P" trap is used at base of the vertical from the cesspool pipe. As early as 1892 the writer urged upon the office the adoption of the end-vent or circuit system of plumbing, originated by Wil- liam Paul Gerhardt, and also strongly advocated the omission of a running trap on the main house drain. The ofBce accepted both improvements about 1894 and has used them continuously since that time with great success; and its example has undoubt- edly had much weight in bringing about a wide adoption of the end-vent system and the consequent abandonment of the com- plicated back-venting systems. In the early days of this advancement the office met with much criticism from local inspectors in various small towns where Fed- eral buildings were being erected, but protests along this line are now so infrequent as to indicate that ancient history has been abandoned as a guide in the practice of plumbing. In the end-vent system the soil pipes are extended up above the roof full size, as are the dead-end vents in most cases, and no traps are placed at the foot of the interior downspouts unless they open within 20 feet of a window. The mains are carried close to the fixtures, and the dead ends to fixtures do not as a rule exceed 6 feet in length, which is equiva- lent to a developed length of 10 feet. These short dead ends re- ceive sufficient oxygen to maintain the bacteria active. The omission of the running trap and the generous size and number of vent pipes extending above the roof serve to create a positive current of air from the city sewer through the plumbing system and thus help to ventilate the city sewer, a very desirable feature. It is of interest to note that if a cleanout plug is removed on one of these systems at the base of a soil or waste stack, a strong and continuous current of air from the room into the pipe will be observed. PLUMBING, DRAINAGE AND WATER SUPPLY 145 )hon-jet water-closets and urinals are used exclusively. All 1 on other fixtures are non-siphoning, except the floor drains shower-bath stalls, which are always end-vented for protec- against siphonage. [ soil, waste, vent, and drain piping below basement floor. From building to cesspool, septic tank, or city sewer (if the [■ is within 200 feet of the building), is extra-heavy cast-iron md-spigot pipe with lead-caulked joints, either coated or un- :d. The fittings thereon are extra-heavy to correspond to No pipe below basement floor is less than 2-inch diameter, janouts are used on horizontal runs below basement floor and )cated in brick or concrete manholes with iron covers set flush basement floor. These cleanouts are located so that the g system may be rodded to clean obstructions, and they are ed not over 40 feet apart on straight run^. ass screw-jointed cleanout plugs are located at the base of ;rtical soil waste, aaid vent pipes, ajid at base of all vertical spouts where same are connected to the drainage system } the basement floor. Similar cleanouts are used on hori- d soil and waste pipes in toilet rooms above the basement. soil, waste, and vent piping and all interior downspouts 3 the basement floor are made of standard galvanized wrought or mild-steel pipe with cast-iron, recessed, screw jointed, nized drainage fittings. brass pipe on sewer side of traps is iron-pipe size and thick- and on fixture side of traps is brass tubing, iter-supplying piping exposed in toilet-rooms on face of le work and at fixtures is nickel-plated brass pipe, iron-pipe nd thickness; ajid all other water piping is standard galvan- yrought-iron or mild-steel pipe. If demanded by the char- of city water, brass pipe or lead-fined iron pipe is used. valves are standard weight; 2-inch and smaller are brass, arger are iron body. running threads or long screws are permitted in jointing ipe, and in lieu of same all-brass ground-joint unions, flange s, or right-and-left couplings are used. No provision for Lsion is made in any piping except hot-water piping over 100 jng. 146 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS UNIFORM PLUMBING SPECIFICATION About two years ago the Treasury, War, and Navy Depart- ments decided to cooperate in designing a complete line of plumb- ing fixtures, and to require their respective contractors to furnish fixtures in strict accordance therewith. The result is the gov- ernment publication entitled "Specification for Plumbing Fix- tures, etc., for the Treasury, War, and Navy Departments," which may be obtained from the Superintendent of Documents, U. S. Government Printing Office, Washington, D. C, at 35 cents per copy. The board which prepared this specification has produced a document remarkable for both scope and accuracy, and has ren- dered a substantial service to sanitary engineers and to the manu- facturers in this line of business. Engineers and architects who have had to hear and weigh the claims and counter-claims of rep- resentatives of various plumbing-material houses will undoubtedly appreciate the relief which the standardization brings. The Treasury Department's representative on the board was Mr. H. M. Price, Mechanical Engineer, Office of the Supervising Architect. The following is a brief description of the line of plumbing fix- tures in general use in buildings under control of the Treasury Department : All fixtures (except wash sinks in boiler room) are required to be extra-heavy vitreous earthenware of rugged design. Closet bowls are required to weigh not less than 54 pounds in any case, and in some cases not less than 75 pounds. The closet must be capable of passing the ink test in regard to flushing. This test requires that the interior surface of the bowl from water line up to flushing rim shall be smeared with ink, and that upon flushing closet the water level in the bowl must not rise, and it must be clearly demonstrated that the flush is reach- ing all parts of the bowl surface above the water line. The closet must also be capable of discharging with one tank full of water 32 sheets of toilet paper spread out on the floor and one end balled up and placed below water line of bowl. The same number of sheets (loose) lightly balled up and dropped into bowl must also be readily cleared out with one discharge of the tank. PLUMBING, DRAINAGE AND WATER SUPPLY 147 3p sinks are of the siphon-jet type with flushing rim molded le bowl, and are supplied with flushing tank and with com- fcion hot and cold water faucet. ■inals are siphon-jet type so designed as to contain a body of r in the bowl. For economy in water consumption, pull tanks constructed similar to water-closet tanks are used on lis. ivatories are made with overflow molded in the bowl, and provided with the ordinary brass chain and rubber plug, closing faucets have not proved entirely satisfactory, and the Her" or compression type of faucet is used, ith tubs are cast-iron, enameled inside and painted outside, not less than 5 feet long and 24 inches wide, with roll rim, ire provided with combination faucets and non-siphoning trap, with either a standing overflow, or a common overflow and iss chain and rubber plug. 1 flre hose is 2-inch diameter, unlined, woven linen, Under- ;rs' hose, with 75 feet of hose to each outlet. Each length of has a 12-inch long brass nozzle with |-inch opening and nec- ■y couplings, and is mounted on a first-class hose rack which ;^s hose to hang in vertical loops. le shower-baths have a 5-inch diameter adjustable head, and »rovided with a mixing valve so designed as to prevent scald- he bather. Floor drains for showers are cast brass, with re- ible bar strainer cover not less than 5-inch diameter. 1 urinal stalls, shower-bath inclosures, and water-closet in- res are light-colored marble, l|-inch thick. 16 floor of toilet-rooms are terrazzo, with marble border ig a sanitary cove cut in same. Marble wainscot |-inch : is used in all toilet-rooms. Height for main toilet-rooms is t, and 4 feet 6 inches for private toilet-rooms. Window and trim in toilet-rooms is marble. le minimum size of a private toilet-room in Federal buildings "eet 6 inches x 5 feet, which allows for the installation of a r-closet and a lavatory if entrance door is properly arranged ookout ladder does not interfere. A larger room is provided 3sible. ilet-rooms which are intended to contain a bath-tub, water- t, and a lavatory are made 5 feet 6 inches x 8 feet 6 inches, if 148 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS entrance door can be properly placed. Five feet by 8 feet is con- sidered the minimum for first-class work. Water-closet inclos- ures for men are generally made 2 feet 9 inches to center and 5 feet deep. Inclosures for women are generally made 3 feet clear inside and 5 feet deep, and inclosure and entrance door extend to within 6 inches of the floor lines. Wherever possible, a retiring-room is provided for women in connection with their main toilet. Main toilet-rooms are made as large as a due regard for economy will permit. It is a practice to screen toilet-rooms opening off corridors so that occupants will not be within view when entrance door to toilet-room is opened. All toilet-rooms are provided with win- dows in exterior walls in order to obtain light and air. In the carriers' toilet-room of a Federal building the minimum number of water-closets provided is three; and in this room are also installed a slop sink, a shower-bath, and at least one urinal and one lavatory. The proportioning of fixtures in a Federal building is solely a matter of judgment and experience, but as a rule one closet to ten persons is allowed in the smaller buildings, and one closet to from thirty to forty persons in the large buildings, similar to school-house practice. The number of urinals never exceeds one-half the number of water-closets, and the number of lavatories is reduced to a mini- mum, generally nor more than two being provided in a large toilet- room. A slop sink is provided in connection with or adjacent to the first-floor lobby, and also in all main toilet-rooms except those assigned to women. Lavatories are provided in each oflfice room if the appropriation for the building permits. In the Philadelphia post office one general toilet-room contain- ing 22 water-closets, 12 urinals, and 15 lavatories was provided for from seven hundred to eight hundred employees, and proved satisfactory. A women's toilet room is always provided in the post-office sec- tion of a building, and if building is two stories high or over a women's toilet-room is also provided on one of the upper fioors, in the most inconspicuous place possible. PLUMBING, DRAINAGE AND WATER SUPPLY 149 e following report contains valuable basic data upon the sub- if proportioning plumbing fixtures to occupants of buildings: RT OF COMMITTEE ON TOILET REGULATIONS FOR INDUSTRIAL PLANTS rsuant to instruction, the committee appointed by the chairman of mitary Section of the Boston Society of Civil Engineers to consider igulations for toilet facilities in industrial establishments, has com- l its study and submitted its recommendations in a report from the following paragraphs are abstracted: every establishment where persons are employed, there shall be pro- within reasonable access a sufficient number of proper water-closets, closets or privies, and wherever ten or more persons of both sexes iployed together, separate water-closet compartments or toilet rooms be provided for each sex, and shall be plainly so designated, e number of seats shall not be less than one to every twenty-five and one to every twenty-five females, based upon the maximum er of persons, of either sex, employed at any one time, except that I urinals are provided, the number of seats required may be decreased e for each urinal installed; but the total number of seats, however, not be less than two-thirds the number required above. ,ter-closets and urinals must be readily accessible to the persons us- lem. In no case may a closet be located more than one floor above ow or more than 300 feet distant from the regular place of work of the a using the same. water-closets which are not ventilated directly to the outside air window, skylight or other opening shall be entirely enclosed in a irtment or toilet room, either by extending the side walls to the ceiling independently ceiling them over at a minimum height of eight feet. 3ompartment or toilet room shall then be ventilated by either: An exhaust system; or A stack to the roof at least six inches in diameter, lerever practicable, these toilets shall be relocated so that they will "be ed directly to the outside light and air, in accordance with the re- ments for new installations. ery toilet-room or water-closet compartment shall be so lighted that rts of the room or compartment are easily visible at all times during ng hours. If daylight is not sufficient for this purpose, artificial nation shall be maintained. all water-closet compartments hereafter constructed, there shall be ,st 10 square feet of floor space and 80 cubic feet of air space per [ or seat installed. water-closets shall be provided with ample power for flushing. water-closets hereafter installed shall have individual bowls made rcelain or vitreous earthenware; they shall be provided with seats 150 MECHANICAL EQUIPMENT OF FEDBBAL BXTILDINGS made of wood or other non-heat-absorbing material, which shall be coated with varnish or some other waterproof substance. All woodwork enclosing the bowl of the closet shall be removed and the space within the compartments shall be painted with some light-colored non-absorbent paint. Hereafter, when more than one water-closet is installed in a toilet room, partitions shall be provided between the seats. These may be of wood if covered with paint or some other non-absorbent material. They shall be not less than six feet high, and, where practicable, shall not ex- tend nearer the ceiling or floor than one foot. They shall be at least 28 inches apart. The floor of every water-closet compartment or toilet room hereafter installed, and the side walls, to a height of 9 inches, shall be constructed of material impervious to moisture, and having a smooth surface. The floors of all water-closet compartments and toilet rooms shall be kept in good repair, and free from large cracks or holes. All water-closet compartments hereafter installed in men's toilet rooms shall be provided with doors at least three feet in height and they shall be hung 24 inches above the floor. All compartments used by females shall be provided with doors at least 42 inches high and furnished with suitable fasteners. The use of the iron trough type of urinal is prohibited, and all urinals shall be made of impervious non-corrosive materials, shall be individual, and preferably of the wall or vertical slab type. Where more than ten males are employed a urinal hall be provided; urinals shall be provided in the ratio of one urinal to every forty males, based upon the maximum number of persons employed at any one time. Two feet of wall urinal shall be considered as an equivalent of one urinal. The floors shall be constructed of impervious material to at least 24 inches distant. It is recommended that all water-closet compartments and toilet rooms shall be kept heated during the working hours to at least 50°F. All toilets and urinals shall be kept clean . Regular and thorough cleans- ing shall be practiced. Disinfection alone is not to be relied upon. In every establishment there shall be one person who shall have direct charge of and be held responsible for the cleanliness of all sanitary appliances installed. In every establishment where persons are employed there shall be pro- vided, within reasonable access, a sufficient number of proper washing facilities, and where ten or more males and ten or more females are em- ployed together, separate washing facilities shall be provided for each sex, and shall be plainly so designated. The number of wash bowls, sinks or other appliances shall not be less than one to every thirty persons, based upon the maximum number of persons using the same at any one time. Twenty inches of sink will be considered as an equivalent of one wash bowl. PLUMBING, DBAINAGE AND WATER SUPPLY 151 special industries or departments where there is undue exposure sonous substances or liquids, or where the work is especially dirty, lay be required for every five persons, and in these cases they shall jvided with clean, running hot and cold water. e washing facilities provided must be within reasonable access as : defined for toilets, and at least one wash bowl, sink or other suit- ippliance shall be provided in or adjacent to every toilet room, washing facilities shall be clearly lighted at all times during working washing facilities or appliances and the floors in and around the same be kept clean, and regular and thorough cleansing shall be practiced. layimg out chases for the reception of the plumbing piping ches of solid wall is left at the back of the chase in exterior and 9 inches in interior walls. nimum depth from plaster hne to back of chase : 8 inches for h and 6-inch pipes, 6 inches for 3-inch and 4-inch pipes, and hes for pipes smaller than 3 inches. dth of chases: 12 inches for two 4-inch pipes, 8 inches for -inch or 5-inch pipe, 8 inches for two 2-inch pipes. No chase ide less than 8 inches unless structural conditions demand, lich event a 4J-inch chase is made for one •2-inch pipe. I chase is placed closer than 9 inches to a beam bearing, nor [• than 15 inches to a girder bearing, nor closer than 12 inches y window or other opening. iless architectural reasons prevent, all soil and waste pipes an exposed at ceiling of room below toilet-room. . water pipes are run exposed in toilet-rooms, none being d in floor or walls. e raising of toilet-room floors to conceal piping is not re- d to unless the conditions absolutely demand that action. WATBE SUPPLY )st of the cities in which Federal buildings are erected have t-class water-supply system, serving water of a good quality it a pressure sufficient to supply all fixtures provided; and iroblem of water supply for the building is therefore merely )roportioning of piping to supply the fixtures and the fire len the normal city water pressure is in excess of 50 pounds, lere the mains are subjected to high pressure during fires, a 152 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS pressure-reducing valve is installed in the building to protect the plumbing fixtures; and the street washers and fire hose are con- nected to the main supply pipe between the street main and the pressure-reducing valve. In towns where there is no water-supply system, or where the water is of poor quality, careful investigation is made for the purpose of ascertaining whether it is feasible to sink a deep well from which all the water required for the building can be obtained. Such wells are usually installed by local contractors, who are re- required to guarantee a certain delivery during eight hours con- tinuous pumping. When there is much sand in the deep-well water, as in Texas and on the Pacific coast, the well is operated by an air lift, or the deep-well pump discharges into a cistern to allow the sand to de- posit. From this cistern the triplex house-pumps take suction, and they discharge into riveted steel receivers of not less than 800 gallons capacity. The old style of open-roof or attic storage tank is not used in Federal buildings except when conditions absolutely demand, as when the city water pressure is low during the day and can not supply the fixtures on the top story, but rises during the night sufficiently to fill an attic tank. Under these conditions the daily city water pressure is utilized to supply all the lower floors, and the upper floors are supplied by the tank without the neces- sity of pumping. The requirements for fire protection for any Federal building practically govern the size of the main water-supply pipe, which is never made less than 2-inch diameter. For the smaller build- ings it is assumed that only one line of fire hose will be in service at any one time, and for large buildings that all fire hose on one floor will be operated simultaneously. The area of a 2-inch pipe is allowed for each fire hose in service, and the main supply pipe to the building is made of a discharging capacity equivalent to the selected number of 2-inch pipes. While the main water-supply pipes are approximated on the fire-protection service when the city water pressure is sufficient to supply all fixtures in the building, fire-protection requirements do not govern when a pumping plant must be installed, as the pumping plant is proportioned for the supply of the plumbing fixtures only. PLUMBING, DRAINAGE AND WATER SUPPLY 153 some Quarantine Stations pumps and piping are installed re protection only, and then the following basic data are used oportioning the system : essure at hydrant, 32 pounds; 90 gallons of water per minute; Feet of 2-inch hose with |-inch nozzle. ider the above conditions the nozzle will throw water 50 horizontally and vertically, necessitating the spacing of hy- ts 300 feet apart. The buildings at Quarantine Stations are im more than 40 feet high, and usually there are not enough idants to care for more than one hose stream at a time. The ig is proportioned to keep the friction losses within a reason- limit, and 2-inch hose outlets are usually provided, iplex pumps driven by gas engines are used for fire protec- at Quarancine Stations. The size of gas engine is ascertained lultiplying the number of gallons of water per minute by the sure at hydrant plus all friction losses (which are never less 50 per cent of pressure at hydrant), and dividing the result 00. here fire-protection service requirements do not govern, the Df main service pipe is based on the assimaption that the maxi- 1 consumption of water will be at the rate of 500 gallons per for each water-closet, urinal, shower-bath, lavatory, sink, wall hydrant. terminal pressure of 8 pounds per square inch, should be itained at the highest fixture, and the drop in pressure in main ce pipe (assumed to be 100 feet long) must not exceed 10 feet . With this loss — Size of service Velocity in feet per second Gallons in 24 hours i 4 3,000 i 4 5,000 3 4 5 7,200 1 44 16,000 If 4 28,000 14 5 42,000 2 6 86,000 2i 6i 144,000 le above table is sufficiently accurate for all practical purposes, here the city water pressure is low, say below 30 pounds per re inch, the piping is laid out and the pipe sizes carefully cal- 154 MECHANICAL EQUIPMENT OF FEDEBAL BUILDINGS culated with this in view. If a water filter is to be installed it is charged with a loss of pressure of five pounds Practice has fixed the size of branch water-supply pipes to the various fixtures as follows: Inches Water-closet flush tank i Urinal flush tank J Slop sink flush tank J Slop and other sinks f Shower-baths i Bath-tubs i Lavatories i Street washers i Small heating boilers and hot-water heaters i The branches to toilet-rooms containing three or a less number of fixtures are made f-inch diameter; more than three and not more than nine fixtures, 1-inch diameter; more than nine and not more than twenty-one fixtures, IJ inch diameter; and for from twenty-two to thirty fixtures, l|-inch diameter. The proportioning of branch water-supply pipes is a matter of experience and judgment, as it is based not only on the number of fixtures in the various toilet-rooms and on the group of toilet- rooms served by one branch or riser, but also on the number of fixtures that will be used simultaneously, a difficult matter to determine, accurately. As previously stated, the branch connections to fixtures are fixed by practice, and certain conservative sizes are established for branches to toilet-rooms containing various numbers of fix- tures. The general practice is to allow, when flush tanks are used, that a |-inch diameter pipe will serve any fixture, and in calculating the proper size of the branch main to a toilet-room, or of a riser to serve a group of toilet-rooms, it is assumed that from 25 to 50 per cent of the fixtures will be used simultaneously. The area of a |-inch pipe is allowed for each fixture so used, and the branch is selected from an "Equalization of Pipe Area" table. In a toilet-room containing eight fixtures with 50 per cent used simultaneously this would give the equivalent of four f-inch pipes, or a 1-inch branch. With twelve fixtures the branch would be Ij-inch and with 50 per cent of the fixtures in use simultaneously a If-inch pipe would serve thirty-two fixtures. PLUMBING, DRAINAGE AND WATER SUPPLY 155 • a very large toilet-room with many fixtures the branch ihould be not less than IJ inches, and not exceeding 25 per )f the total number of fixtures installed should be considered ing used simultaneously. • the calculation of branch supply pipes the water consump- if water-closets is well established. The standard flush tank 7 feet above the closet, and under ordinary operating condi- it will discharge twenty gallons of water per minute into the ipe. The water consumption of urinals, lavatories, etc., is at one-half that amount. 3 following table may be used in proportioning the piping flushometers are to be used : WATEE-OLOSETS URINALS HE Number of Closets Size of Main Size of Valves Number of Urinals Size of Main Size of Valves Is inchea inches inches inches 1 n 14 1 1 1 3 2 2- 3 u 6 24 4- 6 14 1-2 14 U 1- 2 1 3 4 3- 8 2 3- 8 11 9-16 24 9-12 14 1- 4 14 n 1- 3 1 i 5-14 2 4-10 U 15-24 24 11-16 14 3 sizes given above are sufficient to supply all fixtures in a -room with cold water, and no additional allowance need be for lavatories, sinks, etc. shing valves are not used except in the large buildings, nor i the normal city water pressure at the highest fixture is less 10 pounds; and generally the limit is made 15 pounds to large pipe sizes. ,ter filters are used only where the conditions absolutely de- them. The specifications for filters to be used where water y muddy require the maximum rate of filtration to be four IS of water per minute per square foot of filter area, and in ly muddy waters to be six gallons per square foot per min- Under the conditions noted above, with city water of nor- 156 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS mal turbidity, during the test the filter must dehver the amount of water specified, and at the end of an eight -hour run the filtrate must be clear and must not contain free alum or any other coagu- lant used. During the eight-hour test the filter must not require washing, and the drop in pressure of water passing through filter must not be greater than five pounds. The filter must be easily operated, with as few valves as possible ; and when reversing the flow to wash the filter the bed must not be carried out through the waste pipe. The filter bed must be not less than 2 feet 6 inches deep, com- posed of clean, sharp, quarried granite or quartz ground to the proper fineness. Sea or river sand in the filter is not permitted. Two units are always installed, each a complete filter, and so fitted that the units may be used singly, in parallel, or in series. Filters are not used where the entire water supplj^ of the city is filtered. " In proportioning filters, deep wells, and pumping plants, the number of occupants is ascertained for any given building, and the water consumption is based on a rate of 100 gallons per day per capita. Where the number of occupants cannot be ascer- tained with any accuracy, the rate of water consumption is based on 500 gallons per day for each plumbing fixture. This rate is established to cover the maximum demand on the system. In the Philadelphia post office the city water pressure was suf- ficient to supply only the fixtures in basement and on first floor. The fixtures above first floor, numbering 140, had to be supplied by pumps, and on the basis given above this required 50 gallons of water per minute. Two triplex pumps, one 3-inch x 4-inch and one 4-inch x 4-inch, with a combined capacity of 50 gallons per minute, were installed. These discharged into a steel receiv- ing tank 60 inches in diameter and 10 feet high, in which was re- tained a body of air. These pumps have successfully supplied the fixtures for years. In the Toledo post office a deep well was installed, with a ca- pacity based on the installation of 68 plumbing fixtures to serve 300 occupants. On the rules previously given this would require 34,000 gallons a day for fixtures, and 30,000 gallons a day in the per capita basis. A mean of the above would require approxi- mately 22 gallons per minute. PLtTMBING, DEAINAGE AND WATEE SUPPLY 157 le well is 8-inch diameter and 502 feet deep, and on test de- ed 25.8 gallons of water per minute. Before pumping, the ir in the well stod 128 feet below the surface of the ground, and • pumping eight hours at the rate above noted it fell to 168 rising again when pumping ceased. pump 3|-inch diameter by 24-inch stroke was installed, which 5 revolutions per minute delivers twenty gallons of water per ite into a tank against 30 pounds pressure. The pump was ated by a deep-well pump head driven by a 5-H.P. motor, inch cylinder with 4-inch-stroke air compressor was installed, sn by a 3-H.P. motor, and discharged into a galvanized-steel itorage tank with a connection to the air space of the main sure tank. tie air tank was 18-inch diameter and 5 feet long, with j^-inch . and j-inch heads, and the compresson tank was 60-inch di- ter, 26 feet long and constructed with -j^-inch shell and j^- dished heads. Rivets were |-inch diameter, spaced 2| inches er to center. Tank was tested to 100 pounds. !ie gauge glass was 24 inches long, and the tank was provided a 11-inch x 14-inch manhole located below the water line. tie calculation of the horse-power on the usual basis shows with deep-well pumps considerable allowance must be made Lotor for the weight of the suction rods in spite of the buoy- ' of the water. tiirty pounds in tank plus 168-foot lift equals approximately pounds. 20 X 110 , „ , , , — — -— — = 1.3 actual horse-power. 1700 ^ iking the pipe friction at 50 per cent of the 110 pounds would ire 20 X 170 1700 = 2 horse-power. lowing 50 per cent efficiency on working head and 80 per on motor, the combined efficiency would be 40 per cent, and motor horse-power would be 2 divided by 0.4, which equals rse-power. Western cities where the water is strongly alkaline it is the tice to install a rain-water storage cistern in the basement, 158 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS and by means of a watei-lift or pump elevate this water into a storage tank in attic, thence supplying the water for lavatories and slop sinks, and for drinking purposes, the flushing of sanitary fixtures and sprinkling of lawns being done with city water. An excellent example of an installation of this character is in the Federal building at Mitchell, South Dakota. The city water pressure was over 60 pounds, which made a water-lift preferable when relative cost of city water and of electricity was considered. The roof area discharging into storage cistern in basement is 3600 square feet. The cistern is 15 feet x 18 feet inside dimensions, divided into two compartments by means of a 9-inch brick wall with openings at floor of cistern. On the floor of cistern and 12 inches on each side of the division wall, 4|-inch-thick brick walls are erected to a height of 16 inches, and the space between these walls is filled with a layer of charcoal 12 inches deep and covered with a 4-inch bed of sand. The filtered-water compartment from which the water-lift takes suction is 4 feet 5 inches wide and 15 feet long. The downspouts discharge into the large compartment. The cistern was constructed on top of the 5-inch-thick concrete basement floor, and the bottom of cistern was constructed of a layer of water-proofing, 5 inches of concrete, and 1-inch cement mortar finish coat. The distance from basement floor to top of side walls of cistern is 6 feet, and the side walls are 4-inch-thick brick walls plastered with 1-inch cement coating, then a layer of waterproofing, and then a brick wall with a batter on the exterior, thickness at top 24 inches and at bottom 36 inches. The entire cistern is covered with 2-inch x 8-inch wood joists, 1 foot 10 inches on centers, the joists being covered with IJ-inch tongued and grooved boards. Hinged trap doors 24-inch x 36-inch are placed for access to stor- age portion and filtered-water space. Minimum space between bottom of first-floor construction and top of cistern is 2 feet 6 inches. The water-lift has a capacity of 600 gallons of water per hour and is of the reciprocating type, 3-inch power cylinder by 3-inch pump cylinder with a 4-inch stroke, and delivers the water into the attic tank with 60 pounds city pressure. The pump governor is so designed that the admission of city water is regulated by the PLUMBING, DRAINAGE AND WATER SUPPLY 159 ire in the lift discharging pipe to attic tank, and when the is stopped the valve closes and pump is not under pressure. )unip has a Ij-inch city water connection and a IJ-inch irge to attic tank. I attic tank is 3 feet 3 inches x 6 feet 6 inches x 2 feet 3 inches constructed of J-inch tank steel with 2§-inch x 2|-inch corner , and is provided with a drip pan 6 inches larger all around he tank. The tank rests in the pan on three 6-inch I-beams, le pan is supported on three 8-inch I-beams. The tank is led with a |-inch tongue and grooved cover, and inlet to ;s provided with a ball cock. ere space permits, the attic storage tanks usually hold about gallons, and for the average Federal building the cistern in lent should have a capacity of not less than 10,000 gallons. ! size of the storage cistern is generally based on containing lonth's rainfall, assuming the rainfall to be 48 inches per ir 4 inches per month. At this rate each square foot of roof catch about 2| gallons of water, and in the example just the cistern would be 9000 gallons capacity. ! minimum size of cistern is based on containing one month's ;e at rate of 2 inches of rainfall per month, he quality of city water is satisfactory, but an attic storage s necessary on account of the city pressure being low during ly and increasing sufficiently at night to fill the tank, a 1000- tank (which will generally be 4 feet x 6 feet x 4 feet deep) called, and is provided with a drip pan 6 inches larger all d than the tank. The tank and pan always have an over- basement sink. ik and pan should be constructed of J-inch tank steel, and ,nk should have one longitudinal and two transverse braces h diameter, set 30 inches above bottom of tank. ; water is supplied to each shower-bath, lavatory, and sink 'ederal building. ; hot-water branch supply connections to fixtures are the as the cold-water connections previously described. The ater supply pipes to toilet-rooms containing three or a less er of fixtures requiring hot water are |-inch diameter. there are more than 3 and not more than 8 fixtures a 1-incb ter connection is made. 160 MECHANICAL EQUIPMENT OP FEDERAL BUILDINGS Except in one-story buildings, |-inch diameter return circu- lating pipes are taken from each riser near the top and collected into a |-inch return main in basement. The return main is con- nected with the storage tank and provided with a check valve. Where the cost of gas does not exceed 30 cents per 1000 cubic feet, a storage-type, automatic gas water heater is installed; other- wise a cast-iron coal-burning heater is used. In estimating on storage tanks and hot-water heaters for Fed- eral buildings twenty gallons in the storage tank is allowed for each shower-bath, ten gallons for each sink, and five gallons for each lavatory. In the average one-story and small two-story buildings this will require about sixty-five gallons water storage, or a tank 18-inch diameter by 5 feet long, containing a steam coil made of 15 linear feet of l|-inch copper tubing. The gas water heater to be supplied with the above-described tank must be capable of heating 50° 4 gallons of water per minute. Under ordinary conditions this would heat 50° 200 gal- lons of water per hour. The cast-iron water heater to be supplied with above-described tank has a 12-inch diameter grate and will heat 48 gallons of water per hour from 40° to 140° F., and at this rate will require firing every eight hours. The next size storage tank used in Federal buildings is 24-inch diameter and 7 feet long, containing 164 gallons of water and a steam coil with 25 lineal feet of l^-inch No. 16 copper tubing. This tank will serve two shower-baths, five sinks, and from fifteen to twenty lavatories, and may be used with the gas heater above noted. The coal water heater for the above-described tank has a 15- inch-diameter grate, and a capacity to heat 96 gallons of water from 40° to 140°r. per hour when fired every eight hours. The largest buildings have a storage tank 36-inch diameter by 8 feet long, containing 424 gallons of water and a steam coil con- taining 36 lineal feet of 2-inch O.D. No. 16 copper tubing. A gas water heated used with th's combination should have a ca- pacity of heating six gallons of water per minute 50° F.; and a cast-iron water heater should have a grate 18-inch diameter, and be rated to heat 220 gallons of water from 40° to 140° F. per hour when fired once in six hours. PLUMBING, DRAINAGE AND WATER SUPPLY 161 general, the storage capacity should be determined by the )ing rules; and in the large outfits the cast-iron heater should signed to heat the amount of water in storage tank in two when the boiler is fired once in six hours. DRINKING WATER SUPPLY the smaller buildings used exclusively for post office pur- , with perhaps a second or third floor containing offices used or of minor importance, and a post office work room of about 2000 square feet or less one drinking fountain is i in the work room and an ice box in the basement, some of the smaller buildings in which the basement is too Dr sewerage facilities in lieu of the drinking fountain and )x a sanitary water-cooler is placed in the post office work ,he work room exceeds about 2000 square feet area two or drinking fountains are placed in it, and if the building con- a court room a drinking fountain is placed in the corridor at floor, which is generally the second. 5 drinking fountains are of a type hereafter described. The ype are generally used in both work rooms and court room ors, except in cases where there are a number of fountains work room when only those adjacent the offices and in por- of the rooms where women may be employed are made wall md the others in the work rooms are made pedestal type. ; ice boxes are made 48 inches long by 18 inches wide by 33 s deep inside. They are lined with galvanized iron and 1 heavy rack inches above the bottom on which a 400-pound jf ice may be placed. ow this rack is a coil of |-inch block tin pipe. This coil ins 50 lineal feet of pipe if one fountain is used, and 100 feet if two fountains are connected to it. ! boxes have a valved drain out of the bottom and an over- i inches above the rack which holds the ice. Thus the coil ays submerged. ! box is made of |-inch tongue and grooved hard pine inside utside and on the bottom and sides is insulated with 2 : of granulated cork or cork board between the exterior and 162 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS interior wood linings. The cover is made of double thickness, |-inch tongue and grooved hard pine with 2 inches cork between and is hinged and counterweighted. The coil is connected to the water supply system on the inlet side and the outlet side runs as direct as possible to the fountains. Generally a pressure reducing valve is connected in the supply line to the ice box as the pressure at the fountain must be nicely regulated. The lines from ice box to fountains are insulated with coik cov- ering same as hereafter described for the ice water lines of the larger installations. The sanitary water coolers sometimes used in the work room have a water chamber or coil which is connected to the water sup- ply system of the building and a bubbling cup is attached to the outlet. This bubbling cup wastes into a chamber underneath into which the melted ice wastes and this chamber is connected to the sewer system through a trap. No attempt is made to circulate the lines between the ice boxes and the fountains and the runs are made as direct as possible. When more than two fountains are required a system of me- chanical refrigeration is installed. In such cases consideration is given to the plan of confining the drinking fountains to the post office work rooms, the court room corridors and other semi-public places and making ice water connections to the lavatories in the office rooms and in the private toilet rooms. The alternate plan to this is to install wall type fountains in the corridors on the various floors in lieu of lavatory faucets. If funds are sufficient to place lavatories in the office rooms, and if the rooms are used enough and of sufficient importance, the former plan is favored. When funds are limited, and in old buildings where the cutting and patching item for a large number of faucets would be large, the latter plan is resorted to but not favored. There follows a description of the systems of ice water supply in which the water is cooled by mechanical refrigeration. PLUMBING, DBAINAGE AND WATEE SUPPLY 163 HBFRIGERATION le refrigeration plants designed and installed by this office generally small plants for cooling the drinking water for the pants of the building. large buildings where there are many water coolers to be each day and kept clean, thus entailing considerable expense ce and a large amount of janitor service, such plants are a iive economic gain; to say nothing of increased convenience to jccupants. ich- plants generally consist of a compressor, generally motor 5n; a condenser, generally of double pipe reverse current ; a cooling tank in which a refrigerant coil is immersed and an ivater circulating pump, generally a motor driven triplex p; in the basement. A system of ice water supply pipes are it the basement ceiling connecting with supply risers passing brough the building and to the attic where they are collected ther in a system of piping similar to that at the basement ig and run and connected into the bottom of a tank called a ticing tank, om the side of this balancing tank near the top an overflow is connected and carried down to the basement and dig- ged into the cooling tank through a perforated pipe extending nd the circumference of the tank just above the water line. stems. The specifications permit either the ammonia, car- dioxide or ethyl-chloride systems to be used without any irence for any particular one. The contractors so far have rally installed the ammonia systems. )mpression systems are specified, and in the ammonia systems, the compact self contained outfits, and the ordinary outfits hich each part of the apparatus is a separate piece of equip- :, are permitted. certain cases such as hospitals the ammonia type of ma- 3S are not used. impressors. Except in a few cases, where unusually large lines are used, the compressors are required to be vertical, e acting, single or double cylinder, of the enclosed crank case ity. No stuffing boxes are permitted except on the crank ;. Such machines are required to be splash oiling and have 164 MECHANICAL EQUIPMENT OF PEDEBAL BUILDINGS an oil gauge and an oil pump is supplied and attached to the ma- chine. The covers of the crank case are required to be ground to a perfect fit without any gasket being used. Rotary compressors are permitted if ethyl-chloride is to be used as a refrigerating medium because the pressures are low. The difference in pressure between the high and low is only about 25 pounds under ordinary conditions while the pressure difference for ammonia is 150 to 175 pounds and for carbon dioxide very much more than for ammonia; generally about 800 pounds per square inch. The usual structural features of machines are embodied in the specification, which does not attempt to give the cylinder dis- placement, size, etc., leaving that for the manufacturer. The machines are specified to be of a capacity sufficient to abstract a stated number of B.t.u. per hour from the water in the cooling tank when the tank is supplied with water at 75° and cooled water drawn off at about 40°. All losses in the plant up to this stage are charged against the compressor. Compressors are generally belt driven but often space requires them to be chain driven from the motor, in the latter both being mounted on a cast iron bed plate. No outfits of less than two tons refrigerating capacity (22,000 B.t.u. per hour), at the cooling tank are used. It is good policy to use machines of ample capacity and large cooling tanks for storage purposes. In this way the machine can run a few hours a day, when some one can take care of it and the circulating pump can be safely intrusted to run constantly without unusual attention. The machines are not required to be automatic; that is, to have an automatic method of starting and stopping to keep the water in the cooing tank at a predetermined temperature. Condensers, separators, etc. The refrigerant condensers are placed in the basement near the compressor, and except for the self contained types of machines, are the double pipe reverse flow type. They are made of IJ-inch and 2-inch extra heavy pipe with special extra heavy return bend fittings. Water supply and waste connections are provided to take care of 3 gallons per minute per ton of rated refrigeration capacity. PLUMBING, DRAINAQB AND WATER SUPPLY 165 le lineal feet of pipe required for these condensers is given in )le hereafter. I separators, liquid receivers, etc., are required to be of ample and properly connected in the usual manner. ?auge board is mounted in some central location on which are id gauges for the high and low side of the compressor and for fater pressure at the circulating pump discharge. cling tanks. The cooKng tanks are made liberal in size to ide storage capacity. They are cylindrical, open top and i generally of i^-inch galvanized sheet steel riveted and all 3 tinned and soldered. le table given hereafter gives the size of cooling tanks used ifferent size machines. le tanks are set on double layers of 2-inch thick cork board in asphalt, which in turn stands on a concrete foundation 4 !S above the floor. The sides of the tank are lagged with ne and grooved hard pine or hardwood filled and varnished. 8-inch space between the tank and this lagging is packed •pure granulated cork. The top consists of double 1-inch pine or hardwood boards between which is placed 1-inch ; cork board. The top is made in two halves and remov- All pipes entering the tank, except the flow and retura ifrigerant which enter through the cover, are entered through ides of the tank and flanges are provided for that purpose, nks are provided with a water supply, generally f inch con- id by a float valve set to keep water line 6 inches below top ak; a drain out of or near bottom provided with a valve and verflow out of side near top, discharging over a cesspool 1 is connected with the sewer system; and a connection top for the return of the circulated water from the balancing in the attic. The suction of the circulating pump is taken the side near bottom of this tank. brass case thermometer is fitted in the suction pipe to the lating pump and a similar one in the return pipe from the icing tank. oling coils. The cooling coil is generally a spiral coil of 2- extra heavy pipe galvanized on outside with welded joints. tie inlet of this coil outside the tank an expansion valve of eedle type is placed and the outlet of this coil is connected 166 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS directly to the compressor suction. The top of this coil is placed 6 inches below the water line maintained by the float valve and overflow. The number of feet of pipe in the cooling coil for the various size plants is given in the table herafter. Circulating pump. The circulating pump is placed as close as possible to the cooling tank in which its suction is connected and the discharge runs to the various rising lines which supply drink- ing water to the various fountains and faucets throughout the building. These pumps are generally motor driven triplex pumps with a silent chain drive, motor and pump being mounted on one cast-iron sub-base. The pumps are designed of proper capacity to circulate sufficient amount of water in order that the return water to the cooling tank will be about 5° warmer than the water leaving the tank which is generally five to ten times the amount of water consumed for drinking purposes. The method of determining this will be given hereafter. These pumps and motors are often placed in duplicate, and this is the only part of the apparatus which it is deemed necessafy in any case to duplicate being the only machine which is presumed to be in operation all the time. By pass arrangements. In cold climate it will often be found that if a by pass arrangement is made to by pass the cooling tank and circulating pump, so that all or part of the water used for general purposes is first passed through the circulating pipes of the drinking water system and thence into the general water supply piping of the building, the refrigerating plant will have to run very little during the winter months. The high non-con- ducting qualities of the covering on the drinking water lines often is sufficient to prevent the absorption of much heat until the water has passed through the drinking water system, whereas often in case of large buildings the water drawn from the lava- tory faucets would be too warm for this purpose. Balancing tank. The balancing tank is placed in the attic and is provided with a tap in the bottom to which the horizontal mains from the top of all rising lines are connected and a tap near the top from which a line is run down to the cooling tank 'in the basement. This tank is generally a closed- range boiler and is covered with PLUMBING, DBAINAGE AND WATER SUPPLY 167 )uble thickness. of 2-inch moulded cork jacket covered with ra.s. It is provided with a hand hole and cover, he size of the balancing tank will be given in a table here- ter. will be seen that this tank provides a free egress for all air le circulating lines and a small water storage in case of short ; down of the circulating pump in the basement. irculating lines. The circulating lines are started from the ip discharge and lead to the base of all rising lines which pass ard through the building, being offset as required to reach the ous fountains and faucets. In the attic the tops of these lines connected together and run to the balancing tank, he ice water lines are galvanized wrought iron or mild steel, ss the character of the water requires some other kind, and fittings are cast or malleable, galvanized. he rising lines are generally made J-inch diameter. Propor- ing the mains is done by adding the sizes of the various rising i together according to the following table: i-mch= 1 lj-inch = 15 f-inch= 2 2 -inch = 30 1 -inch= 5 2i-inch = 55 li-inch = 10 3 -inch = 85 bus a line to supply 10 |-inch rising lines would be IJ-inch after 5 rising lines had been taken off the main is reduced to 3h, etc. be mains in the attic to the equalizing tank are proportioned tie same manner. tie dead end immediate connections to the fountains and ets are made f-inch and generally are iron pipe size brass II lines must of course grade upward from pump to balancing : to prevent air pockets. The overflow line from this tank fc run without traps so that the balancing taiik can be re- id of air through this line. The overflow line is If inches he smaller systems and 2 inches for the larger ones. iverings. This is an especially important item in drinking ■r systems. On an average the refrigeration required to off- he heat losses from pipes, tanks, etc., with even the best prac- 168 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS tice in covering is just about equal to refrigeration required to cool the actual amount of water consumed. In other words the best insulation is only 50 per cent "efficient." All the ice water pipes, valves and fittings are covered with moulded pure granulated cork covering, the commercial thick- ness of which varies from 1| to IJ inches, depending on the size of the pipe. This covering has a mineral rubber lining to resist moisture, special precautions are taken to make the covering con- tinuous through floors, walls, etc., and the hanger bands are placed outside the covering. The covering is applied in halves with joints broken and joints made with a mineral rubber cement. It is jacketed with canvas, pointed to suit and supplied with brass bands. The low pressure refrigerant lines, if they are of considerable length, and ice water lines in hot locations as in boiler rooms, tunnels, etc., are covered with similar covering of the next heavier commercial cork covering, known as "brine covering," similarly applied. Drinking water fountains and faucets. In work rooms, public lobbies or toilet rooms, adjacent to court rooms, and in like places where there are a large number of people to drink water from the same fixture, vitreous earthenware bubbling cup drinking foun- tains are installed. One or two standard types are used, depending on whether or not in the designer's judgment any one would draw water in a ■ glass or pitcher, or whether it is desired to use only the bubbling cup. One designed to be mounted on the wall has a bubbling cup in the bowl and on the back above the bowl is a faucet to fill a glass or pitcher. Both the faucet and the cock controlling the bubbling cup are self closing. The other type is a pedestal type and has only a bubbling cup operated by a foot valve and may be set up at any place in the room. In the wall type the supply connection is made from the wall and in the pedestal type the supply connection is made from the ceiling below. These two types are known among the fixture manufacturers as "Wall type" and "Pedestal type" fountains, Miscellaneous Draw- ing No. 308, Supervising Architect's office. PLUMBING, DRAINAGE AND WATEB SUPPLY 169 1 the larger buildings each lavatory in office rooms is provided I a J-inch self closing faucet. In place of the usual hot and wateo- faucets on opposite sides of the bowl, a hot and cold bination faucet is placed on the right hand faucet location the ice water faucet is placed on the left hand end with a bier holder mounted on the vitreous back. When offices e a private toilet room the lavatory is placed in the toilet room none in the office proper. 1 such cases there is a marble wainscot generally and the lava- T is without back, in which case the tumbler holder is mounted the marble wainscot above the lavatory. If the toilet room no marble wainscot the lavatory with a vitreous back same as he office rooms would be used. This combination is also shown Miscellaneous Drawing No. 308, Supervising Architect's office as such is known to the fixture manufacturers. lethods of calculation. Following is the basic data used in gning the component parts of such an ice water cooling plant las been described. irst locate the lavatory ice water faucets, drinking foun- LS, machinery, etc., and lay out the pipe lines according to the a, given above as to their sizes, etc. Scale up the lengths of different size pipe in the circulating system and compute the u. absorption per 24 hours from the following table; assum- the standard ice water thickness of moulded cork is to be 3. This table gives the heat transfer in B.t.u. -per 2^ hours lineal foot of pipe per degree difference of temperature between •age water and air. 1-inch pipe 3 . 60 li-inch pipe 5 . 26 i-inch pipe 3.84 2 -inch pipe 5.88 1-inch pipe 4 . 00 2i-inch pipe 6 . 98 1 -inch pipe 4.26 3 -inch pipe 7.30 li-inch pipe 4.78 'he temperature of water is generally taken as 40° F. and the temperature is taken as about the maximum likely to be ountered, depending on locality, say about 90° F., on an rage. 'o this result add 10 per cent fto 15 per cent to take care of overed fixture connections, tanks, pump cylinders, etc., and 170 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS you have the B.t.u. per 24 hours required to offset the radiation losses. To get the B.t.u. required to cool the water actually consumed, allow I pint per hour for each occupant who would draw water from a faucet in his own room and 1 pint per hour for each occu- pant who would use the bubbling fountains. Figure on cooling this amount of water from highest probable water temperature, usually about 75°, down to 35°. The smn of these two items is the maximum required duty of the machine and for this duty all parts of the apparatus are designed. In the following table, the basis of which is the B.t.u. loss per hour as ascertained by the above data, are given the dimensions of the principal component parts of the apparatus. It will be noted that the rated tonnage of the apparatus is somewhat in excess of the B.t.u. available for cooling, this excess being in greater proportion for small plants than for larger ones. This is to cover various losses between compressor and tank, possible freezing of some ice on coils, etc. The figures for liquid receiver, oil separator, cooling coil, horse- power, and condenser are for ammonia plants. For other sys- tems such data must be given by the manufacturer to the contractors. ' B.T.U. per hour Rated tonnage B.T.U. per hour for rated tonnage. Lineal feet pipe in condenser T. ., . f Diameter, in. .. . Liquid receiver < ,. . , . (^Length, m „., . f Diameter, in Oil separator < . , , • [Length, m „ ,. , , [Diameter, in Uoolmg tank < tt ■ i j. • [Height, in Cooling coil, lineal feet 2-inch pipe Equalizing tank /Diameter, in \Length, in Motor horse-power for compressor 4,700 10,600 22,000 45,000 68,500 i 1 2 4 6 5,933 11,866 23,732 47,464 71,196 20 30 60 114 152 6 6 8 10 10 36 48 48 48 60 3 4 6 6 6 30 36 36 42 48 36 36 42 48 54 36 60 72 72 72 25 50 100 200 300 18 18 18 18 18 36 36 36 36 36 2 3 5 7i 15 92,000 8 94,928 190 12 60 6 54 60 72 400 18 36 15 To ascertain the amount of water to be circulated by the pump divide the radiation losses per hour by 5 which gives the amount PLUMBING, DRAINAGE AND WATER SUPPLY 171 ter in pounds per hour to maintain a loss of 5° in the piping n from pump discharge to cooUng tank return. To this add etual amount of water used for drinking purposes bearing in that this allowance of I gallon and 1 gallon respectively ay is for an 8-hour day. This is the amount of water to be lated per hour. ample. The following are the actual figures used in esti- ig a plant in one of the larger buildings. The calculations give the method of applying the data given above. This . has been in service some time and has given good results. ere are 8 bubbling cup drinking fountains and 26 lavatories ice water faucet attached. The maximum number of occu- 3 in the building at one time is 366 for an 8-hour period; as 75 per cent of them will use bubbling fountains exclusively e on 1 gallon per occupant. aximum quantity of water consumed = 366 gallons per 8 3 = 1100 gallons per 24 hour day. 1100 times 8^ equal pounds per 24 hours. ( reduce this from 75° to 35° requires 9166 times 40 equals )40 B.t.u. per 24 hours. le circulating line contains 1115 feet of J-inch pipe; 730 feet h; 155 feet 1-inch; 105 feet IJ-inch; and 95 feet 2-inch, g the factors hereinbefore given the heat absorption of i lines is as follows: 1115 feet 3.84 = 4260 B.t.u. per 24 hours. 730 feet 4.00 = 2920 B.t.u. per 24 hours. 155 feet 4.26= 660 B.t.u. per 24 hours. 105 feet 4.78= 500 B.t.u. per 24 hours. 95 feet 5.88= 560 B.t.u. per 24 hours. Total =8900 B.t.u. per ^ hours per degree differ- ence between water and air. ike room temperature at 90° and water at 40° giving a differ- of 50°. 8900 X 50 = 445,000 B.t.u. per U hours, lost by ition. Adding that required to cool the water gives 445,000 36,640 = 811,640 B.t.u. per 24 hours, divided by 24 equals 50 B.t.u. per hour. Adding 10 per cent for uncovered fix- connections, and tanks we have 33,850 plus 3,385 equals 35 B.t.u. per hour as maximum load. 172 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS Referring to first column of table above it is found that the nearest larger size standard machine is for 45,000 B.t.u. -per hour having a rated capacity of 4 tons refrigeration. All the various parts of the apparatus were made the sizes called for in this table for this size machine. Amount of water circulated. Total radiation losses equal 445,000 plus 10 per cent equals 489,500 B.t.u. 24 hours equal 20,400 B.t.u. per hour. 20,400 divided by 5 equals 4,080 pounds water per hour. 4,080 divided by 8| equals 490 gallons per hour to which must be added the water consumed for drinking pur- poses which equal 46 gallons per hour. 490 plus 46 equals 536. The pump was specified to pump 10 gallons per minute against a head estimated at 60 feet, which is the height of balancing tank above pump plus the estimated pipe friction. The above plant has been tested, placed in service and has given good results. ESTIMATING The following data are used in making preliminary estimates of cost of drinking water systems and for checking bids. Used with proper judgment as to local conditions they will give good results. The figures are based on conditions as they apply in cities and larger towns where good labor and material are easily obtainable. The figures in each case are the contractor's cost for work in new buildings and 15 per cent to 25 per cent should be added to estimate for contractor's profits. Pedestal type drinking fountains in place with non-siphoning trap, etc., equal $50. Wall type drinking fountain in place with faucets, cocks, and fittings equals $60. For each lavatory equipped with ice water faucet and combina- tion faucet add to cost of lavatory with separate hot and cold faucets $5. Ice box in basement in place with overflow, cesspool and coun- terweight equals $135 with 50 feet of pipe, and $160 if 100 feet of pipe is used. Sanitary water coolers in place complete with trap and imme- diate water supply and sewerage connections. PLUMBING, DRAINAGE AND WATER SUPPLY 173 .efrigerating machines in place including compressor, motor, iroUer, foundations, oil separator, liquid receiver, condenser, msion coils, cooling tank, equalizing tank; all refrigerant ng and fittings, water supply and waste to condenser and pressor jacket, triplex circulating pump and motor, all com- e per ton of rated capacity of compressor. i ton =$1100 4tons = $1500 1 ton = 1200 6 tons= 1700 2 tons= 1350 8 tons= 2000 !e water pipe, valves and fittings in place, including cork iring, hangers, floor and wall plates, cutting in new buildings, ' , per foot of pipe. Galv. Brass Hnch = S0.55 $0.85 f-inch= 0.65 0.95 L -inch= 0.75 1.15 li-inch= 0.85 1.45 [i-ineh= 0.97 1.70 Galv. Brass 2 -inch = $1.10 $2.10 2i-inch= 1.30 2.70 3 -inch= 1.60 3.60 3i-inch= 1.85 4.50 4 -inch= 2.15 5.20 he first column above is based on galvanized iron pipe and igs and the second column is based on iron pipe size brass and cast brass fittings. one of the estimates above include any portion of the drain- systems to which the fixtures in question are connected. SPECIFICATION lere follows a typical specification which is the uniform type by the Supervising Architect's office. le drinking fountains, drain pipings, etc., are specified in con- ton with, the plumbing fixtures and waste water systems 3ctively. :inking- water system. This contractor must furnish and in- complete in every detail a drinking-water system to provide id water at the various drinking fountains and ice-water ;ts in the building. neral arrangement. The apparatus and appliances to be lo- 1 where shown on drawings and as directed, with refrigerat- 174 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS ing machine, condenser, cooling tank, circulating pump, etc., in the basement, equalizing tank in attic, and fountains and faucets throughout the building. Water-supply and waste connections. Where shown on drawing a connection provided with a gate valve to be made to water main at basement ceiling. Water-supply pipes of proper size to be made to the various parts of the apparatus, i. e., condenser, cooling tank, compressor, etc., and each connection to have a gate valve. This pipe to be same as other cold-water pipe installed under this specification. Overflow from condenser and compressor jacket to be run and discharged over engineer's sink, unless otherwise shown on draw- ings. A cesspool with a running trap to be placed in proper location to receive overflow and drain from cooling tank herein- after specified. Drinking water piping system. The drinking water piping system to start from the pump in basement and run along basement ceihng with branches and risers of the sizes noted. Risers to continue up to attic and be collected together in attic and run and con- nected to opening in or near bottom of equalizing tank hereinafter specified. The return main to be taken from tap in or near top of equal- izing tank and be run down stack and to discharge into cooling tank. Each rising line in basement and corresponding line in attic and run-out to each fountain or faucet on first floor and basement to have a gate valve. Kind of pipe, covering, hangers, etc., to be as hereinbefore specified in connection with water supply system. Refrigerating machines. Machines using either ammonia, sul- phur dioxide, carbon dioxide, or ethyl-chloride may be used, and must be of compression type. Machine shall be of sufficient ca- pacity to remove not less than — British thermal units per hour from the circulated drinking water. This is the net work to be performed in the cooling tank exclusive of all transmission and radiation losses in machine, tank, etc. Compressor shall be of rugged construction and shall be ar- ranged to reduce as far as practicable the possibility of escape of refrigerant into building. Reciprocating compressor may be inclosed in a sealed metal chamber forming condenser and liquid PLUMBING, DRAINAGE AND WATEE SUPPLY 175 v^er, may have cylinder immersed in same chamber with con- iT, or may have cyhnders inclosed in independent water it. No stuffing boxes will be permitted except on crank . Crank cases to be inclosed joints between covers, and c cases to be ground to perfect fit without the use of any its. Pistons shall have sufficient number of snap rings to mt leakage of refrigerant. Valves shall be ground to fit and provided with steel springs. Rotary compressors have gears inclosed and run in oil. brication of compressors shall be by splash system, and suit- Dil eliminator shall be provided on discharge from compressor, ere shall be a safety valve or other approved appliance to into the low-pressure side when the pressure at the discharge ! exceeds a certain predetermined pressure fixed by the ifacturer. e machine used to be mounted on a cast-iron bed plate on a ble brick or concrete foundation provided by this contractor io be driven by a mot or of ample size wound for — volts — nt by means of double oak tanned leather belt or approved less chain belt. Motor to be in accordance with specifica- hereinafter for "Motors." event machine having pipe or coil condenser is used it shall a by-pass of proper size and properly valved to enable iressor to pump out the condenser. arings of machine used to be of ample size and lined with best ty antifriction metal, ichine used shall have name of manufacturer cast on or a name plate riveted on. The name of contractor or dis- ting agent will not fulfill this requirement. pension chamber. In event of a machine having compressor aled metal chamber, an expansion chamber shall be con- d thereto and be arranged to be partly submerged in the : of cooling tank. denser. Condenser shall contain ample surface to insure num water consumption and medium head pressure with msing water at 70° F. Condenser may consist of a sealed ber containing compressor, which is enclosed in a metal tacle, with cover, and partly submerged in condensing •. Condenser may be a coil of extra heavy pipe submerged 176 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS in chamber forming cylinder jacket or in a separate water chamber, or may be a double pipe condenser. Pipe shall be special ammonia piping coils and shall have welded joints. Double pipe condensers shall be made up with extra heavy special fittings. Double pipe condenser to be suit- ably mounted where shown on drawings or directed. Flow of condensing water shall be in opposite direction from that of re- frigerant. Condenser shall be connected to water supply and overflow to sewer as hereinbefore specified. Liquid receiver. Liquid receiver to be of ample capacity and may be formed in sealed chamber inclosing compressor, may be in base of compressor, or may be of extra heavy wrought iron with welded heads fitted with gauge glass safety cocks and inlet and outlet valves. Expansion coil. The expansion coil, if used, to be placed in tank hereinafter specified, shall be spiral in form and shall con- tain an ample amount of proper size extra heavy wrought-iron pipe with welded joints and galvanized after welding. Cooling tarik. Cooling tank shall be of the open type, con- structed of ^-inch galvanized iron — feet inside diameter and — feet high, with IJ-inch angle iron around top and bottom; rivets to be f-inch in diameter and spaced not over If inches apart. All openings in tank for pipe connections shall be provided with standard screw flanges riveted on or with reinforced openings. Tank shall be provided with a — ^inch drain opening and — ^inch overflow opening. Overflow and drain openings to be piped to cesspool hereinbefore specified and the latter to have a gate valve. Tank shaU rest upon an insulated bottom supported on the basement floor. The insulating base to rest upon concrete base 6 inches high, built on basement floor and extending 3 inches out- side of insulating base all around. The insulation shall consist of one course of l|-inch thick cork laid in hot asphalt; a second course of cork IJ inches in thickness to be laid in hot asphalt directly on top of the first course; all joints shall be made tight and top course flooded with hot asphalt. The insulation shall extend to back side of outer sheathing of sides of tank and edges covered with asphalt. The sides of the tank will be insulated with granulated cork well tamped, not less than 8 inches thick at any point, and held in PLUMBING, DRAINAGE AND WATER SUPPLY 177 e by suitable outer casing constructed of f-inch T. & G. .thing, top edge to be carried up to underside of |-inch sheath- on the top of cover, and edge to be covered with asphalt, ithing to extend to top side of outer cover of top, as herein- V specified, and down to concrete base on bottom. Three is made of No. 14 Brown & Sharpe gauge brass IJ inches 3 to be placed on tank and held in place with brass screws. ithing to be held in place independent of the brass bands, jarter round to be placed around bottom of tank. Top edge ink to be finished with a neat wood molding around same, he top of the cooling tank will have an outer cover of |-inch z G. sheathing backed with 3-ply insulating paper, 1| inches ork board covered with asphalt and backed with |-inch T. & heathing, top cover to be provided with access opening fitted L lid; lid shall be of the same general construction as the top shall be fitted with lifting ring and brass hinges. Entire top ank to be easily removable to permit removal of expansion 3. alancing tank. There shall be furnished and installed in the c a galvanized sheet-iron equalizing tank, — • diameter by — high. 'Tank shall be constructed of j^-inch galvanized- 1 plates and shall have a — inch opening in the shell .near the for the return pipe to the cooling tank, a — inch opening above opening for the return pipe to serve as an auxiliary overflow ^aste pipe as shown on plans, and a — inch opening in bottom connection to risers from pump; openings shall be properly forced to receive pipe connections. Tank to have a clean-out dhole in one end and have flat heads. he tank to be suspended from roof construction or carried on sorts made of pipe and maUeable-iron fittings, as directed by irintendent. ank to be insulated on shell and ends with two thicknesses [-inch best quahty cork board, pressed to fit shgU of tank, k board to be put on with asphalt with all joints staggered, k board to be covered with 12-ounce duck securely sewed on painted two coats asphaltum paint, and held on with brass ds 1 inch wide of No. 14 Brown & Sharpe gauge placed 12 les apart. Insulation of heads to be held in place by circular 'ts of No. 18 galvanized iron under the canvas covering. 178 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS Circular sheets to be held in place by four-worm wire stays ex- tending from end to end of tank. Galvanized-iron end sheets to be suitably reinforced where necessary. A neat removable sec- tion to be made for access to handhole. Edges of opening for this purpose to be protected by a galvanized-iron thimble flanged inside of cork and soldered to circular sheets. Woodwork. All woodwork in connection with cooling tank to be hard pine or cypress. Circulating pump. Furnish and erect where shown on plans one triplex pump capable of circulating not less than — gallons of water per minute through the piping system, at not exceeding 50 revolutions per minute. Pump to have brass plungers operating through approved stuffing boxes. Cylinders to be brass hned and pump to be brass fitted throughout. Crank shaft and con- necting rods to be cast steel or forged. Bearings to be lined with best quaUty antifriction metal and be provided with sight-feed lubricating devices. Pump to be driven by an electric motor through an approved noiseless chain belt of ample size and strength. Pump and motor to be set on one cast-iron sub-base on a suitable brick or concrete foundation provided by this contractor. Suction and discharge connections to have gate valves near pump and discharge connections to have check valve. Air chamber of proper size to be placed on discharge connection near pump. Motor to be in accordance with specification hereinafter for "Motors." Alternate circulating pump. In lieu of a triplex pump contrac- tor may furnish and install an approved screw pump of same ca- pacity. Pump to have four cast-bronze or cast-brass screws or impellers. Pump to be brass fitted throughout. Bearing to be of ample area lined with best quality antifriction metal. Supply and discharge connections to be so made in relation to location of screws that there will be no end thrust. Brass stuffing boxes to be on suction screws. Screw pump to be direct-connected to motor by a flange coupling. Motor and pump to rest on one cast-iron sub-base mounted on a suitable brick or concrete foun- dation furnished by this contractor. Motor to be in accordance with speciflcation hereinafter for "Motors." Pump suction and discharge connections to have gate valve PLUMBING, DRAINAGE AND WATER SUPPLY 179 Gauges. Pressure gauges shall be provided on both high and V pressure sides of the system and shall be mounted on cast- >n gauge boards secured to waU or column where directed by perintendent. Gauges to have not less than 6-inch dial, iron body, and polished iss rim, and in accordance with the following requirements: tiion, pinion staff, sector staff, and hairspring to be constructed either nickel, phosphor-bronze, Tobin bronze, or German silver; id, not plated. In addition, the top and bottom plates must made of one of the above-named metals, solid, or of brass or iam metal with substantial bushings of one of the above-named ncorrosive metals. Levers, slides, and their adjugting and rot screws may be made of brass or steam metal. If the machine is enclosed in a sealed metal chamber no gauges U be required. Jointing, etc. All joints in refrigerant piping to be tinned and dered in a workmanlike manner. Refrigerant piping to be inted as hereinafter specified for pipes in heating system. The atractor must furnish all material for charging the apparatus idy for operation. Thermometers. Two thermometers with a range from zero to 0° to be installed in the drinking-water line near the tank, one be installed in the flow and one in the return line. Float valve. An approved 1-inch diameter float valve to main- n water level 2 inches above top of expansion coils must be stalled in the drinking-water coohng tank and connected to the iter piping. Covering. Water supply pipes and condenser overflow to be TOred as hereinbefore specified for cold-water pipe. Covering • ice-water pipe is hereinbefore specified. AU refrigerant pipe, Ives, and fittings on the "low" side to be covered same as reinbefore specified for ice-water pipe. Overflow from balanc- ; tank to be covered same as other ice-water pipe. Motors for direct current. Motors to be wound for — volts ■ect current. To be of design adapted to service and must capable of developing the required power and of withstanding nporary overloads of at least 50 per cent. Bearings to be of 3 self-oiling type. Motor must be designed to operate practi- lly without noise. 180 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS Speed of motor for compressor must not exceed five times that of compressor. Field coils must be form wound and so secured that they may be readily removed without unwinding. Armature must have slotted core, with windings thoroughly insulated and secured firmly in place. It must be balanced both mechanically and electrically and be well ventilated and easily removable. Commutator to be of drop-forged or hard-drawn copper of highest conductivity, insulated with mica or micanite of even thickness and proper hardness to insure uniform wear, and must run free from sparking or flashing at the brushes at any load up to specified full load or during change of load. It must have ample bearing surface and radial depth for wear. Brushes to be of carbon of such cross-sectional area as will not cause sparking, burning, or blackening of commutator at load specified. Brush holders to be of such design that no chattering will result from continuous use. Collective adjustment of brushes to be made by means of rocker, and individual brush tension is to be maintained by a spring. If the motor is of the interpole type, the rocker arms may be omitted. The frame of machine must have an insulation resistance from the field coils, armature windings, and brushes of not less than 1 megohm. Motor must be capable of standing a breakdown test of 1,500 volts alternating current for one minute. Motor is to be run continuously at full load for six hours, and at the expiration of that time the temperature of the armature and fields shall not exceed 50° C. and of the commutator 55° C. above the temperature of the surrounding atmosphere. Tem- perature to be measured by thermometers shielded by cotton waste in a manner approved by department's agent. For alternating current. Motors to be wound for — volts, — phase, — cycle, alternating current. Motors to be of induction type with rotating secondaries of ample power to perform the work required and capable of withstanding momentary overloads of 50 per cent. Compressor motor shall have phase-wound rotor with slip rings for inserting starting resistance. Circulating pumps motor shall have squirrel-cage rotor. PLUMBING, DRAINAGE AND WATER SUPPLY 181 nsulatioji. Each motor must have an insulation resistance ween stator windings and between stator windings and frame it least 1 megohm. The insulation must be capable of with- ading a breakdown test of 1,500 volts alternating current for 1 minute. I eating. After a continuous run at full load for six hours the ! in temperature of any part of the windings or frames of tors must not exceed 50° C. above the temperature of the sur- nding atmosphere. Temperature to be measured by ther- meters shielded by cotton waste in a manner approved by the tartment's agent. Controlling panels. Controlling panels shall be constructed of ished black slate, treated to prevent absorption of moisture, less than | inch thick. Panels containing fuses, switches, and !uit breakers shall be mounted flush with rheostat panels, lels shall be secured to angle-iron wall frames wherever suit- e wall or column is available near motor to mount said panel, .en no such support is available panel shall be secured to angle pipe floor stand. Jl resistances and other appliances on rear of panels shall be iciently inclosed to prevent the .insertion of a hand into space upied by such resistance. All panels shall be mounted with torn not less than 1 foot above floor. All connections and re- ances shall be mounted on the back of panels and all moving tacts to be on front of panels. All angles and pipe braces in nection with panels to be enameled black. 'or direct current. Panel for compressor shall have mounted reon one double-pole overload circuit breaker with laminated in contacts, auxihary carbon break of the independent arm e of proper capacity to protect motor, and one hand-starting ostat with no voltage release. 'anel for circulating pump shall have mounted thereon one ble-pole, single-throw knife switch with enclosed indicating ;s of proper capacity and one hand-starting rheostat with no ;age release. 'o?- alternating current. Panel for compressor motor shall have mted thereon one — pole overload and no voltage release uit breaker of the independent arm type and one starting stance of proper capacity. 182 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS Panel for circulating pump shall have mounted thereon one — pole, double-throw knife switch without fuses on starting position and with enclosed indicating fuses of proper capacity to protect motor from overload on running position. Switch must be provided with means to prevent same being left in starting position. Electrical connections. Conduit and wiring to the panels will be provided under the "Conduit and Wiring" section of this specification. All connections between motors and panels hereinbefore speci- fied must be made by this contractor. All conductors are to be run in steel conduit terminating in approved condulet type fit- tings except such connections as may be so short as to be self- supporting, and these must be fully protected from abrasion or other mechanical injury. Conductors must be rubber-covered, weU-tinned, soft-drawn copper of highest conductivity, made in strict accordance with the National Electrical Code, and must have a distinct marking of the makers. All conductors. No. 8 Brown & Sharpe gauge and larger, are to be stranded and con- nections made by soldering wires in cup lugs. No joints or splices will be permitted in feeders except at outlets. Wiring system must test free from short circuits or grounds, and the insulation resistance between conductors and between conductors and ground must not be less than 1 megohm. Where size of conductors is not given, the capacity must be such that the maximum current carried will not exceed the limits pre- scribed by the National Electrical Code. Wrenches. A complete set of wrenches for refrigerating ma- chinery is to be furnished and mounted in a suitable hardwood frame, located where directed by the custodian. Refrigerant connections. All necessary refrigerant-piping con- nections required for the complete installation must be furnished and installed by this contractor, including fittings, valves, gauges, purge connections, scale traps, receivers, oil separators, etc. The pipe lines shall be provided with heavy flange union con- nections to permit removal of any parts without disturbing or cutting pipe. All pipe in refrigerant lines shall be extra heavy, special black ammonium pipe, and all fittings to be extra heavy mild-steel ammonia fittings unless otherwise specified in connec- tion with tvoe of machine. PLUMBING, DRAINAGE AND WATER SUPPLY 183 Stop valves to be screw ends, bolted bonnets, extra heavy ttmonia valves. Expansion valves to be of the needle-point pe. Painting. The machine, motors, and pump to be rubbed down id painted one coat before leaving shop and after erection with le additional coat of lead and oil paint of tint approved by perintendent. Piping to be painted same as steam pipe. Cooling tank to be led and rubbed down and given two coats of hard oil. Paint- g for cork covering is hereinbefore specified. Balancing tank attic, to be painted two coats heavy asphaltum paint. Tests. All water piping in connection with this apparatus to tested as hereinafter specified for water pipe. All refrigerant ping must be tested to a hydrostatic pressure 50 per cent greater an the actual working pressure, and must be tight under this essure. Operating test. After the complete installation the capacity the plant wiU be determined by a trial of the unit, to be made the presence of and under the direction of a representative of e Supervising Architect. A temporary connection between a hot-water line and cold- tter supply to tank if necessary must be made by the contractor that the water used can be obtained at about 75° F. A tem- rary draw-off connection must be made by the contractor so at water in drinking-water cooling tank can be drawn off from ttom of tank and weighed at the draw off. A test will be run for a period of not less than 8 hours, as fol- vs : The machine and circulating pump will be stopped. Drain water from tank and remove all ice from coils. Fill tank to 'el established by float valve with water at a temperature of out 75°F. Then start machine and run under normal condi- ns until thermometer in draw off near the tank indicates 40° Readings to be taken as soon as this temperature is reached, ich will be starting point of the test. The equipment to be I under starting conditions during the test and difference in Qperature between readings in inlet and outlet to tank multi- ed by pounds of water drawn off will represent the work in itish thermal units. At the expiration of test allowance will made for ice formed on coils as hereinafter explained. At 184 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS once on completion of test all water will be drained from the tank and drain closed and left closed until all ice has melted off the coils, the resulting water will be weighed and added to work in water cooling above mentioned at the rate of 144 B.t.u. per pound of melted ice. The total B.t.u. thus obtained will repre- sent the net work performed by the plant. No allowance will be made for loss in radiation through tank and connections. During the test the temperature of water at the pump suction is to be maintained at approximately and not exceeding 40° F. Should the net work performed be less than that hereinbefore required, the Supervising Architect shall have the right to reject the entire apparatus or any part thereof and require the contrac- tor to furnish a machine that will fulfil the requirements of this specification without additional expense to the Government. All expenses of such tests, except such as hereinbefore provided under "Inspections and tests," to be paid for by the Government, must be paid by the contractor. TESTS OF PLUMBING AND DRAINAGE SYSTEM Special precautions are taken to insure that all parts of the plumbing and drainage system are free from defects and leaks, and the following specification requirements are prescribed with that in view: The entire system of soil, waste, drain, and vent piping, includ- ing the interior downspouts and rain-water drainage system, must be tested with water or air, as hereinafter described and proved tight to the satisfaction of the superintendent of construction before the immediate connection is made to city sewer, trenches back filled, piping covered, or fixtures connected. Either the water or the air test may be used, except when there is danger from freezing, when the test must be made with air. Wooden plugs are not to be used in making the tests. The connections between the building and the city sewer and the drainage system below the basement floor are to be tested separately. Water tests. If tests are made with water, the connection from the building to the city sewer and the drainage system PLUMBING, DRAINAGE AND WATER SUPPLY 185 ;low basement floor are each to be filled with water to top of a jrtical section of pipe 10 feet high, temporarily connected to the ghest point on the lines to be tested, and the water allowed to and at least 30 minutes for inspection, after which, if the lines :ove tight, the water is to be drawn off, immediate connection ade with city sewer, and trenches back filled. The soil, waste, drain, and vent piping, the interior down- )Outs, and rainwater drainage system above the basement floor le must have the openings plugged where necessary and the ping system above basement floor filled with water to the level ' the main roof gutters and allowed to stand at least 30 minutes r inspection, after which, if the lines prove tight, the water is I be drawn off and the fixtures connected. Each vertical stack )ove basement floor with its branch waste and vent pipes may i tested separately by inserting plugs in the cleanouts at base verticals in lieu of filling entire system in building with water. Air tests. If tests are made with air, a pressure of not less than I pounds per square inch, equal to 20 inches of mercury, must ; applied with a force pump, and said pressure maintained at ast 15 minutes without leakage. A mercury column gauge must be used in making the air tests. 3sting instruments must be furnished by the contractor. Smoke test. After fixtures have been connected, a smoke test ust be applied to the sanitary system, and the entire system oved tight, to the satisfaction of the superintendent, when led with smoke under pressure equal to 1 inch of water. The aoke machine must be provided by the contractor. Test of water-supply system. At completion of the work, cept application of the non-conducting coverings, the waste- pply system must be tested to a hydrostatic pressure of 100 lunds to the square inch. Any water piping run in chases in walls must be tested to lOve pressure and proved tight before the chases are covered, le test pump must be provided by the contractor. Cost of tests and certificate. Cost of tests to be borne by the ntractor, who must furnish the office, through the superin- ident, with a certificate that the required tests have been tisfactorily made. Certificate must be countersigned by the superintendent, who 186 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS ESTIMATING DATA FOE PLUMBING AND DRAINAGE SYSTEMS After the drawings for a plumbing, drainage, and water-supply system are prepared an approximation of cost must be made in order to be able to determine whether the proposals later ob- tained for the work are reasonable; and the following data, which will generally give results within 5 to 10 per cent of the lowest proposals received, are used: New building, approximate cost complete plumbing sys- tem, not including marble finish for all toilet-rooms, average per fixture $125.00 Old building, approximate cost complete new plumbing system, including marble finish for toilet-rooms, aver- age per fixture 200 . 00 For estimate on the above basis count as one fixture each : Shower-bath. Water-closet. Slop sink. Water heater (with hot-water tank). Urinal. Lavatory. Small sink. Interior downspout. Fire-hose connection with hose and rack complete. Drinking fountain with ice box. Four wall hydrants. Cost of system is divided approximately as follows; "Roughing in," per fixture 50.00 Marble work, per plumbing fixture 75.00 Fixtures, average each 50 . 00 Additional for removal of work in place, and for cutting and repairs in old buildings, per fixture 25.00 If brass water pipe is used throughout the job add $20.00 per fixture to above figures. Itemized estimating data. If a very close approximation of the cost of plumbing and drainage system is desired, all pipe, fittings, valves, and fixtures should be taken off the plans and specifications, and the following unit prices used: Vitreous corner lavatory, with back, including connec- tions and trimmings as described above, complete in place $35.00 Special ice-box, complete in place 160 .00 PLUMBING, DRAINAGE AND WATER SUPPLY 187 Portable type combination water cooler and drinking fountain, in place 1150.00 Vitreous corner lavatory, with back, including connec- tions and trimmings as described above, complete in place 36.00 Bubbling fountain, pedestal or wall type, complete in place 32.00 Vitreous slop sink with trimmings, complete in place. . . 65.00 Enameled-iron sink, complete in place 22.50 Fire-hose rack with 75 feet of 2-inch hose, complete in place 33.00 Roof connections complete in place for down pipes from gutters or for vent stacks: 2-inch diameter 5 .00 3-inch diameter 5.25 4-inch diameter 5.80 5-inch diameter 6.00 6-inch diameter 7 .00 Four-inch lead bend with ferrule, complete in place, for basement closet connection 3 .00 Three-inch lead bend with ferrule, complete in place for basement slop sink connection 2.75 2-inch lead bend, etc 2.00 Cast-iron water heater with 12-inch grate and 18-inch x 60-inch galvanized steel storage tank, with copper or brass steam coil, automatic temperature regulators, and all trimmings, smoke connection, etc., complete in place, including nonconducting covering 180.00 Outfit as described above, without steam coil 160.00 Automatic gas water heater with capacity of four gallons per minute, and steel tank with steam coil as described, complete in place 250.00 Shower-bath fixture with floor drains, soap dish, coat hooks, seat, etc., complete in place 60.00 Anti-freezing wall hydrant or street washer, in place 10 . 00 Excavations for pipe trenches inside of building : Trench 3-f eet inch deep, per lineal foot . 15 Trench 4-feet inch deep, per lineal foot ' .25 Excavations for pipe trenches outside of building, trench with average width 3 feet inch and average depth 12 feet inch, in ordinary soil, per lineal foot 1 .00 Excavations in rock, per cubic yard 3.00 Repairing streets, allow to cover any kind of work: Per square foot 0.30 Per lineal foot of trench 1 .00 Street manhole and running-trap manhole, with oast-iron frame and cover, complete in place 76.00 188 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS Brick manhole, 18-inch x 30-inch, in basement floor, with cast-iron frame, and cover, complete in place $30.00 Area cesspool, complete in place 1 .50 Single-hub running trap, with cleanout plug, complete in place 3 . 00 2-inch 3,00 3-inch 4.00 4-inch 4.50 5-inch 5.00 Siphon-jet water-closet, 54-pound bowl, with porcelain tank and connections, floor flange, coat hooks, toilet- paper holder, etc., complete in place 40.00 Siphon-jet urinal with porcelain tank, outlet flange, etc., complete in place 30.00 Porcelain stall urinal with porcelain tank and trimmings, complete in place 60.00 Vitreous rectangular lavatory, 24-inch x 20-inch, with faucets, nonsiphoning trap, supply and waste connec- tions to wall or floor, compression stops and air cham- bers on supplies, and with towel rack, complete in place. 40.00 For special combination hot and cold water faucet, ice water faucet, and tumbler holder on lavatory, add for each lavatory so equipped 5.00 Compound type water meter including heavy locked meter cock or gate valve, and three gate valves, j-inch drain valve and galvanized pipe connections and fit- tings complete in place. 2-inch 75.00 With brass pipes and cast iron fittings 85.00 3-inch 150.00 With brass pipes and oast iron fittings 175.00 4-inch 225.00 Heavy iron body water pressure regulating valve, in- cluding three gate valves, two pressure gages, strainer fitting and galvanized iron pipe connections and fittings complete in place: i-inch 15.00 14-inch 38.00 2 -inch - 52.00 3 -inch 80.00 With brass pipe and cast iron fittings: §-inoh 17.00 IJ-inch 44.00 2 -inch 62.00 Rough cast brass downspout nozzles in place including cutting of hole and nipple through wall: 2-inch 5.00 PLUMBING, DRAINAGE AND WATER SUPPLY 189 3-moh $6.00 4-inch 7.00 6-incli 8.00 e-inch 9 .00 Automatic water operated ejector in place complete and ready for operation: 1 -inch 60.00 IJ-inch 65.00 Rodding cleanouts on cast iron pipe below basement floor including fitting in main drain or on cast iron drain outside of building: 3-inch 2.30 4-inch 2.90 5-inch 4.00 Cleanout fittings with heavy brass plug and nickel plated cover plate in place: 2-inch 1 .80 3-inch 2.75 4-inch 5.00 5-inch 8.90 6-inch 12.00 Screw jointed cleanout fitting with heavy brass plug in place: 2-inch 1 .20 3-inch 3.25 4-inch 4.50 5-inch 7.65 6-inch 15.00 Balanced type back water valves complete with gate valve and 25 feet of J-inch brass vent piping including galvanized fitting in vent stack in place exclusive of manhole: 3- and 4-inch 20.00 6-inch 25.00 rhe following table gives cost in place of galvanized mild steel )e, recessed drainage fittings, etc. Threads included in price of ;ing. Fittings are long radius. For valves, hangers and plates I schedule for heating work. o H S of O o t-H Pi O P 05 o Ph t— f Ph H H 03 P P N <: o lO CD T-( (N 1-1 §s o 00 o § 8 s o O 5 to 1— ( lO CO o T-H CO lO o S© ^ OS CO s C3 T-H C<1 CO CO CO T-H GO »o CO S53 (M o lO lO CO o 8 "0 § CO ^ S8 00 9& 1^ 2 O CD s CO ^ CO CD o CO 00 CO (M 1—1 00 8 lO § 8 ^ 8 T-H § to CO 8S CD 8 'SI 00 lO CO T-H ^ >ra CI T-1 00 -* 1—1 lO ^ CD CO 05 to 00 o o OS o 8 S s g o T-H s 8 O lO o t^ lO O c^ ^ '^ CO 00 CO CO o- lO ■* CO T-H T-H ■* CO CO Tf Ttl CO g s ^ g 1— t o o o 5 o 1> J§ s lO o o >o o 8 o o O T-H o -I CO c^ CO ca ^ iM c^ ■* CO (M CD o lO IM oq IM CO CO CO s 00 o ^ § s s 8 o 8 >o OO CO lO o o g O lO CO o g .— 1 (M ^ (M 1—1 (M 1-H T-l (N (N T-H CO o CO cq T-H T-H ea S o g g s § s o CO 8 § 8 ^ K 8 lo o C3i »o o 1—1 i-H T-H 1— 1 1—1 rH rH CI tN cq o (M ■-1 O 1-H 8 ^ o g >o o o o CO >o o CO lO CO o 00 00 m o tffl CO o --' T-H 1— ( 1— i i-H cs -^ J-i >— t T-H C<1 o T-H o o ^ I— ( 00 1— t g 8 s O 1—1 g g 8 cq o T-H K lO lO r~ T-H g o -^ -' 1—i rH o T-H '-' T-H 05 o o ^ rHN 1— t ^ s s s g 8 8 8 LO IC lO 00 o o o o o T— f o 1—1 o ^ o o o - m GQ QJ k. '^ .1 >" 3 o CI o S O 03 lO 5 Ai tM -y ^ V a o o t3 O pt o O ■D OS faDT3 a 0) .-I l>K.g So S 03 lO 5 m ■* T^ -CJ T3 T^ O; O) ID tsq tq N ID (D (D tq IS] 'a 1=1 ft 03 q=l ID (D cq t:q Q, ID a:: a o a :=! -2 '^ ' t3 CD 2 03 d ^ <^ 1^ c5 1^ m m m m m ^ y-i d CI CI fj CI p] rt d t» d d M ctl crt si ed crt cit Ol Ol IS !> > > > > > > > > m > ;> o3 o3 Ol ctl ctt ct) 01 crt CH Ki 01 tH Ol Ol FqpqOOOOOOOOOmOO PLUMBING, DBAINAGE AND WATEE SUPPLY 191 For hangers, valves, black fittings for vent pipes, etc., see heating ledule. When using heating schedule for fittings, etc., for plumbing rk add cost of threads to same. Double-hub running trap with cleanout plug and fresh-air inlet, complete in place: 6-inch $10.00 8-inch 18.00 Extra heavy cast-iron soil pipe and fittings in place, exca- vation not included: )iameter Inches 2 3 Pipe per lineal foot W.20 0.30 Elbow, any turn $1.10 1.40 T, Yor45° Y branch $1.25 1.75 4 0.40 1.80 2.00 5 6 0.50 0.65 2.25 2.75 2.50 3.25 8 10 12 1.10 1.35 1.70 6.50 7.25 11.00 6.50 10.00 13.60 16 4.00 20.00 26.00 Pipe and fittings in place, for water supply, pipe. Exclusive of hangers, cutting, etc. Threads included in cost i, inches, diameter vanized mild steel pipe vanized malleable ells vanized malleable tees S3 unions ;e valves (brass) 1 pipe size brass pipe (rough) It brass ells (rough) it brass tees (rough) i B" J i 1 U n 50.10 10.10 SO, 10 SO.U 50.13 50.17 50.20 o.n 0.13 0.15 0.17 0.26 0.28 0,40 0.15 0.17 0.20 0.22 0,35 0,39 0,53 0.25 0.30 0.40 0,50 0,65 0,85 1,20 0.65 0.70 0.80 1.00 1,35 1,80 2,40 0.20 0.23 0.29 0.37 0,48 0.69 0,83 0.13 0.15 0.18 0.22 0,33 0.41 0,55 0.19 0.23 0.29 0.34 0,53 0,65 0,88 2 50,26 0,55 0.70 1.70 3.47 1.10 0.80 0.98 For finished brass nickel plated pipe and fittings in place take twice 3 above for rough brass. CORK COVERINGS The following table gives cost of standard ice water thickness rk covering IJ-inch thick in place on ice water lines (exclusive pipe) including canvas, bands and painting. e, in. diameter, r foot 5" elbow borreduL-ing tee i i i J 1 U n 2 2^ 3 3i $0.33 50,37 50.42 50,45 50,54 50.61 50.70 50.78 50.87 50.95 51.08 0.45 0,50 0,55 0.61 0.70 0.78 0,87 0.95 1.03 1.18 1.32 0.50 0,58 0.61 0,70 0.78 0.87 0.95 1.13 1.19 1.32 1,53 0,55 0.61 0.70 0,78 0.87 0.95 1.03 1.15 1,32 1.56 1,71 4 51.20 1,52 1.77 2,05 192 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS For long radius fittings, double the prices for fittings given above and add 10 per cent. Standard brine covering (2 inches to 3 inches thick according to pipe size) costs 15 per cent more in place than standard ice water thickness. The following table gives cost in place of vitrified, salt glazed sewer pipe, with cemented joints, exclusive of excavation, back- filling or any special conditions met in exceptional soil. Diameter, inches Pipe per foot Y branches Elbows (any angle). Increasers 4 5 6 8 10 12 14 W.17 10.20 $0.23 $0.29 $0.41 $0.53 $0.68 0.80 0.90 1.00 1.30 1.80 2.25 2.90 0.70 0.80 0.90 1.25 1.65 2.15 2.80 0.70 0.80 0.85 1.10 1.50 1.90 2.40 15 $0.75 3.20 3.20 3.20 Nonconducting felt covering for hot and cold water pip- ing, take 70 per cent off the "22-cent" list for cost of covering in place complete. Terrazzo floor in place, including concrete bed, per square foot $ 0.50 Removing old floors and laying new concrete base and terrazzo floor, per square foot 1.25 Marble floor slabs, 2-inch thick, per square foot in place. . 1.50 Free standing marble, IJ inches thick, per square foot in place 1.25 Marble wainscot, l-inch thick, per square foot in place. . . 1.00 Marble coved floor borders, per lineal foot in place 1.50 Plain marble tile floor . 75 Nickel-plated brass standards, bracing, angles, etc., in place for marble work in toilet-rooms: For water-closet inclosure 18.00 For water-closet stall in carriers' toilet 4.50 For urinal stall 4.50 For shower-bath inclosure 18.00 Cleaning and painting walls of toilet-rooms three coats lead and oil, per square foot 0.30 Especial attention is called to the fact that the foregoing figures are correct for certain special conditions in new Federal buildings, but are not applicable under all conditions. Used with judgment they will give accurate results. CHAPTER V GAS PIPING The practice of the office is to install a complete gas piping sys- n in every building, except in a few of the larger cities, both for lergency use and to serve as a check on the cost of electric rrent supplied by local lighting companies, and while the system 3ts less than any other portion of the mechanical equipment, gives more trouble than all the rest of the work. Specifications 3 carefully drawn, and repeated and strict tests are imposed, d superintendents of construction and inspectors are charged to TB special attention to this branch ; but with all these precautions )uble frequently ensues. In making an extension to a building only a few years old it is ual to find the gas piping system in a bad condition and filled th leaks which are difficult to locate and costly to repair. Gas piping in old buildings is tested to only 4 inches of mercury, lich must stand one hour without perceptible drop. This test made with lighting fixtures disconnected and outlets capped. With old fixtures and old piping the test is reduced to 2 inches; d with new piping and new fixtures it is made to 3 inches of 3rcury. The gas piping system will average $3.00 per outlet in new lildings, and if the total piping is measured up, 15 cents per Dt for all sizes will be about correct. The following is a sample specification such as is used for a w building : SPECIFICATION This specification includes the installation of a complete system gas piping for supplying all the gas only and combination out- ,s indicated on the drawings. A gas meter satisfactory to the local gas company must be rnished and installed where indicated. All the gas outlets (except vault outlets and outlets indicated plans as gas only) to be arranged so as to allow placing on Tie of electric conduit boxes for combination fixtures. 194 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS Contractor to bring into the building a gas supply pipe of size noted on drawings, and furnish and place at curb Hne a stop cock or tee-handled gate valve on same, also a cast-iron extension stopcock box, located as directed. Gas main just inside of base- ment wall to be provided with a brass gas cock. Kind of pipe used from street main to inside of building and manner of laying same to be in accordance with the regulations of the gas company. If the company will not permit installation of pipe of size noted on drawing, the contractor must take up the matter, before installing the work, with the superintendent, who will refer the matter to the Supervising Architect. Gas pipes in building to be "standard" gauge galvanized wrought-iron or galvanized mild steel, and all fittings to be gal- vanized, malleable-iron, beaded fittings. Unless otherwise noted or indicated on the drawings the size of gas pipes to be as follows : Size of pipe Inches Greatest length allowed Feet Greatest number ot burners i 30 7 3 4 50 28 1 70 50 li 100 96 li 150 140 2 200 280 Main gas pipe of size noted on basement plan to start at point indicated, with capped inlet near basement ceiling, run along same to vent shaft or lookout shaft as shown. From the main, near shaft, a separate riser is to be taken and run up in shaft to supply the horizontal branches in each floor. Each separate riser is to be controlled by a gas cock, located where indicated on plan. Insert in main where shown near foot of risers a "T" fitting, and a 12-inch piece of pipe of same size as main, with reducing fitting, to be placed for the purpose of collecting drip and scales; a short piece of f-inch pipe with gas cock to be screwed to reduc- ing fitting, so that drip can be drawn off when necessary. Plugged outlet of size noted on drawing to be provided on gas main in basement at point indicated, for connection to special furniture fixtures to be placed under another contract. GAS PIPING 195 Gas main to be supported close to basement ceiling with ought-iron or malleable-iron hangers, and risers, except those short length, to be securely supported in an approved manner. Branches from pipes run in first floor to brackets in unplastered 3ms in basement, the gas main in basement, the branch in base- mt to post-office screen lights, and all gas pipe in unfinished tic or roof space to be run exposed. All other gas pipes to be ncealed. The supply branch to the screen lights to be fitted with a gas ck so that supply to said lights can be controlled. Cock to placed where indicated on drawings. Bracket hghts to be supplied by branches taken from the gas Ding run in the floor construction of the story in which they are !ated. Bracket lights in basement to be supplied from main first-floor construction. Gas outlets for bracket lights to be set approximately 7 feet ove floor, unless otherwise noted. Supply pipe for post-office •een lights to be taken from main near basement ceiling at int indicated, and run up concealed in screens and along same space provided for pipes, with outlets at points indicated. lese outlets will be, in general, about 7 feet above floor. The gas outlets for all vaults to be taken from gas pipes below or, and run up in wall alongside of vault doors to a distance of feet above floor line; outlets to extend just beyond finished ister line, and ends to be capped. Gas nipples for fixtures to be at right angles to the walls and iling from which they project, and to project from finished plas- • line of ceiling not less than f-inch nor more than 1| inches, d from finished plaster line of walls not less than | inch nor )re than f inch, and be properly fitted and capped. This juirement will be strictly enforced. No branch pipe from main to be less than | inch internal imeter. Outlets for all brackets, vault outlets, and drops for all chande- rs to be ^-inch diameter. Drops for chandeliers must be taken from center of a "T" inch; and where a chandelier occurs at the end of a branch, or at J of a run of main, the extra opening in the tee to be fitted with sapped 12-inch length of pipe to form a proper support for the 196 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS All gas pipes to be run regularly and in a workmanlike manner, using all necessary fittings, and in no case springing or bending the pipe to reach a point desired. All pipes to be run level where possible, and when necessary to be pitched, to grade down toward riser, and to be without traps. The use of salt water or any other corrosive substance to make piping tight is strictly prohibited. Each length of pipe must be hammered and all scale blown out before assembling. Pipe and fittings to be put together with red lead, litharge or any approved compound. No gas fitters cement will be allowed except at outlet caps. At the beginning of the work when directed by the superinten- dent the contractor shall furnish and set up in a readily accessible position where directed a test pump and a mercury gauge con- nected to the permanent gas piping. Pump and gauge to be properly protected and kept in working order until after final inspection, when same is to be removed when directed by the sup- erintendent. At all times, except when it would be impracti- cable on account of gas pipe actually being connected to work already in place, a pressure equal to 15 inches of mercury is to be maintained on all gas lines in place. At such times as the superintendent may direct, also (1) each time any new work is laid, (2) before the last coat of plaster is put on, (3) on completion of the plastering, (4) on completion of the finished floors and be- fore lighting fixtures are connected, the above pressure shall, without pumping, be maintained in the presence of the superin- tendent for a period of one hour with drop in pressure during the hour not exceeding J inch of mercury. Tests to be made by the contractor, at his own expense, and he must furnish this office, through the superintendent, with a cer- tificate that satisfactory tests have been made. The certificate must be countersigned by the superintendent, who will forward same to the Supervising Architect. CHAPTER VI CONDUIT AND WIRING SYSTEMS For electric lighting installations in Federal buildings the stand- i arrangement is an underground service connection to an en- mce switch in basement just inside of the building. In build- |s where only two or three distributing tablets are used the trance switch and the sub-feeder switches are combined in the me tablet. In larger buildings, requiring four or more dis- bution tablets, there is installed a sub-feeder tablet from which b-feeder or mains are run to the various distribution tablets roughout the building. In large buildings where an electrical generating plant may be stalled at some future time, a standard type of switchboard is iced in the engine room with a service connection to the mains the local companies. The main service switch is usually located as near as prac- sable to the point at which the feeder circuit enters the build- 5, and also near basement entrance door. The sub-feeder tab- ; or the switchboard is so located as to obtain the best runs and e shortest average length (capacities considered) of sub-feeders, le point sought for is one at which the sum of the products tained by multiplying the length of each sub-feeder by its ipere capacity is a minimum. The location for main service itch and sub-feeder tablet or switchboard is selected with due nsideration to the character of the room, and coal rooms, stor- e rooms, and letter carriers' lounging and toilet rooms are never osen. The distribution tablets for the post-office section are located the post-office workroom, so that all the lights in the work- )m and in letter carriers' lounging and toilet rooms, and gen- illy in the executive offices of the post office also, can be con- illed from same. All other tablets in the building are located pubhc spaces (corridors or lobbies) or in the basement outside post-office space and storerooms. 198 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS The locations sought for distribution tablets are those which will admit of reaching same readily with the feeder, and making all branches of approximately equal length, the maximum length being generally 100 feet. Architectural features of a building are also considered. The public lobby on first floor and the exterior lights at main entrance are controlled by the tablet located in the post office workroom, or, in the larger buildings by a tablet located in the boiler room in basement. Where not more than three circuits are required to supply a floor above or below a given tablet, they are taken therefrom. Not more than twenty circuits are taken from a tablet, and one or more spare switches are provided on each distributing tablet. In locating distributing cabinets in thin walls care is taken to see whether a steel beam is located directly over the cabinet; and should this be the case, the structural engineer is requested to move the beam or substitute two channels for the beam and set the backs of the channels IJ inches apart. A cabinet is never located in a partition wall which is less than 4 inches thick exclusive of plaster. Cabinets containing the distributing panels are of steel, and all cabinets and tablets are of special design. The tablets are of Blue Vermont marble and the distribution tablets contain 30-ampere switches and 10-ampere enclosed fuses controlling the various circuits. All wiring is run in rigid metal conduits, and all main service connections to the building are made underground and usually from a steel pole of special design located on the Federal property by the government. If special conditions forbid this, an under- ground connection is made from the service company's poles ad- jacent to the building site. The conduits to service company's poles are run up same 10 feet and provided with a weatherproof hood. The practice of the office was formerly to install handhole boxes at the base of service poles, but this has been abandoned as unsatisfactory, except in special cases. The junction box on main feeder conduit inside of basement is not made less than 6 inches x 6 inches x 3 inches deep. CONDUIT AND WIRING SYSTEMS 199 The feeder and other conduits in basement _ 1-inch diameter i larger are run exposed on basement ceiling and are installed rallel to the lines of the building. As a general rule, all other iduits in the building (except in roof space and in unfinished lies) are concealed. Conduits in floors are run in the most direct manner and are fc usually made larger than l|-inch diameter, a larger size be- ; difficult to conceal in floor construction. I!are is taken that conduits do not cross each other in the 3r construction in such manner as to occupy more than 3 inches .al space. [n most cases the conduits run up from the cabinets and run in Dr construction above with drops to the single-pole snap itches at entrance doors. This is, however, governed by the istruction, ceiling heights, etc., and an effort is made to re- ce the length of the runs to a minimum. The following tables are used to ascertain the sizes of conduits accommodate the various sizes and numbers of wire : CONDUIT SIZES FOR CONDUCTORS WIRE AND CABLE SIZE Cb. & s. gauge) TWO WIHES SAME SIZE THREE WIHES SAME SIZE FOUR ■WIHES SAME SIZE THREE WIRES DOUBLE SIZE NEUTRAL DUPLEX WIRES inches 4 4 3 i 1 1 li u n 2 2 2 2i 21 21 21 inches 3 4 3 i 1 1 li li n 2 2 2 2 24 24 2i 2i 3 inches 3 3 4 l 1 ■■■4 1 1 ■■■4 li ij 2 2 2 24 24 24 24 3 3 inches i f 1 1 li li 14 14 2 2 24 24 24 inches 4 4 f ) 000 000 000 200 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS The above table is based on single-conductor double-braided rubber-insulated wire and unlined metal conduit. All wires No. 8 and larger are stranded. The conduit sizes are given for runs up to 100 feet with not more than four right-angle bends between outlets. For longer runs larger conduits are used. LEAD ENCASED CABLE IN UNLINED METALLIC CONDUIT ■ffIHE AND CABLE SIZE (B. & S. GAUQE, TWO WIRES SAME SIZE THBEE WIRES SAME SIZE FOUR "WIRES SAME SIZE THREE WIRES DOUBLE SIZE NEUTRAL 8 inches n u 2 2 2 2 2 2i 2i 2i 2i 3 3 inches 14 2 2 2 2 2i 24 24 3 3 3 3 34 inches 14 2 2 24 24 24 3 3 3 3 3 34 34 inches 14 6 2 5 2 4 24 3 24 2 24 1 3 3 00 3 000 3 0000 250 000 300 000 OUTLETS The standard types of stamped steel outlet boxes suitable for rigid conduits are used. No conduit larger than f inch is con- nected to any outlet box, and not more than four connections are made to any outlet box. Outlets are located with reference to the architectural treat- ment and the construction of a building. This generally requires symmetrical spacing. Ceiling outlets are used for general illumination, and bracket outlets only where space restrictions demand, i.e., small toilet- rooms, stair landings, low ceilings, etc. As a general rule, ceihng outlets in the same space supply from 100 to 300 square feet of floor area. CONDUIT AND WIRING SYSTEMS 201 n general, the capacity of a ceiling outlet does not exceed 300 its; a bracket outlet, 50 watts; a receptacle, 50 watts. Bracket lets in court rooms, in lobbies, on exterior of building, etc., y supply 100 or more watts. Court-room and lobby ceiling lets, where the total number of outlets is restricted by the hitectural treatment may have a greater capacity than 300 tts, and such outlets sometimes require more than one circuit, looms less than 20 feet square have one ceiling outlet. Rooms sr 20 feet in either dimension have two or more ceiling outlets ced on the longer dimensions, the number of rows of outlets ag governed by the width of the room. n the post-office workroom, a space about 3 feet adjacent to screen is considered to be sufficiently lighted by the brackets the screen, and this area is deducted from the total area of : room when calculating the illumination, n locating outlets in large office rooms consideration is given the possibility of such rooms being subdivided at some future le. The location of ceiling outlets in court rooms and in main lob- s depends very largely upon the design of the ceilings and other hitectural features of these spaces. I!eiling outlets are located in the centers of squares whenever tcticable. ;t is considered that approximately uniform illumination is ob- Qed when the distance between the outlets is equal to twice ! height of the lamps above the plane of illumination, using re- itors which direct the greatest portion of the light downward ,hin an angle of 60° from the vertical and with the maximum jarent candle-power at about 45° from the vertical. )utlets near beams are located a sufficient distance from the i.m to admit of placing a standard 4-inch outlet box, and if the ims project below the ceiling the outlet is located a minimum L2 inches from the center of beam. If a beam is directly over ecessary or very desirable location for an outlet, an effort is de to have the structural engineers substitute two channels h a IJ-inch space between the same for the single beam. )utlets are not placed within 6 inches of heating mains or other ^e piping. Veiling outlets are not placed on skylight frames unless this is 202 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS absolutely necessary, and then the architectural draftsman is called upon to give special construction of the frames to accom- modate the conduit and gas piping, outlet boxes, canopies, etc. Combination ceiling outlets are not used where ceiling heights are less than 8 feet 6 inches. The standard height of bracket outlets is 7 feet above the floor, but they are frquently placed higher in court rooms. Bracket outlets are located so that the fixture canopy will seat on a smooth plane surface not less than 5| inches wide. Bracket outlets are provided over each window in the post- office screen. Bracket outlets are provided on the lock-box sec- tion also, on the basis of one outlet for each 4 to 6 feet of length of the box section. To supply the local illumination of furniture in the post-office workroom, junction boxes with closed covers are set out fully exposed on the basement ceiling. One box is provided for each 300 square feet of floor area, and each box is rated at 300 watts in calculation of wire sizes. Receptacle outlets for local illumination are placed in walls of all office rooms, and also in floors of the principal offices. The floor outlets are located on center lines of rooms, longer dimension, and one floor outlet is provided for each 250 square feet of floor area when more than one such outlet is needed. Desks are generally placed so as to receive a maximum amount of daylight, and this guides the selection of the locations for wall outlets which are generally located in exterior walls. One such outlet for each window of the average office is provided unless conditions indicate the need of a greater number. Money order and registry rooms have two or more wall outlets. An outlet is provided in each elevator and lift shaft, and located near center of travel of car. A plug receptacle is provided in the floor under each end of the judge's bench. A plug receptacle is also provided for the clerk's desk. Combination bracket outlets are provided over the wall writing desks in public lobby. These outlets provide gas burners for emergency lighting, as combination ceiling fixtures are rarely installed in lobbies or corridors. Gas only or combination brack- ets are also installed in basement and in corridors on upper floors for emereencv use. CONDUIT AND WIRING SYSTEMS 203 Dutlets on portable lobby desks are so connected that tearing of floor to place conduit will not be necessary; a junction box iet on basement ceiling near probable location of riser to desk icket, and the horizontal run of conduit from box to desk riser exposed on basement ceiling. The outlet for the elevator circuit is generally connected on a sement circuit which supplies outlets in boiler room. The special junction boxes on the basement ceiling are con- 3ted two on a circuit; or, in case of an odd number, one or •ee per circuit. Branch circuits are connected so that the loads on the two es of the 3-wire circuit will be approximately balanced. Dutlets in public toilets and in attics are connected on corridor cuits. [ndependent circuits are provided for post-office screen outlets. Lobby outlets, outside entrance outlets, and basement out- 3 not in spaces connected with post-office working space are mected to a tablet in basement or in the smaller buildings to i workroom tablet. The outlets for lobby desks are connected to either the work- )m or basement tablets. [n court rooms an independent circuit is provided for the out- 3 at the judge's and clerk's desks, and if conditions require D circuits are provided to each ceiling outlet. Dutside fixtures at each entrance are usually connected on a larate circuit, but where the fixtures are small those at two irances are connected on one circuit, each entrance being con- lied by a snap-switch. I^ead-covered, rubber insulated wire is run from junction boxes t inside wall in basement to outdoor lights at main entrances. \. plug receptacle is provided on exterior of each vault in the Iding, near lock side of door; and if the vault exceeds 80 square t in floor area a ceiling outlet box is provided in vault with a eptacle just inside of vault door, so that the inner and outer eptacles may be connected with a flexible cord when desired. )utlets are located in the roof space or attic, as judgment dic- 3S. Ample illumination is provided for the overhead sheaves elevators. )utlets for ceiling fans, allowing one outlet for each 600 to 800 i?- _j_ _j? n : J - J r j.1- x ^cci^. i_ 204 MECHANICAL EQUIPMENT OF FEDBKAL BUILDINGS room. These outlets are connected two or three on a circuit to the workroom tablets. Ceiling fan outlets are never connected on the same circuit with lights. Each branch circuit is controlled by a double-pole fused knife- switch located on the distributing tablet. Except for the post-office workroom and general basement and unfinished attic or roof spaces, all ceiling outlets and all bracket outlets are controlled by snap-switches. Snap-switches are single- pole push-button flush type, and are set 4 feet above the floor; and those in public lobby have lock attachment. Snap-switches in rooms are located near the entrance door cas- ing on the lock side. Large rooms which have two entrance doors from corridor and more than one ceiling outlet have a snap-switch at each entrance door. Switches controlling large spaces and long corridors are frequently placed in gang boxes. Switches are not located in partition walls less than 4 inches thick, and are so placed that the face plate will seat on a smooth plane surface. A uniform size 10-ampere fuse is used for all branch circuits. The smallest wire used in branch circuits is No. 12, and in lighting fixtures the smallest wire used is No. 16 B. and S. gauge. The sizes of fuses for feeders and sub-feeders are selected to corre- spond to the carrying capacity of the wires which the fuses pro- tect. In case of a small switch controlling a large cable the size of the fuse is adapted to give protection to the switch. GENERAL ILLUMINATION In computing the number of watts required for a certain area the well-known formula recommended by the National Electric Lamp Association may be used: -rjTT ,, _ Floor area in square feet X foot candles Effective lumens per watt It is convenient to solve directly for the number of lamps for a given area; so the following formula is used: ■^, _ Area in square feet X lumens per square foot Lumens per lamp CONDUIT AND WIRING SYSTEMS 205 The lumens per lamp used are those given by the various ip manufacturers. The lumens per square foot for general illumination, using ect lighting for the several classes of rooms are as follows : CHARACTER OF SPACE LUMENS PER SQ. FT. NEW BUILDINGS LUMENS PER SQ. FT. OLD BUILDINGS .ler, Store and Machinery Rooms. ilets, Halls, Corridors, Vesti- ules, etc 0. Workroom ney Order and Registry Rooms. . in Lobby and Main Stairs dl Service Rooms ice Rooms urt Rooms ing Rooms and Jury Rooms Outlets spaced 14 ft. on centers 3.0 7.5 and special 7.5 and special 6.0 7.5 7.5 and special 7.5 5.0 14 ft. centers 3.0 10.0 and special 10.0 and special 6.0 10.0 10.0 and special 10.0 5.0 Che plane of illumination is taken as 2 feet 6 inches above floor in all les. For indirect and semi-indirect lighting the values given for new building )uld be doubled. The following table gives the effective lumens per watt for e lamps and reflectors used: Lamps Walls L Tungsten (vacuum) Light 5.0 Tungsten (vacuum) Dark 4.2 Gem Light 2.0 Arc lamps Large areas 3.0 Tungsten (gas filled) Light 6.0 to 9.0 The above values apply to small and medium size rooms, ■ry large rooms are given special consideration. WIRING The standard wiring for lighting in all buildings is 3-wire feed- 3, 3-wire sub-feeders, and 2-wire branch circuits. This may be ried to suit local conditions, as in a 4-wire distribution system e four wires will be brought to main feeder tablet or switchboard d 3-wire feeders run from this point to distributing cabinets. 206 MECHANICAL EQUIPMENT OP FEDERAL BUILDINGS The even-number wire sizes are used for feeders and sub-feeders smaller than No. 5. In the smaller buildings the fewest possible numbers of wire sizes for feeders is used. All branch lighting circuits are No. 12 B and S., except circuits to the special junction boxes on basement ceiling for furniture lighting, which are made No. 10 B. and S. The maximum allowance for branch circuits is 800 watts ex- cept in post-office workroom where the maximum is 660 watts. All lighting feeders and sub-feeders (or mains) are calculated on the following basis: The assumed lighting load is the total watts for general illumi- nation plus the total watts for local illumination (50 watts per receptacle) plus one watt per square foot of post-office work- room floor space. Load factors for small buildings, one to one and a half stories. Feeders Full connected load Sub-feeders Full connected load Load factors for buildings containing more than four distributing tablets. Feeders 70 per cent of connected load Sub-feeders 80 per cent of connected load Sub-feeders to workroom and court-room tablets are calcu- lated for full load in all cases. Voltage drop. per cent Feeders 3 Sub-feeders 2 Branch circuits 1 Feeders and sub-feeders for all buildings containing not more than three distributing tablets are calculated on the basis of 2- wire circuits and 110 volts. The wire size given by formula is the neutral, and each outside wire is one-half the neutral size, so that the systems may be used either for 2-wire or 3-wire service. No feeder or sub-feeder neutral wire is less than No. 8 B. and S, or larger than 300,000 cm. CONDUIT AND WIBING SYSTEMS 207 i'^here a building contains more than three distributing tab- and the supply system is the usual 110-220 volt 3-wire system, .raight 3-wire system 110-220 volts is used up to the distribu- cabinets. The wires are calculated for outside volts, and the tral wire is made the same size as one of the outside wires. ; feeders and sub-feeders are calculated for full-connected load, . with 2 per cent drop in sub-feeders and 3 per cent drop in in feeder. 'he three wires of a 3-phase circuit and the four wires of a 2- ,se circuit are all made of the same size, and each conductor f the cross-section given by the formula hereinafter stated. >ranch circuits to single arc lamps are increased 50 per cent to vide for the extra current at starting. 'he carrying capacity of all feeders and sub-feeders at the load iors given is not to be less than hereinafter stated, regardless ;he voltage drop. This requirement will generally determine wire size, but in all cases the voltage drop on feeders and sub- lers is calculated. As a rule, the drop is less than the allowed simum in sub-feeders 60 feet long and under, and in main lers 100 feet long and under. WIRING FORMULAE AND TABLES 'eeder and fuse sizes for direct current motors are calculated a current of one and one-half times the full load running rent of the motor and the wire size is selected from table A. ge 210.) 'or alternating current motors feeder and fuse sizes for motors ler 5 horse power are figured at three times the full load cur- t and for motors 5 horse power and over at twice the full load rent and wire size is selected from table B. (Page 210.) *urrent for single phase motors _ Horse power X 746 Volts X power factor X efficiency" iurrent for two phase motors is one-half the above and for 3 se motors .58 times the above. 'he product of the efficiency and power factor may be taken 208 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS Horse power Efficiency of motor power factor 1 0.30 2 0.34 3 0.38 4 0.42 5 0.46 74 0.50 10 0.55 15 0.60 20 0.65 25 0.70 30 0.70 If the feeder is more than 100 feet long a larger size should be used to keep the drop within the 2 per cent allowance for sub- feeders. The formula used when calculating direct-current work is as follows : CM = D X I X 21.6 For single phase alternating current circuits where all wires are in same conduit: £> X 7 X 21.6 VXP.F. ■ D = distance one way in feet. I = line current in amperes at lamp voltage. V = actual volts drop in transmission. P.F. = power factor. When this formula is applied, it will give the size of conductor for a 2- wire transmission. If the 3-wire system with the double neutral is desired then this gives the size of the neutral conductor, and each outside is to be made approximately one-half the size of the neutral. If the Edison 3-wire system (all conductors of the same size) is desired, then the same formula is applied with the following changes : CONDUIT AND WIRING SYSTEMS 209 I = total watts divided by twice the lamp voltage, or I = the current in either of the outside conductors of the Edison 3-wire system. V = twice the actual volts drop if the power is transmitted by a 2-wire system. bese different calculations are based upon the same percentage of voltage in transmitting the power. I direct-current circuits the volts drop per wire = IR, and total volts drop = 21 R. I is the current per wire, and R is resistance in ohms per wire. I alternating-current circuits the volts drop depends on both resistance and reactance but with wires close together as in luit work the reactance will generally be small and may be ected. However, for all alternating-current circuits the ac- volts drop may be calculated at the assumed power factor, ,, and corresponding current, using the following formula : Volts drop per wire = IR -i- P.F. Volts drop, single-phase circuit = 2 (volts drop per wire) . Volts drop, 2-phase circuit = 2 (volts drop per wire) . Volts drop, 3-phase circuit = 1.73 (volts drop per wire). 1 direct-current circuits the volts loss in per cent is the same he per cent power loss. This is not the case in alternating- ■ent circuits except at unity power factor. . convenient method of determining wire sizes is to ascertain ; the current per wire and select a wire size which has this acity; then calculate the volts drop for the wire thus selected. POWEE FACTORS^LIGHT AND POWER per cent Incandescent lamps 95 Arc lamps 70 Incandescent lamps and induction motors 85 Induction motors, full load 80 Induction motors, constant speed type, starting 60 Induction motors, elevator type, starting 70 'he power factor of an unbalanced 3-phase circuit is obtained n the following formula: 210 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS Power factor, three phase, Total real watts Volts across lines X average amperes per phase X 1-73 WIRE AND CABLE DATA— CONDUIT WORK SIZE, B. AND S. SIZE, CIECULAR MILS SAI'E CAHRYING CAPACITY IN AMPERES RESISTANCE, OHMS PER 1,000 FEET AT 68° F. A B 14 4,107 6,530 10,380 16,510 26,250 33,100 41,470 52,630 66,370 83,690 105,500 133,100 167,800 211,600 250,000 300,000 15 20 25 35 50 65 70 80 90 100 125 160 175 226 250 275 20 25 30 50 70 80 90 100 126 160 200 226 276 325 350 400 2.5200 12 1.5900 10 0.9970 8 0.6270 6 0.3940 5 4 0.3130 0.2480 3 0.1970 2 0.1560 1 0.1240 0.0981 00 0.0778 000 0.0617 0000 0.0489 0.0414 0.0345 The preceding is used for both interior and underground cir- cuits, and for all kinds of insulation. Column "A" is always used except for alternating current motors, when column "B" is used. Switchboards. In designing switchboards an attempt is made to keep the size of the panels as closely to standards adopted by the various manufacturers as possible. The majority of switchboard manufacturers make their panels 20 inches, 50 inches, and 70 inches high, and the widths of panels are made 16 inches, 20 inches, 24 inches, 32 inches, and 36 inches. The thicknesses are 1^ inches, 2 inches, and 3 inches. The specifications usually state that the switchboards shall not be less than 62 inches nor more than 70 inches high and that panels must not be less than 24 inches nor more than 32 inches wide, and the thickness not less than IJ inches nor more than 2 inches. CONDUIT AND WIRING SYSTEMS 211 ESTIMATING DATA The average total cost of lighting systems for new buildings, tiplete in place, can be figured at about $12 per outlet in tern sections of the country, $15 in the west and south, 1 $20 in the extreme west. Conduit and wire in place 1 average about 12 cents per foot for all sizes. This includes let boxes, but does not include, switches, receptacles, cabinets I tablets, etc. These figures are based only on the number of actual lighting ilets, switch outlets not being included. ^ov old buildings the cost of the work will be about $25 per let in the extreme west, and from $20 to $25 per outlet in er sections. Estimating in detail. The total amounts of conduit and wire the lengths scaled on the plan plus the following: Number of ceiling outlets x 2 feet. Number of bracket outlets x 10 feet. Number of switch outlets x 10 feet. Number of baseboard outlets x 4 feet. Number of 2-gang switches x 15 feet. Number of 3-gang switches x 20 feet. The average length of branch runs in Federal buildings is 50 t. Jranch conduits | inch; branch circuits in Federal buildings No. 12 B. and S. duplex wire. I'or obtaining lengths of feeders make a diagram of all feeder I sub-feeder circuits. Materials. 'onduit in place in new building, per 100 feet. i inch 17 .00 f inch ; 9.00 1 inch 13 . 30 U inch .18.00 1| inch 21 .50 2 inch ' 29 .00 2i inch 45 .60 3 inch 60 .00 212 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS Add 50 per cent to above for underground service connections in place and for work in old buildings where walls and ceilings are cut and plaster must be replaced. Conduit elbows in place, each: 2 inch $1 .00 24 inch 1 .25 3 inch 4.00 4 inch 10.00 Outlet boxes in place, all kinds, each: In new buildings 0.25 In old buildings where plaster must be repaired 0.50 Large junction boxes, per pound, in place .05 Plug receptacles in place, each 1 .90 Snap switches (single-pole 10-ampere), in place, each 1 .40 Fixture studs, each, in place .05 Double braided rubber-insulated wire, in place per 1000 feet: 16 cent base Solid single conductor: Size, B. & S: 16 15.00 14 18.60 12 23.40 10 30.40 Size, CM.: 250,000 460.00 300,000 530.00 400,000 670.00 500,000 814 .00 Stranded single conductor: 8 47.40 6 70.00 4 95.50 3 113.00 2 132.00 1 172.50 210.00 00 250 .00 000 300.00 0000 362 . 00 CONDUIT AND WIRING SYSTEMS 213 Duplex conductors: 14 $36.00 12 45.70 10 60.00 8 79.50 Telephone cabinets, special office design, in place, each. . . 20.00 Outlet bushings, each, in place .05 Lock nuts, each in place .01 (Estimate three bushings and three lock nuts per outlet.) Reinforced silk-covered lamp cord. No. 16, per 1000 feet, ^ in place 55.00 Knife switches, 250-volt, single-break, with extension for fuses unmounted, polished: Capacity Double-pole Triple-pole 30 1.40 1.90 60 1.80 2.75 100 3.60 5.25 200 5.40 8.15 400 12.20 18.60 600 17.15 26.00 800 28.00 42.00 1000 32.20 48.60 1200 38.00 67.50 Cost of mounting, not including drilling of marble, per switch $1 .00 to $10 .00 Enclosed fuses in place, each : 3 to 30 amperes 0.16 35 to 60 amperes.. 0.22 65 to 100 amperes .57 110 to 200 amperes 1 .25 225 to 400 amperes 2 .30 450 to 600 amperes 3 .60 Bus-bars for switchboards, per pound, in place 0.60 Structural steel work for switchboards, per pound, in place. 0.10 Blue Vermont marble, 2-inch thick, per square foot 2 .00 Slate panels, Ij-ingh thick, per square foot 0.50 Drilling holes, slate and marble, each .25 Labor on switchboard panels, each : In shop 25 . 00 At building 12.00 Total $37.00 214 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS Tablets and cabinets (office special design), per switch $5.00 To actual cost of tablets, if ascertainable, add for installa- tion, per circuit 1 .00 Motor connections, 5-H.P. and under, per H.P 2.00 Motor connections, from 10-H.P. up, per H.P 1 .00 Railroad fare on average Federal building 50.00 Board per man, per day 1 . 00 Freight, 3 per cent of total cost of material and labor. Superintendence, 1 per cent of total cost of materials and labor Profit, 20 per cent of total cost of materials and labor. Especial attention is called to the fact that the foregoing figures are correct for certain special conditions in new Federal buildings, but are not applicable under all conditions. Used with judgment they give accurate results. CONDUIT SYSTEMS FOE TIME CLOCKS AND OTHER SPECIAL PURPOSES The office has discontinued the installation of standard clock systems except in special cases. In the larger buildings, how- ever, where a conduit system for signal wires is installed, these conduits could be used for clock wires, if desired. The standard time clock systems formerly installed in Federal buildings under control of the Treasury Department, consisted of a master clock operating, by means of electricity or air pressure, secondary clocks located throughout the building. The sec- ondary clocks contained no driving mechanism proper, being driven, solely by impulses from the master clock, and did not re- quire winding, oiling, or setting. The master clocks for the pneumatic systems were either self- contained or used a water-operated compressor which automati- cally maintained a constant pressure in a storage tank . The master clock operated a valve once each minute, thus forcing air to travel through the piping and operate the secondaries. In the electric systems, the secondary clocks were provided with electro-magnets connected in series. The master clock was provided with a circuit-closer which automatically closed the cir- cuit (or relay) once each minute. The magnets in the secondaries were thus energized, and the armature which was attracted moved the hands forward one minute. CONDUIT AND WIRING SYSTEMS 215 'he secondary clock circuits for the electric system, if not e than three, were supplied through relays located in the iter clock. Each circuit was fitted with a small telltale clock mted in the master clock. luildings with twenty or more office rooms (including post-office kroom, money-order room, and lobby), were provided with a iplete conduit system for clocks. Tot more than twenty-five secondary clocks were installed on circuit, and the circuit began and ended at the master clock. Duildings where there were more than twenty-five secondaries y were grouped on different closed circuits, with not more n twenty clocks on a circuit. The various circuits contained, ;re practicable, the same number of clocks, and each circuit ; connected with the master clock outlet, which was connected the junction box in the vault protection service conduit just de of basement wall to permit connections at this point to the tery, or to the lines of the telegraph companies for synchro- ing the clocks. Jl conduit systems were |-inch diameter, and the clock outlet :es were of special design. The conduits were arranged for pulling in of wires, or of lead tubes for the pneumatic system. ?he master clocks were of the wall type and were located in post-office workroom in such position as to be visible from all ts of the room, care being taken that near-by columns, sus- ided lookouts, etc., did not obstruct the view. Master clock es varied in size from 64 inches to 90 inches in height and from inches to 24 inches in width. L secondary clock was located in each office room throughout building, in the carriers' swing room, the money-order and reg- \ry division, and the court room. The clocks in office rooms were installed over doors if ceihng ghts permitted. In rooms which were long in proportion to ir width, the clocks were located on an end wall in preference a side wall. In extremely long rooms a clock was placed at h end of the room. Clocks in court rooms were placed so as be easily seen from the judge's desk. The weight of the average size electric and pneumatic second- • clock used was 4 pounds. For ordinary office rooms where distance from the clock to any point in the room did not ex- 216 MECHANICAL EQUIPMENT OP PEDERAL BUILDINGS ceed 40 feet, clocks with 12-inch-diameter dials were installed. Where the distance was greater, 2 inches were added to the di- ameter of the dial for each additional 10 feet. The standard sec- ondary clock with 12-inch dial was 17 inches x 17 inches outside dimensions. In court rooms and rooms over 14 feet high, the size of the clock dial was determined as above when the clock was to be set 10 feet above the floor. For greater heights above floor, the diameter of the dial was increased approximately 12 inches for each addi- tional 10 feet. The architectural treatment of the walls received consideration in deciding upon the size of the clock dial. The clocks usually had a 12-inch dial, Arabic numerals, and an oak case. TOWER CLOCKS Three types of tower clocks are in use on Federal buildings; mechanical, electrical, and pneumatic. The mechanical tower clocks used have generally the ordinary clock mechanism operated by weights, wound up by hand once a week. This is the cheapest form of clock, and is reliable. The present practice is to require that the mechanical clock weights be automatically wound by means of a motor operated on the lighting circuit or by storage batteries. All clocks are provided with a pilot clock so that the hands may be set from the clock room, and the pilot clock is provided with a second-hand.' In order to equalize the cost of the mechanical clock with the other two systems, a clock is placed in some part of the building and operated electrically as a secondary from the tower clock. All types of tower clocks used are provided with a device for automatically switching on and off the lighting system installed for illuminating the clock dial or dials; and all are guaranteed to vary not more than thirty seconds per month. The pneumatic system consists of a hydraulic air compressor and galvanized steel air storage tank, with a master clock located in some part of the building, from which the tower clock is oper- ated as a secondary. If a building is equipped with an electric clock system the tower clock is operated as a secondary from the master clock, the same as any other secondary. CONDUIT AND WIRING SYSTEMS 217 If a building has no clock system, a master clock is installed in the post-office workroom or custodian's office, and the tower clock is operated therefrom as a secondary. The hands of the electric tower clock are operated by a small motor controlled by the master clock, and this motor is wound for 20 to 25 volts and operated by 40 wet cells, which will run the motor one year. The tower clock mechanism occupies a space about 24 inches X 24 inches in plan, and for the electric system the mimimum dis- tance from the center of the clock dial to the stand for supporting the mechanism is not less than 24 inches. The electric clock mechanism weights about fifty pounds, and is, when possible, located in a room protected from the weather; otherwise it is installed in a glass case. In the event a bell and striking mechanism is desired in con- nection with a tower clock, it is located in a room above or below the clock mechanism, or in same room if necessary. The striking mechanism weights about forty pounds. The room for the bell has large openings extending from floor to ceiling to permit the egress of sound. If louvres are used they are widely spaced and backed up with wire grills. A bell room 6 feet x 6 feet in plan and 7 feet to 8 feet high is the standard size. The bell room is made not less than 10 feet higher than the roof of the building. The floor and ceiling of the bell room have mineral wool deaden- ing between joists if wood construction is used. The space occupied by the bell and its supporting stand is ap- proximately 6 feet x 6 feet in plan for a 2000-pound bell. On ac- count of hills, street noises, etc., no definite rule can be laid down as to how far a bell can be heard, but under ordinary conditions a 1400-pound bell can be heard one mile, and a 2000-pound bell two miles. In small Federal buildings a 1400-pound bell is installed, and in the larger buildings a 2000-pound bell. Chimes or peals are not used. The clock dials are made 3 feet diameter for towers up to 30 feet high. For each additional 10 feet one foot is added to the diameter of the dial. The tower clock hands are made of aluminum. If a bell is installed with a tower clock, and no other secondary 218 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS clocks are used in the building, the wet batteries for the clock motor can not be used, as the striking mechanism takes too much current; therefore a storage battery is installed, which is charged from the lighting or power service of the building. If only al- ternating current is available, a rectifier is used and a charging tablet is installed, on which is mounted a double-throw switch, voltmeter, ammeter, reverse current relay, and a bank of resist- ance lamps for charging the storage batteries, consisting of 12 cells each, rated at 4 amperes for eight hours. The proper illumination of tower clock dials is difficult to ar- rive at, and generally expensive to maintain. The office has abandoned its former practice of placing a ring of lights about 2 feet back of each clock face, as a dark spot will appear on the dial if one light goes out, and the dial will have a spotted effect even with all lights burning. It is better to drop down from the center of the ceihng of clock room with a conduit and place a ring made up of conduit and condulets, or regular boxes with re- ceptacles, to form a large cluster, and install 40-watt or larger tungsten lamps, with x-ray reflectors. An abundance of light is necessary, approximately 15 candle-feet on the dial being required. The walls and ceiling of the clock room are given three coats of lead and oil or white enamel paint to increase the reflection. A good way to illuminate clock dials where room is small is to treat the walls of clock room as noted above and drop two large tungsten lamps in center of room, same to be on separate circuits and each large enough for excellent illumination of dial. ESTIMATES OF COST OP STANDARD TIME CLOCK SYSTEMS Cost per cell (new) $1 .50 to $2.00 Voltage per cell 0.6 to 0.7 volts Life of cell, approximately 300 ampere hours Length of contact made by master clock J second Voltage required per secondary clock, approxi- mately 11 volts Amperes required per circuit 1 ampere The number of cells required for operating electric secondaries is equal to twice the largest number of clocks on any one circuit. For preliminary estimates it is sufficiently accurate to allow about $25 per secondary clock and add $200 for the master clock. CONDUIT AND WIRING SYSTEMS 219 Of the $25 per clock, $15 may be taken for the clock and wiring and $10 for the conduit system. This will give about the lowest cost, and the estimate should be increased from 10 to 20 per cent in remote cities. One thousand feet of ^-inch conduit in place costs approximately $70 in new buildings, and $200 in old buildings where cutting is needed and plaster must be patched. One thousand feet of No. 16 wire in place costs approximately $15. The outlet boxes now used in Federal buildings cost about 25 cents each in place in new buildings, and 50 cents in old buildings. The cost of hanging and connecting an electric secondary clock is about $1.50. Connections are made into top of clocks. The cost of an average electric tower clock with no other sec- ondaries, including dial, hands, mechanism, batteries, master clock, etc., complete may be taken at about $1250. This does not include cutting for clock dials, or other structural work. The mechanically operated tower clocks will average about SIOOO. For striking mechanism, including 2000-pound bell, add $1200. Bells will average 50 to 60 cents per pound at factory. FIRE ALARM AND WATCHMAN's TIME-DETECTOR SYSTEM In buildings with fifty or more office rooms, a conduit system for fire-alarm apparatus and a conduit system for watchman's time-detector are installed. For the fire-alarm system two outlet boxes, one above the other, are provided at each station; the lower being about 60 inches above the floor and the upper one 2 feet below ceiling. These boxes are located at various appropriate points in the corridors and else- svhere, and are joined in series by 1-inch conduit. The conduit- system begins and ends at a large junction box in the engine room. From this junction box a conduit is run to the place where ihe batteries are to be located. For convenience, the boxes on :he several floors are located in vertical rows, and a single riser is run through all the boxes in that vertical row. These risers are jross-connected in the basement. The upper outlet used on the fire-alarm system is similar to the regular switch outlet box, or the regular ceiling outlet box with 220 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS brass cover with a bushed opening for connection to a gong. The lower box is 12 inches wide by 17 inches high by 6 inches deep, clear inside, made of steel with a steel cover fiush with plaster line and secured to the box with tap screws. Outlet boxes for the watchman's time-detector system are lo- cated in remote corners of the public portions of the building, pre- ferably in vertical rows, and connected by 1-inch conduit similar to the fire-alarm boxes. These risers are run to a common junc- tion box located in the office of the assistant custodian, and from said box a 1-inch conduit is run to the place where batteries are located. Watchman's clock and fire-alarm systems use No. 16 and No. 18 wire. There is one more wire in the conduit than there are stations on the Une. The watchman's boxes are 5 inches wide by 8 inches high by 6 inches deep, clear inside, and made of steel with a steel cover set flush with plaster line and secured with tap screws. The cost of these systems will average $10 per outlet. VAULT-PROTECTION SYSTEM All Federal buildings are provided with a conduit system for the reception of the wires of an electric vault-protection system. The wiring for each vault consists of a cable which leads to a common junction box for all vaults, which is located in the base- ment. From this junction box a conduit, never less than 1^ inch diameter, is run underground to the service pole and up in- side of same to the top. A |-inch conduit is also taken from this junction box and run to a point selected for alarm gong near ceil- ing of the post-office workroom. From the junction box in basement a f-inch diameter conduit is run to each vault in the building with a steel outlet box located near door trim on the exterior of the vault about 4 feet 6 inches above the floor, and a box is located near the ceiling on the inside of the vault near entrance door. The size of the main service conduit from the junction box to the pole is such that the 4-pair cables from each vault when grouped and formed into a cable will not fill more than two-thirds of the conduit. CONDUIT AND WIRING SYSTEMS 221 In the larger buildings the vault protection main service con- luit is used to bring in the telegraph wires for the Weather Bureau lervice and also the clock and messenger call-bell wires from the ;elegraph companies. The entire cost of this system will average $20 per vault. The viring in the conduits is supplied by the companies furnishing the iervice. TELEPHONE AND CALL BELL CONDUITS A conduit system for telephones and call bells is installed in all Federal buildings, and is so arranged that intercommunicating telephone systems may be installed if desired. As previously stated, in the small buildings the main service 3onduit for the vault protection service is used to bring in the nain telephone wires to the junction box in basement. From this junction box in small buildings a 1-inch conduit is run to a tele- phone junction cabinet centrally located on first floor; and from the junction cabinet radiate separate |-inch diameter conduits to the various ofiice rooms and stations. The standard size of telephone junction cabinet is 24 inches svide by 18 inches high and 3 inches deep, and it is constructed Df sheet steel with a steel frame and hinged door with lock and key. The outlet boxes for telephones are steel, and are provided with a, cover of brass for bushed hole in same. Small buildings are those in which the number of stations is less than 23. A large building has 23 or more stations, with provision for switchboard with operator. •In the large buildings, if there is only one telephone company in the city, a main service conduit never less than l|-inch diame- ter is run from the building underground to the nearest pole of bhe telephone company, terminating 10 feet above grade with cpeatherhood. Where there are two companies two conduits are run, one to the pole of each company. Where a switchboard is to be installed the architect must ar- range for a room not less than 10 by 12 feet, with good natural light, located if possible on the first floor near to the cable termi- Qal room in basement. 222 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS The terminal room is arranged to receive all conduits from risers and from service poles. The telephone company will provide the terminal board, but the conduits should be arranged to per- mit the terminals being inclosed within a wooden cabinet. Ter- minal boards cover approximately, for each 100-pair cable distrib- uted, a space 9 inches wide and 4 feet long by 12 inches deep, but boards are usually arranged to be square for sizes less than 100 pairs. The service conduit enters at the center at bottom, and all risers and conduits to switchboard room leave at the top of board. The riser conduits are not less than l|-inches, and switchboard conduit is 2 inches. The horizontal runs of riser conduits exposed on basement ceiling have a pull box after every two bends and at the foot of each vertical riser. Riser conduits enter the bottom of junction cabinets and leave at top to con- nect to the next above. All branch conduits from cabinets are § inch and leave at the bottom. No more than 20 conduits ara run from one cabinet. In office rooms an outlet box is installed in center of room. Where wood floors are specified, removable floor boards are pro- vided by the architect every 7 feet. These boards are without tongue, screwed to nailing strips, and have in the center of the under side, running lengthwise, a slot about | inch deep and f inch wide. These slots are connected to the floor box by a f inch conduit having a bushed end under the board. This arrangement will permit reaching desk locations at any part of an office with- out the wiring being exposed. Where composition floors are specified an outlet in center of room and one just above the baseboard are provided. The wall outlet is used to carry the wire to the baseboard for running around room to desks, and not for a wall phone. Where two companies exist, two riser conduits between cabi- nets, two terminal boards, and two main conduits to switchboard room, terminated in opposite ends of room, are provided. Only one distribution cabinet and one branch conduit to each room are, however, provided in this case. Each junction cabinet will accommodate the equipment for distributing a 25-pair cable. In determining the cost of installing a branch exchange in a Federal building the following facts were considered : CONDUIT AND WIRING SYSTEMS 223 Salary of operator, per annum $600 ,00 Rent of switchboard, per position per annum 24.00 Rent of trunk lines, about 3, at $24 each 72 .00 Messages, 2400 per annum minimum amount, at 2§ cents each 60.00 22 stations on board, at $6 per annum each 132 .00 (Where phones are located outside of main building, or private trunks exist between departments, add $24 for each such station.) Total cost of phone service per annum for switchboard and operator $888 .00 One operator is provided for every 50 stations. Where a single line phone service is furnished, giving 600 calls per phone, the cost for 22 phones would be as follows : 22 at $39 each , $858 .00 And 23 at 39 each 897 .00 As the telephone conduits are sometimes used for call bells, a l|-inch conduit is run between junction cabinets on each floor above the first, the conduits entering cabinet at opposite end of bottom to that used by the riser conduit. A special call bell system is installed for the post-office section of the building, with outlets located as follows : Near mailing platform on wall. Screen near general-delivery window. Center of post-office workroom. Money-order and registry room on wall. Carriers' swing room on wall. Boiler room on wall. Postmaster's room in floor and wall. Assistant postmaster's room in floor and wall. To care for the battery leads of this call bell system a |-inch conduit is run from the junction cabinet to a suitable location in boiler room. Call bell outlets on screen are placed 4 feet from floor, and in an unfinished basement rooms near the ceiling. The cost of telephone conduit systems will average about $10 an outlet. WEATHER BUREAU SPECIAL CONDUITS In all buildings in which offices are assigned to the Weather Bureau, a large-size floor outlet box with brass cover is placed 224 MECHAJSriCAL EQUIPMENT OF FEDERAL BUILDINGS in the main office room of the Bureau, and a similar outlet box of waterproof type is located on the instrument platform on the roof of the building, these two boxes being connected by a 2-inch ■ conduit for the reception of the instrument wires. The special outlet boxes are generally 6 inches square and 4 inches deep, and the cover of floor box in office room has an opening tapped in same for IJ-inch conduit connection. In addition to the above, a conduit is run from the nearest cabinet and tablet of the lighting system of the building and is extended to the instrument platform on the roof and provided with a weatherproof outlet box at that point. One lighting cir- cuit is installed in this conduit. In buildings located on navigable waters, and which are pro- vided with quarters for the Weather Bureau, in addition to the above conduits a conduit is run from the nearest lighting cabinet and tablet to a weather-proof box on instrument platform. This conduit contains two lighting circuits which are controlled by snap-switches in the Weather Bureau office. In all cases a 1-inch conduit is taken from the vault-protection junction box previously noted and run to a floor outlet box in main Weather Bureau office for the reception of telegraph wires and messenger call-bell wires. CONDUIT FOR SIGNAL SYSTEMS In all buildings containing a court room, a conduit system is installed for the reception of wires for call-bells, intercommuni- cating telephones, etc., between various portions of the building. The system consists of two 1-inch conduits, running parallel, and interconnecting floor boxes of special design located at vari- ous points throughout the building. From these floor boxes a f-inch conduit is run to a wall box just above the base board and another to a wall box just above the picture molding. If there is an adjoining office it is provided with similar outlets opposite and connected to the outlets above mentioned. One set of out- lets is placed in each office and in the workroom, money-order and registry room, and swing room; and a floor outlet is located in judge's platform in court room. The entire system is connected with the vault protection system by two 1-inch conduit. CHAPTER VII LIGHTING FIXTURES The present practice of the oiSce is not to include Hghting ixtures in the general contract for the erection and completion of i building but the lighting fixtures for several buildings are grouped and awarded as a separate contract. For the smaller buildings the requirements for lighting fixtures ire standard, and the fixtures are delineated on standard-size jffice drawings, each fixture being given an identifying number. For lighting fixtures for the larger buildings special designs are ised. Full size detail drawings of the most important fixtures are 'urnished manufacturers as the office has found it impossible to ;et satisfactory fixtures by any other means. 3ASIC DATA IN CONTiTECTIGN WITH DESIGN AND INSTALLATION OF LIGHTING FIXTURES As hereinbefore stated all Federal buildings except in the larger !ities are wired for electricity and piped for gas, but combina- .ion fixtures are installed only in the following locations: post- )fEce workroom, post-office screen brackets, and brackets over obby writing desks. Gas only brackets are also installed in up- )er corridors and in basement. All other fixtures are electric )nly. This aUows either gas or electricity to be used in spaces equiring light for extended periods and permits the use of simple iconomical fixture designs in offices, etc., where light is required )nly for short periods. Where combination fixtures are installed, inverted gas-mantle )urners of a special design, developed to match the electric arms ire used on fixtures in post-oflEice workroom and on screen, and up- ight burners (Welsbach Junior) on fixtures in pubhc corridors for ill floors. The inverted mantle-burner arms and the electric arms are al- emately arranged on the body of the fixture. 225 226 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS In court rooms pendant fixtures are made for "electric only" service, and are hung with bottom of glassware about 15 feet 6 inches from floor in rooms with 20 foot ceiling. The usual length of fixtures is 4 feet 6 inches for ceilings more than 20 feet high. In some cases pendants are dispensed with and special cove or ceiling hghts are intalled. Portable desk lamps with an ornamental shade are used on the judge's desk. For the ordinary building, if the lobby desks are free standing and are arranged to receive a lighting fixture, they are equipped with suitable standards. Cord drops are used in boiler, storage, and machinery rooms. In basement they are fitted with porcelain shell sockets; all other sockets have metal husks. Metal reflectors are seldom used on cord drops in basement. In the post-office workrooms special furniture lighting is in- stalled in accordance with standard office details. Metal shades and 15-watt lamps, allowing two lamps for each man, are used for this work. Pendant switches are used for all pendants in the post-ofl5ce workroom and for pendants in office rooms where several fixtures are controlled by one wall switch. Open-flame gas burners on fixtures are never placed closer than 18 inches to a ceiling; and 15 inches is the minimum distance for upright gas mantles. The height for pendants in office rooms will vary from 8 feet 6 inches to about 10 feet, depending upon the size of room and the style of fixtures used; the minimum height being 7 feet. In post- office workrooms and other rooms where more than one outlet is needed the fixture height above the plane of illumination is one- half the distance between outlets for extensive type reflectors and four-fifths the distance for intensive tjq)e reflectors but fixtures are rarely hung over 15 feet above floor. The minimum height where mail bags are handled is 8 feet 6 inches. The architectural features are considered in selecting the de- sign of the lighting fixtures for the first-floor lobby, and their height will vary generally from 10 feet to 16 feet, depending upon the area illuminated and distance between the outlets. In lob- bies having less than a 13-foot ceiling, a ceiling-light globe fixture is generally used. LIGHTING FIXTURES 227 In second and third-floor corridors the usual height for fixtures is 8 feet 6 inches ; in case of a low ceiling they may be hung 7 feet 6 inches above the floor, but no lower. If a basement is less than 9 feet in height, separate gas brackets are used with "electric only" ceiling outlets provided with drop cords; or a ceiling fixture is used if the room is finished. Mailing vestibules with ceiling less than 10 feet require an " elec- tric only" ceiling outlet and a separate gas bracket. Bracket outlets are installed 7 feet above the floor as a general rule. The glassware used is of either the. extensive or intensive types and both prismatic and opal glass is used. Opal dishes are used for semi-indirect lighting. Mirror reflectors and special glass- ware are also used to a limited extent. The reflectors used with inverted gas burners are the same shape and size as those used with electric lamps but are fitted with metal collars to avoid breakage due to the heat of the mantle. As a general rule not more than three sizes of tungsten lamps are used in any one building. Gem and carbon lamps are never used. The specification given at the end of this chapter will give further details of the requirements as to weight of metals, dimensions of glassware, etc. Reflectors are used for all lamps except in the boiler room, store rooms and attic. Finish of fixtures. Light oxidized brass finish is generally used for all fixtures installed in public lobbies, corridors, court rooms, and important office rooms, and oxidized copper is used in all other parts of the building and for maihng platform bracket. Brush brass finish is not used. In the larger and more important buildings special finishes are used to harmonize with the architectural treatment. ESTIMATING THE COST OF LIGHTING FIXTURES For preliminary estimating it is safe to say generally that the lighting fixtures will cost about the same as the conduit and wir- ing system. In Federal buildings a reasonably close approximation of the cost of the fixtures may be made by counting the number of fix- 228 MECHANICAL EQUIPMENT OF FEDEBAL BUILDINGS ture outlets and multiplying by $15 for combination fixtures with Welsbach mantles, by |14 for fixtures with plain gas burners, and by 113.50 for electric-only fixtures. If there is a courtroom the cost of fixtures for same should be determined separately, de- pending on type of fixtures, and be added to the above. The cost of installing fixtures will average for the entire country 10 per cent of the value of the fixtures, though in the South and West 20 per cent will be nearer the figure. Special lighting on post-office workroom furniture costs approxi- mately $10 per light. The following is a typical lighting fixture specification prepared by the office : SPECIFICATION Combination of fixtures. Fixtures are to be of the combination type as designated in the fixture schedule. The fixtures are to be built for the number of electric and gas lamps as shown by sched- ule, regardless of the number shown in the drawings. All com- bination fixtures shall be provided with gas burners of type as indicated by symbol in the schedule, and fixture construction must correspond thereto. The plain lava-tip burners shall be furnished when mantle burners are not specified. "Electric only" fixtures. The construction of this type of fixture is to be the same as that of the combination fixture, with the omission of all gas burners and of all exposed attachments for same. The piping may be used as a passageway for the wiring. "Gas only" fixtures. The construction of this type of fijrture is to be the same as that of the combination fixture with the omis- sion of all electrical parts. Glassware. All fixtures shall be equipped with glassware, free from flaws, and as noted in schedule. The mantle burners shall have glassware harmonizing in design, shape, and finish with the electric glassware on the same fixture, and shall be of size as in- dicated in schedule. Reflectors. The heights of reflectors over all (including collar) shall not be less than the following dimensions : LIGHTING FIXTURES 229 Lamp sizes: heifhfanoLs) 25-watt 41 60-watt 51 100-watt 51 160-watt 65 Reflex No. 3 T burner 5 Reflex No. 4 T burner 41 Type E. Extensive type reflector, designated in schedule as "E," with numeral following to indicate the size of electric lamp in watts with which it is to be used, must give an apparent candle- power at 45° from the vertical axis between 10 and 60 per cent greater than at the vertical axis. Type I. Intensive type reflectors, designated in schedule as "I" with numeral following to indicate either the size of electric lamp in watts or the trade number of the gas burner with which it is to be used, must give an apparent candlepower at 45° from the vertical axis between 10 and 40 per cent less than at the ver- tical axis. All reflectors shall be of an approximate bowl shape, having inside surfaces smooth. The designs or patterns shall not be etched on nor cut in the glass, but shall be pressed or molded in the same, with outlines and elaboration of an artistic but not intricate character. Reflectors shall be made of pure white trans- lucent glass, shall appear white by both transmitted and reflected light, and bear surface patterns coiisisting essentially of panels and ribs; or shall be made of the best quality prismatic glass hav- ing a velvet finish on the inside. Such glass shall have inherent properties allowing a maximum diffusion with total absorption not exceeding 16 per cent. All reflectors shall give a uniform dis- tribution about the vertical axis, and each type shall be uniform as regards dimensions, ornamentation, and distribution curves. All reflectors in this building must be of the same manufacture. Type G. Globes, designated in schedule as "G" with num- eral following to indicate the diameter required are to be of dif- fusing glass of sufficient density to produce uniform brightness over the entire surface and with an absorption not exceeding 25 per cent. The surfaces shall not be cut or roughed in any manner, and are to bear outside surface designs of an artistic but not in- tricate elaboration either pressed or molded in them. Such glass 230 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS shall consist of two hemispheres held together by an equatorial hinged metal band giving access to the lamp, shall have surface patterns consisting essentially of panels and ribs and appear white by both transmitted and reflected light ; or shall consist of a two- piece globe of best quality clear prismatic glass giving efficient downward distribution; the lower piece of prismatic globes shall have a satin finish on the inside. All globes are to be made so that they may be readily secured to and detached from the fix- tures with which they are specified and shall be uniform as re- gards shape and ornamentation. Globes 8 inches in diameter and smaller shall be as above specified except that they may be made in one piece. Type S. Special glassware for bowls and special dishes shall be equal in quality to the globes and have ornamentation sub- stantially as shown on the drawings. Such glass shall in all cases be made of danse opal or white glass and of size as shown on the drawings unless otherwise noted in the schedule. The contractor must replace all glassware installed by him which may be broken or damaged prior to time of final inspec- tion, as all glassware must be complete and free from all defects at time of final inspection. Metals. All exposed parts of fixtures are to be made of brass. The composition of brass shall be approximately 1 part zinc and 2 parts ingot copper. If the contractor desires to use other al- loys in lieu of those herein specified, the composition of the same, together with finished samples of the metals, must first be sub- mitted to the Supervising Architect for approval. Castings. All patterns for casting shall be of metal, hand chased, and perfectly finished. The modeling of patterns must be crisp and spirited, true to detail, and uniform in execution. The castings shall have have ample metal for strength and rigidity and for a substantial appearance. They shall be close grained, free from sand and blowholes, and free from discoloration. All details of cast ornamentation must be plainly brought out by hand finishing. Where ornaments are made in parts, the joints must be brazed and made so as to cause no break in the orna- mentation. Casings, shells, canopies, etc. Casings, spun canopies, and shells up to and including 8 inches diameter shall not be less than LIGHTING FIXTURES 231 No. 20 Brown & Sharpe gauge metal; shells above 8 inches diame- ter shall not be less than No. 18 Brown & Sharpe gauge metal. Both gauges apply to the thickness of metal before spinning, but the thickness of metal after spinning shall not be reduced at any point more than 20 per cent. The size of casing shall in no case be smaller than shown on drawing, and in all cases must be of ample size to provide room for the wiring. All tubing must be seamless drawn, and if used as a supporting member of the fixture must not be less than No. 17 Brown & Sharpe gauge. The cano- pies shall not be insulated from the walls and ceilings. Set-screw collars for canopies shall be at least | inch in thickness, and the collars must fit the stem closely. All curved and bent parts of fixtures shall be true and free from kinks or bruises. All seats between tubings or casings, seating rings, castings, shells, and other parts shall be so closely fitted that all parts will be held tight, forming concealed joints. Canopy rings and seating rings shall be of solid brass turned to size. All burrs, f].ns, and sharp edges must be removed from fixture parts before same are assembled. Gas piping. The gas piping of fixtures shall be: For fixture arms, J inch; fixture stems, f inch; standard galvanized pipe, un- less otherwise shown on drawing. Ends of gas piping to be reamed to the full area of the pipe. All joints must be cemented. Wiring. Fixture wire must be in strict accordance with the latest specifixation of the National Board of Fire Underwriters. The carrying capacity of the wiring shall correspond to the Na- tional Electrical Code requirements. No wire shall be smaller than No. 16 Brown & Sharpe gauge. All joints in wiring must be soldered and well insulated with rubber and friction tape. At all points where abrasion is hable to occur the insulation of the wire must be reinforced with tape or tubing. All wiring must be concealed within the fixture construction, except where chain stems are specified. The exposed wiring of chain-supported fix- tures shall have a silk outer braid of color to match the fixture finish; single wires to be woven in the chain in the most incon- spicuous manner. Sockets shall be wired in multiple. Reflector and globe holders. All reflector holders shall be sup- ported from and rigidly attached to the fixture army or body, shall be made in accordance with the dimensions shown on draw- 232 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS ing, and be provided with a reinforcing ring having a closed joint. Cast holders shall be made as shown and be provided with holes for ventilation. Spun holders for globes shall be made similar to the 2i-inch holders and of such length as to bring lamp filament in center of globe, using electrolier sockets. Switches. Pendent push switches shall be single pole, single point, 5 amperes, 125 volts, National Electrical Code standard. The switches shall have sufficient length of No. 16 Brown & Sharpe gauge silk-covered reinforced lamp cord to bring same within 6 feet 6 inches of floor. Canopy switches shall be National Elec- trical Code standard of the push-and-pull type. Insulating joints. No insulating joints are to be used. Sockets. All metal shell sockets shall be National Electrical Code standard, Edison-base keyless type of either the electrolier or standard size as required, and where not entirely concealed by the glassware holders, shall be finished to match the fixtures. Gas burners. All "gas only" and combination fixtures not pro- vided with mantles shall have 5-foot lava-tip gas burners. Fix- tures denoted in schedule with the s5mibols "3T" are to be equipped with "Welsbach Reflex No. 3 T" burners; fixtures de- noted with the symbol "U 59" are to be equipped with "No. 59 Welsbach Junior" burners. Finish of fixtures. The finish of fixtures is noted in schedule. It must be produced in the most durable manner by electroplat- ing and acid-bath processes. No paints or pigments shall be used to produce any finish. Oxidized copper finish is to be a dark copper color; tone to be even and to be obtained by hand scouring. Light oxidized brass finish shall have the metal highly polished to a yeUow brass color and then oxidized to a dark color before scouring, enough of the dark color being left in the scouring operation to make it scarcely visible on casings, bodies, and other high surfaces, while low portions of both spun and cast orna- ments are to be left dark. All finishes shall have an even coat of lacquer. Upon application of the contractor to the Supervising Architect samples of the various finishes above described will be forwarded to the contractor for his guidance . LIGHTING FIXTURES 233 SCHEDULE OF FIXTURES Mreviations in schedule: 0. C, oxidized copper finisli; L. O. B., light oxi- dized brass finish; 3 T.; reflex No. 3 T. burner; I. 100, intensive type reflector for 100-watt lamp; 1 3 T., intensive reflector for No. 3 T. burner; G., globes, etc. Tungsten lamps used. 1 1 1 3 3 13 2 GAS LAMPS No. Kind 3T. 3T. 3T. 4T. Tip. Tip. Tip. ELECTRIC LAMPS No. Watts 100 25 100 25 100 100 25 100 25 25 25 100 25 25 LOCATION FIRST FLOOR Public lobby Public lobby Postmaster 2 toilets and sink room. Post-ofEce workroom . . . Post-office workroom at sides Post-office workroom screen Money-order and regis- try division Money-order and regis- try screen Mailing vestibule Mailing vestibule In attic BASEMENT Swing room and toilet. Passage, toilet , and over sink Basement generally Gas brackets L. O.B. L. 0. B. L. O.B. L.O.B. O. C. O. C. O. C. 0. C. O. C. O. C. O. C. O. C. O. C. O. C. O. C. O. C. REFLECTOR OR GLOBE TYPE Gas G. 6 in. I. 3T. I. 3T. I. 4T. None •None. None Electric G. 12 in. G. 6 in. S. 20 in. I. 25 I. 100 I. 100 I. 25 I. 100 I. 25 I. 25 None I. 100 I. 25 None z /(. in. 5 3 5 6 2 2 2 Shipment of fixtures. Lighting fixtures shall be wired and sockets connected at the factory when the fixtures are made. They shall not be shipped in a knocked-down condition but shall be assembled in so far as possible to facihtate shipment. Fix- tures having arms must have same connected tight to the body and whenever possible all fixtures shall be shipped assembled and ready to install. Length of fixtures. The length of fixtures given in the schedule is the distance from the ceiling to the bottom of the lowest piece of glass ware (reflector or globe) on the fixture, and where no glass- ware is called for the lowest part of fixture shall determine the length. 234 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS Installation of fixtures. All fixtures shall be hung from the gas piping of the building or from fixture studs. All pendent fixtures shall be plumb and bracket fixtures at right angles to walls. Temporary drop cords. In event of any delay in receipt of sat- isfactory lighting fixtures at the building, or in the event that the lighting fixtures at the building are rejected and it is deemed neces- sary by the superintendent to furnish light to the entire building or any part thereof the contractor must, at his own expense, in- stall such temporary drop cords as the superintendent directs and maintain them in safe and satisfactory condition until satisfactory lighting fixtures are furnished and installed. Inspection and test of fixtures. After the fourth test has been made on the gas-piping system, as specified under head of "Gas piping" in the specification and said test has been certified as satisfactory by the superintendent, the lighting fixtures may be hung and attached to the gas piping when the conditions at the building (as determined by the contractor) warrant. After the fixtures have been connected to the gas piping the entire gas piping and fixtures must be tested and proved tight under an air pressure of 4 inches of mercury. Test pump and mercury-gauge column must be furnished by the contractor. After fixtures are connected to the wiring system of the build- ing the entire wiring system and fixtures must test free from short circuits and grounds and must show an insulation resistance be- tween conductors and between conductors and ground, based on maximum load, not less than the requirements of the latest edi- tion of the National Electrical code, counting full current at 110 volts required with all lamps in service. CHAPTER VIII ELEVATORS WITH SPECIAL REFERENCE TO INSTALLATION IN FEDERAL BUILDINGS UNDER CONTROL OF THE TREASURY DEPARTMENT In deciding upon the number, type, and speed of elevators for modern structures, architects have not been giving the subject the careful prehminary study which its importance demands, and the unfortunate results may be noted in many recently-erected buildings with an elevator equipment that has proved wholly in- adequate. With the aid of individual experience and judgment, a close ap- proximation of the number of elevators which should be installed in a given building may be based on the following facts in regard to elevator service as stated by Mr. R. P. Bolton, a prominent consulting engineer of New York City, in his excellent treatise entitled "Elevator Service." Tenants object to waiting more than thirty seconds for a car, or, in other words, demand a schedule not exceeding thirty seconds. The occupancy of first-class office buildings in large cities will vary from one tenant for 100 square feet of rentable floor area in brokers' offices to one tenant for 150 square feet in office buildings devoted to real estate agents, etc., on the less important streets. In first-class apartment houses it will average one tenant to 300 square feet rentable floor area, and in modern high-class hotels one to 240 square feet. For preliminary calculations for the av- srage office building with mixed tenancy, one tenant to 150 square Feet may be assumed. The rentable area in an average office building is generally 60 per cent of the gross area. The maximum passenger-carrying capacity of an elevator is reached when the car stops at 80 per cent of the number of floors tvhich the elevator is designed to serve. An elevator should be designed on the basis of making 80 per sent of its landings to handle the tenants of the building one way 235 236 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS in one-half hour, if their occupations are of a character which in- dicate that the majority will begin and stop work at about the same time. The average load carried by the elevator is equal to 40 per cent of the number of floors served multiplied by 150 pounds. The speed of local elevators in a modern office building of more than ten stories should be at least 400 feet per minute, and the speed of express elevators should be approximately 600 feet per minute. In estimating the round-trip time of an elevator is has been found that approximately six seconds is required to receive and discharge each passenger : and to this should be added nine seconds for time lost at upper and lower landings in handling gates. The round-trip time of an elevator in a good office building va- ries between IJ and 3 minutes, depending upon height of building, speed of elevator, etc. As a general rule, the time allowed for a round trip should not exceed 2| minutes. With above data, and knowing the gross floor area of a building and the number and height of stories, the elevator equipment and its duty can be determined. Assume a building with a total gross area of 140,000 square feet and a height of 168 feet above the first floor divided into fourteen stories. The rentable area will be about 60 per cent of 130,000 (the area above first floor) or approximately 80,000 square feet. Assuming an occupancy of one tenant to 150 square feet, the number of tenants to be handled by the elevator in one-half hour is 533, or 1066 per hour. There being thirteen landings to be served above the first floor, the mnnber of passengers per trip one way each elevator will be 80 per cent of 13, or say, ten passengers. As each elevator will on an average take ten persons per trip, it is necessary to know the round trip time to arrive at the capacity per hour. Ten pas- sengers will require sixty seconds to enter and leave car, to which must be added nine seconds for time lost at terminal landings, plus actual running time. The speed in this example will be assumed as 400 feet per minute, or an average speed of 5.33 feet per second, making due allowance for retardation, etc. To run 156 feet X 2, or 312 feet, the time will be 312 4- 5.33, or, approximately, 58 seconds; and the total time will be 58 -f ELEVATORS 237 50 + 9 = 127 seconds, which is well within the limit set of 2| ninutes for a round trip. This speed will give approximately ;wenty-eight round-trips per hour and each car will then handle J8 X 10 = 280 persons; and as the total number of persons is L066 per hour, four elevators will be sufficient. The schedule will 3e the round-trip time divided by the number of elevators, or 2 ninutes divided by 4, giving 30 seconds, which is the schedule iesired. The area of the car floor in the example given would be 10 X 2 -|- 4 = 24 square feet, as an allowance of a 2 square feet is made for 5ach passenger and 4 square feet for the operator. The car should 3e close to 6 feet, measured between rails, and 4 feet deep. The iverage number of passengers carried per trip will be 40 per cent Df the number of floors served, or 13 X 0.4, say 5; and assuming ;he weight of each passenger and of the operator as 150 pounds, the result (5 X 150) -|- 150 = 900 pounds, the average load car- ried by the elevator. As a very rough guide in preliminary calculations for Federal ouildings one elevator for 25,000 square feet of floor area may be issumed as satisfactory. Before completing the drawings for a given building it is advisa- ble to take up the elevator problem with some first-class elevator company, as the elevator equipment is a strong factor in the suc- cessful administration of a building, especially an office building. In his treatise, hereinbefore referred to, Mr. Bolton brings 'out certain points about elevator service which are frequently over- ooked by architects and engineers. At least two of these points should be always kept in mind, i.e., that in high buildings the ^levators should be capable of quickly emptying the upper floors n case of a fire; and that in the design of any plant sufficient re- serve capacity should be allowed so that elevator repairs maybe nade during regular working hours without inconvenience to the 3ccupants of the building. The elevators should always be grouped, and occupy a prominent josition in relation to the building entrance. Size of cars. As previously stated, in proportioning the size of ;he platform for passenger elevators for large and tall office build- ngs, it is assumed that a car will stop at 80 per cent of the land- ngs for which the elevator is designed to stop ; that one passenger 238 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS is estimated to be discharged at each of said floors; and that 2 square feet per passenger and 4 square feet for the operator are allowed in determining the minimum size of car. This size should also be nearly the maximum and the final size of the car should not vary much from this determination, for the reason that a large car means more passengers, longer stops, and consequently a schedule slower than that for which the plant was designed. When installing a passenger elevator in an old Federal building where no hatchway was originally provided, the minimum size of car is made 4 feet 6 inches x 4 feet 6 inches. This is an unde- sirable size and is used only where the conditions demand it. In old buildings where conditions permit and in all new build- ings, the cars are made 6 feet wide measured between the rails, and 5 feet deep. A wide and shallow car is much more desirable than a square car, or a car with a great depth and a narrow di- mension between rails, as passengers have a tendency to crowd to the front of a car. No car should be larger than 6 feet x 6 feet except in a department store, where an 8 feet x 6 feet deep car should be the maximum. The use of pilasters in cars is not desirable and should be dis- couraged. In Federal buildings the cars for freight elevators, mail Ufts, and bonded wareroom hfts are made 6 feet x 6 feet, which is the most desirable size. Ash-lifts and hand-power mail-lifts are gen- erally made 4 feet x 4 feet, and cars for electric dumb-waiters 3 feet 4 inches x 3 feet 4 inches. Elevator hoistways are made 1 foot 1 inch wider than car to allow for the guide rails and 9 inches to 12 inches deeper than car, the front of car being kept 1| inches away from the entrance threshold. In office buildings up to 10 stories the car should be 5 feet wide measured between the rails and 4 feet 4 inches deep. From 10 to 15 stories the cars should be approximately 6 feet wide and 4 feet 4 inches deep; and from 15 to 19 stories, if all elevators are local, the cars should be approximately 6 feet 6 inches wide and 5 feet deep. In the average first-class office building, or in a Federal building, the cost of the ornamental car should range between $300 and $500. Any increase over $500 is extravagant, as, for instance, in install- ELEVATORS 239 ing special, solid bronze cars. The electroplating of iron is just as satisfactory and much cheaper. Emergency exits should always be specified for passenger cars. If cars are in a separate hatchway, the emergency exit should be in top of car, and where two or more cars are in the same hatch- way, emergency exits should be provided from one car to another. A car with two entrances is dangerous and objectionable. When conditions demand two opposite entrances, a collapsible gate or sliding panel in the car should be used at the entrance further from the operator; and entrance door and gate on car should be operated by an approved device, which on electric ele- vators should be made interlocking with the controller. If the entrances to the car are on adjacent sides, the entrance gate further removed from the operator should be protected by some device, which, on electric elevators, should be interlocking with the con- troller. Speeds. The determination of the speed at which a car should be operated is a matter of judgment, and is governed by the rise of the elevator, whether the service is express or local, the number of stops, and the time taken to discharge passengers. In apartment houses the car speed under ordinary conditions should be not over 200 feet per minute. In departnent stores the speed should not exceed 250 feet per minute nor should it fall much below that where cars stop at each landing up and down. In hotels higher speeds should be used, depending on the height of building. In office buildings below 10 stories in height, the speeds will vary from 200 to 400 feet, while with 10 to 15 stories a speed of 400 feet should be allowed. Express elevators equal in number to the local elevators should be used in practically all buildings sixteen stories high and over, and in very tall buildings may be run at 700 feet to 800 feet per minute until they reach their first landing. In very tall buildings where the ground area is small it is better to run all elevators local rather than to have part local and part express. In New York City 500 feet per minute is the legal limit of speed for local elevators and 700 feet per minute for express service. An eleva- tor is rated as "express" when it has a clear run of 80 feet with- out a stop. 240 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS Federal buildings are nearly always low, and consequently ele- vator speeds are comparatively low. The following are used : Speed in feet Travel of car per minute [30 to 40 feet 200 Passenger Elevators ee whether the voltage fluctuates badly, and, if so, be careful to Jlow for it in calculations. See that the elevator accelerates in 5 seconds in making thii ibove test. After test, adjust the controller so that the car will accelerate in 3 seconds if this quicker acceleration does not give a )oor start. After capacity test reduce load gradually until the current re- (uired to run car up is same as that required to come down, in- licating a balanced condition of car, and note the balancing load n reporting on results. Instruct custodian to take up the matter of the supply of oil or operating the elevator with the office. Be sure that the man who will be in charge of the elevator is ally instructed as to oiling machinery; the proper oil to be placed a gear case; use of lubricant on cables; care of commutator and ontroUer and care and oiling of guide rails. It must be borne in mind that technical ability of the man in harge of the elevator, and the care and skill of the elevator con- !uctor, are the most important factors of safety in connection nth the operation of the machine. CHAPTER IX SMALL POWER PLANTS WITH SPECIAL REFERENCE TO INSTALLATION IN FEDERAL BUILDINGS UNDER CONTROL OF THE TREASURY DEPARTMENT In determining whether the mechanical equipment of a Federal building should include a power plant for generation of elec- tric current for light and power, the following items require consideration: The cost; of current if supplied by local electric companies. First cost. Whether suitable space is available. Difference in cost of salaries for power plant operation as com- pared with salaries in connection with operation of a low-pressure heating system. Increase in total cost of fuel required for the power plant above that required for a low-pressure heating system. Increase in cost of water used on account of exhaust steam wasted to the atmosphere. Interest charge on first cost. Depreciation charge (amortization). (Interest and depreciation are assumed as 8 per cent of the first cost of the plant.) In arriving at the cost of the plant the following figures are used: Single-valve direct-connected simple engines and genera- tors, per kilowatt, in place $35 .00 Single-valve direct-connected compound engines and gen- erators, per kilowatt, in place 45.00 Four-valve direct-connected simple engines and generators per kilowatt, in place • 46 .00 Four-valve direct-connected compound engines and gen- erators, per kilowatt, in place 55 .00 Water-tube boilers and setting, with breeching and stack, per horse power, in place 30 .00 Switchboard and mountings, per panel, in place 300.00 Piping, pumps, feed-water heater, etc., in place, at 20 per cent of the cost of the boilers, engines, and generators. . 278 SMALL POWER PLANTS 279 The estimated cost of labor for operation is generally the most important factor in determining whether a plant shall be in- stalled. For operation of the average small plant in a Federal building the following force will usually be found sufficient: One chief engineer, at $1600 per annum. Three assistant engineers, at $1200 per annum. One engineer's helper, at $1000 per annum. Three firemen, at $2.50 per day. Two coal passers, at $2.00 per day. One fireman helper at $2.25 per day. In the same building with no electric generating plant and with electric elevators the following force will usually be found sufficient : One chief engineer, at $1400 per annum. Two assistant engineers, at $1000 per annum. Three firemen, at $2.25 per day, for seven months in the year. One fireman helper, at $2.00 per day for twelve months in the year. Two coal passers, at $2.00 per day for seven months in the year. To approximate the amount of coal required to heat the build- ing, ascertain the amount of radiation, both direct and indirect, reducing the latter to the equivalent of direct radiation by mul- tiplying it by 3 if a fan is used with the system, or by 1| if the cir- culation of air is by natural means. Assimie that each square foot of direct radiation or its equivalent will condense 500 pounds of steam in a season of 200 days, and that when boilers are oper- ated for heating only there will be evaporated 7 pounds of water per pound of coal. If only the cubic contents of the building are known, a fair average for buildings in the latitude of New York City will be 1 square foot of radiation per 100 cubic feet of the contents. To approximate the additional amount of coal required to operate a generating plant, ascertain the size of the generating units as hereinafter described, and assume that the large utiit svill operate under a fluctuating load varying from | to 1| load 16 hours a day for 165 days, and that the small unit will operate under the conditions noted above 8 hours a day. The steam 3onsumption per indicated horse-power of the engines under the rarying loads is taken from the tables hereinafter given, and the 280 MECHANICAL EQUIPMENT OF FEDEEAL BUILDINGS total steam consumption in pounds for the two units is reduced to pounds of coal on the assumption that 8 pounds of water will be evaporated per pound of good bituminous coal. General arrangement of the apparatus. In connection with electric generating plants in Federal buildings, all-steel water tube boilers are installed, if possible, and are designed for a safe work- ing pressure of 150 pounds per square inch, the usual operating pressure being 125 pounds per square inch. The size of the boiler plant is generally governed by the heating and ventilating requirements, as same are heavier in practically all parts of the country than are the requirements of power for operating the engines. A close approximation of the boiler re- quirements for direct heating is made by allowing one boiler horse-power for each 7000 cubic feet of conteiits of the building. In event the heating and ventilating requirements and space conditions are n&t the governing factors in determining the num- ber and size of the boilers, the day load and evening load on the generating plant are determined by the method hereinafter de- scribed; and the day load plus the evening load divided by 2 will give the size of the boiler units from which the best results will be obtained, one boiler being sufficient to carry the full load, with some margin, on the daylight run, and the evening load by slightly forcing the fires. This can easily be done by cleaning the fires toward the end of the daylight run and working up a strong deep fire for the commencement of the evening load. Three boilers of the size above noted would generally be installed. The minimum size of water-tuber boiler installed is 100 H.P. The clear heights which must be allowed from bottom of pit to underside of ceiling beams to insure a proper installation for the water-tube boilers used by the office are as follows: For boilers of 100 to 150 H.P 14 6 For boilers of ISO to 175 H.P 15 For boilers of 175 to 200 H.P 15 6 These boilers are based on 10 square feet of water heating sur- faces per horse-power, and are always equipped with some kind of smoke-preventing apparatus. The boilers are arranged, when possible, to give a short, direct SMALL POWER PLANTS 281 connection to the stack, and are so located as to be close to the sngine room and convenient to the coal and ash rooms. A firing pit (especially a deep one) is always a detriment and is avoided if possible. The boiler and engine rooms are ventilated by drawing the hot air away from the ceiling by a fan or by fans, and allowing the sold air to flow in by gravity through doors and windows so arranged that firemen will not be subjected to a cold draft. The location of the engine room either directly in front or di- rectly at the rear of the boiler room gives the shortest pipe con- aections, and hence the least friction and condensation in the steam mains. This arrangement of engine and boiler rooms also allows for increase in the boiler, engine, and switchboard capacity by lateral 3xtension, giving at all times a neat and compact arrangement of apparatus, and one which is economical both in first cost and in Dperation. Arranging the engines with cylinders on center lines parallel svith center lines of boilers, and close to partition between boiler and engine room (5 to 10 feet clearance between wall and cylinder bead) further shortens steam and exhaust connections. Size and munber of generating units. The full connected lighting and power load is ascertained, special attention being ^iven to accurate determination of the rated horse-power of all jlevator motors, as this item has an important part in determining }he size of the units. The starting current of elevators is never ess than 35 per cent in excess of the maximum running current mth. direct-current motors, and rises to 200 per cent with alter- lating-current motors. Federal buildings in which generating plants are installed are ill 24-hour buildings, and no breakdown connection is made vith the local lighting companies; therefore the plants are made arger than in commercial practice, and never less than three units ire installed; generally two large units, each sufficient to carry he peak load, and one small unit to carry the after-midnight oad. Usually, with a view to insuring as far as practicable continuous )peration, a four-unit plant is selected, comprising two large units', lach able to carry the peak load, and two small units, each capable if carrying the after-midnight load. 282 MECHANICAL EQUIPMENT OP PEDEBAL BUILDINGS No unit smaller than 75 kilowatts, and generally none larger than 150 kilowatts is installed. The reason for not using a unit smaller than 75 kilowatts where an intermittent power load pre- vails needs no explanation, while space conditions, etc., gener- ally forbid the installation of units exceeding 150 kilowatts. To determine accurately the proper number and size of units within the limits stated, further analysis is made, as follows : Constant load, consisting of. Intermittent load, consisting of . . . a percentage of the total number of lights connected. ■ a constant power load consisting of certain motors likely to be run con- tinuously. electric elevators, motors for mail lift, ventilating fans, house pump air compressors, circulating pumps (if used), vacuum cleaning machine, automatic temperature-control ap- paratus, air washer-motors. In determining the size of the units, the power demand should be analyzed under "day load" and "night load" conditions. With the post office operating all night the heaviest demand for current will be between the hours of 4 p.m. and 10 p.m., while from 11 p.m. to 6 a.m. the demand will be the smallest. The day load will consist of a small lighting load plus a con- stant power load plus an intermittent power load, all of which may be determined approximately, as follows: Day load. Lighting. Power. . . 30 per cent of basement lights. 20 per cent of post-office workroom lights. 10 per cent of first-floor corridor lights. 5 per cent of office lights on all floors. f ventilating fan motors. Constant < circulating pump motor for air [ washer. electric elevators, house pump. Intermittent, ... i mail hoist motor, air compressor, vacuum cleaning motor, etc. fter-midnight load • SMALL POWER PLANTS 283 The constant power load can be accurately determined, as it lould not be difficult to decide definitely what ventilating fans, ump motors, etc., will be operated more or less continuously. After the day-load conditions have been thoroughly investi- ited the load conditions of the evening and after-midnight runs lould be determined, as follows: f70 per cent of all post-office workroom lights. I 30 per cent of all basement lights. vening load j 60 per cent of first floor corridor lights. I small power load for fan, pump, or similar [ service, determined from the plans. 40 per cent of all post-office workroom lights. 30 per cent of all basement lights. 30 per cent of all first-floor corridor lights, small power load to be determined from the plans. If the day load plus the after-midnight load is equal to or greater lan the maximum or evening load, one unit should be selected ith full-load rating equal to the day load, and one unit with lU-load rating equal to the after-midnight load. These two aits can then be operated in parallel to carry the maximum or ;rening load. The capacity of the spare unit is made equal to the day load. If, however, the maximum load is greater than the sum of the ly and after-midnight loads, the size of the smaller unit must be lual to the difference between the day load and the maximum or rening load. As hereinafter stated, the large units must never be less in ipacity than four times the rated kilowatt capacity of all ele- itor motors which may be in use at one time. When the day load is larger than 150 kilowatt, two or more lits, preferably of equal capacity, are chosen. To illustrate the method of proportioning units: Assume that the constant light and power day load is 110 kilo- atts, and that two electric elevators are intermittently in use, Lch having a motor rated at 10 kilowatts, and each motor re- liring 15 kilowatts to start. The maximum instantaneous load )ssible under the conditions is 110 plus 15 plus 15, or a total of to kilowatts. 284 MECHANICAL EQUIPMENT OF PEDERA.L BUILDINGS A 125-kilowatt unit would be selected for this case, as said machine has an overload capacity of 156 kilowatts for two hours. The generator could easily take care of a vacuum-cleaner or other small motor in addition to the load stated. For another example; assume that the constant light and power day load is 50 kilowatts, and that there are two electric elevators in service, each having a motor rated at 10 kilowatts and requiring a starting current of 15 kilowatts for each motor, or a total of 30 kilowatts intermittent load. A 75-kilowatt gen- erator would be selected for this service. In selecting the size of a generating unit which must carry the constant power and light day load and also an elevator load, the size of the generator should never be less than four times the rated kilowatts of all the electric elevators which may be in use. The relation of the generator capacity to the intermittent elevator load must not be overlooked or the voltage regulation will be poor and the lights will blink when the elevators start. In commercial practice the generator capacity is, under adverse conditions, sometimes made only 21 times the rated kilowatt capacity of the elevator motors, but the results are bad. The foregoing methods of determining the generating unit capacity are for buildings where the larger unit will not exceed 150 kilowatts. When conditions arise which require the design of a plant involving much larger capacities, and where perhaps from four to ten elevators are in daily use, it is advantageous to provide and operate two units in parallel for the day load in lieu of one; or one large one and three of one-half its capacity sometimes will prove a better arrangement, depending on the rela- tive proportion of the constant and intermittent loads, etc. No hard and fast lines can be laid down to govern the size of generating units, but the procedure is substantially as stated. TYPE OF ENGINES By reason of the advancement in steam engineering in recent years, a number of types of steam engines suitable for operating electric generators are available, each type possessing some merit peculiar to itself which adapts it to fill to best advantage certain operating conditions. The simple and compound high-speed single-valve, and simple SMALL POWER PLANTS 285 id compound medium-speed Corliss-valve engines are the prin- pal types offered. These engines are inclosed, self-oihng, and juipped with automatic shaft governor. They are built either jrizontal or vertical and are arranged for direct connection to 1 electric generator. No arbitrary rules can be laid down to determine the choice ■ the proper type of engine, and each particular installation re- iiires individual consideration. Floor space, size of unit, cost ■ coal, characteristics of load, steam pressures, building heating squirements, and initial cost of installation are the principal ictors which govern such selection. Simple single-valve engine. This type has the fewest me- lanical parts of any of the types mentioned, which commends in all cases where a minimum of attention is desired and at- sndants of only average ability are employed. It is also the ast expensive, which further commends it where first cost is a ictor. On the ground of relatively smaller investment and spreciation, it is usually selected for small units ranging up to id including 50 kilowatts capacity, as in these sizes the saving ? other types in steam does not offset the fixed charges. This ^pe is also recommended in somewhat larger sizes where coal not expensive (say |2 or less per ton), and for installations here the unit is in service for but short periods. It is also well iapted for use in buildings which must be heated during a large irt of the year, or where the demand for steam heating exceeds L amount the engine exhaust. The speeds of this type of engine range as follows : ize kilowatt Revolutions per capacitv minute 25 300-450 35 300-350 50 275-325 75 250-325 100 250-300 125 225-275 150 200-260 200 150-225 250 150-220 300 150-200 The steam consumption per indicated horse-power per hour for 1 the different sizes given above should not exceed the following 286 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS amounts when operating with atmospheric exhaust and at the initial steam pressures stated: I. s. p. QUARTER LOAD HALF LOAD THEEE- QUAHTER LOAD PULL LOAD pounds pounds pounds pounds 48.9 37.8 34.3 33.8 44.0 35.4 32.4 32.0 40.5 33.4 30.9 30.6 37.6 31.7 29.6 29.2 35.3 30.2 28.5 28.1 33.9 29.0 27.6 27.2 32.5 28.1 26.2 26.3 31.6 27.1 25.8 25.6 ONE AND ONE- QUARTER LOAD pounds 80 90 100 110 120 130 140 150. pounds 34.3 32.5 31.1 29.7 28.4 27.7 26.9 26.1 The mechanical efficiency of engines of this type is usually not less than 95 per cent for engines under 300 H.P. capacity and 94 per cent for larger sizes. Simple Corliss-valve engine. This type is a development of the releasing Corliss-valve gear engine and partakes of its character- istics so far as steam consumption is concerned. By reason of fewer parts, without auxiliary cut-offs, dash-pots, etc., more ad- vantageous regulation and speeds are obtainable, making it ad- mirably suited for installation in Federal buildings, where the available floor space is usually limited. It is recommended for units 75 kilowatts in capacity and above, for localities where coal costs over $2 per ton, and with steam pressures in general use which range from 110 to 125 pounds. The steam consumption curve of engines of this type is very flat throughout its range, which adapts it for installations, with fluctuating loads. This, combined with the high mechanical efficiency, commends this type for the usual Federal building installation. The usual speeds of Corliss-valve engines are about as follows: Size kilowatt Revolutions per capacity minute 75 225-250 100 225-250 125 200-225 150 200-225 200 150-200 250 150-200 300 150-200 SMALL POWER PLANTS 287 Steam per indicated horse-power per hour required by engines this type when operating at the initial steam pressures stated d with atmospheric exhaust should not exceed the following lounts for any of the sizes above noted : I.S.P. QUARTER LOAD HALU LOAD THREE- QUARTEK LOAD FULL LOAD ONE AND ONE- QUARTER LOAD pounds pounds 40.0 37.0 34.8 33.3 32.4 31.8 31.2 30.4 pounds 29.6 27.8 26.4 25.3 24.5 24.0 23.6 23.1 pounds 27 A 26.1 24.8 23.8 23.1 22.6 22.2 21.8 pounds 27.5 26.4 25.3 24.3 23.6 23.0 22.6 22.3 pounds 28.8 27.5 26.4 25.3 24.7 24.2 23.8 23.5 The mechanical efficiency of simple Corliss-valve engines is ually not less than 94 per cent for engines under 300 H.P. and per cent for larger sizes. Compound single-valve engine. This engine is adapted for stallations having comparatively high steam pressures ranging )wards from 120 pounds with no back pressure, or operating ndensing. As shown by the table of steam consumption fol- iving, compound engines are not economical at light loads, and erefore constant approximate full loads are necessary for best suits. The speeds of this type which are built either tandem or cross- mpound, are about the same as given for the simple single-valve gines. The steam consumption per indicated horse-power per hour r engines ranging from 75 to 300 kilowatts should not exceed the lounts given in the following table when operating at the initial 3am pressures given and with atmospheric exhaust. The amounts given in the following table are bettered approxi- itely 15 per cent for the quarter and half loads and 20 per cent c the other loads when operating condensing with about 24 3hes of vacutun; the amount of steam required for the con- nser, when condensing water is available, will average 7 per at of the steam used by the engine, leaving a net gain of about 288 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS I. s. p. QUARTER LOAD HALF LOAD THREE- QUARTER LOAD PULL LOAD ONE AND ONE- QUARTER LOAD pounds 100 110 120 130 pounds 48.6 44.6 42.4 41.3 40.3 39,4 38.7 38.3 pounds 32.9 29.5 28.2 27.6 27.0 26.5 26.0 25.6 pounds 28.2 25.4 24.3 23.7 23.2 22.7 22.2 21.8 pounds 27.5 24.6 23.5 23.0 22.5 22.0 21.5 21.1 pounds 28.0 25.0 24.0 23 A 140 ISO 22.9 22.4 160 170 21.9 21.6 8 per cent for light loads and 13 per cent for heavier loads when operating condensing instead of with atmospheric exhaust. For engines of this type of less than 300 H.P. capacity, the mechanical efEciencj'' is about 93 per cent, and in larger sizes about 92 per cent. Compound Corliss-valve engine. This type of engine is recom- mended where proper operating conditions prevail and extreme economy is desired. These conditions are steam pressures of 120 pounds or higher, comparatively steady full load, and exhausting with little or no back pressure, or operating condensing. The speeds at which engines of this type operate are about the same as given for simple Corliss-valve engines. The engines of this type ranging in size from 75 to 300 kilo- watts, when operating at the initial steam pressures given and with atmospheric exhaust, should not consume at varying loads more than the amounts per indicated horse-power per hour following: I. S.P. QUARTER LOAD HALF LOAD THREE- QUAHTER LOAD FULL LOAD ONE AND ONE- QUARTER LOAD pounds 100 pounds 47.0 43.4 41.2 39.6 39.0 38.5 38.0 37.6 pounds 32.3 30.0 28.0 26.8 26.4 26.0 25.5 25.0 pounds 26.7 24.3 22.5 21.3 20.9 20.5 20.1 19.8 pounds 25.2 22.6 21.1 19.8 19.4 19.0 18.7 18.4 pounds 24.9 no 120 22.7 21.3 130 20.3 140 19;9 150 19.5 160 19.1 170 18.8 SMALL POWER PLANTS 289 The amounts given in the table above are improved about the le percentage when operating condensing as given under com- md single-valve engines preceding. The mechanical efficiency of compound Corliss-valve engines of 3 than 300 H.P. capacity is usually not less than 92 per cent, i for larger sizes 91 per cent. selecting an engine. To show the utility of the foregoing data, I following example is given for determining the proper engine be selected «nder assumed conditions of operation : Che engine is to be required to drive a 100-kilowatt generator h 110 pounds initial steajn pressure, exhausting at atmospheric ssure; loads ranging between one-half and one and one-quarter [ loads; units operating ten hours per day, 300 days per year, h coal costing $3.50 per ton. A^'ith a simple single-valve type the steam consumption for •ying loads taken from the table is as follows : ONE-HALF LOAD THREE- QUARTER LOAD FULL LOAD ONE AND ONE- QUARTER LOAD am consumption per I. H.P. er hour . . . . pounds 31.7 pounds 29.6 pounds 29.2 pounds 29.7 The steam required per hour at varying loads would be as ows: i-half load-31.7 1bs. X 75 I.H.P. •ee-quarter load-29.6 lbs. X 112.5 I.H.P. 1 load-29.2 1bs. X 150 I.H.P. ! and one-quarter Ioad-29. 7 lbs. X 187.5 I.H.P. = 2,375 lbs. = 3,340 lbs. = 4,370 lbs. = 5,575 lbs. 4)15,660 lbs. verage steam per hour 3,'915 lbs. X 3,000 rs = 11,745,000 lbs., the total steam required for the engine per year. Vith the simple Corliss-valve engine operating the same as ive, with steam consumption taken from the table, steam re- red per hour would be in accordance with the following : 290 MECHANICAL EQUIPMENT OF FEDEBAL BUILDINGS ONE-HALF LOAD THREE- QUARTER LOAD FULL LOAD ONE AND ONE- QUARTER LOAD Steam consumption per I.H.P. per hour pounds 25.3 pounds 23.8 T'Ounds 24.3 pounds 25.3 One-half load-25.3 lbs. X 75 I.H.P. = 1,900 lbs. Three-quarter load-23.8 lbs. X 112.5 I.H.P. = 2,680 lbs. Full load-24.3 lbs. X 150 I.H.P. = 3,650 lbs. One and one-quarter load-25.3 lbs. X 187.5 I.H.P. = 4,810 lbs. 4)18,040 lbs. Average steam per hour 3,260 lbs. X 3,000 hours per year = 9,780,000 lbs, yearly steam consumption. A compound single-valve engine operating under the same conditions will for varying loads require the following amounts of steam : ONE-HALF LOAD THREE- QUARTER LOAD FULL LOAD ONE AND ONE- QUARTER LOAD Steam consumption per I.H.P. per hour ■pounds 29.5 pounds 25 A pounds 24.6 pounds 25.0 One-half load-29.5 lbs. X 75 I.H.P. = 2,210 lbs. Three-quarter load-25.4 lbs. X 112.5 I.H.P. = 2,860 lbs. Full load-24.6 lbs. X 150 I.H.P. = 3,680 lbs. One and one-quarter load— 25.0 lbs. X 187.5 I.H.P. = 4,730 lbs. 4)13,480 lbs. Average steam per hour 3,370 lbs. X 3,000 hours = 10,110,000 lbs. steam per year. With a compound Corliss-valve engine the steam required at varying loads will be as follows: Steam consumption per I.H.P. per hour ONE-HALF LOAD ■pounds 30.0 THREE- QUARTER LOAD pounds 24.3 FULL LOAD pounds 22.6 ONE AND ONE- QUARTER LOAD pounds 22.7 SMALL POWER PLANTS 291 le-half load-30.0 1bs. X 75 I.H.P. = 2,260 lbs. iree-quarter load-24.3 lbs. X 112.6 I.H.P. = 2,740 lbs. ill load-22.6 1bs. X 150 I.H.P. = 3,380 lbs. le and one-quarter load-22.7 lbs. X 187.5 I.H.P. = 4,290 lbs. 4)12,660 lbs . Average steam per hour 3,165 lbs. X 3,000 urs = 9,495,000 lbs. yearly steam consumption. Comparing the performance of the simple single-valve engine ith the simple Corliss-valve engine, there will be the difference stween 11,745,000 pounds steam and 9,780,000 pounds, or 965,000 pounds steam less required for the simple Corliss-valve an for the simple single-valve engine. Reducing this saving steam to coal at 8 pounds evaporation, there is a total saving 245,625 pounds of coal, or about 109 tons of 2240 pounds each, bis saving in coal at $3.50 a ton amounts to approximately )81.00 per annum, which would justify the difference in the nount of investment in the two engines, roughly about $1200 While the compound single-valve engine shows a gain over the uple single-valve engine, it is obviously insufficient to weigh ;ainst the selection of the simple Corliss-valve type; and as the impound Corliss-valve engine, in comparison with the simple 3rliss-valve type, does not show enough gain to warrant selec- 3n at its greatly increased price, it may be concluded that the nple Corliss-valve engine would be the proper one to choose ider the assumed conditions. If the coal in the above example had been purchased for $1.50 sr ton, the yearly saving with the simple Corliss-valve engine '•er the simple single-valve engine would have been only $163.00, I amount insufficient to justify the expenditure of the additional m necessary to purchase the simple Corliss-valve engine. The engine efficiencies have been ignored in the above calcula- 3ns, as the only object was to show the use of the tables and the ethod of calculating the steam required per indicated horse- )wer with different type machines. ELECTRIC GENERATORS The usual load consists of elevators, lighting, ventilating fans, id pimips, the elevator load being the major part of the total 292 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS load. It is therefore desirable to use a generator of such char- acteristics that a fairly constant lighting voltage will be main- tained when the elevators are thrown on the circuit, and frequent overloads will be carried without sparking. These characteristics are best obtained in the interpole design. In a non-interpole generator, sparking is due primarily to a local magnetic field surrounding a coil which is being commutated. This field sets up a counter-electromotive force, or voltage, in the commutated coil in such a way as to oppose the reversal of the current in the coil, and thus tends to cause spark as the coil or commutator bar leaves the brush. This action increases with current or load, and is especially destructive at heavy overloads. In a non-interpole machine, sparkless commutation may be ob- tained if the brushes can be so located that the armature coils, short circuited by them, are brought into a magnetic field of exactly the right direction and strength to neutralize the effect of the local field at the moment of commutation. Such a field is found to exist near the tips of the pole pieces, and it has been customary to advance the generator brushes sufficiently to bring the armature coils within its during commuta- tion; but this field varies in strength under various conditions of loads, and instead of becoming stronger as desired with increase of loads, it actually becomes weaker. Interpole generators. In interpole generators the proper con- ditions for commutation are obtained by the use of small poles interspaced between the main poles. The interpoles have their windings in series with the armature and set up magnetic fields which annul the effect of the fields formed by armature magnetization, and generate in the commu- tated coils an electromotive force which assists the reversal of the current. Since the interpole coils are in series with the armature, the interpole field strength varies in proportion to the load, and it thus has the proper corrective effect at all loads. Since the electromotive force due to the interpole which assists reversal has a definite position under the interpole, the coil being reversed must also be located accurately with respect to this re- versing electromotive force. The brushes are consequently lo- cated on the true neutral point, arid experience proves that spark- SMALL POWER PLANTS 293 ss commutation can be obtained under practically all conditions om no-load to very heavy overloads. Commercial kilowatt and speed ratings of direct-current jnerators. Standard commercial speeds and kilowatt capacities om 25 kilowatts to 300 kilowatts for 125-volt, 250-volt, and 25-250-volt 3-wire generators are as follows for interpole lachinery : Kilowatt R.P.M. 25 295-305-310-325 35 285-305-315 50 275-280-290-300 75 250-265-275-290 100 250-260-275 125 225-250-260-275 150 200-220-250-260-275 200 100-150-200-210-220 250 150-200-220 300 10D-120-15O-200-220 Late designs are provided with steel frames to produce rugged id stiff construction and at the same time to reduce the handling id shipping weights and permit light foundations. Ventilation. The later types of machines have open-end wind- Lgs on the armatures as well as air ducts in the armature cores, he shunt field coils are form-wound in comparatively long coils ■ small radial depth. The series and interpole coils are wound om bare copper strap insulated with spacers, with ample air icts between the poles, shunt coils, and series coils, so that the ■mature and field windings of the generator are open to free jntilation. Temperature rise and overloads. Based on a room temperature ■ 25° C, the temperature rise at full load should not exceed 35° C. 'ter continuous operation, nor 50° C. after two hours' operation at ) per cent overload. A small margin should be allowed, say 5° C, 1 the commutators of 125-volt generators. SPECIFICATIONS The following is a specification for engines and generators as ■epared in the office of the Supervising Architect : 294 MECHANICAL EQUIPMENT OP FEDERAL BUILDINGS ENGINES Type. The engines are to be of the single-cylinder, automatic, horizontal, side-crank type with gravity feed lubrication, and are to be designed to operate non-condensing on dry saturated steam at 110 pounds gauge pressure at the throttle; the speed of the 100- kilowatt generator engine to be between 225 and 250 revolutions per minute, and that of the 50-kilowatt generator engine to be between 275 and 300 revolutions per minute. Capacities. The engines are to be designed so as to operate most economically when generators are delivering three-quarter load at the rated voltage and speed, and shall be capable of oper- ating the generators for two hours when delivering 25 per cent overload at rated voltage. Foundations. Foundations to be of the required form to suit engine and generator sub-bases, and to be constructed of 1:2:3 concrete with the bottom not less than 4 feet below the floor line. The top must extend not less than 6 inches beyond the edge of sub-base frames all around, and the batter in the depth specified must be not less than 3| feet each side. Concrete foundations to be provided with cushion of 6-inch deep sand. Foundation bolts to be provided with washers and wrought-iron sleeves. Sub-bases. Each engine to be provided with a heavy and sub- stantial cast-iron sub-base upon which shall be mounted the engine; the sub-base of the 100-kilowatt generator engine to be extended under cylinder for support of cyhnder. The sub-base of generators must be secured to engine sub-base with suitable bolts and dowels, and both sub-bases secured to the foundations. Frames. Each engine to be provided with a heavy aad substan- tial cast-iron frame designed for strength, rigidity, and compact- ness, and to be provided with suitable covers to prevent throwing oil and allowing dust to come in contact with the moving parts. Bearings. Each engine to have two bearings; one to be set in the engine frame and the other to be outboard beyond the genera- tor. Bearings shall be long, well-proportioned, and dust proof. The out-board bearing to be of the oil ring type. Bearings to be lined with genuine babbitt metal carefully peened in place and accurately bored to gauge. The bearings to be provided with SMALL POWER PLANTS 295 large size oil wells, visual gauges, and petcocks for drawing the oil. Bearings to be provided with means for adjustment. Lubricating system. Each engine to be provided with an automatic self-lubricating system which shall supply pure, clean oil continuously to all bearings, etc., the operation of system to be positive and free from throwing or spilling the oil, and arranged to reuse the oil. Cylinders. Each cylinder to be made of best grade of close- grained cast iron, bored true and smooth, and of sufficient thick- ness to allow for reboring. The cylinder to be well lagged with magnesia or other material having equal heat insulating value, and covered with ornamental cast-iron jackets or with Russia iron, properly secured to the cylinder casting. Pistons. The piston heads shall be hollow cast iron, with at least two snap rings with lap joints, made from first quality of hard, close grain cast-iron sprung into accurately fitting grooves. Rings shall override the bore of cyhnder. Piston rods to be best quality nickel steel. Rods to be turned to a taper at the piston ends and each driven up to a shoulder and securely held by a heavy nut to be drilled and provided with cotter pin. The for- ward ends to be screwed into crossheads and provided with jam nut to prevent turning. Crossheads. The crossheads to be made of cast iron or steel and be provided with adjustable bronze shoes circular in form. Crosshead pin to be made of steel hardened and ground and held in place by taper fit and nut. Connecting rods. The connecting rods to be forged open- hearth steel in one piece with solid end and crosshead end. The crosshead boxes to be made of phosphor-bronze adjustable by means of wedge. Crank ends to be fitted with boxes of steel lined with genuine babbitt metal peened and bored to fit the pins. Crank shafts. Crank shafts to be constructed of open-hearth steel forged in one piece, with counterbalanciag crank disks of annealed steel, securely fastened thereon. Valves. The valve for the 50-kilowatt generator engine to be perfectly balanced, of the adjustable type, constructed of best quality hard close-grain cast iron, operated in removable bushings or pressure plates. The 100-kilowatt generator engine to be fitted with four valves 296 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS of the semirotary or gridiron type, designed to be slightly un- balanced and securing positive steam-tight seating over the ad- mission ports. Steam valves to be of the multiported type giving ample port openings for all points ot cut-off. Exhaust valves to be designed to give ample port area and insure tightness. All valves to be constructed of best quality hard close-grain cast iron. Semirotary steam valves to be provided with removable bushings or cages; gridiron valves to be provided with suitable balancing plate. Valve mechanism. The valve mechanism on each engine to be designed to give quick and positive motion to the valves in open- ing and closing. All pins subject to wear to be made of steel hardened and ground. All boxes for pins to be made of phosphor- bronze and be adjustable without filing. Lubrication of pins and bearings to be accomplished while in motion by compression grease cups placed at accessible points or to operate in oil wells. Eccentrics. The eccentrics to be strong and light to reduce the strain upon the governor springs, and hung on hardened steel pins operating in removable bronze bushings. The eccentric straps to be lined with best quality of antifriction metal. Ample means of lubrication to be provided and designed to be free from oil throwing when in motion. Governors. Each engine to be equipped with a centrally bal- anced centrifugal inertia governor which will maintain a perfect condition of balance in all positions of cut-off, and operate with equal ease and isochronism from zero to 62.5 per cent cut-off. The governor pins and bushings to be made of steel and bronze, the former hardened and ground true. The lever-arm bearing to be of the antifriction type. Steam consumption. Each bidder must state in proposal sheet the indicated horse-power, full load of each engine, and the maxi- mum steam consumption when operating under conditions herein specified at uniform varying loads, which will receive consideration in award of contract. Each engine when operated under conditions herein specified and at uniform varying loads must not consume more than the amount of dry steam in pounds per indicated horse-power per hour, deter- mined by the weight of condensed exhaust steam, for each load as stated below: SMALL POWER PLANTS 297 LOAD 25 per cent 60 per cent 75 per cent 100 percent 125 percent 50-kilowatt generator engine, dry steam 100-kilowatt generator engine, dry steam 37.6 33.3 31.7 25.3 29.6 23.8 29.2 24.3 29.7 25.3 Shop test of engines. The efficiency, capacity, etc., of each engine to be determined by actual test in the presence of the Department's authorized agent, who shall determine the test conditions. The tests are to be made at the shop where engines are con- structed, and are to begin within ten days after receipt of notice from the contractors of their readiness to commence tests, and to be at the expense of the contractors, except traveling and other ex- penses of the Department's agent. Engines to be run at one-half, three-quarters, full, and one and one-quarter loads for one hour under each load, during which time the exhaust steam will be condensed and weighed, and indicator cards taken every five minutes. Engines to be run at the speeds specified with steam at 110 pounds pressure per square inch at the throttle, quahty of which will be determined by throttling calorimeter placed in steam pipe above throttle. "Under above conditions the friction load must not exceed 5 per cent of the normal capacity of engine for the 50-kilowatt gen- erator engine, and must not exceed 7 per cent for the 100-kilo- watt generator engine. It must be distinctly understood as one of the conditions under which bids are submitted for the work embraced in this specifica- tion that the engines must meet every requirement of the tests above specified, under which conditions the contract price will be paid. In the event the engines fail to meet the requirements for steam consumption or friction load, or both, the Department shall have the right to reject the engines absolutely and require the supply of satisfactory engines which comply with the specifi- cation requirements in regard thereto; or, if the Department elects to accept the engines, the contract price shall be the amount named in the contract for a satisfactory plant, less the amount of 298 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS deficiencies shown by tests above described upon the following basis : Nine hundred dollars per pound or proportional part of said $900 for each fraction of a pound below the guaranteed efficiency for the 50-kilowatt generator engine, and $1800 per pound or proportional part of said $1800 for each fraction of a pound be- low the guaranteed efficiency for the 100-kilowatt generator engine, based on any or all of the varying loads, irrespective of economy at other loads. Two hundred and fifty dollars for each per cent or propor- tional part of said $250 for each fraction of a per cent above the specified friction load for the 50-kilowatt generator engine, and $500 for each per cent or proportional part of said $500 for each fraction of a per cent above the specified friction load for the 100-kilowatt generator engine. The Supervising Architect reserves the right to waive these tests or any portion thereof and to require contractor to submit certified test sheets, in triplicate, for approval, it being under- stood that those portions not waived shall be exacted when ap- paratus is installed if not performed at shop as specified above. Regulation. After engines are installed in position they must be adjusted to run smoothly and practically noiselessly. They must be tested at shops for regulation, which tests must show that slow change from no load to full load and vice versa will not produce more than li per cent speed variation, and from full load suddenly thrown on or off the speed variation shall not be over 2 per cent. Fittings. Each engine to be furnished with the following fittings : One throttle valve. Automatic cylinder relief and drain valves. Mechanical cylinder lubricator, piping, etc. Auxiliary hand oil pump. Steam chest drain connections with valves. Indicator piping with three-way cocks and angle globe valves. Attached indicator reducing motion. Set of adjusting wrenches on hardwood board. All necessary drip, drain, and indicator piping, which must be brass, nickel plated, exposed above floor. SMALL POWEB PLANTS 299 GENERATORS Type. Generators are to be direct-connected, engine-driven, nterpole type for 125-volt direct current, each mounted on sub- 3ase, connected to its engine sub-base. One to have full-load •ating of 50 kilowatts and one to have full-load rating of 100 kilo- watts at the speeds determined by the full load speeds of engines )7hich must be between the limits previously stated. Considera- iions will be given to proposals based on generators without nterpole feature. The armatures and commutators to be built upon ventilated ileeves or spiders, arranged to be pressed on and keyed to shafts. The field or magnet frames to be provided with screws and liners 'or adjustment in position. Frames. The frames of generators to be made of a high-grade ;ast steel or of cast iron of high permeability, sound and free from jlowholes. The seats for the pole pieces to be accurately finished; seats for the bolt heads and nuts to be faced. Poles. The poles to be made- of laminated steel or iron, bolted ;o the frames. The interpoles to be of steel, bolted to the frames. Field Coils. The main field coils to be form wound, provided with ventilating ducts, and be so secured that they may be readily •emoved without unwinding; to be so proportioned as to auto- natically give the voltages specified under "Regulation;" and be jroperly insulated in a substantial manner with material of the jest quality and thoroughly tested. Armatures. The armatures to have slotted cores. The wind- ngs to be thoroughly insulated, provided with ventilating ducts or cooling the windings, and coils to be securely held in place. The armatures must be balanced both mechanically and elec- irically. Commutators. Commutator segments to be of drop-forged or lard-drawn copper of highest conductivity, insulated with mica of iven thickness and proper hardness to insure uniform wear, and nust run free from sparking or flashing at the brushes at any load ir during change of load. They must have ample bearing surface ind radial depth for wear. Brushes. Brushes to be of carbon, of such size and number as nil carry all the loads covered by this specification without in- urious heating. 300 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS With the fixed position of the brushes, there is to be practi- cally no sparking or burning of the brushes or blackening of the commutator within the limits of the time loads specified, nor any injurious sparking at the momentary overloads specified. Brush holders. The brush holders to be so constructed that the tension on any brush may be adjusted without lifting the brush from the commutator and without the use of any tools; and that any brush can be removed while the machine is in operation without disturbing the others and without moving the holder on the stud. Flexible connections to the brushes to be used to prevent injurious current in parts of brush-holder mechanism. The brush holders to be mounted on studs extending from suit- able yokes or rings, which must be supported from the frames. Regulation. The voltage regulation to be 110 volts no load to 117 volts full load based on a variation of speed in the engine of not more than 2 per cent from no load to full load. Insulation. The frames of machine must have an insulation resistance from the field coils, armature windings, and brushes of not less than 1 megohm. Generators to be capable of standing a breakdown test of 1500 volts alternating current for one minute. Heating effect. Generators are to be run continuously at full rated load until all parts have reached a constant temperature and for one hour thereafter, at which time the temperature rise of the armatures and field coils shall not exceed 35° C. and of the commutator 40° C. above the surrounding air, corrected to 25° C. Immediately following the full-load run, and starting with tem- peratures not less than the final temperatures of full-load run, each machine shall be operated for two hours at 25 per cent over- load, at the expiration of which time the temperature rise of the armature and field coils shall not exceed 50° C. and of the com- mutator 55° C. above the surrounding air, corrected to 25° C. Efficiencies. The efficiencies of generators must not be less than the following: One-half Three-quarters Full One and one-quarter. lOO-KILOWATTS 50-KILOWATTS 88.5 88.0 89.0 88.0 88.5 87.5 87.5 86.0 SMALL POWER PLANTS 301 Shop test of generators. The efficiency, heating effect, insu- ition resistance, etc., of generators shall be determined by actual 3st in the presence of the Department's authorized agent, who ball determine the test conditions. The test to be made at the shop where generators are con- tracted, and to begin within ten days after receipt of notice rom contractors of their readiness to commence test, and to be at be expense of contractors, except traveling and other necessary xpenses of the Department's agent. The Supervising Architect reserves the right to waive these ests or any portion thereof and to require contractors to submit ertified test sheets in triplicate for approval, it being under- tood that those portions not waived shall be exacted when ap- paratus is installed, if not performed at the shop as indicated hove. THREE-WIRE GENERATORS In all new plants, and in all old plants in which the motor quipment and the generator sets are to be entirely replaced and he building rewired, the practice of the office now is to install a -wire system and use 3-wire generators. The 3-wire system allows a saving of 25 per cent of the weight if copper in the feeders, when figures are on ■'be basis of current apacity, and a saving of 62| per cent when figured on a basis if drop in potential; the neutral wire being considered as equal a size to one of the outside wires. The 3-wire system admits if using 110 volts for the lighting system, which is the most de- irable voltage, and 220 volts for motors, which is the most de- irable from a standpoint of first cost and general operating con- litions. The half voltage obtainable from either side of the ystem is also desirable for variable-speed motor work or low ^oltage lamps. A 3-wire machine consists of a standard 2-wire machine with he additions described below. Four slip rings are mounted on the shaft and connected with the .rmature winding at intervals corresponding to 90 electrical de- :rees, where 360 electrical degrees is taken as the distance between wo poles of the same polarity. The voltage at the slip rings is -phase alternating. 302 MECHANICAL EQUIPMENT OP FEDERAL BUILDINGS The balance coils are connecfced one to each phase. Each balance coil has a neutral wire connected to its winding midway between the end. These are connected together and form the neutral of the 3-wire direct current system. One bal- ance coil could be employed but the 2-phase connection has been found to give a better distribution of current in the generator armature and a better voltage regulation. Balanced voltage. The action of the coils in balancing the voltage on the two sides of the system may be readily understood by reference to the accompanying figure. Only one coil is shown. It is connected through slip rings to points C and D of the generator armature. Windings and con- nections being symmetrical, it is evident that when the terminals of the balance coil C and D are directly under the brushes, that is, when the point D coincides with the point A and the point C with the point B, the balance coil is subjected to the full voltage of the generator and the potential between the middle point E and each outside wire is equal to one-half the generator voltage. Also, when the armature has rotated 90° further so that the point C and D lie directly under the poles, the balance coil is not sub- jected to a difference of potential and the voltages between the neutral and the outside wires on the two sides of the system are respectively equal to the voltages between D and A , and C and B. In any other position of the armature, the voltage between E and A is the resultant of half the voltage of the balance coil aad the voltage of the segment of the armature winding between D and A. As the voltages generated in equal parts of the armature are equal, the voltage generated in segment AD equals that gener- ated in segment BC, and, since E is the midpoint of the balance SMALL POWER PLANTS 303 joil SO that the voltage between E and D is always equal to that petween E and C, it follows that the voltage between E and A nust always equal that between E and B, and that E is therefore the neutral point at all times. . Armature. The armature winding of the standard Westing- biouse 2-wire generator is unchanged except the coils which have the taps brought out and connected to the collector rings. Fields. The series coils of compound wound 3-wire generators ire divided into halves, one of which is connected with the posi- tive and one with the negative side. This is done to obtain compounding on either side of the system when operating on an unbalanced load. To show this more clearly consider the case Df a generator with the equalizer in the negative side only and with the majority of the load on the positive side of the system. The current flows from a positive brush through the load and back along the neutral wire without passing through the series field. The generator is then operating as an ordinary shunt machine. If the majority of the load be connected to the negative side, the current flows out the neutral wire and back through the series field, boosting the voltage the same amount as a 250-volt load taking the same amount of current. Such operation is not satis- factory and so the two series fields are provided. Equalizers. As there are two series fields, two equalizer busses are ^required. Tenninal boards. Owing to the equalizer connections, two similar terminal boards are supplied, one for each side of the generator. Ammeters. Two ammeters must be provided for reading the current in the two outside wires. It is important that the cur- rent be measured on both sides of the system, for, with ammeter in one side of the system only, it is possible for a large unmeasured current to flow in the other side of the system. Switchboard connections. One voltmeter is connected across the outside wires. Two ammeters should be used to indicate the inbalanced load. The positive lead and equalizer are controlled Dy a double pole circuit breaker, the negative lead and equalizer should be likewise protected. Both the positive and negative nain leads and equalizers are ordinarily provided with single pole single throw switches. 304 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS Unbalanced load. Standard balance coils are supplied of ca- pacity suitable for an unbalanced load of 10 per cent of the full load current, that is, a current in the neutral equal to 10 per cent of the full load current of the machine. For example, take a 100- kilowatt 250-volt generator. Full load current amounts to 400 amperes, at 250 volts, 10 per cent of this amounts to 40 amperes. Regulation. The regulation of a 3-wire generator when oper- ating on a balanced load will be the same as any standard 2-wire generator. With 10 per cent unbalance, the variation in voltage between the neutral and outside wires will not exceed 2 per cent below or above normal. Balance coils. Each of these consists of a laminated core and single winding with a neutral tap brought out from its middle point. Whatever the A.C. voltage impressed on the ends of the winding, the voltage between one end of the winding and the neutral is one-half of the total voltage. Winding and core are enclosed in a cast-iron case, which is filled with transformer oil. In the event it is desired to use a 3-wire generator the foregoing specifications for a 2-wire generator are modified as follows: Type. The generators are to be direct connected, engine driven, interpole type for 3-wire 125-250 volt direct current, each mounted on a sub-base connected to its engine sub-base. One to have a full load rating of 50 kilowatts at 285 r.p.m. and one to have full load rating of 100 kilowatts at 250 r.p.m. The armatures and commutators to be built upon ventilated sleeves or spiders, arranged to be pressed on and keyed to shafts. The field or magnet frames to be provided with screws and liners for adjustment in position. Frames. The frames of generators to be made of a high grade cast steel or of cast iron of high permeability, sound and free from blowholes. The seats for the pole pieces to be accurately fin- ished, seats for the bolt heads and nuts to be faced. Pole. The pole to be made of laminated sheet steel, bolted to the frames. The interpole to be steel bolted to the frames. Field coils. The main field coils to be form wound, provided with ventilating ducts, and be so secured that they may be readily removed without unwinding. The series field will be divided so that one-half will be connected in the positive line, one-half will be connected in the negative line; and so proportioned to auto- SMALL POWER PLANTS 305 natically give the voltages specified under "Regulation," and be proper ly insulated in a substantial manner with material of the Dest quality. Armatures. The armature to have slotted cores, the windings ;o be thoroughly insulated, provided with ventilated ducts for ;ooling the windings and coils to be securely held in place. Pref- irence will be given to 2-phase, 3-wire connections on account )f the better balanced voltage. The armature must be balanced )oth mechanically and electrically. Commutators. Commutator segments to be of drop forged or lard drawn copper of high conductivity, insulated with mica of !ven thickness and proper hardness to insure uniform wear; and nust run free from sparking, flashing or burning at the brushes bt any load or during change of load. They must have ample )earing surface and radial depth for wear. Brushes. Brushes to be of carbon, and of such size and num- )er as will carry all of the loads covered by this specification without injurious heating. With a fixed position of the brushes, there is to be practically LO sparking, flashing or burning of the brushes, or blackening of he commutator within the limits of the time load specified or ,ny injurious sparking at the momentary load specified. Brush holders. (No change.) Regulation. The voltage regulation to be 230 volts no-load to 50 volts full load based on a variation of speed in the engine of ot more than 2 per cent from no-load to full-load. With 10 per cent unbalanced load in the neutral wire or 40 mperes for the 100-kilowatt generators and 20 amperes for the 0-kilowatt generator the variation in voltage between the neutral nd the outside wires will not exceed 2 per cent above or below ormal. Insulation. (No change.) Heating effect. (No change.) Efficiencies. (No change.) Switchboard. (Must be changed to suit 3-wire system of istribution.) CHAPTER X MOTORS AND CONTROLLING APPARATUS DIRECT CURRENT The reasons given for using interpole generators apply more forcibly to direct-current motors. The instantaneous overload is large and more frequent, and the continued overload obtains more often on individual motors than on generators supplying several motors. Also the interpole provides the proper com- mutating field when motors are run at increased speeds by field control, and consequently with weaker magnetic conditions. The mechanical construction should be rigid but the weights should be kept down to the safe minimum. Steel frames are there- fore desirable from both standpoints. The bearings should be dust and oil proof. The efficiency should be high and the overload capacity ample. The speed should be approximately the same as the full load speeds of induction motors, thus simplifying the application of motors to pumps and fans, as it is desirable in some of the Federal buildings to use alternating-current circuits. It is desirable to operate motors on 220 (or preferably 230) volts, rather than at 115 volts. Standard commercial speeds and horsepower ratings from 1| H.P. to 20 H.P. and 230 volts are as follows for interpole motors: Horsepower Full load R.P.M. li 900 2 850-1200 3 1150-1800 5 850-1100-1800 7i 650-850-975-1150-1700 10 600-730-850-1150-1300-1700 15 600-675-825-1100-1250-1700 20 650-750-900-1100-1700 This table, however, applies to 115 volt interpole motors except 7| to 20 H.P. motors, inclusive, which are not usually built for 1700 R.P.M. 306 MOTORS AND CONTROLLING APPARATUS 307 The commercial efficiencies of 230-volt interpole motors at full load are as follows: HORSEPOWER RATED ?^PEED 3 600 720 900 1200 1800 1.5 84.5 85.0 86.0 87.5 84,5 85.5 85.5 88.0 74.5 76.5 79.0 83.5 85.5 87.0 88.0 88.0 77.5 80.0 83.5 85.5 86.5 88.5 89.0 2 3 79 5 5 81 5 7.5 86 10 86 15 87 5 20 88 5 The commercial efficiencies of 115-volt interpole motors at full load are as follows: HORSEPOWER RATED SPEEDS 600 720 900 1200 1800 1.5 84.5 85.5 87.0 84.5 84.5 85.5 87.0 72.5 76.5 7.90 82.0 84.5 86.0 86.0 87.0 77.0 80 83 85 86 87 88 2 3 78.5 5 7.5. 80.6 10 15 20 Methods of speed contfolfor direct-current motors. 1. Arma- ture Control, or regulation of the voltage at the brushes by means of an adjustable resistance in series with the armature. Recom- mended for some service in which speeds lower than normal are desired as in controlling the speed of fans, blowers, centrifugal pumps, etc. 2. Field Control, or regulation of the field strength by means of an adjustable resistance in the shunt field circuit. Recom- mended for service in which speeds higher than normal are desired, as in operating machine tools. Armature control. With constant torque, the motor current is constant regardless of the speed. Therefore every change in the 308 MECHANICAL EQUIPMENT OF FEDERAL BtTILDINGS controlling resistance in armature control produces a correspond- ing change in voltage drop in the resistance and a like effect on the motor speed. Moreover, the motor speed remains constant at any adjustment. The motor output is proportional to the product of the torque and speed, and the former remaining con- stant, the output must vary with the speed. For example: At one-half speed the motor output is one-half that corresponding to the same torque at full speed; and since the voltage at the brushes must be one-half that of the line, the voltage drop in the con- trolhng resistance equals the voltage at the brushes. That is, one-half the total energy taken from the line is absorbed by the resistance and the efficiency of the motor and controller cannot be over 50 per cent. Constant reduced speeds with varying torque cannot be ob- tained by armature control. Fans, blowers and centrifugal pumps require an unvarying torque at each speed, and with fans and blowers the torque de- creases very nearly with the cube of the speed, making this control fairly economical. For service requiring a continuous operation with full-load torque at reduced speeds, adjustment by armature control is very inefficient, as much energy is lost in the resistance. Field control. With constant voltage at the brushes, the speed of direct-current motors varies practically in inverse proportion to the change of field magnetism, that is, the weaker the field the higher the speed, and vice versa. The field magnetism changes with the change of shunt field current, though not always in direct proportion thereto. The torque decreases in proportion to the decrease in field magnetism; the horsepower output, being pro- portional to the product of the speed, and torque remains practi- cally constant throughout the entire range of speed. With shunt motors, the speed regulation at any given speed is good, in fact, practically constant at all loads within the motor capacity. This is of especial importance to the operation of ma- chine tools and in service of any character where constant speed with varying torque is desired. Speed control. Starting devises should be provided with au- tomatic control so that a failure of voltage, or excessive overload, will open the circuit and voltage can not again be impressed on the motor or the starter, without connecting the proper resist- MOTORS AND CONTROLLING APPARATUS 309 ance in the circuit. All starters, therefore, should be provided with a no-voltage release so that on resumption of the power full resistance will be inserted between the line and the motor; and Bither circuit breakers, fuses or magnetically operated switches should be provided so that the excessive overload will not damage the apparatus. Remote control. Two general principles are employed, the constant time element and litnitiag starting current on successive steps. A. The constant time eleme;nt is desirable where a smooth evea acceleration is required as in starting a belt driven load of large inertia. B. The limiting current method is desirable where starting con- ditions require acceleration in steps depending on starting current conditions, as with pumps, elevators, and similar service. Two types of automatic-control auxiliaries are in general use : A. Float type switch, or a float, in an open tank, which closes the relay circuit, at either the lower or higher predetermined level, and starts or stops respectively the motor, by means of magneti- cally operated switches. B. Pressure type, or a pressure gauge, in a closed pressure sys- tem, which operates in a similar manner at a predetermined lower or higher pressure. Armature control. A face plate constant speed hand-operated starter provided with no-voltage release is satisfactory up to 20 H.P. capacity. Drum type controllers should be used from 20 H.P. to 50 H.P. capacities or where frequent starting and stopping duty is required. No-voltage release should be provided in con- nection with the starters. A fused line switch, circuit breaker or similar device should be provided, with the starter, so that the circuit will be opened on excessive overload, should the operator hold the starting handle on an intermediate resistance point. All starters should be arranged to automatically cut in the properresistance, once the circuit is opened, either through voltage failure or excessive overload, so that the motor and controller will be protected on resumption of power. This can be accomplished either mechanically or by means of magnetically operated switches, electrically interlocked, so it is necessary to move the handle to the off position, before again connecting the apparatus in circuit. Multiple switch starters should be used above 50 BC.P. capaci- 310 MECHANICAL EQUIPMENT OP FEDERAL BUILDINGS ties, arranged with interlocks, so the switches can only be closed in proper order, and should be provided with full overload and no-voltage release protection. The same specifications apply with the addition of proper re- sistance steps to operate continuously at reduced speeds. A con- stant speed motor is capable of a small increase in speed, say 15 per cent, by field control, and where necessary, the starters can be arranged with an auxiliary control to increase the speed, by cutting resistance in series with the shunt field. Remote control. Starters, in addition to the use as indicated by the name, eliminate the personal element, insuring always the same appKcation of the machinery under consideration. Acceleration is accomplished by means of magnetically operated switches, controlled by relays, and so interlocked that a failure of any of the switches will prevent the motor circuit being closed. Full overload and no-voltage release should be provided. Either face plate or drum type regulators may be used as the master switch only controls the relay circuit. For remote control speed regulating the master switch should be provided with proper latching mechanism, so continuous op- eration can be obtained, at reduced speed. Indicating lamps or gauges should be provided to show the operating speed. Field control. For variable speed the same type of controller should be used as specified under the various sub-divisions under constant speed motors, with the addition of a field regulating rheostat, interlocked with the starter in such a manner that it is impossible to start the motor with weakened field. ALTERNATING CURRENT MOTORS Alternating current motors should be of the induction type, with rigid but light construction provided with ample size of bearings to be both dust and oil proof. Because of the simple mechanical construction, great rugged- ness and reliability, squirrel-cage motors should be used for con- stant speed service, except where a starting torque of more than 1 to 1| times full-load torque is required, or where it is necessary to keep the starting current below 2| to 3| times the normal load current. If more severe conditions must be met, motors having phase-wound rotors should be specified. The question of starting current on small induction motors is MOTOES AND CONTROLLING APPARATUS 311 often given undue prominence. In actual practice it is found that even when a large proportion of the total connected load is com- posed of small squirrel-cage motors, which are frequently started and stopped, that the maximum peak load is but a small per- centage increase over the normal load. It is true that squirrel- cage motors while starting take from 2J to 3| times full-load current, but this maximum, as a rule, does not exist more than five seconds, and as the motor speed increases the current falls rapidly. Two or three times full-load current of a motor, which is only 10 per cent of the total capacity of the motors installed, is only about 25 or 30 per cent of the total current taken when all the motors are operated. The commercial speeds and horsepower of 3-phase, 60-cycle, 220-volt, squirrel-cage induction motors are as follows : Horsepower Full load R.P.M. 1 1700 2 1135-1710 3 1140-1720 5 560-670-859-1130-1700 7i 560-670-850-1130-1710 10 560-675-850-1125-1710 15 565-680-855-1135-1710 20 565-675-850-1135-1700 The standard gear ratio for back-geared motors is approxi- mately 5 to 1. Motors with a synchronous speed of 1800 R.P.M. are not usually geared above the 3-horsepower size. The full-load efficiencies and power factors of the above motors are as follows : R. P. M. HORSB- POWEB 600 720 900 1200 1800 PF. Eff. PF. Eff. PF. Eff. PF. Eff. PF. Eff. 1 2 3 5 7.5.... 10 15 20 82 80 80 84 83 81 84 84 86 87 81 80 84 85 84 83 83 84 86 85 83 83 86 86 85 85 85 85 85 85 78 81 86 85 90 89 91 84 84 84 84 85 86 87.5 80 80 86 88 90 90 91 93 77 84 85 85 85 85 86 87 312 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS Auto-starters furnish the most satisfactory means for starting squirrel-cage induction motors. They reduce the voltage initially impressed upon the motor primary, and simultaneously supply the increased current needed for starting, without drawing excess cur- rent from the line. For this purpose they are more efficient than any form of rheostatic starter, their internal losses are small, and it is practically impossible to injure the motor or the starter. The essential features are two auto-transformers, by means of which the reduction in voltage in two of the phases is obtained, and a switching mechanism for connecting the motor primary, first across a portion of the auto-transformer taps, and then directly across the line. The switching mechanism and starter can be enclosed in the same iron casing, or the two can be mounted separately. Con- tacts of the oil-immersed butt type give the most satisfactory operation. Motors up to and including 5 H.P. can be thrown directly on the line and should be provided with a fused switch. Motors over 5 H.P. should have automatic protection. The starting current being so much larger than full load current fuses or circuit breakers would open at starting, consequently starters should be provided with two sets of line leads, one for starting and one for running. The starting leads may, or may not, be provided with overload protection, according to the start- ing conditions, but fuses, or a circuit breaker, must always be provided for. the running leads. Auto-transformers should be provided with no-voltage release, and can be provided with overload release when desired. Remote control starters. Acceleration can be accomplished in two general ways : A. Magnetic switches operated through relays, by means of a controller. B. Mechanically operated auto-transformers with bell craaks or rope drive, or where compressed air is available, by means of an air cylinder connected to the starting mechanism of the auto- transformers. Both devices should be provided with full overload and no- voltage release. MOTORS AND CONTROLLING APPARATUS 313 PHASE-WOUND INDUCTION MOTORS Phase-wound or slip-ring induction motors develop high starting torque without drawing excessive current from the line. They are, therefore, well adapted for driving machinery, requiring a strong starting effort on circuits where close voltage regulation is neces- sary, as in starting heavy machinery when the motor is operated from a lighting circuit. These motors are especially adapted to constant speed service for operating all classes of constant speed machinery, such as the operation of hoists, pumps, compressors, etc. With full-load torque these motors will start and accelerate with current not exceeding one and one-fourth times full load. The secondary electromotive force is that necessary to drive the secondary currents through the windings. It follows that the electromotive force required must depend on the resistance of these windings. A larger resistance means a larger electromotive force for the required current and, therefore, a greater number of secondary alternations or a greater shp; the torque being held constant, any variation of the secondary resistance requires a proportionate variation in the slip. If the slip with a torque is 10 per cent, for instance, it will be 20 per cent with double the secondary resistance, or 50 per cent with five times the resistance. The secondary resistance may be in the windings themselves or entirely separate from the machine and connected to the winding through slip rings. This means that the speed of a phase-wound motor can be varied below synchronous speed by inserting external resistance by means of a proper controller. The phase-wound induction motor should be used, therefore, when it is necessary to reduce the starting current of the motor on account of resultant effect on the lighting system when the motors are operated from the lighting circuit; when high starting torque is necessary; or when it is desirable to vary the speed of the apparatus which is motor driven. The commercial speeds and horsepower of 3-phase, 60-cycle 220-volt, phase-wound induction motors are as follows: 314 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS Horsepower Approximately full load speed 5 860-1120-1710 7i 860-1120 10 580-690-860-1140 ■ 15 580-690-870-1150 20 580-690-860-1150 The full-load efficiencies and power factors of above motors are as follows : R. P. M. HORSE- POWER 600 720 900 1200 180J PF. Eff. PF. Eff. PF. Eff. PF. Eff. PP. Eff. 5 7.5.... 10 15 20 77 81 80 85 86 87.5 82 82 82 86 87 87 80 78 81 83 83 85 85 86 87 86.6 84 80 85 87 89 83 83 86 88.5 87 86 87 83 87 It is preferable in specifications to scale all efficiencies and power factors from | to 1 per cent from those given above, and while the best commercial results are desired the specification should not be made too rigid. CONTROL Constant speed, hand starting. Drmn type controller with auxiliary resistance should be used up to approximately 100 H.P., the circuit provided with no-voltage and overload release. The starters are only connected with the secondary windings and are used to accelerate the speed by short circuiting successive resist- ance steps in each phase. All these phases should be intercon- nected and grounded to prevent shock to operator. The resist- ance may be integral with or separate from the controller of the motor. Multiple switch-type starters should be used for larger motors, the switches being interlocked to provide proper sequence of operation. No-voltage and overload release should be provided. Variable speed, hand operated. Controllers should be in gen- eral the same as above, except equal resistance steps should be MOTORS AND CONTROLLING APPARATUS 315 provided so the motor can be run continuously at speeds less than synchronous. Remote-control starting. Magnetically operated switches should be used to short circuit successive resistances. The switch should be interlocked to insure operation in the proper sequence and be provided with fall overload and no-voltage release. Face plate or drum type controller should be used to operate the relay circuit controlling the magnetic switches. CHAPTER XI VACUUM CLEANING SYSTEMS Stationary. The specifications prepared in the office of the Supervising Architect for vacuum cleaning systems of the sta- tionary type with vacuum producers and separators located on permanent foundations, and with a piping system having out- lets throughout the building, admit the use of apparatus of both the so-called high-vacuum and low-vacuum types, with certain restrictions. The high-vacuum type is required to use a 1-inch diameter cleaning hose and maintain under test conditions a vacuum equivalent to 12 inches of mercury in a separator that first receives the dust. The low-vacuum systems are required to use a If-inch diameter hose and to maintain when operated under test conditions a vacuum equivalent to 6 inches of mercury in the separator that first receives the dust. For large buildings which do not contain an electric generating plant and in which high-pressure steam is maintained throughout the year, consideration is given to the installation of vacuum pro- ducers of the steam jet type. Contrary to the generally accepted opinion, first class devices of this type are, when provided with efficient controlling devices, fully as economical as high-grade steam or electrically driven vacuum pumps. In buildings like hotels, where cleaning must be constantly going on throughout the day, with from one-fourth to one-half the plant capacity in use, the jet producers are far more economical in operation than pumps of any type. In addition to the relative low cost for maintenance and repairs, the steam jet devices have the merit of low first cost, simplicity in construction, and economy of space. Positive displacement pumps of the piston or double-impeller rotary type are permitted under the specifications. The reciprocating type of exhauster when fitted with poppet type of valve is limited to a piston speed of 200 feet per minute in order to insure quiet running. When the rotary type of valve is used a piston speed of 300 feet per minute is permissible. Pref- 316 VACUUM CLEAISriNG SYSTEMS 317 erence is given to machines of the lower speed as making for longer life and fewer repairs. The specifications for the reciprocating type of vacuum, pro- ducers require strictly first-class workmanship; no pockets or clearance spaces are allowed in pistons; piston rings are required to fit grooves both in width and depth. Valves are required to be placed in heads and the clearance reduced to a minimum. The cylinders are required to be jacketed; frames must be of ample strength; cross heads and slides are required and all bearings must be lined with anti-friction metal. These specifications are im- portant to prevent the use of vacuum producers of less merit. Rotary exhausters of the double-impeller type are limited to a peripheral velocity of 1100 feet per minute to insure quiet running. They are required to be provided with gearing running in oil or grease, and must be fitted with water jet for cooling and sealing the impellers. At all vacua below 12 inches this type of exhauster is more economical than the best reciprocating type; it is practi- cally free from wear, and from damage due to foreign substances entrained in the air entering the exhauster; the first cost is less, and few repairs are required. Exhausters of the centrifugal type are admitted by the specifi- cations and their speed is limited to a peripheral velocity of 15,000 feet per minute. Exhausters of this type are required to have air-tight casings of aluminum or cast iron, and plain or ball bear- ings; and preference is given to machines of the type which are provided with vertical shafts so arranged that the weight of mov- ing parts equalizes the end thrust. Machines of the centrifugal type require special high-speed motors, which are subject to ex- tensive repairs. Careful erection is necessary to reduce vibration and noise to a minimum. This type of exhauster is suitable for low vacuum only. All positive displacement and all centrifugal types of exhausters installed in Federal buildings are motor-driven. In all of the cleaning systems installed in Federal buildings a dry separator is required to be placed between the suction lines and the exhauster. The dry separator must be cylindrical, constructed of sheet steel, and provided with cast iron or steel heads. No bags or screens are permitted to be installed in this separator. The 318 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS action of separator must be purely centrifugal and the device must intercept not less than 95 per cent of the total dust entering same. With all positive displacement types of exhauster a second sepa- rator is required to be placed between the centrifugal dry sepa- rator and the exhauster. The second separator must positively remove all dust from the air before it enters the exhauster. The second separator may be either of the wet or dry type; and if of the latter type may have a bag or core composed of "hush cloth" or other suitable material, which must be properly reinforced to prevent rupture and so arranged that it may be cleaned without dismantling the separator. If the second separator is a wet separator it may be cylindrical like the dry separators or may be formed in the base of the ex- hauster. In either case it must be provided with means for posi- tively mixing the air and water and thoroughly breaking up all bubbles, and must positively separate the water from the air and prevent water and dirt from entering the exhauster. With the steam jet or centrifugal types of exhausters this second separator may be omitted. Separators are required to have a cubic contents of 3 cubic feet for each sweeper of plant capacity, for high-vacuum and 4.5 cubic feet per sweeper of plant capacity for low-vacuum systems. The specifications require that all steam jet and positive dis- placement type of exhausters must be provided with a device for automatically controlling the vacuum. The control must main- tain within certain limits a predetermined vacuum in the dry separator. The controlling device may be of the electrical type operated by the vacuum in the dry separator to vary the speeds of the exhauster and maintain a constant vacuum in the dry separator. This type of control when used, requires the motor to have special windings so that its speed may be varied from one-third to full speed by variation of the strength of shunt field only. The controller may be of the mechanical type which is intermit- tent in action and which closes the suction of the exhauster when the vacuum reaches a certain point and opens the suction when the vacuum falls 2 to 2| inches below the determined amount. The controller may also be of the type that opens the suction of VACUUM CLEANING SYSTEMS 319 the motor-driven exhauster to atmosphere; or that cuts off the steam to the jet type of exhauster and holds the vacuum in the separator by means of check valves when the vacuum in the dry separator reaches a certain point and closes the air inlet to suction of motor-driven exhauster; or that turns on steam to jet type when vacuiun falls 2 to 2| inches. All of these control systems are required to effect a saving in power which is determined by operating the exhauster with all hose inlets closed as hereinafter explained under the heading of tests. Centrifugal types of exhausters do not require any controlhng device as features inherent in the design thereof tend to produce and maintain a constant vacuum within the capacity of the machine. With all positive displacement exhausters a positive acting vacuum-breaker is required to be furnished as a safeguard in the event the control fails to operate. The power per sweeper required to operate cleaning plants of from four to eight-sweeper capacity when operating the full num- ber of sweepers on stiff-backed carpets has been determined by tests to be as follows : SEPAHATOHS POWER PEH SWEEPER High vacuum Low vacuum Reciprocating Wet and dry 2 dry 2 dry Wet and dry Idry kilowatt 2.36 2.15 2.06 2.80 kilowatt 2.22 Reciprocating 1.98 Double cam rotary Double cam rotary Centrifugal 1.32 1.80 1.98 High vacuum Low vacuum Steam jet ... 250 pounds steam ner 200 pounds steam ner hour hour The tests were made under the most favorable conditions as re- gards power consumption, as the air handled is at a minimum, i.e., 43 cubic feet per minute for high vacuum, and 60 cubic feet per 320 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS minute for low vacuum. When cleaning bare floors, walls, re- lief work, or pigeon holes, the amount of air passing through the cleaning tool is practically equal to that passed by an open hose. Capacity tests of sweeping plants are made with hose lines 100 feet long equal in number to the plant capacity, with ends open to atmosphere, under which conditions the high vacuum will handle 55 cubic feet and the low vacuum 80 cubic feet of free air per sweeper per minute. The power required by the system under test conditions above noted is limited by the specifications as follows : Kilowatts per sweeper 6- to 8-sweeper plants 3j 3- and 4-sweeper plants SJ 2-sweeper plants 3f 1-sweeper plants 4 The specifications require each bidder to state the size of motor he proposes to use, which under test conditions must not be over- loaded and must not operate under less than three-quarters of its rated power. The motor must be constructed in accordance with the standard motor specifications prepared by the Supervising Architect; and may have shunt, compound, or interpole windings, as the type of control requires. In addition to the capacity test hereinbefore described a test is made to determine the tightness of the system. This is done by subjecting the piping to a test under 7§ pounds air pressure, and after all outlet valves, separators, etc., are connected the ex hauster is operated at the speed specified, and the power required to operate exhauster under conditions noted must not exceed the following. Per cent of power required for ca- pacity test 8-sweeper plants 40 4- and 6-sweeper plants 50 3-sweeper plants 60 2-sweeper plants 65 A test to determine the efl&ciency of the separators is also made. A number of outlets equal to capacity of system are selected, and on the -floor over an area 50 square feet at each outlet, there is VACUUM CLEANING SYSTEMS 321 spread 6 pounds of dry sharp sand (screened through a 50 mesh screen), 3 pounds of wheat flour and 1 pound of powdered charcoal. Bare-floor cleaning tools are then attached to outlets, using 50 feet of hose, and the material is picked up, recovered from the dry- separator, spread out again on the floor and again picked up. This procedure is repeated a third time. At the conclusion of the test the positive displacement exhausters are examined internally, and if a trace of any of the above materials is found it is considered sufficient cause to reject the separators. If the centrifugal or steam-jet type of exhauster is installed the quantity of material recovered from the separator is weighed and if this be less than 95 per cent of the total material picked up the separator is rejected. The air piping is standard, black, wrought-iron or mild steel and ends of all pipes are reamed. The fittings on air pipes must have an inside diameter equal to the pipe bore and may be plain or galvanized cast iron drainage fittings, with a radius of not less than 3 inches at center line when space conditions permit. Fit- tings with less radius are reinforced at point receiving the impact of the dust. A standard flange union is used at the base of each riser to permit repairs. Brass screw-jointed clean-out plugs are provided in fittings at turns and at base of each riser, and plugs in l|-inch line are same size as pipe but are 2 inches in all other lines. Pipe bends are installed on some lines to reduce the friction. Wall outlet sweeper cocks are of the flush type and are pro- vided with hinged or screw covers. If latter type of cover is used a safety chain must be provided to secure same to the outlet. The hinged type must close by its own weight and be provided with a rubber disc or ring to make a tight joint. Floor outlets are located in a brass box set flush with floor, with hinged lid which will not open in a vertical plane and will close by its own weight. Sweeper cocks for high-vacuums are all 1-inch diameter, and for low-vacuums l|-inch diameter. A cabinet containing a complete set of tools is required to be pro- vided for each sweeper capacity of the plant, and at least one com- plete set of tools for each story of the building. The following tools comprise a set : 322 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS One 12-inch or 15-inch carpet renovator. One 12-inch or 15-inch bare-floor brush. One 12-inch or 15-inch wall brush. One 4-inch or 6-inch diameter relief clean brush. One stair-cleaning brush. One 4-inch or 6-inch upholstery brush. One corner of crevice cleaner. One short stem 1 foot long. One long stem 5 feet long. One extension stem 5 feet long. One 45° handle for floor cleaning. One straight handle for woodwork and wall cleaning; or one straight handle with detachable swivel. All renovators except the stair cleaners and round brushes have slots within 15 per cent of the following widths: high-vacuum J inch; low-vacuum | inch. The lips of carpet and upholstery renovators must be so con- structed as to prevent injury to the fabric cleaned and reduce sticking of renovator face to material cleaned. Handles for tools are either cast metal or tubing, and the bore of same is required to be uniform size throughout and same size as stems. Stems are either drawn steel No. 21 gauge or brass tubing No. 16 gauge. Stems are 1 inch outside diameter for high- vacuum and Ij-inch outside diameter for low-vacuum. Exten- sion stems for wall cleaning are aluminum. Carpet renovators are preferred to be cast iron, but either brass or aluminum body with an iron wearing face may be used. Vacuum breakers are required in the tool handles of high vacuum systems, except when renovators are provided with inrush slots or other vacuum-reducing devices. For each set of tools provided a hose rack is installed, and for each rack 100 feet of non-collapsible reinforced hose is supplied, which must not weigh over one pound per lineal foot. The hose couplings are either screw, slip, or bayonet-lock type, with smooth bore of practically same diameter as the hose. Screw couplings have ground joints; bayonet-lock joints may have packing washer; and slip joints have permanent steel pieces on end of hose and brass slip coupling. VACUUM CLEANING SYSTEMS 323 The size of the plant to be installed is based on the floor area of the building and as to whether said floor area will be carpeted or left bare. A stationary plant is not installed in a building where the total floor area is less than 50,000 square feet and where the total car- peted area is less than 20,000 square feet. One operator can clean 3000 square feet of bare floor or 2000 square feet of carpet per hour. The following table is used as a guide in determining the size of the plant, and in this connection attention is called to the fact that the tendency of engineers is toward the installation of too large a plant. Number of sweepers in Floor area, including basement plant capacity 51,000 square feet to 100,000 1 101,000 square feet to 150,000 2 151,000 square feet to 250,000 3 251,000 square feet to 400,000 , 4 400,000 and up 6 In preliminary layouts the following space is allowed for the reception of the future plant : Number of sweepers Space for pump and motor Space for separators 2-3 3 feet by 9 feet 6 inches 2 feet 9 inches by 5 feet 4 3 feet by 10 feet 3 feet by 5 feet . 6 4 feet by 11 feet 6 inches 3 feet by 5 feet 8 5 feet by 14 feet 4 feet by 7 feet 6 inches The minimum height allowed for the small plants is 6 feet 6 inches and for the large plants 8 feet 6 inches. A space of 2 feet 6 inches square is allowed for the control board and a space of 1 foot 6 inches square for the muffler which is re- quired with reciprocating exhausters. The mufiler discharge is; taken into the smoke breeching on stack side of damper; or if conditions demand a separate exhaust pipe is run above the roof. If possible, the risers are located so that all parts of building to be cleaned may be served with not over 50 feet of hose on any outlet. The sweeper cock outlets are located in basement, in the post- afflce workroom, and in the lobbies and corridors; occasionally in 30urt room, but never in an office room. 324 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS If conditions require, risers may be so located that 75 feet of hose will be required to clean all parts of the building. Most of the standard makes of vacuum producers are tapped as follows : HIGH VACUUM LOW VACUUM CAPACITY Inlet Exhaust Inlet Exhaust 1 sweeper 2 sweeper 3 sweeper inches 2 2i 3 4 5 5 inches 2i 3 4 5 6 6 inches 2i 3 4 4 5 6 inches 3 4 5 5 6 sweeper 8 sweeper 6 8 The pipe sizes for the systems to be installed in Federal build- ings are indicated on drawings. They are given for both the high and low-vacuum systems, and are determined by the following method : A table of equalization of pipes, in which each size is given an arbitrary value, is used. To find the size of pipe equivalent of any number of pipes of given size, add the values assigned each size of pipe, and select the pipe size which is the sum of their arbitrary values: Pipe size 1" li" 2" 2i" 3" 4" 5" 6' Constant 10 30 60 110 175 380 650 1050 To determine the size of the risers, assume that only 50 per cent of the total number of sweeper outlets on a riser will be in use at any one time and allow the equivalent of one 1-inch pipe for each outlet in use for high-vacuum and the equivalent of one l|-inch pipe for each outlet in use on low-vacuum systems. No riser to be less than 2-inch diameter and no branch to a single outlet from r'ser to be made less than l|-inch diameter. Example : Assume an 8-story building with eight sweeper out- lets on each riser and with four outlets in use on each riser, under which conditions for high-vacuum 4 X 10 = 40 which underthe rule requires a 2-inch riser. For low-vacuum 4 X 30 = 120, which under VACUUM CLEANING SYSTEMS 325 the rule requires a 2|-inch riser. To ascertain the size of mains required, start at the last riser on any line and make the mainline the same size as riser until the next riser is connected to main; then make the size of the main equivalent to the risers connected thereto until the pipe size is the same as the tapping of the machine used. Example: Assume a 6-sweeper plant in an 8-story building, using a high-vacuum system. The main will start 2 inches and when the second riser is connected 60 + 60 = 120, which under the rule will make the main 2^ inches. When the third riser is con- nected 120 -|- 60 = 180, and the main will be 3 inches. When the fourth, fifth, and sixth risers are added the main will be 4 inches, and when the seventh riser is added the main will be 5 inches in diameter, which is the size of machine tapping. For a low-vacuum system the main will start at 2| inches and when the second riser is connected 110 + 110 = 220, which under the rule makes the main 4 inches; the 4-inch size is maintained until the fourth riser is connected, 110 X 4 = 440, and the main is made 5 inches, which is the size the machine is tapped for, If additional risers are added the main would not be increased. Whenever possible the machine is located near the center of the building and two or more branch mains are used and connected together as one main near the separator. Each of the branches may be made equal to the machine tapping if the number of risers connected to such branch main requires such size under the rules stated. The connection from the point of junction of the mains to the separator may be same size as the largest branch main, or may be increased if desired. No account is taken of basement sweeper outlets when calcu- lating the size of air mains. The basement branches, and any other branches in which material picked up must be lifted, are always made 1| inches for high-vacuum and 2 inches for low- vacuum. Lifts are to be avoided unless absolutely necessary. The above method of calculating the mains is used for all high- vacuum systems, and also for all low-vacuum systems when the distance from the machine to the end of furthest riser does not exceed 400 feet. When the distance is greater than 400 feet the size of mains is calculated from tables of friction loss, etc., and all pipe sizes are 326 MECHANICAL EQUIPMENT OP FEDERAL BUILDINGS checked so that the velocity of the air in the main will not be less than 2000 feet per minute when the plant is operating at full capacity. SPECIFICATION A specification such as is used by the office of the Supervising Architect is as follows for a four-sweeper plant : VACUUM CLEANING SYSTEM General description. The work included in this contract shall be the installation of a complete vacuum cleaning system for the removal of dust and dirt from rugs, carpets, floors, stairs, furni- ture, shelves, walls, and other fixtures and furnishings throughout the building, and for conveying said dust and dirt to suitable receptacles located where shown, together with all of the neces- sary cleaning tools, hose, piping, separators, exhauster, motor, etc., as hereafter more fully specified. Exhauster. Furnish and erect where shown on drawings Nos. V. C. 488 and V. C. 489 an approved air exhauster having a nominal capacity for four sweepers at either high-vacuum, 12 inches, or low-vacuum, 6 inches of mercury, and that shall operate without overload under the test conditions hereafter specified. The exhauster in all of its details shall be made of the best ma- terials suitable for the purpose, and shall be of approved design and construction, and may be either of the positive displacement (piston or rotary) or of the multistage fan type. The piston type of exhauster shall be double acting and so designed that the cylinder clearance shall be reduced to a mini- mum, or suitable devices shall be employed to minimize the effect of large clearance. The induction and eduction valves may be either poppet, rotary, or semirotary, and shall operate smoothly and noiselessly. The piston packing shall be of such character as to be practi- cally air tight under working conditions and constructed so that it will be set out with its own elasticity without the use of springs of any sort. If metallic rings are used, they must fill the grooves in which they are fitted, both in width and depth, and must be concentric — that is of the same thickness throughout. The joint in the ring or rings to be lapped in width but not in thickness VACUUM CLEANING SYSTEMS 327 and if more than one ring is used they are to be placed and doweled in such position in their respective grooves so that the joints will be at least one-quarter of the circumference apart. The piston shall have no chamber or space into which air may- leak from either side of the piston. All openings into the body of the piston must be tightly plugged with cast-iron plugs. The piston-rod stuffing box to be of such size and depth that if soft packing is used it can be kept tight without undue pressure from the gland. If metallic packing is used, it must be vacuum tight without undue pressure on the rod. Proper means shall be provided for the continuous lubrication of the piston rod. The exhauster of the piston type shall be fitted with an ap- proved crosshead, suitably attached to the piston rod; machines having an extended piston rod for guide purposes will not be acceptable. The rotary displacement exhauster shall be of the two-impeller type. Exhausters fitted with sliding blade or blades will not be acceptable. All parts of the exhauster shall be rigid enough to retain their shape when the machine is working under maximum load conditions. The impellers must be machined all over and must be of such shape and size that they will revolve freely and not touch each other or the casing (cylinder) in which they are placed, but the clearance must be of the least possible amount consistent with successful operation. The shafts must be of steel with the journals ground to size. The journal boxes must be long and rigidly supported by the headplates and placed far enough from the headplates to allow the placing of proper stuffing boxes on the shafts. The shafts must be connected by two pairs of wide-faced steel gears, cut from the solid and securely fastened to the shafts. The gears shall run in suitable oil-tight gear boxes that shall be fitted with adequate and suitable means for lubrication. The displacement type of exhaustion may be used for either high or low-vacuum system. Centrifugal fan type. The centrifugal fan exhauster to be so proportioned and constructed as to handle the volume of air re- 328 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS quired at the specified vacuum with the least possible loss. The housing shall be of aluminum or cast iron, made in sections. The housing must be air tight. The fan wheels to be constructed of aluminum or steel or other metal, properly reinforced, and, if cast, must include hub and arms complete in one piece. If the fan wheels are built up, they must be strongly riveted to cast-iron, steel, or brass hubs or spiders. The fan wheels are to be secured to shaft with a feather and set screws. The shaft of fan exhauster shall be vertical and the wheels so mounted that their weight will equalize or partly equalize the end thrust, or may be horizontal and end thrust taken care of with ball-bearing thrust rings. The journal boxes for all of the above-named types of exhausters shall be of the design best adapted for the purpose and must be fitted with first-class approved continuous lubricating devices, either sight feed, ring oiler, or any other kind best suited for the work or design of apparatus used. Reciprocating piston exhauster shall be provided with the neces- sary devices for the removal of the heat generated by friction and compression, that shall prevent the temperature of cylinders or eduction chambers rising more than 100° F. above the surrounding atmosphere after two hours' continuous operation under full-load conditions. The rotary type of exhaust must be provided with the necessary water connections to properly seal and cool the pump. Speed. Reciprocating exhauster with poppet valves shall oper- ate at an average piston speed not exceeding 200 feet per minute, with rotary valves not exceeding 300 feet per minute. Rotary exhausters shall not exceed a peripheral speed of 1100 feet per minute at tips of impeller. Centrifugal fans sha^U not exceed peripheral velocity of 15,000 feet per minute when running under specified full-load conditions. Base plate, foundation, etc. Provide suitable base plate to rigidly support the exhauster and its motor as a unit, which shall be large enough to catch all drip of water or oil. Provide a raised margin and pads for feet of exhauster frame, motor and anchor bolts, high enough to prevent any drip from getting into the foundation or on the floor. VACUUM CLEANING SYSTEMS 329 Provide suitable foundation of brick or concrete, to which the base plate shall be firmly anchored. The foundation shall be built on top of the cement floor of the basement, which is not to be cut, but shall be picked to afford proper bond for the foundation. Construct the foundation of such a height as to bring the work- ing parts of the machine at the most convenient level for operat- ing purposes. Exposed parts of the foundation to be faced with best grade white enameled brick. If the base plate does not cover the foundation the exposed top surface is to be finished with enameled brick, using bull-nose brick on all edges and corners. Drive. The exhauster shall be driven by an electric motor, which may be direct connected to the exhauster shaft or be oper- ated with a metal-link belt of the noiseless type, or by cut gearing. Chain and gearing is to be of ample size and strength for their work and must run without undue noise or wear. Means shall be provided to take up the slack of the chain belt. Furnish and place a suitable metal guard over belt and sprocket wheels that shall prevent oil being splashed outside of the base plate and prevent clothing being caught. If the exhauster is operated through cut gearing the gears must be inclosed in an oil and dust-proof case, which shall be fitted with means for copious and continuous lubrication of same. Finish. The air exhauster and motor and the base plate shall be finished in a first-class manner, filled, rubbed down, and painted at least one coat at the shop, and after installation shall receive two more coats, finishing tint to be as directed. Electric motor. Motor to be of such size that when operating under test conditions same will not be under less than three-fourths nor more than full-load condition. Motor to be of standard make, approved by the Supervising Architect. Motor to be wound, for 220 volts direct current. Motor armature to be of tooth-core construction, with windings thoroughly insulated and securely fastened in place, and must be balanced both mechanically and electrically. Commutator segments to be of drop-forged copper of high con- ductivity, well insulated with mica of even thickness and of such texture as will give uniform wear of copper and mica, and shall run free from sparking or flashing at the brushes. 330 MECHANICAL EQUIPMENT OF FEDEKAL BUILDINGS Commutator to be free from all defects and have ample bearing surfaces and radial depth as provision for wear. Brushes to be of carbon mounted on common rocker arm and to have cross-sectional area of not less than 1 square inch for each 40 amperes of current at full load. Rocker may be omitted in event interpolar motor is used. Brush holders to be of a design to prevent chattering, with in- dividual adjustment in tension for each brush by means of a spring. Bearings to be of approved self -oiling type. Bidders are required to state in their proposal the rated horse- power and speed of motor. Insulation resistance. There shall be an insulation resistance between the motor frame and the field coils, armature windings, and brush holders, and between shunt and series field coils of not less than 1 megohm. Motor must be capable of standing a break-down test of 1500 volts alternating current for one minute. Efficiency. The efficiencies of motor furnished must not be less than — One-half load, 83 per cent. Full load, 88 per cent. Heating. The maximum rise in temperature of any part of the motor after a continuous run at full-rated load for a period of three hours shall not exceed 90° F. above the surrounding atmosphere. Shop tests and inspection. The insulation, heating, and efficien- cies of the motor shall be determined by actual tests at the shops where the motor is constructed under conditions specified. The contractor shall give 10 days' notice direct to the Super- vising Architect of his readiness for the shop tests of the motor. The department reserves the right to waive shop tests or in- spections of such portions as may in the opinion of the Super- vising Architect be expedient, it being understood that such por- tions not fully waived shall be exacted after the installation of the apparatus. The Supervising Architect reserves the right to waive the shop test in the presence of a representative of this office and in lieu thereof to require the contractor to submit certified test sheets of motor in duplicate. VACUUM CLEANING SYSTEMS 331 Tablet. Furnish and place where indicated a marble tablet not less than IJ inches thick, supported by a substantial angle-bar frame so placed that there will be a space of not less than 1 foot 4 inches behind the tablet. Mount on this tablet one 75-ampere, double-pole, single-break knife switch; one double-pole circuit breaker, with auxiliary car- bon break and overload release, with range from 25 to 60 amperes; and one starting rheostat, with no-voltage release, of proper ca- pacity to control the motor. The rheostat and all of the con- nections shall be on the back of the tablet. The space between the tablet and wall shall be inclosed with a removable diamond-mesh grille of No. 10 iron wire in channel frame. All connections between the tablet and motor are to be made by this contractor. Two No. 3 feeders are now in place and terminate near the new switch tablet which is to be furnished by this contractor. If these feeders are not of sufficient length to reach the new tablet, they must be spliced to new feeders, the splice being made in a junction box. All wires are to run in standard steel conduit, except those that are so short as to be self-supporting, and these are to be cord wrapped or otherwise protected. No wire smaller than No. 12 to be used. All material and workmanship to be strictly first class. Elec- trical work must show an insulation resistance of at least 1 meg- ohm, and to be in strict accordance with the latest edition of the "National Electrical Code." Automatic control. Suitable means shall be provided in con- nection with the motor of reciprocating or rotary exhausters that will maintain the vacuum in the separators within the limit of the machine at point found to be most desirable, irrespective of the number of sweepers in operation. This controller may consist of an automatic device, mounted on the tablet hereinbefore specified, to change speed of motor con- trolled by the variations of the vacuum in the system. If this method of regulation is used, the motor shall be provided with special windings that will permit a speed variation of from one- third full speed to full speed by variation of shunt field only, without undue sparking at the brushes. 332 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS In lieu of above method of control suitable means may be pro- vided in the exhauster, or as an attachment thereto, which will automatically throw the exhauster out of action by admitting atmospheric pressure to the exhauster only, but not to the system; or that shall cause suction from the system to cease whenever the vacuum in the separators rises above the point considered desir- able, and throw the exhauster into action when the vacuum falls below the established lower limit. Drawings. Contractor will be required to submit for approval, after award of contract, drawings in triplicate showing exhauster, motor, separators, connections, and type of control, in detail. Said drawings must be approved by the Supervising Architect before any of the work is installed. Vacuum breaker. In addition to the controlling devices above specified, if reciprocating or rotary exhauster is used, there shall be placed in the suction pipe to the exhauster an approved positive- acting vacuum breaker having opening equivalent to the area of 1-inch diameter pipe and set to open at 12 inches for the high vacuum system. If centrifugal fan-type exhauster is used, it must be designed so that the maximum vacuum shall not exceed 6 inches of mercury and no vacuum control or vacuum breaker will be required. Dust separators. Furnish and place at some convenient point between the vacuum mains and the exhauster one dry separator having a volume of not less than 12 cubic feet for a high or 18 cubic feet for a low-vacuum system. If a displacement type of exhauster is installed, there shall be furnished an additional separator to be placed between the first separator and the exhauster cylinder, which may be either wet or dry, as desired, and may be contained in the base of the machine or consist of a separate tank. If centrifugal type of exhauster is installed, but one separator, and that a dry separator, will be required. Separator tanks shall be constructed with steel shells, with either cast-iron or steel heads, and be fitted with suitable bases or floor stands for support. The interior arrangements of the dry separator first receiving the dust shall be such that no part of same will receive the direct im- pact of the dust. No cloth bags nor metal screens will be per- VACUUM CLEANING SYSTEMS 333 mitted in this separator. It must be so constructed that it shall intercept not less than 95 per cent of the dust entering same. If two dry separators are used, the second separator must be arranged so that none of its apphauces are liable to be ruptured by air currents or of being drawn into the piping or exhauster, and the arrangment of same must be such that the separator can be easily cleaned without dismantling same. Wet separators, whether separate from or integral with the base of the machine, must be provided with an attachment which will positively mix the air and water, thoroughly break up all bubbles, separate the water from the air, and prevent any water entering the exhauster cylinder. If wet and dry separators are used in combination, suitable means must be provided to automatically equalize the vacuum between them upon the shutting down of the exhauster. The separators must be provided with suitable openings for access to the interior for inspection and cleaning, and the interior arrangement of the separators must be such that they may be readily cleaned without dismantling. All parts of the wet separator tank not constructed of non- corrosive-metal must be thoroughly tinned or galvanized both inside and outside. The interior of the wet separator formed in base of exhauster shall be painted with at least two coats of asphalt varnish or other paint suitable to prevent the corrosion of the same. Separators must be provided with all necessary valves or other attachments for successful operation, including a sight glass for the wet separator, through which the interior of same may be ob- served, and a 30-inch iron case mercury column attached to the dry separator first receiving the dust. Wet separator shall be connected to the water-supply main and to sewer, which pipes are in place in the machine room, as directed. A running trap with clean out shall be installed in the waste hne between separator and sewer. Piping. The vacuum mains shall be installed as indicated and noted on drawings. The pipe size indicated on the drawings, inclosed in circles, are to be followed for a high-vacuum system and the pipe size inclosed in squares are to be followed for a low-vacuum system. No in- crease or decrease in these pipe sizes will be allowed. 334 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS Pipes. All pipe conveying air is to be standard, black, wrought iron, or mild steel, screw-jointed pipe, and is to be smooth inside, free from dents, kinks, fins, or burrs. Ends of pipe to be reamed to the full inside diameter and beveled. Bent pipe to be used in mains where necessary. Care must be taken in erecting pipe to maintain as nearly as possible a smooth, uniform bore through all pipe and fittings. Waste and water pipe, in connection with wet separator and jacket (if used), except waste pipe below basement floor to be standard galvanized wrought iron or steel, screw-jointed pipe, free from burrs. Waste pipe below the basement floor is to be best grade, "extra heavy" cast-iron pipe, with lead-calked joints. Fittings. All fittings to be tough, gray cast iron, free from blow holes or other defects; smooth castings in all cases. All fittings on vacuum lines must have inside diameter through body of same size as pipe bore, and all fins, burrs or rough places must be removed. Fittings on vacuum lines are to be black or may be galvanized. Where space permits, all tees and elbows, must have a radius at center line of not less than 3 inches. All fittings having less than 3-inch radius must have the thick- ness of metal on sides receiving the impact of the dust increased 50 per cent above standard thickness. A standard cast-iron flange union is to be provided on the connection to each riser near the base. Fittings on water lines to be standard galvanized beaded fittings. Fittings on waste line above basement floor to be galvanized, recessed, screw-jointed drainage fittings, and those below base- ment floor to be "extra heavy" cast iron with hub joints. Horizontal overhead pipes to be supported with substantial pipe hangers spaced not more than 10 feet apart. Where exposed pipes pass through walls or floors of finished rooms, they must be fitted with cast-iron, nickel-plated plates. Clean-out plugs. Brass screw-jointed clean-out plugs are to be provided in lines at all turns where indicated on the drawing. The clean-out plugs to be 2-inch dia:meter, except in the l§-inch lines, where clean-outs are to be same diameter as the line. VACXJUM CLEANING SYSTEMS 335 Exhaust connection. Exhaust pipe from the exhauster is to be run up to the basement ceiliug and along same into the vent shaft and up same to attic and through the roof, as indicated. The opening in roof is to be flashed with 6-pound sheet lead and pro- vided with counterflashing. The exhaust pipe is to be fitted with an approved firstclass exhaust muffler not less than 12 inches in diameter and 6 inches high, closely riveted and constructed of galvanized iron not less than |-inch thick, and in event an exhauster requiring lubrica- tion is furnished this muffler is also to be arranged so that it will also be an efficient oil separator. Drip connection to be arranged at bottom of muffler. Sweeper outlets. The following number of outlets are to be provided: Basement, three; first story, six; second story, three; third story, three; fourth story, three; fifth story, three; sixth story, three; attic, three. The sweeper outlets may be fitted with hinged screw covers or caps with rubber gaskets. If screw cover is used, same is to be provided with a safety link, brass, nickel-plated chain. If hinged type of outlet is used, same is to be arranged to be self-closing when hose is removed. Outlets coming through finished walls or partitions are to be fiush pattern. Outlets on risers run exposed agaiiist walls are to be set close up against bead of fittings. If contractor desires to use other form of connection than above described, which is equally satisfactory, same must be submitted to the Supervising Architect for approval after award of the contract. Tool cases. Furnish eight approved hardwood cabinet- finished cases for cleaning tools. Each case to be made as light as possible and of convenient form for carrying by hand and pro- vided with a complete set of cleaning tools, each securely held in its proper place and fitted with lock and key, clamps, and con- veniently arranged handles. In this specification the word "renovator" is used to mean that portion of the tool which is in contact with the surfaces cleaned; the word "stem," that portion connecting the renovator 336 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS and handle, and the word "handle," that portion held in the hand and to which the hose is attached; the word "cleaner" is used to mean a complete cleaning tool. Cleaning tools, etc. The following cleaning tools are to be furnished for each case : One renovator not less than 12 inches nor more than 15 inches wide, for cleaning carpets. One renovator not less than 12 inches nor more than 15 inches wide, for cleaning bare floors. One brush renovator not less than 12 inches nor more than 15 inches wide, for cleaning walls. One dusting brush renovator not less than 4 inches nor more than 6 inches in diameter, for cleaning relief work. One brush renovator suitable for stair cleaning. One upholstery cleaner not less than 4 inches nor more than 6 inches wide for cleaning upholstery furniture. One corner and crevice cleaner. One short stem about 1 foot long. One long stem about 5 feet long. One extension tube about 5 feet long. One 45° handle for floor cleaning. One straight handle for woodwork and wall cleaning. Both kinds of handles to be provided with couplings for hose and stems to be provided with hand-operated full-area roundway valves. The cut-off valve must be easily operated and be indi- cating and when closed be practically air tight. All movable parts that are in contact must be arranged so as to be protected from dust and from wear from this cause. The renovators for carpets, bare floors, walls, and relief work to be arranged with adjustable swivel joint, so that same can be set at an angle with stem from 45° for regular use to an angle of about 80° for use under or back of furniture and other similar places. This movable joint can be made so that it can be easily adjusted and firmly set and held in place, or so arranged that lips of cleaning tool will always remain in contact with surface cleaned, and constructed so that fitted surfaces are not exposed to dust, and the air current when deflected to impinge only upon surfaces which are of heavy metal and where such wear as occurs will not affect the operation and handling of the tool. VACUUM CLEANING SYSTEMS 337 In lieu of the above adjustable joint in the renovators them- selves special couplings, one for each stem, may be furnished in addition to the straight couplings, which can be used in connection with the renovator mentioned so as to bring the latter to the 80° angle required. All renovators, stems, and handles are to be as light as is con- sistent with strength and ability to withstand cutting action of dust. All renovators, except round and stair brushes, are to have slots of the following widths: For high-vacuum system, J inch wide. For low-vacuum system, | inch wide. A variation not exceeding 15 per cent in width of slots as given above will be allowed on carpet renovators. A variation of 25 per cent increase will be allowed on brush renovators. If renovators, with air-intake slots, or other form of vacuum reducer, or short-circuiting opening, are used, the area of the main slot may be increased 20 per cent. The area of intake opening or slot is not to exceed 10 per cent of the net area of main slot. The lips of carpet renovators and upholstery cleaner to be of such proportions and form as will prevent injury to the fabric, and such width as will reduce to a minimima the sticking of renovator face to the material being cleaned. An approved |-inch diameter finished-brass, nickel-plated, positive-acting vacuiun breaker, with an adjustable brass spring, inclosed within a removable cap, is to be provided in the handle of a high-vacuum system, and must be connected to handle by |-inch diameter standard screw-pipe connection so as to be removable for cleaning, etc. In event air-intakes slots or other vacuum-reducing devices are used in the high-vacuum system, the vacuum breakers in the tool handles may be omitted. In event centrifugal exhauster which will not produce more than 6 inches of vacuum is used, the vacuum breakers in tool handles may be omitted. Handles to be cast metal or combination of cast metal and tubing. Stems to be not less than 1 inch outside diameter for high- 338 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS vacuum system and li-inch outside diameter for low-vacuum system. Air passages in handles and swivels to be same diameter as inside of stem. The handles are to have long-radius curves, and connections are to be made without shoulders or projections in the bore against which dust can strike. Parts of handles receiving dust at change of direction are to have ample metal to allow for cutting effect of dust. Stems to be drawn-steel or brass tubing, not less than No. 21 United States standard gauge thick if steel and not less than No. 16 Brown and Sharpe gauge thick if brass. Carpet renovators to be made preferably of cast iron, as light as possible, or may be made of cast brass with iron wearing face. All brushes to be of substantial construction, with best quality bristles set in close rows and as thick as possible, skirted with rubber, leather, or chamois skin so that all air entering renovator will pass over surface being cleaned. All renovators and brushes must be provided with proper rub- ber or other approved buffers to prevent marring the woodwork. Upholstery cleaners are to have inlet slots or openings of such size and form as to absolutely prevent drawing in loose covering of furniture. Upholstery and corner cleaners are not to be arranged for use with stems and handles, but are to have their own handles perma- nently attached, and be provided with hose couplings, and with- out valves and vacuum breakers. All metal parts of renovators, stems, and handles are to be fin- ished, and all except aluminum parts nickel plated. Hose racks. Furnish and properly secure in place, where directed, one hose rack in basement, first, second, third, fourth, fifth, sixth, and attic stories (eight racks in all). The racks to be constructed of cast iron, galvanized or enamel finish, and each rack to be suitable for holding 75 feet of hose of required size. Hose. There must be furnished with each hose rack 75 feet of non-collapsible hose in three 25-foot lengths. Hose to be not less than 1 inch inside diameter for high-vacuum system and not less than l|-inch inside diameter for low-vacuum system, and must be smooth inside and outside. VACUUM CLEANING SYSTEMS 339 The hose to be best quality rubber hose, reinforced in best man- ner to absolutely prevent collapse at highest vacuum obtainable with the exhauster furnished and to prevent collapse if stepped on. Weight of hose to be not over 16 ounces per Hnear foot. Couplings for hose to be either screw, slip, or bayonet-lock type, with smooth bore of practically same diameter as inside of hose. The couplings to have least possible projection outside of hose dimensions and be well rounded, so as not to injure floors, doors, furniture, etc. Screw couplings to have ground joint; bayonet joints may have packing washer, and slip joints to have permanent steel T pieces on ends of hose and brass slip coupler. All ends of hose couphngs to have outside ferrules securely fastened in place. Simple conical slip joints slipped into ends of hose without fer- rules will not be acceptable. Samples. The successful bidder, after award of contract, if required by the Supervising Architect, must submit to the Super- vising Architect for approval one cleaning-tool case supplied with full set of cleaning tools, one of each kind of outlet, and one piece of vacuum hose, 12 inches long, supplied with coupling at one end. Tests. The contractor is to make tests hereinafter described in the presence of the Department's representative and must fur- nish all the labor necessary to make said tests. Operation test. After the complete installation of the appa- ratus, a capacity test of the exhauster shall be made. Four outlets shall be selected by the Department's representative, but not more than two on any one riser, and to each shall be at- tached 100 feet of hose, of size required by the system, with end open. To be acceptable, this test must show that the exhauster shall maintain the specified vacuum when running at or under the specified speed, and the power consumed shall not exceed 14 kilowatts. To test the tightness of the system and the effectiveness of the vacuum control, the exhauster shall be run with all outlets closed, and the power consumed shall not exceed 50 per cent of that at full load. Test of cleaning tools. The plant shall be operated by the contractor in presence of the Department's representative, and a 340 MECHANICAL EQUIPMENT OP FEDERAL BUILDINGS test made of each kind of cleaning tool furnished. The tool shall be attached to a 50-foot length of hose attached to an out- let selected by Department's representative, and under normal working conditions each tool must satisfactorily perform the work for which it was designed. Dust and surfaces to be cleaned shall be furnished by the contractor. Test of separators. At each of four points, near four outlets selected by the Department's representative (not more than two outlets on any one riser), the contractor shall furnish and spread on the floor, evenly covering an area of approximately 200 square feet for the four outlets, or 50 square feet for each outlet, a mix- ture of 24 pounds of dry, sharp sand that will pass a 50-mesh screen, 12 pounds of fine wheat flour, and 4 pounds of finely pulverized charcoal. Fifty feet of hose of size required by the system used shall be attached to each of the four outlets, and the surface or surfaces prepared for cleaning shall be cleaned simultaneously by operators provided by the contractor, until all of the sand, flour, and char- coal has been taken up, when the exhauster shall be stopped and the dirt removed from the dry separator and spread on the floor again, and the operation of cleaning repeated until the mixture has been handled by the apparatus four times. If, after thor- oughly flushing the system, at completion of the above run, any dust or mud is found in the cylinder, ports, or valves chambers of the displacement exhauster, or if less than 95 per cent of the dirt removed is found in the dry separator of the centrifugal ex- hauster, it shall be deemed sufficient ground for the rejection of the separators. Painting. After the completion of the specified tests, all ex- posed galvanized-iron or tinned work in connection with this apparatus, not specified to be otherwise finished, shall be primed with paint suitable for galvanized or tinned surfaces, and then given two additional coats. Machinery shall be painted as already specified, and all other work shall be given finishing tints as selected or approved by the custodian. Black iron shall be primed with a coat of red lead and hnseed oil. Portable apparatus. For Federal buildings containing less than 50,000 square feet of floor area, a portable vacuum cleaner com- VACUUM CLEANING SYSTEMS 341 plying with the following specifications is supplied at a cost of about $125.00. Vacuum producer shall be of rugged construction with well- proportioned parts. It must be capable of displacing not less than 50 cubic feet of free air per minute at the end of not less than 15 feet of cleaning hose, and must produce a vacuum when outlet is closed of not less than 22 inches of water. Motor shall be of standard make, of ample power to drive vacuum producer. The maximum power consumption when operating either with open hose or with renovator on carpet shall not exceed 360 watts. The motor must be fitted with a suitable device to permit same to be started with a 10-ampere fuse in the circuit. Dust separator shall be constructed of metal and be so ar- ranged that it can be easily cleaned. The capacity and arrange- ment of dust separator shall be such that at least one peck of dust may be picked up and the machine still do effective work and the separator intercept all dust and dirt without cleaning the dust separator. The vacuum producer, motor, and dust separator shall be mounted as a unit. No wood shall be used in any part of this unit. The combined unit shall be mounted on wheels or casters and fitted with suitable handles, and shall not weigh more than 80 poimds. The following equipment to be furnished with the cleaner: 25 feet flexible reinforced new code No. 14 double conductor with Edison screw attachment plug. Not less than 15 feet of reinforced rubber-lined cleaning hose not less than IJ-inch inside diameter. One brass or aluminum tubular handle not less than 4 feet long. One extension tube 5 feet long. One carpet renovator with cleaning slot not less than 8 inches long by f inch wide, with cast-iron wearing face. One hard-wood floor tool. One floor brush. These may be arranged to be attached to carpet renovator if desired, and shall have cleaning slots with areas equal to or greater than that of carpet renovator. 342 MECHANICAL EQUIPMENT- OF FEDERAL BUILDINGS One wall brush not less than 5-inch diameter. One upholstery tool with not less than 3-inch cleaning slot. One corner cleaner. One blowing nozzle. All renovators to be made of aluminum or of brass, the former being preferred, and all parts except aluminum to be nickel- plated. The foregoing specification for portable cleaning apparatus was used by the Department until October, 1911, at which time the Bureau of Standards undertook the testing of these devices for the Treasury Department with a view to selecting the best ap- paratus. When the tests are completed a new specification will be issued. CHAPTER XII OPERATING DATA There are few engineers who have jurisdiction over the design, construction, and operation of mechanical and electrical equip- ment of buildings, and this lack of intimate contact with the actual operating side of plants is a severe handicap to those who are not so fortunate, especially when they are called in to defend their recommendations for installation of isolated power plants for buildings or industrial establishments, for the reason that their information on the subject of plant operation is purely theoretical and they have no bona fide records of their own to back up their calculations. It is also true that only a few operating engineers are pro- vided with means for accurately determining the coal and cur- rent consumption rates of the apparatus under their charge. The great majority are densely ignorant regarding the distribu- tion of the steam generated in the boilers to the different portions of the equipment, i.e., the electric generating plant, the heating apparatus, etc.; and consequently they have no records to produce and have only a hazy idea of the situation when confronted by a good contract agent from the central station in an argument for or against shutting down the electric generating plans under their charge. The office of the Supervising Architect is particularly fortunate in that it has exclusive jurisdiction over the design, construction, repair, and operation of the various buildings that it erects, and also has exclusive jurisdiction over the personnel of the operating forces, as well as over the purchase and use of all the supplies, etc., required for the various buildings. That this situation is correct and logical is borne out by the extraordinary economies that have been effected since steps were taken to place all these responsibiUties under one technical bureau instead of entrusting them to several related or nonrelated bureaus, as was previously the custom in the Treasury Department, and as is still the custom 343 In order to obtain data upon the operation of Federal buildings under control of the Treasury Department, records are kept in some detail, especially in the larger buildings, and these records and data are studied, compared, and used as guides in the design of new projects. All of the important buildings containing electric generating plants are equipped with coal scales, steam flow meters, water flow meters, CO2 machines, etc., and the chief operating engineers axe provided with daily report blanks covering the coal consump- tion, ash removal, steam consumption of electric generating plants, etc. A few samples of the actual reports follow: OPERATING DATA 345 C*^ 2; H o TME RCHIT 5-14 50 O rt CI -a o d ft ft EO m d d CD a; u o o u a O (N (M CO O +=" -^=» bJD o3 j2 ^ -^^ S -t> -IJ H^ P-l O O c^ ;? & o o3 bO ^ b p< ^ bO a 5 m ^ bjo o3 .S ft 73 e! 3 bB 3 M ft f^ ft--* t3 ■« w m & XI a o S oj 1 — I _ t, h t-i ^ Q) (D bfl > > O <1 -Jj O rt m m m OT J3 ,Q ^ J2 O 1^ o o ^5 "=> CD CX> CO CI .s a i " ft o ,3. o3 ■^ 3 3 m > =3 .3 3 I— I '^ ■ -I +=> X o3 <: W SK o bO 3 bC .3 ■3 2 ° ca 3 > ■-< a a 03 3 3 ^" o •a a -^ ^^ ^ OPERATING DATA 347 IN to g 00 to o -* • . to t^ lO T-H • • CO U5 TO to o TO CM §§ ^ "^ -^ : : (M .-1 I— ( i -l CO o T}1 1— 1 CM O cn CO 00 3 3 Coo o o o a, n, p,^' g "H ll_ II II II II ll_ c >>'2 c~ a cT « -a o,Cooooc H.H 3;=l;i-,:=l~ s J2 .° iS c3 53 03 O p. a Q. P< 0< P< m m to 02 CO CO -^^ -t^ -fJ -*J +3 ^J fi d a c o c a; > 3 >^ S ^ m a a Q Op: o o o o -^^ +2 +3 -(J en CO CO CO O O O O o o o o 3 o3 o3 (D QJ 350 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS e© »5 g S -3 a o a _C 'C 3 13 o .ri s w w ^" > ^ K K^ I--* ft a p. s s a ■ ra c3 o3 ' s d fi ■ O 00 -H 00 CD CO o3 03 o3 •< ^ cS CO o I— I Tfl T3 d OS ■ T3 a (2. a a bo o3 o3 O o bb.'^ a : c3 . ,cl > > <: & g 03 ^ > -G O .«> 00 O -a c -a o3 ^ 2 ho c +^ CD c3 bO ^ C a '^ CI. W O t3 O) C<1 tH CO f- 1^ ;-: "^ K^ « 03 c3 " ^ ]M I-] hC -D O fri (B w M m mm t» -Q -O ^ ^ .i3 ^ ^ T3 Di j5 fi. CD O O CO 00 (M -S a hC d Si hfl d o3 O O S bc . =^ a g g t- CO a3 :=> G^ -M o o QJ -^ faO bjD CD C QJ hO O <1 Q >5 .^3 ° ^ 03 C >? ;> •-, ffl b^ 0^ 2 ~ a o3 o3 OPEHAMNG DATA 351 o ^ O CO I— 1 lO o CO o CO r— 1 00 CO CO t- o o CO t^ o CO 03 y~t CO 00 I> T-H ^ 00 (r ■* e@ >— 1 o o f^ -y o o "3 rt H a 3 cS ^ ^ II O o 11^ a '-3 -a O 3 S HO g 'CL, o3 O o3 C3 O b£ Ph bfl ho ft 'So d 3 o o o o „ ._ OT W W ^5^0000 fe: O O O O 352 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS O O -*J -4-3 +3 ^^^ 354 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS by careful operation and close supervision it has been possible to compete with the large central stations except where certain influ- ences have made the labor item outrageously excessive. In the plants which have been shut down in recent years the cause of the change has been that the engineering employees have over- reached themselves in the matter of hours of labor, rates of pay, etc., coupled with the fact that the plants themselves were old and generally low in all-around efficiency. The central stations are each year making lower rates and ap- proaching the point where the cost of purchasing current wiU be equal to or less than the cost of operating the isolated plants, and it behooves those interested in the maintenance of an isolated plant to keep up to date and effect every possible economy. The following table is introduced to give an idea of the annual consumption of electricity for power and light in certain Federal buildings. It is interesting to compare the current consumption in Federal buildings (which are 24-hour buildings), with commercial buildings as reported by the Wisconsin Public Service Com- mission : CLASS OF BUILDING K.W H. PER ANNUM PER K W. OF FULL CONNECTED LOAD ^LIGHTING only) Churches Farms Laundries Lodge halls Schools Residences Theatres Offices Livery stables Stores Hotels Signs Bowling alleys Depots Saloons Industrial establishments Restaurants 101 183 185 194 236 239 367 400 402 471 505 551 809 937 955 1069 2209 OPERATING DATA 355 FEDERAL BUILDINGS K.W.H. PER ANNUM PER K.W. FULL CON- NECTED LIGHTING LOAD K.W.H. PEH AMNTJM PER H.P. OF FULL CONNECTED POWER LOAD Small buildings up to 250,000 cubic 1200 1200 1200 3300 350 250,000 to 500,000 cubic contents... . 500,000 to 1,000,000 cubic contents.. 1,000,000 to 10,000,000 cubic con- (all stamp cancel- ling machines) 160 300 400 The foregoing data are extremely valuable in estimating the operating characteristics of a new building which is being designed, at which time it is essential that the maximum demand, full con- nected load, annual K.W.H. consumption, heating requirements, labor force, etc., be accurately determined, in order that an in- telhgent comparison may be made with the rates quoted by the local electric company to see whether the installation of an isolated electric light plant would be justified. It may be stated roughly that the full connected power and lighting load will not exceed If watts per square foot of the en- tire building; that the maximum demand will not exceed 45 per cent of the full connected lighting and power load; and that the electric current consumption per annum for power and hght will not exceed 2 K.W.H. per square foot of floor area in a modern building with ample and well-placed windows. Generally speaking, an isolated plant begins to be feasible in a. Federal building where the full connected load is not less than 150' K.W. or more and where the annual current consumption is not less than 200,000 K.W.H. or more per annum and the cost of cur- rent from the central station does not exceed 4 cents per K.W.H. In commercial buildings, an authority states that in and around New York City where the cost of purchased current will ap- proximate 5 cents per K.W.H. an isolated plant should be given consideration when the annual current consumption is 60,000 K.W.H. or more. A leading mechanical and electrical engineer of New York City, has stated that in a given building where there are two or more electric elevators and 1000 or more lighting sockets (50-watt rat- 356 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS ing) an isolated plant becomes a possibility when the cost of pur- chased current is 5 cents per K.W.H. or greater. The accompanying table represents the operating characteris- tics of a large number of Federal buildings in Washington, D. C. These data were gathered in connection with a report made by the writer for the establishment of a central heating, power, and lighting plant to serve the buildings noted. Based on the re- port an appropriation of approximately $1,500,000 was made by Congress to carry out the project. Certain of the older Federal buildings in the larger cities were not originally provided with isolated power plants, and a few years ago the writer detailed an able engineer to visit these buildings and determine on the ground, after full conference with the local public service officials, whether the installation of isolated plants would be justified. In one notable instance the situation was especially favorable, and the engineer reported as follows : The following data were obtained from records and conditions at the building to form a basis of data in considering the installation of a plant: Total wattage of lamps is 377,000. Total K.W. rating of motors is 700. Total floor area is 660,000 square feet. Preseat coal and current consumption. July August September October November December January February March April May June Summer months Winter months Totals ;.. CUHHENT IN K.W.H. 98,840 100,340 105,860 109,420 106,430 116,590 637,480 Wi nter 117,240 115,590 127,080 123,970 125,800 125,800 735,480 637,480 735,480 1,372,960 TONS OP COAL Summer 323.790 309.350 319.970 406.479 316.392 269.649 Winter 417.835 538.427 537.414 837.000 694.720 670.715 1,945.630 3,696.111 1,945.630 3,696.111 5,641.740 OPEBATING DATA 357 Current cost per annum, $26,113.35. 26,113.35 ^j^^^ =$0,019 per K.W.H. Highest maximum demand for any month 340 K.W. Lowest maximum demand for any month 225 K.W. Average hours less than 100 K.W. demand 3,000 Average hours between 100 and 220 K.W 2,400 Average hours between 200 and 300 K.W 2,800 Average hours between 300 and 400 K.W 560 Under the above operating conditions the installation of two 200 K.W. and two 100 K.W. electric generating units would give the most flexible plant and allow ample reserve. Ample boiler capacity is now installed in the building, and it is be- lieved that better efficiency will be obtained during the summer months with the additional load required by the electric generating plant. Estimated cost of plant: Engines and generators $30,000 Piping 2,500 Switchboard changes 1,000 Incidentals 500 Total ■ S34,000^ " The plant was installed for $42,000. To be safe and allow 50 pounds of steam per K.W.H. and a factor of evaporation of SJ pounds of water per pound of coal, we would have 6 pounds of coal per K.W.H., and charging all coal used in six months of the year, and 20 per cent during six months of the seven that exhaust steam is utilized for heating: 637,480 X 6 = 3,824,880 lbs. of coal 735,480 X 6 X .2 = 882,576 lbs. of coal 4,707,456 lbs. of coal=2.100 tons. 2,000 tons X 3.15 = $6,615.00. ASH REMOVAL Ash removal for 5645 tons of coal costs now $622.41. Ash removal for 2100 tons of coal will cost $231.00. Water used by the plant will be: 4,707,456 pounds of coal X 8| = 39,228,800 pounds of water = 627,660 cubic feet X 52.5 cents (per 1000 cubic feet) = $329.57 per annum. 358 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS Present cost With an electric generating plant 1 chief engineer $2,200.00 1 chief engineer $2,200.00 1 assistant chief engineer 1,800.00 1 assistant chief engineer 1,800.00 3 assistant engineers 3,600.00 3 assistant engineers. .. . 3,600.00 2 engineer helpers 2,000 . 00 4 engineer helpers 4,000 . 00 3 oilers 2,520.00 4 oilers 3,360.00 7 firemen 6,387.50 8 firemen 7,300.00 3 firemen helpers 2,190.00 3 firemen helpers 2,190.00 2 firemen helpers for 7 2 firemen helpers for 7 months 852.00 months 852.00 $21,549.50 $25,302.00 OIL AND WASTE Estimated for electric generating plant $300.00 REPAIKS $30,000 at li per cent $450.00 INTEREST AND DEPRECIATION 30,000 at 10 per cent $3,000.00 Total cost to operate the proposed electric generating plant: Coal $6,615.00 Ashes 231 .00 Water 329.57 Labor 3,752.50 Oil and waste 300.00 Repairs 450.00 Interest and depreciation 3,000.00 Total annual cost $14,678.07 Cost of current during present year $26,113.35 Estimated cost of current with electric generating plant 14,678 .07 Estimated annual saving $11,435.28 I recommend the installation of an electric generating plant in this building at an early date, as same will pay for itself in three years. Respectfully, The plant recommenced by the engineer was installed after a long controversy, and the writer takes pleasure in stating that after twelve months operation the annual saving to the Government by OPERATING DATA 359 the installation of this plant has amounted to $15,984.78, and it is performing its work in a satisfactory manner. When a Federal building is erected in a city where a district heating company has steam or hot water mains in the vicinity, the heating apparatus is designed so that the building may be oper- ated either by its own boilers (which are always installed) or by the heating medium purchased from the district heating company. Upon receipt of the company's proposal for supply of the heating medium, which in the case of steam is nearly always based on a sliding scale so arranged that the price per thousand pounds de- creases as the amount used per month increases, it is necessary for the ofhce to determine accurately whether it will be more economical to generate its own steam, or to purchase the steam from the company. The following method is used: The actual amount in square feet of direct radiation is taken off the plans, to which is added any fan blast surface and any gravity indirect surface. To reduce to equivalent direct radiation the amount of blast coil surface in square feet is multiplied by 3, and the gravity indirect is multiplied by IJ. The equivalent direct radiation is then assumed to condense during the 212 days of the average heating seasons 500 pounds of steam per square foot. To apply the sliding scale the total steam per season is apportioned as follows : October 1 to October 31 15 per cent of total November 1 to November 30 15 per cent of total December 1 to December 31 20 per cent of total January 1 to January 31 25 per cent of total February 1 to February 28 15 per cent of total March 1 to March 31 15 per cent of total April 1 to April 30 5 per cent of total .The total cost is thus ascertained if steam be purchased, and it is compared on the following basis with the cost of operating the boilers in the building: The total number of pounds of steam per annum as previously ascertained is divided by 7, which gives the number of pounds of coal per annum used under the boilers. This is reduced to tons and the local cost per ton of coal is applied. To the actual cost of coal is added the cost of ash removal, which is taken roughly as 10 cents per ton of coal, and in the infrequent cases (especially in 360 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS the smaller buildings) where labor can be saved by the purchase of steam the cost of the additional labor is added. The De- partment is usually wilhng to pay $100 or 6ver per annum more for the purchase of steam in order to be relieved of the operation of the boilers, and secure freedom from smoke, dirt, etc. If hot water is the medium the same process is used, by reduc- ing the hot water radiation to a steam equivalent (dividing the hot water radiation by 1.6) to ascertain the amount of coal to be burned and compare it with the flat rate always quoted for hot water radiation by the local companies. South of the Mason and Dixon line the figure 500 above noted will become 450, while in San Francisco, Cal., it will approximate 350 pounds per square foot direct steam radiation. The majority of the buildings are very small, and the mechanical equipment consists of a direct steam or hot-water heating appa- ratus and a gas and electric direct lighting system supplied with either gas or electricity from local companies. In these small buildings the matter of engineering personnel, purchase of sup- plies, fuel, etc., is merely routine. It was the practice of the Department to purchase coal on the B.t.u. basis for all buildings where the cost exceeded $1500 per annum, but this method of purchase has been discontinued except for the large buildings. When coal is purchased under the B.t.u. system the specifica- tions state what kind of coal is desired, and limit the amount of volatile matter and ash which will be permitted. Each bidder offers such coal as he thinks will meet the specifi- cation, and gives in his proposal the following information rela- tive to the coal'he proposes to supply: Number of B.t.u. per pound of dry coal as received. Percentage of ash per pound of dry coal. Cost per ton of coal. As there is always a variation in the ash content of coal offered by the various bidders, it is necessary, in order to reduce all to the same basis, to fix a standard ash content and make an allow- ance for variation from same. The lowest ash content stated by any bidder is made the stand- ard, and all other coal is brought to this basis by adding 2 cents OPERATING DATA 361 per ton to the price quoted for each 1 per cent or fraction thereof the ash content exceeds the arbitrary standard. When all proposals have been brought to the same basis in regard to ash content, the lowest price quoted per 1,000,000 B.t.u. is readily ascertained by the following formula: „ , .,,. T, , 1,000,000 X price per ton of coal Cost per million B.t.u. = ' ,„ — =— — — 2240 X B.t.u. per pound of coal. When the coal purchased under the B.t.u. system is delivered at the building, samples are taken and sent to the Bureau of Mines for analysis, the result of which determines the payment to be made for the coal delivered. If the analysis shows that the contractor has fulfilled his agreement, no more and no less, the contract price is paid; otherwise, corrections above or below the contract price are made for variation in B.t.u. and ash. The correction for B.t.u. is made by the following formula: Delivered B.t.u. X contract price per ton . ., , — — r— = price paid per ton. Contract number of B.t.u. per pound For example: If the contractor stated that his coal contained 14,000 B.t.u. per pound and the price per ton was $3, and the coal dehvered contained 14,300 B.t.u. per pound, he would be paid per ton 14,300X3 14,000 = $3.0643 The price to be paid must be further corrected for any varia- tion in ash content. For all coal, which by analysis contains less ash than that estabUshed in the proposal, a premium of 2 cents per ton for each whole per cent less ash is paid. An increase of 2 per cent in ash over the contract amount is tolerated without deduction, but for any excess a penalty is exacted in accordance with the following table. When local conditions permit the choice of either gas or elec- tricity as the illuminating medium, preference is given to elec- tricity for many practical reasons, such as maintenance, adjust- ments, etc., and also on account of the great amount of heat generated by the gas, which is a decidedly objectionable feature during the summer months. 362 MECHANICAL EQUIPMENT OF FEDERAL BUILDINGS NO DEDUC- TION rOK CENTS PEK TON TO BE DEDUCTED ASH AS ESTAB- LISHED IN i i i 7 12 18 25 :« MAXIMUM LIMITS FOR ASH BELOW Percentages of ash in dry coal per cent 5 7 7-8 8-9 9-10 10-11 11-12 12-13 13-14 12 6 8 9 10 11 8-9 9-10 10-11 11-12 9-10 10-11 11-12 12-13 10-11 11-12 12-13 13-14 11-12 12-13 13-14 14-15 12-13 13-14 13-14 14-15 15-16 16-17 14^15 15-16 16-17 17-18 13 7 14 8 . . 14-15 15-16 14 9 15 10 12 13 12-13 13-14 13-14 14^15 14-15 15-16 15-16 16-17 17-18 17-18 18-19 16 11 16-17 16 12 14 14-15 15-16 16-17 17-18 18-19 19-20 17 13 15 15-16 16-17 17-18 18-19 19-20 20-21 18 14 16 17 16-17 17-18 17-18 18-19 18-19 19-20 20-21 20-21 21-22 21-22 19 15 19-20 19 16 18 18-19 19-20 20-21 21-22 22-23 20 17 19 20 19-20 20-21 20-21 21-22 21-22 22-23 22-23 21 18 22 With combination lighting fixtures designed to give satisfactory illumination using either tungsten lamps or Welsbach gas lamps, the cost of illuminating a building will be about the same for gas and electricicty if gas is selling at $1 per thousand cubic feet and electricity at 10 cents per kilowatt-hour. The theoretical ratio of cost based on equal illumination is approximately 30 to 1 on the basis that 1 watt of electricity will give 10 lumens on an average and gas 300 lumens per cubic foot on an average but actual ex- perience has demonstrated that the true ratio is 10 to 1 under practical operating conditions as found in Federal buildings. Where conditions permit the use of either gas or electricity their relative costs are carefully analyzed in each case, on the assumption that the full connected lighting load of a building will be in service 1200 hours per annum. The following data are used in connection with the gas lighting : Pilot uses Yz cubic foot of gas per hour and burns continuously. Welsbach inverted No. 4 T uses 1.6 cubic feet per hour gives 450 lumens. No. 3 T 21 cubic feet per hour gives 900 lumens. Junior upright about IJ cubic feet per hour give 350 lumens. Inverted No. 20 uses 9 cubic feet per hour gives 2400 lumens. Welsbach inverted No. 1 uses 3|-4 cubic feet per hour gives 400 lumens. Welsbach upright gallery burner uses 4 J cubic feet per hour gives 800 lumens. APPENDIX GENERAL INSTRUCTIONS ISSUED TO DRAFTSMEN BT THE CHIEF MECHANICAL AND ELECTRICAL ENGI- NEER, OFPICB SUPERVISING ARCHITECT The first step taken in the design of the mechanical equipment of a Fed- eral building consists in acting on the survey which is secured by the office and forwarded to the Chief Mechanical and Electrical Engineer for check. As the proper design of the drainage system, gas, and water piping, and electrical service connections to buildings are dependent on a correct sur- vey, great care must be taken in acting on same, and the following are the principal items to be noted: Survey must give location of gas and water mains and sizes thereof. If no gas mains are shown, check survey and state in your note to engineer- in-charge "No gas mains shown." If water mains are not shown, return survey with request that size and location of water main be indicated. In event water or gas mains indicated on survey are smaller than 2-inch diameter (unless the gas is distributed at high pressure) , return survey and request size and location of nearest large gas or water main. Many gas mains are now installed in which gas is under a pressure of several pounds and in consequence they are reduced greatly in size. See that location and sizes of sewers are given, and-direction of flow and rate of fa,ll. If an elevation is given on sewer without a specific state- ment as to what point it refers, request that this information be given, unless there is absolutely no question that sewer can drain a cellar 10 feet deep. In event sewer is shown but no elevation is given, request information relative to elevation of invert. If no sewer is available, and a cesspool or septic tank is not to be used, it will be necessary for the Government to build its own sewer, and you should call special attention to the matter in order that the necessary legal steps may be taken to secure right of way, exclusive jurisdiction, etc. Examine survey for electric light, power, telephone, telegraph and trolley poles, or for underground conduits; if all these points are covered satisfactorily, check survey. If no poles are indicated on survey and none appear in photographs, check survey. If the specific uses of the various poles shown are not noted, or if pho- tographs show poles adjacent to site which are not indicated on survey, request further information. 363 364 APPENDIX The second step in the preparation of the mechanical equipment draw- ings and specifications is the forwarding of data sheets to the custodian of the Government site and the action on same upon receipt of data sheets from him. These data sheets ask for information not covered by survey and proper answers to the questions propounded must be secured. Survey and data sheets must be compared to see that they agree and that data sheets are complete. If data sheet states that there are gas works in the city, and survey shows no gas mains, the custodian of site should be requested to state size and location of gas mains adjacent. to site. When all the foregoing instructions have been attended to, the drafts- man will initial the data sheet and file it in the appropriate data book; and he will be held responsible for failure to secure at this time all neces- sary data. The next step in the design of the mechanical equipment is the com- pletion of preliminary drawings, which are tracings of the building plans, prepared by the architectural draftsman, showing arrangement of building. The mechanical draftsman will indicate on tracings: The entire plumb- ing and drainage system; all chases necessary for any part of mechanical equipment; the size and location of openings for smoke breeching and stack; size and location of all hot air flues and registers, cold air inlets, ventilators, vent ducts, flues and space required for boilers, fan, heaters, air washers, and other machinery that will be required in connection with heating and ventilating system; location of all outlets, cabinets, tablets and switchboard which will be required in connection with lighting; the space required for elevator machine, tank and pumps that may be required in connection with elevators; the space required for vacuum cleaner; and any other machinery ^that may be required in connection with mechanical equipment. When floor plans are at scale J inch to 1 foot, the mechanical draftsman will note on the preliminaries that architectural draftsman is not to indicate on his drawings any plumbing fixtures or piping but must indicate thereon all other items mentioned above and note also on drawings the finish of the toilet rooms. These preliminary tracings are returned to the architectural draftsman whose duty it is to arrange the building to receive the proposed mechanical equipment. This preliminary work fixes the design of the mechanical equipment with but little chance to change same later, and draftsmen must read carefully the following instructions before the preparation of the preliminaries. Consideration must be given to part of country in which building will be located; as to whether a district heating service is available; style of build- ing; uses to which various parts are to be put; appropriation available; and any other facts that will affect design of mechanical equipment. Consid- eration must also be given to the fact that the assignment of a building as indicated on preliminaries is likely to be changed before occupation, involving division of large rooms, conversion of storage spaces (where pro- vided with light) into offices, etc., and the mechanical equipment must be APPENDIX 365 arranged as far as possible to accommodate such changes with a minimum amount of alteration and expense. In preparation of preliminaries the survey and data sheets must be consulted, and the layout must be made in pencil and approved by the Mechanical Engineer before any work is inked in. The general design of mechanical equipment for large buildings inust be discussed with the Chief Mechanical and Electrical Engineer before laying out same. All vertical pipes in building must be concealed in chases, furring, look- outs, or closets, except when structural conditions prevent, and then pipes may be exposed in locations other than public lobby and court room. ' In addition to chases for plumbing pipes, indicate on preliminaries chases for heating risers of sufficient number to provide a chase for each riser, and a sufficient number of risers to require but one radiator on a floor to be connected to same riser. Heating pipes may be run in same chases with downspouts or vent pipes, but must not be in run in chases with soil or waste pipes unless absolutely necessary. No chase or piping to be run in vaults. Indicate also chases for electric conduits, which must never be run in same chases with heating or water pipes. Chases are not generally neces- sary for conduits where walls are furred, and need never be provided for distribution conduits except at cabinets. Between basement floor and under side of fireproofing of deepest first floor beam or girder there must be a clear height of not less than 8 feet 6 inches; this is the minimum and must be exceeded when possible. Horizontal pipes may be exposed at ceilings of basement, toilet rooms, lookouts, mailing vestibule, workroom, and back of screen in money-order room provided screen extends to ceiling. In all other rooms pipe must be concealed in furring or floor construction. Toilet-rooms floors mustnot be raised above general floor level without special permission of Chief Me- chanical and Electrical Engineer. An Executive Order requires that hot water for cleaning purposes must be provided for all buildings. All buildings must be piped for gas even though there are no local gas works. This is a special departmental requirement. To ascertain for preliminary calculation the approximate amount of direct radiation required to heat the building, multiply the extreme out- side dimensions of building (length by width) by the distance from first floor to ceiling line of first, second, or third floor, as the case may be, to ascertain the cubic contents of heated space; then ascertain the gross wall area of the building, using extreme outside dimensions and the height as determined above; this amount divided by 4 is equal to the glass area and the gross wall area less glass equals amount of net wall area. The total B.t.u. necessary and the total radiation necessary can be determined quickly by multiplying the gross wall area as above obtained by 45 in ordi- nary climates and 50 in extreme cold climates to get B.t.u., and the result divided by 150 for water and 250 for steam will give the square feet of direct radiation necessary. Check this by building cubic contents heated 366 APPENDIX by 100 for square feet if direct steam and by 60 for square feet if direct hot water. Also ohecli by the rule that 1 square foot of direct steam ra- diation will be required for each square foot of glass in climates varying from - 10° to + 10° extreme temperature ; add 60 per cent to above for hot water. Ascertain from data sheets if a district steam or hot-water heating company is in operation or is contemplated in the city where building will be located. If such company exists ascertain the size of service pipe recommended by the heating company to supply the radiation required by the building. If steam is used, ascertain whether heating company will permit service pipe to grade towards street main. In such cases the heat- ing apparatus will be designed to be served from the district heating com- pany and the building will also be provided with boiler for breakdown service. Be sure that there are openings from outside of building to boiler room large enough to permit installation and future removal of boiler. The top of smoke flue or vent shaft must extend not less than 2 feet 6 inches above top of ridge of roof or level of parapet. When a inasonry flue is used for smoke same must be provided with a terra-cotta lining. The largest terra-cotta lining available is 15J inches x 15J inches inside, and where a down-draft furnace is required, or where a larger stack is required, the masonry flue cannot be used. In this case return preliminaries to Mechanical Engineer calling attention to necessity for providing a vent shaft. Indicate size of opening for smoke breeching 2 inches larger than round breeching or 2 inches larger each way than rec- tangular and give distance to center or bottom above floor. Note size of opening in vent shaft cover for smoke stack, which opening must be 4 inches larger in diameter than the stack. To ascertain proper size of coal room for an average Federal building, ascertain the cubic contents based on extreme dimensions and height from bottom of basement to top of flat roof or average height of pitched roof, and figure that one pound of coal will be burned per season for each cubic foot of cubic contents and check on the basis of one-fourth pound of coal per square foot of radiation per day and with 200 days in heating season. Allow coal to be 6 feet deep in room and estimate 50 cubic feet of space per ton of coal. Generally figure to store entire season's supply in the small buildings. Light outlets are located on preliminaries to aid structural engineer to avoid same in designing framing, and also in order to prepare an estimate of cost of conduit and wiring system . Conditions must be carefully studied and light outlets definitely and correctly located. Where for lack of in- formation relative to construction certain light outlets cannot be definitely located, estimate the number of such outlets and include them in the esti- mate of cost. (For rules for calculating number of outlets see "Conduit and Wiring.") Estimate the number of tablets that will be required and determine if reasonably central locations can be obtained for same. If locations are difficult to find, or if tablets will be located on brick walls, obtain from ar- APPENDIX 367 chitectural draftsman information relative to exact locations for tablets, and indicate on preliminary the chases as hereinbefore stated. In all buildings three stories or higher containing a court room, pro- vision must be made for an elevator. If appropriation will not warrant the installation of an elevator, a hoistway or stairwell large enough for a hoistway, and a room suitable for an elevator machine must be provided. A vacuum cleaning-system will not be installed in a building having a total floor area (including basement— of less than 50,000 square feet. When a system is to be installed indicate space required for machinery and chases necessary for risers (see "Vacuum Cleaning"). Any special machinery or appliances such as pumps, tanks, etc., that may be necessary on account of local conditions, must be located on pre- liminaries in order that space may be reserved for same. In preparing preliminaries for extensions the report of the draftsman detailed to secure data must be carefully considered (having in mind also the amount of the appropriation available) in determining whether the entire mechanical equipment of the old building must be abandoned, or whether same shall be extended, to serve the addition. Consult Chief Mechanical and Electrical Engineer in regard to all ex- tensions, but before taking up the subject be in possession of all data, including amount of appropriation available per cubic foot of extension. The estimated value of the plumbing and drainage, plumbing marble, heating and ventilating apparatus, gas piping, conduit and wiring, clock system, telephone system, vault protection system, elevators, lighting fix- tures, etc., must be carefully determined, and noted on the preliminary drawings . The conduit and wiring system estimate placed on preliminaries is to include all special conduit systems. To ascertain the cost of the plumbing and drainage where the building is within 100 feet of city sewer to which it will connect, add together the number of water-closets, urinals, slop sinks, lavatories, shower baths, sinks, fire hose racks, and take four wall hydrants as one fixture and hot water boiler and heater as one fixture. Multiply the number of fixtures so ascer- tained by $125 for 80 fixtures and less, and by $115 for more than 80 fixtures. To ascertain cost of plumbing marble multiply the number of fixtures in toilet rooms by $75. If a terra-cotta private sewer must be run, estimate it at $1 per lineal foot if in earth and $3.50 if in rock ; and if brick or granite pavements must be replaced add $1 per lineal foot to above. Estimate $75 for each manhole; $200 for a cesspool, and $300 for a septic tank. For each water filter of 50 gallons capacity per minute (in new buildings) allow $600. Cost of gas piping system $3.50 per outlet. To estimate the cost of heating apparatus where direct radiation and a portable steel boiler with plain grate is used, multiply the number of square feet of radiation by $1.25 for steam and $1.10 for hot water if building is located in northern or eastern part of United States; and by $1.50 for steam and $1.35 for hot water if building is located in south or southwest. To this add $600 if downdraft furnace is used. Brick-set, horizontal, return tubular boilers would not materially change the estimate. 368 APPENDIX Add for cooling coil and connections for outside heating system 50 centi per square foot of indirect radiating surface. For automatic-temperature control add 60 cents per square foot oi radiation. A fan system with air heated to 70° for ventilation only and with an air washer, will cost approximately $300 per 1000 cubic feet of ail per minute for steam, plus 60 per cent for hot water for ventilating system only, exclusive of registers. Gravity-steam-indirect will cost $2 per square foot of radiation. Vacuum systems will cost approximately 50 cents per square foot oi radiation in addition to cost of a standard one-pipe gravity-return appa- ratus. To estimate the cost of conduit and wiring system multiply the total number of ceiling outlets, bracket outlets, plug receptacles and post-oflBce workroom floor outlets by .114 where building is located near a large city; by $16 when somewhat remote from a large city; and by $20 when in far west or south. For a check rule to ascertain the number of gas or electric outlets in a building, divide the total cubic contents by 2000. This result is outlets, not lights, as the number of lights will average 5 to the outlet. The cost of the lighting fixtures will be approximately $15 each and their aggregate cost, including installation, will be the same as that of the conduit and wiring system. Cost of conduit and wiring for the lighting system of an old fireproof uilding is $25 per outlet; wood construction $20 per outlet. Vault protection systems estimate at $20 per vault. Telephone systems $10 per outlet, for conduit and boxes; no wire or instruments. Clock system at $10 per outlet for conduit and boxes alone. Watchman's clock systems at $10 per outlet for conduit and boxes alone. Cost of clock system complete $35 for each secondary clock. Estimate for vacuum cleaning system : Six-sweeper plant $3,500 Four-sweeper plant 3,000 Three-sweeper plant 2,500 Two-sweeper plant 2,000 Each hydraulic lift operated by city water-pressure direct, estimate at $2000. This will include street connection. Hydraulic lift with pumping plant estimate at $3000. Push-bottom dumb-waiters (office standard) will cost $2000. Push button-freight ele- vator not exceeding 1200 pounds capacity $3000. For each standard drum-type electric passenger and freight elevator estimate $6000. For geared traction type the cost for each elevator will be about $7500. Very small hand-power lifts for machinery only, $150. Where shaft and enclosure are to be built for hand-power lift with car above 4 feet x 4 feet and capacity of 300 pounds, cost will average f APPENDIX 369 Based on the architectural cubic contents of a building,which is obtained by multiplying the extreme outside dimensions of building by the distance from basement floor to top of balustrade on a fiat roof building or to mean height of roof on a steep pitched roof, the cost of the mechanical equipment will approximate the following figures when intelligent estimates are secured from contractors: Per cubic foot Plumbing and plumbing marble 5F0.02 Direct heating ■ 012S Conduit and wiring 0055 The approximate cost of mechanical equipment based on total cost of our standard building is about : Per cent of total cost of building -Plumbing and plumbing marble 6 Direct heating 31 Conduits and wiring IJ Gas piping 0.4 Approximate cost of mecahnioal equipment of a small one-story post- office building is roughly 12 per cent, and for a large building from 15 per cent to 20 per cent, of total cost of building (exclusive of land) . The cost of our small standard buildings for entire completion including mechanical equipment is 35 cents per cubic foot. When the proposed building figures out below this, consult Chief Mechanical and Electrical Engineer. The cost of our standard extensions where some changes of magnitude occur in old part of building will average 45 to 50 cents per cubic foot of the extension only. When the figures are below this, consult Chief Me- chanical and Electrical Engineer. Attention is called to the fact that proposals based on architectural or mechanical drawings made on a scale of i inch to the foot, will average 10 per cent higher than proposals based on same work on J-inch scale to the foot. The cost of the mechanical equipment of our standard one-story post- office buildings will average about as follows: Plumbing $2500 Plumbing marble 900 Heating apparatus 2500 Conduit and wiring 900 Gas piping 300 For our standard three-story building it will average: Plumbing «4000 Plumbing marble IZW Heating apparatus '^100 Conduit and wiring 2300 Gas piping 400 370 APPENDIX The following data compiled by Mr. D. D. Kimball of New York, who has had a large experience in the mechanical equipment of similar public buildings will be oi interest and may be considered as authoritative. " In a study of the cost of installation of heating and ventilating plants, made in a number of schools, it was found that the prevailing custom of apportioning a certain percentage of the total cost of the building for the heating and ventilating apparatus is of no value as these percentage ratios vary more than 100 per cent, even with similar classes of installations. For a given size building the cost of a heating and ventilating system will be approximately the same whether the building is a monumental stone structure or a plain wooden one, but the percentage of cost of the system will be very different. CLASSIFICATION OP SYSTEMS As a result of this study, the following scheme of classification has been arrived at: Class A. Plants providing for fire-tube boilers, double fan systems, air washers and humidifiers, individual or double duct systems and modulat- ing control of direct radiators and mixing dampers. Class B. Same as Class A, but using automatic stokers and water-tube boilers instead of fire-tube boilers. Class C. Same as Class A, but eliminating the modulation control of radiators and dampers and using the single trunk ducts. Class D. Same as Class C, except that it eliminates the use of air washers and humidification systems. Class E. All other systems. Manifestly there are many combinations of equipment which render an exact determination of classification difficult, but in general this classifi- cation has proven satisfactory. After a careful study of this method of classification and the figures on costs as thus obtained, it was found that the only satisfactory basis of determining the cost of the installation of the heating and ventilating plant was on the basis of the cubic feet of space in the building. The variation in costs within the different classes of systems is rarely over 10 per cent from the average, the greatest variation occurring in Class A. The resulting costs are as follows : Class A, cost of plant per cubic foot 2.7 cents to 3.3 cents — average 3.1 cents. Class B, cost of plant per cubic foot 3.3 cents to 3.8 cents — average 3.4 cents. Class C, cost of plant per cubic foot 2.2 cents to 2.5 cents — average 2.4 cents. Class D, cost of plant per cubic foot 2.2 cents to 2.3 cents— average 2.25 cents. Class E, cost of plant per cubic foot 1.9 cents to 2.2 cents— average 2.1 cents. APPENDIX 371 If classes D and E were but abandoned and a proper amount of skill were used in the design, installation and operation of the remaining classes, a suflScient appropriation being provided for the installation and operation of the ventilating plant, it is believed that little basis would be left for complaint as to the success of the artificial ventilating system. Classes D and E are the result of a too limited appropriation, a demand for too large a building for the funds available, too much ornamentation, or too much equipment, or, in other words, an attempt to build a $100,000 building with a $75,000 appropriation, the greatest sacrifice being made in connection with the heating and ventilating plant. Better were a proper building, well equipped, though smaller. As a matter of information it is interesting to note that the cost of plumbing equipment tor school buildings ranges from three-quarters of a cent to one and one-half cents per cubic foot, the average being one and one-tenths cents. The cost of electrical equipment, exclusive of electric power plants, ranges from one-half to one cent per cubic foot, the average being seven-tenths per cubic foot. In the case of the heating and ventilating, plumbing and electrical work, the costs seem to be approximately the same in grade schools and high schools.'' Upon completion of preliminaries, prepare the insert specification for mechanical equipment if the mechanical equipment is to be let with the building, as is the case except in larger buildings where the cost of the entire mechanical equipment will approximate $25,000. The mechanical draftsman must follow up the job and at the proper time obtain of the architectural draftsman floor plans, and trace for finished heating and lighting if said floor plans are made \ inch to the 1-foot scale: and for plumbing, heating and conduit and wiring if said floor plans are made j inch to the 1-foot scale. When an extension is to be made to an old building an engineering drafts- man is detailed to visit the building for the purpose of obtaining all data necessary as a basis for preparation of drawings and specifications for me- chanical equipment of the extension and for any required modifications, etc., in the apparatus in old portion of the building. A draftsman detailed for such duty must, before leaving the office, pro- vide himself with all necessary drawings of the old building, a set of draw- ings of the proposed extension, a B. and S. wire gauge, and a set of data, sheets: familiarize himself with the proper use of transportation requests,, with the keeping of an expense account, the preparation of vouchers, etc.; and ascertain the amount appropriated for the extension, and the estimated cost of structural work of extension, and changes in old buildings. He must not discuss with the officials at the building the assignment, etc., of the proposed extension, nor permit anyone to examine the drawings for same; and must obtain and note data in accordance with the following general instructions : Conduit and wiring system. Indicate location of all light outlets, noting whether same are gas orelectric orboth, and ascertain the number of 372 APPENDIX lights. Note the type of fixture, its condition, whether wired, and if pro- vided with finial or pendant switch. If new lighting fixtures are neces- sary obtain all data necessary in order that specification for same may be prepared. Indicate. swing of all doors of building. If electricity is used in old building for lighting, indicate location of snap switches, size of same, height above floor, and lights controlled by each switch. Give location of switch tablets or switchboards. Make diagram of same showing number, type, and size of switches and fuses. Also indicate whether slate or marble is used for panels and ascertain con- dition of same. Note especially if any spare switches are on panel boards and ascertain their size; also note location of wiring compartment on tab- lets and note construction of cabinets. If capacity of switch is not marked on same obtain dimensions of blades. Note manner in which wires are run, whether in conduit (iron or paper), in moulding, or on knobs or cleats, and condition of same. If possible, indicate runs of all circuits and groups of lights controlled by each switch on tablets. If possible give size of all circuits and in every case give size of main and subfeeders. Note whether feeders are two or three-wire. Where feeders are stranded measure outside diameter of copper cable and if possible give size of wire in strands and number of strands in ouside layer. Note floor construction, fire-proof, wood or otherwise, and whether fin- ished floors are wood, tile, or whatever construction. Give direction of run of floor boards in finished floors. Have superintendent or manager of lighting company fill in service data sheet, answering fully questions No. 15 and No. 17. Get answers to above questions also from telephone company. Make a sketch showing exact location on or distance from site of all poles (electric light and power, telephone or telegraph) . Indicate present services entering building and state whether overhead or underground, and give size. Heating and vendlation. Indicate on the drawings the location, size, construction and condition of all direct and indirect radiators in old build- ing, and size of connections, risers, and branches thereto. State whether radiator connections are above floor, in floor construction, or at ceiling below. Indicate location, size, and elevation above basement floor of all heating mains, and state type and the name of manufacturer of air valves and radiator valves in place. Indicate on drawings location, size, numbers, construction and condition of boiler or boilers; give grate area, water line, kind of coal burned, size and location of breeching and stack, and state whether or not the draft is good. State if building is satisfactorily heated and ventilated. If there is a ventilating system, show location and size of fans, motors, ducts, flues, registers, etc., and state condition; give ele- vation above basement floor bf all parts of apparatus located near ceiling, and state if system is satisfactory or not. If there are no ventilators. APPENDIX 373 report whether same are needed, especially in assembly rooms. State condition of atmosphere of the city, especially in regard to dust and soot. Plumbing and gas piping. Indicate on drawings the location of all plumbing fixtures and note type, name of manufacturer, and trade name (if obtainable) ; also their condition and whether they are satisfactory in number and operation. Give finish of all toilet rooms. Locate all down- spouts and all soil, waste, vent, and water risers of sanitary system. Indicate location and give size of all horizontal soil, waste, vent, water and gas piping. Give elevation above basement floor of all overhead piping- Indicate connection of building to city sewer and give size of connection and size of city sewer. Report whether drainage is satisfactory or if water backs up during rains. Give the distance from basement floor to center of horizontal soil pipes at summit, at point where same leave building, and at not less than two other points. Engage assistance (through custodian) to secure these data if necessary. Ascertain the condition of city water, to determine if filters are neces- sary, and the pressure carried. Fill out and return data sheets, with full report. Size of drawings. All tracings must be 24J inches x 37 inches, with i-inch margin; titles in capital letters designating branch of work, i.e., "Heating," "Electric Wiring," etc. Floor title to be placed midway between side borders, immediately below plan; scale in i^-inoh letters immediately below floor title. Title designating work to be placed midway between floor title and right-hand border line, about 2 inches above bottom border line. "Chief Mechanical and Electrical Engineer" in two lines to be in small italics, immediately above bottom border line, 6 inches from left hand border. Building title in right-hand bottom corner, and Supervising Architect's title in left-hand bottom corner, to be placed only on separate contract drawings. Space to be left for same otherwise. SUGGESTIONS TO SUPERINTENDENTS The following suggestions to Superintendents of Construction belonging to the office of the Supervising Architect, in relation to the mechanical equipment of Federal buildings, were incorporated in a paper presented at the annual meeting of the Treasury Construction Society in July, 1911, at St. Louis, Mo., and are included herein as being connected with the subject- matter of this book. The first precaution of the superintendent should be to familiarize him- self with the specification (not neglecting the general conditions) and the drawings governing the mechanical equipment, and to make marginal notes relative to any items which are not clear to him, or which appear to 374 APPENDIX him to be in error, or, more important still, where there is a conflict between the drawings and the specification. If such matters are taken up with the office at that time for adjustment, for interpretation, or for whatever action is necessary, it will save a lot of trouble in the future. If a superintendent has had comparatively little experience with me- chanical equipment it is a good idea for him to confer with the foremen on the various branches of mechanical work as soon as they report at the building, frankly state that he is a little weak on those portions of the work, and warn them that while he may not see all the defects during the progress of the work the inspector of mechanical and electrical engineering will be very likely to when he comes along, and therefore that their own best interests will be served by strictly following the drawings and specifica- tions and using no material except that which has been specified and approved. Cases are bound to arise where structural conditions will prevent the installation of work or materials strictly in accordance with contract re- quirements, but it should be impressed upon the contractors' representa- tives at the building that they must not make any change, however slight, without the concurrence of the superintendent. The latter's authority permits him to direct a contractor to change the location of a pipe, a con- duit, a cabinet, and tablet, etc., where structural difficulties arise, pro- vided no change in price is involved, but the order to make the change must be made in writing, so that there may be no misunderstanding, and a duplicate of the letter should be placed on the superintendent's files for his own protection and for the information of the inspector who examines the installation. If the superintendent has any doubt as to his jurisdiction in the matter, or as to the best course to follow, it is well to refer the case to the office in advance of taking any action. Great care is taken by the office in selecting the materials and appliances to be used in the mechanical equipment, and the letter of approval gives name of manufacturer, tra de name, and, where possible, catalogue number. After this formal approval, these materials and appliances are as much a part of the contract as anything that went before, and cannot be changed without permission of the Secretary of the Treasury, or an Assistant Sec- retary acting for him, and as all these changes cost the Department time and money they should be avoided whenever possible. If a superintendent recognizes the necessity of permitting a change to be made, i.e., where structural reasons demand it, where serious delay would result by insisting upon the use of exactly what has been approved, etc., etc., he should im- mediately obtain from the contractor a proposal to make the substitution, either with or without change in contract price, whichever the conditions warrant, and should forward it with a brief explanation and with his recommendation. If the conditions which make the change necessary or advisable were not anticipated (as may often be the case where extensions to old buildings are in progress), and an exigency exists, threatening de- lay to other work, or indicating the possibility of some complication, the superintendent should wire the office, stating briefly the conditions and APPENDIX 375 that a proposal from the contractor has been or will be obtained and for- warded; and this wire should give the amount of money involved, exactly or approximately, if any change in price is contemplated, and state clearly just what material is to be changed and what they desire to use in place of it. Except under the above conditions the superintendent should see that the contractor uses what is specified and approved, and nothing else, and even though he is not very familiar with steam heating, plumbing, etc., he should not have much difficulty in identifying the approved devices and fixtures with the aid of the usual illustrations and descriptions. The con- tractors should be discouraged from asking for changes on the ground that they can get "something just as good" for less money, or that their sub-contractors have a large stock of some make on hand and prefer to use it, as these considerations have no weight with the Department, and the requests and refusals cumber the files unnecessarily and get in the way of more important business. Another very important precaution for the superintendent is to examine the mechanical equipment material as delivered, or as soon thereafter as other duties will permit, with a view to rejecting immediately any that is not in accordance with contract requirements. I have known cases where the office used several thousand words, and an enormous amount of time and patience, in obtaining the removal of inferior material, not acceptable even on the basis of a considerable deduction, which the contractor claimed had been put in with the concurrence of the superintendent, or, at least, without any objection from him, which was construed as being equiva- lent to permission to go ahead. These troubles, or many of them, would be avoided by a careful examination of material before installation. It is a fact that much of the trouble in making final settlements, so far as mechanical equipment is concerned, comes from unauthorized changes in appliances and materials, all of which have to be adjusted at that time. The new standard plumbing specifications adopted by the Treasury, War, and Navy Departments, are profusely illustrated and will tend to do away with all uncertainty in regard to the recognition of approved fixtures, etc., so far as new work is concerned. In connection with heating work superintendents will do well to provide themselves with the Crane Company's hand-book of their various steam specialties, and with the Ideal Fitter's hand-book, published by the Ameri- can Radiator Company, Chicago, 111. While the above-named firms generally decline to send their valuable catalogues to persons not engaged in the line of business to which they cater, they would undoubtedly be supplied to superintendents who wrote in their official capacity and stated that the books were for official use. Where omissions, additions, or changes are necessary in connection with work already under contract, and the superintendent is unable to get what he considers a reasonable figure, he should forward to the office without delav the best proposal he is able to obtain from the contractor, accompanied by a statement as to the necessity and the value (itemized) 376 APPENDIX of the work, and a recommendation relative to the amount which should be fixed by the Department as compensation, It is not the intention to require contractors to perform additional work without a reasonable profit, and therefore superintendents should be liberal in estimating on same, giving due weight to the possibility of delaying other work under contract, to the distance from the market where the material must be obtained, and to the cost of expressage, freight, etc., adding a margin of not less than 25 per cent for profit, which includes the cost of doing busi- ness. With these features taken into account, and itemized in the superintendent's statement, the office will be very apt to follow his recommendations. In those cases where contractors are ordered to perform work at a fixed price, the superintendent should give it his particular attention, keep an accurate record of the labor and material used, and on completion report the facts to the office so that same may be available either to justify the position of the Department in case of controversy or to rectify any unin- tentional injustice done the contractor in fixing the price. Where it becomes necessary for the Department to order any portion of the work done at the contractor's expense, it is even more important for the superintendent to keep careful watch of the work as it progresses, to check up the materials and labor used, and to make sure that the contract requirements are strictly followed in every particular, as any failure in this direction would materially weaken the positioa of the Department in case of a controversy with the contractor in regard to the basis of settlement. If a superintendent after due effort is unable to obtain from a contrac- tor a reasonable proposal for work which is necessary, but is not closely associated with work under the contract, as, for instance, work in the old part of a building to which an extension is being added, or work in a new building which was not contemplated by the original contract and in no way affects it, as an independent gas or steam service connection, etc., the superintendent should forward such proposal as he is able to obtain from the contractor, accompanying same with an itemized statement of the necessity and value of the work, and with a proposal from some local contractor, or from sub-contractors on the job. In making estimates for partial payments on mechanical equipment the best results will be obtained by calling on the contractor for a detailed schedule of the values he assigns to the various portions of the work sat- isfactorily in place (no allowance being due for material delivered and not installed), and using these as a basis of comparison with the estimates made by the superintendent himself, who will thus be in a position to check up any errors in over-estimating or under-estimating on either side before the vouchers are prepared. The following data may be of service in this connection : On the heating work the boiler represents approximately 30 per cent of the cost of the job; radiation 20 per cent; piping 26 per cent; labor and APPENDIX 377 profit 25 per cent; and when the boiler is set and all piping run, but radia- tion not connected, the job is "roughed in," and 50 per cent completed. The plumbing is considered 50 per cent completed, or "roughed in," when all pipes are in place and tested, but fixtures not set. The fixtures represent about 20 per cent of the value of the work, and the cost of installa- tion will average about 110 per fixture. The conduit and wiring system is 50 per cent completed, or "roughed in," when all conduits, steel cabinets, and outlet boxes are in place, but the marble tablets, wiring, etc., have not been installed. The marble tablets cost about 20 per cent of the job, and are worth about $1 per cir- cuit to connect. In new buildings conduits of all sizes, in place, will average about $150 per 1000 feet. When a contract includes the removal of old material no credit should be given this factor under the head of percentages of completion on the semi-monthly reports, as this causes confusion in the office and has some- times resulted in sending an inspector to the building for a "preliminary inspection" before there -^as anything for him to see. Particular attention should be given by the superintendent to the pre- scribed tests of the mechanical equipment, which he should require the contractors to make in his presence at the proper time. The specifica- tions give full information relative to the kind of certificates required from contractor and superintendent, and it will help the mechanical inspec- tor a good deal if the superintendent will place a copy of such certificates on the building files. If any portions of the heating apparatus (such as risers in chases) are to be covered in by terra-cotta, etc., the superintendent should have such pipes tested in his presence with steam or water (water pressure not less than 50 pounds), and permit them to be covered if the results are satis- factory. No other portions of the heating installation are to have the non-conducting coverings applied until after the system has been inspected and tested by a mechanical inspector after completion, but the coverings should be at the building for his examination at the time of final inspection, and to insure this result the superintendent should promptly compare the delivered material with the approved samples of covering sent to him from the office, and require the contractors to correct any mistakes imme- diately. As indicated by the specifications, when lighting fixtures are under a separate contract, the connection of the lighting fixtures to the wiring system of the building should be deferred until after the latter has been tested out by an inspector of mechanical and electrical engineering, this having been found to be necessary on account of the controversies which used to arise between the wiring contractor and the fixture contractor when defects in the work developed and the responsibility lay between them. In order to be in a position to fix the responsibility for any defects which may develop during the fixture installation, the superintendent should be present when the fixture contractor makes the prescribed test of 378 APPENDIX gas piping before beginning his work; and it is very important that the superintendent make sure that all gas nipples for lighting fixtures comply strictly with specification requirements, thus avoiding delays on this account after the installation is begun. Particular attention should be paid to tests of piping, wiring, etc., speci- fied to remain in place in buildings which are being extended, and if any parts are found to be not tight, or in any way unfit for use, a proposal for repairs or renewal, as the case demands, should be promptly forwarded by the superintendent, with his explanation and recommendation. Where the specification for extension of a building includes the removal of old mechanical equipment the superintendent should carefully note whether the contractor has the privilege of using any of the old material. Such material as the contractor has no right to use should be listed by the superintendent, divided into groups, such as steel and iron, copper) brass and lead, etc., giving the approximate weights, and proposals for purchase and removal should then be obtained and forwarded. The old-metal markets vary greatly, but the following prices are an indication of what the superintendent may expect under ordinary conditions: Wrought iron pipe $ 8.00 per ton Old boilers (whole) 4 .00 per ton Iron castings and machinery 10.00 per ton Copper wire, etc . 10 per pound Light brass castings 0.05 per pound Lead pipe 0.03 per pound Old hose 0.02 per pound Old plumbing fixtures No settled market price; variable, and generally very low. In regard to old material which is properly considered as debris, the superintendent should take whatever course will dispose of it with the least trouble and get it out of the way of building operations. It is the intention of the office to make at least two inspections of me- chanical equipment before the final inspection, and to make the first of these when the various branches are from 20 to 50 per cent completed, the exact time being regulated by the exigencies of the service, as there are many places to visit and but few inspectors to do the work. It is particularly important that the superintendents give their best attention to work that is to be covered before the inspectors' arrival, and allow no piping, etc., to be concealed until satisfactory tests have been made under the pre- scribed conditions. If a superintendent is in doubt as to whether certain Vork should be considered acceptable a call for an inspector will receive due consideration even before the usual time for making a preliminary examination. Probably all the superintendents know that the office requires formal notice from the contractor, by letter or telegram, when the mechanical equipment is ready for final inspection and test, this precaution being necessary in the event the inspection is delayed or repeated through some APPENDIX 379 fault of the contractor, in which case the next visit of the inspector is at the contractor's expense. This notice should come through the superin- tendent when possible, with his confirmation of the contractor's statements relative to the stage of completion reached, or with such comments to the contrary as the conditions require. It will be helpful to those in charge of routing up the mechanical inspectors if the contractor's notice is obtained and forwarded a little in advance of actual completion, provided the con- ditions are such as to warrant contractor and superintendent in agreeing upon a definite date when everything will be ready for the inspector's examination. When the contractor is unwilling to bind himself to a defi- nite date in advance of actual completion, it will be helpful if the super- intendent will confer with the contractor and then give the office his best judgment relative to the probable date of readiness for the inspector. This will not involve the .contractor, but will give the oflSce a chance to route this job up with others in the vicinity if an inspector is going that way in the near future. The contractor's notice must follow at the proper time, of course, and a telegram from the superintendent stating that such notice is in his possession will be appreciated, and will frequently save an inspector a long trip back over a recently-traveled route. Some of the superintendents seem to misunderstand the status or the motives of the inspectors of mechanical and electrical engineering, and a word on that subject may not be amiss. The inspectors are the direct representatives of the Supervising Archi- tect, selected and appointed because their technical education, their ex- perience, and their judgment are needed in obtaining the execution of the mechanical and electrical branches in strict accordance with contract re- quirements. In reporting every variation, however minor it may appear to be, they are simply carrying out their orders, and superintendents are not justified in believing that inspectors do this for the purpose of placing them before the Department in an unfavorable light. Judging from my own experience, the inspectors would be very glad if they did not find any- thing to criticise, and the office would certainly be overjoyed; and yet in cases where numerous and serious defects and omissions have been re- ported the superintendent in charge of the work has written the office in a strain indicating a spirit of hostility to the inspector, criticising him di- rectly and the office indirectly, and seeming to attribute the blame to every- body but the people at fault, i.e., the (Contractors and the superintendent. Inspectors differ, just like superintendents and other people, but the aver- age inspector if met in a fair spirit will be very glad to help the superin- tendent on the branches of work which are his special province, and to give him the benefit of his experience on such points as valuing work in place, estimating percentages of completion, interpreting drawings and specifications, etc.; and will consider these courtesies well repaid if the superintendent on his part will have all papers relating to mechanical equipment, beginning with the acceptance of proposal, carefully filed in proper sequence and readily available for examination, for with these data, including the duplicates of test reports and copies of any orders the super- 380 APPENDIX intendent has given for changes due to structural conditions, etc., as pre- viously referred to, the inspector will be saved much time and trouble and the office will reap a corresponding benefit in handling his report. About four years ago, for good reasons, the office discontinued the old practice of sending a copy of the mechanical inspector's report to the super- intendent with instructions to make necessary demands on the contrac- tors, and inaugurated the custom of making the demands directly on the contractors. Good results have been obtained, and the superintendents have doubtless been glad to be relieved of the clerical work involved in the former method. They should, however, follow the contractors up and hasten the completion of the work along the lines indicated by the de- mand letter, reporting to the office within a reasonable time if the action taken is not satisfactory. If any variations reported by the inspector are acceptable to the Department, either on a deduction basis or otherwise, the superintendent is notified so that he may govern himself accordingly, and the fact that certain items have been objected to by the inspector need not be taken into account by the superintendent (except when there is an obvious error of omission on the part of the office) unless the demand letter sustains the inspector's views. If a contractor fails to prosecute the mechanical work in harmony with the remainder of the building, or fails to supply omissions and correct defects in accordance with instructions of the superintendent or the office, as the case may be, the superintendent should after a reasonable time ad- dress a formal demand to the contractors, sending a copy of same to the office, with a brief explanation (unless the copy is self-explanatory) of the conditions which demand the action. If this does not promptly bring about the desired result it is no use for the superintendent to delay further, and he should report the case to the office for appropriate action. In the event a superintendent is transferred to another point of duty prior to the correction of defects reported at the time of final inspection of mechanical equipment, he should explain all items carefully to the cus- todian, and impress on him the necessity of submitting a detailed report as soon as conditions will warrant. Prompt action on this feature of the work will tend to expedite final settlement more than any other one thing, and help the office to avoid many of the criticisms now made on account of slow payments. Even when the structure and the mechanical equipment are included in one contract the office is frequently called upon to answer questions relative to the use of the heating apparatus during the erection of the build- ing. In these cases the building contractor may use the heating apparatus of the building, or any other medium which he desires, provided he furnishes temporary heat upon demand of the superintendent which is satisjactory to that officer. Where the heating apparatus is under a separate contract the matter of using it for temporary heat is for adjustment between the contractor and the building contractor, and the office is not interested in the basis of ad- justment. If the heating contractor does not want the apparatus used APPENDIX 381 that is his privilege, and the building contractor must find some other means. In either of the above cases the superintendent should advise the con- tractor that the office will interpose no objection to the use of the heating apparatus for the purpose of furnishing temporary heat, provided it is presented tor final inspection in a first-class condition, in full accordance with contract requirements. It sometimes occurs that a building is ready for general occupancy be- fore the heating apparatus is entirely completed, although the system is in such condition that it can be placed in service and operated by the cus- todian's force; and in such cases (as the interests of the Department will be served by the action) the superintendent should request the detail of an inspector of mechanical and electrical engineering, who will note all omis- sions and defects then existing, after which the system may be operated by the custodian's force.on the understanding that the contractor will not be held responsible for any damage due to such operation, but must cor- rect all defects reported by the inspector and meet all responsibilities entailed by the "Guarantee" and "Notice to Surety" clauses of the specification. Where extensions are made to old buildings which are not vacated dur- ing building operations, special care is taken in preparing the specifications for mechanical equipment and certain portions of the general conditions under the construction specification, so that the building contractor is bound to insure proper heating of the occupied parts of the building and adequate lighting and toilet facilities, failing which the superintendent has the right to act at contractor's expense. When the superintendent's course in the matter is clearly set forth in the specification, which is the endeavor in all such cases, he should act promptly and discreetly and submit vouchers to the office for the necessary expense, with a letter of explanation. Before proceeding with any "exigency" work under these conditions, it is well for the superintendent to get at least two written pro- posals from local parties, and accept the one which is best for the interests of the Department, all things considered, forwarding both proposals to the office with the vouchers. Where the specifications are not clear in regard to the action to be taken by the superintendent in such cases, he should simply obtain and forward the bids with his explanation and recommendation and await instructions. It may be well to call attention to the fact that some cities require the "owner" to sign the application for a permit to open streets, connect to sewers, etc., and in those instances there is no objection to the superin- tendent signing the application as a matter of form, provided he accom- panies same with a statement that the signing in no way binds the Govern- ment or its agents to any payments therefor, as the specifications require the contractor to pay all necessary fees. At a convenient time it is also well to advise the city authorities that the local regulations in regard to plumbing, drainage, etc., do not apply within the Federal lot line, and therefore that the local inspectors have no juris- diction. 382 APPENDIX While the specifications provide that gas and water pipe used in the work outside of the lot line are to be in accordance with the rules of the local companies so far as materials and method of laying are concerned, this does not apply to the building sewer; and the specifications do not permit any reduction in the size of the gas and water pipes. In all the matters treated of in this paper the office must rely to a great extent on the discretion, tact, and judgment of the superintendent, and perhaps it will help him in his work if he will remember that while he may be having a struggle with one building the office is having a struggle with a couple of hundred in various stages of completion. The amount of cor- respondence from all of them is enormous, and steadily increasing, and any- thing a superintendent does in the way of avoiding unnecessary additions to it is appreciated. He should not draw the ofBce into a matter that is properly within his own jurisdiction, but if he must write on a subject, should make his communications as brief and explicit as possible. The ideal superintendent is the one who can erect a building in strict accordance with contract requirements, and with the minimum amount of controversy and correspondence, so that if it were not for his semi-monthly reports of progress the office could almost forget that such a, building was under way. APPENDIX 383 1—1 H P <; GO H m O o o p o e e p. gB^ a Q O H ■s S ™ o J w ^ a o £ a oQ o H rf O o rt fe S^ 3 I S w SS fi cj to pi ■ lO OO T}< 00 < . 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