<» m w *tmm»prm*****»mit*m* mnu t f *»tmi»tm»4*tttti n t » n* ut0 t nnxau Ti— iMiwiaoaiwimHWit'P >^i>., mtm * m $ n t» Notes on Heating and Ventilation ^4 ALLEN mm r : i L I'luiiMinma M«*«a*««W*««*4«Mw****«*«w«M#*««**«««**w«a««tw««««s«i «fcMM- Book_Jt^ GoRyiightl^^ COPYRIGHT DEPOSrr. \ NOTES ON HEATING AND VENTILATION BY JOHN R. ALLEN fi JUNIOR PROFESSOR MECHANICAL ENGINEERING UNIVERSITY OF MICHIGAN Member American Society Heating and Ventilating Engineers Member American Society Mechanical Engineers SECOND EDITION » 5 13 3 DOMESTIC ENGINEERING CHICAGO 49-53 North Jefferson Street 1906 |UBRARY ot CONGrtESS, two Copies Heceivdd JUL 3 1^08 (Uu,f7 f906 COPY tiJ K COPYRIGHT DOMESTIC ENGINEERING 1906 V ^ PREFACE. The chapters comprising this book are a brief resume of the lectures delivered by the author to the classes in heating and ventilation at the University of Michigan. The subject matter was first published as a series of articles in Domestic Exgixeeeing. The book has been written primarily for the steam- fitter and designer of heating systems. It presupposes a knowledge of the construction and operation of the simpler forms of heating* systems and has been reduced to as brief a form as possible so that the reader can readily find the notes or data desired. The design of heating and ventilating systems has not been reduced to an exact science. The factor of judgment and experience in designing heating plants is a large one. One reason for this is the lack of exact experimental data governing some of the most important factors entering into these calculations. This lack must be filled from the designer's experience. The tables of heat losses from radiating surfaces and the tests of pipe coverings have been compiled from the results obtained from the experiments made under the direction of Prof. M. E. Cooley, Dean of the Department of Engineering, University of Michigan. The author also has shown illustrations of tunnel sections which have been used by Prof. Cooley in the design of a number of central heating systems. John R. AI/LEN. Ann Arbor, October 80, 1905. TABLE OF CONTENTS. Introduction. Theory of heat and measurement of tempera- ture . . . . . . . .II Chapter I. Heat losses from buildings and rules for deter- mining the heat losses in different construc- tions ........ 17 Chapter II. Dift'erent forms of heating systems ; their ad- vantages, disadvantage and relative economy 36 Chapter III. The design of a direct steam heating system and the properties of steam . . . -49 Chapter IV. Design of an indirect steam heating system . 81 Chapter \'. Steam boilers and steam piping. Determination of size and details of construction . . . 95 Chapter VI. The connection of mains to risers and risers to radiators, with ilkistrations of different ar- rangements in practical use . . . .122 Chapter VII. The design of a hot water heating system . 147 Chapter MIL Hot water boilers and piping. Determination of size and details of construction DO Chapter IX. \>ntilation and the pollution of air by human beings, artificial lighting and chemical pro- cesses . . . . . . . .172 Chapter X. Design of hot air heating system . . .186 Chapter XI. Fan systems of heating, with tables of fan capacities and condensation in heater coil . 200 Chapter XII. Central heating systems ; their design and in- stallation, with discussion of different meth- ods of carrying pipes underground . . 226 Chapter XIII. Pipe cov(Tings, pipe, valves, temperature regu- lation, air washing and exhaust heating . 252 SUBJECT INDEX. Page. A Absolute temperature .... 12 Air. changes of. for venti- lation 177 dilution of. for chem- icals 175 flues 88-91-181-191-192 loss of pressure in pipes. 218 mixing systems 220 moistening of . . 188-264-265 piping systems 263 pollution of 173 registers, location of... 181 valves 170-244-256 velocity of. in pipes .... 192-211-214-216 washers 265 Anchors for steam pipes.. 243 B Blowers, steel plate Boilers — cast iron, proportions of. 205-106 central heating 100 227 99 158 98 95 52 •:>7 horsepower of hot water proportions of types of , Boiling point of water. . . . Brick walls, heat loss through Buildings, example of heat loss from 33 heat loss from 17-27-28 materials, heat loss from 12 C Carbon dioxide, amount al- lowable 177 Cast iron boilers, propor- tions of 100 radiators, heat loss from 55 Ceilings, heat loss from. . . 27 Central heating, air valves for 244 boilers for 227 carrying of pipes for... 235 design and location. .. .226 gravity system 229 Page. Central beating, heat and power combined 222 high pressure system... 1 30 low pressure 231 pump logs 236 size of pipes 240 systems of distribution . 228 tunnels 237 Coils, heating for fan sys- tem \ .269 pipe, heat loss f rom .. 55-64 Cold air duct 189 Conduction 22 Connections, mains to risers 122 radiator, single pipe. . . .134 radiator, two-pipe 141 Convection, loss by 23 Covering for steam pipe .. 252 relative value of 253 varying thickness 254 varying pressure 255 D Dampers for hot air flues.. 191 Damper regulators 264 Dams in return pipes 102 Direct steam heating 41-49 55-75 radiation, example of . . . 77 Disc fans 2i 2-223 Doors, heat loss from. ... 27 Draining of steam pipes.. 102 Drips 101 Ducts, cold air 189 for fan system 214 for recirculating 190 underground piping .... 235 E Economizers 250 Economy of different heat- ing systems 36-46 Example. direct steam heating 75 fan heatino- 223 heat loss from buildings 33 rage. Example, heat lost bv con- duction 23 heat lost by radiation. .. 21 hot air heating 196 hot water heating 152 indirect heating 90 specific heat 14 size of steam main 11.3 in use of steam tables. . 53 Exhaust steam heating. . .232 steam and hot water heating 249 Expansion "of steam pipes. 101-llS tanks 157 Evaporation, latent heat of 52 total heat of 52 F Factors for exposure 27 Fan coils 209-212 heaters, dimensions of..il3 loss of heat from. . .210-215 heating, air to be sup- plied 203 systems of heating. . 44-200 Fans, disc 222-223 steel plate 205-206 Fahrenheit temperature... 12 Fittings 260 Flow main 157 riser 157 of hot water in pipes. . .168 Floors, heat lost from.... 27 Flues, foul air 193 friction in . . ,- 218 hot air 91-191 materials for 220 proportions of 192 recirculating 190 for indirect radiators. . . 91 Flue radiators 65-92-94 Furnaces, for hot air 39-187-195 Fuel 99 G Gases, specific heat of.... 15 Grates, heating by 37 Grates, proportions of . .98-195 Gravity system 110-229 II Hangers for pipes 243 Heat 11 conduction of 22 convection of 23 latent 51-52 given off by human be- ings 175 given off by illuminants. 177 rage. Heat loss from buildinus.. 17-25-27-28-31 loss from direct radia- tors 55 loss, effect of height on. 25 loss from fan heater coils 210 loss from flue radiators. 65 loss from hot water ra- diators 149 loss from indirect ra- diators 65 loss from pipe cover- ings 253 radiation of 18 specific 14 transmission of, in build- ings 27 unit of 13 relation to work 13 Heater coils for fan svs- tem 209-212 Heating apparatus, classi- fication of 36 by direct steam 49 by exhaust steam 232 bv fan svstem 200 by hot air 186 by hot water 147 by high pressure steam. 230 by indirect steam 81 by low pressure steam.. 232 surface 98 Horespower of steam boil- ers 100 for disc fan 222 for steel plate fan.. 205-206 Hot air, heating, example of : 196 furnace 39-187-194 flues 91-191-192 Hot water heating, bo'l- ers 155-158 pump system 249 mains, size of 169 natural system 147 open and closed circuits. 166 piping 157-160-169 piping, velocitv of flow in 168 radiators 148 risers, size of 171 rules for 152 sing-le pipe svstem 166 Ilumiditv . . . ." 188-264 Indirect heating, example of 90 rules for 89 Page. Indirect heating, hot water. 43 radiators S'2-So-SS steam 43-81 L Latent heat 51-52 Lighting, pollution of air by 174 heat given off bj' 177 Magnesia pipe covering. loss from 253 Mains, return . lUl-115-116-122 steam ..101-112-114-116-122 Moistening of air lSS-265 Mineral wool covering. .. .253 O Overhead steam mains. . . .110 hot water mains 162 P Pipe covering 252 Pipes, expansion of 118 Piping 101-155-260 hangers and anchors for. . 243 capacitv of 114-169 for steam . .101-104-112-122 for hot water. .157-160-169 pitch of • 102-158-160 underground systems. . .153 Properties of steam 49 Pump logs 237 R Radiation 18 Radiators, connection of.. 134 flue 65-94 heat loss from 68 hot water 148-152-169 • indirect steam .. 82-85-89-90 installation of indirect. 85 steam . . . .54-56-68-69-71-75 tappings 85 Registers SS-181-191 Regulation of tempera- ture 261 Reliefs 101 Resistance of air flues.... 218 Return mains. 101-112-116-157 Risers 101-122-157 Rules for. direct steam heating 72-73 fan heating coil 211 heat lost from build- ings 29-31 horsepower of fan 207 Page. Rules for, hot water heat- ing 151 hot water piping 170 hot air heating 195 hot air piping 194 indirect steam heating. . 89 steam pipe sizes 114 S Siphon 102 Skylights, heat loss from. 27 Specific heat 14 Steam boilers 95-98 cast iron 100 heating, direct 41-47-104-114 bv exhaust 232 indirect 43-81 mains . .102-112-114-116-121-122 piping 101-104-122 pipes, expansion of 118 radiators, direct 54-56 flue 65 indirect 82 resistance in pipes 242 tables 51 traps 104 Steel plate blowers 204 Stoves, heating by 38 T Tables, air dilution for chemicals 176 changes of air for venti- lation 179 conducting power 22 example for direct ra- diation 77 example for hot water heating 153 example of hot air sys- tem 197 example of indirect heat- ing 92 fan heater dimensions .. 213 heat loss from direct ra- diation 55-68 heat loss from flue ra- diators 65 heat loss from indirect radiators 67-84 heat loss from hot water radiators 149 heat loss from fan coils . 210-215-216 heat loss from pipe cov- erings 253-254-255 heat given off by illumi- nants 177 Page. Tabk'S, hot air systems, proportions of 194 porportions of cast iron boilers lOU-158 products of respiration from human beings.. 174 products of combustion from sources of light. 174 properties of steam .... 52 radiating power 19 resistance of air flows. .218 size of flues for indirect radiation 88 size of hot water mains. 109-171 size of steam and return mains 114-1 IG specific heat 14 speed and capacity of disc fans 222 speed and capacity of steel plate fans. ".205-206 temperature of air leay- ing indirect radiators 85 Page. Tables, velocity of flow in hot water system .... 1G8 Thermal units 11 Temperature absolute .... 12 of air leaving hot air furnace 195 Fahrenheit 12 regulation 261 Tunnels 287 V Vacuum heating systems.. 268 Valves Il21-233-26() air 244-256 Ventilation 172-180 W Water hammer 103 line in heating system.. 102 seal ^ 102 Windows, heat lost from. . 27 Wooden houses, heat lost from 27 Work, relation to heat.... 13 NOTES ON H EATING AND VENTILATION INTROD UCTION. HEAT. Heat is a form of motion. The modern scientific conception of heat is that it is produced by the mo- tion of the particles of matter which compose any body. Ah Heat. matter is conceived as being made up of small particles called molecules. These particles do not exist in a state of rest, but are in constant vibration. If these particles move slowly the body is at a low temperature ; if they move more rapidly the body is at a higher temperature, the temperature of the body being determined by the rapidity of the motion of the particles. In measuring heat there are two properties to be con- sidered — the intensity and the quantity. This may be compared to measuring water in a pipe. We measure the pressure of the water in the pipe by means of a gauge in pounds per square inch. The quantity of water is measured in pounds. In the same way the intensity of heat is measured by the thermometer in degrees and the quantity of heat is 12 Notes on Heating and Ventilation measured by comparison with the quantity of heat which a pound of water will absorb. Temperature, which is a measure of the intensity of the heat of a body, might also be considered as measuring the velocity of the Temperature. molecules of the body. In me- chanical engineering all meas- urements of temperature are made on the Fahren- heit scale. On this scale the freezing point is taken at 32° and the boiling point as 212°, the tube of the thermometer between these points being divided into 180 equal parts called degrees. We never know the total amount of heat in a body. As it is impossible to bring any body to a condition of absolutely no heat, the heat in any body must always be measured from some assumed zero point and in the Fahrenheit scale this assumed zero point is 2^2"" below the freezing point. For theoreti- cal purposes, however, it is highly desirable to have some absolute standard of heat. A perfect gas at 7^2"" contracts about 1/493 of its volume for each degree Fahrenheit that it is reduced in temperature. If, then, we keep on decreasing the temperature of a perfect gas from 7,2°, until it reaches a point 493° below 32° Fahrenheit, it would have, theoretic- ally, no volume. If it has no volume, the amount of heat which it contains must be zero. This point, then, is called the absolute zero. This point is mani- festly an ideal one. To find the absolute tempera- Notes on Heating and Ventilation 13 ture in degrees it is necessary to add to the Fahren- heit temperature 461 degrees, that is, 1,2° Fahren- heit corresponds to 493° absolute. Heat is not a substance and it can not be meas- ured as we would measure water in pounds or cubic feet, but it must be measured by the effect which it produces. Unit of Heat. Suppose it requires a certain amount of heat to raise a pound of water from 39° to 40° Fahrenheit. It would require three times that quantity of heat to raise a pound of water from 39° to 42° Fahrenheit. The heat required to raise a pound of water one degree Fahrenheit is called a British thermal unit, and is designated by letters B. T. U. Work is measured in foot-pounds. The unit of work is the work required to raise one pound through a height of one foot. ^ .^ <. . . r ^ Relation Between ten units of work or ten foot- „ ^ ^ ,Tr , Heat and Work. pounds would be the amount of work done in raising ten pounds one foot high or one pound ten feet high. Heat is a form of motion, hence there must be some definite relation between heat and work. This relation was first determined by Joule. By a series of experiments Joule found that one heat unit was equivalent to 778 foot-pounds. It is possible, then, to express heat either in heat units or in foot-pounds. 1^ Notes on Heating and Ventilation Different substances require very different quanti- ties of heat to produce the same change of tempera- ture for the same weight. As Specific Heat. for example, to raise one pound of water one degree requires one B. T. U. ; to raise one pound of ice one degree re- quires .504 B. T. U/s ; to raise one pound of wTOught iron one degree requires .1138 B. T. U. The heat necessary to raise one pound of a sub- stance one degree, expressed in British thermal units, is called specific heat. The following table gives the specific heat of the principal substances which we meet with in engineering work :, Table 1. — Specific Heat. Substance — B. T. U. Water 1 ce 504 Glass 197 Cast iron 1298 Soft steel 1165 Wrought iron 1138 Copper 0951 Brass 0939 Tin 0569 Lead 0314 It is required to raise the temperature of a cast iron radiator weighing 300 pounds from 70° to 212°. The temperature through Example. which the iron would be raised would then be 212 minus 70° or 142°. From the table we see that it would require to raise one pound of cast iron one degree .1298 heat Notes on Heating\and Ventilation 1'^ » units, then to raise one pound 142° would require 142 times .1298 or 18.43 heat units, and to raise 300 pounds one degree would require 300 times this amount or 5,529 B. T. U/s, the heat required to heat the radiator. In solid substances the change in volume when they are heated is so small that it is not considered. In gases, however, the change in volume when the gas is heated without being confined, depends di- rectly upon the absolute temperature and may be very large. When air is confined and is heated, it cannot expand; if it does not expand there is no work done because, from our definition of work, it is necessary when work is done, that the body have some movement. On the other hand, when air re- ceives heat and is free to expand it does work. For instance, if air were confined in a cylinder by a pis- ton, and this air were heated, the air would expand and the piston would be moved out. As the piston is moved through a certain space there must be work done. On the other hand, if the piston were blocked so that it could not move, then the air on being heated would do no work. Then in these two cases dififerent amounts of heat will be required to raise the substance one degree, depending upon whether there is external work done or not. It is necessary in gases that we consider two specific heats, the specific heat of constant volume and the specific heat of constant pressure. For air 16 Notes on Heating and Ventilation the specific heat of constant volume is .1689, ^^^ constant pressure it is .2375. It is seldom that we use air in a confined space, so that, so far as this work is concerned, we shall in most cases consider the specific heat of air as .2375 — that is, to raise one pound of air one degree requires .2375 B. T. U., the pressure being constant. CHAPTER L HEAT LOSS FROM BUILDINGS. Heat is lost from a room in three ways — by the direct transmission of the heat through the walls and windows ; by the passage of ,. r , ' n 1 1 Loss of Heat. air up the foul air flues, and by ^^^^ Buildings. the filtration of air through the walls and air leakage around doors and windows. The first two losses are easily determined, but the determination of the loss by filtration must always involve a large factor of judgment and experience. All building construction is more or less porous. This is well exemplified by the old experiment made with a common brick. . Two cornucopias of paper are pasted on opposite sides of a common brick, the large end of the cornucopias being fastened to the brick. Opposite the small end of the cornucopia at one side is placed a lighted candle. By blowing into the cornucopia on the opposite side, the candle may be blown out, the air having passed directly through the brick. * The experiments which have been made in order to determine this loss generally tend to show that in the ordinary well-constructed building the air in the room will change about once per hour, when all doors and windows are closed. 18 XcjTEs UN Heating and Ventilation In order to study the other heat losses from a room it will be necessary to study the laws of cool- ing. A body may be cooled in three different w^ays — by radiation, by conduction and by convection (contact of air). In order to understand these losses more thoroughly, each will be considered separately. The heat that passes from a body by radiation may be considered similar to the light which is given off by a lamp. There is always Badiation. a transfer of radiant heat from the body of a higher tempera- ture to the body of lower temperature. The amount of heat radiated will depend upon the difference in temperature betv/een the bodies and the substance through which this heat passes and the condition of the surface from wdiich the heat is radiated. The losses bv radiation mav be better understood by referring to Fig. i. Suppose the plate PP to be of cast iron i foot square and i inch thick. Let us suppose this place to be on both sides at a tempera- ture of 60°. Let this plate form one side of a room, the w^alls WWW being non-conducting substances and at a temperature of 59°, the air in this space being at a temperature of 60°. Since the plate and the air in the space are at the same temperature, there will be no loss of heat from the air to the walls, but all the heat that passes from the plate PP to the walls must pass by radiation. For ordinary temperatures of heating surfaces, say 60 or 70°, the Notes on Heating and Ventilation 19 loss by radiation will equal the difference in tem- perature between the hot body and the cold body multiplied by a factor representing the radiating power of the body. The following table gives the radiating power of dift'erent substances : Table II — Radiating Power. Radiating power of bodies, expressed in heat units, given off per square foot pei* hour for a difference of one degree Fahrenheit. (Peclet.) Copper, polished 0327 Iron, sheet 0920 Glass 595 Cast iron, rusted 648 Building stone, plaster, wood, brick 7358 Woolen stuffs, anv color 7522 Water 1.085 Heat is radiated in straight lines exactly as light is given oft from the source of light. We may have heat shadows the same as we have light shadows and the intensity of the heat is inversely propor- tional to the square of the distance from the source. Some bodies are transparent to heat and other bodies absorb heat, the same as some bodies are transparent to light and others absorb light. The transparency of bodies to heat is called diather- mancy. Gases, such as air, oxygen, nitrogen, and hydrogen, are almost perfectly transparent to heat, Vvdiile wood, hair, felt and other non-conducting bodies are almost perfectly opaque to the transmis- sion of heat. The loss of heat by radiation is inde- pendent of the form of a body so long as it does not 20 Notes on Heating and Ventilation radiate heat to itself. The color or condition of the surface of different bodies affects their radiant power. Smoothly polished surfaces radiate less heat than rough surfaces. As, for instance, a sur- Figure 1. face painted with lamp black will radiate over 13 times as much heat as a polished copper surface. Suppose we have a glass surface five square feet in area. The glass surface is at a temperature of Notes ox Heating axd Ventilation 21 70° and the objects surrounding it are at a temperature of zero. Example. From the table we see that one square foot of glass (surface) loses .595 heat units in an hour for a difference of one degree between Figure 2. it and the surrounding objects. For a .difference of 70°, then, each square foot of glass would lose 70 times that amount, or 41.5 heat units, and 5 square 22 Notes on Heating and Ventilation feet of glass would lose 5 times that amount, or 207.5 heat and units per hour. The heat transmitted by conduction is the heat which is transmitted through the body itself. For example, take the condition Conduction. shown in Fig. 2. PP is a plate, one side of which is enclosed by the walls WW. Let the temperature of the plate outside be 59°, the temperature on the inside of the plate be 60° ; the temperature of the walls be 60°, Table III — Conducting Power. The conducting power of materials, expressed in the quantity of heat units transmitted per square foot per hour b}^ a plate one inch thick, the surfaces on the two sides .of the plate differing in temperature by one de- gree. (Pec let.) B. T. U's. Copper 515 Iron 233 Lead 113 Stone 16.7 Glass 6.6 Brick work 4.8 Plaster 3.8 Pine wood .75 Sheep's wool .323 the temperature of the air in the room be 6o°. Then all the heat that is lost by the room must be lost by direct conduction through the plate PP. The amount of heat conducted will depend upon the ma- terial of which the conductor is composed and in ad- dition it will also depend upon the difference in temperature between the two sides of the plate and upon the thickness of the plate. The conduction through any plate may be calculated as follows : Notes ox Heating and Ventilation 28 Multiply the factor given in Table III by the differ- ence in temperature between the two sides of the plate and divide the result by the thickness of the plate in inches. The quotient will be the heat trans- mitted l:y conduction per square foot of surface. Suppose a boiler plate 5 feet square, 32"ii^cl^ thick, to have a temperature of 70" on one side and a tem- perature on the opposite of 200^. The dift'erence in temperature of Example, the two sides of the plate would be 130°. The amount of heat conducted would then be 233x130^-1 '2=15145 B. T. U.'s, the heat trans- mitted per square foot of plate. Then five square feet would transmit five times this amount, or 75,725 B. T. U.'s in one hour. Loss by convection is sometimes termed loss by contact of air. Take, for example, the condition shown in Fig. 3. Let P be a vertical plane of metal one foot Convection, square, having its surfaces main- tained at 60° temperature. Let the walls WW also be at a temperature of 60°. Let the air in the room be 59°. Li this case there will be no loss of heat from the walls to the plate by radiation and there will be no loss through the plate by conduction, but heat will be transmitted from che walls and the plate to the air of the room. The air which comes in con- tact with the warmer walls will be heated. As air is heated it becomes liehter and rises and a current 24 Notes on Heating and Ventilation is formed. This produces a circulation of air, and this circulation of air gives rise to a loss of heat by convection or contact of air. The loss of heat by convection is independent of the nature of the surface, wood, stone or iron losing Figure 3. tiiC same quantity of heat, but it is affected by the form of the body — that is, a cyHnder and a sphere would lose different amounts of heat per square foot. Take the steam radiator, for example. The Notes on Heating and Ventilation '^^ air nearest the radiator becomes heated and rises ; as it rises its place is taken by other colder air com- ing off the floor so that a current of air is estab- lished. In the ordinary type of radiator, the loss by contact of air represents about half the loss of heat, the .balance being loss by radiation. The calculation of the heat lost by convection is quite complicated and dift'erent expressions have been derived for this loss for dif- ferent forms of surfaces. Those Calculation of developed by Peclet are given in Convection Box's treatise on Heat. " Losses. The rules given for convection in the text-books on heat cannot, as a rule, be ap- plied to the loss of heat from buildings. All these rules assume that the air surrounding the object is in a perfectly quiescent state. In buildings this is not the case, for the air surrounding a building is rapidly circulated by the winds. Theoretically a high building would lose proportionally less heat than a low building, because in the upper stories there would be a smaller difference in temperature be- tween the air inside the room and the air outside than in the lower stories. This, however, is not the case, as the wind circulates the air outside the build- ing and makes the temperature of the air surround- ing the building on the outside practically the same at all levels. Inside the room, however, the air at the top of the '^6 XoTEi Ox\ Heating and Ventilation rocm is much warmer than that at the floor. The result is that the rate of transmission of heat in rooms with high ceihngs is appreciably higher than in rooms with low ceilings, as in the room with a high ceiling we have a greater difiference of tem- perature between the inside and the outside air at the ceiling. This difiference is not ordinarily consid- ered unless the height of the room exceeds ten feet. If the hei2:ht of the room does not exceed ten feet the temperature taken live feet above the floor line may be assumed at the average temperature in the room. The loss of heat from buildings was first investi- gated both experimentalh' and theoretically by Peclet. The greater part of his work is given in Box's treatise en Heat. The results obtained by Peclet are difificult to apply practically and nearly all the rules that are used to determine the loss of heat from a building are largely empirical. The con- stants determined by the German government are probably the most reliable we have. They are given in the following table, the results being expressed in the heat units transmitted per square foot of sur- face per degree difiference of temperature. It is found that the thickness of glass in the win- dow makes a difiference in the heat transmission. Plate glass transmits about 30 per cent less than single glass, but this is only approximate. In the table below double glass refers to two sheets of Notes ox Heating and Ventilation 27 glass with an air space between, what is sometimes called double glazing. Where brick walls are made double with air space between the air space will re- duce the loss of heat about 20 per cent below that given by a solid wall. The heat losses given in the following table should be increased as follows : Where the room has a north exposure and the winds are severe, add 10 per Factors for cent. \Mien the building is Exposure. heated in the day time only and allowed to cool during the night, add 10 per cent. When the building is heated occasionally — for ex- Table IV — Heat Losses. SuKFACt:. B T. U per h 1" r per sq ft. per degree difference of t mperature. Window, single glass 1.03 Window, double glass 518 Skylight, single glass 1.118 Sljylight. double glass G21 Brick wall 4 inches thick 68 Brick wall 8 inches thick 46 Brick wall 12 inches thick 32 Brick wall IG inches thick 26 Brick wall 20 inches thick 23 Outer doors 42 Floors, wooden beams, planked 083 Floors, fireproof, floored with wood .124 Ceilings, wooden beams, planked 104 Ceilings, fireproof construction 14.5 Ordinary wooden house construction 25 ample, a church — add from 40 to 50 per cent. A\'here a room has a northerly exposure and is subjected to extremely high winds, add 30 per cent. It is usually advisable to assume for un warmed spaces, such as 28 Notes on Heating and Ventilation cellars and attics, a temperature of about 32°. For vestibules and entrances unheated, which are being frequently opened to the outer air, a temperature of 20° may be assumed. In determining the loss of heat from a building all surfaces should be considered which have on the side opposite the room a lower Determination of temperature than the tempera- the Loss of Heat 4. • ^u rr c ojuoo ui xicetu ^^^^^ j^ ^YiQ room. If a room is From a Build- . , . ^ , J situated over a portion of the cellar which is not heated, the loss of heat through the floor should be considered. If the room has over it an unheated attic the loss through the ceiling should be considered. The loss through the sides of a room which is surrounded by rooms at the same tempera- ture may be neglected. Doors entering directly into a room are considered to lose the same amount of heat as the windows. A common rule for the loss of heat from a build- ing is that given by Professor R. C. Carpenter in his book on ''Heating and Ven- Rules for Deter- tilation.'' This rule is developed mining the Loss from the following considera- of Heat. tion. Referring to Table I\\, we notice that one square foot of glass conducts approximately four times as much heat as a brick wall 20 inches thick. If, then, we divide the wall surface by 4, the result will give us Notes ox Heating and Ventilation 29 the number of square feet of glass surface, which would lose the same quantity of heat. Adding to this the actual glass surface would give us the total equivalent glass surface. In addition to this heat transmitted through the walls we must add the heat which is lost by the air which passes directly through the walls themselves. It is assumed that for ordinary sized rooms the air in the room will be changed about once an hour, so that we must figure on heat- ing the entire air in the room about once per hour. One cubic foot of air w^eighs, approximately, 1/13 of a pound. To raise a pound of air one degree re- quires .238 B. T. U.'s. Then to raise one cubic foot of air one degree would require .238xi/i3=.oi83 B. T. U. or one heat unit will heat 1-^.0183=54.6 cubic feet, or in round numbers say 55. If, then, we di- vide the contents of a room by 55 we will have the heat lost by filtration through the walls. Adding these factors together will give the total heat lost from the room. This rule may be expressed more concisely as follows : Rule i. — Divide the contents of the room by f^f^; add the glass surface and to this the zcall surface divided by 4. The sum zvill be the heat lost from the room per degree dUTerence of temperature be- tzveen the air in the room and the air outside the room. Multiply this sum by the difference in temperature between the air inside the room ^ and 30 Notes on Heating and Ventilation that outside of the room and the product zuill be the heat lost from the room. This rule can be expressed algebraically as fol- lows : Let C represent tlie vohimc of the room, W the wall surface, G the glass surface and d the differ- ence of temperature betzveen the air outside and the air inside the room. The heat loss from the room per hour expressed in B. T. U.'s would be ^ On W ] \ i- G d zvhere n is a factor which .55 4 j depends upon the tightness of the room and varies in value from i — j. For ordinary room n^=i, for corridors i.j, for vestibides 2 to j. It is quite customary to assume the difference in temperature between the air in a room and the air outside to be 70°. Where the windows are poorly fitted or the house loosely built the loss by filtra- tion should be doubled, and in halls where the doors are being opened and closed frequently this should be multiplied by three. There is one criticism on this method of figuring the heat lost in the room. The diffusion loss is as- sumed to depend upon the cubic contents of the room. This of course is manifestly not correct, as the diffusion loss occurs through the w-alls and windows and must depend upon the area of the walls and windows. The rule, however, will work Notes on Heating and Ventilation ^i very well for rooms of average size, but where rlie rooms have excessive wall and window surfaces, or where the cubic contents of the room is large com_- pared to the wall and window surfaces, this rule will give inconsistent results. The following rule seems to the author to be capable of a much wider application : Rule 2. — Diz'idc tlie zcall surface by 4; add the glass surface; multiply this sum by the difference in temperature between the air in the room and the air outside J and then multiply the result by iy2. This rule is for a zvell constructed building. If the build- ing is. old and poorly built, then instead of multiply- ing by iy2 the result should be multiplied by 2; en- trance halls multiplied by ^}4. This rule may be expressed algebraically as fol- lows : Let W represent the zcall surface, G the glass surface and d the difference of temperature betzveen the air outside and the air inside the room. Then the heat loss from the room per hour expressed in W ^+G B. T. U.'s zvould be d n, zi'here n is a factor zi'hich depends upon the construction of the house or location of the room and varies in value from 7.5 to 2.j as stated above. In figuring the radiating surface for any room the cubic contents should alwavs be taken into con- 32 Notes on Heating and Ventilation sicleration. In a large room with a small exposed wall surface, if only enough radiation is put in to cover the loss from walls and windows, the room w^ill be slow^ to heat. In addition. to taking care of the loss from w^alls and windows it is necessary for the radiator to heat the air in the room itself. In order to do this a large proportion of this air must either pass through the heating device or be car- ried out by the ventilating flues, so that where the cubic contents of a room is large it is advisable to add from lo to 20 per cent to the radiating sur- face to allow for the heating of the air in the room itself. The above remark applies only when the building is intermittently heated ; wdien the building is continuously heated it is not necessary to consider the volume of the room. The following temperatures are usually assumed in determining the heat losses : Table V — Temperatures Assumed in Heating. Degrees Temperature lof the outside air Temperature of stores 68 Temperature of residences 70 Temperature of halls and auditoriums 64 Temperature of prisons 68 Temperature of factories 60 to 68 Temperature of cellars not warmed 32 Temperature of attics not warmed 32 Temperature of outside entrances 20 The average temperature for the period of the year during which buildings are heated throughout Notes on Heating and Ventilation ^3 the Central States may be assumed to be approxi- mately 35°. The following examples will show the method to be pursued in determining the heat lost from a building. Suppose a room, as shown in Fig. 4. Let the temperature be maintained in the room at 70 de- grees, the temperature of the outside air be o. Let the walls Example 1. be of brick 8 inches thick, plas- tered on the inside, the windows be 2^x6 feet, the ceiling of the room be 10 feet high. Let the room be on the second floor of the building, the rooms above and below heated. The window sur- faces are 2x2^x6=30 square feet. The total wall surface is 20x10=200 square feet. The net wall surface is 200 — 30=170 square feet. Then the heat lost from the room per degree difference of tem- perature by rule 2 would be i7CK-4-f- 30=72 J/^. As the difiference between the outside and inside tem- perature is 70°, the total heat lost is 72^x70=5075 B. T. U. per hour. Take the same room as in Example i, except that the room is covered by a flat tin roof. The air space between the ceiling of the room and roof should be as- Example 2. sumed to be at a temperature of 32°. Then, in addition to the loss figured in Ex- ample I, there will have to be added the loss due to 34 Notes on Heating and Ventilation o' Figure 4. the tin roof. The area of the ceiHng of the room would he 14x20=280 square feet. Referring to Tahle R' we find the loss per hour through ceilings Notes ox Heating and Ventilation 35 of wooden construction to be .104 B. T. U.'s per degree difference of temperature ; then the loss through this ceihng would be, per degree of temper- ature, .104x280-— 29.1 B. T. U.'s. The room being at 70° and the attic space 32°, the difference in tem- perature would be 70 — 32=38 degrees. The total loss through the ceiling would then be 29.1x38= 1 105.8 B. T. U.'s. Adding this to the loss found in Example i we have a total loss from the room, 5,075+1 io5.=6i8o B. T. U.'s. CHAPTER II , DIFFERENT FORMS OF HEATING. The dififerent heating systems may be classed under two general heads — Direct and Indirect. In direct heating the heating sur- Classification of . i i • i -_ ^. . . faces are placed m the rooms to Heating Apparatus. ^ be heated, as, for instance, stoves, steam radiators or hot water radiators. In indirect heating systems the heating apparatus is usually placed in some other room and the heat carried to the room to be heated by means of pipes. Under this head would be included hot air furnaces and the various systems of heating in which fresh cold air is made to pass over steam or hot water radiators on its way to the room. The indirect systems of heating naturally divide themselves into two other classes, those using nat- ural draft and those using forced draft. A good example of natural draft indirect heating is the hot air furnace, where the circulation of air through the house is produced by the difference in tempera- ture between the air in the hot air flues and the cold air outside the flues. The fan systems of heat- ing, used in heating school buildings and churches, are good examples of the forced draft system. In Notes ox Heating and Ventilation 37 this case the draft is largely produced by mechanical means, usually a disc fan or a pressure blower. In order to understand better a discussion of the various forms of heating which will come later, it is desirable to understand in general the advantages and disadvantages of the various forms of heat- ing. The most primitive form of heating apparatus is the grate. In the grate the air which passes through the fire and is heated by the fire all passes up the chimney and Grates. only the heat given off by radia- tion to the walls and objects in the room is effective in heating the room. In grates of better construc- tion this is somewhat improved by surrounding the grate by fire brick so arranged that the brick will become highly heated and radiate heat to the room. But the fact that all the air heated by the grate passes up the stack makes this a very uneconomical form of heating. In the best form of open' grates only about 20 per cent of the heat of the fuel is eff'ective in heating the room. This form of heating, however, has been defended by many. It is a very popular form of heating throughout England and Scotland. The feeling of a grate-heated room is quite dift'erent from that of a room heated by other systems. All the heat is given off by radiation and the air in a grate-heated room is at a considerably lower temperature than the objects and persons in '^8 Notes on Heating and VentiLxVpion the room, owing to the fact that radiated heat does not h.eat the air through which it passes. The air of the room being at a lower temperature, its ca- pacity for moisture is not increased as much as it w^ould be were the air heated to a higher tempera- ture. The result is that the air contains propor- tionally more moisture than is the case in other forms of heating. This, no doubt, is an advantage. On the other hand it is impossible to heat the room uniformly, and a person is hot or cold, depending upon his distance from the grate. Heating by means of grates is practiced only in the more moderate climates. The grate is useful in houses heated by other forms of heating, as it serves as a most efficient foul air flue. The introduction of a large number of grates into a house adds materially to the ease with wdiich the house may be ventilated. The stove is a marked improvement over the grate as a form of heating, particularly from the stand- point of economy. The modern Stoves. base burner stove is one of the most economic and efficient forms of heating, making use of from 70 to 80 per cent of the heat in the fuel. In heating by a stove the heat is given ofif both by radiation and by convection. The hot surface of the stove being at a higher temperature than the surrounding objects in the room, radiates its heat directly to these ob- jects. In addition the air surrounding the stove is Notes ox Heating and Ventilation , 39 heated and rises, passing along the ceihng to the cold wall and window surfaces where it is cooled, drops to the floor and passes along the floor back to the stove to be again heated. In selecting a stove to heat a given room care should be taken to select one of ample size so that only in the coldest weather w^juld it be necessary to crowd it ; that is, keep on the drafts in order to heat the room. At the present time the stove as a general source of heat is being rapidly discarded because of the attendance re- quired, the space occupied and the unsightly ap- pearance of the stove. Another serious objection to the stove is the fact that it does not furnish venti- lation to the room which it heats. The hot air furnace is a natural outgrowth of the stove. In this system one large stove is placed in the basem.ent of the building, the air is taken from the outside, ^ naces. passed over the surfaces of the stove or furnace, carried up through the flues to the rooms to be heated. The principal advantage of the hot air furnace is that it provides a cheap method of furnishing both heat and ventilation, it requires little attendance and does not deteriorate rapidly when properly taken care of. (The greatest disad- vantage of this system is in the fact that the circu- lation of the heated air depends entirely upon nat- ural draft ; that is, it depends upon the difference in weight between the air inside the flue and the air 40 Notes on Heating and Ventilation outside the flues. This difiference of weight is ex- tremely small, so that the force producing circula- tion in the flue is always small. This force is easily overcome either by the winds or by the resistance of the piping. When a very strong wind blows against one side of the house it is difficult to heat the rooms on that side of the house. If the system is carefully designed, however, this difficulty can be overcome in a measure. Another serious objection to the hot air furnace is that it is seldom dust tight and dust and ashes are carried into the room. In general, how^ever, the hot air furnace may be con- sidered as a very good type of heating plant for small residences. In the case of the hot air furnace the heat is carried to the room by convection, as all heat is carried fromi the furnace by the air which passes around the furnace and enters the rooms from the flues. This air circulates in the room and heats the objects and air in the room. The efficiency of the hot air system will vary, depending on the relative proportion of the air taken from outside and upon the temperature of the air entering the room. If the cold air entering the furnace is taken from the house itself and not from outside the efficiency of the hot air furnace will be almost the same as that of a steam furnace ; that is, from 70 to 75 per cent of the heat of the coal will go into the rooms. If, however, the cold air is taken from outside, then Notes on Heating and Ventilation 41 the heat used in heating the air from the tempera- ture of the outside air to the temperature of the room will be lost, and under ordinary conditions of operation the efficiency would be from 50 to 60 per cent. From the standpoint of ventilation direct steam heat has little advantage over a stove, as it gives no means of supplving . , . -r^ . ' , Steam Heating, iresh air. its use m g-eneral ^. ^ Direct. should be confined to rooms which require little or no ventilation. Mechanically, however, it has many advantages over the stove or the hot air furnace. The boiler for a building hav- ing this form of heating can be located anywhere in the basement, and the rooms are free from dirt or gas. The modern radiator is easily adapted to almost any location in the room, it is not affected by w^ind or local conditions, and a distant room may be heated as easily as one close to the furnace. The efficiency of the direct steam heating system is about the same as that of a stove, and with a well-installed plant from 70 to 80 per cent of the heat of the fuel will be delivered by the radiator to the room. The application of direct hot water radiators as a method of heating is similar to that of steam, with the exception that the sur- faces are at a much lower tem- Hot Water, Direct. perature and hence more radi- ating surface will be required. It has an advan- 42 Notes on Heating and Ventilation tage over steam in that the temperature of the heat- ing surface can be controlled easily, and can be any- where from the temperature of the room to 200 degrees, hi the steam radiator the surface is usually not less than 212 degrees. The principal disad- vantage of this system is in the fact that the circu- lation of the system is by natural circulation ; that is, the circulation is produced by a difference in weight between the water in the hot leg of the system and in the cold leg of the system. This dif- ference in temperature is usually about 10 degrees, so that the dift'erence in weight betw^een these two cohniins of water is small and the resulting force producing circulation is, of course, small. It is necessary to be very careful in designing* the piping for the hot water system, as the circulation may be easily affected by resistance of the pipe. In addition it will be aft'ected by the height of the radiator above the boiler ; the greater the height above the boiler, the greater will be the difference in weight between the two columns of water and the stronger w^ill be the force producing circulation.' This sys- tem in general requires more careful design and construction than the steam system. The efficiency of the hot water system is practically the same as that of steam, and we may expect to obtain in the room from 70 to 80 per cent of the heat in the coal. In heating with indirect steam radiation cold air XoTES OX Heating and V'entilation 4 o is drawn from the outside, passed through and around the hot radiator, which is ., •. . 1 • .1 1 ^ Indirect Steam usually situated ui the basement, „ . . ' Heating. and delivered by pipes to the rooms to be heated. The rules governing the intro- duction of air mto the rooms and the method of running pipes is similar to that employed with hot air furnaces. The principal advantages of indirect steam over hot air are : Each room has a separate source of heat, the system is not afifected by the winds and no dust or obnoxious gases are carried to the rooms. The air entering the room will always be as pure as the air which furnishes the source of sup- ply. The source of heat being independent of the position of the boiler, it is possible to place the indirect radiator anywhere in the building and long hot air pipes are not necessary. This makes the indirect radiator much more efficient and more cer- tain in operation than the hot air ftirnace. The efficiency of this system, from the standpoint of coal consumption, will be much less than in direct forms of heating and about the same as the hot air fur- nace ; that is, from 50 to 60 per cent of the heat of the coal will be used effectively in heating. The application of hot water . ,.,..., , - Indirect Hat indirect is similar to that of water Heating. steam and the efficiency is prac- tically the same. The use of hot water indirects has •14 NoTKs ON 11katii\(; and Vkntilation hocii nuicli more liiuitod than the use of steam indi- rocts. The installation of hot water indirects must he (lone with i;reat care so that each radiator will at all times have the proper amount (^f hot water circu- lating; throui^h it. In ihe hot water indirect radi- ators, if for any reason the water in ^ 4^_I o2 (u.t: J- 0) 2 c 0).= bs ste, sed pe per ho 1- o T3

» d i^ 03 per ho of te stea CAST IRON RADIATORS, 38 INCHES. 1 column. ..48 sq.ft. 226 105 .212 1.82 2 column. ..48 sq.ft. 226 76 .265 1.70 3 column. ..45.3 sq.ft. 226 88 .204 1.42 6 column. ..36 sq.ft. 225 71 .217 1.35 WROUGHT IRON RADIATORS^ 38 INCHES. 1 column. .12 sq.ft. 221 89 .446 3.27 2 column. .42 sq.ft. 222 83 .284 2. 3 column. .48 sq.ft. 229 70 f .294 1.77 4 column. ..48 sq.ft. 226 73 .202 1.27 1" wall coil, 1 pipe high. 212 70 .41 2.8 1" wall coil, 4 pipes high. 228 65 .425 2.48 Up by the radiator per square foot per actual sur- face per hour. The steam in the radiator was at a temperature of 226° and the air in the room at a temperature of /6°, the difference in tempera- ture being 150°. If we divide 255.7 by 150 the result is approximately 1.7. This result represents the B. T. U's transmitted per square foot of rated surface per hour per degree difference of tern- ^ Notes on Heating and Ventilation perature between the steam inside the radiator and the air in thvi room. This is the quantity which should be used in comparing the relative merits of the various forms of heating surfaces. The results of a series of experiments made at the University of Michigan, extending over a period of a number of years, together with the results show^n in the foregoing table, lead to the following conclusions : Radiators zvith different steam volumes do not give essentially different results, except as the vol- ume is so small as to restrict the passage of steam. Single column radiators, as shozcn in Fig. 5, usually shoiv larger results than those with more than ouc column. The condensation per square foot of radiator per degree difference of temperature as shown in column 5 of Table VII shows a rapid de- crease as the number of columns increases. The reason for this is quite apparent when we consider the position of the radiating sur- Diiferent Types faces in a single pipe radiator as of compared with the surface in a Relative Efficiency, three-pipe radiator. Referring to Fig. 6, tube B, you will note that this tube can radiate heat in all directions with- out interference, except those lines which radiate to columns A and C. Columns A and C being at the same temperature, no radiant heat passes be- tween them, so that all the surface of column B Fig. 5. Single-Column Cast Iron Radiator. ^ Notes on Heating and Ventilation which would radiate its heat to columns A and C is unaffected. The amount of surface which does this, however, is extremely small. Suppose we take point i on column B. The heat from that point radiates in a straight line in all directions. But all the rays of heat between ray 2 and ray 3 strike on column A and are lost because column A is the same temperature as column B. The number of rays that do this are extremely small in a single column radiator. If we consider column B in a three-column radi- ator and take point i on column B we see that all the rays between 2 and 3, 4 and 5, 6 and 7, 8 and 9, 10 and II are lost and become ineffective for heating as columns A, C, D, E, F, are at the same temperature and intercept rays passing into the room. When the columns in a radiator have been in- creased from 5 to 6 then the inner columns have practically no effect in giving off radiant heat, and the only heat they give off is given by convection due to the passage of air through the radiator. In addition to the experiments given in the table a series of experiments were made on radiators painted dift'erent colors and on unpainted radiators. The results of these experiments seem to show that the painting of a radiator does not materially affect the heat given off by the radiator. Notes on Heating and Ventilation 59 By glancing at Fig. 6 we see that the greater the distance between the columns or pipes of a radiator the smaller would be the number of rays of radiant heat intercepted by other columns of the radiator O O d/ng^/e Co/i/ma boo o o poo r/?ree Co/c/m/?. Fig. 6. and the larger would be the radiating effect; the wider the space between the columns of the radi- ator the more effective does the radiator become in giving off heat. 60 Notes on Heating and Ventilation The writer has had opportunity to make a series of tests on radiators of the two-column type, having the sections of one radiator spaced at 2^ inches and the sections of the other radiator 3^ inches. The increase of ^ inch in the length of space added approximately 10 per cent to the effectiveness of the radiator. Radiators are made in standard heights. The height most used is 38 inches. They can be pur- chased, however, in varying heights from 15 to 45 inches. The radiators of various heights are rated at a certain number of square feet per section. For instance, a 38-inch two-column radiator, as shown in Fig. 7, is rated at 4 square feet per section. As a rule, however, radiators are slightly overrated. A radiator containing 48 square feet has an actual surface, when measured, of about 47 square feet in most two-column radia'tors. In some cases, par- ticularly in radiators having a large number of col- umns, the radiators are very much overrated. In one instance a radiator rated at 36 square feet had an actual surface of only 2^ square feet. In pur- chasing a radiator, therefore, it is important to know that it has approximately the surface given in the catalogue of the manufacturer, as the radi- ating power depends primarily upon the square feet of surface it contains. . Comparing lines 2 and 6 of Table VII you will notice that the two-column wrought iron radiator Fig. 7. Two-Column Cast Iron Radiator. Fig. 8. Three-Column Cast Iron Radiator. Fig. 9. Six-Column Cast Iron Radiator. End view of section. 64 Notes on Heating and VENTILATIO^f transmits about lo per cent more heat than the two-column cast iron radiator. This is undoubtedly due not so much to the difference of material as to the difference in the spacing of the columns com- posing the radiators. Wrought iron pipe wall coil, as shown in the last line of the table, condenses almost twice as much steam as the cast iron ra- diator; in other words, it gives off about twice as much heat as the radiator. The reason for this is not so much the dift'erence in material as the differ- ence of location. In the case of the cast iron radi- ator the air at the base becomes heated, rises along the radiator, becoming more and more heated as it comes nearer to the top, so that at the top of the radiator there is little difference between the tem- perature of the air surrounding the radiator and the temperature of the radiator itself. This reduces the transmission of heat near the top of the radi- ator. In the wall coil, the sections being placed in a horizontal position, the air remains in contact with the coil for a short time only, so that the air sur- rounding all portions of the coil is practically at the same temperature. To state this in another way, in the cast iron radiator, with the sections placed vertically, the difference in temperature be- tween the air outside the radiator and the steam inside the radiator is much less than in the wall coil, where the pipes are placed horizontally, making the wall coil much more eft'ective per square foot of Notes on Heating and Ventilation 65 surface. Approximately we can say that a wall coil will do twice as much per square foot as a cast iron radiator. Their extensive use, however, ex- cepting in shop buildings, is always more or less questionable, owing to their unsightly appearance and the difficulty of installation in many places. Besides the usual radiator in which a large pro- portion of the heat is given off by radiation and a smaller portion by convec- tion, there is what are known Flue Radiators. as flue radiators. In a flue radiator each section, as shown in Fig. lo, has a projecting flange at the outer edge, so that there is confined in the radiator itself a series of narrow hot air flues. In these radiators only the external sur- Table VIII — Heat Loss from Flue Radiators. A B 1. Size of radiator 6 sec. 38" 6 sec. 38" 2. Rated surface, square feet 42 42 3. Actual surface, square feet 39 39.41 4. Temperature steam 226 226.9 5. Temperature external air 103.3 103.5 6. Difference between steam and air.. 123 123.4 7. Condensation per sq. ft. rated sur- face 1847 .1922 8. B. T. U.'s per deg. diff. per sq. ft. rated surface 1.437 1.5 9. Temperature of air entering flues. 106 102 10. Temperature of air leaving flues.. 187 182 11. Cubic feet of air leaving flues per minute 37.59 45.77 12. Average velocity of air leaving, ft. per minute 150.3 171.3 13. Percentage of heat transmitted by flues 36 41 14. Percentage of heat radiated 64 59 Fig. 10. Cast Iron Flue Radiator. Notes on Heating and Ventilation ^'^ face of the radiator acts as radiating surface. The interior surfaces of the radiator act as indirect radiators to heat the air which is drawn up from below the radiator. The heat losses from two well- known forms of flue radiators are given in Table VIII, which gives the loss by radiation from the radiator as separated from the loss due to the heat transmitted to the air in the flues. The action of the flue radiator depends upon the design of the flues. There should be no point of restricted flue area ; that is, the air should be given a free passage from the base of the radiator to the top. Flue radiators are particularly serviceable in rapidly circulating the air in the room and can be used in a large room having small window surfaces to assist in heating the air in the room more rapidly than is done by the ordinary radiator. The flue radiator is also used in connection with ventilation, in which case the base of the radiator is closed and Table IX- -Heat Transmission. Difference in B. T. U.'s transmitted temperature. per deg. diff. per hr. | 80 1.56 90 1.57 100 1.58 110 1.6 3 20 1.615 130 1.63 140 1.645 150 1.65 160 1.675 170 1.69 180 1.705 100 1.72 68 Notes on Heating and Ventilation is connected with the outside air. This phase will be taken up more in detail under the head of Venti- lation. In the foregoing tables it has been assumed that the heat lost per degree of difference of temperature between the steam in the ra- Heat Lost from diator and the air outside the Radiators Under Vary- radiator was a constant quan- ing Temperatures. ^ tity. In general this may be assumed as true for the ordi- nary conditions under which radiators operate. Where radiators are operated on very high or very low temperatures there is a difference in the amount of heat transmitted per degree of difference of tem- perature. Table IX gives the heat transmitted for each degree difference of temperature -between the steam inside and the air outside the radiator per hour per squaje foot of surface for the two-column cast iron radiator 38 inches high. For ordinary conditions of operation — that is, when the steam is at a pressure from atmospheric to 10 pounds and the temperature of the room is 70 degrees — there will be no necessity to consider this variation in the transmission of heat due to differences of temperature between the steam and the air. There are, however, conditions in drying- rooms that are to be kept at a very high tempera- ture, where this will make an appreciable difference in the amount of radiation to be used. In vacuum Notes on Heating and Ventilation 69 systems also, where a very low vacuum is carried, it would be necessary to take these factors into consideration. The following suggestions apply to the placing of radiators in the room. The radiators should be placed in the coldest portion of the room. In gen- eral it is best to place the ra- diators in front of the win- Installation of Direct dow, selecting a radiator of Radiators. such height that the top will be an inch or two below the window sill. There Fig. 11. are a number of advantages in placing the radiator in front of the window. Probably the most impor- 70 Notes on Heating and Ventilation tant is the fact that it reduces the strong cold down draft along the window surfaces. Figure ii shows the effect upon the circulation of the air by placing the radiator in front of the windows. In this case we get two separate cur- rents of air. The current rising from the radiator divides, one current passing out into the room, being cooled by the wall surfaces and objects in the room, dropping down to the floor and passing back along the floor to the radiator ; the other cur- rent, passing directly to the cold wall surface, is cooled, drops down along this surface and comes back to the radiator, making the circulation along the cold walls and windows close to the radiator a local one which does not affect the occupants of the room. Carpets and rugs should not extend under the radiator. If a radiator is allowed to stand upon a carpet or rug for any great length of time, the heat from the legs of the radiator will eventually deteriorate the fabric of the rug. In a carpeted room the radiator may be placed upon a hardwood or a marble base. When radiators are placed next the wall a space of 13^ inches at least should be left for the circula- tion of air behind the radiator. Unless otherwise specified, radiators are usually tapped as in Table X. Notes on Heating and Ventilation '71 The best method of figuring radiating surface is to determine the actual heat loss from the room in B. T. U's, then decide upon the form of radiator which you propose to use. Suppose, for example, that a Rules for Direct two-column cast iron radiator Heating, is selected. The steam pres- sure to be carried is 5 pounds. The temperature in the room is required to be 70 degrees. Referring to the table of heat losses from direct radiators Table X — Radiator Tappings. For one-pipe work radiatoi's containing — Inches. 24 sq. ft. and under 1 From 24 to 40 sq. ft 1^ From 40 to 100 sq. ft 1^2 Above 100 sq. f t 2 For two-pipe work radiators containing — 48 sq. ft. and under. lx% From 48 to 96 sq. ft 1^x1 Above 96 sq. ft. . iy2xli4 (Table VII, we see that a two-column cast iron radiator loses 1.70 heat units per degree difference of temperature per square foot of rated surface per hour. The temperature corresponding to 5 pounds pressure of steam as given in Steam Table (Table VI), is 22y degrees, and the dift'erence between this and the temperature of the room will be 157 de- grees. Then the heat lost will be 1.70X157=266 heat units per square foot per hour. Dividing the heat loss, as given by the rule for loss of heat, by 72 Notes on Heating and Ventilation 2.66 gives the the number of square feet of radi- ation to be used. This is the only method that can be used at all in rooms where conditions are exceptional. For rooms of ordinary construction, heated to 70 degrees, a large number of thumb rules are used. Some of these thumb rules are as follows: In the following rules the expression wall sur- face means exposed wall surface, that is, those sur- faces which have outside air temperature on one side and room temperature on the other side. Rule i. Divide the volume of the room by 35. Add one-fourth of the exposed ivall surface; add the glass surface, and multiply the sum of these three quantities by .2J3. The product will be the direct radiation in square feet. Rule 2. For ordinary rooms. Divide the ex- terior zvall surface by 4, add the glass surface and multiply the sum by .4. B. For entrance halls. Divide the exterior wall surface by 4, add the glass surface and multiply the sum by .34. C. For the Tca// surface in basement rooms be- long the ground line. Divide the 7call surface by 4 and multiply the result by .//. D. For floors having unhealed space below. Divide the floor space by 4 and multiply the result by .23. Notes on Heating and Ventilation 73 Rule 3. Divide the volume of the room in cubic feet by the factors given below and the quo- tient will be the radiating surface in square feet. First -floor rooms, one side exposed 55 First floor rooms, two sides exposed ^0 First floor rooms, three sides exposed. ... 45 Sleeping rooms, second floor 60 to 70 Halls and bath rooms ^0 Offices 50 to y^ Factories and stores 75 to 1^0 Assembly halls and churches 75 lo 1^0 Rule 4. (Baldwin's Rule.) Divide the dif- ferences between the temperature at which the room is to be kept and that of the coldest outside temperature by the difference betzveen the tempera- ture of the steam in the radiator and that at which you wish to keep the room and the quotient will be the square feet of radiating surface to be allowed for each square foot of equivalent glass surface. By equivalent glass surface is meant the wall sur- face divided by 4 phis the glass surface. In all of these rules the factors to be allowed for exposure should be applied. These factors are given under the head of ''Factors for Exposure." Where the rule does not involve the contents of the room it will be necessary in very large rooms or in rooms where the wall surface is very small in pro- portion to the contents of the room, to add a cer- Fig. 12. BASEMExNT PLAN. (74) Notes on Hp:ating and Ventilation '75 tain proportion of radiation, usually not more than 20 per cent, to allow for heating the air in the room quickly when it has once been allowed to cool. Table XI- -Dimensions and Heat Iiosses. B «M 0«M a 3 ' en ;r a Q > d en .^ 03 Tarlor .13'9"xl2'9"x9'6" 1665 216 36 9450 Sitting room. . . 14'3"xl5'6"x0'0" 2100 95 48 7035 Dining room. . . .12'6"xl3'9"x0'0" 1640 145 36 7350 Kitchen . 13'0"xl3'0"x9'fr' 1610 1210 249 197 36 18 10300 7035 Hall .12'0"xl0'0"x9'6" SECOND FLOOR. W. Chamber . . . .ll'6"xl3'6"x8'G" 1320 172 48 10050 Alcove .10'0"x 9'frxS'O" 810 130 40 7560 So. chamber. . . . .12'6"xl4'9"x8'6" 1560 172 24 7035 N. chamber. . . . 13' xl3' x8'f3" 1440 188 24 7455 Bath .6' X 8' x8'6" 410 50 18 3150 E. chamber. . . . .13' x 8' x8'6" 880 160 18 5250 Front Hall. .. j 14' X 4' x8'6" / 885 33 18 2730 8' X 6' x8'6" S In order to understand better the methods of determining the heating surface required for a given house, it would be best to consider a concrete example. Figs. 12, 13 and 14 represent the basement, Example. (Direct first and second floors of a Radiation.) residence. The house is con- structed of wood, sheathed, papered and clap- boarded on the outside and plastered on the inside. On the first floor the rooms are 9 feet 6 inches high and on the second floor 8 feet 6 inches high. Porch T Pi Vestibule I K— [-- 10-i---4 Fig. 13. FIRST FLOOR. (76) Notes on Heating and Ventilation 'J'7 The windows are 6 feet high and the standard size is 3 feet wide. Table XI gives the general dimen- sions of the room and the heat losses from the various rooms, assuming the temperature of the outside air to be zero and the temperature of the inside to be 70 degrees. Table XII — Results of Computation, Direct System First Floor. _ | OQ h Parlor 9450 Sitting room ...:..... 7035 Dining room 7350 Kitchen 10300 Hall 7035 Second Floor. W. chamber 10050 Alcove 7560 S. chamber 7035 N. chamber 7455 Bath 3150 E. chamber 5250 Halls 2730 cfi •^^ o P H OQ "la boo o 1-1 "^ Cj "Q r I e3 10395 7035 8085 10300 7770 11055 8316 7035 8190 3465 5250 3003 39 27 30 39 29 42 31 27 31 13 20 12 CO fl w p 33.5 38 30 32 24 22 13 26 24 7 14.7 14.7 I The method used in determining the British thermal units lost from the room, given in column 6, is the same as those given in the paragraph headed "Rules for Determining Loss of Heat." Take, for example, the parlor. The wall surface is Fig. 14. SECOND FLOOR. (78) Notes on Heating and Ventilation '79 216 square feet. Divide this by 4; the result, 54 square feet, is the equivalent glass surface. Add the actual glass surface, 36 square feet, which makes a total equivalent glass surface of 90 square feet. Multiply this by i^ times the difference be- tween the outside and the inside temperature, which gives the heat lost, or 90X105=9,450 B. T. U. lost from the room per hour. The remainder of the re- sults shown in column 6 have been computed in the same way. In Table XII the second column gives the B. T. U's as determined in Table XI; the third column the B. T. U.'s corrected for exposure, 10 per cent being added to rooms having north and west ex- posures, as, in this case, the prevailing winds are from the west. Column 4 gives the radiating sur- face required to heat the rooms with a two-column cast iron radiator. Column 5 gives the radiating surface as determined by Rule 3. The quantities in column 4 are obtained in the following manner. The steam pressure to be car- ried in the radiator is 5 pounds. The corresponding temperature of steam is 227 degrees. The tem- perature of the room is 70 degrees. The difference in temperature between the room and the steam will be 157 degrees. In the last column of Table VII the heat lost for a two-column cast iron radi- ator is given as 1.7 B. T. U.'s per degree difference per hour. Then the total heat lost per square foot 80 Notes on Heating and Ventilation per hour will be 157X1.7=267 B. T. U.'s, that is, each square foot of radiator surface will give to the room 267 heat units per hour. Dividing the heat lost from the room, as given in column 3, by 267, will give the results shown in column 4. In column 5 the radiating surface has been de- termined by Rule 3, which is sometimes called the Volume Rule ; that is, the cubic contents of the rooms are divided by a certain factor, depending upon the location of the room. A careful com- parison of columns 4 and 5, together with an in- spection of the plans, wnll show the inconsistency of the volume rule. The volume rule can be used only where the room has an average amount of cubic contents, as compared with its wall surface. To get the best results it is better to employ the method that has been used in determining the re- sults in column 4. CHAPTER IV. DESIGN OF INDIRECT STEAM HEATING SYSTEM. It is seldom thai indirect radiators only are in- stalled. This is due chiefly to the increased cost of installation and operation of such a plant, as com- pared with a plant using both direct and indirect radiation. In a residence heated by indirect radi- ation alone, it will be necessary to introduce an excess of air over that required by ventilation. This materially increases the cost of . operation. In designing an indirect heating plant the loss of heat from the building is figured in the same way as w4th the direct system. In using indirect radi- ation alone it will be necessary to introduce enough air so that the heat left in the room wiU supply the loss from the walls and windows. In order to determine the amount of surface to be placed in the room, it is necessary to know the temperature to which the radiator will heat the air and the amount of heat given ofif by the indirect radiator under different conditions of operation. >.H The amount of heat that miay be obtained from a given indirect radiator will depend upon the tem- perature at which the air is taken in, the tempera- 82 Notes on Heating and Ventilation ture of the radiator, and the Heat Lost from , . ^ . . Indirect Steam ^^^ic feet of air passing Radiators. through the radiator. The following table gives the re- lation between the above quantities, assuming the temperature of the air entering the radiator to be zero, the temperature of steam in the radiator 22^ degrees, the temperature corresponding to 5 pounds gauge pressure : In school buildings and in buildings where the flues are of ample size the amount of air passing per square foot of radiating surface may be assumed to be 200 cubic feet per hour. In residences and build- ings where the flues are usually small, the amount of air passing per square foot of surface per hour does not exceed 150 cubic feet. From the results of the tests on indirect radi- ators given, the following points may be noted : If the temperature of the air entering the radiator is constant, then the temperature of the air leaving the radiator will decrease as the amount of air passing through the radiator is increased. In order to determine the amount of heat trans- mitted by the radiator it is necessary to assume the number of cubic feet of air that will pass through the radiator per square foot of radiation. You will also note the difference between the standard or short pin radiator (Fig. 15) and the long pin radi- ator (Fig. 16). As shown in Table XIII, the tem- Fig. 15. Short Pin Indirect Radiator. Fig. 16. Long Pin Indirect Radiator. 84 Notes on Heating and Ventilation peratiire at which the air is heated by the long pin is less than the temperature to which the air is heated by the short pin with the same quantity of air pass- ing. This is undoubtedly due to the fact that the pins Table XIII— Keat Losses from Indirect Radiators be . ^ fee . k a;, a; o rt . C - Q.C* - . m fl ^ "^ o m o . '5 S-i ad «M n '55 . "'' «y "^ -^^ _a O . ai oQ rj ^ "" 'be ^^fc CO ^*3S W m O • ^- O) ^ j_^ •1^ g OJ OJ a ?, oj M (X)._ r; . Soto's O -M -t-J H 1-^ Stan- Stan- Stan- dard Long dard Long dard Long pin. pin. pin. pin. pin. pin. 50 .147 140 .125 .15 .80 .95 75 .143 137 .17 .21 1.17 1.27 lUU .140 135 .24 .26 1.51 1.60 125 .138 132 .295 .31 1.85 1.90 150 .135 129 .355 .36 2.22 2.20 175 .132 126 .41 .405 2.57 . 2.47 200 .130 123 .47 .45 2.90 2.72 225 .127 120 .53 .49 3.25 3.00 250 .123 118 .585 .53 3.60 3.20 275 .121 115 .645 .57 3.90 3.40 300 .119 112 .700 .61 4.22 3.60 are so long that the ends become cooled. On the other hand, the long pin type is a very desirable type to use when one wishes to pass large quanti- ties of air, as the radiator has ample air passage. This is primarily the work for which it is designed. Notes ox Heating and Ventilation tb The short pin gives better results for ordinary houses where small quantities of air pass through the radiator. Table XTV — Indirect Radiators- -Temperature of liOaving Air. 1 >^ii'^ > ^ ,-^ ^ ' OJ-^ CO Q ^ -M . .— i -'-' U4 ^ ^ a ^'^ a -5 5 o) >j 5 o) >j 25 cj ^ .ti .ii O) Oi o o ^ ID (D a> H H H Standa rd Long Standard Long pin. pin. pin. pin. 130 125 135 128 10 134 128 139 132 20 131) 132 144 136 30 40 144 136 141 149 140 153 144 148 50 153 144 158 146 Indirect radiators are placed in a chamber or box, usually situated in the basement of the build- ing, as close as possible to the vertical flue leading to the room which they are to heat. The air is admitted to Installation of the radiator by a duct or flue. Indirect Radiators, connected with the outside air. This duct should be supplied with a suitable damper and, if possible, be so arranged as to close ^6 Notes on Heating and Ventilation V^'.'.'sV'.A-.V'.VVVk-.S^^V'A'^^^^^^^^'^^^^^^^^^^^^'^' Notes on Heating and Ventilation ^'^ automatically when the steam pressure is taken off the radiator. The cold air is usually admitted di- rectly beneath the radiator and the heated air on leaving the room is taken off at one side. The casing surrounding indirect radiators is usually built of galvanized iron or of matched board, lined with tin. If of galvanized iron it should be bolted together with stove bolts, so that the casing may be easily removed. A much better method, but one which is more expensive, is to en- close the radiator in a small brick chamber with cement floor. This chamber should be large enough so that the radiator is accessible for repairs. Some- times a duct is provided in the radiator casing so that cold air may be taken around the radiator and mixed with the heated air through a suitable dam- per, controlled from the room which is heated. This is a very common arrangement in school build- ings. Fig. lo shows a sketch of an arrangement of this kind. The pipes or ducts leading from an indirect radi- ator should be carried to the room as directly as possible. It is better to have a long cold air pipe and a short hot air pipe. A long horizontal hot air pipe should be avoided. Where the air from the indirect radiator is to be used primarily for ventila- tion it is best to place the hot air register near the ceiling. The indirect radiators are usually suspended in 88 Notes ox Heating and \'entilation the radiator chamber on iron pipes supported by rods hanging from the ceiHng. There should be at least lo inches clear space between the radiator and the bottom and top of the casing. The casing of the radiator should fit the radiator as closely as possible, so that very little air is allowed to pass around the radiator without being heated. Indirect radiators should be placed at least 2 feet above the v/ater line of the boiler, if they are to be operated on a o^ravitv svstem of circulation, and should be so arranged that the condensed water* wall drain from them without trapping. The tappings of these radiators are the same as for double pipe direct steam radiators. (See p70.) The following table gives the general proportions for an indirect radiator svstem : Table XV— Size of Flues for Indirect Radiator. Heating surface, sq. ft. Area of cold air supply, sq. in. Area of hot air suppl sq. in. Size of brick y, flue for hot air. Size of register. 20 . . . 30 . . 40 . .. 50 . . . 30 4."> 60 '. . , 75 40 60 so 100 120 100 200 240 280 8x 8 8x12 8x12 12x12 12x12 12x16 12x20 14x20 16x20 8x 8 8x12 10x12 10x15 12x15 14x18 16x20 16x24 20x24 60 00 80 . . 100 120 150 120 . . 140 . . 180 .... 210 It is usual to assume that the air enters the radi- ator at zero degree of temperature, in which case Notes ox Heating and Ventilation 89 it will leave the radiator at about 130 degrees, the steam pressure in the radi- ator being 5 pounds and the Heating Effect of an velocity through the radiator Indirect Radiator. being 200 cubic feet per hour per square foot of radiator. Under the above conditions an ordinary pin radiator will give off 470 B. T. U.'s per square foot, or, say approximately, 450 B. T. U.S. Under these conditions the air en- tering the room will be at a temperature of 130 degrees, and if the temperature of the room is 70 degrees this air will be capable of losing to the room 60 degrees, or in other words, there is 60 de- grees of temperature available in this air for heat- ing purposes, or of 450 B. T. U/s given out by the radiator 210 B. T. U/s are available for heating the room. SOME RULES FOR IISTDIRECT HEATING. Rule i. A. For ordinary rooms. Divide the zvorll surface by 4, add the glass surface, and multi- ply the snm by .6. The quotient zmll be the amount of indirect radiation necessary to heat th? room. B. For entrance halls. Diz'ide the exterior wall surface by 4, add the glass surface and multiply the sum by .75, the product will be the number of square feet of indirect radiation. Rule 2. Figure the heating surface the same as for direct heating. Add 40 per cent. 90 Notes on Heating and Ventilation Rule 3. Divide the volume of the room by 40. The quotient is the square feet of indirect surface required to heat the rooms on the first floor. For second and third fioor rooms divide by 50, and in stores and large rooms divide by 60. Take the same house that was used in the prob- lem for direct heating. In this case all rooms are to be heated by indirect radiation. It is in actual practice an unusual arrange- Example of Indirect ment, but it is figured out in Heating. this way as an illustration merely. The heat loss in this house will, of course, be the same in both direct and indirect heating and is given in Table XII (p. yy) . Assume that the air enters the radiator at zero degrees and leaves at 130 degrees; that the steam in the radiator is at 5 pounds pressure and that 200 cubic feet of air is passed through the radiator per square foot of sur- face. From the results determined in paragraph headed ''Heating Efifect of the Indirect Radiator" each square foot of radiation gives off approxi- mately 450 B. T. U.'s. If the temperature of the room is 70 degrees only 60 degrees of the heat given to the air is effective in heating the room. As the total amount of increase in temperature is 130 degrees, only approximately 6o-f-i30, or 45 per cent, is available for heating. As each square foot of indirect radiation gives off 450 B. T. U's, 45 Notes on Heating and Ventilation ^1 per cent of 450, or 200 B. T. U's, will be available for heating the room. The heat loss as given in the table for the parlor is 10,395 B. T. U's. Divid- ing this by 200 gives 52, the number of square feet of radiation required for the room. Fifty-two square feet of radiation passing 240 cubic feet of air per square foot will pass 12,480 cubic feet of air per hour; 12,480 is 3.47 cubic feet per second. Allowing a velocity of 5 feet per second, the area of Size of Hot Air the hot air pipe is 3.47 -:- 5 ^ .69 Tij^e. square feet. This equals 99 square inches, which is the proper area of the pipe. The size of the cold air pipe leading to the radi- ator is usually made three-quarters the size of the hot air pipe. Table XVI gives the results for the whole house computed in the same manner as given above. In the table the odd figures and decimals have been left off. In selecting the size of radiator for a room, it is necessary to select those that vary by 10 square feet or more, as indirect radiator sections are not made smaller than 10 square feet per section. In a house where the radiators would be less than three sections, it is necessary to put two or three rooms on the same radiator, as it is not desirable to make very small indirect stacks. There is always danger, however, in taking the heat for two separate rooms off the same radiator, that the heat will not dis- 92 Notes on Heating and Ventilation tribute equally between the two rooms. When sep- arate rooms are heated from the same radiator, care should be taken to see that pipes leading to the two rooms have about the same leno:th and as nearly as possible the same resistance. A much more common ar- Combination of Di- rangement of indirect radiators rect and Indirect, is to put in just enough indirect radiation to give the proper amount of air for ventilation and supply the addi- Table XVI — Results of Computation, Indirect System. QQ O 72 ^ o ^ *-lH . bI H S (] floor. ..15.800 73 145 110 12x12 1.500 Skco.nd Floor — W. chamber. alcove 10,370 93 ISO 1 35 12x20 l.GOO So. chamber.... 7,035 35 70 50 8x12 700 X. chamber 8,190 40 80 GO 8x12 750 Bath 3.465 17 40 30 6x 8 300 E. chamber .... 5.250 24 50 35 6x 8 500 tional heat for the room with direct radiation. Each svstem is installed as though the two were separate, Fig. 18. Arrangement of Flue Radiator. 94 Notes on Heating and Ventilation except that they take their steam from the same steam mains and return into the same return pipes. In this system the direct radiators can be installed on the one-pipe system, but the indirect should be installed on the two-pipe system as indirect radia- tion does not work w^ell on a one-pipe system. It is not necessary to put indirect radiation into all the rooms of a residence. They are put into the principal living; rooms, the hall and the large bed- rooms. Where the house is small it may be neces- sary to put indirect radiation only in the sitting room and in the hall. An example of this kind will be taken up under the head of ventilation. Where only a small quantity of air is needed for ventilation Flue Radiators. ^^^^ radiators may be used in place of indirect radiators. The damper in the outside wall regulates the amount of air passing into the room and in ex- tremely cold weather this may be entirely closed. Table YIII on page 65 shows the heat loss from this type of radiation and the amount of air that the flues will pass. In figuring this type of radiation figure the same as for direct radiation and add 25%. Each 30 square feet of flue radiation will furnish ventilation sufficient for one person. . CHAPTER V. STEAM BOILERS AND STEAM PIPING. Boilers are divided into two general classes—^ fire tube or tubular, and water tube or tubulous boilers. The commonest form of boiler used for heating purposes in this country is what is known as the return flue fire tube boiler. These boilers are adapted • to 1 . r J J Types. plants of over 30 and under 150 horsepower and where the pres- sure does not exceed 100 pounds. For pressures above 100 pounds it is customary to use water tube boilers. There is one exception, that is the Scotch marine boiler, which is a fire tube boiler and which can be made to withstand pressures of 200 pounds and over in large sizes, as in this boiler the fire does not come in contact with the out- side shell. For heating purposes there have been introduced a number of special forms of boiler, a great many of these forms being built of cast iron. Cast iron boilers are not operated at pressures exceeding 10 pounds. Any of these forms of boilers may be used for heating and the selection of the proper form will 96 Notes on Heating and \'entilation depend upon the conditions in each particular case. In selecting a boiler the following points should be taken into consideration : The boiler must be of sufficient strength to withstand the maximum pres- sure to be carried. This does not usually exceed ID pounds. It must have sufficient heating sur- face in proportion to the grate surface to be economical. The stack temperature in a low^ pres- sure boiler should not exceed 450 degrees ; in the best plants it does not exceed 300 degrees. The boiler must have sufficient liberating surface so that the steam form.ed in the w^ater may escape from the surface of the water, without carrying a large quantity of water with it. The boiler must have large circulating areas so that the w^ater may be circulated freely to the heating surfaces and the steam formed may pass aw^ay from the heating sur- faces without restriction. The steam that forms on the heating surfaces rises in bubbles and is liberated from the surface of the water. If the boiler has insufficient liberating surfaces or the circulating areas are contracted the steam cannot rise rapidly enough and bubbles of steam remain on the heated surfaces. These bubbles prevent the w^ater from reaching the heating surfaces and as steam is a poor conductor of heat this results in an overheat- ing of these surfaces. This trouble may be very serious, especially in the water tube type of boiler, and results in the burning out of the tubes. In Notes ox HEATI^XT axd \'extilation 97 cast iron boilers the lack of proper liberating sur- faces and sufficient steam space often causes ex- cessive priming. The question of circulating area and liberating surface is of more importance in a low pressure boiler plant than in a high pressure plant, as steam at 5 pounds pressure has about six times the volume of steam, at 100 pounds pres- sure ; so that to have relatively the same circu- lating area and liberating stirface in a low pressure boiler, we shotild have live times as much as in a high pressure boiler. In boilers for heating purposes it is desirable that they should have sufficient steam space, and a large storage of water, particularly if the plant is to be continuously operated. In boilers having large water storage it is possible to maintain a steam pressure on the boiler all night under banked fires. AMiere boilers are to be operated only occa- sionally, it may be desirable to have a small quan- tity of water, as each tin:e the boiler is started it is necessary to heat all the water in the boiler be- fore steam is formed. The ordinary fire tube re- turn flue boiler, on account of its large water stor- age, liberal circulating areas and large liberating surface, is a desirable one for heating purposes. The heating surfaces in a boiler are those sur- faces which have water on one side and hot gases on the other. A boiler should be so proportioned 98 Notes on Heating and Ventilation as to transmit as much of the heat generated by the fuel to the water as possible. Proportion of Experience has determined that Boilers. for best results in boilers of 50 horsepower and over a square foot of heating surface should evaporate not more than three pounds of water per square foot of heating surface. For small houses, where heating boilers of but a few horsepower are used, it is not usual to allow^ a square foot of heating surface to evaporate more than 2 pounds of water and when a square foot of heating surface evaporates more than the amounts given above, the transmission of heat through the plate becomics so rapid that all the heat is not removed ; the result is an exces- sively high stack temperature and a corresponding loss of heat. Surfaces that have steam on one side and hot gases on the other are called super- heating surfaces. It is not advisable to have super- heating surfaces in a boiler. The proportion of grate surface to heating sur- face depends upon the kind of fuel and the in- tensity of the draft. In small boilers used for heat- ing purposes it is usual to allow one square foot of grate surface to every 20 to 30 square feet of heating surface. For boilers 50 horsepower and over it is usual to allow from 30 to 40 square feet of heating surface per square foot of grate sur- face and in very large boilers the ratio is 50 to 60 Notes on Heating and Ventilation 99 square feet of heating surface per square foot of grate. The rate of combustion for anthracite coal will vary from 5 to 7 pounds of coal per square foot of grate surface per hour with average draft. With bituminous coal under similar circumstances, 6 to 8 pounds will be burned in the smaller boilers and from 12 to 15 pounds in the larger sizes. The air opening to be allowed in the grates de- pends upon the kind of coal, but usually does not exceed 50 per cent of the area of the grate. An- thracite and the better grades of bituminous coaj do not require as large opening as do the slack coals. The term boiler horsepower as applied to boilers has no definite value and varies with local cus- toms, and the opinion of the manufacturer. The rating of a boiler should be the amount of steam it can . , . Boiler Horsepower. evaporate with good economy and without producing wet steam. In purchasing a boiler specify the number of square feet of heating surface the boiler should contain. This is a better criterion of the work that the boiler will do than the horsepower rating. The American Society of Alechanical Engineers has adopted the follow^ing rating for the horsepower of a boiler : 100 Notes on Heating and Ventilation Table XVII Cast Iron Boilers for Steam Heating. -lJ CM 7J u P4 u «f-l 6" ^ -M d be . m oA > a» -^.v^ OC ^ a i^ >t >i >> E ^ E «« E "^ 53 0) 53 i; CO aj 5; a 'J) 0. c/3 a Kn a nch iy4 inch IVa inch iy4 inch nch iy2 inch IV2 inch iy2 inch nch ly^ inch 2 inch ly? inch nch 9 inch 2y2 inch 2 inch nch 2 inch 2y2 inch 2 inch nch 2V2 inch 3 ] nch 2y2 inch nch 3 inch 3 inch 2% inch nch 3 inch 3 inch 3 inch inch 3i/> inch inch 3y2 inch inch 4 inch inch 4 inch inch 4 Mi inch inch 5 inch nch 6 incli inch 7 inch Notes on Heating and Ventilation ^^ of 20 is 4.48, which would make the size of the main 4^ inches. Table XVIII gives the common practice in pipe sizes : 'The steam supply of the radiator should never be less than i inch. Steam mains in one-pipe work should not be less than 1^4 inches and in two-pipe work less than i^4 inches. The return connections to radiators should not be less than ^-inch and return mains should not be less than i inch. The drip pipe should not be less than ^-inch. Long horizontal pipes should be one-pipe size larger than the verticals in the same line. In the overhead sys- tem, especially where the building is over seven or eight stories, it is well to make the risers fairly large at the lower end to take care of the con- densed steam. These risers, even at the lower end, should not be less than 2 inches in size. Return Mains. — Return mains cannot be fig- ured for returning the water of condensation at a low velocity alone, but allowance must be made for the very sudden demands which occur when the plant is started and for the air carried with the water. The size of the return main is determined almost entirely by practical considerations. Table XIX gives the relative size of steam and return main and diameter of steam main. Return mains may be placed on a dead level, but as a rule it is desirable to give them some slight 116 Notes on Heating and Ventilation pitch, to some point, preferably the boiler. At its lowest point there will be provided some sort of drain cock so that all condensed steam may be drained out of the system. The radiators, as well Table XIX — Relative Size of Mains. Diameter Steam Pipe. Diameter Return Pipe. 11/2 2 ^ /2 3 4 5 6 12 1 1 1^ • 2V2 3 4 5 5 or 6 as the pipes, should be set so that the condensed steam mav drain from them easily. It is alwavs 3est to drain the condensed steam with the steam, in Pipe Drainage. which case the steam tends to free the pipes of the water of condensation. If mains are long, it is well to drain them at intervals to avoid carrying too much water of condensation with the steam. In the gravity return system where the drip pipes connect to the return system, there should be at least two fe^t difference in l^vel between the steam main and the boiler water level, in order to avoid the possibility of the water from the boiler being Notes on Heating and Ventilation H'^ forced back into the steam main. Check valves wiii not prevent it, the water of condensation will ac- cumulate in the steam main above the check. If it is necessary to drip the steam main at a point below or close to the water line, then it should be drained to a separate system of piping and the condensed steam accumu- lating in this piping should be forced back to the boiler bv some mechanical means. Fig. 24. Steam connections to steam mains should always be taken from the top of the mains so as to avoid the draining of the water of condensation into the connections. In over- head' systems of piping the steam mains may be drained directly through the risers as the amount of condensation is small compared to the number of drain pipes. In this case the risers may be taken from the bottom of the main. In connecting radi- 118 Notes on Heating and Ventilation ators to the pipe system they should be set so as to have a sHght pitch in the direction in which they are intended to drain. Radiators set so that they cannot be entirely drained are a very common source of water hammer. The expansion of pipes in mains exceeding 50 feet in length becomes an important consideration. It is customary to assume that in low-pressure steam piping there will be an expansion oi lyi inches per 100 feet of pipe. In steam mains car- rying a pressure of 80 pounds or over it is customary to allow for an expansion of about lYz inches per 100 feet of length. There Expansion of Pipes. Fig. 25. are three general methods of taking up expansion. First, a simple means is by making offsets and turns in the pipe every 50 to 100 feet, the expansion Notes on Heating and Ventilation 119 being taken iip by the spring in the pipe. This is shown in Fig. 24. This method is seldom used except in pipes under 4 inches. Another method and the method which it is most desirable to use, is to take up the expansion at all 90° turns. In this method the pipe w^hen it reaches the corner turns either up or down and the expansion is taken up //yj/////////////7777777. ^/W/////////////>//. Fig. 26. by the movement around the vertical nipple in the elbows or tees at the corner. This method of taking up expansion is shown in Fig. 25. The author has had the opportunity of observing a system installed, in which expansion amounting to as high as 4 or 5 inches has been taken up in swing joints and the joints (which have been in use for over seven years) have given no trouble whatever. The third method is by use of expansion joints. The use of expansion joints is in general not to be recommended. Fig 26 shows a cross-section of an expansion joint. Expansion joints are quite ex- 120 Notes on Heating and Ventilation pensive and are always liable to leak and require attention. By carefully laying out the piping most systems can be installed without the use of expan- sion joints. The most serious difficulty occurs in the modern high office building. In buildings of not over ten stories expansion joints may be avoided bv anchorino: the risers in the middle so that thev expand in both directions, and allowing for a flex- ible connection between the risers and supply main in the attic and return main in the basem.ent. In this case the radiators in the upper and lower stories of the building must have allowance made in the radiator connections for expansion of the main. Another method that has been used to allow for expansion is by offsetting the pipe at about the mid- dle story. As, for exairiple, in a building of say i6 stories, run the riser up to the eighth story, then offset just under the ceiling of the eighth story for a considerable distance, usually not less than 20 feet, and continuing the riser up at another loca- tion. The principal objection to this method is its appearance. In some cases it is difficult to avoid the use of expansion joints. In using expansion joints, * the joint should be anchored so that the expansion will go in a definite direction. A great deal of consideration should be given to the valving of a steam heating system. Gate valves should be used on horizontal steam mains, as they do not form a water pocket. If globe valves are Notes on Heating and Ventilation 121 used on steam mains, they should Valves, be placed horizontally, that is, in a vertical pipe to avoid forming a steam pocket. Where it is possible to use it, an angle valve makes a very desirable form of valve. In large buildings where the plant will be under the control of an en- gineer, it is desirable to place valves on the steam risers and valves on the corresponding return risers. In residences it is w^ell to avoid valves, particularly on return mains. A valve on the return main is particularly dangerous as it may be closed by ac- cident while the system is in operation, in which case the radiator wall be filled with water and no water will be allowed to return to the boiler. Location of Mains and Risers. — Mains and risers should be located in as inconspicuous a place as possible, at the same time they should be acces- sible. The concealing of mains and risers in the building construction is ahvays a questionable prac- tice. If it is necessary to conceal the pipe it should be concealed under panels screwed on so that they can be removed in case of leakage or other neces- sary repairs. It is not wise to attempt to save in risers by making long radiator connections. The system will give much better operation by having frequent risers w^ith shorter radiator connections. Where risers are concealed in a building of wooden construction they should be carefully protected from the woodwork. CHAPTER VI. CONNECTIONS TO MAINS AND TO RISERS. In making the connections from mains to risers in a steam system there are three things to be con- sidered — the drip, the expansion, and free circu- lation. The simplest form of connection is shown in Fig. 27, and for general purposes it is perhaps Fig. 27. The simplest form of connection. Not desirable if ex- pansion at right angle is great. the best form of connection. The expansion of the main in the direction of its length is taken care of by turning in the threads of the vertical pipes. The expansion at right angles to the main, which is or- Notes on Heating and Ventilation 123 dinarily very small, is taken care of by the spring of the pipes. If the expansion occurring at right angles were very large, then some other form of connection would be desirable. Fig. 28 shows a similar connection, but using ^ 45-degree elbow in place of a 90-degree elbow at the main, as shown in Fig. 2y. This connection of- fers less resistance to the passage of steam than the connection shown in Fig. 2y ; on the other hand, it does not allow of as much expansion. The pipe rising from the main Fig. 28. Using a 45° ell instead of a 90°, as shown in Fig. 1. being at 45 degrees, there is a limited opportunity for any turning in the threads of the pipe and ex- pansion is taken up by the spring of the pipe. In this figure a drip is shown at the bottom of the riser. A drip is often placed at this point, particu- 124 Notes on Heating and Ventilation larly in large buildings. In smaller plants con- densation is carried back through the steam con- nection itself, as in Fig. 27. In larger buildings it is undesirable to carry so much condensation through the horizontal pipes and a drip' is placed at the bottom of the riser, as shown in Fig. 28. Fig. 29 shows a connection similar to that in Fig. 27. It allows free expansion of the main, the same as Fig. 2y. In Fig. 29 all the condensation Fig. 29. Allows free expansion of the main ; requires a drip at the point where riser starts. which has occurred in the main up to this connec- tion will drain into the connection and it is there- fore necessary to place a drip at the point where the riser starts. A connection of this kind is often used where it is desired to meter different riser con- Notes on Heating and Ventilation 125 nections for different consumers, then the conden- sation for each riser or each set of risers can be col- lected and metered with very little possibility of its coming back into the main. This is, in some re- spects, an undesirable form of connection. If for any reason the water level rises in the return system above the horizontal pipe connection to the riser then the ri^er will be entirely sealed from the main .■^/■ser^ Afc///-? Fig. 30. Often used in limited headroom. Usually undesirable. and it will be impossible to get steam into the riser. The writer has experienced this difficulty in places where it was necessary to use this form of con- nection. This happens particularly in gravity re- turn svstems. Fig. 30 shows a form of connection often used where there is very limited head room. As a gen- eral rule this form of connection is a very unde- 126 Notes on Heating and Ventilation sirable one. It allows almost no expansion, all ex- pansion in such a connection must be taken up in the spring of the pipes. In addition to this, if the main happens to carry a large amount of water of condensation, part of this condensation may flow into the horizontal pipe and impede the circulation in the horizontal. Under the same conditions if a ;/'%:v/"5' ,^v/v/> Fig. 31. A different way of carrying off the drip ; used where drip is taken off at end of main. connection such as is shown in Fig 2y or Fig. 28 were used, no difficulty would be experienced. Fig. 31 shows another method of carrying off the drip. This arrangement is used where the drip is to be taken away at the end of the main. It is very often desirable at such points, particularly if the main is long, to remove the air from the pipe. Notes on Heating and Ventilation 127 The figure shoWvS an air valve placed at the end of the pipe. Locating an air valve at the end of a main near the point of the drip facilitates the rapidity of Fig. 32. Drips from two mains to a single drip pipe. Simple but undesirable. the circulation in the main. In a great many installa- tions all the air in the system is taken care of by 128 Notes on PIeating and Ventilation means of the radiator air valves. Such an arrange- ment, particularly if the house be large, always is /¥a. va/// s'-\-\<;'-^\s'^»tx-v i. i'- ' ^ ■^l ^sN , ''^0 < T^S fe Fig. 33. A better arrangement of dripping two mains into one drip pipe. makes the system, slow in circulation. In the larger systems it is absolutely imperative that the steam Notes on Heating and Ventilation 129 mains be properly relieved of air. In addition to making the steam slow in circulation, it causes un- equal expansion of the piping. This trouble will be taken up in another chapter. Fig. 34. Connection from main to riser where liead room is very short and expansion great. Fig. 32 shows the connection of the drips from two mains to a single drip pipe. Such an arrange- ment, while simple, is undesirable, as the condensa- 130 Notes on Heating and Ventilation tion from one main often interferes with the con- densation coming from the other main. This would give very Httle trouble if the connection were made above the water line. The objection, however, to making such connection above the water line is that if the two currents of condensation which meet at this point are not at the same temperature, ham- mering or a chattering noise results. If placed be- low the line there is an opportunity for the two streams of water to interfere with the circulation. A better arrangement is that shown in Fig. 33, in which the two streams of water coming as drip from the steam mains would not strike ^ach other in the sam.e line ; the one stream, would How into the other. The union of the two streams should occur below the w^ater line of the system, if possible. Fig. 34 show^s a connection from main to riser, in which the head room is very short and it is de- sired to take up a large amount of expansion, the expansion being taken up by a swing on the short vertical nipple and by a swing on the riser. This connection has been used for tunnel mains where the head room in the tunnel did not permit of the other forms of connection shown. Fig. 35 show^s the connection between the main and the riser in an overhead system of distribution in which the rooms in the upper story are used and it is desired to conceal the piping connections. As shown in Fig. 35 it will be seen that the con- Notes on Heating and Ventilation 131 nection from the main to the riser is carried in the space between the roof and the ceiling of the room Fig. 35. Connection from main to riser in overhead system of steam distribution. below. The connection from the main to the riser is taken from the bottom of the main. This is not 182 Notes on Heating' and Ventilation objectionable in an overhead system, as each riser has a drip at the bottom and becomes in itself a Fig. 36. Horizontal connection long enough to care for some expansion of riser by the spring of the pipe. drip main, and in some cases this is the de- sirable thing to do, as it keeps the steam and Notes on Heating and Ventilation 133 main entirely relieved of condensation at all points. In making connections between mains and risers an endeavor should be made to locate the main so that the horizontal pipe connecting main to the riser will be as short as possible. If it is necessary to Fig. 37. Simplest form ; short ; drains easily, but does not allow for expansion of riser. m.ake this a long pipe then the pipe should be made one pipe size larger than would otherwise be used 134 Notes on Heating and Ventilation particularly in the single pipe system. In the double pipe system long horizontals are not so objection- able, as the riser may be dripped at its lower end, as shown in Fig. 28. In residence work it is usually found desirable to connect directly from the steam main to the radiators on the first floor instead of connecting these radiators to the risers. This direct connection from the radiator to the main insures a quicker cir- culation of the first floor radiators, which is usually found desirable in residence work. In building work this is not usually the case, the first floor radi- ators are connected to the main risers. The connection between the radiators and the risers should always be carefully considered. There are a great many forms of connection used between the radiator and the riser to Eadiator which it is connected. Each of Connections. these different forms of connec- tion has its advantage and dis- advantage, which must be considered in using any particular type of connection. Figures 36 to 42 deal with single pipe work. Fig. 36 is the simplest form of connection. Its advantage is that it is short, simple and drains easily. The disadvantage of this form of connec- tion is that it does not allow of any expansion. The expansion of the riser would lift one end of Notes on Heating and Ventilation 135 the radiator off the floor and in all probability pro- duce a leaky joint. Fig. 37 is a similar form of connection, but the connection between the valve and the riser is long enough so that a certain amount of expansion can Fig. 38. Desirable, clean, but floor must come up when the trouble-man comes. be taken care of by the spring of the pipe which connects the radiator valve and the riser. Fig. 38 is a very common form of connection used in residence work. The advantage of this connec- tion over the connections shown in Figs. 36 and 37 136 Notes on Heating and V^entilation is that where the pipe passes over the floor there is always opportunity for dirt to collect around and under the pipe and it is difficult to sweep this dirt out. The connection shown places the horizontal pipe in the joist space. The long horizontal pipe Fig. 39. Similar to Fig. 3, witti position of radiator clianged. under the floor allows a certain amount of expansion due to the spring of the pipe. On the whole this is a desirable form of connection. Its principal objec- tion is that it cannot be easily reached in case of accident and it cuts the joists. The most common trouble with such connection is to have a sand hole in the elbow. Of course to repair this it would be necessary to take up the floor. Notes on Heating and Ventilation 137 Fig. 39 is practically the same as Fig. 38, the po- sition of the radiator being changed. Fig. 40. Sometimes used on upper floors : horizontal pipe ex- posed below ceilings is an objection, ^yill do for store and undecorared rocms. Fig. 40 shows *the arrangement of radiator con- nection in which the horizontal is dropped down 138 Notes on Heating and Ventilation under the ceiling of the room below. This con- nection is sometimes used on upper floors. The objection to it, however, is that the horizontal pipe coming just below the ceiling is very unsightly, and it should be used only where the horizontal pipe is exposed in store-rooms or through un- decorated rooms where such pipe would no' be objectionable. rig. 41. Used in office buildings ; good form for fireproof buildings. Fig. 41 is the plan of a connection very commonly used in office buildings. The connection is made from the riser to the radiator, passing the pipe be- yond the radiator and using a corner valve where the radiator connection attaches to the radiator. The principal objection to this arrangement is that it throv.\s the radiator out some distance into the Notes on Heating and Ventilation 139 FiS. 42. Commonly used in residence work, where first floor radiators are fed from main in cellar. room and it is very difficult to sweep around the connection so as to keep it clean. In buildings of fireproof construction and where a large amount of 140 Notes on Heating and Ventilation expansion is to be taken care of, this is probably the best form of connection to use. Fig. 42 shows a connection similar to Fig. 40 for first floor radiators. It is customary in most build- ings to connect the first floor radiator directly to Fig. 43. The simplest connection for a two-pipe system. the main and not to a riser. This arrangement is commxOnly used in residences. The connection is such that we have very easy turns and a very slight resistance for the passage of steam into the Notes on Heating and Ventilation 141 radiator. It is particularly desirable where the system is operated at a low pressure. All the previous figures have dealt with single pipe connections. Fig. 43 show^s the simplest form of radiator con- nection for the two-pipe system. The objection to this arrangement is similar to the objection made to Fig. 36. That is, it is very rigid and will permit of almost no expansion and should only be used where the radiator is located at such a point that it is not necessary to take up expansion. The connec- tion is simple and direct, and from the standpoint of circulation, a desirable one. Fig. 44 shows a connection in which the expan- sion is taken up by means of the spring in the hori- zontal pipes. The verticals to the radiator valves may be made shorter and these connections can all be concealed in the joist space if desired. This ar- rangement can be used for buildings not more than three stories in height. Where buildings are higher the two-pipe connection should be made with a series of elbows, allowing for free expansion — something like that shown in Fig. 41. Fig. 45 shows a two-pipe radiator connection where the radiator is on the first floor and the horizontals are located in the basement. The same connection is shown with a horizontal pipe, allow- ing for expansion. In this case the return connec- tion is shown entering directly into the return main 142 Notes on Heating and Ventilation Fig. 44. Expansion taken up by spring in horizontal pipes. lUsed in buildings not more than three stories in height. without any elbow. This is always undesirable, as the connection is very rigid, not allowing for ex- pansion, and should only be used where the con- Fig. 45. Radiator on ^-st floor and horizontals in basement. 7} 144 Notes on Heating and Ventilation Fig. 46. Connection for automatic system of heat control on the double-pipe system. nection will not be affected by expansion. If ex- pansion must be allowed for in the return main Notes on Heating and Ventilation 145 then a connection similar to that shown for the steam main should be used. Fig. 46 shows the radiator connection for auto- matic system of heat control on the double-pipe system. In this case it is quite common to put the automatic on the steam supply and the check valve on the return. Then when the steam is turned off by the thermostat, the check valve automatically closes, and there is no possibility of the steam or water in the return main getting back into the radi- ator. If no check were placed upon the return a vacuum w^ould be formed in the radiator, due to the condensation, and the water would be drawn back from the return main into the radiator by this vacuum ; then when the steam was again turned on this water would cause a severe hammer in the radiator. In planning radiator connections for a building a long horizontal should be avoided, the length should be only sufficient to take up expansion. The location of the radiator should be carefully selected, so as not to occupy the best space in the room. For example, it is not uncommon to find the radiator in a bedroom occupying the only place in the room for the bed. The position of the radi- ators should be selected also with reference to the risers, so as to make the connections as short and direct as possible. The form of connection should be such as to allow for proper expansion. 146 Notes on Heating and Ventilation Supporting of Pipes. — Horizontal pipes are usu- ally supported by the ordinary form of expansion hanger. As a rule pipes should be supported every ID feet and should be supported at points bearing the greatest weight. In placing a pipe support care should be taken to see that each support bears its proper proportion of weight. In buildings over three stories in height other methods should be taken to take the weight of the risers. An iron strap passing around the pipe and bolted to some portion of the building structure is usually the best means. Large piping is often supported by chains or on brackets with rollers. The supports of large pipes will be taken up under the subject of Cen- tral Heating. CHAPTER VIL DESIGN OF A HOT WATER HEATING SYSTEM. Hot water heating plants may be divided into two classes, those using natural circulation, and those using forced circulation. In residences and small buildings the system using natural circula- tion is almost universally used. It is simpler in construction and cheaper to install and operate. In central hot water heating systems and in the larger buildings the forced system of circulation is em- ployed. It is more certain in circulation, the size of the pipes may be smaller and in such buildings the system may be cared for by an expert attend- ant. The systems of forced circulation will be dis- cussed in connection with central heating. The arrangement of the hot water boiler and of the Natural System, piping in a hot water heating plant is similar to that of a two-pipe steam system, the difference is only in minor changes in the pip- ing system. The circulation in a natural hot water heating system is produced by the difference in the weight of the water in the cold and the hot leg of the system. It depends very largely upon the height of the water column in the cold leg. The 148 Notes on Heating and Ventilation difference in the weight of the water in the two legs of the system is due to the fact that water Weighs less per cubic foot as its temperature is increased, namely : At 130° the weight of water per cubic foot is 61.56 pounds. At 140° the weight of water per cubfc foot is 61.37 pounds. If, then, there were one cubic foot of water in both hot and cold legs of the system with a difference of 10° between the two sides, the force to produce circulation would be .19 pound. It will be seen from this that the force going to produce circulation is a small one and may be easily overcome by the resistance of the piping system. It is important, then, that in in- stalling a hot water system considerable attention be given to the arrangement of the piping. In designing a hot water Loss of Heat From system the losses of heat from Radiators. the building would be com- puted by the same rules as previously given for other systems. These losses of heat having been determined, it will be necessary to replace the loss by the heat given off by the radiator. In order to determine the amount of radiation nec- essary we must know what the losses of heat per square foot are for hot water radiators. Table 20 gives the results obtained from hot water radiators tested under actual operating conditions with hot water. Notes on Heating and Ventilation 149 Table XX shows that the rate of transmission, as given in the last column of the table, is almost the same as for steam radiators. It will be safe to assume that the hot water radiator would • TABLE XX. k. »r u O ■*•> eg ♦a o c 2 o c i o a I- B.T U.pe er hour pe f. in temp. o •a a d a .£■::; = ■^•■5 c 53 E 5/i O- t/) ■ 01 jvj H H -J qs"-^ 38'' 3-column cast iron. . . .187 182 72 180 1.67 38" 2-column cast iron. . . . .190 185 70 200 1.70 38" flue radiator. . .182.5 178.5 70 181 1.65 give off the same amount of heat per square foot whether filled with steam or hot water, the temperature inside and outside of the radiator be- ing the same. This, however, is not the case, as it is customary to operate a hot water plant at a temperature not exceeding i8o° or less. In calculating heating surfaces, the temperature of the water should never be assumed higher than i8o°. The temperature being about 220° under ordinary conditions in a steam radiator and only 180° in the hot water radiator, the total transmis- sion in the hot water radiator is only about 75 per 150 Notes on Heating and Ventilation cent of the transmission by the steam radiator using steam. There is another consideration in hot water heat- ing. The lower the temperature of the radiating surface the more uniform the temperature of the room and the more agreeable the heating effect. Where it is desired to heat almost uniformly all portions of a room, regardless of initial expense, it may be accomplished by installing very large heating surfaces. The reason for this is easily ex- plained. Where the radiating surfaces are kept at a high temperature, say 200° or over, at least 50 per cent of the heat is given off by radiation and the remaining heat is given off by contact of air. When the temperature of the radiating surface is lowered a large proportion of heat is given off by contact of air and a smaller portion by radiation. This allows the air in the room to be at nearly the same temperature as the objects in the room. It is possible, then, in a hot water system to use quite different amounts of radiation, depending upon the effect desired. This may be illustrated by an example. Suppose a room to lose 10,000 B. T. U.'s per hour and that the heating surface has the same rate of transmission whether steam or water is used, and that this rate of transmission be 1.68 B. T. U. per square foot per degree difference of tempera- ture. In the first case, let the room be heated by Notes on Heating and Ventilation 1^1 steam. The temperature of steam in the radiator be 220° and the temperature of the room 70°. Then the heat lost per square foot of surface would be (220 — 70) X the rate of transmission, 1.68=250 B. T. U. The number of feet of radiation required to heat the room will be 10,000-^-250 = 40 sq. feet. In the second case, suppose the room to be heated by hot water radiator at a temperature of 180°. Then the B. T. U. given off per square foot of sur- face w^ould be (180 — 70) X 1-68=185. The num- ber of square feet of radiation required to heat the room would be 10,000-^185 = 54 square feet. In the third case, assume a residence in which a very uniform heating condition is desired and the temperature- of the heating surface is not to exceed 150°. The loss per square foot of radia- tion would be (150 — 7o)Xi.68=:i35 B. T. U. The radiation required would then be 10,000^- 135 = 75 square feet. The amount of radiation in hot water heating depends, then, upon the effect de- sired. In a closed tank system it would be entirely pos- sible to obtain a temperature as high as 240° or 250°. In the open tank system the temperature should never exceed 180°, as a higher temperature than this would form steam in the tank and there would be danger of the water boiling, which causes a cracking, hammering sound in the piping system. 152 Notes on Heating and Ventilation Rule I. — Divide the volume Rules for Hot Water of the room by 55. Add ^ Heating. of the exposed wall surface. Add the glass surface. Mul- tiply the sum of these by .4, the product will be the square foot of direct hot water radiation required. Rule 2. — For ordinary rooms divide the exterior wall surface by 4 ; add the glass surface and multi- ply the sum by .55. For entrance halls multiply the sum by .7. Rule 3. — Divide the volume of the room in cubic feet by the factors given below and the quotient will be the radiating surface in square feet. First floor rooms, i side exposed .40 First floor rooms, 2 sides exposed 37 First floor rooms, 3 sides exposed 34 Second floor rooms 45 — 50 Halls and bath rooms 35 Offices 37—50 In all these rules factors of exposure are to be allowed as given on page 2y, In order to understand better the methods of de- termining the heating surface required for a given house, take the same house as figured for steam on page 75. Take, for example, the parlor, assuming the out- side air to be at zero degrees and the inside air at 70° The wall surface is 216 square feet and one- quarter of this is 54. Add the glass surface, 36 Notes on Heating and Ventilation 1^3 square feet, and multiply the sum by i^ times the difference between the temperature of the room and the outside air, or (54 + 36) X i>^ X 70 = 9,450 B. T. U.'s. To this add 10 per cent for exposure, which gives the loss as 10,395 B. T. U/s per hour. In Table XXI the second column gives the B. T. U.'s, as determined in Table XII, column 3. Col- umn 3 gives the radiation in square feet for a two column radiator. Column 4 gives the radiation as determined by Rule 3, the volume rule, the vol- TABLE XXI. Results of Computations — Direct Hot Water. -:: t: « t: t:l5 6 3 w 3 3-j^ 2— <^ c c '^^ "^ ^ "■5 ' "^ "2 -^ OQ First floor — Parlor ". 10,395 68 45 68 Sitting room 7,035 46 52.5 50 Dining room 7,350 48 48 48 *Kitchen 10,300 67.5 47 40 Hall 7,035 46 32.5 48 Second floor — W. chamber 10,050 65 39 65 Alcove 7,560 49 18 40 S. chamber 7,035 46 34.5 46 N. chamber 7,455 49 32 50 Bath 3,150 20 12 20 E. chamber 5,250 34 25 34 Halls 2,730 18 25 20 ♦Just enough radiation to keep from freezing in ex- tremely cold weather. 154 Notes on Heating and Ventilation umes of the rooms being taken from Table XL Column 5 gives the radiation that would actually be used. The quantities in column 3 are obtained as follows : Assume the temperature of the water entering the radiator at 175° and that of the tem- perature of the water leaving the radiator 165°, then the average temperature in the radiator is 160°. The temperature in the room is 70°, the difference being 90°. The rate of transmission as given in Table XX, line 2, is 1.70 B. T. U. The total transmission per square foot per hour is, then, 1.70X90=153 B. T. U. Dividing the heat lost from the room, column 2, by 153, or the loss for each square foot of radiation, will give the results in column 3, the number of square feet of radia- tion required. In column 4 the radiating surface has been determined by the volume rule, Rule 3, and shows the inconsistency of this method of fig- uring though it is a method very commonly used. This method should never be used except as a check. When the volume rule shows very much larger results than the other rules it is well to add surface to the radiator to allow for the increase in volume. This has been done in column 5. In re- gard to proportioning of radiation one can never trust absolutely to his figures and should always carefully compare his results with the room and its exposure and use his judgment in regard to changes that seem desirable. CHAPTER VIII. HOT WATER BOILERS AND PIPING. Hot water boilers are practically the same as steam boilers. Any good form of steam boiler may be changed to a hot water boiler by filling the steam Hat Water Boilers, space with water and allowing the water to go in at the lowest point of the boiler and go out at the highest point of the boiler. In boilers especially designed for hot water heating no space is left over the tubes, the whole boiler shell being filled with tube surfaces. This makes the hot water boiler more compact for the same amount of heating capacity than the steam boiler. The circu- lation in the hot water boilers is probably slower than in steam boilers and there is much less local circulation. The cold water enters from the bot- tom, passes over the tubes and leaves at the top of the boiler. The heat transmitted per square foot of surface is practically the same in steam and hot water boilers. The proportions of heating surface to grate surface and of grate surface to chimney area may be taken the same for hot water as for steam. In large hot water systems the ordinary fire tube boiler is used. The principal modification of the 156 Notes on Heating and Ventilation boiler would be to fill the steam space with tubes and make the return opening same size as the steam opening. For residence work cast iron, sectional boilers are usually used and these are suitable for all similar work, except wdiere high pressure is used. In high pressure hot water heating, cast iron boilers are not permissible as these boilers are not usually made to withstand pressures exceeding 20 pounds. A pressure of 20 pounds corresponds to a water column 46 feet high and this is about the height of an ordinary four-story building. It is not desirable to use cast iron boilers in buildings more than three stories high, above that height wrought iron boilers should be used so as to with- stand the' static pressure due to the height of the water. Cast iron boilers would not oe suitable for hot water systems using a closed tank and having the water under pressure. Boilers for these systems are usually made to withstand safely a pressure of 100 pounds per square inch. The pro- portions of cast iron boilers for hot water heating are given in Table XXII. In this table the rating of the boiler does not include the piping. In select- ing the boiler the square feet of radiation equiva- lent to the piping must be added to the square feet of radiator surface. In the average house these boilers will carry .6 of their rating in actual radia- tion, exclusive of piping, provided the piping is covered with some good grade of pipe covering. Notes on Heating and Ventilation l^'^ Table XXII is based on approximately the fol- lowing, allowing one square foot of grate to each 30 square feet of heating surface, and one square foot of grate to each 300 square feet of radiation. (This radiation must include the radiating surface in the mains.) In designing a hot water piping system the most im- Hot Water Piping. portant consideration is the resistance of the piping. The resistance of the piping should be almost the same for each radiator at the same level and the friction of the piping sys- tem should be kept as low as practicable. Definition of Terms Used. — The different parts of the piping system referred to will have the following meaning. Flow Mains and Flow Risers. — The flow mains and flow risers are those portions of the piping system which carry hot water from the boiler to the radiator. The word flozv always refers to the hot side of the system. Return Mains and Return Risers. — The terms return mains and return risers refer to pip- ing which returns the cold water from the radiator to the boiler. Expansion Tank. — The expansion tank is a vessel partly filled with water and partly filled with air which allows for the variation of the volume of water in the system with the changes of the tem- 158 Notes on Heating and Ventilation perature of the water. In the open tank system this tank is situated at the highest point of the system. In the closed tank system it may be lo- cated anywhere in the building. TABLE XXII. Proportion of Cast Iron Hot Water Boilers. c O T3 b4 a> ■*- C -*-> oj !2 a .2 5 T3 to 0« ?ff)ff}?>>f}ffff>f?fI}>}}>>I>>}?>}>??f>/>fM/))}ff^^}I}I>>f>I>f>?}>JH>>})>»»»)J»»}>f}}}>. •aasSi r^jtjfj)jj>>)ij)j)}i J Figure 55. In rooms for restaurant purposes, where smoking is allowed or in smoking rooms or in kitchens, the air must be taken off the ceiling, as the foul air, Notes on Heating and Ventilation 185 being warmer, rises to the ceiling. In this case it is necessary to bring the ventilating air in at the baseboard, at a very low velocity and at a large number of places and take the air out at definite points near the ceiling, as shown in Fig. 55. In theaters and churches special means must be em- ployed for securing ventilation. It is customary to admit the air in a large number of places. Some- times this is done by means of a large number of small registers placed directly under the seats. Care, however, must be used in doing this to avoid drafts. Another method is to employ a large num- ber of openings around the sides of the room. The air is usually taken ofif near the stage at the lowest point in the auditorium. There should be provided in all auditoriums some means of taking the air off the ceiling, as oftentimes the heat given off by the occupants of the room is more than sufficient to heat the room, and in addition we have the heat given off by the sources of illumination. This heat can be best taken care of at the ceiling line, which is naturally the warmest point in the room. CHAPTER X. DESIGN OF HOT AIK HEATING SYSTEM. In a hot air furnace the cold air from the outside is passed over heated iron surfaces, usually en- closed in galvanized iron or Design of Hot Air brick walls. The space be- System. tween the walls and hot sur- faces of the furnace is con- nected to the outside air at the bottom and at the top to the flues leading to the rooms. The amount of air circulating through the furnace will depend upon the temperature of the hot air leaving the furnace and the height and resistance of the flues. In order that the air in a room may be quickly replaced by w^arm air it is necessary that the room be provided with a foul air flue. A great many of the difficulties that have been experienced with the hot air system as ordinarily installed are due to the sharp competition in busi- ness, which has resulted in the erection of plants of inferior workmanship and design. One of the commonest mistakes is the installation of a furnace much too small to do the work properly. The result of putting in a small furnace is that the fire must be continually crowded so that the heating surface is at high temperature and a large amount Notes on Heating and Ventilation 1^7 of the heat of the coal is wasted in excessive stack temperature. The hot air system with natural draft should not be used in houses where the horizontal por- tion of the hot air flues would exceed 20 feet in length. In very large houses two or more furnaces may be used to avoid excessive pipe resistance. Hot air furnaces are as varied in types as are steam boilers. They are made either of cast iron or steel. It is difficult to de- cide between the merits of Hot Air Furnaces, these two materials. Cast iron is less liable to be rapidly deteriorated by rust when the boiler stands in the summer, but it is more easily broken either by misuse or shrinkage strains in the castings. There is no essential differ- ence between the metals in their conducting ca- pacity as applied in these furnaces. It is very important to see that the furnace is so constructed that the joints between the fire-box and hot-air chamber are tight, so that the air en- tering the rooms may not be mixed with gases of combustion. This is one of the most difficult things to prevent in the hot air furnace. Joints should be as few as possible and vertical joints should be avoided. The introduction of moisture into the air passing through the furnace is an important consideration and will be treated in a separate para- graph. 188 Notes on Heating and Ventilation The builders rate their furnaces at about their maximum capacity. The rating being expressed as the number of cubic feet of building volume the furnace will heat. In selecting a furnace it is wise to have 25 to 50 per cent excess capacity in the fur- nace over the builder's rating. In the hot air furnace we have the fire and hot gases on one side of the shell and air on the other side of the shell. Air being a poor medium for the conduction of heat it is essential to economy that a hot air furnace should have large heating surfaces in proportion to grate area. The best manufac- turers allow from 50 to 70 square feet of heating surface per square foot of grate surface. A furnace should be provided with some form of shaking and dumping grate which is easily cleaned. In addition to draft doors admitting air below the grates, the furnace is usually provided with a check damper in the smoke pipe. The draft door and check damper are arranged so that they may be controlled by chains situated in some con- venient point in the room above. It is very important that air after being heated by the furnace pass over the surface of a pan of water so that it can Necessity of Supplying Mois- take up moisture. One ture to Heated Air. pound of air at 2)^'' F. will hold in the form of a vapor .003 of a pound of water, and at 150 de- Notes on Heating and Ventilation 189 grees it will hold .22, or about 70 times as much. If then we take air saturated with moisture at an outside temperature of 32 degrees and heat it up to 150 degrees we have increased its capacity for moisture 70 times. On entering the rooms if the air has not been given opportunity to take up mois- ture it will take it up from the objects in the room. This drying effect of the air injures the furniture and woodwork and affects the persons occupying the room, producing a dry throat and a feeling of cold due to rapid evaporation from the skin. The usual method of overcoming this is to have a pan filled with water situated in the furnace near the fire-box. This, however, is the wrong end of the furnace to place the pan, as the air entering is coolest at this point. The water should be added to the air as it leaves the furnace. In some hot air installations every pipe leaving the furnace has a trough in it, which is filled with water, and from this water the air takes up its moisture. The cold air supplied to the furnace is usually taken from one of the basement windows and brought to the furnace through a tile or w^ooden Cold Air Duct, duct lined with galvanized iron ; where a tile duct is used it is placed below the level of the cellar floor. The cold air should be taken from the side of the house that is subject to the prevailing winds. It is sometimes desirable to 190 Notes on Heating and Ventilation have cold air ducts leading to different sides of the house, so that the supply of cold air may be taken from the windiest side. It is well to provide some means of recirculation of the air in the house through the furnace. The air for recirculation is usually taken from the hall. If it is desired to recirculate partially and take the balance of the air from outside, the recirculating pipe should be brought to the furnace separately, and a deflecting plate placed in the air space under the furnace. If this is not done the air will come in from the outside and pass up the recirculating pipe instead of going to the furnace. If, however, the recirculating pipe is only to be used when the cold air pipe from outside is closed, then the re- circulating pipe can be conducted into the cold air pipe directly. In this case the cold air pipe and recirculating pipe must both be provided with dampers. The cold air pipe should have at least three-fourths of the combined areas of the hot air pipes. It is a common error to make the recirculating pipe of a furnace system too small. The recircu- lating pipe should be not less than three-fourths the area of the cold air pipe. It is better to have it equal in area to the cold air pipe. The furnace should be centrally located, or if the Notes on Heating and Ventilation 1^1 coldest winds come from a certain direction, it can be located more on that side of the house from which the Hot Air Flues, cold winds come. The hot air flues leading from the furnace should be as short and direct as possible ; long horizontal pipes should be avoided. Horizontal pipes should pitch sharply towards the furnace, three-quarter inch to the foot is good practice. All hot air pipes should have nearly equal resistance to the passage of the air. The hot air flues should have as few and as easy turns as possible. They should never be placed in the outside walls. Uptake flues of any kind in out- side walls seldom draw satisfactorily. The hot air flue should enter the room in most cases opposite the largest exposed glass surface or some distance from it. The circulation of air in the room would be best if the hot air entered near the ceiling. The principal objection to this is that the registeY in the wall is apt to blacken the wall and it does not allow people to warm themselves over it. Floor regis- ters are very objectionable as they always serve as receptacles for all kinds of rubbish and sweepings. Dampers should be provided in all pipes leading to rooms above the flrst floor. If all the registers are provided with dampers there is danger of burn- ing the furnace, due to shutting oft all the passages for removing hot air and preventing circulation in the furnace. It is good practice to have no valve 192 Notes on Heating and Ventilation in the hall register so one pipe will always be open. The velocity of air for first floor pipes may be calculated as three to four feet per second, second floor four to five feet per Proportions of Hot Air second, third floor and floors Flues. above five to six feet per second. The registers should be proportioned so as to give a velocity of two to three feet per second on the first floor and three to four feet per second on the floors above. The effective area of the ordinary register is about 50 per cent of the actual area, taking outside dimensions. H. B. Carpenter, in a paper before the Society of Heating and Ventilating Engineers (Transac- tions, vol. 5, p. "jy), gives the following rule for finding the cubic feet of air passing through pipes per minute : To the first floor multiply the area in inches by 1.25. To the second floor multiply the area in inches by 1.66. To the third floor multiply the area in inches by 2.08. It is good practice to figure on changing the air in the principal rooms five times per hour in hot air heating. The foul air flues should be placed in the inside Notes on Heating and Ventilation 198 walls and with foul air registers at the baseboard. The reason being that the hot air entering the room Foul Air Flues, opposite the window sur- faces rises to the ceiling, passes along the ceiling to the windows and is cooled. It then drops to the floor line, passes along the floor and out the foul air register. The hot air register should be a suf- ficient distance from the foul air register so that the hot air will not pass directly to the foul air flue. A cheap foul air flue can be made by having a reg- ister in the baseboard opening into the spaces be- tween the studs, selecting a space that is open to the attic, a ventilator is placed on the attic space and discharges foul air out of doors. No two rooms should open into the same studding space. A still better draft can be produced by extending each flue separately by galvanized iron pipe to the ventilator. If no ventilating flues are provided, it is very diffi- cult, especially if the house is tight, to get a proper circulation of hot air from the furnace ; you cannot put hot air into a room if there is no provision for taking cold air out. A fireplace makes one of the best forms of foul air flue. In a house well provided with fireplaces, it is often not necessary to provide any other foul air flues. The size of the hot air flue, vent flue, hot air 194 Notes on Heating and Ventilation register, heating surface and grate surface in the furnace is given in Table General Proportions of ^wt o-i • ^ t^i • Hot Air System. ^^^^' ^his table is given for rooms of average pro- portion and under average conditions. Table XXXI — Proportions of Hot Air Heating System. Contents of Room ix Cu. Ft. 500 1,000 1,500 First Floor — Diameter hot air flue, in 6 8 9 Diameter foul air flue, in 8 9 Second P'loor — Diameter hot air flue, in 6 7 S Diameter foul air flue, in 6 8 9 Grate area in furnace, sq. in 25 50 75 Heating surface in furnace, sq. ft.... 10 20 30 2,000 2,500 3,000 3,500 4,000 5,000 6,000 8,000 10,000 10 11 12 13 14 16 17 20 '24 10 11 12 13 14 16 17 20 24 9 10 11 11 12 14 15 18 20 10 11 12 13 14 16 17 20 24 100 125 150 175 200 250 300 350 400 40 50 60 70 80 100 125 160 200 The following assumptions have been made in the above table : Temperature outside air, o de- gree ; temperature of air in the room, 70 degrees ; changes of air in the room, three times per hour. Velocity of air in hot air flues, ist floor, 3 ft. per second. Velocity of air in hot air flues, 2nd floor, 4 ft. per second. Velocity of air in foul air flues, istand 2nd floors, 3 ft. per second. Notes on Heating and Ventilation 195 Temperature of air entering the room, i6o de- grees. Proportion of grate surface to heating surface, i to 60. Pounds of coal burned .per square foot of grate surface per hour, 2.5. The temperature of the rooms should be regulated by the drafts of the furnace as much as possible. The heating surfaces of the furnace should never Suggestions for Operating be brought to a red heat. Hot Air Furnaces. If it is necessary to do this to keep the rooms warm, the furnace is too small. Ashes should be frequently removed from the furnace, as an accumulation of ashes may burn out "the grate. Never shake the fire more than is neces- sary to expose the red coals to the ash pit. The furnace should be cleaned at least once a year. The water pan of the furnace should be kept full of water. ROUGH RULES FOR HOT AIR SYSTEM. . I. The volume of the house divided by 50 equals square feet of heating surface in furnace radiator. 2. The volume of the house divided by 20 equals the number of square inches of grate area in the furnace. 3. Divide the volume of the room by 20 and the square root of the quotient wall be the diameter of 196 Notes on Heating and Ventilation the furnace pipe for the first floor room. For sec- ond floor rooms divide the volume by 25 and the square root of the quotient will be the diameter of the furnace pipe. As an example of the hot air system applied to the ordinary dwelling, take the same house that was used as an example of di- Example of Hot Air rect steam heating. The System. heat lost from the rooms would be the same as in the case of direct steam. As an example of an in- dividual room take the parlor. From Table XII we see that the volume of the parlor is 1,665 cubic feet and the heat lost 10,395 B. T. U's per hour. In figuring the heating system for the parlor the following assumption will be made: The hot air enters the room at 160°. Cold air enters the furnace at 0°. The temperature in the room is 70°. Then the air entering the room is reduced in temperature 160 — 70^=90°. Each pound of air on having its temperature reduced 90° would give up .2375X90=21.4 B. T. U's. Then there will have to be introduced into the room to supply heat lost from the room 10,395-^21.4=485 pounds of air per hour. At atmospheric pressure a pound of air occupies approximately 13 cubic feet, hence 485 pounds of air is equal to 6,300 cubic feet. This is the amount of air which must be delivered to the room per hour; 6,300 cubic feet of air per hour is Notes on Heating and Ventilation 197 equal to 1.75 cubic feet per second. Allowing a velocity of 3 feet per second, the area of the pipe would be i.75^-3=.58 square feet, which is equiva- lent to 84 square inches, or approximately the area of a pipe 10.5 inches in diameter. To warm the First Floor. Parlor 1,665 10,395 18,500 6,300 10 Vg Sitting room 2,100 7,035 12,500 4,350 9 Dining room 1.640 7,350 12,800 4,500 9 Kitchen 1,610 10,300 18,000 6,250 IO1/2 Hall 1,210 7,035 12,500 4,350 9 Second Floor. W. chamber 1,320 10,050 17,900 6,200 9 Alcove 810 7,560 13,400 4,750 8 S. chamber 1,560 7,035 12,500 4,400 8 N. Chamber 1,440 7,455 13,300 4,650 8 Bath 410 3,150 5,600 1,850 6 E. chamber 880 5,250 9,400 3,300 7 Halls 88 2,730 4,800 1,750 6 151,200 air going to the parlor would require 485 X -2375 X 160=18,500 B. T. U's. In a similar way the same quantities have been calculated for the other rooms. Except that for the second floor room, a velocity of 4 feet per second has been allowed. Column 3 of Table XXXII shows the heat which is left by the air in the room. Column 4 shows the 198 Notes on Heating and Ventilation heat used to warm the air entering the room. The difiference between these two cohimns is the heat lost up the ventilating flues. This loss should not l^'W** Figure ."iO. be charged against the hot air furnace, but should be considered as the loss that nnist be charged to ventilation. The loss is about 44 per cent if the Notes on Heating and Ventilation 199 temperature of the outside air is at o° and the tem- perature of the air entering the room is 160'^. As the temperature of the outside air or the incoming air is increased proportionately more heat enters the room and this loss becomes less. During the average winter weather the outside air is 35°, in which case the per cent of loss by ventilation, that is, through the ventilating flues, is about 30 per cent. Summing up column 4 of the table gives the heat required to warm the air entering the entire house in zero weather or 151,200 B. T. U's. If we assume that 80 per cent of the coal goes into the heated air, then there will be required from the coal 151,200-^ .8=188,500 B. T. U's per hour. A good anthracite coal contains about 13,500 B. T. U's; then in zero weather this house would use 1 88, 500-f- 13,500=14 pounds of coal per hour. As the average loss from a house during the heating season is approximately 50 per cent of the loss during zero weather, the A\'erage consumption of coal in this house for the heating season would be i4X.5^7-00 pounds of coal per hour. Assuming the furnace to be oper- ated 24 hours per day and 200 days per year, the coal consumption for this house would be 7X24X 200-^-2,ooo-=i6.8 tons. Fig. 24 shows a cross sec- tion of a house with the hot air system installed. CHAPTER XI, FAN SYSTEM OF HEATING. Where it is necessary to introduce large quanti- ties of air into a building for the purpose of venti- lation a natural system of circulation is out of the question and it is necessary to force the air into the building by some mechanical device. This is usually done by means of a steel plate blower which delivers the air with sufficient pressure to force the air into all rooms in the building. The pressure required in the average building does not usually exceed one- quarter ounce. The mechanical system of ventila- tion has the additional advantage that its operation is entirely independent of the heating of the build- ing: and the building mav be ventilated as easily in the summer as in the winter. The natural system of ventilation depends entirely upon the air in the flues being heated, and during the summer periods the system is inoperative. There are two general schemes of fan heating, one in which the air is heated to a temperature higher than that in the Systems of Fail Heating, room, so that it furnishes enough heat to supply the heat lost from the walls and windows, as well as to Notes on Heating and Ventilation '^01 furnish air for ventilation. In the other system the heat loss from walls and windows is supplied by direct radiation situated in the room and the fan supplies only the necessary amount of air for venti- lation. In the latter system the air for ventilation is supplied at about the temperature to be main- tained in the room. The first system, in which all the heat is supplied by means of a fan, is most ap- plicable in buildings that must be heated and venti- lated both night and day. Hospitals and asylums are buildings of this class. It has certain disad- vantages, however. When a room lias very large glass surfaces it is almost impossible with this sys- tem to prevent strong cold drafts coming down along the window surfaces. The system is in many cases wasteful. In order to heat a building it is often necessary to admit more air than is required for the purpose of ventilation, and all the heat put into the air to raise the temperature of the out- side air to the temperature of the room is lost. On the other hand, this system requires but one system of heating, which makes it less expensive to install. The second system mentioned, where direct ra- diation and a fan are both used, is most applicable in buildings that require ventilation only part of the time. Schools, factories, oflfice buildings are build- ings that may be included in this class. While the buildings are filled with occupants the fan system is operated; as soon as the occupants leave the build- 202 Notes on Heating and Ventilation ing the fan system is closed and the building kept warm by means of direct radiation. The building is thus kept warm at a minimum expenditure for fuel. There is no necessity of introducing into the building more air than is necessary for ventilation. But the system is expensive to install, as it involves installing two separate systems of heating. This system is being more and more favorably consid- ered, however, in connection with the class of build- ings mentioned. The usual arrangement of the fan system is shown in Fig. 57. The air is drawn first through a series of tempering coils General Arrangement of shown at A. Then it enters the Fan System. a tempered air chamber in which is located the fan. This delivers the air through a series of heating coils B into the hot air chamber. From this hot air chamber the individual rooms in the buildings take their heat. The tempered coils are usually designed to heat the air to about 70°. The fan takes this air at 70° and passes it to the heating coils. After leaving the heating coils the tempera- ture of the air is from 130° to 140°. Where the air is used for ventilation only the heating coils are omitted and the air is delivered by the fan from the tempered air chamber directly to the room. The quantity of air to be supplied to each room Notes on Heating and V^entilation 203 will depend upon the system of heating employed. If the heating is done en- tirely by fan enough air Quantity of Air to Be must be admitted so that the Supplied, heat left by the air will be sufficient to heat the room. In audience and school rooms the amount of air necessary to supply proper ventilation is usually sufficient for heating. In of- Figure 57. fices and living rooms more air will have to be sup- plied in order to heat the room than would be neces- sary for purposes of ventilation. Roughly speak- ing, if the number of cubic feet of air supplied to the room per hour is four times the cubic contents of the room the room wtU be heated, providing the air be supplied at not less than 140°. In a system where direct radiation is used to supply losses from '^0.4 Notes on Heating and Ventilation walls and windows only enough air is introduced to supply the necessary ventilation. The amount of air necessary can be determined by rules pre- viously given under the head of Ventilation. In most cases the type of fan known as the steel plate blower is best adapted to the w^ork of fan heating. The theory of this Size, Speed and Horse- fan has been discussed by power of Fan. Weisbach and Lindner in their treatises, also by vari- ous writers in the Transaction of the Society of Heating and Ventilating Engineers. The results derived are difficult of application. The following general statement may be made, however. The discharge capacity of a fan depends upon the speed of the fan tips, the size of the fan blades, and the size of the discharge openings. As the discharge opening of the fan is decreased the velocity of the air leaving the fan increases and the pressure of air in the fan case increases until we get to the maxi- mum pressure that can be produced by a certain velocity of fan tips. This will occur when the area of the outlet equals the effective area of the fan blades. This is the point at which the fan delivers the maximum amount of air corresponding to the pressure for a given speed. If we further reduce the discharge outlet the pressure in the fan case remains constant, the quantity of air discharged is reduced and the power to drive the fan is reduced. Notes on Heating and Ventilation 205 The theoretical relations connecting the pressure of the air, the quantity of the air delivered, power Table XXXIII — Fan Capacities. Speeds, Capacities and Horse Powers of ''A B C' Steel Plate Fans of Varying Revolutions. R.P.M. FAN 60 60 70 80 90 100 110 120 140 160 180 200 220 240 PerV, 785 942 1100 1257 1414 1571 1728 1885 2200 2513 2837 8141 3455 8769 AirV. 685 820 957 1092 1230 1367 1503 1640 1,P15 2182 2459 2732 8005 8279 100 Pres. .017 .025 .034 .044 .0,55 .068 .082 .100 .134 .175 .231 .273 .385 .401 Cu. Ft. 682 1121 1,870 2652 3840 5475 6395 9565 14916 21750 80221 4t608 55201 71941 H. P. .150 ;222 .370 .476 .672 1.01 1.37 2.03 3.46 5.47 7.7 12.0 17.1 25.1 Per V. 981 1178 1375 1571 1768 1964 2160 2356 2750 3141 8533 3926 4318 4711 AirV. 853 1025 1196 1366 1538 1707 1879 2029 2390 2724 3073 3415 8756 4098 125 Pres. .027 .089 .053 .060 .039 .108 .132 .153 .212 .276 .350 .435 ..525 .626 Cu. Ft. 852 1402 2338 31.58 4809 6844 7992 11945 18645 27170 87767 52010 68997 99910 H. P. .175 .284 .439 .588 .934 1.34 2.06 2.90 5.00 8.15 12.5 19.3 29.2 43.5 PerV. 1177 1413 1650 1886 2121 2356 2592 2827 3S0O 3770 4240 47U 5182 5653 Air V, 1025 1230 1432 1640 1845 2044 2255 2460 2870 3280 3688 409a 4500 4928 150 Pres. .039 .056 .075 .100 .180 .160 190 .230 .800 .400 .503 .626 .758 .904 Cu. Ft. 1023 1681 2805 3979 5760 8110 »S0 14360 22374 32610 45325 62412 82811 10812C H. P. .200 .325 .531 .756 1.27 1.86 '2.34 3.£0 7.22 11.3 19.6 32.1 46.2 68.6- PerV. 1374 1649 1925 2200 2474 2749 3024 •3297 38.50 4380 4947 5496 6046 6596 AirV. 1195 1434 1674 1914 2152 2390 2630 2868 3S50 8826 4303 4781 5260 574? 175 Pres ;053 .076 .104 .134 .172 .212 .258 .^06 .420 .554 .687 .848 lj02 1.21 Cu Ft. 1194 1962 3274 4622 6729 9594 11200 16715 26100 38043 52883 72814 96626 126089 H.-P. .225 .393 .647 1.01 1.74 2.46 3.55 5.52 9.91 17.3 27.9 44.2 67.1 103.0 PerV. 1570 1884 2200 2511 2828 3142 3456 8770 4400 5026 56.54 62^ 6910 7538 AirV. 1366 1640 1915 2187 2460 2737 3007 3280 38S0 4375 4918 5465 6011 6558 200 Pres. .069 .101 .1.34 .175 .?i5 .274 .333 .392 .537 .700 .f03 1.12 1.34 J159 Cu. Ft. 1364 2242 3740 5304 7690 10960 12830 19150 29850 43520 •60442 83331 110422 143902 HP. .262 .478 .855 1.26 2.05 3.16 4.69 7.01 13.3 23.7 39.2 62.1 96.6 154.5 Per V. 1766 2120 2475 2829 3182 3534 8888 4241 4950 5654 6360 7065 7774 AirV. 1536 1844 2153 2459 2767 S073 3383 8688 4305 4919 5533 6148 6762 225 Pres. .037 .126 .172 .225 .285 .351 .421. .507 .690 .601 1.14 1.41 1.60 Cu. Ft. 1534 2523 4207 5969 8655 12334 14385 21500 33560 48680 68000 93634 124217 H. P. .300 .581 1.03 1.57 2.61 4.09 5.95 9.29 17.0 31.1 52.8 87.9 142.5 PerV. 1963 2355 2750 3143 3535 3927 4320 4712 5.500 6283 7067 7852 Air V, 1708 2048 2392 2734 8070 3416 37.58 4100 4780 54.50 6148 6840 250 Pres. .109 .056 .213 .280 ..360 4.30 .520 .630 .860 1.12 1.48 1.73 Cu. Ft. 1706 2793 4675 63.32 9600 13705 16000 23950 37310 5420O 75558 104036 H. P. .375 .684 1,22 1.79 3.32 4.97 744 11.6 22.5 41.2 71.7 121.4 PerV. 2159 2.591 3025 3457 3889 4319 4731 5183 6050 6911 7774 AirV. 1878 22.58 2632 3008 3383 3755 mo 4.507 5263 6013 6763 275 Pres. .131 .189 »258 .337 .426 .526 .623 .7.56 1.04 1..35 1.71 Cu. Ft. 1876 3083 5142 7294 10578 15773 17394 26278 41020 58328 83104 H. P. .436 .821 1.45 2.35 3.92 6.09 9.09 14.5 29.4 54.7 89.3 PerV. 2355 2826 3300 3771 4242 4712 5184 5654 6600 7539 AirV. 20.50 24.58 2875 3280 3685 4100 4510 49E0 .5745 6555 300 Pres. :160 .'^25 .302 .401 ..520 .630 .760 .910 1.26 1.62 Cu. Ft. 20 »6 3363 5610 7957 11520 162.50 19200 28800 44750 63629 H. P. .500 .975 1.73 2.86 4.63 7.44 11.4 181 37.5 69.3 PerV. 2747 3297 3850 4399 4949 5447 4770 6018 6597 7700 AirV. 2390 2863 3345 3827 4-295 ^262 5724 6680 NOTE 850 Pres. .216 .306 .418 .550 .693 .8.50 .970 1.25 1.68 These figures guaraiiteed to Cu Ft. 2387 3923 6545 9282 13410 19110 22395 33400 52206 H. P .663 1.28 2.38 3.89 6.65 10.7 17.2 28.3 55.8 be correct with the resistance PerV. 3140 3768 4400 5028 5656 6282 6912 7540 ordinarily found in heating AirV. 2732 3278 3830 4374 4926 .5470 6013 6560 work. 400 Pres. .277 .399 .546 .713 904 1.14 1.42 163 Cu. Ft. 2729 4384 7480 10620 15400 219.50 25574 38300 H. P, 750 170 3.19 5.04 9.S4 15.3 25.2 39 2 206 Notes on Heating and Ventilation to drive the fan and the speed can be stated briefly as follows : The quantity of air delivered is pro- portional to the peripheral velocity of the fan tips and to the area of the fan tips. The pressure pro- Table XXXIV — Fan Efficiency Under Varying Pressures. Speeds, Capacities and Horse Powers of "A B C" Steel Plate Fans of Varying Pressures. PRESSURES. Hot- H oz. Koz. 1 oz. IH oz. IH oz. IKoz. 2 02. 2!4 oz. 3 oz. 50 CU. FT. R. P. M. H, P. 2740 »S0 .80 3900 .540 4760 659 2.66 5490 760 385 6090 847 5 32 6700 9:^0 6.65 7350 1004 8.22 7750 1075 10.25 8650 1200 14.38 9520 1320 18.85 60 CU. FT R. P. M. H. P. S.i.'iO 317 1.03 5040 449 2.05 7350 383 3.02 5490 549 3.42 7100 4.95 7910 706 6.84 8700 776 8..54 9410 838 10.6(> 10200 895 13.2 11210 1000 18.45 12330 1100 24.3 70 CU. FT. R. P. M. H. P. 5220 271 1.51 630 238 1.82 7850 211 2.27 90.)0 471 5.04 10400 .542 7.30 11600 605 10.10 12700 663 12.80 13750 716 15.60 147.50 768 19.40 16.500 857 27.20 18000 938 85.7 80 CU. FT. R. P M. H. P. 8800 S36 3.65 10940 412 6.08 125.50 474 8.82 14000 12.15 15350 580 15.20 16600 627 18.85 17300 672 23.40 19890 . 750 saf.80 21920 825, 43.2 90 CU. FT. R. P. M. H. P. 11050 299 4.53 13600 366 7.56 15600 421 11.00 174.50 470 15.10 19100 515 18.90 206.50 557 23.40 22100 596 29.10 247.50 666 40.70 27300 734 53.5 100 CU. FT. R. P. M. H. P. a-uo 190 2.76 13.500 268 5.52 16500 329 9.20 19050 380 13.35 21300 424 18.42 23200 464 23.00 25200 502 28.60 27000 537 35.10 30500 600 49.60 33000 659 65.2 110 CU. FT. R P. M. H. P. 11870 173 3.43 15030 159 4.32 19800 i:« 5.72 .250-)0 118 7.29 16700 244 6.85 20600 300 11.44 23600 345 16.60 26400 885 22.J,0 28900 422 28.60 31300 4r)6 35.50 33500 488 44.00 37500 546 61.7 41200 600 81.2 120 CU. FT. R. P. M. H. P. 21000 224 8.65 2.5840 274 14.40 29700 316 20.t0 33200 3.54 28.80 36400 387 36.00 39400 418 44.60 42200 448 55.45 47100 .500 77.7 51800 5.50 102.1 140 CU. FT. R. P. M. H. P. 27900 192 11.42 34200 2:» io.oo 39400 271 27.60 44000 302 38.10 48200 331 47.60 51200 357 59.00 55800 88;i 73.30 639C0 43<.l 1027 68400 470 1S5.5 160 CU. FT. R. P M H. P 35600 168 14.60 43700 206 24.32 50250 237 35.20 56150 265 48.60 61500 290 160.75 66500 314 75.20 71250 336 93.50 79200 373 134 87500 412 172.0 180 CU. FT. R. P. M. H. P. 31410 106 9.07 44200 149 18.13 54300 183 30.24 62700 211 43.80 69700 235 60.48 76700 259 75.5 82700 279 93.6 88400 298 116.20 9V000 S34 131.0 108400 966 214.0 200 CU. FT. R. P. M. H. P 38000 95 11.02 53700 134 22.20 66000 165 36.80 75700 189 53.3 849.50 212 73.5 93000 232 92.0 loaioo 251 114.0 107':00 268 141.5 120000 300 198.5 134000 390 261.0 220 CU. FT. R. P. M. H. P. 46800 87 13.48 66300 1-23 27.00 80600 150 44.90 93200 173 65.10 104000 193 89.6 113500 211 112.0 1-28300 229 139.0 131400 244 173.0 147100 274 243.0 161500 300 818.0 240 CU. FT. R. P M. H. P. 56400 80 16 10 79000 112 32.30 96.500 137 .5:j.mo 112000 159 7S00 124800 177 107 4 i:i8S00 194 1:m.O 147400 209 1660 1.58000 ?-'4 206.0 176100 250 290.0 194000 275 S82.0 Notes on Heating and Ventilation 207 duced is proportional to the square of the peripheral velocity of the fan tips and the power necessary is proportional to the cube of the peripheral velocity of the fan tips and to the quantity of air delivered. Mr. M. C. Huyett gives the following approxi- mate rule for finding the capacity of a fan : The quantity of air in cubic feet delivered per revolu- tion is equal to one-third the diameter of the fan wheel multiplied by the width of the blades at cir- cumference, multiplied by the circumference of the fan wheel. All dimensions expressed in feet. Professor R. C. Carpenter gives the. following rule for determining the horsepower required by the fan : The horsepower required for the fan is equal to the fifth power of the diameter of the fan wheel in feet multiplied by the number of revolu- tions per second, divided by 1,000,000 and multi- plied by one of the following coefficients — for free delivery, 30; for delivery against i-ounce pressure, 20; for delivery against 2 ounces pressure, 10. The best method of obtaining the horsepower to drive a fan and the capacity of the fan is by reference to the blower companies' catalogues. Some companies have published catalogues which are obviously wrong. At the present time, however, the Ameri- can Blower Company, of Detroit, have published in their catalogue tables that are very satisfactory. Table XXXIII gives the speed, capacity and horsepower required for various sized fans. 208 Notes on Heating and Ventilation Table XXXIV gives similar results for dififerent sized fans at varying pressure. The table should be made use of in the following manner : Having determined the quantity of air required for the entire building, we select from the table a fan which would give the proper capacity. In doing this three things must be considered. The fan must have sufficient capacity to deliver the amount of air recjuired. It must deliver this air with the minimum horsepower, and it must rotate with sufficient speed to produce a pressure in the fan system sufficient to overcome the resistance of the piping. It is always possible to select either a small fan driven at a high speed or a large fan driven at a low speed, both of which will deliver the same capacity of air. A large fan may be driven at so slow a speed that it will not produce sufficient pressure to overcome resistance of the air flues. Choose the largest fan that, driven at sufficient speed to overcome the resistance of the air flue, will deliver a proper quantity of air for the pur- pose of ventilation. As an example: Suppose we wish to deliver to a building 10,000 cubic feet of air per minute. Referring to the table, we see that we may use an 80-inch fan driven at 400 revo- lutions, in which case there would be 'required 5 horespowers to drive the fan and the pressure pro- duced would be .713 ounce. Or we might use a 120-inch fan driven at 125 revolutions per minute, Notes on Heating and V^entilation 2^9 in which case the power required to ch'ive the fan would be 2.9 horsepowers and the pressure pro- duced would be .153. In the first case the fan is small and being driven at high speed the pressure produced is far more than necessary to overcome the resistance requiring an excessively large horse- power to drive it. In the case of the 120-inch fan, while the horsepower is much lower the pressure is insufficient to overcome the ordinary resistance. For ordinary purposes the pressure should be about .25. Referring again to the table, we see that the 100-inch fan driven at 200 revolutions per minute would require 3.15 horsepow^ers and produce a pressure of .274. This would be about the proper size of fan to select. The pressure required to over- come the resistance of the building depends very largely upon the capacity and design of the flues and the resistance of these flues is largely a matter of judgment and experience. The determination of the proper quantity of heat- ing coil to raise the air to a given temperature will depend primarily Heating Coils. upon the amount of heat given ofif per square foot of heater coil. Table XXXV is obtained from the results of ex- periments made by the American Blower Company, of Detroit, and shows the condensation and heat given off by ordinary pipe heater coils under dif- ferent conditions. Knowing the heat given oflf Table XXXV Condensation and Heat Given Off by Heater Coils. a. c/) ^m , 4> O B 2 3 2 8 12 16 20 24 28 32 p. o o »i4 B 3 2 8 12 1« 20 24 28 32 TEMPERATURE AIR ENTERING COIL 0^-10° Velocity of Air 1000 feet per minute. o 2 Velocity of Air 1250 feet per minute. Velocity of Air 1500 feet per minute. Velocity of Air 1700 feet per minute. c o o o — **- '71 t/i I- c =» O ^^ u. E a» a 3 "^ —• b6 'y> C3 c ^ I- ._ 0) i» > u M c ? ^ C3 C O O O c/, (/5 C 2.E 2^ C3 2.9 1.78 1.53 1.31 1.20 1.10 1.05 74 94 114 130 143 152 2.37 2.1 1.86 1.68 1.54 1.45 1.40 65 2.56 60 2.72 82 2.32 77 2.45 98 2.09 93 2.25 115 1.88 108 2.05 128 1.77 122 1.92 140 1.70 134 1.85 148 1.65 140 1.77 55 73 88 103 117 129 133 TEMPERATURE AIR ENTERING COIL 40°-50^ Velocity of Air 1000 feet per minute. Velocity of Air 1250 feet per minute. Velocity of Air 1500 feet per minute. \'eIocity of Air 1700 feet per minute. __ _ ^ 18,, 4) -^ S S Oi o C O a> o £ o h C .2 o y) C O 75 u o O O tfl ensat uaref ound 2.E e — ^ T3 CO a» c '^ b 3 c rt 5 it 3 2 mperatu leaving degrees n ^ c c ^ ^ 5: 3 5 >eratu uaref grees rt a* c 5 3 ® T3 3- a c ? a7 T3 CT Cl •3 era c CT± T3 O- "• 5 '^' c E I' T3 C 75 £. E Tj-a c t/» c O •_ .3 f'^ u. O u .- •'** u. w a ,<1> ;- o «-.= U^ H.- 'J%. •"•JS ^^ ^J^ go 3 ^ 2.E e E -D 1.75 1.50 1.41 1.37 1.32 1.26 1.14 91 2.07 84 2.37 80 2.52 107 1.80 100 2.06 95 2.23 119 1.65 112 1.89 107 2.02 133 1.60 125 1.80 121 1.90 143 1.50 137 1.67 135 1.77 150 1.40 145 1.56 142 1.64 158 1.30 152 1.48 148 1.52 78 93 105 119 133 140 147 Notes on Heating and Ventilation 211 by the coil per square foot, under given conditions, the number of square feet of coil surface necessary may be obtained in the following manner : ^Multiply the air to be passed per hour by the difference be- tween the temperature of the outside air and the tem- perature of the air after passing through the coil. ^Multiply this product by .2375. Divide the re- sult obtained by 13.3, multiplied by the condensa- tion per square foot of surface per hour, multiplied by 966. Let C = condensation per square foot of coil ; A^ = volume of air in cubic feet passing per hour ; F = square feet heating surface coil should contain ; t --=^ temperature outside air ; t' = temper- ature of air after passing coil ; then P^ -^375V(t— t) "~ 13.3 X 966 c- In most cases the condensation in the tempering coils can be assumed at about 2 pounds per hour and in the heating coils about i^ pounds. In ex- treme cases condensation as high as 5 pounds per square foot per hour have been reported. After determining the number of scjuare feet of surface in the heater the heater must be so de- signed as to allow sufficient air area for the passage of air through the heater coils. The coils as ordi- narily arranged are shown in Fig. 58. Sufficient area should be allowed in these coils for the ve- locity of air passing. This should not exceed 1,200 feet per minute., except where coils are very large. 212 Notes on Heating and Ventilation Tempering coils should not be less than 12 pipes deep. If the heater coils are made very shallow the condensation in the coil is so rapid that in cold weather they will hammer. The heater coil consists of a cast iron base into which is screwed i-inch steam pipes jointed at the top by nipples and elbows. The cast iron base for Lin. Fii'ure 58. each section is provided with a steam ihlet and drip, both connected to the cast iron heater base. Alost bases are constructed for four rows of pipes. Table XXX\ I gives the principal dimensions of the American Blower Company's heaters with the size of fan regularly used. Within the last few years Cast Iron Heaters. cast iron indirect radiators suitable for use with fans have been placed on the market. Figure 59 shows a group of ten of these sections. They are easier Notes ox Heating and Ventilation 213 to handle in erection and less liable to rnst. The standard sizes on the market are 41 and 6o§/8 inches in length; both sizes are 9^4 inches deep and each section takes up a width of 5 inches. The 60-inch section contains 17 square feet per section and the 40-inch section 11^2 square feet. The sections are tapped 2^ inches and may be Table XXXVI- -Heater Dimensions. Lineal feet Size _,.Ac'ity Net 9 ii Reg- of fan. of 1-inch — Connections. space in ular Steel pipe. Steam. Drip. Bleeder. SCJ. ft. Disc. plate. 200 2" 1" %" 5.4 30 80 300 2" 1" %" 7.6 36 90 400 2" 1 V4" %" 10.7 42 100 525 2" 1 Vj " \" 14.3 48 110 650 O" IV," 1" 17.7 54 120 825 21/2 1V2" 1" 22.2 60 140 1.175 2V- 1 1/," 1" 31*. 72 160 1.525 3" ' 2// IV4" 40. 84 180 2,025 3" "2" ly^" 52.5 96 200 bushed to the proper size, depending on the num- ber of sections composing the radiator. Fig. 60 shows a curve of the steam condensation for these radiators with varying depth of coil and different velocities of air. Figure 61 shows the tempera- ture to which the air would be heated in passing- through these coils with varying depth of coil and dififerent velocities of air. The last two cuts are from the results given bv the American Radiator Co. 214 Notes on Heating and Ventilation The success of the fan system depends very largely upon the design of the flues. The best form of flue is round, the Ventilating Ducts. next best form is square, or, if rectangular,, as nearly square as possible. All turns and branches should Figure 59. be made with easy curves. The size of the flues is ordinarily determined by the velocity of the air passing in the flues. In main ducts of large size a velocity as high as 2,000 feet per minute or over may be used. In the branch ducts the velocitv should not exceed 1,000 to 1,500 feet. In flues Notes on Heating and Ventilation 215 Condensation Chart Incoming air, o° Fahrenheit. Steam pressure, 5 pounds 05 10 15 20 IT. 25 Ti P 30 ^ 35 c 40 45 u 50 X 55 60 ex 65 \, \ s s. \ \ V V \, \ \ s. \ \ \ S \, \ \ \^ \ V V ^. \ \ s^ \ S, k \ V s \, \ V \, \ \ N, N ^"i ^ N V N \. \ S \, ^ O- \ s. \ \ V ^ \, ~ \ \ S \, ^ \ s. \ \ s. S ^1 A. \ s s. \ s s. ^' '0. \ \ > \ V s \, % \ s. \ s V <;i ^ \ \ s. \ s. ^ 0. \ s V \, ^ s \, ^ ip. N V \, •^ ?* \ \^ ^ V S \, \ S^ V \, \ \, V \, :^ 500 600 700 -800 900 1000 1100 1200 1300 1400 1500 Velocity of Air Through Heater in Feet per Minute 1024 1072 1121 1170 1219 1267 1316 1365 1414 1462 1511 1560 1608 1657 1706 1755 1804 1852 1901 1950 1999 2047 2096 2145 2194 2242 2291 2340 2389 2437 2486 2535 2584 2632 2681 2730 3 O o 3 X o o 3 cr" Figure 60. 216 Notes on Heating and Ventilation leading to the individual rooms the velocity should be from 600 to 1,000 feet per minute, depending upon their size. Where the ducts are of small size Temperature Chart Initial air temperature, o° Fahrenheit. Steam pressure, 5 pounds 220' 210' 200/ 190/ 180/ 170/ .t 160/ ^ 150/ ° 140/ 4> e t— • C 5 o ""■^ t=j 1 1 H^^M ^^^ r: — 1 1 — F=] ^^ '^~ — »s^ =^ "^ ^•^ ^ ^ ^ psd p— 1 ^ --S - ' =4; 1 — ^ ^ ^ Ho, - - — =^ =^ r '-^ =^ - — \ •--^ —^ _— 1 p Hffl ^ 130" 120° 110° 100° 90° 80.° 70.° 60.° 50.° 40° 30.° 20° 10.° 0° 500. 600 7(X). 800. 900. 1000. 1100. 1200 1300. UOJ. 15iKJ. Velocity of Air Through Heater in Feet per Minute. Figure Gl. this velocity is often reduced to 400 feet per min- ute. The velocity at the registers should not exceed 300 feet per minute except in very large registers Notes on Heating and Ventilation 217 so located that the current of air entering the room will not strike the occupants of the room. In all ordinary buildings, if these proportions of air ve- locities are used the resistance of the system will be from two to three-tenths of an ounce pressure. In designing the ducts for a fan system short bends and tee branches should be avoided. The bends should be long and the branches made with Y's. The inside radius of the bend should be equal to the diameter of the pipe as a minimum and where conditions will permit, twice the diameter of the pipe. \Miere branches leave the main ducts it is a common practice to place a deflecting damper at the bend of the branch. This is merely a piece of galvanized iron attached to the point of the branch which may be adjusted and fastened so that each branch will take its proper supply of air. Dampers controlled by the attendants in the building should be as few as possible. The reductions in the size of a flue should be made gradually. The angle of the reduction should not exceed 30"^. Xo round pipes less than 6 inches in diameter are used, and if rectangular, less than 6x8. A common arrange- ment of ducts is to let them radiate from the fan in the form of a tree, with trunk and branches. This, however, makes the duct system very expensive and a system having large feeding mains similar to a system of steam piping is the one more used as it can be designed to give satisfactory results. An- 218 Notes on Heating and \^entilation other very satisfactory method of distribution is to force all the air from the fan into a large duct or chamber in which the air has a very low velocity. Table XXXVII— Pressure Losses. Air. — Loss of Pressure in Ounces per Square Inch per 100 Feet of ripe of Varying Velocities and Varying Diameters of Pipes. Velocity of Af» Feet per Minute. DIAMETER OF PIPE IN INCHES. Loss OF PreSSI'RE IK Ov.NfES- 600 1,200 1,800 2.400 8,000 8,600 4,200 4,800 6,000 .400 .200 .133 .100 .0*0 .067 .057 1.600 .800 .5:« .400 .3-20 .267 .22? 3.600 1.800 1.200 .»00 .720 .600 .514 6.400 3.200 2.133 1.600 1.280 1.067 .914 10.000 5.000 3.3.S3 2.500 2.000 1.667 1.429 14.400 7.200 4.800 3.600 2.880 2.400 2.a57 9.800 12.800 6..i.'>3 8..133 4.900 6.400 3.920 5.120 3.267 4.267 2.800 8.657 20.000 13.333 10.000 8.000 6.667 6.714 .050 .200 .450 .800 1.2^ 1.800 2.4.50 3 200 5.000 Velocity of Air Feet per Minute. DIAMETER OF PIPE IN INCHES 10 11 12 14 16 18 Loss OF Pressure i.n Olnces. 20 600 1,200 1.800 2,400 3,000 8.600 4.200 4.800 6,000 .044 .040 .036 .033 .029 .026 .022 178 .160 .145 .133 .114 .100 .089 400 .360 .327 .300 .257 .225 200 .711 .640 ..582 ..533 .457 .400 356 1.111 1.600 l.OQO 1.4^6 .909 1.309 .833 1.200 "".*900 "".'800 1.029 2.178 1.960 1.782 4.633 1.400 1.225 1.089 2.844 2.560 2.327 2.133 1.829 1.600 1.422 4444 4.000 3.636 3.333 2.857 2.50e 2.222 .020 OSD ISO .320 .720 .980 1.280 2000 Velocitj- of Air Feet per Minute. DIA.METER OF PIPE IN INCHES. 22 24 28 32 36 40 44 Loss of Pre.v^uke i.n Olnces. 48 600 1,200 1,800 2,400 8,600 4,200 4,800 6,000 .018 .017 .014 .012 Oil .010 .009 .073 .067 .057 .050 .044 .040 .036 .164 .156 .129 .112 .100 .090 .082 .'291 .267 .239 .200 .178 .160 .145 .6.55 .600 .514 .4.50 .400 .360 .327 .891 .817 .700 .612 .544 .490 .445 1.164 1.067 .914 .800 .71J .640 .582 1.818 1.667 1.429 1.250 i.m 1.000 .909 .008 .ats .075 .i:« .300 .408 .583 .883 Notes on Heating and Ventilation 219 The rooms take their air from this chamber by means of vertical flues controhed by proper dam- pers. These large chambers are called Plenum chambers. A good example of this is shown in the construction of the new Engineering building. Uni- versity of ?^Iichigan. In this building the corridor on the ground floor has a false ceiling about 3 feet below the second story floor. This leaves a space 3 feet high by 12 feet wide extending through the entire building. Into this space two separate fans Figure 62. deliver their air. The space acts as a Plenum chamber and the individual flues leaving the rooms take their air from this Plenum chamber through volume dampers which may be set and fastened after the proper position has once been determined. Table XXX\^II shows the loss of pressure per I GO feet of pipe for varying velocities and varying diameters of pipes. This table is quite liberal and allows for two ordinary 90° bends per 100 feet. Where the building is heated entirely by a fan 220 Notes ox Heating and Ventilation system it is necessary to devise some arrangement by which the room may be Air Mixing Systems. furnished with hot air or tempered air. In case the room becomes too warm, to close ofif the hot air register would do away entirely with ventilation and it is necessary to provide some means of intro- ducing tempered air. The method usually used is shown in Fig. 58. Wdiere each room is connected both to the warm air chamber and to the cold air passage, the dampers being connected so that when the warm air is turned ofif cold air is introduced into the room, or vice versa. In this case the mix- ing damper is located near the fan and preferably controlled automatically. Another system shown in Fig. 62 has entirely separate cold and hot air flues which are led to the base of vertical flues lead- ing to the rooms, at which point there is introduced a mixing damper similar to the mixing damper shown in Fig. 58. The flues for fan systems are ordinarily con- structed of galvanized iron with double lap joints riveted and soldered. The Materials of Flues. ducts should be made as nearly as possible air-tight. The weight of material used for ducts depends upon the size of the duct. It ordinarily varies from Xo. 26 to Xo. 16 gauge. Large ducts are also made of sheet iron with close riveting. When Notes on Heating and Ventilation 221 ducts are made of sheet iron the ducts are painted and then asphalted. Where it is necessary to build ducts underground they are built of brick or ce- ment. The cement, if anything, is preferable to brick, as it does not absorb odors as easily and may be plastered to make a smooth job. Where pos- sible it is desirable to build the ducts and flues into the building itself, making them of permanent ma- terial. Brick or cement ducts built into the build- ing and so arranged that they may be examined and cleaned easily are the most satisfactory. Wood is always a bad material to use for ducts and should be avoided. Where it is used the ducts are lined with tin, owing to the fact that wood usually shrinks, leaving open joints. \^ent ducts from closets should be carried out of the buildings separately from the other vent flues. Where these ducts are made of brick they should be lined with galvanized iron to prevent the odors from the closet being absorbed by the brick. It is very desirable that closet vents should be col- lected at convenient points and then exhausted from the building by means of a fan. This prevents the odors from the toilet rooms being carried back into the building. Disc fans are used where the resistance to be overcome is very slight or in cases where the ducts 222 Notes on Heating and Ventilation Table XXXVIII— Disc Fan Efficiency. Disc Ventilating Fan — Capacities, Speeds and Horse Pow- ers. (American Blower Co.) Are Veloc- ity IN Ft. PBR MlN. Size Fan 18 21 24 30 36 42 48 54 60 72 84 96 itiS 126 600 Free Cu. Ft. R. P. M. H. P. 1&60 327 .016 1440 280 .022 1880 245 .028 2940 196 04a 4230 165 • 064 5772 140 087 7536 122 "3 9540 110 143 1 1 770 98 •177 16960 82 253 23090 70 • 345 .450 38160 55 573 47160 so 706 Heater R. P. M. .H. P. 530 •053 453 072 .094 3»7 •'47 267 .212 227 .288 '97 •377 178 ■ 477 158 •59° .849 ir3 > 15 100 '•51 89 1. 91 81 2.3s 700 Free Cu. Ft. R. P. M. H. P. '235 370 .025 1680 328 ■035' 2200 280 .045 3400 230 .070 494° 190 .110 6730 J 64 •'36 8800 145 .178 11120 127 .227 43750 1 12 .279 19760 96 .402 26950 82 .548 35016 72 .740 44500 ■ 62 • 905 55000 58 I. It Heater R. P. M. H. P. 600 ,071 53° ■ .096 458 .126 .196 307 .283 266 .384 234 ■5°3 206 .636 i78 .786 158 I 13 132 '•54 n6 a. 10 JOO 2.52 92 3 14 800 Free Cu. Ft. R. P. M. H. P. 1410 435 .036 1920 373 048 2510 326 ,068 3820 262 098 5650 218 .142 7700 187 .192 10300 164 •25' 12710 145 • 3'7 15710 '3' •392 22600 no .562 30400 94 ,766 40150 83 1.00 50900 73 I 27 62800 66 '•57 Heater R. P. M. H. P. 705 .106 604 149 527 ..89 424 »94 353 .426 302 .579 265 .756 234 ■957 212 1.18 '78 '7' 152 2.32 134 3 20 118 3^83 107 4 73 900 Free Cu. Ft R. P. M. H. P. 1584 490 • 048 2160 425 06s 2826 36S .085 4410 285 '32 6354 246 .190 8650 210 •258 11304 184 .338 14310 164 .42b 17667 146 •53° 25443 .762 34642 106 1.04 45234 . 93 I 35 57250 82 1.72 70650 74 2.12 Heater R.P. M. H. P. 792 •143 770 •195 2400 470 .080 595 254 461 3" 7 398 • 572 340 .780 298 1 .02 265 1 .29 236 J 59 199 2.29 '73 3 '2 150 4.07 132 S15 119 6.36 1000 Free Cu. Ft. R. P. M. H. P. 1770 545 057 3HO 406 .104 4900 328 142 7060 275 ■233 9610 234 •3'7 12560 205 ■4'3 159C0 181 .520 19630 166 ■647 28270 136 •933 38480 120 1.27 50265 103 1.66 63600 9' 2.09 78540 82 2.56 Heater R. P. M. H. P. 883 .204 760 .276 657 362 53° .565 445 .814 378 I II 332 1 45 .293 '•83 2C8 2 .26 220 3 26 33900 164 1.62 194 4 44 167 577 .147 7 33 ■ 132 9 OS 1200 Free Cu.Ft. R. P. M. H. P. 2112 654 . lOI 2880^ 560 .138 ..3768- 490 .180 5880 398 .280 8472 33° .■405 "54' 280 ■ 550 15072 245 .716 19100 218 .910 23566 I96 '•'3 46176 140 2.20 60312 124 287 76300 110 3^63 94240 4.4S Heater R. P. M. H. P. 1059 .300 912 .409 .,788 534 636 •832 534 1 .20 1.64 .396 2.14 351 2.70 322 3 37 264 4.85 234 6.60 200 8.63 176 10.8 .160 '13 3 1400 Free Cu. Ft. R. P. M. H. P. 2475 767 •»33 3360 655 .180 4400 570 •235 6850 460 .368 9870 388 •53° 1347° 327 721 17600 286 .942 22270 254 ' '9 27500 230 '•55 39600 190 2.12 53900 164 •2.89 70300 144 , 3 77 88950 128 4 77 109500 5.89 Heater R. P. M. H. P. 1235 .487 1064 .660 919 .864 742 '■35 623 195 52S 2.64 463 3 46 410 4.38 376 5 4° 308 ,7-88 •' 274 10.6 234 '18 205 '75 184 21 .6 1600 Free Cu. Ft. R. P. M. H. P. 2830 875 .'85 3850 750 252 5000 656 .330 7810 526 •5'5 1 1300 438 •742 15400 375 1 .01 20050 332 '■34 25400 298 1.67 3.400 264 2 .06 45200 220 '2.97 61500 1 88 4.05 80000 16s 5.28 101200 .46 6.68 125200 8.25 Heater R. P. M. H. P. 1412 •735 1216 1 .00 1050 '3.' 848 2 04 712 2.94 603 4.00 537 5 23 468 6.62 429 8.17 352 II. 8 314 16.0 • 268 20.9 26.5 210 ■32 ■ 7 1800 Free Cu. Ft. R. P.M. H. P. 3170 980 .247 4320 840 336 5630 732 • 440 8850 69° .686 12700 490 .-•99' 17300 420 '•35 22600 368 1.76 28600 330 2.22 35200 294 2.75 51000 245 396 16.9 69000 210 J 39 354 23.0 90200 '85 •302 30.0 114000 141000 148 »i.o Heater r:p:m. H. P. T588 'OS 1368 « 43 1181 1.87 954 2 93 801 4 ■23 679 5 75 595 7.50 526 9.50 "483 11.7 263 38.0 236 47 2000 Free Cu. Ft. R. P. M. H. P. 3520 1090 336 4800 935 .456 6280 815 •597 9800 655 93' 14126 545 '•34 19^40 47° .83 a5'2o 410 2 39 31800 363 3 02 39260 327 3 73 56510 272 5 38 76960 234 7 3' 100520 206 9 55 127200 182 12. 1 157100 164 '4 9 Heater R. P. M. H. P. 1764 1.30 1520 '77 1312 2.30 1060 3.60 890 5 '5 755 7.05 664 9 25 585 11.7 528 '4 5 440 20,8 380 28. s 336 37 292 46.8 262 578 2200 Free Cu. Ft. R. P M. H P. 3890 1200 424 4300 1050 .576 6800 900 ■754 10800 720 I. 18 15520 600 1.70 21130 5'5 23' 27600 450 .3 02 35000 400 3 82 •43200 360 4 72 62200 300 6.79 84700 257 925 I 10500 228 12 I 139800 202 15 3 172500 '75 18.8 ^ Heater R P.M. H. P. 1940 17" r 1700 2 30 1460 3.00 1163 4-70 97' 6 80 830 9 25 727 121 645 '5 3 582 18 8 485 27.0 4'5 37 368 48 2 323 61 .0 284 82 Notes on Heating and Ventilation 223 are very large, with easy turns and of very short Disc Fans, length. They are exten- sively used for exhausting the air from the vent flues and where the vent flues are short and large they give good satisfaction. The capacity, speed and horsepower of various sizes of disc fans is shown in Table XXXVUI. Example. — As an example of the fan system consider an auditorium. The dimensions of the room are 40 feet g inches by 79 feet 6 inches by 127 feet 9 inches. The volume of the room is 413,- 000 cubic feet. It has 203 square feet of glass sur- face and 5,441 square feet of wall surface. The heat lost from the room, figuring in the same way as we have for previous examples, will be 168,010 B. T. U's. The hall has a seating capacity of 2,500 persons. Allowing 2,000 cubic feet of air per person, the necessary air to be admitted to the room will be 5,000,000 cubic feet of air per hour. This equals 383,000 pounds. In order to heat the room with this quantity of air entering, it will be necessary to heat the air but 1.85 degrees so that the air admitted to the room for ventilating pur- poses will be far more than that necessary for heat- ing purposes. It is best, then, to figure on admit- ting air only for purposes of ventilation. To heat this air from zero to 70° would require 383,oooX .2375X70=6,353,000 B. T. U's. Referring to 224 Notes on Heating and Ventilation Table XXXV^ we see that a heater coil 12 pipes deep will heat air having a velocity of 1,250 feet per minute to a temperature of 82°, which is prob- ably about the proper assumption to make in this case. The coil will condense 2.1 pounds of steam per square foot per hour. Each pound gives up about 970 heat units, so that each square foot of heater coil will give ofif about 2,000 B. T. U's. per hour. Then the number of square feet of heater coil required would be 6,350,000 -:-2,ooo^=3, 175 square feet. The heater coils are usually made of I -inch pipe and each square foot of surface is equivalent to about 3 feet of i-inch heater pipe, hence there will be required 3,175X3 or 9,525 feet of I -inch pipe in the heater coils. The air to be admitted to the hall is 5,000,000 cubic feet per hour or 83,300 cubic feet per minute. The usual velocity allowed for the air passing through the heater coil is 1,200 feet per minute. This will re- quire an air area in the heater coil of 83, 300 -^^ 1,200 =69.5 square feet. The area in the various heater coils will be found in the blower company's cata- logues and is also given in Table XXXAT. This will determine the size of the heater coil to be used. On account of the size of the hall and the amount of air introduced, it will be best to have two fans for delivering air into the building. Each fan would then need a capacity of 41,650 cubic feet Notes on Heating and Ventilation 225 per minute. In order to overcome the resistance of the flues the pressure should be from .2 to .3 of an ounce at least. From the table of fan capaci- ties we see that a 180-inch fan running at 150 rev- olutions would require 19.6 horsepowers and pro- duce a pressure of .503 ounces. This, how-ever, is ^ higher pressure than would be desired unless the flues were very long and had a number of curves. If the flues are short and straight we could use two 200-inch fans running at 100 revo- lutions. These fans would deliver 55,000 cubic feet of air each, with a pressure of .273 ounces and re- quire 12.9 horsepower to drive them. By using a larger size of fan 6.7 horsepow^ers (for each one of the fans) would be saved. Assuming the air to be delivered to the hall by four ducts, these ducts being large, it would be reasonable to allow a velocity of 1,500 feet per minute in the duct. Each duct would have to carry 20,800 cubic feet of air per minute ; 20,800-^1,500=13.8 square feet in area. As the registers of these ducts wnll be large and situated well above the head line, it would be safe to allow^ a velocity of 400 feet per minute to the register. The area of each register, assuming that there are four entering the room, w^ould be 26 square feet. The vent flues leaving the room should have an area about equal to the hot air flues. CHAPTER XII , A CENTRAL HEATING SYSTEM. It is not intended in this chapter to discuss the design of heating systems, such as is used in the heating of a city, but sys- Design and Location, terns that are in use for the heating of pubhc institu- tions, or groups of buildings. The type of system to be used in a given installation depends very largely upon the location and character of the build- ings to be heated. No two systems, even though designed by the same engineer, will be the same, and the suggestions made in this chapter can be but general. Before starting the design of a central heating system it is first necessary to have a careful survey of the property. This survey should show the ex- act location of the buildings to be heated, the ele- vation of the basement and first floor, together with a general profile of the ground through which the tunnels or pipes are to be run. The profile of the ground will largely decide the proper location of the power house. The power house should be located as nearly as possible to the buildings to be heated or as near as possible to the largest steam load. It Notes on Heating and Ventilation 227 should be low enough, if the profile of the land will permit, so that the condensation of the return mains may be returned to the power house by gravity. If possible, it should be so located that the floor of the boiler room may be drained to the sewer. Con- siderable difficulty is usually experienced to carry away the water, which results from the cleaning and blowing ofif of the boilers if no sewer connection can be made. The question of the soil, the location of the railroad siding, the water supply and the general appearance of the power house must also be taken into consideration. Before designing the power house the type and general form of boilers must be determined. If the power house is to work on a low pressure system with a pressure under lOO pounds, either fire or water Bailers, tube boilers may be used. In general, for this service fire tube boilers are very satisfactory, as they have large water storage, re- pairs are easily made, and the boiler may be crowded considerably beyond its rating. The economy of water tube and fire tube boilers is prac- tically the same. The principal objection to fire tube boilers, ex- cept of the Scotch marine type, is the large space which it occupies. If the power house is to be op- erated on high pressure, that is, over lOO or 125 pounds, then only water tube or Scotch marine boil- 228 Notes on Heating and Ventilation ers can be used. The size of the boiler must be deter- mined by the amount of steam which is to be used l)y the radiation and other devices taking steam from the boilers. The steam used bv the different forms of radiation can be determined by reference to the radiator tables previously given. Aftei having once determined the cjuantity of steam the plant is expected to use, it is customary to assume that each scjuare foot of heating surface in a boiler will evaporate about three pounds of water. This determines the total amount of heating surface that the boilers should contain. The boiler units should be so selected that one boiler or one set of boilers will take care of the plant during the light load period of operation, that two boilers or sets of boilers w411 take care of the average operating load. In addition to this there should be a boiler or set of boilers that will take care of the maximum con- ditions of load. There should always be a sufficient number of boilers in the plant so that at least one boiler or set of boilers can be out of service for a considerable period of time for cleaning or repair- ing. In a central heating plant using the gravity return system, it is necessary that all boilers have their water line at the same level. Systems of Distribution. The general design of a piping system and its lo- cation will depend upon the system of distribution adopted. Notes on Heating and Ventilation 229 If the gravity return system is used no main feed pump is necessary, the water returning by gravity to the boiler, as previously described. AVith this sys- Oravity System, tem any difference in pres- sure between that in the boiler and that at the ex- treme point in the piping system will result in a corresponding elevation of the water level in the return system at the extreme point — each one pound drop of pressure in the steam piping corresponds to an increase in the level of the water in the return piping of 2.30 feet. It is essential, then, that the gravity return system with a difference in pressure between that at the boiler and that at the extreme point of the piping system be comparatively small. The difference of pressure assumed wall deter- mine the size of the piping. In gravity systems it is usual to allow for the drop of pressure not over two pounds between the boiler and the extreme end of the system. In some cases the gravity return system has been used over quite an extended area, the most distant building heated being as far as 2,500 feet from the boiler, and the system has given very good satis- faction. In a central heating plant using the gravity re- turn system unless the steam mains are six to eight feet above the return it is necessary that the steam condensed in the mains be dripped separately from 230 Notes on Heating and Ventilation the main returns in the building and this drip pumped back to the boilers, preferably by a pump and receiver, or some other mechanical means, such as a return trap. This pump and receiver should be of sufficient size to take care of the steam condensed in the mains when the steam is being turned on and the condensation is excessive. By returning the condensation of the mains separately, excessive hammering is avoided and the system can be started much more rapidly. Gravity return is used only where the boiler pressure does not exceed ten pounds. The high pressure heating system is being little used for general heating purposes. It has some advantages. The pipes are smaller and radiation is more effective per square High Pressure System, foot. The disadvantages, however, outweigh the ad- vantages in most cases. In the high pressure sys- tem cast iron radiators are not safe, as they are not usually made to operate at a pressure to exceed twenty pounds. The pipe coil or other form of radiation must be used. The cost of producing steam, the chance of accident, and the cost of re- pairs are increased. It is not possible to use ex- haust steam with a high pressure system. When pipe coil radiation is used it would be safe to carry a pressure up to lOO pounds. In determining the Notes on Heating and Ventilation 231 size of steam mains for such a system a loss of pressure as high as ten pounds would not be con- sidered excessive. In the high pressure system each building usually sends its condensation back to the return system through a trap so that the pressure on the return is only slightly above the atmosphere. This condensation returns to a surge tank, from which the feed pumps return it back to the boilers. The drip from the steam mains is dripped directly back into the return system. In a very large system where it is difficult to get enough difiference in elevation between steam and return mains, or where the drop in pressure exceeds Low Pressure Pump two pounds, it is usual to Return System, install some form of pump return. One of the most common forms of pump return is to trap the return condensation of each building into the return main, which carries the re- turn back to a surge tank in the boiler room. From this surge tank the water is returned to the boiler by means of a pump. The drip from the steam main is trapped directly to the return main. The most objectionable feature of this system is the constant attendance and the repairs necessary to take care of the traps. In most cases the heating system is combined with some form of power system. This makes a 232 Noxks ON Hh:ating and Ventilation very economical coinbiiia- Combination of Power tion, as the exhaust from and Heating System. the power plant may be used in the heating system. Where the exhaust can be entirely utilized for from six to eight months of the year it is seldom profit- able to use condensing engines. Figure 63. There are two general schemes used for com- bining a power and heating system. In the simplest form the boilers are operated at a high pressure. The steam goes from the boilers to the engine, and after the steam leaves the engine it passes directly to the heating system. A by-pass pipe is carried XoTEs OX Heating and Ventilation 233 from the high pressure steam main to tlie heating main and in this by-pass is located a reducing pres- sure valve. If for any reason the engine does not supply sufficient steam to maintain pressure on the heating system, then the reducing valve opens and Fisure 64. introduces live steam. The returns from the heat- ing system are carried back to the boiler by means of a pump. Fig. 63 shows the general arrangement of sys- tems of this kind with a by-pass for furnishing live steam to a heating system. This system depends in a measure for its success upon the action of the reducing pressure valve. The cross-section of a reducing pressure valve is shown in Fig. 64. Such valves have been found to 234 Notes on Heating and Ventilation be quite reliable when well designed and well made. The principal cause for trouble is when the valve becomes foul with dirt. In- a system of this kind the engine exhaust is always provided with a back pressure valve connected to the atmosphere. This valve is so arranged that if for any reason excessive pressure should accumulate in the heating system « iat^ P'-est u^t< QQ'^r'-s 0:&^i 9 a I if Figure G5. the valve would open and exhaust the steam into the atmosphere. The arrangement show^n in Fig. 63 is most used in small plants and both the heat and the power can be taken from one boiler. In larger plants the heating boilers are operated on the low pressure and the power boilers on the high pressure system. In the high pressure system steam goes Notes on Heating and Ventilation 285 to the engine and pumps and is exhausted through an oil separator into the low pressure system. The pressure of the exhaust is determined by the pres- sure carried on the low pressure system. This sys- tem is particularly desirable where the heating load is considerably larger than the power load ; and where at times the engines are entirely shut down and only the low pressure system is operated. Fig. 65 shows a sketch of this arrangement. £'/euc://'/ •= V- .E *- o w ii S a •- c ~ :;? i *: ^- •- £ a; ■Si 3 ;/ ^ ^ -^ c J S^ - u. ^ 3 - 1. Asbestos 145 .319 1.23 136. .803 2. Magnesia 119 .224 .94 166. .915 3. Magnesia and asbestos. .125 .500 1.12 118. .879 4. Asbestos and wool felt .190 .228 1.12 102. .910 5. Wool felt 117 .234 1.16 110. .904 6. Wool felt and iron with air space 134 .269 . 125. .828 Sectional Coverings. 7. Mineral wool 097 .193 .94 91. .952 8. Asbestos sponge 105 .220 1.12 102. .920 9. Asbestos felt 100 .217 1.35 94. .923 10. Hair felt 080 .186 1.45 75. .960 Non-Sectional Coverings. Two layers asbestos paper 388 .777 364. .268 Two layers asbestos paper, one inch hair felt and one thickness canvas 070 .150 68. 1,000 isfactory. It is expensive, but its expense is war- ranted in the saving from condensation in the piping. Table 40 shows the relative effectiveness of dift'er- ent thicknesses of covering. Column 3 of this table 254 Notes on Heating and Ventilation shows the relative effectiveness of the various thick- nesses of covering compared with the bare pipe. From this table it is not a difficult matter to figure the amount of saving that may be made by using various thicknesses of covering. Knowing the amount of steam carried per year and the cost to produce i,ooo pounds of steam, and having the results shown in this table, we can easily compute the financial savine to be made in the various thick- Table XL. Heat Transmission for Varying Thiclinesses of Covering. Ratio of B. T. IJ.'s Condensation of condensa- trans- Tliickness of per sq. ft. per tion covered mitted per covering, liour in pounds, to bare pipe. sq. ft. per hour. V^ .120 .281 167. % .117 .255 163. 1 .107 .231 149. IV2 .099 .219 138. 1% .087 .191 121. 2 .078 .19 108. Tlie covering used in obtaining the above results was a wool felt. ^ nesses of covering. In doing this it is usually found that for building work an inch covering is suf- ficientl}' heavy ; but for tunnel work and all work- where the heat loss from the pipe is entirely lost • and does not enter the building it is economy to use covering 2 inches thick. Table 41 shows the heat lost through a i-inch wool covering with various steam pressures. In covering a pi]:)ing system the Notes on Heating and Ventilation 255 fittings and valves should be covered the same thick- ness as the pipe. This also applies to flanges and steam traps. Where flanges and other parts which require removal are covered they should be covered so that the covering can be taken ofif easily. A sat- isfactory method of doing this is to form a cover- ing composed of one layer of asbestos paper, i inch of hair felt and one thickness of 8-ounce duck. These are quilted together with cord so that the Heat Table XLI. Transmission for Varying Pressures. Condensation Gauge per sq. pressure, ft. per hour. Ratio of condensation of covered to bare pipe. B. T. U.'s transmission per sq. ft. per hour. 5.3 9.6 15.5 20.5 .108 .111 .126 .134 . .239 .233 .227 .223 100. 104. 110. 119. jacket is firmly held in one piece. This covering is then fastened over the pipe to be covered by means of hooks and laces. The advantas^e of coverino: may be shown from the following computation : Example. — In a given steam plant it was found that the heat lost from bare pipes per hour was 3,355,000 B. T. U's. In the particular plant in question the number of heat units required to make a pound of steam was 990, and this loss of heat would represent a condensation of 3,390 pounds of 256 Notes on Heating and Ventilation steam per hour. Assuming an evaporation of 9 pounds of steam per pound of coal this would be equivalent to 376 pounds of coal per hour. If the plant were operated 365 days in the year and 20 hours a day, and the coal cost $3.25 per ton, the yearly loss would be $2,069. ^Y covering the pipe I inch thick with hair felt the loss which would re- sult from the bare pipe would be reduced 15 per cent, which equals $314, making a saving of $1,755 by putting on covering. This amount capitalized at 10 per cent would represent an investment of $17,- 550. In the particular case in question the actual cost of the covering was but $3,500. In steam piping work it is very important that the piping system be provided with sufficient number of properly located air valves. Pri- Air Valves. marily, air valves should be located at the points in the piping at which air accumulates in quantity. We are familiar with the fact that when a radiator is not provided with an air valve steam will not circulate into it and it does not become warm. This is true of both steam mains and the return system. The writer has seen the entire return system of a building plugged with air on account of there being no air valve on a high point in the return main. For radiators an air valve similar to that shown in Fig. 75 is usually used. You will notice tli^at this air valve allows air entering from the connection Notes on Heating and Ventilation 257 to the radiator to pass directly to the top of the air valve body and out through a small hole or open- ing, which may be adjusted by means of a screw plug. If water enters the air valve, the water will rise in the valve body until the copper float, having a pin on its upper end, rises so as to close the exit Figure 75. Type of air valves commonly used on radiators. Figure 76. Air valve used on radiators in con- nection with Paul valve. from the air valve, and no water is allowed t^ escape. When steam enters the air valve the ex- pansion plug shown at the center of the air valve expands, raising the copper float, again closing the outlet from the air valve. Fig 76 shows an air valve which is used for radi- ators in connection with a system of air piping from the air valves. (i) is a cap screw screwed 268 Notes on Heating and Ventilation down on the valve with a lead washer, making a tight seat. (2) is a hollow screw upon which the expansion post (3) sets, closing the valve. The adjustment of the valve is done with screw (2), and this may be done without disturb- ing the valve. (3) is a hollow part fastened at (5) and held in place by the union (6). This should never be disturbed. (4) is the nipple of the valve body, by which it is attached to the radiator. This is the union for attaching to the piping of the Paul >ystem or other air piping system. (7) is a nut which forms the union for attaching this piping. The operation of the valve is as follows : The air is drawn in from the radiator through nipple (4) into the valve between the adjusting screw (2) and the composition part (3) passing down through (3) into the pipe. Wh^n steam enters the composition part becomes heated and expands, thereby closing the opening between (3) and (2). When air again accumulates and cools this composition part con- tracts, permitting air to be drawn through the tube. There are two typical forms of air valve, one closing off the air by the action of the float, the other closing off the air by the action of heat ex- panding a plug. V\^. 75 shows a combination of these two principles, which prevents the throwing of water or the discharging of steam. Fig. 76 exemplifies the simple expansion opera- Notes on Heating and Ventilation 259 tion. The valve shown in Fig. 76 would allow cold water to pass. Fig. yy shows an air valve particularly adapted to hot water work. In this air valve the float prin- ciple alone is used. Air enters in through the con- Figuie 77. Air valve adapted to hot water work. nection to the radiator, as shown by the arrow in the cut, passes under the float and escapes through a small tube which reaches to a point near the top of the air valve. As soon as the water enters the float lifts, due to the air compressed by the water under the float, and the rubber valve held by the rim closes the opening through which the air escapes. The valve as shown here is made for connection to an air valve piping system. A similar valve is made without this connection. In the air 260 Notes on Heating and Ventilation valve shown for connection to a piping system there is a three-way plug cock in the air valve, which al- lows of air and water being drawn directly to the air pipe system and of being entirely closed off. The pipe used in steam heating work is usually of standard weight, except for boiler blow-offs and boiler feed pipes, which are Pipe, Valves and Fittings, made of extra heavy pipe. Steam pipe is made of steel or wrought iron. Wrought iron is more ex- pensive than steel, but gives better results. Steel pipe can be made which is very satisfactory, but care should be used in selecting a good grade of pipe. Cast iron elbows and tees are more satisfac- tory than malleable iron and they should be full weight. There are on the market light-weight cast iron fittings. The advantage of cast iron for fittings is that the fittings can be broken with a sledge if at any time it is desired to open the pipe. If malleable iron fittings are used it is necessary to cut them out with a cold chisel, which is expensive. In putting up piping bushings are to be avoided as much as possible and reduction in size made in the fittings. Valves 2 inches and under are usually made of brass composition and should be of full weight. Over 2 inches it is customary to use iron body brass mounted. Valves over 4 inches should be provided with yokes. Valves 6 inches and over should be provided with by-passes. CHAPTER XIV, AUXILIARY DEVICES FOR HEATING SYSTEM. A temperature regulator is an automatic device which will open and close the valve of the radiator so as to keep the room at a constant tempera- ture. The temperature regulator in general consists of three parts. First, a thermostat which is so constructed that its parts will move with a change of temperature in the surrounding air and the motion of these parts will directly or indirectly open the dampers or valves wdiich control the heat supply. Second, there must be some means of transmitting the motion from the parts of the ther- mostat to the valves or dampers controlling the heat supply. Third, some form of mechanism for open- ing the valves or dampers. In most temperature regulating systems the thermostat merely fur- nishes power enough to close or open an air valve or electric sw^itch and thus start or stop the opera- tion of the valves or dampers. The form most used at the present time uses com- pressed air to operate the valves and dampers. In the Johnson thermostat a small air valve is opened by the expansion of a curved strip composed of two 262 Notes on Heating and Ventilation materials having dififerent rates of expansion. The bending of this strip due to change of temperature allows the air to escape and a small diaphragm to move back, thus opening a second valve allowing the air to come from the compressor or source of air supply and close the valve or damper on the radiator. When the room becomes cool the con- traction of this strip closes the first small valve forc- ing out the diaphragm and closing ofif the compressed air supply to the valve or damper and releasing the air already in the valve or damper. Another form of thermostat extensively used is operated by means of a liquid confined in a thin metal vessel, the liquid having a very high degree of expansion. As the liquid expands or contracts it controls the system of valves controlling the heat supply to the room. Temperature regulation is a desirable thing in all large heating systems, particularly for public build- ings. The systems are quite expensive, but the expense of construction is more than offset by the saving in fuel bills. The saving in fuel bills in most cases is not less than 20 per cent and often as high as 30 per cent. In general the operation of these systems has been entirely satisfactory even after they have been in use some time without any attend- ance. The control of the temperature of the room should be regulated within 3 degrees. With proper care these systems should control the temperature Notes on Heating and Ventilation 263 of the room within 2 degrees. Temperature regu- lating apparatus is particularly desirable in school rooms ; this places the temperature of the room out- side the control of the instructor and it is then free from his own personal ideas in the matter, thus adding much to the health and comfort of the occu- pants of the room. The discharge of air Air Piping System. from the air valves and ra- diators often produces a very disagreeable odor and in addition it is very difficult to obtain an air valve which will not at times discharge a certain amount of steam or water. This difficulty may be overcome by using an air valve so designed that the discharge connection to the valve can be fastened to a piping system. The pipes and air valves are carried to the basement, collected into a larger pipe and discharged to a sew^er or suitable vessel. A system of air piping is very desirable, particularly in large buildings, such as hotels and office buildings, where it saves ma- terially in the attendance necessary to keep the plant in operation. It is also desirable in nice residences where any discharge of water or steam might in- jure the furnishings. In case it is desirable to install a vacuum system of heating this system, could be connected directly to a vacuum pump in- suring more rapid circulation in the radiation. It is alwavs desirable in a steam or hot water 264 Notes on Heating and Ventilation heating plant, particularly steam, to install some form of dam])er regulator Damper Eegulators. on the boiler. In some heating plants it consists of an ordinary rubber diaphragm enclosed in a metal case. The steam is allowed to come in contact with one side of the diaphragm, pushes a lever attached to the other side of the diaphragm. This lever op- erates a damper controlling the air supply to the fire and sometimes also operates the check valve in the breeching. This is a very desirable arrange- ment as it reduces the attendance necessary to keep the pressure in the boiler at the point desired. The humidity of the atmosphere is a very im- portant consideration in any heating system. When the air is very dry it is Humidity Regulation, necessary for a room to have a much higher tem- perature in order that it may feel comfortable than when the air is moist. It is, therefore, important that we keep the humidity at a point as high as consistent with satisfactory operation. Cold air contains proportionately less moisture than warm air and therefore when cold air is heated and brought into a building, it should be moistened in order to keep a proper per cent of humidity. The average humidity is about 70 per cent ; in the most arid regions humidity is as low as 30 per cent. Hu- midity as low as 30 per cent produces irritation of Notes on Heating and Ventilation 265 the lungs and smarting of the eyes. In cold weather, if the humidity of the outside air is 70 per cent and this air is heated and brought into the room without moistening, its humidity may be reduced as low as 30 or 35 per cent, making the air as dry as in the most arid regions. This pro- duces a serious effect upon the inhabitants and also the furniture of the room. The decrease of humidity due to the action of the heating system occurs particularly in the indirect heating system. There has been placed on the market wdiat is called a humidostat. This is similar to a thermostat ex- cept that it is arranged so that as the moisture de- creases in the room the humidostat opens up a se- ries of steam or water jets in the air supply so that the air in passing through the steam or water jet takes up moisture. When the moisture gets to a certain percentage, determined by the setting of the humidostat, the apparatus closes ofif automatic- ally the steam or water jets. Such devices are particularly desirable in connection with school and hospital heating plants. In the large cities the smoke and dust in the air makes ■ it undesirable to introduce this air directly into the room for ventilat- ing purposes. A great Air Washers, many schemes have been tried to remove the dust from the air. The earliest form was to use burlap screens through which the Notes on Heating and Ventilation 267 air passes. These screens work fairly well but the finer dust will always be carried through tliem. A better plan is to pass the air through a sheet or series of sheets of water. After passing through these sheets of water the air is passed through an apparatus which removes the excess of water. Fig. 78 shows the general arrangement of an air wash- ing system. As you will notice from the figure, the air first passes through a tempering coil which raises the temperature from 60 to 70 degrees, then passes through the sprays or sheets of water, then through the eliminator where the excess of water is removed and then it passes to the heating coils to be heated. The water used for washing the air is circulated over and over again by means of a small centrifugal pump driven by a motor. In some cases it is desirable that the air should be cooled. This may be done by placing cooling coils in the tank where the water collects after having washed the air, and reducing the temperature of this water to the desired point. The washing of the air with water also increases the humidity of the air. In a plant installed by the author the humidity of the air has been kept at a point not lower than 60 per cent by means of the air washer. Air wash- ing devices are very effective in removing dirt ; the amount of dirt removed in some cases is very large. There is very frequently installed in connection 268 Notes on Heating and Ventilation with the heating system what is known as a vacuum heating system. There are Vacuum Systems. two principal forms of vacuum heating systems, one in which the air is drawn from the radiator by means of an air pump through an air valve, as shown in Fig. 76, and the other in which the radia- tor is fitted with a special form of return valve and vacuum is maintained on the re- turn, system by means of a pump or aspira- tor. The vacuum systems of heating lowers the temperature of the radiator and the radiators do not condense so much steam as they would un- der full pressure. They do not make any material saving in the amount of coal burned. The prin- cipal advantages of the vacuum systems are cer- tainty of circulation and the reduction of pressure in the piping system. They are particularly well adapted for use in connection with exhaust steam heating systems where the reduction of pressure in the heating system lowers the back pressure on the engine, increasing the horse power output of tlie engine. The vacuum system of heating in which the air is drawn from the air valves is particularly de- sirable in hospitals and school buildings as it does away with the objectionable odor from the air valves. I lie vacuum system of heating does away very largely with the attendance required by air Notes on Heating and Ventilation 269 valves. It also permits of the radiator being placed lower than the level of the boiler and the condensa- tion is raised from the lower level by means of the vacuum in the svstem. Oftentimes this enables the engineer to overcome serious difficulties in the de- sign of a heating plant. These systems can be profitably installed in old plants where the steam mains are overtaxed, owing to frequent additions to the plant. By additions of the vacuum system these old mains can be made to carry a larger weight of steam, the vacuum system permitting a higher velocity of steam in the system without increasing the back pressure. Sizes of Flow and Return Steam Mains Being an apprentice's query as to correct sizes of pipes in heat- ing plants, and answers thereto by twenty-five leading American heating engineers. These re- plies, giving the practice in some of the leading shops in many different cities of the country, with tables and diagrams, are by the following engineers : Prof. R. C. Carpenter, Cornell University Prof. J. H. Kinealy, St. Louis John Gormly, Philadelphia Ralph CoUamore, Detroit Gerard W. Stanton, New York Wm. G. Snow, Boston Thomas Barwick, New York EA. K. Munroe, Baltimore W. R. Stockwell, Irvington-on-Hudson Clarence M. Lyman, Utica, N. Y. R. R. M. Carpenter, Wilmington, Del. E. F. Capron, Chicago J. R. Shanklin, Charleston, W. Va. John S. Brennan, Milwaukee H. A. Smith, New York R. S. Thompson, Springfield, O. Bernard Gause, Jacksonville, 111. J. J. Wilson, Philadelphia Henry S. Kries, Baltimore Reginald Pelham Bolton, New York F. R. Still, Detroit Thomas Morrin, San Francisco James A. Donnelly, New York, and others. Bound in Beards, r-j • r r\ . i i- j 6Kx4>iinchei rrice DU cents, dehvered Domestic Engineering, 58-64 N. Jefferson St., Chicago Plumbing Catechism THEORY AND PRACTICE OF PLUMBING DESIGN By Charles B. Ball, M. Am. Soc. C. E., and M. Am. Soc. In- spectors of Plumbing and Sani- tary Engineers, and Herbert T, Sherriff, A, B., some-time Edi- tor of "Domestic Engineering", M. Am. Soc. Inspectors of Plumbing and Sanitary Engi- neers. Bound in cloth; 6}i x4^; 1 00 pp; elaborately indexed. This book formulates, in question and answer form, the basic principles of plumbing design and practice, crystallizing the knowledge of the skilled plumber, and providing the non-technical reader a source of information as free as possible from puzzling set phrases. It is sepecially commended to students in engineering and trade schools, and to master and journeymen plumbers, preparing for examinations. It does not discuss matters of handicraft such as joint wioing, lead burning, etc. CONTENTS: PLUMBING FIXTURES: Lavatories, kitchen sinks, bath tubs, laundry tubs, slop sinks, urineds, water dosets, water closet flushing apparatus, local ventilation, floor slabs, refrigerators. WATER SERVICE PIPELS: Fixture supply pipes, storage tanks, hot water supply systems. THE DESIGN OF PIPE SYSTEMS: The main drain, the main trap, the air inlet, traps, ventilation pipes. PUMPS. EFFECTS OF FREEZING. Price $1.00, delivered Domestic Engineering, 58 64 N.Jefferson St., Chicago FIFTY Plumbing Charts Showimg how modern, up- to-date, sanitary plumbing should be done. Paper bound, 9x5 yi inches; 50 pp. A lay-out of each of the fol- lowing jobs is shown, giving sizes of all pipes, heights of all fixtures; every joint, every piece of material and every fixture: Plate 1 Kitchen Sink Connection Plate : 27 Anti-Freezing W. C 2 Lavatory 28 Roof Connections 3 Water Closet 29 Roof Connections 4 Bath Tub 30 Fresh Air Inlet 5 Wash Tray \ << 3 1 Fresh Air Inlet 6 Pantry Sink <4 32 Traps 7 Urinal it 33 Traps 8 Slop Sink • < 34 Traps 9 Hotel Sink 4t 35 Grease Traps lOSitzBath <( 36 SoU Pipe on Side Wall 1 I Foot Bath 4« 37 Plumbing fcJr Residence 1 2 Bath Room «t 38 Cellar Work, Residence 13 Refrigerator it 39 Plumbing for Double House 1 4 Refrigerator Line Under Test 1 5 Ferru e Connections 40 Plumbing for 3 Tenement houses 1 6 Preparing Lead Works 4 1 Plumbing for Six Flats 1 7 Ferrule Connections 42 Cellar Work for Stores and Flats 1 8 Cleanouts 43 Plumbing for Horse Stall 19 Water Closets 44 Plumbing for Stables 20 Water Closets 45 Plumbing for Eng. House 21 Back Venting 46 Cellar Work, Eng. House 22 Back Venting 47 Plumbing for Hotel 23 Floor Con. for W. C. 48 Plumbing for R. R. Sta. 24 Roor Con. for W. C. 49 Plumbing for Y.M.C. A. Bldg. 25 Local Venting 50 Plumbing, High School 26 Local Venting Price 25 cents, delivered Domestic Engineering, 58-64 N. Jefferson St., Chicago JUL 3 1908