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 http://www.archive.org/details/cu31924022808301 
 

 By Charles L. Hubbard, B.S., M.E. 
 
 Power, Heating and Ventilation 
 
 IN THREE PARTS 
 
 Each complete in itself Sold separately 
 
 Part I Steam Power Plants $2.50 
 
 Part II Heating and Ventilating Plants 2.50 
 Part III Isolated Plants and Small Groups 
 
 {In Press) 
 
 McGRAW-HILL BOOK CO., Inc. . 
 
 239 WEST 39th STREET NEW YORK CITY 
 
yt 
 
 POWER, HEATING AND VENTILATION 
 
 PART II 
 
 HEATING AND 
 VENTILATING PLANTS 
 
 A Treatise for Designing and Construct- 
 ing Engineers, Architects and Students 
 
 BY 
 
 CHARLES L. HUBBARD, B.S., M.E. 
 
 Consulting Engineer 
 
 SECOND EDITION 
 
 Rewritten and Reset 
 
 McGRAW-HILL BOOK COMPANY, Inc. 
 
 339 WEST 39TH STREET, NEW YORK 
 
 6 BOUVERIE STREET, LONDON, E. C. 
 
 1914 
 
« 
 
 A, 2-104 1 <o 
 
 Copyright, 1914, 
 By > 
 Chables L. Htjbbakd. 
 
 
PREFACE 
 
 This volume includes the second part of a treatise covering the 
 design, construction and management of power, heating and 
 ventilating plants. 
 
 For the convenience of the reader, the work has been divided 
 into sections, and the chapters so arranged as to form three vol- 
 umes, each complete in itself. 
 
 ■ The matter contained in the following pages covers the subject 
 of heating and ventilation as applied to all classes of buildings, 
 from the small furnace-heated dwelling to structures of the 
 largest size. 
 
 The fundamental elements of the subject are quite fully 
 treated in the earlier chapters, thus making the work especially 
 valuable as a text-book for students as well as a book of reference 
 for engineers. 
 
 Special thanks are due to the editors of various magazines for 
 permission to use material which has appeared over the author's 
 name in their publications.- 
 
 As many of the chapters have been rewritten from several pub- 
 lished articles upon similiar subjects, it has been impossible to 
 give suitable credit in the text, and for this reason it has seemed 
 best to give the reference by chapters, as follows : 
 
 American Architect, Chapters 7, 8, 9, 15, 16. 
 
 American Artisan, Chapter 4. 
 
 Architectural Record, Chapters 4, 7. 
 
 Domestic Engineering, Chapters 13, 14. 
 
 Electrical Review, Chapters 2, 3, 12. 
 
 Engineering Review, Chapters 2, 3, 4, 9, 12. 
 
 Engineering Record, Chapter 16. 
 
 Heating and Ventilating Magazine, Chapters 2, 3, 12. 
 
 Machinery, Chapters 13, 14. 
 
 Merchant Plumber and Fitter, Chapter 5. 
 
 Metal Worker, Chapters 9, 10, 13. 
 
 Power, Chapter 13. 
 
 Sheet Metal, Chapters 3, 4. 
 
 Steam Engineering, Chapter 11. 
 
 V 
 
vi PREFACE 
 
 Heating and Ventilation oj Buildings, by Carpenter, data on heat, design of 
 aspirating coils and electric heating. 
 
 Mechanical Draft, B. F. Sturtevant, Company data on fans. 
 
 Furnace Heating, by Snow, data on the design of furnace heating plants. 
 
 Ventilation and Heating, B. F. Sturtevant Company, data on forced-blast heating 
 and ventilation. 
 
 Thanks are due to Mr. F. R. Still of the American Blower 
 Company for valuable data and suggestions in the preparation of 
 the matter on fans. 
 
 It has been the intention of the author to give credit in every 
 case where due, but if through any oversight this has not been 
 done, it will be considered a favor to have such oversight reported 
 in order that it rnay be corrected in future editions. 
 
 Charles L. Hubbakd. 
 Boston, Mass. 
 
CONTENTS 
 
 Chapter I. Physics of Heating and Ventilation 1 
 
 Theory of Heat; Temperature; Thermometers; Fahrenheit Scale; 
 Centigrade Scale; Unit of Heat; Specific Heat; Latent Heat; Conduction; 
 Convection; Radiation; Mediums for Heat Transmission, including 
 Air, Water and Steam; Force for Heat Transmission; Velocity of Air 
 Flow; Hot-Water Circulation; Flow of Steam in Pipes. 
 
 Chapter II. Heat Loss prom Buildings 12 
 
 Causes of Heat Loss; Loss by Transmission; Loss by Leakage; Com- 
 putations for Heat Loss; Corrections for Leakage and Exposure; Ap- 
 proximate Method; Practical Considerations; Cost of Heating. 
 
 Chapter HI. Ventilation 20 
 
 Atmospheric Composition; Oxygen; Nitrogen Carbon Dioxide; Analysis 
 of Air; Air Supply and Conditioning; Effect of Gas Jets; Air Quality; 
 Air Filtering; Air Cooling; Humidity; Heat Required for Ventilation; 
 Air Distribution; Measurement of Velocity; Cost of Ventilation. 
 
 Chapter IV. Fuenace Heating 32 
 
 Advantages and Disadvantages; Types of Furnaces; Materials of 
 Construction; Fire-Pot; Dome; Radiator; Heating Surface; Casing; 
 Air Passages; Grate; Evaporating Pan; Size of Furnace; Rate of Com- 
 bustion; Thermal Unit Method; Cubic Space Method; Auxiliary Equip- 
 ment; Smoke-Pipe and Chimney; Cold-Air Supply; Return Flue; Hot- 
 Air Pipes; Registers; Combination Systems; Comparative Costs. 
 
 Chapter V. Boilers 49 
 
 Types of Heating Boilers; Sectional Boilers; Tubular Boilers; Rating 
 of Cast-Iron Boilers; Boiler EflBiciency; Rate of Combustion; Ratio of 
 Heating to Grate Surface; Rating of Tubular Boilers; Proportions of 
 Tubular Boilers; Combustion and Evaporation; Construction of Tubular 
 Boilers; Chimneys. 
 
 Chapter VI. Pipe, Fittings and Valves 61 
 
 Wrought-Iron Pipe; Fittings; Details of Construction; Flanged Joints 
 and .Gaskets; Hangers; Pipe Expansion; Gate Valves; Globe Valves; 
 Angle Valves; Radiator Valves; Hot-Water Valves; Check Valves; Air 
 Valves; Pressure Reducing Valves; Back Pressure Valves. 
 
 Chapter VII. Direct Steam Heating. 74 
 
 Advantages and Disadvantages; Cast-iron Radiators; Wall Radiators; 
 Pipe Radiators; Circulation Coils; Radiator Efficiency; Computing Size 
 of Radiator; Location; Systems of Piping; Two-Pipe System; Returns 
 
viii CONTENTS 
 
 and Drips; One-Pipe Relief System; Arrangement and Expansion of 
 Risers; One-Pipe Circuit System; Radiator Connections; Vapor Sys- 
 tems; Vacuum Systems; Pipe Sizes;. Returns; Floor and Ceiling Plates; 
 Boiler Connections; Blow-Off Tanks. 
 
 Chapter VIII. Indirect Steam Heating 106 
 
 Advantages and Disadvantages; Types of Radiating Surface; Radiator 
 EflSciency; Computing Indirect radiation; Stack Casings and Supports; 
 Arrangement of Heater; Mixing Dampers; Heating by Air Rotation; 
 Pipe Connections; Pipe Sizes; Warm-Air Flues; Cold-Air Supply Ducts; 
 Vent Flues; Flue Dimensions; Velocity of Air in Flues; Aspirating Coils; 
 Vent Hoods; Registers and Grilles. 
 
 Chapter IX. Hot-Water Heating by Gravity Circuiation 128 
 
 Advantages and Disadvantages; Principles of Hot- Water Heating; 
 Types of Direct Radiating Surface; Efficiency of Direct Radiators; 
 Systems of Piping; Two Pipe System; Circuit System; Overhead System; 
 Pressure Systems; Expansion Tank; Air Venting; Radiator Connec- 
 tions; Valves and Fittings; Indirect Heating; Size of -Stacks; Flues and 
 Casings; Pipe Connections; Combination Systems; Pipe Sizes for Direct 
 Radiation; Pipe Sizes for Indirect Radiation; Boilers and Connections; 
 Testing Steam and Hot-Water Systems. 
 
 Chapter X. Hot- Water Heating by Forced Circulation 154 
 
 Systems of Piping; Sizes of Mains and Branches; Velocity of Flow; 
 Loss Through Friction; Centrifugal Pumps; Design and Construction; 
 Efficiency and Horse Power; Types of Heaters; Heating Surface and 
 Efficiency; Auxiliary Heaters; Pump and Heater Connections. 
 
 Chapter XI. Exhaust Steam Heating 169 
 
 Factors to be Considered; Feed-Water Heating; Use of Live Steam; 
 Effect of Back-Pressure; Steam Traps; Return Traps; Return Pumps; 
 Oil Separators; Supply Piping; Exhaust Piping; Return Connections; 
 Types of Vacuum Systems; Webster System; Paul System. 
 
 Chapter XII. Electric Heating 184 
 
 Types of Heaters; Material for Heaters; Connections for Electric 
 Heaters; Comparative Cost of Steam and Electric Heating. 
 
 Chapter XIII. Fans 189 
 
 Types; Proportions of Centrifugal Fans; Fan Calculations; Pressure 
 and Velocity; Capacity; Speed and Volume; Horse Power; Resistance; 
 Mechanical Draft; Calculations; Effect of Temperature; Propeller Fans. 
 
 Chapter XIV. Forced Blast Heating and Ventilation , 215 
 
 Systems of Vetilation; Combined Heating and Ventilation; Main 
 Heaters; Details of Pipe Heaters; Details of Cast-iron Heaters; Efficiency 
 of Pipe Heaters; Efficiency of Cast-Iron Heaters; Hot-Water Heaters; 
 Pipe Connections; Pipe Sizes; Fan Drives; Ducts and Flues. 
 
CONTENTS ix 
 
 Chapter XV. Special Devices 236 
 
 Automatic Temperature Control; Air Compressors; Thermostats; 
 Pneumatic Valves; Diaphragm Motors; Dampers; Hot-Water Regula- 
 tors; Telethermometer; Humidostat; Air Filters; Air Washers; Humidity 
 Control; Air Cooling. 
 
 Chapter XVI. Heating and Ventilating Duterent Types of Buildings. 255 
 Ventilation of Dwelling Houses; Ventilation of Schoolhouses; Fur- 
 naces; Flues; Gravity System; Air Supply; Stacks; Dampers; Radia- 
 tors; Coils; Direct and Indirect Systems; Fan Systems; Diffusers; Ar- 
 rangement of Heaters; Condensation; Connections; Ventilation of 
 Toilet Rooms and Hoods; Ventilation of Hospitals; Asylums, etc.; 
 Heating and Ventilating Churches; Heating and Ventilating Halls and 
 Theaters, Office Buildings, Shops and Factories. 
 
 Chapter XVII. Care and Management oe Heating and Ventilating 298 
 
 Plants 
 
 Furnaces; Low-Pressure Steam Heating; Hot-Water Heating; School 
 Buildings. 
 
PART II 
 
 HEATING AND VENTILATING PLANTS 
 
HEATING AND VENTILATING PLANTS 
 
 CHAPTER I. 
 PHYSICS OF HEATING AND VENTILATION. 
 
 As the various effects of heat enter so largely into the subjects 
 treated in the following pages, a brief discussion of its nature and 
 some of its more important properties may be of assistance to the 
 reader, by fixing clearly in his mind the exact meaning of the 
 terms most frequently used. 
 
 Heat is recognized by the bodily sensation of touch, and by 
 means of this we are able to judge roughly of the temperature of 
 an object. The terms heat and cold are relative only, and when 
 we speak of a body as being hot or cold we mean that its tempera- 
 ture is higher or lower than that of some other body with which 
 it is compared. 
 
 Theory of Heat. — There have been many theories in regard to 
 the exact nature of heat, but the accepted one at the present time 
 is that of molecular vibration. It is thought that heat is a vibration 
 of the molecules of which a body is composed, and that the degree 
 of heat, or temperature, depends upon the velocity and amplitude 
 of these vibrations. 
 
 Temperature and Its Measurement. 
 
 Temperature. — The intensity of the heat in a body, that is, the 
 velocity of vibration of its molecules, is called the temperature. 
 This, however, does not indicate the quantity of heat which it 
 contains. For example, a small bar of iron may be heated to a 
 white heat and still contain a much smaller quantity than a larger 
 bar at a lower temperature. 
 
 1 
 
2 HEATING AND VENTILATING PLANTS 
 
 Thermometers. — The temperature of a body is determined by 
 comparing it with some substance whose intensity of heat is 
 known. The simplest way of doing this is to use a substance the 
 volume of which changes a definite amount with the addition or 
 removal of a given quantity of heat, and always has the same 
 volume for the same degree of temperature. 
 
 This principle is rnade use of in the thermometer, which con- 
 sists of a glass bulb, usually containing mercury or alcohol, and 
 to which is attached a tube of small bore. As heat is applied to 
 the bulb the mercury expands and rises in the tube, the height at 
 which it finally stands indicating the temperature of the sur- 
 rounding medium. 
 
 Fahrenheit Scale (F.) . — The scale most frequently used in this 
 country is known as the Fahrenheit scale. The graduations in 
 this case are obtained by noting the position of the mercury col- 
 umn when the bulb is placed in melting ice, and again when 
 placed in steam which is being evaporated under atmospheric 
 pressure. This difference in the heights of the column is divided 
 into 180 equal parts, called degrees. The freezing point of this 
 scale is marked 3i3 degrees, which makes the boiling point 33 + 
 ISO = 212 degrees above zero. 
 
 Centigrade Scale (C). — In the French system the Centigrade 
 thermometer is used. The freezing point on this scale is marked 
 zero, and the boiling point 100. 
 
 Methods of Conversion. — As the difference between the freez- 
 ing and boiling points on the Fahrenheit scale is divided into 180 
 degrees, and on the Centigrade scale into 100 degrees, it follows 
 that 1 degree C. = 180 -^ 100 = 1.8 degree F., and 1 degree F. 
 = 100 -^ 180 = 0.55 degree C. 
 
 Zero on the Centigrade scale is at the freezing point, and on 
 the Fahrenheit scale it is 3i2 degrees below the freezing point. 
 Therefore, to change the Fahrenheit scale to Centigrade, we must 
 first subtract 33 and then multiply the remainder by 0.55. 
 
 The methods of conversion may be represented by the follow- 
 ing equations, in which C. is the reading in degrees Centigrade 
 and F. the reading in degrees Fahrenheit. 
 
 C. = 0.55 X (F. — 32) 
 F. = (1.8 X C.) -f 30 
 
PHYSICS OF HEATING AND VENTILATION 3 
 
 Example. — Reduce 60° F. to the Centigrade scale. (60° — 32) 
 X 0.55 = 15.4° C. The reason for this is evident because 60° 
 F. is 60 — 33 = 3.8° above the freezing point and 1° F. = 0.55° 
 C. ; then 28° F. = 26 X 0.55 = 15.4° C. 
 
 In Hke manner readings on the Centigrade scale may be 
 changed to Fahrenheit by first multiplying by 1.8 and then adding 
 32 to the product. 
 
 General Definitions for the English System. 
 
 Unit of Heat. — The unit of heat is taken as the quantity re- 
 quired to raise the temperature of one pound of pure water one 
 degree at its point of greatest density, which is at about 3.9° F. 
 
 The quantity of heat required to raise one pound of water 
 through successive degrees is not quite constant, but increases 
 slightly as the temperature rises. For all practical purposes, 
 however, we inay neglect this, and define a heat unit, or British 
 Thermal Unit (B. T. U.) as the quantity of heat required to 
 raise the temperature of one pound of water one degree 
 Fahrenheit. 
 
 Specific Heat. — The quantity of heat required to raise the tem- 
 perature of a body one degree is called its thermal capacity. The 
 thermal capacity of a pound of pure water is one B. T. U. and is 
 greater than that of any other known substance. The thermal- 
 capacity of a given weight of any other substance, compared with 
 an equal weight of water, is called its specific heat, and is always 
 less than 1. We may thus define specific heat as the quantity of 
 heat, expressed in thermal units, required to raise the tempera- 
 ture of one pound of any substance one degree. 
 
 Latent Heat. — When heat is applied to a body and it passes 
 from a solid to a liquid state, its temperature remains practically 
 constant during the process. The heat which disappears during 
 this change is called the latent heat of fusion, and represents the 
 work done in tearing apart the molecules of the substance. When 
 the body solidifies, this heat is given back again. The heat re- 
 quired to change a liquid into a gas is called the latent heat of- 
 evaporation, or vaporization. The heat necessary to melt ice into 
 water, and then evaporate the water into steam, are familiar ex- 
 amples of the above. 
 
 Conduction. — The transfer of heat between two bodies which 
 
4 HEATING AND VENTILATING PLANTS 
 
 are in contact is called conduction. When this transfer takes 
 place between different parts of one continuous body, it is called 
 internal conduction. When it passes from one body to another it 
 is known as external conduction. If one end of an iron bar be 
 held in the fire, the other end soon becomes heated by conduction. 
 If a piece of wood were used in place of the bar, the end in the 
 fire would burn, and but little heat would be transferred to the 
 other end. Thus we see that some substances are good con- 
 ductors of heat while others are not. 
 
 Conduction enters largely into problems relating to the heat loss 
 from buildings and will be considered in detail in Chapter II. It 
 is also an important factor in the insulation of warm-air flues, 
 steam and water piping, boilers, etc., as described later. 
 
 Convection. — We know from experience that lighter solids or 
 liquids will float upon a heavier liquid. When a portion of a 
 liquid is heated and expands, it rises to the surface because it is 
 lighter, or rather because the cooler liquid surrounding it falls to 
 the bottom of the vessel and forces the lighter liquid upward. 
 Currents set up in this manner are called convection currents. 
 Convection also takes place in gases. 
 
 Radiation. — We have learned that in a heated body the mole- 
 cules are supposed to be in violent agitation. The motion of these 
 vibrating molecules or particles is communicated to the surround- 
 ing ether, and transmitted by it with great rapidity in the form of 
 waves. Heat transmitted in this manner is called radiant heat, 
 and the process is called radiation. 
 
 Radiant heat travels in straight lines through a uniform medium, 
 and the radiation is equal in all directions. The heat from a fire- 
 place or steam radiator is radiant heat, and passes through the 
 air to the walls of a room which absorb it. As these become warm 
 the heat is given off to the surrounding air by conduction and is 
 diffused throughout the room by convection. A certain amount 
 of heat is also absorbed by the air directly from the radiator in 
 the same way. 
 
 Practical Application. 
 
 The applicaition of the above principles to problems in heating 
 
 and ventilation will now be shown by a few practical illustrations. 
 
 Mediums Employed in Heat Transmission. — The usual me- 
 
PHYSICS OF HEATING AND VENTILATION 5 
 
 diums employed for the transmission of heat from the furnace to 
 the rooms to be warmed are air, water, and steam. 
 
 Transmission by Air. — Computations relating to the first of 
 these require a knowledge of specific heat, in order to know how 
 many B. T. U. may be carried by a given weight or volume of air 
 under practical conditions, or how many B. T. U. will be required 
 to raise the temperature of a given volume of air any number of 
 degrees. Taking the specific heat of air as O.S'SS and the weight 
 of 1 cubic foot ait 60°, as 0.0764 pound, we find that 0.2-38 X 
 0.0764 = 0.01818 B. T. U. are required to raise the temperature 
 of one cubic foot of air 1°. Therefore, 1 B. T. U. will raise the 
 temperature of 1 cubic foot of air 1-^-0.01818 = 55°, or it will 
 raise the temperature of 55 cubic feet 1°. 
 
 The factor 55 will vary slightly for different temperatures and 
 pressures, but is suflSciently accurate for all ordinary computa- 
 tions involved in heating and ventilation. 
 
 Example. — If the air from a hot-air furnace is delivered to a 
 room at a temperature of 120°, how many B. T. U. will each 
 cubic foot give out in cooling to 70°, the normal temperature of 
 the room? 
 
 If, in cooling 1° each cubic foot of air gives out 55 B. T. U., 
 then under the conditions of the problem it will give out (1.20 — 
 70) X 5i5 = 2750 B. T. U. 
 
 Transmission by Water. — In case hot water is used as the 
 medium of transmission, a suitable temperature range is assumed, 
 and the necessary weight computed for giving out the required 
 amount of heat with the assumed drop in temperature. 
 
 Example. — A building requires 300,000 B. T. U. per hour for 
 warming purposes in zero weather. The hot water flowing 
 through the radiators is cooled 20° during its passage. How many 
 pounds of water must circulate through the system per hour to 
 warm the building? 
 
 If 1 B. T. U. is required to raise the temperature of 1 pound of 
 
 water 1°, then the same amount of heat will be given out when 
 
 the water is cooled 1°, or twenty times that amount if it is cooled 
 
 20°. Therefore, if 1 pound of water gives out 20 B. T. U. while 
 
 300,000 
 passing through the system, — ^ — =15,000 pounds must be 
 
 circulated per hour to give out the amount of heat required. 
 
6 HEATING AND VENTILATING PLANTS 
 
 Transmission by Steam. — This method makes use of the latent 
 heat contained in the steam, which is again given out as condensa- 
 tion takes place in the radiators. 
 
 When steam is generated in a boiler, the heat supplied by the 
 furnace is used in two ways. First, a certain amount is required 
 to raise the temperature of the feed water up to that of the 
 steam at the given pressure, called heat in liquid; and second, 
 
 
 Table I. 
 
 
 lESSURE, TeMPEEATDRE, AND 
 
 Latent Hi 
 
 Gauge Pressure, 
 
 Temperature, 
 
 Latent heat, 
 
 in pounds per 
 
 in degrees F, 
 
 in B. T. U. 
 
 square inch 
 
 
 per pound 
 
 
 
 212 
 
 966 
 
 1 
 
 216 
 
 963 
 
 2 
 
 219 
 
 961 
 
 3 
 
 222 
 
 959 
 
 4 
 
 225 
 
 957 
 
 5 
 
 228 
 
 955 
 
 6 
 
 231 
 
 953 
 
 7 
 
 233 
 
 951 
 
 8 
 
 235 
 
 950 
 
 9 
 
 238 
 
 948 
 
 10 
 
 240 
 
 946 
 
 12 
 
 244 
 
 943 
 
 14 
 
 248 
 
 940 
 
 16 
 
 252 
 
 938 
 
 18 
 
 256 
 
 935 
 
 20 
 
 259 
 
 933 
 
 22 
 
 263 
 
 930 
 
 24 
 
 266 
 
 928 
 
 26 
 
 269 
 
 926 
 
 28 
 
 272 
 
 924 
 
 30 
 
 274 
 
 922 
 
 the latent heait necessary for changing the water into steam. The 
 latter is much the larger of the two, and is the only factor con- 
 sidered in ordinary steam heating. 
 
 The latent heat varies with the pressure of the steam, and is 
 given in "Steam Tables," so called, which have been prepared 
 for convenient use. Table I., gives the temperature and latent 
 heat of evaporation for the range of pressures commonly used 
 in heating work. 
 
 Example. — What quantity of heat will be required to change 
 500 pounds of feed water from a temperature of 60 degrees into 
 steam at 5 pounds gauge pressure? 
 
 From Table I. the temperature and latent heat for this pres- 
 sure are found to be 2^° and 955 B. T. U. respectively. The 
 heat required for raising the temperature of one pound of feed 
 water to the point of evaporation is 2i28 — 60 = 168 B. T. U., 
 
PHYSICS OF HEATING AND VENTILATION 7 
 
 and for evaporating it into steam, 955 B. T. U., making a total 
 of 16& + 955 = 1,1^3 B. T. U. per pound, or l.ias X 500 = 
 561,500 B. T. U. for the whole amount. 
 
 Example. — What weight of steam, at 2 pounds gauge pressure, 
 will be required per hour for warming a building where the total 
 heat loss from all causes in the coldest weather is 580,000 B. T. U. 
 per hour ? 
 
 Table I. gives the latent heat for 2 pounds pressure as 961 
 B. T. U. Hence, 580,000 -f- 961 = 604 pounds will be required. 
 
 Force Required for Heat Transmission. — After the air, water, 
 or steam has received its heat from the furnace by conduction 
 through the various heating surfaces, a certain amount of force 
 is required to carry it to the various rooms of the building. In 
 the simpler forms of heating, known as gravity systems, the force 
 employed for moving air and water is that due to convection, in 
 which the courses of the currents are controlled by the use of 
 flues and pipes. In the case of steam, flow through the pipes is 
 due solely to a drop in pressure caused by condensation in the 
 radiators. lAs this takes place, steam from the boiler flows in to 
 replace that which has been condensed, and to equalize the pres- 
 sure between the two ends of the connecting pipe. 
 
 Velocity of Air Flow. 
 
 The velocity of air flow through vertical flues is given by the 
 formula 
 
 ■=sV 
 
 V-.- ' ^^ 
 
 460+ r 
 in which 
 
 F= velocity of flow, in feet per second. 
 
 A = height of flue, in feet. 
 
 Z)= difference in temperature between the outside air and that in 
 the flue. 
 
 r= temperature of the outside air. 
 
 This formula, however, is purely theoretical and does not take 
 into account the frictional resistance. Under actual conditions 
 only about 40' to 50 per cent of the velocity given by the formula 
 will be obtained, depending upon the smoothness of the interior 
 surface of the flue and its freedom from bends. 
 
 Example. — A hot-air register on the second floor of a building 
 
8 HEATING AND VENTILATING PLANTS 
 
 is 20 feet above the furnace. With an outside temperature of 
 40°, and a flue temperature of 90°, what will be the velocity of 
 flow, assuming the actual velocity to be 50 per cent of the theo- 
 retical ? 
 Substituting in the formula, we have, 
 
 F=8J^H5L = n.2, 
 >i 460+40 
 
 or actually, 11.2X0.5=5.6 feet per second. 
 
 Hot-Water Circulation. 
 
 As previously stated, the circulation of hot- water in a gravity 
 heating system is produced by convection currents, and therefore 
 operates upon the same general principle as a hot-air system. 
 The application of this principle, as utilized in practice, will be 
 made clear by the following illustration: If a glass tube of the 
 form shown at the left in Fig. 1 be filled with water and held in a 
 vertical position, no movement of the water will be noticed be- 
 cause the two columns A and B are of the same weight and there- 
 fore in equilibrium. Now if a lamp flame be held near the tube A, 
 the small bubbles of steam which are formed will show the water 
 to be in motion, with a currernt in the direction indicated by the 
 arrows. 
 
 The reason for this is that as the water in A is heated it ex- 
 pands and becomes lighter for a given volume and is forced up- 
 ward by the heavier water in B falling to the bottom of the tube. 
 The heated water flows from A through the connecting tube at 
 the top into B, where it takes the place of the cooler water which 
 is settling to the bottom. 
 
 If now the lamp be replaced by a furnace, the columns A and B 
 connected at the top by inserting a radiator, the illustration will 
 assume the practical form as utilized in hot-water heating and 
 shown at the right in Fig. 1. 
 
 The pressure or head producing circulation under the above 
 conditions is determined as follows: It has been found by 
 experiment, for the temperature range commonly employed in 
 hot-water heating, (150° to 21.3°) that a rise of 1° will reduce 
 the weight of a column of water 1 inch square by 1 foot in height, 
 0.000154 pound. This means, that for each degree difference in 
 
PHYSICS OF HEATING AND VENTILATION 9 
 
 temperature in the supply and return pipes to a radiator, there 
 will be a difference in weight of 0.000154 pound per square inch 
 of sectional area for each foot in height. Hence, to determine 
 the pressure, in pounds per square inch, producing a flow to a 
 given radiator, multiply the difference in temperature in the 
 Supply and return pipes (in degrees) by the height of the radiator 
 above the boiler (in feet), and this result by 0.000154. 
 
 As the pressures used in this class of work are commonly ex- 
 pressed in "feet head," the above factor may be reduced to this 
 
 EXPANSION 
 TANK 
 
 RADIATOR 
 
 Fig. 1 . Showing Principles of Hot- Water Heating. 
 
 denomination by dividing by 0.4^, the weight of a column of 
 water 1 inch square and 1 foot in height at a temperature of 
 180°. This gives a factor of 0.000154-^0.43 = 0.000367. 
 
 In the practical application of the above to the design of piping 
 systems for hot-water heating, frictional resistance must be 
 taken into account as described in a later chapter. 
 
 Example. — A radiator is located at an elevation of 30. feet 
 above the boiler. Neglecting friction, what will be the "pressure 
 head" for producing a circulation, with a temperature difference 
 of 10° between the supply and return pipes? 
 
10 HEATING AND VENTILATING PLANTS 
 
 Applying the above method, we find it to be 30X10X0.000367 
 ■-= 0.110 feet. 
 
 Flow of Steam in Pipes. 
 
 The flow of steam through iron pipes with smooth interior sur- 
 faces is given by the following formula, 
 
 W-- 
 
 4 
 
 w {p — ^i) d? 
 
 I 
 
 in which 
 1^= weight of steam per minute. 
 
 ie'= weight of a cubic foot of steam at pressure p. 
 
 ^= pressure of steam at inlet to pipe, called the initial pressure. 
 ^1= pressure of steam at outlet of pipe called the terminal pressure. 
 
 <^= diameter of pipe in inches. 
 
 /= length of pipe in feet. 
 
 c=a constant, depending upon the diameter of pipe. 
 
 Values of the constant c, and also the 5th powers, for different 
 diameters of pipe are given in Table II. 
 
 Table II. 
 Constants and Fifth Powers foe Formula for Flow of Steam. 
 
 Diameter 
 
 
 
 Diameter 
 
 
 
 of pipe, 
 
 Value of c 
 
 5th power 
 
 of pipe, 
 
 Value of c 
 
 5th power 
 
 inches 
 
 
 
 inches 
 
 
 
 I 
 
 45.3 
 
 1.00 
 
 5 
 
 58.4 
 
 31.25 
 
 
 48.2 
 
 3.05 
 
 6 
 
 59.5 
 
 77.76 
 
 IM 
 
 50.3 
 
 7.59 
 
 7 
 
 60.1 
 
 168.07 
 
 a 
 
 52.7 
 
 32.00 
 
 8 
 
 60.7 
 
 327.68 
 
 2K 
 
 54.3 
 
 97.60 
 
 9 
 
 61.2 
 
 590.49 
 
 3 
 
 56.1 
 
 243.00 
 
 10 
 
 61.8 
 
 1000.00 
 
 3)^ 
 
 57.1 
 
 522.90 
 
 12 
 
 62.1 
 
 2488.32 
 
 4 
 
 57.8 
 
 1024.00 
 
 15 
 
 62.6 
 
 10485.76 
 
 For the conditions of ordinary low-pressure steam heating it is 
 customary to assume a drop in pressure of 1/^ pound per 100 
 feet in length, for buildings of small and medium size. 
 
 Table III. computed by the preceding formula, gives the 
 pounds of steam discharged per minute through pipes of different 
 diameters, for drops in pressure of \'^ pound and % pound per 
 100 feet in length. 
 
 Where long runs of pipe are required, and when it is desired 
 to limit the drop in pressure to 14 o'' % pound at the extreme 
 
PHYSICS OP HEATING AND VENTILATION 
 
 Table III. 
 Flow of Steam in Pounds Per Minute. 
 
 11 
 
 Diameter 
 
 Drop in pressure, 
 
 of pipe. 
 
 
 
 inclies 
 
 KLb. 
 
 HLb. 
 
 1 
 
 0.44 
 
 0.63 
 
 1/^ 
 
 0.81 
 
 1.16 
 
 Ijl 
 
 1.06 
 
 1.89 
 
 2 
 
 2.93 
 
 4.17 
 
 2Vi 
 
 S.29 
 
 7.52 
 
 3 
 
 8.61 
 
 12.3 
 
 3M 
 
 12.9 
 
 18.3 
 
 4 
 
 18.1 
 
 25.7 
 
 5 
 
 32.2 
 
 45.7 
 
 6 
 
 51.7 
 
 73.3 
 
 7 
 
 76.7 
 
 109 
 
 8 
 
 108 
 
 154 
 
 9 
 
 147 
 
 209 
 
 10 
 
 192 
 
 273 
 
 12 
 
 305 
 
 434 
 
 15 
 
 535 
 
 761 
 
 end of the run, the quantities in Table III. should be multiplied 
 by the following factors : 
 
 Length of Run 
 
 Factor 
 
 200 ft. 
 
 0.70 
 
 300 ft. 
 
 0.57 
 
 400 ft. 
 
 0.50 
 
 600 ft. 
 
 0.40 
 
 800 ft. 
 
 0.35 
 
 1,000 ft. 
 
 0.31 
 
 Example. — What diameter of pipe will be required to deliver 
 12 pounds of steam per minute a distance of 400 feet, with a 
 drop in pressure of i/^ pound at the extreme end of the run ? 
 
 The factor for 400 feet is 0.5, hence, the weight of steam to 
 look for in Table III. is 12 -h 0.5 = 34 pounds. Looking in 
 column 3 of the table, we find a 4-inch pipe will discharge 25.7 
 pounds, with a drop of % pound, and is the size required. 
 
CHAPTER II. 
 
 HEAT LOSS FROM BUILDINGS 
 
 The first step in designing a heating system for a building is; 
 to determine the probable heat loss in B. T. U. per hour in the 
 coldest weather, after which, an equipment should be provided 
 of sufficient heating power to offset this loss when working at 
 its normal capacity. 
 
 Heat Loss. 
 
 Causes of Heat Loss. — ^The cooling of a building is due partly 
 to the transmission of heat through the walls and windows, and 
 partly to the leakage of air, both outward and inward, through, 
 the building construction and around the windows and doors. 
 
 When ventilation is provided an additional amount of heat is 
 required for bringing the temperature of the entering air up to 
 that of the room. This, however, cannot be considered strictly as 
 a loss, but must be included when estimating the total amount of 
 heat to be provided. 
 
 Loss by Transmission. — The heat loss by transmission depends 
 upon liie difference between the inside and outside temperatures ; 
 thickness of walls; the building material used; and also the 
 method of construction. Temperature differences will vary with 
 the locality and use of building. In iNew England and the Middle 
 States it is customary to provide for a minimum outside tempera- 
 ture of zero, while in certain portions of the West and North- 
 west, the plant should be designed for 10° to 30° below zero. In 
 other sections of the country, the minimum temperature will vary 
 from the above up to a point where practically no heating is re- 
 quired. The normal inside temperature is commonly taken as 
 70°, although special conditions will call for temperatures both 
 above and below this. With improvements in humidity control, 
 lower temperatures of 60° to 65° have been found to give the 
 same degree of comfort, and at the same time have proved to be 
 more healthful. 
 
 12 
 
HEAT LOSS FROM BUILDINGS 13 
 
 It is not usually necessary to provide a plant of sufficient ca- 
 pacity, except perhaps in hospital work, to meet the requirements 
 of the two or three extremely cold days which occur each season, 
 as these can generally be gotten through with comfortably by 
 forcing the boiler or furnace and by temporarily shutting off 
 some of the less important rooms. Continued minimum tempera- 
 tures should therefore form the basis of all heating computations 
 rather than occasional low records. 
 
 Loss by Leakage. — This depends largely upon the quality of 
 the building construction and also its exposure to winds. The 
 frequent opening of doors and windows is an important factor 
 in the heat loss by leakage. With a strong wind there will be a 
 constant inleakage of cold air on the windward side of the 
 building and a corresponding outward leakage of warm air on 
 the leeward side. 
 
 Computation for Heat Loss. 
 
 There are various methods of computing the heat loss from a 
 building, all necessarily giving approximate results. The use of 
 any table or formula for determining heat loss must be combined, 
 with knowledge gained by practical experience, to get the best 
 results. 
 
 Table IV. has been made up of data obtained from reliable 
 sources, and gives the heat loss in B. T. U. per square foot of 
 surface per hour, for different materials and methods of con- 
 struction. Transmission is given for temperature differences of 
 1°, and also for 50°, 60°, 70°, and 80°, which covers the usual 
 range of ordinary heating work. 
 
 For hollow walls of brick or stone, multiply the figures given 
 in the table by 0.85. 
 
 When walls of masonry have an inside furring of lath and 
 plaster, with shallow air space, multiply the tabulated transmis- 
 sion losses by 0.8. 
 
 Where rooms have a cold attic above or cellar beneath, multi- 
 ply the heat loss through walls and windows by 1.1 to 1.15, ac- 
 cording to the tightness of construction. 
 
 Correction for Leakage. — The figures in Table IV. apply only 
 to the most thorough construction. For the average well built 
 .house the results should be increased about 10 per cent; for fairly 
 
14 
 
 HEATING AND VENTILATING PLANTS 
 
 good construction, 20 per cent ; and for poor construction, 30 per 
 cent. 
 
 Correction for Exposure. — Table IV. also applies to rooms 
 having a southern exposure; for other exposures, multiply the 
 results by the proper factor as given in Table V. 
 
 Table IV. 
 Heat Transmission Through Various Butujing Structures. 
 
 Material and thickness 
 
 B. T. U. per 
 
 hr. per 
 
 deg. diff. 
 
 B. T. 
 
 U. per hr. for Diff. of 
 
 50° 
 
 60° 
 
 70° 
 
 80° 
 
 S" brick wall 
 
 0.40 
 0.32 
 0.26 
 0.22 
 0.20 
 0.18 
 0.80 
 0.55 
 0.40 
 0.66 
 0.48 
 0.39 
 0.34 
 0.29 
 0.27 
 0.24 
 0.21 
 0.30 
 1.20 
 0.30 
 0.17 
 0.36 
 0.40 
 0.60 
 0.54 
 1.30 
 1.20 
 0.60 
 1.30 
 0.65 
 0.40 
 0.30 
 0.60 
 0.50 
 0.20 
 0.15 
 0.10 
 
 20 
 16 
 13 
 11 
 10 
 
 9 
 40 
 28 
 20 
 33 
 24 
 20 
 17 
 15 
 14 
 12 
 11 
 15 
 60 
 15 
 
 9 
 18 
 20 
 30 
 27 
 65 
 60 
 30 
 65 
 33 
 20 
 15 
 30 
 25 
 10 
 
 8 
 
 5 
 
 24 
 19 
 16 
 13 
 12 
 11 
 48 
 33 
 24 
 40 
 29 
 23 
 20 
 17 
 16 
 14 
 13 
 18 
 72 
 18 
 10 
 22 
 24 
 36 
 32 
 78 
 72 
 36 
 78 
 39 
 24 
 18 
 36 
 30 
 12 
 9 
 6 
 
 28 
 22 
 18 
 15 
 14 
 13 
 56 
 33 
 28 
 46 
 34 
 27 
 ■24 
 20 
 19 
 17 
 15 
 21 
 84 
 21 
 12 
 25 
 28 
 42 
 38 
 91 
 84 
 42 
 91 
 46 
 28 
 21 
 42 
 35 
 14 
 11 
 7 
 
 32 
 
 12" brick wall 
 
 26 
 
 16" brick wall 
 
 21 
 
 20" brick wall 
 
 18 
 
 24" brick wall 
 
 16 
 
 28" brick wall 
 
 15 
 
 4" reinforced concrete 
 
 64 
 
 
 44 
 
 
 32 
 
 8" solid concrete 
 
 53 
 
 
 38 
 
 
 31 
 
 16" solid stone 
 
 27 
 
 20" solid stone 
 
 23 
 
 24" solid stone 
 
 22 
 
 28" solid stone 
 
 19 
 
 32" solid stone . 
 
 17 
 
 
 24 
 
 TTnlinftH nnrnigfltpd irnn 
 
 96 
 
 Koof of slate on matched boards . . 
 
 21 
 
 
 14 
 
 Roof of 6" hollow tile, 2" concrete, tar and gravel . . 
 Roof of 8" hollow tile, 1" concrete, tar and gravel . . 
 
 Roof of 4" concrete, cinder fill, tar and gravel 
 
 Roof of 6" concrete, cinder fill, tar and gravel 
 
 29 
 32 
 48 
 43 
 
 
 96 
 
 
 48 
 
 Single skylight 
 
 104 
 
 Double skylight. 
 
 52 
 
 
 32 
 
 2" wooden door 
 
 24 
 
 
 48 
 
 
 40 
 
 Concrete floor on brick arch 
 
 16 
 
 
 12 
 
 
 8 
 
 
 
 The method of using these tables is illustrated by the follow- 
 ing examples : 
 
 Example. — A certain room is to be maintained at a tempera- 
 ture of 70° in zero weather. The walls are of brick, 13 inches 
 in thickness, with lath and plaster furring, and present an exposed 
 area of 250 square feet. The windows are single, and make up 
 a total glass area of 60 square feet. The room has a westerly 
 
HEAT LOSS FROM BUILDINGS 15 
 
 exposure, and the building is of average construction. What will 
 be the total heat loss per hour? 
 
 From Table IV. we find the transmission factor for a 12-inch 
 brick wall, and a temperature difference of 70° to be 2-2, which 
 should be multiplied by 0.8 on account of the lath and plaster 
 
 Table V. 
 
 
 ;cTioN Factors for 
 
 Exposure 
 
 ; OF R( 
 
 Exposure 
 
 
 Factor 
 
 N. 
 
 
 1.32 
 
 E. 
 
 
 1.12 
 
 S. 
 
 
 1.0 
 
 W. 
 
 
 1.20 
 
 N. E. 
 
 
 1.22 
 
 N. W. 
 
 
 1.26 
 
 S. E. 
 
 
 1.06 
 
 s. w. 
 
 
 1.10 
 
 N. E. S. W. or total exposure 
 
 1.16 
 
 furring. Factor for single window, from the same table, 84; 
 factor for leakage, 1.1 ; factor for exposure, 1.2^. 
 Applying these factors to the problem, we have 
 
 Wall 250 X 32 X 0.8 = 4,400 
 
 Glass 60 X 84 = 5,040 
 
 9,440 B. T. U. 
 Correcting this for leakage and exposure we find the total heat 
 loss to be 
 
 9,440 X 1-1 X 1.2 = 12,460 B. T. U. per hour 
 
 Example. — A room 15 ft. X 20 ft. X 10 ft. is to be heated to 
 70° when it is 30° below zero outside. The longer side has a 
 northerly exposure and three windows each 3 ft. X 5 ft., with 
 double sashes. The shorter side has an easterly exposure, with 
 two windows of the same size, with single sashes. The walls are 
 of stone, 16 inches in thickness, with lath and plaster furring, and 
 a cold attic extends over the entire room. What will be the heat 
 loss per hour, assuming the building to be of fairly good con- 
 struction ? 
 
 Taking up the problem in the same general manner as before, 
 we have the following data; 
 Temperature difference, 70 -|- 20 = 90°. 
 For the longer side. 
 
 Window area, 3 X 5 X 3 = 45 sq. ft. 
 
16 HEATING AND VENTILATING PLANTS 
 
 Factor for transmission, 0.6 X 90 = 54 
 
 Wall area (10 X ^0) — 45 = 155 sq. ft. 
 
 Factor for transmission, 0.34 X 90 X 0.8 = 24.5 
 
 Factor for exposure, 1.3i2 
 For the shorter side. 
 
 Window area, 3 X 5 X 2 = 30 sq. ft. 
 
 Factor for transmissiion, 1.2 X 90 = 108 
 
 Wall area (10 X 15) —30 = 120 sq. ft. 
 
 Factor for transmission, 24.5 
 
 Factor for exposure, 1.12 
 For the whole room 
 
 Factor for cold attic, 1.1 
 
 Factor for leakage, 1.2 
 Making the various computations we find the heat from the 
 longer side to be 
 
 Glass, 45 X .54 = .2,430 
 Wall, 155 X 24.5 = 3,798 
 
 6,22i8 B. T. U. 
 Correcting this for exposure gives 
 
 6,228 X 1-32. == 8,221 B. T. U. 
 For the shorter side we have 
 
 Glass, 30 X 108 = 3,240 
 Wall, 120 X 24.5 = 2,940 
 
 6,180 B. T. U. 
 Correcting this for exposure gives 
 
 6,180 X 1.12 = 6,922 B. T. U. 
 
 Adding these results, and correcting for cold attic and leakage, 
 makes a total heat loss of (8,221 + 6,922) X 1.1 X 1.3 = 19,989 
 B. T. U. per hour. 
 
 Example. — A church of average wooden construction has a 
 ground dimension of 40 ft. by 60 ft. and an auditorium ,30 ft. in 
 height at the sides. The windows, which are single, make up % 
 the total outside exposure. The basement is unwarmed, and there 
 is a cold attic above. What will be the total heat loss in zero 
 weather, allowing ,270,000 B. T. U. per hour for ventilation? 
 Gross wall area (40 + 40 + 60 + 60) X 20 = 4,000 sq. ft. 
 Window area, 4,000 X Ys = 500 sq. ft. 
 
HEAT LOSS FROM BUILDINGS 17 
 
 Net wall area, 4,000 — 500 = 3,500 sq. ft. 
 
 Factor for window transmission, 84 
 
 Factor for wall transmission, 2.1 
 
 Factor for cold attic, 1.1. 
 
 Factor for cold basement, 1.1 
 
 Factor for leakage, 1.1 
 
 Factor for exposure, 1.16 
 
 Making the various computations we have 
 Glass, 500 X 84 = 43,000 
 Wall, 3,500 X 31 = 73,500 
 
 115,500 B. T. U. 
 
 Correcting this result for attic, basement, leakage, etc., gives 
 115,500 X 1.1 X 1.1 X 1.1 X 1-1'6 = 177,870 B. T. U. Adding 
 to this the heat required for ventilation, makes a total of 177,870 
 + 370,000 = 447,870 B. T. U. per hour. 
 
 Approximate Method for Heat Loss. — A convenient method, 
 which may be used to approximate the heat loss from buildings 
 of ordinary wooden construction, is to multiply the total exposed 
 surface by a single factor which shall include all the heat losses 
 under average conditions. The factors given below are based 
 on the assumption that 1/6 the exposed surface is glass and 5/6 
 wall; with an increase of 10 per cent for cold attic, ;30 per cent 
 for leakage, and 16 per cent for exposure. The effect of a cold 
 basement is supposed to be offset by the' kitchen range and radia- 
 tion from the boiler. 
 
 Outside Temp. 
 
 Factor 
 
 + 10° 
 
 45 
 
 0° 
 
 50 
 
 — 10° 
 
 55 
 
 This method is to be used simply for approximating the size 
 of boiler for direct steam or water heating, or the total radiation 
 for small buildings like dwelling houses, apartments, etc. It 
 should not, however, be applied to those of special construction or 
 having a large proportion of window area. The heat loss from 
 individual rooms must, in all cases, be computed separately by 
 the methods already given. 
 
18 HEATING AND VENTILATING PLANTS 
 
 Practical Considerations. 
 
 When measuring the wall surface of a room, for estimating the 
 heat loss, only the outside exposure should be taken, unless there 
 is an inside partition coming against an unheated space ; surfaces 
 of this kind may be considered as equivalent to one-third an 
 equal amount of outside wall. 
 
 The heat loss from a vestibule or hallway, subject to the fre- 
 quent opening of an outside door, and to leakage around the 
 same, will greatly exceed that computed by the foregoing 
 methods. A certain amount of practical experience is necessary 
 to deal with problems of this kind satisfactorily, but under aver- 
 age conditions, it will usually prove safe if the computed heat 
 loss is doubled. Before starting to make any of the computations 
 a set of tracings of the different floors should be made from the 
 architect's plans, omitting all details of construction which do not 
 especially affect the heating work. 
 
 Dimensions may be scaled directly from these plans with suffi- 
 cient accuracy, and are taken in even feet. In estimating the glass 
 area, measure the opening inside the window casing, making no 
 allowance for the sash. 
 
 Each room to be heated should be numbered on the plans, and 
 all computations tabulated under their proper room number. 
 
 A very satisfactory method of tabulating data of this kind is 
 shown in Fig. -2, which can also be extended to include the sizes 
 of radiators, flues, registers, etc. Data arranged in this manner 
 are very convenient, both in connection with the work in hand, 
 and for future reference. 
 
 In the above, w = transmission factor for wall ; g ^= trans- 
 mission factor for glass ; I = factor for leakage ; and e = factor 
 for exposure. In general, all of the above factors will be the 
 same for the various rooms, except e. Column H is for cases 
 where the heat loss must be corrected for special conditions, such 
 as cold attics, etc. This form of tabulation is given simply as 
 a suggestion, engineers usually preferring to devise one accord- 
 ing to their own ideas. 
 
 Cost of Heating. 
 
 The cost of heating will depend upon the outside temperature, 
 the efficiency of the boiler or furnace, and the cost of fuel. 
 
HEAT LOSS FROM BUILDINGS 
 
 19 
 
 The first condition will vary with the geographical location and 
 season of the year. 
 
 The cost is usually estimated for the entire heating season, and 
 is based upon the average temperature, which must be obtained 
 from the weather records for the particular location under con- 
 sideration. In New England and the Middle States it is cus- 
 tomary to assume a heating season of ,2il3 days (7 months) and 
 an average outside temperature of about -|- 36°. With these 
 data at hand it is a simple matter to compute the heat loss in 
 
 Name of Buildin 
 
 
 
 
 
 
 
 
 w= , (7= , 1= t e= , 
 
 
 A 
 
 B 
 
 C 
 
 D 
 
 E 
 
 F 
 
 O 
 
 H 
 
 Room 
 number 
 
 Wall 
 area 
 
 Heat 
 
 loss, 
 
 UXw) 
 
 Glass 
 area 
 
 Heat 
 
 loss 
 
 (CX9) 
 
 Total 
 
 heat 
 
 loss, 
 
 (.B+D) 
 
 Combined 
 
 factor for 
 
 leakage and 
 
 exposm-e 
 
 (IXe) 
 
 Total 
 
 corrected 
 
 heat 
 
 loss, 
 
 iEXF) 
 
 Total 
 
 heat loss 
 
 corrected 
 
 for special 
 
 conditions 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Fig. 2. Blank {or Tabulating Data. 
 
 B. T. U. per hour from a given building, from which the total 
 heat loss is the B. T. U. per hr. X 34 X 313, for continuous warm- 
 ing. If the building is warmed for only a portion of each day, 
 the result may be reduced accordingly, with a certain allowance 
 for "warming up" in the morning. 
 
 In this method of computation a perfect system of temperature 
 regulation is assumed, which shall exactly proportion the 
 quantity of steam used to the heating requirements. 
 
 In practice this is not possible and the results obtained above 
 should be multiplied by 1.5 and 1.1 for hand control and auto- 
 matic control, respectively, to offset the heat lost through open 
 windows and wasted by overheating. 
 
 In considering the boiler efficiency, we may assume each pound 
 of coal to furnish 8,000 B. T. U. for warming purposes. There- 
 fore, the total heat loss for the season, divided by 8,000, will give 
 the pounds of coal required; the actual cost of which is easily 
 computed from the current price of coal in that locality. 
 
CHAPTER III. 
 VENTILATION. 
 
 The subject of ventilation is one of much importance, and the 
 problem of maintaining air of a certain standard of purity in all 
 occupied buildings should receive careful attention. 
 
 An illustration sometimes used in emphasizing the necessity of 
 an abundant air supply is to compare its importance with that of 
 food and water. For example, it is possible for a man to live 
 three weeks without food, three days without water, but only 
 three minutes without air. The immediate effect of a vitiated 
 atmosphere is to produce a feeling of drowsiness or weariness, 
 usually followed by a dull headache, while the continued occu- 
 pancy of poorly ventilated rooms results in a lowered vitality and 
 a greater susceptibility to disease. 
 
 That it decreases both the mental and physical capacity for 
 work has been shown in many cases by the increased output in 
 shops and offices where efficient systems of ventilation have been 
 installed. 
 
 In the case of hospitals, statistics show a reduction of about 90 
 per cent in the death rate in children's hospitals, and 70 per cent 
 in general and army hospitals, due to the installation of modern 
 systems of ventilation. 
 
 Formerly, it was considered that all requirements were fulfilled 
 if a sufficient quantity of air was provided, but present standards 
 take into account, quality as well. 
 
 Atmospheric Composition. 
 
 Atmospheric air is a mechanical mixture in which the principal 
 constituents are oxygen and nitrogen, in the proportion of 1 part 
 oxygen to 4 of nitrogen, by weight. 
 
 In addition to these are various other substances in small 
 amounts, such as carbon dioxide, sulphuretted hydrogen, am- 
 monia, and nitric, nitrous, sulphuric and sulphurous acids. Water 
 
 20 
 
VENTILATION 21 
 
 vapor and various organic impurities are also found in varying 
 quantities according to the locality. 
 
 Oxygen. — The most important constituent is oxygen. This 
 takes an active part in the chemical process of combustion, and 
 also in the changes which occur in the lungs during respiration. 
 In the latter process it unites with the excess of carbon in the 
 blood and forms carbon dioxide, or carbonic acid gas, which is 
 given off with other impuriities in the act of breathing. 
 
 Nitrogen. — This serves the purpose of diluting the oxygen and 
 rendering it less active. It takes no part in the various processes 
 of combustion, and passes through both the furnace and the lungs 
 without change. 
 
 Carbon Dioxide. — This, in moderate quantities, is not espe- 
 cially harmful or disagreeable unless combined with other im- 
 purities. Its effect is to decrease the readiness with which the 
 oxygen unites with the carbon of the blood, and for this reason, 
 if present in sufficient quantities, may produce even fatal results. 
 The small amount of this gas found in occupied buildings is not 
 in itself injurious, but it serves as an index to certain other 
 harmful gases and organisms which exist in a fixed proportion 
 to it. 
 
 On this account tests for the purity of air are commonly based 
 on the proportion of carbon dioxide which is easily determined 
 by chemical analysis. 
 
 Carbonic acid exists in the open country in the proportion of 3 
 to 5 parts in 10,000. For conditions of good ventilation it should 
 not exceed 6 to 7 parts, which allows for an increase of 2 to 3, 
 parts over that of the open air. 
 
 Analysis of Air. — An accurate qualitative and quantitative 
 analysis of air can only be made by an experienced chemist. But 
 there are several approximate methods for determining the 
 amount of carbonic acid present, which are sufficiently exact in 
 most cases. These, while making use of different forms 
 of apparatus, employ practically the same principal, which is to 
 determine the volume of air necessary to change a given amount 
 of lime water from a clear to a milky appearance when shaken 
 together in a glass bottle or other closed receptacle. In. a general 
 way, a device for this purpose consists of a glass cylinder of 
 
22 BEATING AND VENTILATING PLANTS 
 
 known volume, in which is placed a definite quantity of lime 
 water. Connected with this is a piston, by means of which the air 
 may be exhausted from the cylinder, thus allowing air from the 
 room to flow in and take its place. In operation, the cylinder is 
 filled with the air to be tested, then thoroughly shaken to mix it 
 with the lime water. If the latter shows no change, the air is 
 exhausted and the cylinder again filled, and the operation re- 
 peated. This is continued until the lime water begins to show a 
 milky or cloudy appearance. Knowing the quantity of lime water 
 used and the number of cylinders of air necessary to change it, 
 the proportion of carbon dioxide may be at once determined from 
 tables furnished with the apparatus. 
 
 Air Supply and Conditioning. 
 
 The standard of purity for different degrees of ventilation is 
 based upon the number of parts of carbon dioxide contained in 
 10,000 parts of air. This, as previously stated, should not exceed 
 7 parts, and if possible, the ventilating equipment should be de- 
 signed for keeping the proportion below 6 parts in 10,000, when 
 working under normal conditions. 
 
 Table VI. 
 Amount of Air Required for Ventilation. 
 
 Standard parts of 
 
 carbonic acid in 
 
 10,000 o£ air in 
 
 room 
 
 Cubic feet of air required per person 
 
 Per minute 
 
 Per hour 
 
 5 
 6 
 7 
 8 
 9 
 10 
 
 100 
 50 
 33 
 25 
 20 
 16 
 
 6000 
 3000 
 8000 
 1500 
 1200 
 1000 
 
 Assuming the average production of carbon dioxide by an 
 adult at rest to be 0.6 cubic feet per hour, and the outside air to 
 contain 4 parts in 10,000, the cubic feet to be supplied per hour 
 per occupant may be found by dividing 6,000 by the allowable 
 increase in carbon dioxide per 10,000 parts of air. 
 
VENTILATION 23 
 
 For example, to maintain a standard of purity of 5 parts in 
 10,000, the air supply should be 6,000 h- (5 — 4) = 6,000 cubic 
 feet per hour per occupant, and for a standard of 6 parts in 
 10,000 it should be 6,000-^ (6 — 4) = 3,000 cubic feet, and so 
 on. 
 
 Table VI., computed in this manner, gives the required air 
 supply per occupant for different standards of purity. 
 
 While this table gives the theoretical quantities of air required 
 and may be used as a guide, it will be better in actual practice to 
 use quantities which experience has shown to give good results 
 in different types of buildings. 
 
 In auditoriums where the cubic space per individual is 
 large, and in which the atmosphere is thoroughly fresh before the 
 rooms are occupied, and the occupancy is of only two or three 
 hours' duration, the air supply may be somewhat reduced from 
 the figures given above. 
 
 The following represents good modern practice and may be 
 used with satisfactory results : 
 
 Table VII. 
 Air Supply for Various Buildings. 
 
 Air supply per occupant for 
 
 Hospitals 
 
 High schools 
 
 Grammar schools 
 
 Theaters and assembly halls. 
 Churches 
 
 Cubic feet 
 
 Cubic feet 
 
 per minute 
 
 per hour 
 
 80 to 100 
 
 4,800 to 6,000 
 
 BO 
 
 3,000 
 
 40 
 
 2,400 
 
 25 
 
 1,500 
 
 20 
 
 1,200 
 
 Although it is usually better to base the air supply upon the 
 number of occupants, there are cases when this information is 
 not available, or the use of the room is such that the number of 
 people within it is constantly changing, as in public toilets, waiting 
 rooms, libraries, etc. In rooms of this general character it is 
 common practice to base the air supply upon a certain number of 
 complete changes per hour. When this is done, the use of the 
 room, the character of the occupants, and condition as to crowd- 
 ing, etc., must be taken into consideration. 
 
24 HEATING AND VENTILATING PLANTS 
 
 In general, the following will be found satisfactory for aver- 
 age conditions : 
 
 Table VIII. 
 Air Supply for Various Rooms. 
 
 TT £ _ Changes of air 
 
 Use of room pe? hour 
 
 Public waiting room 4 to 5 
 
 Public toilets 5 " G 
 
 Coat and locker rooms. , . 4 " 5 
 
 Museums 3 " 4 
 
 Offices, public 4 " 5 
 
 Offices, private 3 " 4 
 
 Public dining rooms 4 ■■ 5 
 
 Living rooms 3 ' 4 
 
 Libraries, public 4 " 5 
 
 Libraries, private 3 '' 4 
 
 It often happens that architects' plans give only the dimensions 
 of an auditorium or schoolroom without stating the seating ca- 
 pacity. In instances of this kind it is safe to assume about 15 
 square feet of iioor space per occupant, which includes aisles, 
 platform, etc. 
 
 Sometimes in the case of audience halls the space allowed per 
 occupant is made as low as 10 or" 12 square feet, but the larger 
 figure is more common. 
 
 Effect of Gas Jets. — In estimating the air supply, it is not only 
 necessary to consider the number of occupants, but also the 
 method of lighting. The burning of a gas jet or lamp not only 
 consumes a certain amount of oxygen in the process of com- 
 bustion, but also gives off carbon dioxide, thus lowering the 
 standard of purity of the air. Under average conditions each 4i/2 
 foot gas burner requires about 50 cubic feet of air per hojr, 
 which must be added to the general supply. 
 
 The problem of ventilation in theatres and large audience halls, 
 which require brilliant illumination, has been greatly simplified by 
 the introduction of incandescent electric lighting, which does its 
 work without vitiating the atmosphere. 
 
 Air Quality. — Aside from carbon dioxide and its associated 
 impurities, air quality commonly refers to dust or other solid 
 matter held in suspension, and to the relative humidity. Harm- 
 ful or objectionable gases from manufacturing plants or other 
 sources require special treatment and are not included i'.i the 
 ordinary methods of air purification. 
 
VENTILATION 25 
 
 What is commonly called dust is of two classes; that which is 
 ordinarily visible, and that which can only be seen in a ray of 
 sunlight. While ordinary dust is not of itself injurious, except 
 for its irritating effect upon the mucous membrane of the respir- 
 atory passages, it is liable to contain disease germs, especially in 
 cities and large towns, and for this reason should be removed, so 
 far as possible, where large volumes of air are supplied for ven- 
 tilating purposes. 
 
 Aside from the matter of unhealthfulness, the large amount 
 of dust and soot brought into city buildings with the air supply is 
 a constant source of damage, both to the building itself and its 
 contents. 
 
 Air Filtering. — ^Dust is removed from air by the process of 
 filtering, which is of two kinds, dry and wet. The first method 
 employs screens or bags of loosely woven cloth which simply 
 catch the coarser particles of dust. Filters of this kind do not 
 remove disease germs, and are only applicable to cases where the 
 air supply is small, as in special rooms or suites of rooms. Their 
 use is confined principally to offices and banking rooms as a 
 protection against the soiling of books and papers. When a 
 thorough cleansing of a large volume of air is desired, the spray 
 filter or air washer is employed. By this method the particles of 
 dust are washed from the air, carrying the disease germs with 
 them, thus making the process very effective from the standpoint 
 of purification. Recent investigations along this line seem to 
 indicate that a portion, at least, of the air purified in this manner 
 may possibly be recirculated with satisfactory results in place of 
 fresh air from outside. Should this prove feasible, it would re- 
 sult in a large saving in fuel. 
 
 While investigations of this kind have been confined prin- 
 cipally to laboratory tests, future developments in ventilating 
 methods are thought to lie in the direction of improvement in 
 air quality rather than by increasing the quantity. 
 
 Air Cooling. — By using a fine spray or mist in the washer suffi- 
 cient evaporation may be obtained to produce a decided cooling 
 effect on the entering air, especially if its relative humidity is 
 low. This feature of the washer is of especial importance in 
 connection with hospital work. 
 
 Humidity. — This is the general term employed to denote the 
 
26 HEATING AND VENTILATING PLANTS 
 
 percentage of moisture in the air under varying conditions. The 
 amount of water vapor which will be diffused in a closed space, 
 where water is present, depends entirely upon the temperature. 
 If the space contains air, it is said to be "saturated" under these 
 conditions, although the presence of the air has nothing to do with 
 the amount of moisture diffused at the given temperature. 
 
 "Relative humidity," which is the term commonly employed in . 
 practical work, is the ratio of the moisture actually contained 
 in the air to that which it is capable of holding at the point of 
 saturation, at the same temperature. 
 
 The normal humidity of the outside atmosphere varies from 40 
 to 70 per cent and if it passes these limits in either direction, to 
 any extent, unpleasant sensations are experienced. If the hu- 
 midity is too low there will be a dryness in the throat and nose, 
 and the body will feel chilly at normal temperatures. If too 
 high, there will be a sense of oppressiveness, causing more or 
 less discomfort. The temperature of a room in which the air has 
 been properly moistened, may be kept 4 or 5 degrees lower than 
 where the air is dry. This is because of the reduced evaporation 
 from the bodies of the occupants, which tends to make the room 
 seem equally warm, although actually at a lower temperature. 
 
 The practical methods employed in air cooling and humidity 
 control will be taken up in a later chapter. 
 
 Heat Required for Ventilation. 
 
 It has been previously stated that 1 B. T. U. will raise 
 the temperature of 1 cubic foot of air 55°, or will raise 55 
 cubic feet 1°. From this it is evident that the heat units required 
 to raise the temperature of a given quantity of air through any 
 number of degrees will be equal to the volume in cubic feet, mul- 
 tiplied by the rise in temperature in degrees, divided by 55. This 
 is expressed algebraically by the following equation : 
 
 ^^=B.T.U., 
 55 
 
 in which 
 
 C= cubic feet of air. 
 
 r=rise in temperature in degrees. 
 
 Example. — What quantity of heat will be required to warm 
 
VENTILATION 27 
 
 100,000 cu. ft. of air to 70° for ventilating purposes when the 
 outside temperature is 10° below zero? 
 
 100,OOOX80h- 55 = 145,454 B. T. U. 
 The factor T/o.5 is approximately 1.1 for 60°, 1.3 for 70°, and 
 1.5 for 80°. 
 
 Assuming a temperature of 70° for the entering air, we may 
 multiply the air volume supplied for ventilation by 1.1 for an 
 outside temperature of 10° above zero, 1.3 for zero, and 1.5 for 
 10° below zero, which covers the conditions most commonly met 
 with in practice. 
 
 Air Distribution. 
 
 Air for ventilation is conveyed from the furnace or heating 
 chamber to the various rooms through ducts and flues, usually 
 of sheet metal or masonry construction. In the gravity system, 
 so called, the air movement is due to the higher temperature 
 inside the flue, as already described in Chapter I. This force 
 is comparatively weak, and is often overcome by wind or other 
 outside causes, except under the most favorable conditions. This 
 method of air movement,, however, is the simplest in use, and the 
 one almost universally employed in dwelling houses, and also in 
 halls, churches and schools of small size. In large buildings, 
 where the air must be carried through horizontal ducts of con- 
 siderable length, fans are employed to produce the necessary 
 pressure. By this method, an even distribution of air is secured 
 in all parts of the building without regard to wind pressure or 
 other external causes, and at a small expenditure of power. 
 
 Exhaust fans are also employed for removing the foul air from 
 buildings, both in connection with supply fans, and with gravity 
 systems of heating. 
 
 Air Distribution in Different Types of Buildings. — The best 
 method of delivering the fresh air to a room will depend some- 
 what up its use. In dwelling houses, cottage hospital wards, etc., 
 where the volume of air is comparatively small in proportion to 
 the amount of heat brought in, the inlet registers are usually 
 placed in the floor or in the baseboard near the floor. This ar- 
 rangement provides an opportunity for warming or drying the 
 feet and supplies a certain amount of warm air in the lower part 
 of the room, where it is most needed. 
 
28 
 
 HEATING AND VENTILATING PLANTS 
 
 In the case of school rooms, where large volumes of air are 
 required at moderate temperatures, the best results are obtained 
 by bringing in the supply at a height of 7 or 8 feet above the 
 floor. With this arrangement the entering air first rises to the 
 ceiling, spreads out, and then, as it becomes slightly cooled, falls 
 with a gradual movement to the breathing line, without sensible 
 drafts. The foul air, in rooms of this kind is removed through 
 vent registers placed near the floor. 
 
 The general path of the air under these conditions is illustrated 
 in Fig. 3. 
 
 Fig. 3. Path of Air in Room. 
 
 Inlet and Outlet Arrangements. — The relative positions of in- 
 let and outlet are often governed to some extent by the building 
 construction, but if possible, they should both be located upon 
 the same side of the room. Fig. 4 shows common arrangements. 
 
 The most satisfactory method is to place the vent outlet in an 
 inside wall, as this prevents the air within it from becoming 
 chilled and thus reducing the velocity of outflow. In churches, 
 halls, and theatres, where the occupants are seated close together, 
 the best results are obtained by introducing the air through a 
 large number of small openings evenly distributed over the entire 
 floor space occupied by seats or pews. In rooms of this kind, 
 the animal heat generated by the bodies of the audience, warms 
 the entering air still more and causes it to rise continuously from 
 floor to ceiling. By admitting the supply in this manner the 
 impurities given off by respiration are at once disposed of. If 
 the fresh air were admitted from above, the downward currents 
 and those rising from the audience would conflict, and much of 
 the impure air would be carried back to the breathing line. 
 
VENTILATION 
 
 29 
 
 The discharge ventilation from halls and churches should, in 
 general, be partly through registers near the floor and partly 
 through ceiling vents. The latter method should be emplagred 
 when the air supply is at the flow, and the vents in any case shfflHld 
 be of sufficient size to care for the entire ventilation in warm 
 weather or when the room is crowded. 
 
 b-^»^»^':t:'!»'^^^^^^^^:^ ^!^^ 
 
 ^^^^y>^^»^y^^^^»^^ ^y^>^^^^^ 
 
 ?y!i^^^^^»^yty:»i?i:i;^y^-^Ny 
 
 OUTSIDE WALL OUTSIDE WALL OUTSIDE WALL 
 
 Fig. 4. Arrangements of Inlet and Outlet. 
 
 In theatres the foul air should be discharged partly through 
 the main ceiling and partly at the rear, from the low spaces be- 
 neath the balconies. 
 
 Measurement of Velocity. 
 
 The velocity of air in ventilating ducts and flues is measured 
 directly by an instrument called an anemometer. A common form 
 of this instrument is shown in Fig. 5. It consists of a series of 
 flat vanes attached to an axis, and a series of dials. The rotation 
 of the axis causes a motion of the hands in proportion to the 
 velocity of the air, and the result in feet in any given length of 
 time can be read directly from the dials. 
 
 Measurements for the total air supply to a building are com- 
 monly made at the fresh-air inlet windows, while the supply to 
 an individual room is measured at the register. 
 
 It should be noted in this connection that the air is cool in one 
 case and heated in the other so that due allowance must be made 
 for expansion when comparing the results. 
 
 For approximate results the anemometer may be moved slowly 
 across the opening in either vertical or horizontal parallel lines, 
 so that the reading will be made up of velocities taken from all 
 parts of the opening. Readings one minute in length are usually 
 sufficient for rough work. 
 
30 HEATING AND VENTILATING PLANTS 
 
 When more accurate results are desired, the opening should be 
 divided into squares, the number depending upon the degree of 
 accuracy required. Readings are then taken at the center of each 
 square and the average of all the readings used in determining 
 the final result. 
 
 If the opening is comparatively small, the division into squares 
 can usually be made by the eye, but for those of larger size it is 
 better to stretch light twine across, attaching it to tacks driven 
 into the casing. 
 
 Fig. 5. Anemometer. 
 
 When air is delivered to a room through a wall register, the 
 velocity is much greater at the top than at the bottom, and if 
 sufficiently high, there may be a reverse or outward current 
 through the lower part. In computing the average of several 
 readings, the negative or reverse readings must be subtracted 
 from the total. 
 
 For approximate results, as when roughly adjusting the air 
 flow to different rooms, a single reading may be taken while 
 holding the anemometer at or slightly above the center of the 
 register. 
 
 In the case of vent or discharge openings the velocity is more 
 uniform over the whole area, but for accurate results the same 
 methods of measurement should be used as already described 
 for the inlets. 
 
 When taking measurements of air-flow at grilles and registers, 
 the anemometer should be held about 4 inches from the face of 
 the fretwork, as at this distance the jets of air issuing through 
 
VENTILATION 31 
 
 the various openings, become practically united in a solid stream 
 or current having a sectional area equal to the over-all or gross 
 area of the register face. If more accurate results are required, 
 the register should be removed and measurements taken in the 
 unobstructed opening. 
 
 Cost of Ventilation. 
 
 The cost of ventilation depends upon the same factors as the 
 cost of heating, with the addition of the volume of air to be 
 supplied. In making estimates of this kind it is customary to 
 compute the cost per hour for the average temperature of the 
 heating season, and multiply this by the number of hours during 
 which ventilation is to be provided. 
 
 C y^T 
 
 The heat required is computed by the formula — ^ — , pre- 
 viously given, in which C is the cubic feet of air supplied per 
 hour, and T the rise in temperature, which for New England and 
 the Middle States, may be taken as 35° Knowing the B. T. U. re- 
 quired, the cost of fuel is determined in the same manner as for 
 heating. 
 
 The heat supplied for ventilation is more easily regulated than 
 in the case of warming, and the results given by the above method 
 will be sufficiently accurate for all approximate work without 
 correction. 
 
CHAPTER IV. 
 FURNACE HEATING. 
 
 Furnaces are usually installed by the makers or their agents, 
 under a guarantee to produce certain stated results ; hence the 
 engineer or architect ordinarily has little to do with the prepara- 
 tion of plans or specifications for this class of work. It often 
 happens, however, that he is required to pass upon the plans of 
 different agents or contractors, so that a general knowledge of 
 this method of heating is essential in connection with those of 
 other systems. 
 
 Advantages and Disadvantages. — Furnace or hot-air heating 
 is the simplest system in common use and the least expensive to 
 install. It furnishes fresh air for ventilation, warms up the rooms 
 quickly in the morning, is easily regulated as to quantity of heat 
 supplied, is free from damage to the apparatus by freezing in 
 unoccupied rooms, and avoids the flooding of floors and ceilings 
 from leaking air valves. 
 
 The chief disadvantage is the unevenness of the heat supply 
 to different parts of the building, and the difficulty experienced 
 in forcing the warm air into certain rooms in case of high winds. 
 Other objections of less importance are the ease with which dust 
 and ashes are carried through the flues from the basement to the 
 upper part of the house, and the dry and overheated quality of 
 the air when the furnace is too small for its work. Unevenness 
 of heat distribution may be largely overcome by locating the fur- 
 nace so as to shorten the hot-air pipes leading to northerly rooms, 
 especially those on the first floor. Horizontal pipes should be 
 limited in length, and made of ample size, while the furnace 
 should be set low enough to provide for a decided pitch upward 
 to the bases of the vertical flues. Overheated air may be avoided 
 by using a furnace with generous air passages and heating sur- 
 faces so that a comparatively large volume of air will be supplied 
 at a moderate temperature. While the air in furnace heating may 
 seem dryer than with steam or water, there is really no difference, 
 
 32 
 
FURNACE HEATING 33 
 
 as the amount of moisture in either case depends upon other 
 conditions. The relative humidity of the hot air entering the 
 registers is low, due to its high temperature, but as it becomes 
 diffused and cools to the normal temperature of the rooms, the 
 humidity is practically the same as in other systems of heating. 
 Passing the air through a furnace neither increases nor diminishes 
 the amount of moisture unless furnished with an evaporating pan. 
 
 In general, the conditions required for successful furnace heat- 
 ing are more easily realized in small houses than in large ones, 
 and for this reason its field is somewhat limited. However, for 
 houses of six to eight rooms this is probably one of the most 
 satisfactory systems of heating when all points are considered. 
 
 Buildings of larger size may also be successfully warmed with 
 hot-air furnaces, under certain conditions, but require special 
 care in design and installation. 
 
 Furnaces. 
 
 Types of Furnaces. — Furnaces may be divided into two gen- 
 eral types, known as "direct-draft" and "indirect-draft." 
 
 In the direct-draft furnace the gases pass from the top of the 
 dome or combustion chamber into the smoke pipe by way of 
 passages more or less direct. 
 
 Fig. 6 shows a well designed furnace of this general type. 
 
 The gases in this case are made to pass around a radiator by 
 means of suitable diaphragms or deflectors, and thus give up a 
 good share of their heat before passing into the chimney. 
 
 The passage of the fresh air over the various heating surfaces 
 of the furnace is indicated by the arrows. It enters the casing at 
 the bottom and passes upward around the fire-pot and dome, then 
 through and around the radiator and into the delivery or air pipes 
 at the top of the casing. In some of the cheaper forms of fur- 
 naces of this type, no radiator is provided, and the gases pass 
 directly from the dome into the smoke-pipe. 
 
 Fig. 7 shows a common form of indirect-draft furnace. 
 
 In this type the gases pass downward to a radiator located 
 near the base, then upward through another flue to the smoke- 
 pipe. A damper is provided to give a direct connection with the 
 chimney, for carrying off the increased amount of gas which is 
 formed when coal is first put on. 
 
34 
 
 HEATING AND VENTILATING PLANTS 
 
 In the case of schoolhouses, halls and churches, where a large 
 volume of air is required for ventilating purposes, special forms 
 are often employed in which the ratio of heating surface to grate 
 surface is large as compared with the ordinary house-heating 
 
 Fig. 6 . Direct Draft Furnace . 
 
 furnace. This type is usually set in a brick chamber and 
 may be used in connection with a fan, if desired, to make 
 the air supply uniform under all conditions. A furnace of this 
 general type, without the brick casing, is shown in Fig. 8. 
 
 Materials of Construction. — The materials employed in furnace 
 
FURNACE HEATING 
 
 35 
 
 construction are cast-iron, wrought iron, or steel plate, and a com- 
 bination of the two. Cast-iron is less affected by corrosion, re- 
 quires a smaller number of joints, and owing to its greater thick- 
 ness, holds the heat better and maintains a more even tempera- 
 
 Fig. 7. Indirect Draft Furnace. 
 
 ture. Wrought iron, on the other hand, transmits the heat more 
 rapidly, but lacks the storage capacity of cast-iron. Furnaces of 
 either material should give satisfactory results when properly 
 constructed. 
 
 Fire-Pot. — This is commonly made in one of two ways, either 
 entirely of cast-iron or of steel plate lined with firebrick. The 
 former is more effective as heating surface than a lined one, and 
 
36 
 
 HEATING AND VENTILATING PLANTS 
 
 where the latter is used, it is necessary to increase the size of 
 radiator or dome to offset it. 
 
 Dome. — The space above the lirepot, commonly called the 
 dome or combustion chamber, should be of generous size in order 
 that the gases of combustion may become thoroughly mixed with 
 the entering air. If restricted, as is commonly done in the cheaper 
 grades, incomplete combustion will follow, with a resulting loss 
 in efHciency. 
 
 Radiator. — The radiator, seen in both Figs. 6 and 7, is always 
 
 Fig. 8. Furnace with Large Ratio of Heating Surface to Grate Area. 
 
 provided in furnaces of the best make. Its use is that of a form 
 of reservoir, in which the gases are stored until an opportunity 
 is provided for them to give up a portion of their heat to the air 
 passing through the furnace. 
 
 Radiators are constructed both of cast-iron and steel plates, 
 and also in some cases of a combination of the two. The best 
 location is a matter of some question; if placed at the bottom, as 
 in Fig. 7, it is surrounded by air at the lowest temperature and 
 is therefore more effective for 'a given area, but on the other 
 hand, this condition is liable to cause the condensation of certain 
 gases which form corroding acids and thus injure the iron. 
 
FURNACE HEATING 37 
 
 Heating Surface. — The heating surface of a furnace is made 
 up of the fire-pot, dome, flues, radiator, and extended surfaces, 
 such as ribs or pins. 
 
 The ratio of heating surface to grate surface, and also the 
 effectiveness of the former, varies greatly in different makes. In 
 a considerable number examined, this was found to run from 10, 
 in some of the larger sizes, to 85 in the smaller ones. The smaller 
 ratio is often offset by using a larger furnace and reducing the 
 rate of combustion per square foot of grate. This may be done 
 with good results if the combustion is not so slow as to become 
 wasteful of fuel. 
 
 Casing. — ^Galvanized iron casings are used almost entirely at 
 the present time, except for some of the larger sizes where brick- 
 work is employed. Insulation is secured in different ways, per- 
 haps the most common method being to provide an inner casing 
 of black iron, with an air space of about an inch between that 
 and the outer one. 
 
 Air Passages. — The space required between the furnace and 
 casing for the passage of air will vary under different conditions. 
 This is commonly based upon the velocity, and may be taken as 
 300 feet per minute for dwelling houses ; 400 feet for schools, 
 churches, and halls, with a gravity flow; and 600 feet where a 
 fan is employed. 
 
 Grate. — The grate is an important part of any heater, whether 
 hot-air furnace or boiler. The best makes are usually equipped 
 with rotating triangular bars which cut a slice of ashes and 
 clinker from the bottom of the fire when revolved. In others, 
 some form of rocking grate is used. The difficulty with any 
 grate is the liability of unburned fuel falling into the ash pit when 
 the fire is shaken. 
 
 Evaporating Pan. — As mentioned in a previous chapter, the 
 supply of a certain amount of moisture to the entering air is an 
 important feature in any system of warming. This is accom- 
 plished in the case of furnace heating by means of an evaporating 
 pan placed inside the furnace casing. To be effective, this must 
 have a large capacity and be placed somewhat above the fire-pot 
 to bring the water in contact with the warm air, thus ensuring a 
 
38 HEATING AND VENTILATING PLANTS 
 
 more rapid evaporation and avoiding any possibility of freezing 
 in extremely cold weather. 
 
 Some of the best results have been secured by the use of a pan 
 running entirely around the furnace, and supplied automatically 
 through a pipe extending to an outside tank containing a ball 
 cock. 
 
 Determining Size of Furnace. 
 
 There are various methods employed for determining the size 
 of furnace for any given case. The simplest of these is based 
 on the cubit feet of space to be warmed. While this may be 
 safely used in many cases by an experienced man, it does hot 
 take into account the relation between wall and window areas, 
 the kind of building construction, nor the amount of ventilation 
 required. 
 
 This method is often convenient for approximate computa- 
 tions and applies fairly well to the average dwelling house of 
 regular form. It is much better, however, to employ one of the 
 more exact methods, based on the heat loss by transmission and 
 leakage, as these take into account the varying conditions noted 
 above and give more accurate results. 
 
 These methods, in turn, are divided into two classes ; those 
 which consider the heating capacity only, without reference to 
 the amount of air supplied, and those in which a definite air 
 volume is also provided for. 
 
 Efficiency. — In determining the size of furnace by any of these 
 methods, it is important to know approximately what proportion 
 of the heat generated may be utilized for warming purposes. 
 This proportion, called the efficiency, commonly varies from 50 
 to 70 per cent, with 60 per cent as a fair average. Under these 
 conditions about 8,000 B. T. U. will be transmitted from the 
 furnace to the air for each pound of coal burned on the grate. 
 
 Rate of Combustion. — This will vary somewhat with the size 
 of furnace and the care which it receives. Under ordinary con- 
 ditions it will run from about 3% pounds of coal per square foot 
 of grate per hour, in the smaller sizes up to 5 pounds in the larger 
 ones. 
 
FURNACE HEATING 39 
 
 For grates 18 and ,30 inches in diameter, we may assume a 
 combustion of 3.5 pounds of coal per square foot per hour, which 
 will supply 3.5 X 8,000 = 3,8,000 B. T. U. In like manner, 3i3 
 and 34-inch grates will have a combustion of 4 pounds and 
 produce 3.3,000 B. T. U. ; 36 and 38-inch grates, 4.5 pounds, and 
 produce 36,000 B. T. U. ; 30 and 3i3-inch grates, 5 pounds, and 
 produce 40,000 B. T. U. 
 
 Thermal Unit Methods. 
 
 In dwelling houses, and similar buildings, where the cubic feet 
 of space per occupant is large, it is customary to consider only 
 the heating capacity of the furnace, for, with the usual range of 
 temperatures employed, the amount of air required to bring in 
 the necessary heat will be ample for ventilating purposes also. 
 In the case of buildings requiring more generous ventilation, like 
 schools and churches, special provision must be made as de- 
 scribed in Chapter XVI. 
 
 In the usual method of determining the size of furnace, where 
 heating capacity only is to be considered, the first step is to com- 
 pute the heat loss from each room through transmission and 
 leakage, by means of the factors in Tables IV. and V., and 
 take the sum of these results as a basis for computing the 
 required grate area. The heat delivered to a building by a 
 furnace may be considered as made up of two parts; that re- 
 quired to raise the temperature of the outside air to 70°, the 
 normal temperature of the room, and an additional amount, 
 sufficient to replace that lost by transmission and leakage. In 
 practice the air is usually delivered to the rooms at a tempera- 
 ture of about 130° with zero conditions outside, so that 
 
 70 
 tj-oTT of the heat given to the entering air may be considered as 
 
 making up the first part mentioned above, leaving —^ available 
 for purely warming purposes. From this, it is evident that the 
 
 total heat supplied to the entering air must be equal to 1 : ..^r. 
 = 3.1 times that lost by transmission. When the lowest outside 
 
40 HEATING AND VENTILATING PLANTS 
 
 temperature is taken as 10° below zero, multiply by 2.3, and 
 when it is taken as 10° above zero, multiply by 2. 
 
 Example. — An average well7built two-story wooden dwelling, 
 30 ft. X 40 ft. in size, with a height of 17 ft. is to be heated by a 
 furnace. Assuming .1/6 the total exposure to be of glass (single 
 sashes), what will be the required grate area for warming the 
 building to 70° in zero weather, with a combustion of o pounds 
 of coal per square foot of grate? 
 
 Total exposure, (30 + 30 + 40 + 40) X l? = 2,380 sq. ft. 
 Glass exposure, 2,380 X 1/6 = 400 sq. ft. (approx.) 
 Net wall exposure, 2,3i80 — 400 = 1,9-80 sq. ft. 
 Factor for walls, wooden construction, (Table IV.) 21 
 Factor for glass, single sash, (Table IV.) 84 
 Factor for leakage, 1.1 
 Factor for cold attic, 1.1 
 Factor for total exposure, (Table V.) 1.16 
 Making the computations, we have 
 
 Wall, 1,980 X 51 = 41,580 
 
 Glass, 400 X 84 = 33,600 
 
 75,180 B. T. U. 
 Correcting for leakage, cold attic, and exposure, gives 75,180 X 
 1.1 X 1.1 X 1-16 = 105,252 B. T. U. per hour by transmission. 
 Multiplying this by the factor 2.1 and dividing by 40,000, the 
 B. T. U. furnished per square foot of grate area per hour, calls for 
 105,25.2 X 2.1 
 
 — ipoo— = °-^ ''I- *'• ^'"-^^ ^'^^- 
 
 Cubic Space Method. 
 
 Manufacturers of furnaces usually base their ratings on the 
 cubic space which they are supposed to heat. Table IX. has been 
 prepared on this basis, and while it is considerably more conserv- 
 ative than the average table of this kind, it will be found to give 
 a somewhat smaller furnace that the more exact method, when 
 applied to the same building. For example, in the preceding 
 problem the building has a cubic contents of 30 X 40 X 1''' = 
 
FURNACE HEATING 
 
 41 
 
 20,400 cubic feet, and, according to Table IX., calls for a grate 
 
 area of 
 
 3.7 + 4.3 
 
 = 4 square feet, as against 5.5 square feet com- 
 
 puted by the more exact method. 
 
 The discrepancy between the two methods is probably due 
 partly to the fact that the former assumes the total air supply to 
 be taken from outside at all times, while the latter counts on re- 
 circulating a portion of the air in the coldest weather, and partly 
 to a higher temperature of the entering air. These various points 
 
 Table IX. 
 Cubic Feet of Space Heated by Ftjrnaces or Different Sizes. 
 
 
 Sq. ft. 
 of grate 
 
 Cubic ft. of space heated to 70° 
 
 Diameter 
 
 
 
 of 
 fire-pot 
 
 Outside temperature 
 
 area 
 
 
 
 
 
 
 —10° 
 
 0° 
 
 -1-10° 
 
 18 
 
 1.8 
 
 6,000 
 
 8,000 
 
 10,000 
 
 20 
 
 2.2 
 
 8,000 
 
 10,000 
 
 12,000 
 
 22 
 
 2.6 
 
 10,000 
 
 12,000 
 
 14,000 
 
 24 
 
 3.1 
 
 12,000 
 
 14,000 
 
 18,000 
 
 26 
 
 3.7 
 
 14,000 
 
 18,000 
 
 22,000 
 
 28 
 
 4.3 
 
 18,000 
 
 22,000 
 
 26,000 
 
 30 
 
 4.9 
 
 22,000 
 
 26,000 
 
 30,000 
 
 should always be taken into account when making approxima- 
 tions by the cubic space method. 
 
 Auxiliary Eqviiptnent. 
 
 Smoke-Pipe. — The smoke-pipe should be carried to the chim- 
 ney flue in a direct line if possible. The top of the pipe should 
 be at least 10 inches from unprotected beams, and not less than 
 8 inches from those covered with asbestos or tin. Town and 
 city requirements vary somewhat in regard to this matter. 
 
 The size of the pipe is usually fixed by the smoke outlet from 
 the furnace, but should not in general be made less than 1/7 of 
 the grate area. 
 
 Chimney. — While the chimney forms a part of the building 
 construction, it should be built subject to the approval of the 
 heating engineer. The following, based upon the diameter of 
 
42 
 
 HEATING AND VENTILATING PLANTS 
 
 fire-pot, will cover about the usual range of sizes for dwelling 
 house work. 
 
 Table X. 
 
 Chimney Sizes for Furnace Heating. 
 
 For Hard Coal 
 
 Diameter of 
 fire-pot 
 
 Bfictangular 
 tile 
 
 Round 
 tile 
 
 Brick 
 
 18" to 22" 
 24" to 30" 
 
 8K"X 8H" 
 S%" X13" 
 
 8" 
 10" 
 
 8" X 8" 
 8" X12" 
 
 For Soft Coal 
 
 18" to 22" 
 24" to 30" 
 
 8M"X13" 
 13" X13" 
 
 10" 
 12" 
 
 8" X12" 
 12" X12" 
 
 Cold-Air Box. — This should* be made large enough to supply 
 a volume of air sufficient to fill all of the hot-air pipes at one 
 time. If too small, the distribution will be uneven and the base- 
 ment become overheated from lack of air to carry away the heat 
 which is generated. It is common practice to make the area of 
 the cold air box about 0.8 that of the combined area of the hot- 
 air pipes. This should be taken as the minimum size, for if 
 made too large it can easily be throttled down by means of the 
 slide to suit the requirements. 
 
 The location of the inlet should be such that the prevailing 
 winds will blow into it, thus making use of the outside wind pres- 
 sure to force the air through the pipes and registers. In most 
 cases the air supply should be taken from the north or west side 
 of the house. 
 
 The cold-air box is commonly made of matched sheathing or of 
 galvanized iron, and should be furnished with a wire netting over 
 the outer end, and a regulating damper for use in case of high 
 winds. A door is usually provided for admitting air to the cold- 
 air box from the basement when it is extremely cold and windy 
 outside. Small electric fans from 13 to 16 inches in diameter 
 and run at speeds not exceeding 1,000 to 1,100 revolutions per 
 minute are sometimes placed in the cold-air box and used to 
 accelerate the flow of air through the furnace pipes for a short 
 
FURNACE HEATING 
 
 43 
 
 time in the morning or when certain rooms fail to heat properly 
 during high winds. 
 
 Cold-Air Room. — A very desirable arrangement, when space 
 allows, is the use of a cold-air room, into which the air flows 
 before entering the duct leading to the furnace. This acts as an 
 equalizing chamber and overcomes to a considerable extent the 
 effect of sudden gusts of wind. For the average size furnace 
 this is made about 4 feet square and extends from the floor to 
 ceiling of the basement. An arrangement of this kind is shown 
 in Fig. 9. 
 
 Fig. 9. Arrangement of Cold-Air Room. 
 
 When there is considerable dust or soot in the air, baffle plates 
 or cheese-cloth screens may be introduced for removing a portion 
 of it. When the latter are employed, the area of the filter surface 
 should be from 15 to 20 times that of the cold-air duct, and the 
 screens should be removed and cleaned every 10 to 30 days, ac- 
 cording to their condition. 
 
 Return Flues. -^Th.&se. are passages by means of which a cer- 
 tain amount of air may be returned to the furnace from the 
 inside of the house instead of taking the whole supply from out 
 of doors. . Only one or two of these are commonly provided in a 
 house of average size, usually one from the front hall and pos- 
 sibly others from important rooms on the northerly or westerly 
 
44 HEATING AND VENTILATING PLANTS 
 
 sides of the house, which are difficult to heat in windy weather. 
 They are connected with the cold-air duct near the furnace, in 
 such a manner that the outside air cannot enter them directly and 
 so impede their action. Recirculation of air should only be prac- 
 ticed for quick warming in the morning and at other times when 
 the outside wind pressure causes an excessive inleakage of cold 
 air. Switch dampers, accessible from the first floor, should be 
 provided for regulating the relative amounts of outside and in- 
 side air, in order to meet the varying requirements of extremely 
 cold or windy weather. 
 
 Hot-Air Pipes. — Round pipes of heavy tin or galvanized iron 
 are used for connecting the casing of the furnace with the regis- 
 ters. While round pipes give the best results, it is not always 
 possible to provide a sufficient space for them and flat or oval 
 pipes must be used instead. 
 
 The size of the hot-air pipe, in any given case, is based upon 
 the amount of air required to carry the computed heat supply to 
 the room. Each cubic foot of air warmed from zero to 130° 
 requires 130-^-55 =2.34 B. T. U. It has already been shown 
 
 that in zero weather only tj-ttq of the heat contained in the enter- 
 ing air is available for offsetting transmission losses, so that only 
 
 2.34 XyoQ= 1.1 B. T. U. are supplied by each cubic foot for 
 
 this purpose. 
 
 Hence, the volume of air required per hour, at a temperature 
 of 130°, to warm a given room, may be found by dividing the 
 total loss by transmission and leakage in B. T. U. per hour by 
 1.1, which gives the air required in cubic feet. While conditions 
 vary somewhat with changes in the outside temperature, the final 
 result remains very nearly constant, and the factor 1.1 may be 
 used for all ordinary temperatures. 
 
 Knowing the volume of air to be supplied to a room in a given 
 time, the area of pipe may be found by dividing this by the prob- 
 able velocity within the pipe. 
 
 The air velocity for given temperature differences may be com- 
 puted theoretically by the formula for air flow given in Chapter 
 I., but it is better in practice to use velocities based upon actual 
 
FURNACE HEATING 45 
 
 tests made under working conditions. These may be taken as 
 350, 335, and 400 feet per minute for the first, second and third 
 floors respectively. 
 
 Table XI. will be found useful in determining the diameters of 
 hot-air pipes for different conditions. 
 
 Example. — The heat loss by transmission from a room on the 
 first floor is 13,200 B. T. U. per hour. What should be the diam- 
 eter of hot-air pipe connecting it with the furnace? 
 
 Table XL 
 Areas of Round Hot-Air Pipes. 
 
 Diameter of pipe, 
 inches 
 
 Area in square 
 
 Area in square 
 
 inches 
 
 feet 
 
 28 
 
 0.196 
 
 38 
 
 0.267 
 
 50 
 
 0.349 
 
 64 
 
 0.442 
 
 79 
 
 0.645 
 
 95 
 
 0.660 
 
 113 
 
 0.785 
 
 133 
 
 fl.9S2 
 
 1B4 
 
 1.07 
 
 li- 
 
 1.23 
 
 201 
 
 1.40 
 
 10 
 
 11 
 
 12 
 13 
 14 
 15 
 16 
 
 13,200-^ 1.1 =13,000 cu. ft. of air required per hour, or 13,000 
 -^ 60 = 300 per minute. Dividing this by the assumed velocity 
 for first floor rooms, calls for an area of 200 -^ 350 = 0.8 sq. ft. 
 which corresponds most nearly to a 13-inch pipe. Under ordinary 
 conditions, the horizontal runs of pipe between the furnace and 
 the bases of the vertical flues should not be over li3 or 13 feet. 
 If greater lengths are required, in special cases, they should be 
 increased in size and given a good pitch upward. 
 
 Common methods of running the horizontal pipes are shown 
 in Figs. 10 and 11. 
 
 The first of these is the better arrangement on account of the 
 greater pitch, and should be used whenever the height of the 
 basement allows. An adjusting damper should be placed in each 
 pipe near the furnace for equalizing the air flow and thus giving 
 to each room its proper share. 
 
 In general, each room should be supplied through a separate 
 pipe, except in special cases, as when two small or unimportant 
 rooms adjoin one another upon an upper floor. When flat pipes 
 
46 
 
 HEATING AND VENTILATING PLANTS 
 
 Fig. 10. Fig.lt. 
 
 Arrangement of Hot- Air Pipes in Basements. 
 
 are used much better results are obtained if the smaller dimension 
 is limited to 4 inches, or better, 5 inches. Special attention should 
 be given to protection against fire, and a clear space of at least ^ 
 inch should be allowed between the pipes and all wooden con- 
 struction. Further protection should be provided by tinning the 
 adjacent woodwork and covering in the pipes with wire lath, or 
 asbestos board instead of the usual wooden lath and plaster. 
 
 Table XII. gives the capacity of oval pipes. A 6-inch pipe 
 ovaled to 5 means that a 6-inch round pipe has been flattened out 
 
 
 Table XII. 
 
 Areas 
 
 OF Oval 
 
 HoT-AiR Pipes. 
 
 Ditnensi 
 
 on o£ pipe. 
 
 Area in square 
 
 inches 
 
 inches 
 
 6 ovaled to 5 
 
 37 
 
 7 ' 
 
 ' "3J 
 
 29 
 
 7 ' 
 
 " 4 
 
 31 
 
 7 ' 
 
 " 6 
 
 38 
 
 8 ' 
 
 " 5 
 
 43 
 
 9 ' 
 
 ' " 4 
 
 45 
 
 9 
 
 " 5 
 
 51 
 
 9 ' 
 
 " 6 
 
 57 
 
 10 ' 
 
 ' " 3J 
 
 46 
 
 10 ' 
 
 " 6 
 
 67 
 
 11 ' 
 
 " 4 
 
 58 
 
 11 
 
 " 5 
 
 67 
 
 12 ' 
 
 ' "3J 
 
 55 
 
 la 
 
 ' " 5 
 
 75 
 
 13 
 
 " 6 
 
 85 
 
 14 
 
 " 4 
 
 76 
 
 15 
 
 ' "35 
 
 73 
 
 19 
 
 " 4 
 
 96 
 
 20 
 
 ' "3J 
 
 100 
 
 to a thickness of 5 inches, and column two gives the resulting 
 area in square inches. 
 
 Registers. — These are usually of cast-iron, and provided with 
 
FURNACE HEATING 47 
 
 valves or vanes for closing when less heat is required or the 
 room is not in use. 
 
 The net area for the passage of air through a standard register 
 is generally about 60 to 70 per cent of the gross area, and should 
 
 Table XIII. 
 Standard Sizes of Registers for Various Diameters of Hot-Air Pipes. 
 
 Diameter of pipe, Size of register, 
 inches inches 
 
 6 6 by 10 
 
 7 7 by 10 
 
 8 8 by 18 
 
 9 9 by 14 
 
 10 10 by 14 
 
 11 11 by 16 
 13 12 by 16 
 
 13 14 by 20 
 
 14 14 by 22 
 IB 15 by 22 
 16 16 by 24 
 
 be from 15 to 20 per cent greater than the area of the pipe con- 
 necting with it. In practice it is customary to use a certain size 
 of register with a given diameter of pipe, as indicated in Table 
 XIII. 
 
 Table XIV. 
 
 Heating Stirpace in Fuknace for Combination Systems. 
 
 Square feet of direct 
 Kind of heating surface radiation supplied by 
 
 1 sg. ft. of heating surface 
 
 Cast-iron sections suspended above fire 15 to 20 
 
 Cast-iron sections in contact with fire 20 to 25 
 
 Pipe coil buried in fire 50 to 60 
 
 Combination Systems. 
 
 It often happens that there are rooms in a building too remote 
 to be easily reached by warm-air pipes, and where heat is of more 
 importance than generous ventilation. 
 
 In cases of this kind a "combination system," so called, may 
 usually be employed to advantage. An arrangement of this kind 
 consists in either placing a coil of pipe above the fire or intro- 
 ducing a hollow cast-iron section in the side of the fire-pot, 
 through which water may circulate. This forms an auxiliary 
 hot-water heating system which operates automatically in con- 
 nection with the hot-air system. 
 
48 HEATING AND VENTILATING PLANTS 
 
 The size of direct radiator, in square feet, for any given room 
 may be found by dividing the total heat loss from the room in 
 B. T. U. per hour, in zero weather, by 160. The amount of heat- 
 ing surface to be provided in the furnace will depend upon its 
 location and character, and the square feet of radiating surface 
 to be supplied. For average conditions, a temperature of 160° 
 may be maintained in the radiators by using the ratios given in 
 Table XIV. 
 
 When combinations of the above surfaces are used, an average 
 ratio should be employed, depending upon the existing propor- 
 tions. The pipe connections between the furnace and radiators 
 are practically the same as in ordinary hot-water heating and 
 may be obtained from Chapter IX. 
 
 Comparative Costs. 
 
 A comparison of the costs of installing and operating hot-air, 
 steam and hot-water systems recently published by the American 
 Radiator Company is given below. These results are based on 
 reliable data and are as follows: 
 
 Hot Air Steam Hot Water 
 
 Approximate percentage of cost to whole building 7 10 12 
 
 Relative cost of operation 18.5 13.5 10 
 
CHAPTER V. 
 BOILERS. 
 
 The successful operation of any system of heating employing 
 steam or hot water as the medium of transmission is largely de- 
 pendent upon the boiler or "heater. No matter how carefully the 
 radiation and piping may have been designed and installed, unless 
 the boiler is of sufficient size and its parts properly proportioned, 
 the entire system is likely to prove unsatisfactory in its results, 
 both as regards heating capacity and economy of operation. 
 Therefore, a thorough understanding of the requirements of an 
 efficient boiler is essential to the design of any heating plant, 
 whether large or small. 
 
 Types of Heating Boilers. 
 
 The types of boilers used for. steam and hot-water heating 
 are practically the same, the principal difference being the 
 addition of a steam space to the former. It is also important 
 in this case that the water passages extend more directly from 
 top to bottom in order to assist in the liberation of steam. 
 
 For houses of small size the round cast-iron boiler is commonly 
 employed, although many of the sectional boilers are also adapted 
 to this purpose. These boilers usually have grates from 15 to 3i2 
 inches in diameter, although in some makes, 36-inch grates are 
 furnished. The Magee boiler, shown in Fig. 1:3, is typical of this 
 general form. 
 
 Sectional boilers of various designs are commonly used for 
 larger buildings. These are made in different sizes, some of 
 which have grates 4 feet in width by ^8 feet in length. It should 
 be said, however, in this connection, that the grate for a hand- 
 fired boiler should never be over 60 inches in length, and 48 to 
 54 inches is better. With a long grate it is difiScult, if not im- 
 possible, properly to care for the fire on the rear portion and 
 more satisfactory results are obtained by using two boilers with 
 shorter grates, than with a single large one. This also gives the 
 
 49 
 
50 HEATING AND VENTILATING PLANTS 
 
 advantage of a smaller boiler for use in spring and fall when 
 only a portion of the full capacity is required. Sometimes a 
 bridge-wall section is used, in which case the capacity of the 
 boiler is based on the heating surface, and the grate made short 
 enough for convenient hand firing. 
 
 The smaller size of grate is offset by operating the boiler at a 
 
 Fig. 12. Magee Boiler. 
 
 higher rate of combustion and the efficiency is maintained by in- 
 creasing the ratio of heating to grate surface. 
 
 This arrangement is only recommended where there is a strong 
 chimney draft, and in cases where the boiler can be fired at 
 rather frequent intervals. 
 
 Sectional Boilers are of two general types, the first of which 
 is well illustrated by the Mercer hot-water boiler shown in Fig. 
 13. This is made up of slabs or sections, each one of which is 
 connected by nipples with headers or drums at the top and sides. 
 The gases from the fire pass backward and forward through flues 
 
BOILERS 
 
 51 
 
 formed by openings in the sections, as shown by the arrows, and 
 are finally taken off at the rear of the boiler. The forms for 
 steam and water are practically the same, except for the attach- 
 ment of gauges, water glass, etc., in the case of steam boilers. In 
 using boilers of this type care must be taken not to place too 
 many sections in a single unit, for the reasons already men- 
 tioned. The construction of this particular type of boiler ensures 
 
 Fig. 13. Mercer Boiler. 
 
 a good separation of the steam and water, and a stable water line 
 under ordinary working conditions. 
 
 The second type is illustrated by the Meal steam boiler, shown 
 in Fig. 14. In this design there are no drums, the sections being 
 joined directly together by means of push nipples at top and 
 bottom. 
 
 The Model boiler. Fig. 15, varies somewhat from those above 
 described, being made up of sections which increase the width 
 instead of the length. This form of boiler has a large proportion 
 of the heating surface exposed to the direct heat of the fire, and 
 the travel of the gases before reaching the smoke pipe is some- 
 
52 
 
 BEATING AND VENTILATING PLANTS 
 
 what less>than in the others just described. As the width of the 
 boiler is increased more fire doors are provided, so that all parts 
 of the grate can be easily reached, whatever the size. These 
 boilers have no drum, and the method of connecting the sections 
 is practically the same as in Fig. 14. 
 
 Fig. 14. Ideal Boiler. 
 
 In General. — There are many different designs of cast-iron 
 boilers for low pressure steam and hot-water heating, but the 
 ones shown serve to illustrate the distinctive features of some of 
 the more important types. Boilers having a drum connected with 
 each section by nipples usually give dryer steam and hold a 
 steadier water line than the second form, especially when forced 
 above their normal capacity. The steam in passing through the 
 openings between successive sections is apt to carry with it more 
 or less water and to partially choke the openings, thus tending 
 to produce uneven pressure in different parts of the boiler. This 
 is especially noticeable when two or more boilers are connected 
 
BOILERS 
 
 53 
 
 together in a battery. In the case of hot-water heating this ob- 
 jection disappears. 
 
 In order to adapt this type of boiler to steam work the open- 
 ings between the sections should be of good size, with an ample 
 steam space above the water line, and the nozzles for the dis- 
 charge of steam should be located at frequent intervals. 
 
 A pressure of from 1 to 5 pounds is usually carried on these 
 boilers, depending upon the outside temperature and the size of 
 
 Fig. 15. Model Boiler. 
 
 the piping connecting them with the radiators. The usual setting 
 is simply a covering of some kind of non-conducting material 
 like plastic magnesia or asbestos. 
 
 Tubular Boilers. 
 
 For buildings of larger size, such as schools, churches, halls, 
 etc., where the demand for steam is increased by the require- 
 ments of ventilation, horizontal tubular boilers are commonly 
 employed for heating purposes. 
 
 This type of boiler consists of a cylindrical shell of wrought 
 iron or steel with fire tubes terminating in the two flat ends. The 
 tubes are usually from two and one-half inches to four inches in 
 diameter, depending upon the length of the shell. The steam space 
 occupies about one third of the volume of the boiler and the re- 
 
54 
 
 HEATING AND VENTILATING PLANTS 
 
 mainder is filled with water which should normally stand from 
 four to six inches above the tops of the tubes. The- heads below 
 the water line are supported by the tubes, and the remaining por- 
 tions are stayed by through braces or diagonal stays. Fig. 16 
 shows a longitudinal section through a boiler of this kind. Hori- 
 zontal tubular boilers require a brick setting, drawings for which 
 are usually furnished by the makers. 
 
 Fig. 16. Horizontal Tubular Boiler. 
 
 Rating of Cast-Iron Boilers. 
 
 Boilers of this type are most frequently rated according to the 
 square feet of direct radiating surface which they will supply. 
 In estimating this, an allowance should be made for the exposed 
 piping, and a correction factor should also be applied for covering 
 any other losses which may occur. Under average conditions, 
 experience indicates that about 10 per cent should be allowed for 
 the former and the same amount for the latter, making a total in- 
 crease of 10 + 10 ^ ,20 per cent. That is, in computing the size 
 of boiler for a given plant, it should have sufficient capacity for 
 supplying an amount of radiating surface equal to 1.3 times that 
 contained in the radiators themselves. If the building contains 
 indirect radiation, count each square foot as one and one-half 
 of direct, in dwelling house and cottage hospital work, and as 
 two of direct in schoolhouses and churches. This simplifies 
 matters by placing the total radiating surface on a common basis. 
 
 The next step is to determine the heat units to be provided in 
 supplying this amount of radiation, which of course must equal 
 the total amount given off by the radiators, piping, etc. 
 
BOILERS 55 
 
 For cast-iron radiation of the usual type it is customary to 
 allow 250 B. T. U. per square foot of surface per hour for steam, 
 and 170 B. T. U. for hot water. 
 
 For circulation coils of wrought-iron pipe, use the number 3i90 
 and 190 for steam and water respectively. In buildings contain- 
 ing a small amount of radiation of this form, it may be counted 
 as cast-iron surface, the factor of safety making up for any slight 
 difference in efficiency. If, however, the proportion is large, as 
 often happens in stores, school-houses, etc., it should be multi- 
 plied by the higher efficiency (390) when determining the b.oiler 
 capacity. 
 
 When ventilation is to be furnished by means of a fan and 
 main heater, allow 1.3 B. T. U. for each cubic foot of fresh air 
 to be supplied per hour in zero weather. 
 
 Efficiency. — The efficiency of a boiler, that is, the ratio of the 
 heat absorbed by the water in the generation of steam, to the 
 heat value of the coal burned, is a variable quantity, depending 
 upon the design of the boiler, the ratio of grate to heating sur- 
 face, character and position of heating surface with reference to 
 the fire, and the rate of combustion. As all of these conditions 
 vary more or less in different makes and sizes of boilers, and 
 with the skill and care with which they are operated, it is evi- 
 dently impossible to fix an arbitrary efficiency to be applied to all 
 boilers of this kind. The only way to obtain the efficiency of a 
 given make and type of boiler is by actual test under standard 
 conditions. If this is not possible, it may be assumed that the 
 efficiencies of standard makes will run from 50 to 70 per cent, 
 with 60 per cent as a fair average. Taking the heat value of 
 anthracite coal as 13,500 B. T. U. per pound, it means that 
 13,500 X 0.6 = 8,100, or in round numbers, 8,000 B. T. U. will 
 be available for heating purposes from each pound burned on the 
 grate. 
 
 Rate of Combustion. — The next step is to determine the most 
 efficient rate of combustion. This will depend largely upon the 
 type and size of boiler and the ratio between heating surface and 
 grate surface. In a large number of tests of house-heating boil- 
 ers, this varied from 2.7 pounds of coal per square foot of grate 
 per hour, for boilers having 1 square foot of grate area, up to 
 6.6 pounds for those having an area of 30 square feet. 
 
56 HEATING AND VENTILATING PLANTS 
 
 ¥oT practical purposes cast-iron boilers may be divided into 
 four classes, as follows, according to their size. In Table XV., 
 column 2 gives the probable rate of combustion, and column 3 
 the B. T. U. supplied per square foot of grate per hour, on a 
 basis of 8,000 B. T. U. per pound of coal. 
 
 Ratio of Heating to Grate Surfcae. — It has been found by 
 experience that the highest efficiency is obtained with this type of 
 boiler when the rate of evaporation does not exceed 2 pounds of 
 steam per hour, per square foot of heating surface, which cor- 
 
 Table XV. 
 Rates of Combustion joe House-Heating Boilers. 
 
 Pounds of coal B.T.U. furnished 
 Square feet burned per sq. ft. per sq. ft, of 
 of grate of grate per hour grate per hour 
 
 1 to 5 4 32,000 
 
 6 to 10 5 40,000 
 
 11 to 15 6 48,000 
 
 16 to 20 7 56,000 
 
 responds approximately to a transmission of 2,000 B. T. U. per 
 squiare foot. If 8,000 B. T. U. per pound of coal are absorbed 
 through the heating surfaces of a boiler, then for a combustion 
 of 4 pounds and a transmission of 2,000 B. T. U., there should 
 
 be ' „ — = 16 square feet of heating surface for each square 
 
 foot of grate, to obtain the best results. In like manner the ratio 
 is found to be 20 for a combustion of 5 pounds ; 24 for 6 pounds, 
 and 28 for 7 pounds. 
 
 Example. — A building has 800 square feet of direct cast-iron 
 hot- water radiation. What should be the area of the boiler grate 
 and the minimum square feet of heating surface? 
 
 800 X 1-3 X 170 = 163,.200 B. T. U., and 163,200 -^ 32,000 
 = 5.1 square feet of grate required. This calls for a combustion 
 of practically 4 pounds of coal per square foot of grate per hour, 
 which in turn, requires a ratio of 16 between the heating and 
 grate surfaces. 
 
 Example. — A building contains ,2,000 square feet of direct cast- 
 iron steam radiation, and 400 square feet of indirect. What 
 should be the grate area, and ratio of heating to grate surface ? 
 
BOILERS 
 
 57 
 
 [2,000 + (.1.5 X 400)] X 1-^ X 350 = 780,000 B. T. U., and 
 780,000 -^ 48i,000 = 16.3 square feet of grate required. 
 
 This comes slightly above the limit set for a combustion of 6 
 pounds per hour, the rate assumed, but is very close to it and 
 gives a result on the side of safety. The ratio of heating to 
 grate surface for this rate of combustion is ,24. 
 
 
 
 Table XVI. 
 
 
 
 
 Proportions of 
 
 Tubular Boilers. 
 
 
 
 
 Diameter 
 
 LeDgth 
 
 
 Size 
 
 Diameter 
 
 No. 
 
 tubes, 
 
 tubes, 
 
 H. P. 
 
 of grate 
 
 boUer 
 
 tubes 
 
 in. 
 
 ft. 
 
 
 in. 
 
 36 
 
 34 
 
 2ii 
 
 8 
 
 14 
 
 30x36 
 
 36 
 
 
 
 9 
 
 15 
 
 30x42 
 
 36 
 
 
 
 
 10 
 
 17 
 
 30x42 
 
 38 
 
 
 
 
 11 
 
 19 
 
 30x48 
 
 42 
 
 34 
 
 
 3' 
 
 9 
 
 19 
 
 36x42 
 
 42 
 
 
 
 
 10 
 
 21 
 
 36x42 
 
 42 
 
 
 
 
 11 
 
 23 
 
 36x48 
 
 42 
 
 
 
 
 12 
 
 25 
 
 36x48 
 
 48 
 
 44 
 
 
 i 
 
 10 
 
 30 
 
 42x48 
 
 48 
 
 
 
 
 11 
 
 33 
 
 42x48 
 
 48 
 
 
 
 
 12 
 
 36 
 
 42x54 
 
 48 
 
 
 
 
 13 
 
 38 
 
 42x54 
 
 54 
 
 54 
 
 
 i 
 
 11 
 
 35 
 
 48x54 
 
 54 
 
 
 
 
 12 
 
 38 
 
 48x54 
 
 64 
 
 
 
 
 13 
 
 41 
 
 48x54 
 
 54 
 
 
 
 
 14 
 
 44 
 
 48x54 
 
 60 
 
 72 
 
 
 i 
 
 12 
 
 48 
 
 54x60 
 
 60 
 
 
 
 
 13 
 
 52 
 
 54x60 
 
 60 
 
 
 
 
 14 
 
 56 
 
 64x60 
 
 60 
 
 
 
 
 15 
 
 60 
 
 54x66 
 
 66 
 
 90 
 
 
 i 
 
 14 
 
 70 
 
 60x66 
 
 66 
 
 
 
 
 15 
 
 78 
 
 60x66 
 
 66 
 
 
 
 
 16 
 
 80 
 
 60x72 
 
 66 
 
 78 
 
 aVz 
 
 17 
 
 86 
 
 60x72 
 
 72 
 
 114 
 
 3 
 
 15 
 
 94 
 
 66x72 
 
 72 
 
 
 
 16 
 
 100 
 
 62x72 
 
 72 
 
 98 
 
 3k 
 
 17 
 
 106 
 
 72x72 
 
 72 
 
 
 
 
 18 
 
 113 
 
 72x72 
 
 Rating of Tubular Boilers. 
 
 The capacity of a boiler of this type is based upon the "horse 
 power" rating instead of the grate area. When used for heating 
 purposes it is customary to allow 15 square feet of heating sur- 
 face per horse power. Table XVI gives suitable proportions for 
 tubular boilers designed for this purpose, based on the usual rates 
 of combustion and evaporation obtained under average conditions. 
 
 One boiler house power furnishes approximately 30,000 
 B. T. U. per hour, so that by computing the total number of 
 heat units required for heating and ventilation, and dividing by 
 30,000, the result will be the boiler horsepower required. Table 
 
58 HEATING AND VENTILATING PLANTS 
 
 XVII. has been computed on this basis and gives the relation 
 between boiler horsepower and different types of radiating sur- 
 face. 
 
 Rate of Combustion. — This, with tubular boilers of good size, 
 used for heating, will commonly range from 8 to 10 pounds of 
 coal per square foot of grate per hour, while with small and 
 
 Table XVII. 
 Relation Between Boiler Horsepower and Radiation. 
 
 One boiler horse power will supply 
 Steam Hot-water 
 
 120 180 Sq. ft. of direct cast-iron radiation 
 
 100 150 Sq. ft. of direct wrought-iron coils 
 
 60 90 Sq. ft. of indirect cast-iron radiation 
 
 20 . . Sq. ft. of steam-blast coils 
 
 poorly cared for boilers it is often much less. In large plants, 
 where the conditions more nearly approach those of power work, 
 a somewhat higher rate will be obtained. 
 
 Rate of Evaporation. — This, like the rate of combustion, is a 
 variable factor, and depends largely upon the character and ar- 
 rangement of the heating surface and its relation to the grate 
 area. With boilers of medium size this will vary from 8 to 10 
 pounds of steam per pound of coal, but with smaller units, say 
 below 18 or 30 horsepower, it will often fall to 6 or 7 pounds, 
 due principally to less attention in cleaning and firing, 
 
 Grate Area. — The required size of grate may be computed 
 by the formula 
 
 H. P.X34.5 
 '^~ CXE 
 in which 
 
 5= grate area, in sq. ft. 
 
 C=rate of combustion. 
 
 £=rate of evaporation. 
 Assuming rates of combustion and evaporation of 10 and 8 
 pounds respectively, the above formula calls for a grate area of 
 0.43' square foot per H. P. 
 
 Ratio of Heating to Grate Surface. — This in tubular boilers 
 usually varies from 30 to 40 under ordinary conditions. Taking 
 the lower figure and assuming 15 square feet of heating surface 
 
BOILERS 
 
 59 
 
 per H. P., calls for a grate area of 0.5 square foot per H. P., which 
 agrees fairly well with the result obtained by the formula. The 
 grate areas in Table XVI. are based on 0.5 square foot per H. P. 
 for the small and medium sizes, while with the larger ones it 
 
 Table XVIII. 
 Chimney Dimensions. 
 
 Sq. ft. of 
 
 Sq. ft. of 
 direct 
 
 Height of chimney, in feet 
 
 direct 
 
 20 
 
 30 
 
 40 1 50 
 
 60 
 
 80 
 
 steam 
 
 hot-water 
 
 
 
 
 
 
 radiation 
 
 radiation 
 
 Diameter, or 
 
 side of square, in inches 
 
 250 
 
 375 
 
 8 
 
 7 
 
 7 
 
 7 
 
 6 
 
 6 
 
 500 
 
 750 
 
 10 
 
 9 
 
 9 
 
 8 
 
 8 
 
 7 
 
 750 
 
 1,150 
 
 11 
 
 11 
 
 10 
 
 10 
 
 9 
 
 9 
 
 1,000 
 
 1,500 
 
 13 
 
 12 
 
 11 
 
 11 
 
 11 
 
 10 
 
 1,500 
 
 2,260 
 
 15 
 
 14 
 
 13 
 
 13 
 
 12 
 
 12 
 
 2,000 
 
 3,000 
 
 17 
 
 16 
 
 15 
 
 15 
 
 14 
 
 13 
 
 3,000 
 
 4,500 
 
 21 
 
 19 
 
 18 
 
 17 
 
 17 
 
 16 
 
 4,000 
 
 6,000 
 
 24 
 
 22 
 
 21 
 
 20 
 
 19 
 
 18 
 
 5,000 
 
 7,500 
 
 26 
 
 25 
 
 23 
 
 22 
 
 21 
 
 19 
 
 6,000 
 
 9,000 
 
 28 
 
 27 
 
 25 
 
 23 
 
 23 
 
 21 
 
 7,000 
 
 10,300 
 
 30 
 
 29 
 
 27 
 
 26 
 
 25 
 
 23 
 
 drops to about 0.3, which may be safely used in well cared for 
 plants of large size. 
 
 Construction of Tubular Boilers. 
 
 The shell plates of heating boilers should not, in general, be 
 less than %-inch in thickness, with longitudinal seams of the 
 double-riveted, butt-joint type. The bracing is usually of the 
 diagonal form, the braces being of pressed steel without welds. 
 In the larger sizes the bracing may be a combination of "diag- 
 onal" and "through" bracing as shown in Fig. 16. This general 
 construction will give a boiler much stronger than is necessary 
 for the low pressures carried in heating, but allows for corrosion 
 and gives a large factor of safety which is especially desirable in 
 this class of work. 
 
 Chimneys. 
 
 Chimneys for power work, and for large heating plants using 
 tubular boilers, are based upon the boiler horsepower. In the 
 case of cast-iron heating boilers it is customary to proportion the 
 
60 
 
 HEATING AND VENTILATING PLANTS 
 
 chimney to the amount of direct radiation, or its equivalent, to 
 be suppHed. 
 
 Table XIX.* 
 Size of Chimneys with Corresponding Horse Power ob Boilers. 
 
 
 Height of chimney in feet 
 
 ft) (0 
 
 S.2 
 
 •Sill 
 
 a.2 
 
 a 
 
 11 
 
 s».s 
 
 .2 
 
 d 
 
 SO 
 
 60 
 
 70 
 
 80 
 
 90 
 
 100 
 
 110 
 
 125 
 
 150 
 
 175 
 
 200 
 
 
 5 
 
 Boiler horse-power 
 
 Lai's 
 
 18 
 
 23 
 35 
 49 
 65 
 84 
 
 25 
 38 
 54 
 72 
 92 
 115 
 141 
 
 27 
 
 41 
 
 58 
 
 78 
 
 100 
 
 125 
 
 152 
 
 183 
 
 216 
 
 
 
 
 
 
 
 
 
 .97 
 
 1.47 
 
 2.08 
 
 2.78 
 
 3.58 
 
 4.47 
 
 6.47 
 
 6.57 
 
 7.76 
 
 10.44 
 
 13.51 
 
 16.98 
 
 1.77 
 
 2.41 
 
 3.14 
 
 3.98 
 
 4.91 
 
 5.94 
 
 7.07 
 
 S.30 
 
 9.62 
 
 12.57 
 
 15.90 
 
 19.64 
 
 16 
 
 21 
 
 
 
 
 
 
 
 
 
 19 
 
 24 
 
 62 
 83 
 107 
 133 
 163 
 196 
 231 
 311 
 363 
 505 
 
 
 
 
 
 
 
 
 22 
 
 27 
 
 
 
 
 
 
 
 
 24 
 
 30 
 
 113 
 141 
 173 
 208 
 245 
 330 
 427 
 539 
 
 
 
 
 
 
 
 27 
 
 33 
 
 
 
 
 
 
 
 30 
 
 36 
 
 182 
 219 
 258 
 348 
 449 
 565 
 
 
 
 
 
 
 32 
 
 39 
 
 
 
 
 
 
 35 
 
 42 
 
 
 
 271 
 365 
 472 
 593 
 
 
 
 
 
 38 
 
 48 
 
 
 
 389 
 503 
 632 
 
 
 
 
 43 
 
 54 
 
 
 
 
 551 
 692 
 
 
 
 48 
 
 60 
 
 
 
 
 748 
 
 
 54 
 
 
 
 
 
 
 * From Kent's Mechanical Engineers' Pocketbook. 
 
 Table XVIII., given by Professor Carpenter, is adapted to all 
 types of heating boilers, both cast-iron and tubular, as it is based 
 upon the radiation to be supplied. 
 
 In general, it would not be best to use. a flue smaller than 8 
 inches for any size boiler on account of the accumulation of soot 
 and ashes, and it is well to allow something for this, even in the 
 larger sizes. 
 
 When the boiler plant is computed on a horsepower basis, and 
 includes ventilation or power requirements, the chimney size may 
 be taken from Table XIX. 
 
CHAPTER VI. 
 PIPE, FITTINGS AND VALVES. 
 
 In order to lay out a system of piping for either steam or hot- 
 ■water heating it is necessary to have a thorough understanding 
 of the materials employed for this class of work. This can best 
 be obtained by a careful study of the trade catalogues issued by 
 some of the leading manufacturers of material and equipment of 
 this kind. In making a selection, however, certain points should 
 be borne in mind, which will be touched upon briefly in the 
 present chapter. 
 
 Wrought-Iron Pipe. — Wrought-iron pipe is made "standard 
 ■weight," "extra strong" and "double extra strong." The standard 
 weight is commonly used for all pressures up to 125 pounds per 
 square inch. The heavier weights are often used for higher 
 pressures, although extensive tests seem to show that standard 
 weight pipe is sufficiently strong for all pressures used in ordinary 
 power work at the present time. 
 
 When particularly exposed to corrosion, it is well to use extra 
 h€avy pipe. This applies to feed lines, sealed returns, under- 
 ground drip piping, etc., and all lines that are to be run in places 
 which are not easily accessible. 
 
 Nearly all of what is commonly known as wrought-iron pipe is 
 in reality wrought steel. There seems to be no especial advan- 
 tage in using iron in place of a good quality of steel, although 
 some engineers prefer the former. 
 
 Wrought-iron pipe is not carried in stock to any great extent, 
 and if it is to be used in considerable quantity should be ordered 
 well in advance of the time required. 
 
 Table XX. gives the dimensions of standard wrought-iron 
 pipe. 
 
 The outside diameter of the extra strong and double extra 
 strong pipe is the same as that of the standard weight, the extra 
 thickness being added to the inside. This makes it possible to use 
 the same fittings with any weight of pipe. 
 
 61 
 
62 
 
 HEATING AND VENTILATING PLANTS 
 
 Standard weight pipe is employed for all heating work except 
 in special locations difficult to reach for repairs or renewal, as,, 
 noted above. Extra heavy pipe should be used under these con- 
 ditions as a precaution against corrosion rather than for addi- 
 tional strength. 
 
 Table XX.* 
 
 Dimensions of Standard Wroughi-Iron Pipe. 
 
 J i and smaller proved to 300 pounds per square inch by hydraulic pressure. 
 IJ and larger proved to 500 pounds per square inch by hydraulic pressure. 
 
 Ih 
 
 0) 
 
 
 
 
 
 
 
 
 
 
 
 
 
 a; 
 
 s 
 
 '■3 
 
 •a 
 
 
 s 
 
 (U «i 
 
 0)Og 
 
 
 
 0) 
 
 t 
 
 ■Jfl 
 
 ll 
 
 'to 
 
 S is 
 
 g 
 
 3 
 
 3 
 u 
 
 O aJ 3 
 
 
 a) 
 
 
 2 S 
 
 a 
 
 
 — (0 
 
 CJ 
 
 5g 
 
 +3 CTqj 
 
 5g^ 
 
 
 
 
 ■aiS- 
 
 
 1 
 
 I3 
 
 
 
 « a 
 
 
 0) S 3 
 
 k] P4O 
 
 .•0 
 
 '5 
 
 3 
 
 
 ^83 
 
 '3 
 
 In. 
 
 In. 
 
 In. 
 
 In. 
 
 In. 
 
 Ft. 
 
 Ft. 
 
 In. 
 
 In. 
 
 Ft. 
 
 Lb. 
 
 
 0.405 
 
 0.270 
 
 0.848 
 
 1.272 
 
 14.15 
 
 9.44 
 
 0.0572 
 
 0.129 
 
 2500. 
 
 0.243 
 
 
 0.54 
 
 0.864 
 
 1.144 
 
 1.696 
 
 10.50 
 
 7.0,5 
 
 0.1041 
 
 0.229 
 
 1386. 
 
 0.422 
 
 
 0.615 
 
 0.494 
 
 1.552 
 
 2,121 
 
 7.67 
 
 5.667 
 
 0.1916 
 
 0.368 
 
 751.5 
 
 0.561 
 
 
 0.84 
 
 0.623 
 
 1.957 
 
 2.652 
 
 6.13 
 
 4.502 
 
 0.3048 
 
 0.554 
 
 472.4 
 
 0.845 
 
 
 1.05 
 
 0.824 
 
 2.589 
 
 3.299 
 
 4.636 
 
 3.637 
 
 0.5333 
 
 0.866 
 
 270. 
 
 1.136 
 
 1 
 
 1.31B 
 
 1.048 
 
 3.292 
 
 4.134 
 
 3.6:9 
 
 2.903 
 
 0.8627 
 
 1.357 
 
 166.9 
 
 1.670 
 
 IJ 
 
 1.66 
 
 1.380 
 
 4.335 
 
 5.216 
 
 2.768 
 
 2.301 
 
 1.496 
 
 2.164 
 
 96.25 
 
 3.258 
 
 n 
 
 1.90 
 
 1,611 
 
 5.061 
 
 5.969 
 
 2.371 
 
 2.01 
 
 2.038 
 
 3.835 
 
 70.65 
 
 2.694 
 
 2 
 
 2.375 
 
 2.067 
 
 6.494 
 
 7.461 
 
 1.848 
 
 1.611 
 
 3.365 
 
 4.430 
 
 42.36 
 
 3.600 
 
 25 
 
 3.875 
 
 2.468 
 
 7.754 
 
 9.032 
 
 1.547 
 
 1.328 
 
 4.7&3 
 
 6.491 
 
 30,11 
 
 5.773 
 
 3 
 
 3.50 
 
 3.067 
 
 9.636 
 
 10.996 
 
 1.246 
 
 1.091 
 
 7.388 
 
 9.621 
 
 19.49 
 
 7.547 
 
 3S 
 
 4.00 
 
 3.548 
 
 11.146 
 
 12.566 
 
 1.0(7 
 
 0.956 
 
 9.887 
 
 12.566 
 
 14.56 
 
 9.065 
 
 4 
 
 4.60 
 
 4,026 
 
 12.648 
 
 14.137 
 
 0.949 
 
 0.849 
 
 12.730 
 
 15.904 
 
 11.31 
 
 10.66 
 
 45 
 
 5.00 
 
 4.508 
 
 14.153 
 
 15.708 
 
 0.848 
 
 0.765 
 
 15.939 
 
 19.636 
 
 9.03 
 
 12.34 
 
 5 
 
 6.563 
 
 5.045 
 
 15.849 
 
 17.476 
 
 0.75r 
 
 0.629 
 
 19.990 
 
 24.299 
 
 7.20 
 
 14.50 
 
 6 
 
 6.625 
 
 6.065 
 
 13.054 
 
 20.813 
 
 0.63 
 
 0.577 
 
 28.889 
 
 34.471 
 
 4.98 
 
 18.767 
 
 7 
 
 7.625 
 
 7.023 
 
 22.063 
 
 23.964 
 
 0.644 
 
 0.595 
 
 38.737 
 
 45.663 
 
 3.72 
 
 23.27 
 
 8 
 
 8.625 
 
 7.982 
 
 26.076 
 
 27.096 
 
 0.478 
 
 0.444 
 
 50.039 
 
 58.426 
 
 2.88 
 
 28.177 
 
 9 
 
 9.625 
 
 9.001 
 
 23.277 
 
 30.433 
 
 0.425 
 
 0.394 
 
 63.633 
 
 73.716 
 
 2.26 
 
 33.70 
 
 10 
 
 10.75 
 
 10.019 
 
 31.475 
 
 33.772 
 
 0.381 
 
 0.365 
 
 78.838 
 
 90.762 
 
 1.80 
 
 40.06 
 
 11 
 
 12.00 
 
 11,25 
 
 35.343 
 
 87.699 
 
 0.340 
 
 0.318 
 
 98.942 
 
 113.097 
 
 1.455 
 
 45.95 
 
 12 
 
 12.75 
 
 12.000 
 
 38.264 
 
 40.840 
 
 0.313 
 
 0.293 
 
 116.535 
 
 132.732 
 
 1.235 
 
 48.98 
 
 14 
 
 14,00 
 
 13.25 
 
 41.268 
 
 43.983 
 
 0.290 
 
 0.273 
 
 1.34.582 
 
 163.938 
 
 1.069 
 
 53.93 
 
 15 
 
 15.00 
 
 14.25 
 
 44.271 
 
 47.124 
 
 0.271 
 
 0.254 
 
 155.968 
 
 176.716 
 
 .923 
 
 57.89 
 
 16 
 
 16.00 
 
 15.25 
 
 47.274 
 
 50,265 
 
 0.254 
 
 0.238 
 
 177.867 
 
 201.063 
 
 .809 
 
 61.77 
 
 18 
 
 18.00 
 
 17.25 
 
 53.281 
 
 56.548 
 
 0.225 
 
 0.213 
 
 225. 9W 
 
 354.469 
 
 .638 
 
 69. C6 
 
 20 
 
 20.00 
 
 19.25 
 
 59.288 
 
 62.832 
 
 0.202 
 
 0.191 
 
 279.730 
 
 314.160 
 
 .615 
 
 77.57 
 
 * From catalogue of Walworth Manufacturing Company. 
 
 Fittings. — Cast-iron fittings, both screwed and flanged, are used, 
 for all classes of steam work. These are commonly made in three 
 weights. The lightest for low pressures, such as exhaust or con- 
 denser connections ; standard weight, for heating and all pressures 
 up to 100 or 125 pounds per square inch; and extra heavy for 
 higher pressures up to 250 pounds per square inch. 
 
PIPE, FITTINGS AND VALVES 
 
 63 
 
 Fittings are made in a great variety of forms, the most common 
 being the elbow, tee, cross, return bend and coupling, indicated 
 in Fig. 17, ^ to £ inclusive. The eccentric reducing coupling, 
 shown at F, is for use when connections are made in the side or 
 top of a long run of pipe, which reduces in size as the branches 
 are taken ofif. By the use of this fitting the bottom of the main 
 is kept level and pockets for the collection of water are avoided. 
 
 Various modifications of these fittings may be had to meet 
 almost any condition which may arise in designing a system of 
 piping. 
 
 ^ 
 
 ^ 
 
 Fig. 17. Pipe Fittings. 
 
 Elbows of 45 degrees are used for making an eighth turn, and 
 Y branches for making a 45-degree connection with a main. 
 
 When pipes are to be joined permanently, couplings are com- 
 monly used, but if it is desired to make any part of the work re- 
 movable, unions are employed instead. All steam and water con- 
 nections with boilers, engines, pumps, radiators and other appar- 
 atus should be made up with unions. For small pipes, the screwed 
 brass union shown in Fig. 18 is used, but for larger sizes, over 3 
 or i3% inches, cast-iron flanges are screwed to the ends of the 
 pipe and then bolted together as indicated in Fig. 19. 
 
64 
 
 HEATING AND VENTILATING PLANTS 
 
 Details of Construction. 
 
 Flanged Joints and Gaskets. — For low-pressure steam and hot 
 water, the flanges are simply screwed onto the ends of the pipe 
 with a taper thread, a thin gasket of sheet packing placed between 
 them, and then drawn together with bolts. For higher pressures 
 more care must be taken to make the joints tight and durable. 
 
 Hangers. — ^Hangers of various patterns are used for supporting 
 steam and return pipes in overhead positions. When the ceiling 
 construction is of wood they are usually held in place by lag 
 
 Fig. 18. Union. Fig. 19. Flange Joint. 
 
 screws, screwed into the beams or joists. When fireproof con- 
 struction is used, the hangers are either clamped to the lower 
 flanges of the /-beams or attached to iron plates embedded in the 
 masonry above the arches. The requirements of a satisfactory 
 hanger are that it shall be adjustable to the proper alignment of 
 the pipe and have sufficient lateral movement to swing with the 
 expansion and contraction of the pipe without straining. Hangers 
 are usually placed from 10 to 13 feet apart on straight runs of 
 pipe, with extra ones at bends or where other special conditions 
 require them. Fig. SO shows an adjustable hanger with lag screw 
 for attaching to a wooden ceiling, while Fig. 21 is provided with 
 a clamp for fastening to an /-beam. Where pipes run near the 
 floor they are usually supported on rolls which rest in small cast- 
 iron bases screwed or bolted to the floor. (iSee Fig. 22.) 
 
 Pipe Expansion. — As pipes expand about ly^ inches in each 
 100 feet when low pressure steam is turned into them, it is evi- 
 dent that in laying out a system of piping care must be taken to 
 provide for this increase in length without producing excessive 
 strains upon the pipe and fittings. In case of the smaller sizes 
 this may be cared for by means of offsets and bends which allow 
 
PIPE, FITTINGS AND VALVES 
 
 65 
 
 the pipe to spring or give. For the larger sizes, this simple method 
 will not be sufficient unless the offsets are of considerable length, 
 and swivels or slip joints must be used to take up the expansion. 
 
 Valves. 
 
 Among the requirements of a good valve, are, sufficient weight 
 of metal to prevent its being bent or sprung out of shape when 
 connected with the piping; valve seats that are easily repaired or 
 renewed, freedom from pockets or projections which may catch 
 
 G 
 
 yS 
 
 L/ 
 
 Nj 
 
 H] 
 
 Fig. 20. Fig. 21. Fig. 22 
 
 Pipe Hangers. Pipe Support. 
 
 dirt or scale, and arrangements for easily packing the stem or 
 spindle when under pressure. 
 
 Gate Valves. — This type of valve gives very little resistance to 
 the flow of steam or liquid passing through it, and is generally 
 used in the best class of work. 
 
 A form commonly employed in heating work is shown in Fig. 
 33. 
 
 A gate valve should never be placed in a steam pipe with the 
 spindle downward, for if only partially opened, the gate project- 
 ing from the bottom upward, will form a pocket for holding back 
 the condensation, and may thus be the cause of serious injury to 
 the plant. When placed with the stem extending upward or in a 
 horizontal position a clear passage is provided at the bottom of 
 the pipe. Valves are made in different weights and the pressure 
 to be carried should always be stated when they are specified. 
 
66 
 
 BEATING AND VENTILATING PLANTS 
 
 Globe Valves. — A form of globe valve is shown in Fig. 'Z^. 
 This is known as a disc valve, and has a renewable seat; other 
 patterns have solid seats of different forms. A globe valve 
 should always be set to close against the pressure, for if placed in 
 the opposite way it could not be opened if the valve should be- 
 come detached from the stem, and no indication of the trouble 
 would be given by the action of the stem under these conditions. 
 
 gix 
 
 A 
 
 I I 
 
 Fig. 23. Gate Valve. 
 
 Fig. 24. Globe Valve. 
 
 Fig. 25. Angle Valve. 
 
 Globe valves should never be placed in horizontal steam or dry 
 return pipes with the stem in a vertical position because under 
 this condition the condensation must rise to the middle of the 
 valve before it can flow through the port or opening. 
 
 Angle Valve. — These valves are sometimes used to take the 
 place of elbow fittings. They are a form of globe valve with the 
 inlet at the bottom and the outlet in the side. The larger sizes 
 have a guide spindle extending below the valve seat as shown in 
 Fig. 2i5, while in the smaller sizes this is omitted. 
 
 Radiator Valves. — These are usually of the disc type, shown in 
 Fig. 24, but are made in a variety of forms, as illustrated in Figs. 
 %&, 37 and 28, for use with radiators in various locations. The 
 first of these is the one most frequently used, and is adapted to 
 all cases where the radiator is placed at the top of a riser or the 
 connection is brought up through the floor. 
 
PIPE, FITTINGS AND VALVES 
 
 67 
 
 The second (Fig. 27), is employed where the run-out from 
 riser to radiator is above the floor, and it is desired to get a slight 
 drop at the valve to ensure proper drainage. The third (Fig. ^8), 
 is used where the radiator is set in a corner, and there is not 
 room for the usual fittings. It will be noticed that two of these 
 valves are provided with unions. This type is preferable because 
 
 Fig. 26. Fig. 27. Fig. 28. 
 
 Angle, Offset and Coiner Valves for Radiator Coniiections. 
 
 it allows of easy removal for repairs without disturbing the 
 other piping. Globe and gate valves are not commonly used in 
 making radiator connections but are usually employed for cir- 
 culation coils where the stems can be placed in the proper posi- 
 tion. In addition to the valves shown, there is a variety of special 
 designs upon the market, such as the "packless," "quick open- 
 ing," and "graduated" or "fractional" valve. 
 
 Hot-Water Valves. — While the valves above described are 
 often used on hot-water radiators it is more convenient to employ 
 some form of quick opening valve which requires only a quarter 
 or half turn for the complete operation of opening or closing. 
 Two designs of this type are shown in Figs. 2% and 30. 
 
 Ch^ck Valves. — When it is necessary that the flow of steam 
 or water shall always take place in the same direction, check 
 valves are employed. There are several forms of these in use, the 
 most common for heating work being the swing check shown in 
 Fig. 31. 
 
68 
 
 HEATING AND VENTILATING PLANTS 
 
 Fig. 29. 
 
 Fig. 30. 
 
 Two Designs of Hot-Water Valves. 
 
 If it is desired to reduce the resistance in special cases, the 
 valve may be turned partially on its side. The spring check, 
 shown in Fig. 3i3, is particularly adapted for use in feed-pipes 
 where the feed-water is supplied by a pump. The valve being 
 held in place by a light spring is prevented from beating against 
 the seat between the strokes of the piston. Check valves are 
 placed in boiler-feed and return pipes, in the discharge pipes from 
 traps, and various other places where it is desired to prevent the 
 
 Fig. 31. Check Valve. 
 
 Fig. 32. Spring Check. 
 
PIPE, FITTINGS AND VALVES 
 
 69 
 
 pressure in one pipe from "backing" into another, as when sev- 
 eral return pipes from a building are brought into a common 
 receiving tank. When used in a return pipe the check should 
 always be placed below the water line if possible. 
 
 .Valve 
 
 Fig. 33. Fig. 34. 
 
 Air Valves. — Air valves of various kinds are used for freeing 
 the radiators of air when steam is first turned on. They are usu- 
 ally automatic in action, being operated by an expansion piece 
 which closes the opening as soon as steam strikes it. When the 
 steam pressure drops, the expansion piece contracts and opens 
 the valve, allowing air to again fill the radiator. The expansion 
 piece varies in form and material in different makes, being some- 
 times of metal but more frequently of vulcanite. 
 
 Fig. 33 shows a common form of air valve. In this case the 
 expansion piece is made up of two strips of metal, usually steel 
 and brass, soldered together. The difference in expansion of the 
 two metals causes the prongs of the loop to open slightly when 
 steam strikes it and so raises the spindle and closes the valve. 
 The hollow float is for catching any sudden rush of water that 
 may occur, and being attached to the spindle, closes the valve 
 temporarily until the water drains back into the radiator. 
 
70 
 
 HEATING AND VENTILATING PLANTS 
 
 Fig. 34 shows a valve in which the metal expansion piece is 
 replaced by one of vulcanite. The outlet for the air is through 
 the center of the vulcanite plug, as indicated by the arrows. 
 
 The end of the plug rests against a spring seat which prevents 
 injury to the valve in case the seat is screwed down too far dur- 
 ing adjustment. In Fig. 35 the expansion piece consists of a 
 small metal float partially filled with a volatile liquid. This va- 
 porizes and exerts a certain pressure when the radiator is free 
 from air and steam begins to flow through the valve. The effect 
 of this is to bulge the ends of the float a small amount, thus 
 raising the spindle and closing the valve. 
 
 A sudden rush of water is met and cared for the same as in 
 Fig. 33. 
 
 Fig. 35. Fig. 36. 
 
 A form of valve often used on indirect radiators and coils, 
 where its appearance is not objectionable, is shown in Fig. 3i6. It 
 consists primarily of a brass tube which is screwed into the 
 radiator. The upper end of the tube has a small opening partly 
 closed by a pointed thumb screw which turns in a yoke supported 
 by iron side rods as shown. As long as the tube remains cold the 
 air can pass out freely through the opening at the end, but when 
 
PIPE, FITTINGS AND VALVES 
 
 71 
 
 Steam enters, the resulting expansion presses it firmly against the 
 point of the thumb screw, thus closing the opening. 
 
 In certain forms of vapor heating, "vacuum" air valves are 
 employed which allow the air to pass out under a slight steam 
 pressure but act as a check to prevent its return -when the pres- 
 sure within the system falls below that of the atmosphere. A 
 valve of this kind is shown in Fig. 37, in which the same general 
 type of expansion piece is employed as in Fig. 35. In this case, 
 
 Fig. 37. 
 Vacuum Air Valve. 
 
 Fig. 38. 
 Automatic Valve for Hot- Water Radiator. 
 
 however, the chamber containing the volatile liquid is in the form 
 of a bellows, which gives a greater movement to the valve stem 
 and reduces the liability of fracture from constant expansion and 
 contraction. Referring to the cut, A is the lower bellows or 
 "sylphon," charged with the volatile liquid, B the upper sylphon, 
 acted upon by the steam pressure only. The valve stem F is 
 attached to the lower sylphon. A, and moves with it, while the 
 tube E containing the valve seat is attached to the upper 
 sylphon, B. When steam is admitted to the radiator a pres- 
 sure of a few ounces is sufficient to raise B, thus opening the 
 valve and allowing the air to escape from the system. As soon 
 
72 
 
 HEATING AND VENTILATING PLANTS 
 
 as Steam strikes A the volatile liquid expands and by raising the 
 stem F closes the vent opening in E. When the steam pressure 
 drops and approaches that of the atmosphere, B falls and pre- 
 vents the entrance of air into the system, thus keeping the valve 
 closed and establishing a vacuum. 
 
 A common type of hot- water air valve is shown in Fig. 38. 
 The valve in this case being opened by a small float which falls 
 
 CONNECT WITH LOW PRESSURE SIDE 
 
 Fig. 39. Reducing Valve. 
 
 Fig. 40. Back-Pressure Valve. 
 
 when air collects in the top of the radiator and lowers the water 
 level. 
 
 Pressure Reducing Valves. — It is often necessary to provide 
 steam at different pressures in the same building, as in a com- 
 bined power and heating plant. In this case the reduction in 
 pressure is accomplished by passing the steam through a reduc- 
 ing valve. There are many different forms of these valves, all 
 acting more or less upon the same general principles. In the valve 
 shown in Fig. 39, the low pressure steam acts on the lower side 
 of a flexible diaphragm, and the weighted lever, which may be 
 adjusted to give the desired reduction in pressure, acts upon the 
 other side. The movement of this diaphragm causes a balanced 
 valve to open or close as may be necessary to maintain the desired 
 lower pressure. 
 
 Back Pressure Valve. — This is a form of relief valve which is 
 placed in the outboard exhaust pipe from an engine to prevent 
 
PIPE, FITTINGS AND VALVES 73 
 
 the pressure in the heating system from rising above a given point. 
 Its office is the reverse of the reducing valve which supplies more 
 steam when the pressure becomes too low. The form shown in 
 Fig. 40 is opened by the steam pressure acting upon an area equal 
 to the difference in areas of the two discs. Regulation for dif- 
 ferent pressures is obtained by varying the position of the weight 
 upon the lever arm. 
 
CHAPTER VII. 
 DIRECT STEAM HEATING. 
 
 Although a system of direct steam heating is more expensive 
 to install than a hot-air furnace, it has a number of advantages, 
 especially in buildings of large size. The most important of 
 these is the ability to reach and heat any room regardless of its 
 location and distance from the boiler. This makes it possible to 
 warm the entire building from a single boiler, or battery of boil- 
 ers, thus adding both to the convenience and economy of opera- 
 tion. With furnace heating in buildings of large size, it is neces- 
 sary to duplicate the units because the distance which warm air 
 can be carried horizontally is limited in the ordinary gravity sys- 
 tem. 
 
 The operating expenses with direct steam are less than with 
 hot-air because no special ventilation is provided. 
 
 While the inability to provide fresh air with this system is 
 often considered a disadvantage, there are many times when 
 ventilation is unnecessary and simply a useless expense. In the 
 case of entrance vestibules and halls, and in rooms occupied by 
 a single person there is usually sufficient air provided by leakage. 
 In sleeping rooms also, the modern practice of free ventilation 
 through open windows during the night makes the furnishing of 
 warm air unnecessary except in special cases. 
 
 When compared with hot-water heating, steam has the ad- 
 vantage of smaller radiators; practically no danger of freezing 
 when ordinary precautions are taken; and greater flexibility as 
 regards warming up or cooling ofif a building quickly. 
 
 Among the disadvantages of direct steam are the lack of ven- 
 tilation; the unsightliness of radiators and piping in the rooms 
 and the difficulty of cleaning the spaces around them ; flooding of 
 floors from open air valves ; noise from water hammer and surg- 
 ing in pipes ; and difficulty in regulating the amount of heat sup- 
 plied to the rooms. The last is an especially important matter 
 because the radiators are proportioned for the coldest weather 
 
 74 
 
DIRECT STEAM HEATING 75 
 
 and must work at their full capacity when filled with steam re- 
 gardless of the outside temperature. All of these objections may 
 be avoided to a certain extent, however, when the system is 
 properly designed and operated. While a supply of fresh warm 
 air cannot be provided by a system of direct heating, either with 
 steam or hot-water, it is a comparatively simple matter to add 
 indirect stacks, thus obtaining the advantages of furnace heating 
 in one or more of the important rooms, such as living room, 
 nursery, library, etc., if so desired. Sometimes a generous quan- 
 tity of fresh air is supplied to the hall in this manner, which finds 
 its way to other rooms through open doors. Direct radiators can 
 usually be so placed as not to be especially conspicuous, and 
 much may be done to improve their appearance by making them 
 of pleasing proportions and by giving them a finish to correspond 
 with that of the room in which they are located. 
 
 Supply and return piping can usually be concealed in partitions, 
 carried up in closets, or in the corners of unimportant. rooms if a 
 certain amount of care is exercised in planning the work. Much 
 of the difficulty formerly experienced by the accumulation of dirt 
 is now obviated by the use of wall radiators and those of plain 
 and open pattern. 
 
 With supply and return pipes of sufficient size, properly drained 
 and graded, there should be no difficulty either from leaking air 
 valves or water hammer. The best makes of automatic air valves 
 are now constructed in such a manner as to overcome dripping 
 or "spitting," and with a properly connected radiator there should 
 be no danger of flooding unless the return valve is left open with 
 the steam valve closed. By using the "single-pipe" method of 
 supply, which is usually possible in most cases, this danger may 
 also be done away with. 
 
 While the only method of obtaining a close regulation of tem- 
 perature is by the use of an expensive system of automatic con- 
 trol, there are various way in which direct steam may be made 
 fairly flexible and to compare favorably with hot air or water. 
 
 One of the simplest methods is to divide the radiator into two 
 parts, in the ratio of 1 to 2, by means of a "blind nipple" between 
 the sections, and connect each end with a single-pipe supply. 
 
76 
 
 HEATING AND VENTILATING PI ANTS 
 
 This gives, in effect, two separate radiators, and makes it pos- 
 sible to employ 1/3, %/Z or 3/3 the total capacity as may be re- 
 quired. Other methods include "vapor systems" where the pres- 
 sure, and consequently the temperature within the radiator may 
 be varied somewhat; also "vacuum systems," where a consider- 
 able difference in pressure is maintained between the supply and 
 return piping and the quantity of steam admitted to the radiator- 
 is regulated by a graduated valve. 
 
 Fig. 41. Common Form of Radiator. 
 
 Direct steam, in one form or another, is adapted to almost all' 
 classes of buildings, either by itself or in combination with in- 
 direct-heating, and is probably more widely used than any other 
 system. 
 
DIRECT STEAM HEATING 77 
 
 Types of Radiating Surface. 
 
 The radiation used in direct steam heating is made up of cast- 
 iron sections of various forms, a combination of cast-iron cham- 
 bers and wrought-iron pipes, and circulation coils, so called. 
 
 Cast-Iron Radiators. — For dwelling houses, apartments, office 
 buildings, etc., cast-iron sectional radiators of the general type 
 shown in Fig. 41 are commonly employed. These are made in a 
 great variety of forms and can be ftirnished in almost any shape 
 or proportion desired. 
 
 The sections are joined at the bottom by special nipples which 
 form a steam or supply chamber and circulation is produced by 
 slight differences in pressure in the legs or loops of which the 
 sections are made up. 
 
 The designs of different makers vary somewhat in size for the 
 same amount of heating surface, but Tables XXI. to XXIV., from 
 the catalogue of the American Radiator Company, may be taken 
 as giving about the average space required for radiators of dif- 
 ferent size. More sections may be added if desired, but for pur- 
 poses of temperature regulation it is better to use two or more 
 smaller radiators in place of a single large one. A low and mod- 
 erately shallow radiator with ample space for the circulation of 
 air between the sections is more eiificient than a deep radiator 
 with the sections closely packed together. One and two column 
 radiators, so called, are preferable to three and four column, 
 when there is sufficient space to use them. 
 
 The standard height of a radiator is 3,8 inches, and it is better 
 not to exceed this if possible. For small radiators it is the better 
 practice to use lower sections and increase the length ; this makes 
 the radiator slightly more efficiient and gives a much better 
 appearance. 
 
 Wall Radiators. — These are now used quite extensively where 
 it is desired to keep the floor free and to take up as little space as 
 possible. The regular sizes project only about 4 inches from the 
 wall when erected, and are usually attached to cleats screwed to 
 the studding, or supported upon special legs when the walls are 
 of stone or other fireproof construction. Patterns having cross- 
 bars should be placed, if possible, with the bars in a vertical 
 position, as their efficiency is impaired somewhat when placed 
 
78 
 
 HEATING AND VENTILATING PLANTS 
 
 Table XXI. 
 
 Sizes of Radiators for Various Heights and Areas of Heating Sur- 
 face. Single Column. 
 
 
 I/ength 
 
 Heating surface— square feet 
 
 
 
 
 
 
 
 S o 
 
 85 inches 
 
 Height, 
 
 Height, 
 
 Height, 
 
 Height, 
 
 Height, 
 
 
 per 
 
 83 in. 
 
 32 in. 
 
 26 m. 
 
 23 m. 
 
 80 in. 
 
 section 
 
 3 sq. ft. 
 
 25 sq. ft. 
 
 2 sq. ft. 
 
 11 sq. ft. 
 
 15 sq. ft. 
 
 ^ 
 
 
 per sec. 
 
 per sec. 
 
 per sec. 
 
 per sec. 
 
 per sec. 
 
 i 
 
 B 
 
 6 
 
 . 5 
 
 4 
 
 35 
 
 3 
 
 3 
 
 1i 
 
 9 
 
 171 
 
 6 
 
 5 
 
 45 
 
 4 
 
 10 
 
 12 
 
 10 
 
 8 
 
 6§ 
 
 6 
 
 6 
 
 m 
 
 15 
 
 125 
 
 10 
 
 85 
 
 75 
 
 6 
 
 15 
 
 18 
 
 15 
 
 12 
 
 10 
 
 9 
 
 7 
 
 m. 
 
 81 
 
 175 
 
 14 
 
 11§ 
 
 105 
 
 8 
 
 80 
 
 24 
 
 80 
 
 16 
 
 133 
 
 12 
 
 9 
 
 32i 
 
 27 
 
 225 
 
 18 
 
 15 
 
 135 
 
 10 
 
 85 
 
 30 
 
 85 
 
 80 
 
 16? 
 
 15 
 
 11 
 
 2;'d 
 
 33 
 
 275 
 
 82 
 
 185 
 
 165 
 
 12 
 
 30 
 
 36 
 
 30 
 
 84 
 
 80 
 
 18 
 
 13 
 
 32J 
 
 39 
 
 325 
 
 26 
 
 213 
 
 195 
 
 14 
 
 35 
 
 42 
 
 35 
 
 28 
 
 235 
 
 21 
 
 15 
 
 37J 
 
 45 
 
 375 
 
 30 
 
 25 
 
 285 
 
 16 
 
 40 
 
 48- 
 
 40 
 
 32 
 
 2&i 
 
 84 
 
 17 
 
 425 
 
 51 
 
 425 
 
 34 
 
 885 
 
 255 
 
 18 
 
 45 
 
 54 
 
 45 
 
 36 
 
 30 
 
 87 
 
 19 
 
 475 
 
 57 
 
 475 
 
 38 
 
 31| 
 
 285 
 
 30 
 
 50 
 
 60 
 
 50 
 
 40 
 
 33J 
 
 30 
 
 21 
 
 525 
 
 63 
 
 525 
 
 42 
 
 35 
 
 31J 
 
 22 
 
 55 
 
 66 
 
 55 
 
 44 
 
 361 
 
 33 
 
 23 
 
 575 
 
 69 
 
 •575 
 
 46 
 
 385 
 
 . 345 
 
 24 
 
 60 
 
 72 
 
 60 
 
 48 
 
 40 
 
 36 
 
 Table XXII. 
 Double Column. 
 
 
 Length 
 
 
 
 Heating surface— square feet 
 
 
 
 
 
 
 
 
 
 
 
 Si 
 
 25 inches 
 
 Height, 
 
 Height, 
 
 Height, 
 
 Height, 
 
 Height, 
 
 Heigrht, 
 
 Height, 
 
 1" 
 
 per 
 
 45 m. 
 
 38 in.. 
 
 33 in. 
 
 26 m. 
 
 23 m. 
 
 80 m. 
 
 15 m. 
 
 section 
 
 5 sq. ft. 
 
 4 sq. ft. 
 
 3J sq. ft. 
 
 23 sq. ft. 
 
 25 sq. ft. 
 
 2 sq. ft. 
 
 15 sq. ft. 
 
 'z, 
 
 
 per sec. 
 
 per sec. 
 
 per sec. 
 
 per sec. 
 
 per sec. 
 
 per sec. 
 
 per sec. 
 
 8 
 
 5 
 
 10 
 
 8 
 
 6§ 
 
 55 
 
 43 
 
 4 
 
 3 
 
 3 
 
 75 
 
 15 
 
 18 
 
 10 
 
 8 
 
 7 
 
 6 
 
 45 
 
 4 
 
 10 
 
 20 
 
 16 
 
 III 
 
 10§ 
 
 95 
 
 8 
 
 6 
 
 5 
 
 125 
 
 25 
 
 20, 
 
 185 
 
 II3 
 
 10 
 
 75 
 
 6 
 
 IB 
 
 30 
 
 84 
 
 80 
 
 16 
 
 14 
 
 18 
 
 9 
 
 7 
 
 175 
 
 35 
 
 28 
 
 235 
 
 181 
 
 165 
 
 14 
 
 105 
 
 8 
 
 20 
 
 40 
 
 38 
 
 261 
 
 215 
 
 183 
 
 16 
 
 12 
 
 9 
 
 285 
 
 45 
 
 36 
 
 30 
 
 24 
 
 81 
 
 18 
 
 18S 
 
 10 
 
 35 
 
 50 
 
 40 
 
 335 
 361 
 
 263 
 
 83.', 
 
 80 
 
 15 
 
 11 
 
 875 
 
 55 
 
 44 
 
 295 
 
 253 
 
 28 
 
 165 
 
 12 
 
 30 
 
 60 
 
 48 
 
 40 
 
 32 
 
 88 
 
 84 
 
 18 
 
 13 
 
 325 
 
 65 
 
 58 
 
 434 
 461 
 
 343 
 
 i^l 
 
 26 
 
 195 
 
 14 
 
 35 
 
 70 
 
 66 
 
 375 
 
 38 
 
 21 
 
 15 
 
 375 
 
 75 
 
 60 
 
 50 
 
 40 
 
 85 
 
 80 
 
 285 
 
 16 
 
 40 
 
 80 
 
 64 
 
 56i 
 
 48} 
 
 375 
 391 
 
 38 
 
 24 
 
 17 
 
 425 
 
 85 
 
 68 
 
 455 
 
 34 
 
 255 
 
 18 
 
 45 
 
 90 
 
 72 
 
 60 
 
 48 
 
 42 
 
 36 
 
 27 
 
 19 
 
 475 
 
 95 
 
 76 
 
 ^\ 
 
 503 
 
 445 
 
 38 
 
 285 
 
 20 
 
 50 
 
 100 
 
 80 
 
 535 
 
 463 
 
 40 
 
 30 
 
 21 
 
 525 
 
 105 
 
 84 
 
 70 
 
 56 
 
 49 
 
 42 
 
 815 
 
 28 
 
 55 
 
 110 
 
 88 
 
 1% 
 
 583 
 
 515 
 533 
 
 44 
 
 33 
 
 33 
 
 575 
 
 IIB 
 
 92 
 
 615 
 
 46 
 
 345 
 
 81 
 
 60 
 
 180 
 
 96 
 
 80 
 
 64 
 
 56 
 
 48 
 
 36 
 
DIRECT STEAM HEATING 
 
 79 
 
 Table XXIII. 
 
 Sizes of Radiators for Various Heights and Areas of Heating Sur- 
 face. Three Column. 
 
 4-1 
 
 
 
 Heating surface — square 
 
 feet 
 
 
 u a 
 
 
 
 
 
 
 
 
 S.2 
 
 2J inches 
 
 Height, 
 
 Height, 
 
 Height, 
 
 Height, 
 
 Height, 
 
 Height, 
 
 1" 
 
 per 
 
 44 m. 
 
 38 m. 
 
 32 in. 
 
 26 in. 
 
 
 
 section 
 
 6 sq. ft. 
 
 5 sq. ft. 
 
 4.i sq. ft. 
 
 33 sq. ft. 
 
 3 sq. ft. 
 
 2J sq. ft. 
 
 z 
 
 
 per sec. 
 
 per sec. 
 
 per sec. 
 
 per sec. 
 
 per sec. 
 
 per sec. 
 
 2 
 
 6 
 
 12 
 
 10 
 
 9 
 
 74 
 
 6 
 
 44 
 
 B 
 
 n 
 
 18 
 
 15 
 
 13J 
 
 llj 
 
 9 
 
 6} 
 
 4 
 
 10 
 
 24 
 
 20. 
 
 18 
 
 15 
 
 12 
 
 9 
 
 5 
 
 121 
 
 30 
 
 25 
 
 22J 
 
 182 
 
 15 
 
 Hi 
 
 6 
 
 15 
 
 36 
 
 30 
 
 87 
 
 224 
 
 18 
 
 184 
 
 7 
 
 174 
 
 42 
 
 35 
 
 3U 
 
 26i 
 
 21 
 
 15| 
 
 8 
 
 20 
 
 48 
 
 40 
 
 36 
 
 30 
 
 24 
 
 18 
 
 9 
 
 22i 
 
 64 
 
 45 
 
 m 
 
 33 
 
 27 
 
 20j 
 
 10 
 
 26 
 
 60 
 
 50 
 
 45 
 
 374 
 
 30 
 
 22, 
 
 11 
 
 m 
 
 66 
 
 55 
 
 49J 
 
 41i 
 
 33 
 
 24 
 
 12 
 
 30 
 
 72 
 
 60 
 
 54 
 
 45 
 
 36 
 
 27 
 
 13 
 
 325 
 
 78 
 
 65 
 
 584 
 
 48, 
 
 39 
 
 29i 
 
 14 
 
 85 
 
 84 
 
 70 
 
 63 
 
 52 
 
 42 
 
 .311 
 
 15 
 
 37J 
 
 90 
 
 76 
 
 674 
 
 56 
 
 45 
 
 383 
 
 16 
 
 40 
 
 96 
 
 80 
 
 72 
 
 60 
 
 48 
 
 •36 
 
 17 
 
 42J ' 
 
 102 
 
 85 
 
 764 
 
 631 
 
 51 
 
 88J 
 
 18 
 
 45 
 
 108 
 
 90 
 
 81 
 
 674 
 
 64 
 
 40* 
 
 19 
 
 47i 
 
 114 
 
 96 
 
 854 
 
 71i 
 
 67 
 
 423 
 
 20 
 
 50 
 
 120 
 
 100 
 
 90 
 
 75 
 
 60 
 
 45 
 
 21 
 
 625 
 
 126 
 
 105 
 
 944 
 
 82f 
 
 63 
 
 47. 
 
 22 
 
 65 
 
 132 
 
 110 
 
 99 
 
 66 
 
 49 
 
 28 
 
 57J 
 
 138 
 
 115 
 
 103J 
 
 86i 
 
 69 
 
 61 
 
 24 
 
 60 
 
 144 
 
 120 
 
 108 
 
 90 
 
 72 
 
 54 
 
 Table XXIV. 
 Four Column. 
 
 °2 
 
 Length 
 
 Heating surface — square feet 
 
 
 
 
 
 
 
 ^■^ 
 
 23 inches 
 
 Height, 
 
 Height, 
 
 Height, 
 
 Height, 
 
 Height, 
 
 1" 
 
 per 
 
 
 
 
 23 in. 
 
 20 m. 
 
 section 
 
 8 sq. ft. 
 
 65 sq. ft. 
 
 64 sq.ft. 
 
 4| sq. ft. 
 
 4 sq. ft. 
 
 ^; 
 
 
 per sec. 
 
 per sec. 
 
 per sec. 
 
 per sec. 
 
 per sec. 
 
 2 
 
 54 
 
 16 
 
 134 
 
 103 
 
 94 
 
 8 
 
 8 
 
 8i 
 
 24 
 
 20 
 
 16 
 
 14 
 
 12 
 
 4 
 
 11 
 
 33 
 
 26} 
 
 214 
 281 
 
 185 
 
 16 
 
 6 
 
 133 
 
 40 
 
 334 
 
 234 
 
 20 
 
 6 
 
 164 
 
 48 
 
 40 
 
 32 
 
 28 
 
 24 
 
 7 
 
 191 
 
 56 
 
 465 
 
 375 
 
 325 
 
 28 
 
 8 
 
 22 
 
 64 
 
 584 
 
 42j 
 
 374 
 
 82 
 
 9 
 
 243 
 
 . 12 
 
 60 
 
 48 
 
 42 
 
 36 
 
 10 
 
 274 
 
 SO 
 
 661 
 
 53.5 
 
 465 
 
 40 
 
 11 
 
 30i 
 
 88 
 
 734 
 
 585 
 
 614 
 
 44 
 
 12 
 
 33 . 
 
 96 
 
 80 
 
 64 
 
 66 
 
 48 
 
 13 
 
 363 
 
 104 
 
 865 
 
 695 
 745 
 
 605 
 
 52 
 
 14 
 
 88J 
 
 112 
 
 984 
 
 655 
 
 68 
 
 15 
 
 414 
 
 120 
 
 100 
 
 80 
 
 70 
 
 60 
 
 16 
 
 44 
 
 128 
 
 1065 
 
 
 745 
 
 64 
 
 17 
 
 46, 
 
 136 
 
 113i 
 
 905 
 
 794 
 
 68 
 
 18 
 
 49 
 
 144 
 
 120 
 
 96 
 
 84 
 
 72 
 
 19 
 
 52 
 
 152 
 
 1281 
 
 1014 
 1065 
 
 885 
 
 76 
 
 20 
 
 55 
 
 160 
 
 1334 
 
 985 
 
 80 
 
 21 
 
 57, 
 
 168 
 
 140 
 
 112 
 
 98 
 
 84 
 
 22 
 
 60 
 
 176 
 
 1461 
 
 1175 
 
 102# 
 
 88 
 
 23 
 
 63, 
 
 184 
 
 1534 
 
 1225 
 
 1074 
 
 92 
 
 24 
 
 66 
 
 192 
 
 160 
 
 128 
 
 112 
 
 96 
 
80 
 
 HEATING AND VENTILATING PLANTS 
 
 horizontally. To get the best results they should be set out at 
 least 1% inches from the wall to allow a free circulation of air 
 back of them. Fig. 42 shows the Fowler and Wolfe wall radia- 
 tor, and Table XXV. gives the standard dimensions. 
 
 The sections may be tapped at any of the points indicated by 
 the arrows, and made up in groups of any form or size desired. 
 
 Fig. 42. Fowler & Wolfe Wall Radiator. 
 
 Table XXV. 
 Heating Surface and Linear Dimensions of Wall Radiators. 
 
 Square feet of 
 
 Length of section, 
 
 Width of section, 
 
 Thickness of 
 
 surface 
 
 inches 
 
 inches 
 
 section, inches 
 
 5 
 
 17 
 
 185 
 
 3 
 
 6 
 
 21 
 
 m 
 
 3 
 
 7 
 
 84 
 
 12S 
 
 3 
 
 9 
 
 34 
 
 13 
 
 3J 
 
 Fig. 43 shows another form of wall radiator made by the 
 American Radiator Company. This is similar to the ordinary 
 single column floor radiator except the legs are omitted and it is 
 supported by brackets attached to the wall. This pattern is made 
 in heights of 20, 23, 26, 32 and 38 inches. The heating surface 
 per section may be taken from Table XXI. Projection from wall 
 5% inches. 
 
DIRECT STEAM HEATING 
 
 81 
 
 Pipe Radiators. — Another and older form of radiator is shown 
 in Fig. 44. This consists of wrought-iron pipes screwed into a 
 cast-iron base. The pipes are sometimes connected at the top in 
 pairs, but usually they have no connection, each being closed and 
 provided with a thin metal diaphragm passing up the center 
 nearly to the top. This gives the effect of a loop and insures a 
 positive circulation of steam through it. 
 
 Fig. 43. Wall Radiator, American Radiator Company. 
 
 These radiators are usually made of 1-inch pipes, 36 inches in 
 height, each containing practically one square foot of heating 
 surface. 
 
 They are commonly made one, two, three and four pipes in 
 depth, and the corresponding bases are 4^/^, Si^, 81^, and 10 
 inches in width. In length, each pipe takes up about 2 inches and 
 the base projects 1 inch at each end. From these data the re- 
 
82 
 
 HEATING AND VENTILATING PLANTS 
 
 quired space for any amount of heating surface can be easily 
 approximated. 
 
 Wall Coils. — Circulation coils of wrought-iron pipe are used to 
 a large extent where the appearance is not of great importance, 
 as in shops, factories, basement rooms, etc. They are also em- 
 ployed where an extended heating surface is desired, as under the 
 windows in schoolrooms and in corridors. They should incline 
 
 Fig. 44. Pipe Radiator. 
 
 about 1 inch in each 20 or 30 feet toward the return end, in or- 
 der to secure proper drainage and quietness of operation. 
 
 If the pipes of a wall coil can be carried around the corner of 
 a room, branch tees of the form shown in Fig. 45 may be used at 
 the ends, the change in direction allowing sufficient spring to take 
 up the expansion in the pipes, provided the shorter side of the 
 coil is not less than about 1/6 the entire length. If the entire heat- 
 ing surface must be placed upon a single wall, a return bend coil, 
 of the form shown in Fig. 46 must be used. 
 
 In making up coils of this kind provision must be made to 
 allow for the unequal expansion of the pipes when steam is first 
 turned on. 
 
DIRECT STEAM HEATING 83 
 
 Overhead Coils are usually of the mitre form shown in Fig. 47 ; 
 they are laid on the side and suspended 13^ or 18 inches from the 
 ceiling. Coils placed in this position are more efficient than when 
 hung upon a wall, but are less effective than when placed near 
 
 Fig. 45. Tees for Pipe Ends of Coils. 
 
 the floor, as the warm air stays at the ceiling and the lower part 
 of the room is likely to remain cold. They are only used when 
 wall coils or nadiators would be in the way of fixtures, or when 
 they would come below the water-line of the boiler if placed at a 
 lower level. When coils are made in the form shown in Fig. 47 
 the ends of the pipes are screwed into branch tees, the same as 
 wall coils. 
 
 Overhead coils are supported upon special rolls and hangers 
 similar to those illustrated in Fig. 48, and wall coils upon hook 
 plates attached to the wall. 
 
 These are of two kinds as indicated in Figs. 49 and 50, one for 
 use with a cleat and the other for attaching directly to the wall. 
 
84 HEATING AND VENTILATING PLANTS 
 
 Efficiency of Radiators. 
 
 Determining Factors. — The efficiency of a radiator, that is, the 
 B. T. U. which it gives off per square foot of surface per hour, 
 depends upon the difference in temperature between the steam 
 
 Fig. 47. Overhead Circulation Coils. 
 
 Fig. 48. Hangeis for Overhead Coils. 
 
 in the radiator and the surrounding air, the velocity of the air 
 over the radiator, and the character of the surface, whether 
 rough or smooth. In the case of ordinary direct-steam heating 
 these conditions are very nearly constant and experience has 
 shown the average cast-iron radiator of open pattern to have an 
 efficiency of about MO B. T. U. per square foot of surface per 
 
DIRECT STEAM HEATING 
 
 85 
 
 hour. This is based on the assumption that 1.7 B. T. U. will be 
 given off per square foot per hour for each degree difference in 
 temperature between the radiator and surrounding air, and also 
 assumes a room temperature of 70° and a steam pressure of 3 
 pounds per square inch. With these data at hand, it is a simple 
 matter to compute the efficiency for other room temperatures and 
 for higher steam pressures. For example, the difference in tem- 
 
 
 
 ( 
 
 Fig. 49. Fig. 50. 
 
 Bookplates for Support of Wall Coils. 
 
 perature between 70° and steam at 2 pounds pressure is 2'30 — 
 70 = ,150°, and the radiator efficiency for this condition is 1.7 X 
 1,50 = 2'55 B. T. U., or .250 in round numbers. For a room tem- 
 perature of 50° and a steam pressure of 30 pounds, the efficiency 
 would become (,274—50) X 1.7 = 380 B. T. U. 
 
 The velocity of the air passing over the radiating surface af- 
 fects the efficiency to a certain extent and for this reason shallow 
 radiators, or those of especially open pattern, are more efficient. 
 
 Casing in a direct radiator or covering it with screens, as is 
 frequently done in banking rooms and private offices, lowers the 
 efficiency and should be offset by increasing the amount of sur- 
 face unless the casing is so designed as to provide for a free cir- 
 culation of air over the radiator from the bottom upward. 
 
86 HEATING AND VENTILATING PLANTS 
 
 While overhead of ceiling coils have a higher eificiency than 
 sectional radiators, due to the freedom with which the air passes 
 over them, they are less effective than radiating surface placed 
 near the floor. For this reason they must be given a low eflS- 
 ciency as compared with the usual floor radiator or wall coil. 
 The surface or finish of a radiator also affects its efficiency to a 
 certain extent ; a dull finish being about 30 per cent more effective 
 than a glossy one. 
 
 Table XXVI. gives average efficiencies for direct radiating sur- 
 face of different kinds for low pressure steam. 
 
 In practice it is not customary to make any difference in the 
 radiator efficiency for room temperatures 10° above or below the 
 
 Table XXVI. 
 Relattve Efficiencies of Various Types of Radiators 
 
 Type of radiating surface Efficiency 
 
 Cast iron, sectional, and pipe radiators .... 250 B. T. U. 
 
 Wall radiators 290 
 
 CeiUng coils 200 
 
 WaU coils 290 ;; 
 
 Cased-in radiators 150 to 170 
 
 normal, nor for a change in steam pressure unless.it amounts to 
 10 or 15 pounds. 
 
 Size and Location of Radiator. 
 
 To Compute Size of Radiator. — To compute the amount of 
 direct radiation for a given room, first determine the total heat 
 loss in B. T. U. per hour for the coldest weather (see Chapter 
 II.), and divide this by the efficiency of the radiator to be used. 
 The result will be the square feet of surface required. 
 
 Example. — 'The total heat loss from a room by transmission 
 and leakage is estimated at 12,500 B. T. U. per hour ; how many 
 square feet of cast-iron radiation will be required? 
 
 12,500-=-3.50 = 50 sq. ft. 
 
 When wrought-iron pipe coils are employed, square feet of sur- 
 face may be reduced to linear feet of pipe by use of the following 
 factors : 
 
DIRECT STEAM HEATING 87 
 
 Square feet of heating surface X ' 
 
 3 = linear ft. of l'' pipe 
 2.3= " " IX'/ " 
 
 2 = " " 1}4" " 
 
 1.6= " " 2" " 
 
 Example. — The total heat loss from a factory building is 
 
 5S0,000 B. T. U. per hour; how many linear feet of 1%-inch 
 
 pipe will be required in the wall coils? 
 
 580,000 ^o ^ nnn ,• c ^ 
 
 — ~- — X2 =4,000 hnear feet. 
 
 When computing the radiation for a building it is not usually 
 necessary to make any allowance for the additional heat required 
 in "warming up," this being cared for partly by the increased 
 efficiency of the radiators at room temperatures below 70°, and 
 partly by the surplus heating surface for all outside temperatures 
 above the minimum assumed. 
 
 Location. — Radiators should in general, be placed in the cold- 
 est part of the room, as under windows or near outside doors. In 
 living rooms it is often desirable to keep the windows free, in 
 which case the radiators may be placed at one side. Circulation 
 coils are usually run along the outside walls of a room under the 
 windows. Sometimes the positions of the radiators are deter- 
 mined by the necessary locations of the pipe risers, so that a 
 certain amount of judgment must be used in each special case as 
 to the best arrangement to suit all requirements. When the rooms 
 are small the location of the heat supply makes but little differ- 
 ence, and radiators or coils are usually placed where most con- 
 venient. 
 
 Systems of Piping. 
 
 There are three systems of piping commonly used for direct 
 steam, known as the two-pipe system, the one-pipe relief system, 
 and the one-pipe circuit system, with various modifications and 
 combinations. 
 
 Two-Pipe System. — Fig. 51 shows in diagram the arrange- 
 ment of piping and radiators in the two-pipe system. The steam 
 main leads from the top of the boiler and the branches are car- 
 ried along near the basement ceiling; risers are taken off from 
 
88 
 
 HEATING AND VENTILATING PLANTS 
 
 the supply branches and carried up to the radiators on the dif- 
 ferent floors, and return pipes are brought down to the return 
 mains, which should be placed, if possible, near the basement floor 
 below the water-line of the boiler. Where the building is more 
 than one story high, radiators in similar positions on different 
 floors are connected with the same supply riser, which may run 
 to the highest floor. A corresponding return drop connecting 
 
 ■^ ,,^.'i.'....'..'..f,. 
 
 /J f/f^/y^^fj'///^\ rZ/yf^i^/z/y^/^y ^ 
 
 5* 
 
 
 DRY RETURN 
 
 SIPHON LOOP 
 
 At 
 
 
 a 
 
 '^^/^/ ^^^^^^ I 
 
 SEALED RETURN 
 
 Fig. 51 . Piping and Radiators in Two-pipe System. 
 
 with each radiator is carried down beside the riser to the base- 
 ment. A system in which the main horizontal returns are below 
 the water-line of the boiler is said to have a "wet" or "sealed" 
 return. If the returns are overhead and above the water-line, it 
 is called a "dry" return. 
 
 Advantage of Wet Return. — A system having a wet return is, 
 in general, more free from surging or "water-hammer" than one 
 having a dry return. This arrangement prevents the steam from 
 coming in contact with the cooler water of condensation flowing 
 along the bottom of the return pipes, thus avoiding the sudden 
 condensation which is the principal cause of water-hammer. 
 When the return from each radiator is sealed against the entrance 
 of steam, there is no chance for air to become caught or pocketed 
 
DIRECT STEAM BEATING 
 
 89 
 
 in the middle sections of the radiator. This often happens with 
 a dry return, when the return valve is opened before the radiator 
 is entirely filled with steam. When it is necessary to use dry 
 returns on account of the pipes crossing doorways, etc., they 
 should be made of large size and given a pitch of at least 1 
 inch in 10 feet toward the boiler. The returns at the right in 
 Fig. 51 are sealed, while those at the left are dry. 
 
 Fig. 52. 
 
 Fig. 53. 
 
 Drip Pipes for Two-pipe System. 
 
 Arrangement of Drips. — The ends of all steam mains and 
 branches should be dripped into the returns, and all pockets for 
 the accumulation of condensation should be avoided. With long 
 mains it often happens that if given a continuous pitch they would 
 be too low at the extreme ends ; and it is therefore customary to 
 rise and drip at intervals, as shown in Figs. 52 and 53. This 
 applies to any of the systems of piping described. I^ the returns 
 are sealed, the drip may be directly connected, as shown in Fig. 
 20, but if they are dry, the drainage should be through a siphon 
 loop 4 or 5 feet in length, as in Fig. 53. The loop becomes filled 
 with water before overflowing into the return, thus preventing 
 the entrance of steam directly from the main, which being at a 
 slightly higher pressure is liable to result in water-hammer. In 
 the case of sealed returns, a grade of 1 inch in each 30 or 40 
 feet toward the boiler is sufficient. 
 
90 
 
 HEATING AND VENTILATING PLANTS 
 
 One-Pipe Relief System. — 'This is a very satisfactory arrange- 
 ment, especially for dwelling houses and similar work because 
 there is no danger of flooding the floors through carelessness in 
 closing the return valve. The radiators in this case have but a 
 single connection, as shown in Fig. 54, the same pipe serving for 
 both supply and return. 
 
 The general arrangement of the basement steam piping is sim- 
 ilar to that shown in Fig. 51, except for the method of drainage. 
 
 ■^yyy,y^^^yy^,,^,^y,y^y 
 
 
 DRY RETURN 
 
 -Ail. 
 
 SEALED RETURN 
 
 Fig. 54. Arrangement of Pipes in the One-pipe Relief System. 
 
 The highest point in the main should be directly above the boiler 
 and the various branches should pitch downward with an even 
 grade in the direction of steam flow. The risers are taken off 
 as indicated, and the bottoms dripped into the return main below. 
 Each riser supplying two or more radiators should, in general, 
 have a separate drip into the return. Single radiators of small 
 size may drip back into the supply main, but if they are of large 
 size it is better to drip each riser separately. 
 
 It will be noticed that the drip connections at the left, for the 
 dry return, are the reverse of those for the two-pipe system, that 
 is, the risers are drained through siphons while the end of the 
 main connects directly with the return. In this case the lowest 
 
DIRECT STEAM HEATING 91 
 
 pressure is at the ends of the mains so that steam introduced into 
 the returns at these points will cause no trouble in the pipes 
 connecting between them and the boiler. 
 
 If no steam is allowed to enter the returns, a vacuum will be 
 formed, and there will be no pressure to force the water back to 
 the boiler. 
 
 There is but little difference in the cost of the two systems, as 
 larger pipes and valves are required for the single-pipe method. 
 With radiators of medium size and properly proportioned con- 
 nections, the single-pipe system is preferable, there being but one 
 valve to operate and only one-half the number of risers passing 
 through the lower rooms. 
 
 Arrangement of Risers. — Fig. 54 shows the general method of 
 making the connections for both dry and sealed returns, and Fig. 
 55 shows in detail a good way of connecting the risers with the 
 mains and branches. If the return main be overhead a siphon 
 should be placed in the drip connection. 
 
 An arrangement of the single-pipe system especially adapted 
 to buildings over three stories in height, is to carry a single large 
 riser to the attic, then branch and connect with the various drops 
 supplying the radiators on the floors below. By using this 
 method the flow of steam and condensation is in the same direc- 
 tion and smaller pipes may be used than when they are in opposite 
 directions. 
 
 This system of piping is used extensively in office buildings, 
 hotels, etc. 
 
 Expansion of Risers. — In the case of tall buildings special pro- 
 vision must be made for the expansion of the risers. For build- 
 ings of 8 or 10 stories the expansion may be taken up by swivel 
 connections in the basement like those shown in Fig. 56, similar 
 swings being used in the attic if the overhead- feed system is 
 used. The connections in this case should be with the bottom 
 of the main in order to secure proper drainage. In buildings 
 over 10 stories in height slip joints or expansion loops of the 
 general form shown in Fig. 57 should be placed in the riser every 
 6 or 8 stories. Expansion loops of this kind are unsightly if 
 exposed, but they may generally be concealed, either in specially 
 provided pockets in the floor or in spaces furred down below the 
 ceilings near the walls. 
 
92 
 
 HEATING AND VENTILATING PLANTS 
 
 One-Pipe Circuit Syste-m. — 'A system often employed with 
 good results in buildings of small and medium size is shown in 
 Fig. 58. In this arrangement a single main of uniform size is 
 carried entirely around the basement with a slight downward 
 pitch, the extreme end being dripped to the boiler below the water 
 line. 
 
 Fig. 57 
 
 Fig. 55. Connecting Risers with Mains and Branches. 
 Fig. 56. Swivel for Taking up Expansion in Risers. 
 Fig. 57. Expansion Loops for Risers in High Buildings. 
 
 The radiators are connected with the main through a single pipe 
 and all condensation is carried along in the lower part of the 
 main in the same direction with the steam. 
 
 This system is especially adapted to small apartment houses of 
 two or three stories where each flat is provided with a separate 
 boiler, on account of the simplicity of the piping, which eliminates 
 all return mains in the basement. 
 
 A modification of this system adapting it to larger buildings is 
 shown in Fig. 59. The riser shown in this case is one of several, 
 the number depending upon the size of the building, and may be 
 supplied either at the bottom or top as most desirable. If steam is 
 supplied at the bottom of the riser, as shown in the cut, all of the 
 drip connections with the return drop, except the upper one. 
 
DIRECT STEAM HEATING 
 
 93 
 
 should be sealed, either with a siphon loop or check valve, to 
 prevent the steam from short-circuiting and holding back the 
 condensation in the returns above. If an overhead supply is 
 used, the arrangement should be the reverse, that is, all return 
 connections should be sealed except the lowest. 
 
 Sometimes a separate drip is carried down from each set of 
 
 777 ■77777777777777777: 
 
 .^ 
 
 777: r7yr777T7777777777777777>777777777777777P77? -777777777. 
 
 Fig. 58. One-pipe Circuit System. 
 
 radiators, as shown on the lower story, and connected with the 
 main return below the water-line of the boiler. In case this is 
 done, it is well to provide a check valve in each drip near its point 
 of connection with the main. 
 
 Valves and Piping. — Whatever the system of piping used, 
 valves should be placed in the steam mains near the boiler and 
 corresponding valves in the returns. A check valve should be 
 provided in each return connection with the boiler, and should be 
 placed just outside the gate valve. This is to prevent the water 
 from flowing out of the boiler in case a partial vacuum is sud- 
 denly formed in the pipes or radiators. In buildings of any con- 
 siderable size it is well to divide the piping systern into sections 
 
94 
 
 HEATING AND VENTILATING PLANTS 
 
 by means of valves placed in the corresponding supply and re- 
 turn branches. These are for use in case of a leak in any part 
 of the system, so that it is necessary to shut off only a small part 
 of the heating system during repairs. 
 
 In tall buildings it is customary to place valves at the top and 
 
 ^^777777^7777777^, 
 
 ^ 
 
 ^ 7777?^. 
 
 
 "^^7777/////, 
 
 ' 7 7 7 r 77 7- ) h 777777^77V 
 
 7^ 
 
 CHECK V. 
 CONN. 
 
 C££££££Z£££££££^£^^ 
 
 | T | 
 
 y^yyyy'y^yyy^yyy^yy^ 
 
 I 'I i I ' I 
 
 SEALED 
 RETURN 
 
 SEALED 
 RETURN 
 
 | t| If t 
 
 Fig. 59. One-pipe Circuit System for Large Buildings. 
 
 bottom of each riser, in which case any particular one may be 
 cut out independently of the others. 
 
 The expansion of pipes has already been taken up in a previous 
 chapter. In low-pressure heating this is usually cared for by run- 
 ning the mains and branches in such a way as to provide sufficient 
 spring for taking up any expansion which may occur. Expan- 
 sion joints are seldom necessary in this class of work unless it 
 be in the case of long underground mains. 
 
DIRECT STEAM HEATING 
 Radiator Connections. 
 
 95 
 
 Radiator Connections. — Figs. 60, 61 and 6^ show common 
 methods of connecting the risers and radiators. The first shows 
 the usual form of connection for a two-pipe radiator ; the second, 
 
 ^^ 
 
 ■^jylly-/'J>////^/////^^y^,^^^^,^^^M>.r*^,7: 
 
 Wy^^^y^/^y'^^,^^,y'//yjy ,^^^y^^j.i^^;777^, 'r, 
 
 Fig. 60 
 
 
 W/M^MM/M////M/////W/MA 
 
 Fig. 61. 
 
 22ZZ. 
 
 ^///y/////^/^//////////^. 
 
 ^ 
 
 w///^yM^M^^y,-/yyy^yyy^w///M. 
 
 TZZi 
 
 t 
 
 Fig. 62. 
 Method of Connecting Risers and Radiators. 
 
 a single-pipe connection with a riser which also supplies a radiator 
 upon an upper floor, and the third, a connection with a first-floor 
 radiator, draining back into the supply main, as in the case of a 
 one-pipe circuit system. The horizontal portion of the pipe 
 between the riser and radiator should have a good downward 
 pitch toward the riser, and for the first two floors may be made 
 quite short and rigid. On the upper floors provision must be 
 made for the expansion of the riser as shown in Fig. 61. Figs. 
 63, 64 and 65 show different ways of connecting up wall coils, 
 and the proper position of the air valve in each case. 
 
 Vapor Systems. 
 
 The terms "low-pressure," "vapor" and "vacuum" are merely 
 relative when applied to steam heating. The first applying to 
 pressures ranging from 1 to 5 pounds above atmosphere, the 
 
96 
 
 HEATING AND VENTILATING PLANTS 
 
 second to lower pressures of 1 to 5 ounces, and the third to any 
 pressure below atmosphere. The object sought in both vapor 
 and vacuum heating is a simple means of regulating the tempera- 
 ture with a direct steam system. 
 
 The Webster Modulation system, shown in diagram in Fig. 
 66, is a good illustration of a vapor system, although it may also 
 be operated at pressures somewhat below atmosphere. In this 
 method of heating the usual supply valve is replaced by a gradu- 
 ated valve for varying the amount of steam admitted to the radi- 
 ator, while a water seal or thermostatic valve which allows only 
 air and condensation to pass through it is placed on the return 
 end of the radiator. In operation the air and water discharged 
 from the thermostatic valve pass into a separating tank, from 
 which the former passes to the atmosphere through a vacuum 
 
 JAIRV. 
 
 Fig. 63. 
 
 Fig. 64. Fig. 65. 
 
 Ways of Connecting up Wall Coils. 
 
 valve as indicated, while the condensation flows into the boiler 
 through the return pipe "A.'^ After the air has been discharged 
 from the radiators the system may be operated under a, low 
 vacuum if desired, as the air-valve on the separating tank is of 
 the vacuum type and any slight difference in pressure between 
 the boiler and the atmosphere will be balanced by the water 
 column in drip-pipe "B." 
 
DIRECT STEAM HEATING 97 
 
 Vacuum Systems. 
 
 Vacuum systems are of two kinds, those in which a uniform 
 pressure, less than atmospheric, exists in the entire system, includ- 
 ing the boiler, and those in which the pressure varies in different 
 parts of the system, as between the radiators and return mains. 
 
 o o 
 
 it 
 
 u m 
 
 V6 
 
 Badiator 
 
 Vacuum -g 
 Air Valve p3 
 
 -O-h 
 
 Separating 
 Tank 
 
 I Graduated 
 
 Supply 
 
 Valve 
 
 Fig. 66. Webster Modulation System. 
 
 The former is usually confined to cases where the condensation 
 returns to the boiler by gravity, as in dwellings and similar build- 
 ings, while the latter system is used principally in large plants 
 where exhaust steam is employed for heating and it is desired to 
 maintain a low back-pressure upon the engines. 
 
 Only the uniform-pressure system will be considered in the 
 present chapter, the other coming more strictly under the head of 
 exhaust steam heating. 
 
 Most of the vacuum systems in use employ some form of pat- 
 ented device for removing the air and for automatically maintain- 
 ing a slight vacuum within the radiators. Any low-pressure heat- 
 
98 
 
 HEATING AND VENTILATING PLANTS 
 
 ing system may be transformed into a vacuum system, provided 
 the joints are sufficiently tight, by substituting vacuum air valves 
 in place of the usual automatic valves; these being so designed 
 as to allow the air to pass out of the radiators when the steam 
 pressure within is slightly above that of the atmosphere. When 
 the air is once expelled, the steam pressure may be allowed to 
 drop through a considerable range while the valve remains closed 
 and does not allow the air to enter the radiator. 
 
 The Eddy vacuum system, shown in diagram in Fig. 67, illus- 
 trates the application of this principle to practical work. In this 
 case the usual air valve is replaced by a "retarder," so called, 
 which has a minute opening, and allows air and steam to flow 
 from the radiator into the air-line when under a slight pressure. 
 
 BetarderOt 
 
 Vacuum 
 Air VaJve 
 
 D 
 
 Betarder 
 
 Air-Line 
 
 
 Reoeiving 
 
 Return 
 Water 
 Valve 
 
 Air Vent 
 
 J 
 
 Radiator 
 
 u 
 
 steam to Bad. 
 
 _WaterIjine^ 
 Boiler 
 
 Main Return 
 
 Fig. 67. Eddy Vacuum System. 
 
 The air-line, in turn, connects with a receiving tank placed 
 above the water-line of the boiler, and which is provided with a 
 vacuum air valve. In operation, a steam pressure of about 1 
 pound is first raised for clearing the system of air, after which 
 it may be dropped to a point where the temperature of the steam 
 
DIRECT STEAM HEATING 
 
 99 
 
 is just sufficient to give off the required amount of heat for 
 warming the building. Any steam which passes through the re- 
 tarders is condensed in the receiving tank, from which it passes 
 to the boiler through the return-water valve shown in the cut. 
 
 Construction of Pipe Lines. 
 
 Pipe Sizes. — The proportioning of the steam-pipe sizes in a 
 heating plant is a matter of much importance and should be care- 
 fully worked out by methods which experience has shown to be 
 correct. Assuming a radiator efficiency of 290 B. T. U. per 
 square foot of surface per hour, which covers all classes of direct- 
 steam radiation, and taking the latent heat of steam at 2 pounds 
 pressure as 960 B. T. U., we find that each square foot of surface 
 
 Table XXVII. 
 Area of Radiating Surface for Different Pipe Sizes. 
 
 Diameter 
 
 Square feet of radiating surface 
 
 of pipe, 
 
 5 pound drop in 
 
 i pound drop in 
 
 inches 
 
 pressure 
 
 pressure 
 
 
 in 100 feet 
 
 in 200 feet 
 
 1 
 
 80 
 
 56 
 
 IJ 
 
 145 
 
 103 
 
 n 
 
 190 
 
 134 
 
 8 
 
 52S 
 
 870 
 
 2J 
 
 950 
 
 670 
 
 3 
 
 1550 
 
 1080 
 
 3J 
 
 2.320 
 
 1625 
 
 4 
 
 3260 
 
 2280 
 
 5 
 
 5800 
 
 4060 
 
 a 
 
 9320 
 
 6520 
 
 ■1 
 
 13800 
 
 9660 
 
 8 
 
 19440 
 
 13600 
 
 will condense 300 -f- 960 = 0.3 pound of steam per hour, which 
 is commonly taken as 1/3 pound. 
 
 While this is slightly more than would be obtained with cast- 
 iron sectional radiators, it is on the side of safety and is partly 
 offset by the f rictional resistance of bends and other obstructions. 
 
 Table XXVII. is based on a condensation of 1/3 pound of 
 steam per square foot of radiation per hour and has been com- 
 puted from the formula and tables given in Chapter I. for the 
 flow of steam. 
 
 The figures in the second column for 14 pound drop in 100 feet 
 may be used for all ordinary conditions with steam pressures from 
 
100 HEATING AND VENTILATING PLANTS 
 
 2 to 5 pounds, and for even lower pressures in small buildings. 
 Column three is to be used in the case of exhaust-steam heating 
 where the condensation flows back to the receiving tank by 
 gravity, and it is desired to keep the back pressure on the engines 
 as low as possible. 
 
 Since the main of a circuit system must carry both steam and 
 water of condensation, it should be made considerably larger in 
 proportion to the surface supplied than mains which are dripped 
 at frequent intervals, or which carry only the condensation in the 
 main itself. 
 
 Sizes ample for circuit mains are given in Table XXVIII. 
 
 In the two-pipe system, sizes for the supply risers may be 
 
 Table XXVIII. 
 Areas for Different Sizes of Cikcuit Mains. 
 
 if circuit 
 
 Square feet of 
 
 , inches 
 
 radiating surface 
 
 2 
 
 200 
 
 2J 
 
 350 
 
 3 
 
 600 
 
 85 
 
 900 
 
 4 
 
 1200 
 
 5 
 
 2000 
 
 6 
 
 3000 
 
 taken from Table XXVII., because the conditions in this case 
 are practically the same as in the mains and branches. 
 
 In the single pipe system, where the steam and condensation 
 flow through the same pipe in opposite directions, it is customary 
 to base the size upon the velocity of the steam. 
 
 Table XXIX. gives pipe sizes for velocities of 10 and 15 feet 
 per second. The lower velocity is better for general use, espe- 
 cially in case of the smaller sizes. When it is desired to limit the 
 size of riser, between the lowest radiator and the main, the 
 higher velocity will usually be found satisfactory, especially for 
 pipes 2 inches in diameter and above. 
 
 It will be noticed that the sizes in Table XXIX. for a given 
 radiating surface are considerably larger than required for the 
 mains and branches. When laying out a system of piping it is 
 customary to make the short branches between the main and 
 
DIRECT STEAM HEATING 
 
 101 
 
 risers the same size as the latter, as it reduces the velocity of the 
 steam near the base of the riser, thus preventing the condensation 
 from being carried up with the steam. 
 
 Table XXX., for the connections between the risers and radi- 
 ators, is based on practice and will be found to correspond very 
 closely with the tappings of standard makes of radiators. 
 
 Returns. — The size of a return pipe is usually a matter of cus- 
 tom and judgment rather than computation. It is common prac- 
 tice among steam fitters to make the returns one size smaller than 
 the corresponding steam pipes. This is a good rule for the 
 smaller sizes, but gives a larger return than is necessary for the 
 larger sizes of pipe. Table XXXI. gives different sizes of steam 
 pipes with the corresponding diameters for dry and sealed re- 
 turns. 
 
 Table XXIX. 
 Areas of Radiator Surface for Different Risers. 
 
 10 feet per second velocity 
 
 15 feet per second velocity 
 
 Diameter of 
 
 Square feet 
 
 Diameter of 
 
 Square feet 
 
 pipe, inches 
 
 of radiation 
 
 pipe, inches 
 
 of radiation 
 
 1 
 
 30 
 
 1 
 
 50 
 
 li 
 
 80 
 
 li 
 
 90 
 
 n 
 
 80 
 
 li 
 
 120 
 
 2 
 
 130 
 
 2 
 
 800 
 
 3J 
 
 190 
 
 2i 
 
 390 
 
 .3 
 
 290 
 
 8 
 
 340 
 
 35 
 
 390 
 
 3S 
 
 590 
 
 The length of run and number of turns in a return pipe should 
 be noted and any unusual condition provided for. Where the 
 condensation is discharged through a trap into a lower pressure 
 the size may be slightly reduced, especially among the larger 
 pipes, depending upon the difference in pressure. 
 
 Floor and Ceiling Plates. — Where pipes pass through floors or 
 partitions the woodwork should be protected by galvanized iron 
 sleeves having a diameter from % to 1 inch greater than the pipe. 
 
102 
 
 HEATING AND VENTILATING PLANTS 
 
 Fig. 68 shows a form of adjustable floor sleeve which may be 
 lengthened or shortened to conform to the thickness of the floor 
 or partition. The ceiling plate in this case is fastened to the 
 sleeve by small steel wires passing up through holes provided for 
 them. There are a number of forms of ceiling plates which are 
 
 Table XXX. 
 Sizes of Connections Between Risers and Radiators. 
 
 Square feet of 
 radiation 
 
 10 to 84 
 84 to 48 
 48 to 96 
 96 to 150 
 
 Two-pipe connection 
 
 Diameter of Diameter o£ 
 
 steam pipe, 
 inches 
 
 1 
 
 li 
 
 15 
 
 return pipe, 
 inches 
 
 1 
 
 Single pipe connection 
 10 to 24 1 
 
 81 to 00 IJ 
 
 60 to 80 IJ 
 
 80 to 130 2 
 
 Table XXXI. 
 Sizes of Returns. 
 
 Diameter of 
 
 Diameter of 
 
 Diameter of 
 
 steam pipe. 
 
 dry return, 
 
 sealed return. 
 
 inches 
 
 inches 
 
 inches 
 
 1 
 
 1 
 
 i 
 
 11 
 
 1 
 
 1 
 
 U 
 
 n 
 
 1 
 
 2' 
 
 u 
 
 U 
 
 2J 
 
 2 
 
 IJ 
 
 3 
 
 25 
 
 2 
 
 35 
 
 2J 
 
 8 
 
 4 
 
 3 
 
 25 
 
 5 
 
 3 
 
 25 
 
 6 
 
 35 
 
 3 
 
 7 
 
 35 
 
 3 
 
 8 
 
 4 
 
 35 
 
 9 
 
 5 
 
 34 
 
 10 
 
 B 
 
 4 
 
 12 
 
 6 
 
 B 
 
 fastened directly to the pipe. These are not desirable as the ex- 
 pansion and contraction of the pipe soon pushes them away from 
 the ceiling, thus producing an unsightly appearance. 
 
DIRECT STEAM HEATING 
 
 103 
 
 Boiler Equipment. 
 
 Boilers. — The best type of boiler will depend upon the kind of 
 building to be heated, and also to a considerable extent upon its 
 size. 
 
 For dwelling houses, and school buildings and churches of 
 small size, some form of cast-iron boiler is usually employed. 
 
 These are commonly rated according to the direct radiating 
 surface which they will supply. Catalogue ratings, however, 
 should not in general be used, and it is better to compute the 
 necessary grate surface as described in Chapter V. 
 
 Fig. 68. Adjustable Floor Sleeve for Protection of Woodwork. 
 
 If catalogues are to be relied upon, only about 75 per cent of 
 the rating should be taken, and this should include steam mains 
 and risers as heating surface unless they are thoroughly insulated. 
 
 For larger building, tubular boilers are generally employed. 
 The method of computing the size of these boilers for heating 
 purposes has already been given in Chapter V. 
 
 Boiler Connections. — The connections for cast-iron heating 
 boilers are simple. If a single boiler is used, valves should be 
 placed in both the supply and return mains, and a check valve 
 should also be provided in the latter outside of the gate valve. 
 As low pressures are carried, the boiler may be fed under city 
 pressure, through one of the return headers. Both stop and 
 check valves should be placed in the feed pipe. Connections pro- 
 
104 
 
 HEATING AND VENTILATING PLANTS 
 
 vided with gate valves and plug cocks should be made for drain- 
 ing the boiler and return mains separately, if desired. When two 
 boilers are set in a battery the steam connections should lead into 
 a common header, stop valves being placed in the pipe from each 
 boiler. The returns should be made up in a similar manner. In 
 addition to the above, there should be an equalizing pipe of the 
 same size as the leads for maintaining an equal pressure in both 
 boilers when running together. 
 
 Fig. 69. Method of Connecting Two Boilers. 
 
 Fig. 6'9 shows in diagram the method of making the connec- 
 tions for two boilers when the condensation returns by gravity. 
 
 When tubular boilers are employed it is customary to take the 
 steam from the rear nozzle as it contains less moisture at this 
 point than at the other end which is directly over the hottest part 
 of the fire. Boilers of this type are usually provided with an in- 
 ternal feed pipe so arranged as to discharge the water in the 
 coolest part, which is between the shell and tubes about 2 feet 
 from the rear head. 
 
 Except for these two points, the connections for tubular boilers 
 are practically the same as shown in Fig. 69. Each boiler in a 
 battery should be furnished with a pressure gauge, safety-valve, 
 water-glass, and gauge cocks. Automatic damper regulators op- 
 
DIRECT STEAM HEATING 
 
 105 
 
 erated by changes in the steam pressure, should always be pro- 
 vided. When a single boiler is used it is generally attached to 
 the draft door and cold-air check, but in case there are two or 
 more boilers,, a hand damper is placed in each smoke connection 
 and the automatic regulator arranged to operate a damper in the 
 main pipe. 
 
 Blow-Off Tanks.— Whtre the blow-off from a boiler dis- 
 charges into a sewer, some means must be employed for cooling 
 the water or else the joints of the sewer pipe will be injured. 
 This is accomplished by first passing the water through a special 
 chamber or receiver, called a blow-off 
 tank, one form of which is shown in Fig. 
 70. This consists of a cast iron receiver 
 A, connected with the boiler through the 
 blow-off pipe B. The tank ordinarily 
 stands full of cold water. 
 
 When hot water is admitted from the 
 boiler, any steam which is formed will be 
 carried off through the vapor pipe C, 
 which should extend through the roof of 
 the boiler house. As the hot water 
 enters the top of the tank, the cold water 
 will be forced out from the lower part 
 Fig. 70. Blow-off Tank. through the discharge pipe D, which con- 
 nects with the sewer. A small cross-connection E is provided for 
 admitting air pressure to the discharge pipe to break the siphon 
 effect and prevent the tank from being drained after the valve in 
 the pipe B is closed. This form of tank is usually sunk in the 
 ground with its top flush with the boiler-room floor, or slightly 
 above it. 
 
 Tanks of wrought-iron plate mounted on cast-iron cradles are 
 also used in large plants. 
 
CHAPTER VIII. 
 INDIRECT STEAM HEATING. 
 
 , In indirect heating the radiation is placed in the basement, and 
 the heated air conveyed to the different rooms by means of brick 
 or galvanized iron flues. 
 
 This system is adapted to practically the same conditions as 
 furnace heating, and in addition, may be successfully employed in 
 buildings of much larger size. While there is no mechanical 
 obstacle to its use in small dwellings and buildings of a similar 
 kind, it is more expensive to install than a hot-air furnace, and 
 therefore is not generally used for this purpose except in com- 
 bination with direct heating, as already stated. 
 
 Its chief advantage, as compared with furnace heating, is the 
 placing of the radiating surface directly at the bases of the ver- 
 tical flues, thus doing away with long horizontal runs of pipe and 
 reducing the frictional resistance to air flow. This results in a 
 more even distribution of air throughout the building and makes 
 the system less susceptible to the effects of outside wind pressure. 
 Other advantages are the increased ratio of heating surface to 
 grate surface, which furnishes a larger volume of air at a lower 
 temperature, and the ability to heat a building of any size from a 
 single boiler plant. Its advantages when compared with direct 
 steam, are ventilation, better temperature regulation, and the re- 
 moval of radiating surfaces and piping from the occupied rooms. 
 
 While a system of indirect steam is more expensive to install 
 than a hot-air furnace the cost of operation is practically the 
 same for an equal amount of ventilation. A considerable saving 
 in fuel is often made by using direct radiation in certain unim- 
 portant rooms, where heat only is required, but this is usually 
 offset by the more generous ventilation provided in other parts 
 of the building. 
 
 106 
 
INDIRECT STEAM HEATING 
 
 107 
 
 Types of Radiating Surface. 
 
 Cast-iron Radiators. — Indirect steam radiators are made of 
 cast iron in many different patterns, the most common being the 
 pin radiator, one form of which is shown in Fig. 71. They are 
 made in sections or slabs, and a sufficient number of these are 
 connected together to form a heater or stack, having the required 
 amount of heating surface. 
 
 An efficient form of radiator that is especially adapted to the 
 warming of large bodies of air, as in schoolhouses and similar 
 work, is shown in Fig. 7i3. This radiator as well as Fig. 71 can 
 
 Fig. 71. Pin Radiator. 
 
 be used for either steam or hot water, there being a continuous 
 passage downward from the supply connection at the top to the 
 return at the bottom. The sections are made up in stacks similar 
 to Fig. 71, except nipples are used instead of bolts. 
 
 Fig. 73 shows another form in which the extended surfaces 
 are made up of fins or blades instead of pins. The standard pin 
 radiator, rated at 10 square feet of heating surface per section, is 
 probably as well adapted to house heating as any. The sections 
 are usually made from 36 to 40 inches in length, 7 to 8 inches 
 in depth and ,3% to 33^ inches in thickness, although these di- 
 mensions may vary somewhat in different makes. The free air 
 space between the sections is about 36 square inches. 
 
 The School Pin shown in Fig. 73 is made in two sizes, rated at 
 15 and 30 square feet of surface respectively; they are each 36 
 
108 
 
 HEATING AND VENTILATING PLANTS 
 
 inches in length by 4 inches in thickness, the difference in size 
 being made up in the depth, which is 10 inches in one case and 
 14 inches in the other. The free area between the sections is- 
 about 60 square inches. 
 
 The Cardinal Radiator shown in Fig. 73 is 37^ inches long, 
 11^4 inches deep at the connecting end and Zy^ inches in thick- 
 ness. 
 
 Pipe Radiator. — A very efficient form of heater may be made 
 up of wrought-iron pipe joined together with branch tees and 
 return bends. A heater of this kind is called a box coil, and its- 
 
 Fig. 72. Radiator for School Buildings. 
 
 efiSciency is increased if the pipes in alternate rows are staggered- 
 They are commonly made six or eight pipes deep and of sufficient- 
 length and width to give the necessary heating surface and area, 
 for air flow between the pipes. 
 
 It is common to consider 3/5 to ^^ the over-all area of the- 
 heater as free for the flow of air between the pipes. 
 
 Efficiency. — The efficiency of an indirect heater depends upon 
 its form, the difference in temperature between the steam and the 
 surrounding air, and the velocity with which the air passes 
 over it. 
 
 Under ordinary conditions in dwelling-house work a good form, 
 of indirect heater will give off at least 350 B. T. U. per square 
 foot of surface per hour in zero weather, with a steam pressure 
 of 3 to 5 pounds. 
 
 In the case of schoolhouses and similar buildings where large 
 volumes of air are warmed to moderate temperatures, about 550' 
 
INDIRECT STEAM HEATING 109 
 
 B. T. U. are given off per square foot per hour with steam at the 
 same pressure. This increase is due to the higher velocity of the 
 air passing over the heater and to its lower average temperature. 
 In hospital work where the conditions come between those of 
 dwelling houses and school buildings, an efficiency of 450 B. T. U. 
 may be assumed. 
 
 Computing Indirect Radiation. 
 
 Calculations for Schoolhouses. — The principles involved in in- 
 direct steam heating are similar to those already described under 
 
 Fig. 73. Radiator with Fins. 
 
 furnace heating. In the case of schoolhouses, churches, etc., 
 where the air volume is large in comparison with the heat loss by 
 transmission and leakage, it is customary to compute the heat 
 requirements for warming and ventilation separately, add the 
 results, and divide the sum by the efficiency assumed for this class 
 of work. 
 
 Example. — The heat loss from a standard class room by trans- 
 mission and leakage in zero weather is 40,000 B. T. U. per hour. 
 The air supply for ventilation is to be 96,000 cu. ft. per hour. 
 How many square feet of surface should the heating stack con- 
 tain ? 
 
 The heat required to raise the temperature of the entering air 
 from 0° to 70° is 96,000 X 1-3 = 134,800 B. T. U. per hr., mak- 
 ing a total of 40,000 -f 124,800 = 164,800 B. T. U. This, di- 
 
no HEATING AND VENTILATING PLANTS 
 
 vided 'by 550, the assumed efficiency of the radiation, calls for 
 164,800 -H 550 = 300 sq. ft. of surface in the stack. 
 
 Calculations for Dwellings. — The relation between air supply 
 and heat loss in dwellings varies decidedly from that in school- 
 houses, and therefore a different method is employed in deter- 
 mining the radiating surface. A room in a dwelling house, with 
 a comparatively large outside exposure, may have only two or 
 three occupants; hence, it would be necessary to raise the small 
 amount of air needed for ventilation to a very high temperature 
 in order to bring in the required amount of heat. In another 
 room the conditions might be reversed. A method often em- 
 ployed in this class of work, and which seems to 'apply well to 
 average conditions, is to compute the required amount of direct 
 radiation for warming the room and multiply the result by 1.5. 
 
 It usually happens that only a part of the rooms in a dwelling 
 house are heated by indirect radiation, so it is a simple matter to 
 determine the size of direct radiators for all of the rooms and 
 then increase the surface 50 per cent for those which are to have 
 indirect heat. 
 
 Example. — The heat loss from a room by transmission and 
 leakage is 15,000 B. T. U. per hour in zero weather. How many 
 square feet of indirect radiation will be required to warm it ? 
 
 1^'000-X1.5 = 90 sq.ft. 
 
 250 
 
 Calculations for Hospitals. — The conditions to be provided for 
 in the indirect heating of cottage hospitals come between those of 
 dwellings and schoolhouses. In this case the air supply is pro- 
 portioned to the number of occupants as in schools, but the 
 arrangements of flues and registers are more nearly like those in 
 dwelling house work where the air-flow is more sluggish. Under 
 these conditions the total heat for warming and ventilation is 
 computed, as previously described, and the result in B. T. U. 
 divided by 450, the efficiency given for this class of work. 
 
 Example. — A ward in a cottage hospital requires 60,000 cu. ft. 
 of air per hour for ventilating purposes. The heat loss by trans- 
 mission and leakage is 120,000 B. T. U. per hour in zero weather. 
 
INDIRECT STEAM HEATING 111 
 
 How many square feet of indirect radiation will be required 
 
 under these conditions? 
 
 Heat for ventilation, 60,000 X 1.3 = 78,000 
 Heat for warming, 120,000 
 
 Total per hour 19i8,000 B. T. U. 
 
 From this we find 198,000 -h 450 = 440 sq. ft. of surface are re- 
 quired. 
 
 Stack Casings ani Supports. 
 
 Construction. — The casings for .enclosing the heating stacks 
 are usually constructed of galvanized iron, although brick cham- 
 bers are sometimes employed for those of large size. 
 
 When sheet metal is used it should be made up in such a 
 manner that the casing may be easily removed for reaching the 
 heater. The gauge of iron for this purpose will depend some- 
 what upon the size of stack. No. 2i2 being commonly used for 
 the larger sizes and No. 34 for the smaller ones. The casings 
 should be made up in sections, stiffened with V strips or light 
 angle iron, and put together with small "stove bolts." Access to 
 the heater should be provided by means of doors or slides. Brick 
 chambers are generally constructed with 8-inch walls and covered 
 with asbestos block or other insulating material supported on 
 small tee bars resting on the brick work. When this covering is 
 used it should be finished with a layer of plastic asbestos for clos- 
 ing the cracks between the blocks and making it air tight. 
 
 Cast-iron doors of good size should be furnished for admis- 
 sion to the chamber below the heater and smaller ones for in- 
 specting the space above. 
 
 Method of Support. — When sheet metal casings are employed 
 the heating stacks are usually hung from the overhead floor con- 
 struction. If this consists of wood, lag screws are used for attach- 
 ing the hangers to the joist above. If the building is of fireproof 
 construction the rods are either clamped to the lower flanges of 
 the floor beams or extend into the masonry where they are pro- 
 vided with metal plates or large washers. The lower ends 
 of the hangers are made in the form of a hook or eye and 
 an iron bar or piece of pipe run through for supporting the 
 heater. 
 
112 
 
 HEATING AND VENTILATING PLANTS 
 
 Arrangement of Heater. — Fig. 74 shows a section through a 
 stack and galvanized iron casing arranged for introducing warm 
 air into a room through a floor register. The cold-air chamber 
 is seen at the bottom of the casing, and the air in passing through 
 
 FLOOR J^EGISTER 
 
 GALVANIZED IRON CASING 
 
 Fig. 74. Anangement of Heater. 
 
 the spaces between the sections becomes heated and rises through 
 the register to the room above. 
 
 With this arrangement there is no way of regulating the tem- 
 
 FLOOR REGISTER 
 
 GALVANIZED IRON SUDING 
 CASING DOOR 
 
 Fig. 75. Heater with Mixing Damper for Regulating Air Temperature. 
 
 perature of the room except by closing or partially closing the 
 register and thus shutting off the air supply. 
 
 Where indirect stacks are used in dwelling houses and similar 
 work, the height of the warm-air space above the sections 
 should be made at least 8 inches, while 10 or li^ inches is better 
 for stacks of large size. The cold-air space is commonly made a 
 little less, but if there is ample room it is well to make it the 
 same. 
 
 In schoolhouses and churches, where larger volumes of air must 
 
INDIRECT STEAM HEATING 
 
 113 
 
 pass through the heaters, these spaces should be based upon the 
 velocity of flow as described later. 
 
 Mixing Dampers, — Fig. 75 shows a heater equipped with a 
 mixing damper for regulating the temperature of the air enter- 
 ing the room without diminishing the volume to any extent. 
 
 The action of this device is evident from the cut; and by set- 
 ting the damper in different positions the proportions of hot and 
 cool air admitted to the room may be varied at will. The effect- 
 
 Fig. 76. Brick Casings for Stacks. 
 
 iveness of a mixing damper is limited to some extenrby the fact 
 that the cool air must pass under the heater in order to reach the 
 flue. 
 
 This results in the air becoming more or less heated and so 
 reduces its cooling effect. However, a certain amount of heat 
 is usually required, and this defect is not of much importance 
 except in very mild weather. Different methods may be em- 
 ployed for overcoming this action if desired, such as bringing 
 the cool air to the mixing damper through a separate flue, etc. 
 
 'An arrangement of heater and damper, in connection with a 
 brick chamber, is shown in Fig. %Q. 
 
 It will be noticed in this case that a hood is placed over the 
 lower opening leading to the mixing damper in order to take the 
 cold air supply from the bottom of the chamber at a considerable 
 distance from the heater. 
 
114 
 
 HEATING AND VENTILATING PLANTS 
 
 Another defect of the mixing damper is the difficulty experi- 
 enced in obtaining a thorough mingling of the hot and cool air 
 before it enters the room. This is especially noticeable in the 
 case of first-floor rooms where the connection between the damper 
 and register is short. The same difficulty appears in schools and 
 similar buildings, even where the air is brought into the rooms 
 
 Fig. 77. Mizing Damper with Flue. 
 
 at a considerable elevation, unless care is taken to admit the cool 
 air at the back of the flue. The reason for this is illustrated in 
 Fig. 77, where the hot air is represented by crooked arrows and 
 the cool air by straight ones. When these currents enter the 
 room, the hot air tends to rise and the cool air to fall. Therefore, 
 with the arrangement shown in the cut there will be a thorough 
 mixing of the two currents as they pass through the register. If 
 the room inlet were on the other side of the partition, so that the 
 cool air passed up the front of the flue, this mixing process would 
 not take place and drafts of cold air would fall directly upon the 
 heads of those sitting below. 
 
 In cases of this kind it is necessary to lower the heater and 
 
INDIRECT STEAM HEATING 
 
 115 
 
 bring the cool air to the mixing damper above it through a special 
 passage. In order to be effective, mixing dampers should be 
 carefully constructed with reference to the non-leakage of either 
 hot or cold air. They should be operated from the rooms. with 
 which they connect, and be provided with simple means for hold- 
 ing in any desired position. 
 
 Heating Two or More Rooms. — Two or more rooms may be 
 heated from a single stack provided the arrangements are such 
 
 Galvanized Iron Casing 
 Fig. 78. Airangement of Stack for Heating Two Rooms. 
 
 as to divide the air supply among the different flues in the right 
 proportion. This is usually accomplished by separating the hot- 
 air space by partitions, as shown in Fig. 78, giving to each room 
 its proper share of heating surface. In the case of brick cham- 
 bers, the partitions should extend for a couple of feet below the 
 sections in order to prevent a circulation of air across the bottom 
 of the heater. This would tend to warm the entire air supply in 
 the lower part of the chamber and so interfere with the effective- 
 ness of temperature regulation at the different mixing dampers. 
 Heating by Air Rotation. — Cases sometimes occur where it 
 is desirable to warm a given room at certain periods when ven- 
 tilation is not required. This applies to rooms occupied for only a 
 portion of the time, and to the quick warming of a room or 
 building in the morning. An arrangement for air rotation is 
 shown in Fig. 79, in which the supply may be taken either from 
 
116 HEATING AND VENTILATING PLANTS 
 
 outside or from the room with which the heater connects, thus 
 passing the same air through the stack over and over again. 
 
 Sometimes, as in front halls and vestibules, it is desired to re- 
 tain the appearance of indirect heating by using a register, while 
 depending upon leakage for purposes of ventilation. In cases of 
 this kind, the general arrangement shown in Fig. 79 may be used 
 without the outside air connection. Under these conditions the 
 two registers are placed close together, as in Fig. 80, or, if de- 
 sired, a single long register face may be employed, one end con- 
 
 Fig. 79. Register and Damper for Heating Only. 
 
 necting with the cold-air downtake and the other with the warm- 
 air uptake. 
 
 Steatn-Pipe Connections. 
 
 The two-pipe system, with dry or sealed returns, is used in 
 indirect heating. The conditions to be met are practically the 
 same as in direct heating, the only difference being that the radia- 
 tors are at the basement ceiling instead of on the floors above. 
 The method of making the supply and return connections does 
 not differ essentially from those used in the direct system. 
 
 A typical layout for connecting up an indirect heater is shown 
 in Fig. 81. 
 
 As the stacks are located in the basement, their height above 
 the water line of the boiler is limited, and care should be taken 
 that the drop in pressure is not sufficient to cause the condensation 
 to rise into them through the return piping. In estimating for 
 this condition it may be assumed that a drop in pressure of 1 
 pound will raise the water level .21/^ feet. In buildings of 
 moderate size a minimum elevation of 2 feet above the normal 
 waterline will usually be found sufficient. 
 
INDIRECT STEAM HEATING 
 
 117 
 
 Pipe Sizes. — The pipe sizes may be computed the same as for 
 direct heating by counting each square foot of surface as two of 
 
 Cold-a ir Reg. 
 
 Hot-a ir Reg. 
 
 
 
 
 
 
 
 
 
 Door 
 
 
 Heater 
 
 
 Door 
 
 
 
 
 
 
 
 
 
 
 
 Galvanized Iron Casing 
 Fig. 80. Rotation Heater for Halls and Vestibules. 
 
 &!p 
 
 Q 
 
 MAIN RETURN 
 
 Fig. 81 . Connections in Two-pipe System of Indirect Heating. 
 
 direct. Table XXXII. has been prepared upon this basis, which 
 assumes that 2/3 of a pound of steam will be condensed per hour 
 by each square foot of heating surface. 
 
118 
 
 HEATING AND VENTILATING PLANTS 
 Warm-Air Flues. 
 
 The required size of the warm-air flue between the stack and 
 register depends, first, upon the diflference in temperature be- 
 tween the outside air and that in the flue; and, second, upon the 
 height of the flue. 
 
 Table XXXII. 
 
 Indirect Steam-Pipe Sizes Required for Various Areas of Heating 
 
 Surface. 
 
 Diameter of 
 pipe. 
 
 Square feet of indirect radiation which will be 
 supplied with 
 
 inches 
 
 1 pound drop in 100 feet 
 
 i pound drop in 200 feet 
 
 1 
 
 40 
 
 28 
 
 11 
 
 78 
 
 61 
 
 Ih 
 
 95 
 
 67 
 
 2 
 
 263 
 
 185 
 
 25 
 
 475 
 
 335 
 
 3 
 
 775 
 
 540 
 
 3J 
 
 1160 
 
 812 
 
 4 
 
 162S 
 
 1140 
 
 5 
 
 2900 
 
 2030 
 
 6 
 
 4660 
 
 3260 
 
 7 
 
 6900 
 
 4830 
 
 8 
 
 9720 
 
 6800 
 
 The method of computing the theoretical velocity of air-flow 
 has been described in Chapter I. In practical work it is custom- 
 ary to use areas or velocities based upon experience rather than 
 to make accurate computations. 
 
 Flues for Dwelling Houses. — In dwelling houses it is common 
 practice to allow 2 square inches area for each square foot of 
 indirect radiation when the room is on the first floor, and 1% 
 square inches for the second and third floors. In the case of 
 hospitals, where a larger volume of air is required, these figures 
 may be increased to 3 square inches for first floor wards and 2 
 square inches for those on the upper floors. 
 
 Flues for Schoolhouses. — In schoolhouses and halls, where a 
 definite volume of air is to be supplied, it is customary to base 
 the flue area upon an assumed velocity rather than upon the 
 amount of heating surface in the connecting stack. It is evident, 
 that with a constant inside temperature, the flue velocity will vary 
 with the outside temperature and also with changes in the direc- 
 
INDIRECT STEAM HEATING 119 
 
 tion and strength of the wind. For these reasons it is necessary 
 to assume velocities which will represent average conditions 
 throughout the heating season. The figures given below are 
 based upon experience and should give satisfactory results for all 
 ordinary work of this kind. 
 
 1st floor i2i60 feet per minute. 
 
 2d " aao " " 
 
 3d " 380 " " 
 
 As the velocities will be increased somewhat in windy or ex- 
 tremely cold weather, throttling dampers should be provided for 
 use at such times. 
 
 Example. — The air supply of a schoolroom on the third floor 
 is to be 1,600 cubic feet per minute; what should be the area of 
 the warm air flue? 
 
 1,600 
 
 3,80 
 
 = 4.2 sq. ft. 
 
 Cold- Air Supply Ducts. 
 
 The cold-air ducts supplying the stacks should be planned in a 
 manner similar to that described for furnace heating. The inlets 
 should, when possible, be on the north and west sides of the 
 building, unless trunk lines can be carried entirely through with 
 inlets at each end. This, in large and important buildings, makes 
 the better arrangement and should be provided when possible. 
 
 Area and Construction of Ducts. — The area of the cold-air duct 
 for any stack should be at least three fourths of the total area 
 of all the warm-air ducts leading from it. If the duct is of any 
 considerable length or contains sharp bends, it should be made 
 the full size of the warm-air ducts. 
 
 Adjusting dampers should be placed in the supply to each 
 separate stack. 
 
 If a trunk line with two inlets is used, each should be of suffi- 
 cient size to furnish the full amount of air required, and should 
 be provided with cloth checks for preventing an outward flow of 
 air, when the entire supply is taken through a single inlet. 
 
 All fresh-air inlets should be furnished with some form of 
 
120 HEATING AND VENTILATING PLANTS 
 
 damper or slide, outside of which should be placed a wire grille 
 backed with a netting of about i^-inch mesh. 
 
 Special arrangements for schoolhouses and hospitals are given 
 in a later chapter. 
 
 Vent Flues. 
 
 In dwelling houses vent flues are often omitted, the frequent 
 opening of doors and leakage around doors and windows being 
 depended upon to carry away the impure air. While this will 
 usually be found sufficient for rooms having only two or three 
 occupants, a fire-place or special vent flue should be provided in 
 the more important rooms, especially where gas jets or lamps are 
 burned in the evening. When the latter arrangement is used, 
 flues of heavy tin or galvanized iron are run to the attic space 
 through partitions or closets, and there gathered together and 
 carried outboard through a brick flue beside the boiler or range 
 chimney. This method provides a warm vent flue which tends to 
 accelerate the flow of air through it. Sometimes the room vents 
 are simply carried to an open attic and the air allowed to find its 
 way out by leakage through the, roof construction. 
 
 Toilet and bath-rooms should, if possible, connect with a warm 
 flue, through the local vent of the closet. The common practice 
 of carrying an unheated vent pipe to the atmosphere is of no 
 use whatever, and is better omitted. 
 
 Dimensions of Flues. — The areas of the vent flues in this 
 class of work are usually based on the size of the heating stack, 
 but are made the opposite of the warm-air flues because the 
 heights of the heated air columns are reversed. That is, first floor 
 rooms have short supply flues and long vent flues, while the rela- 
 tions become the opposite of this on the upper floors. Basing the 
 size of vent flue upon the above, we have the following for 
 average conditions. 
 
 Dwelling Houses 
 
 
 Vent flue area per 
 
 
 square foot of indirect 
 
 Story 
 
 radiating surface 
 
 1st 
 
 \yi sq. inches 
 
 2nd 
 
 2 sq. inches 
 
 .3rd 
 
 2}4 sq. inches 
 
INDIRECT STEAM HEATING 
 
 121 
 
 
 Cottage Hospitals 
 
 
 Vent flue area per 
 
 
 square foot of indirect 
 
 Story 
 
 radiating surface 
 
 1st 
 
 2 sq. inches 
 
 2nd 
 
 3 sq. inches 
 
 3rd 
 
 4 sq. inches 
 
 Velocity of Air in Flues. 
 
 In order to secure a flow of air through a vent flue there must 
 be an acting force to produce it. 
 
 Fig. 82. Aspirating Coil for Small Flue. 
 
 In gravity heating this is due to the higher temperature within 
 the flue, as already described for the warm-air pipes. 
 
 This temperature difference, and the resulting velocity, is 
 usually less than in the corresponding supply flue, and is offset 
 partly by the smaller quantity of air passing through the vent, 
 due to leakage, and partly by increasing the size of flue. 
 
 In dwelling houses it is customary to make the corresponding 
 supply and vent flues about the same size, while in schools and 
 halls the vents are made somewhat larger, being based upon 
 average velocities about as follows : 
 
 1st story 320 feet per minute. 
 2d " 260 " " 
 3d " 200 " " 
 
 In estimating the volume of air passing through a vent flue 
 it is customary to assume that about three-fourths of the air 
 
122 
 
 HEATING AND VENTILATING PLANTS 
 
 entering the room through the supply register will pass out by 
 way of the vent, the remainder being disposed of by leakage. 
 
 Aspirating Coils. — While a flue beside a warm chimney will 
 often answer in case of a dwelling house, vents from hospital 
 wards and other important rooms require a greater degree of 
 heat than can be obtained in this way. In work of this kind it 
 is customary to place a heater within the flue, called an aspirating 
 coil. For single wards, and rooms having vent flues not exceed- 
 ing 1 square foot in area, a loop of 1 inch pipe, similar to that 
 shown in Fig. 83, and 10 or 12 feet in height, will usually give 
 sufficient heat to produce the desired velocity. 
 
 Fig. 83. Aspirating Coils for Large Flues. 
 
 For large flues, the form shown in Fig. 83 has been found to 
 give good results. The heating surface in this case is made up of 
 tubes, having interior diaphragms, screwed into a cast-iron 
 header. For ordinary conditions, two of these, with a tube 
 length equal to twice the depth of flue, placed in an inclined posi- 
 tion as shown in the cut will give sufficient heat and provide ample 
 area for the flow of air. 
 
 The formula for computing the velocity of air flow under dif- 
 ferent conditions of temperature and height of flue has been 
 given in Chapter I. Table XXXIII. has been computed by this 
 formula for flues of different heights and for temperature dif- 
 ferences ranging from 5° to 50°, and has been corrected for fric- 
 tional resistance by reducing the theoretical results one-half. 
 
 The velocities given in the above table apply especially to 
 straight flues with smooth interiors like galvanized iron. For 
 
INDIRECT STEAM HEATING 
 
 123 
 
 those having abrupt turns or laid up with rough bricks, the veloc- 
 ities will be somewhat reduced. 
 
 In practical work the height of flue is usually fixed, and also 
 the velocity, within certain limits. Under these conditions it 
 becomes necessary to compute the size of aspirating coil to pro- 
 duce the desired velocity of air flow through a flue of given di- 
 mensions. 
 
 In cases of this kind a velocity of 200 to 320 feet per minute 
 may be assumed for flues ranging from 20 to 50 feet in height, 
 and the temperature difference necessary to produce the required 
 
 Table XXXIII. 
 Velocittes of Air-Flow in Feet Per Minuie. 
 
 Height of 
 flue in 
 
 Excess of temperature of air in flue above that of external air (D) 
 
 
 
 
 
 
 
 feet 
 
 60 
 
 10° 
 
 15° 
 
 20° 
 
 30° 
 
 50° 
 
 5 
 
 55 
 
 76 
 
 94 
 
 109 
 
 134 
 
 167 
 
 10 
 
 77 
 
 108 
 
 133 
 
 153 
 
 188 
 
 242 
 
 15 
 
 94 
 
 133 
 
 162 • 
 
 188 
 
 230 
 
 297 
 
 20 
 
 108 
 
 153 
 
 188 
 
 217 
 
 865 
 
 342 
 
 25 
 
 181 
 
 171 
 
 210 
 
 242 
 
 297 
 
 883 
 
 80 
 
 183 
 
 188 
 
 230 
 
 265 
 
 325 
 
 419 
 
 35 
 
 143 
 
 203 
 
 248 
 
 286 
 
 351 
 
 453 
 
 40 
 
 153 
 
 217 
 
 265 
 
 306 
 
 875 
 
 484 
 
 45 
 
 182 
 
 230 
 
 282 
 
 885 
 
 398 
 
 514 
 
 50 
 
 171 
 
 242 
 
 297 
 
 842 
 
 419 
 
 541 
 
 60 
 
 188 
 
 264 
 
 325 
 
 373 
 
 461 
 
 594 
 
 velocity taken from Table XXXIII. Most conditions for all 
 practical purposes are given in the table, but if others occur, 
 values for "D" may be computed by the following formula : 
 
 D= 
 
 V (4604- r) 
 
 in which 
 
 F= velocity of flow, in feet per second. 
 
 A = height of flue, in feet. 
 
 D = difference in temperature between the outside air and that in 
 the flue. 
 
 r= temperature of outside air. 
 Knowing the volume of air passing through the flue per minute, 
 
124 
 
 HEATING AND VENTILATING PLANTS 
 
 and the degrees it is to be raised in temperature, the heating sur- 
 face of the aspirating coil may be found by the formula 
 
 5= 
 
 VXT 
 380 
 
 in which' 
 
 5= square feet of heating surface in coil. 
 
 F = cubic feet of air passing through the flue per minute. 
 
 r=rise in temperature above that of the room. 
 
 Example. — The discharge ventilation -from a second floor 
 schoolroom is to be 1,500 cubic feet of air per minute through a 
 
 Fig. 84. Fig. 85. 
 
 Fig. 84. Simple Form of Hood. 
 Fig. 85 . Patented Form of Hood . 
 
 vent flue 40 feet in height and having an area of 5 sq. feet. 
 What should be the heating surface in an aspirating coil to pro- 
 duce the necessary velocity when the outside temperature is 60° ? 
 The required velocity for the above conditions is 1,500 -^ 5 = 
 300 feet per minute. Looking in Table XXXIII.- we find a 40- 
 foot flue requires a difference of i30° between the flue temperature 
 and that of the external air to produce a velocity of 306 feet per 
 minute, which corresponds very closely to the conditions of the 
 problem. With an outside temperature of 60° this calls for a flue 
 temperature of 60 -|- 20 = 80°, or 10° above the normal tempera- 
 ture of the room (70°). Substituting the known values in the 
 above formula, we find the required heating surface in the aspir- 
 ating coil to be 
 
INDIRECT STEAM HEATING 
 
 125 
 
 5= 
 
 1,500X10 
 380 
 
 = 40 sq. ft. 
 
 Vent Hoods. — Vent flues should be carried well above the ad- 
 jacent roofs in order to secure a good draft, and be provided 
 with hoods of such form as to prevent the entrance of rain or 
 snow without increasing the resistance to air flow. 
 
 Two hoods of this kind are shown in Figs. 84 and 85. 
 
 Coveriag 
 
 iBricli Flihe I 
 
 I , ■ I 
 
 Fig. 86. Vent Hood for Schools and Halls. 
 
 In the case of large vent shafts, like those in schools and halls, 
 a simple covering like that in Fig. 86 is usually sufficient. 
 
 The height of the cover or roof above the flue should be such 
 that the area beneath it on any two sides will at least equal the 
 area of the flue. Sometimes with brick flues the hood is omitted, 
 and provision made at the bottom for draining away any water 
 which may collect. All vents, except those of small size, should 
 be provided with dampers for closing when not in use. 
 
 Registers and Grilles. 
 
 Location of Registers. — Inlet registers in dwelling-house and 
 similar work are placed either in the floor or in the baseboard ; 
 sometimes they are located under the windows, just above the 
 baseboard. The object in view is to place them where the cur- 
 rents of air entering the room will not be objectionable to persons 
 sitting near the windows. A long, narrow floor register, placed 
 
126 
 
 HEATING AND VENTILATING PLANTS 
 
 close to the wall in front of a window, sends up a shallow current 
 of warm air, which is not especially noticeable to one sitting- 
 near it. 
 
 Baseboard registers should be long and low so as to distribute 
 the air as much as possible. The air supply in this case is de- 
 livered along the floor, and if used with a mixing damper set for 
 cool air, may cause uncomfortable draughts about the feet. In 
 practice one must be guided somewhat by circumstances, and 
 adopt the position found most convenient. It is sometimes de- 
 sirable to keep the floor free, on account of carpets and rugs. 
 
 Fig. 87. Section Through Floor Register. 
 
 while in other cases it is difficult to reach wall registers with 
 warm-air pipes of sufficient size, on account of the building con- 
 struction. 
 
 Registers are preferably placed near the outside walls, especially 
 in large rooms. Warm-air pipes are commonly carried up to the 
 second floor in inside partitions, but they may be run in outside 
 walls, if covered with suitable insulating material. Hair-felt is 
 often used for this purpose, but is likely to be destroyed by ver- 
 min, and seaweed quilting or air-cell covering is preferable on this 
 account. Vent registers should be placed in inside walls, near 
 the floor. 
 
 Construction. — Registers and grilles are commonly made of 
 cast-iron, steel, bronze, and wood. Floor registers should be cast 
 of solid metal on account of the hard wear which they receive. 
 
 Wall registers may be either cast, or stamped from sheet- 
 metal, the latter being lighter and more convenient to handle, 
 especially in the larger sizes. Wire grilles of either flat, square 
 or round wire are also used extensively in schoolhouses and sim- 
 ilar work. Wooden registers are not so frequently employed, but 
 
INDIRECT STEAM HEATING . 127 
 
 are sometimes used in the floors of gymnasiums, and also in 
 churches and other buildings of elaborate interior finish where 
 metal would be objectionable. Cast-iron and steel registers are 
 commonly finished in black or other colored japan, but may 
 also be plated with nickle or bronze of various shades. Plated 
 registers, however, should never be used in floors or where they 
 will receive hard usage as the plating is likely to wear off under 
 these conditions. 
 
 A section through an ordinary form of floor register is shown 
 in Fig. 87, in which A is the valve arrangement for closing off; 
 B the metal border ; C the register-box of tin or galvanized iron ; 
 and D the flue connection. 
 
 Registers may be used either with or without the valves, being 
 called "register faces" in the latter case. This arrangement is 
 often used with the larger sizes by substituting a flue damper in 
 place of the valves. 
 
 Computing Size. — The free opening, in most registers of 
 standard make, is about 3/3 the over-all area of the grille work ; 
 hence, in computing register sizes, the free area required should 
 be multiplied by 1.5 to obtain the gross or catalogue area. 
 
 The free opening should at least equal that of the flue with 
 which it connects and in some cases is made somewhat larger in 
 order to reduce the air velocity at the outlet. The various trade 
 catalogues give a large assortment of standard sizes and propor- 
 tions, which should be used when possible rather than to call for 
 special sizes and designs which are expensive to obtain. 
 
CHAPTER IX. 
 HOT-WATER HEATING BY GRAVITY CIRCULATION. 
 
 This system of heating is used extensively in the warming of 
 dwelling houses, apartments, and greenhouses on account of the 
 ease with which it may be regulated. During the mild weather of 
 spring and fall the water may be circulated at a temperature 
 just sufficient to meet the heating requirements, thus obtaining 
 one of the advantages of furnace heating, while in colder weather 
 the temperature may be raised to a point but little below that of 
 low-pressure steam. This flexibility of regulation, together with 
 the fact that any room may be reached and heated as easily as 
 with steam, are the two strong points in favor of hot- water heat- 
 ing. 
 
 As the water is normally circulated at a temperature somewhat 
 below that of steam, larger radiators are required, which adds 
 materially to the cost of installation, but on the other hand the 
 ease with which the heating capacity may be gauged to the re- 
 quirements reduces the cost of operation to a point considerably 
 below that of steam. 
 
 The principal objections to hot water are the danger of freez- 
 ing when radiators are shut off in unoccupied rooms, and the 
 length of time required to warm up a building in the morning. 
 The first of these may be overcome by opening all radiator valves 
 slightly in very cold weather, or better by drilling a very small 
 hole through the valve gate or disc, so as to produce a slight 
 circulation through the radiator at all times. A %-inch hole will 
 usually be sufficient for this purpose and the resulting loss of 
 heat is comparatively small. 
 
 While slowness in heating up may be a disadvantage in one 
 way, it is offset by the fact that when once warm, the temperature 
 of a building heated in this manner does not fluctuate so rapidly 
 as when either hot air or steam is used. 
 
 128 
 
HOT-WATER HEATING BY GRAVITY CIRCULATION 
 
 129 
 
 It may be said in this connection, that it is usually more eco- 
 nomical with any system of heating to carry an even, though 
 somewhat lower, fire during the night than to allow the house to 
 become cold. The forcing of a fire for an hour or two in the 
 morning for warming up, takes practically as much fuel as to 
 maintain a moderate fire continuously, to say nothing of the 
 added comfort secured by the latter method. 
 
 Fig. 88. Hot- Water Radiator. 
 
 Principle of Hot-Water Heating. — A system of hot-water 
 heating is similar in construction and operation to one designed 
 for steam, except that hot-water is the medium of heat trans- 
 mission from the boiler to the rooms instead of steam. The 
 force which produces a circulation through the system, and the 
 way in which it is utilized in practical work, has already been 
 described in Chapter I. A review of this matter will make it 
 clear that the velocity of flow through any given radiator will 
 
130 
 
 HEATING AND VENTILATING PLANTS 
 
 depend upon the difference in temperature between the supply 
 and return pipes, the height of the radiator above the boiler, and 
 the frictional resistance of the pipes. 
 
 Types of Direct Radiating Surface. 
 
 Cast-iron sectional radiators and circulation coils are used for 
 hot water as well as for steam. The radiator shown in Fig. 88 
 may be used for either steam or hot water ; the important feature 
 being that the sections are connected at the top as well as the 
 bottom. 
 
 AJrV. 
 
 ^Wnfnirnnl 
 
 Fig. 89. 
 
 Fig. 90. 
 
 Fig. 89. 
 Fig. 90. 
 
 Showing Circulation in Radiator with Bottom Connections. 
 Showing Circulation in Radiator with Blind Nipple. 
 
 This construction is necessary for two reasons : First, it allows 
 the air which gathers at the top of each loop to pass along to the 
 end of the radiator where it is removed by the air valve; other- 
 wise, it would be necessary to vent each section. In addition to 
 this, it allows greater freedom of circulation through the radiator 
 by providing a continuous passage along the top. The path of 
 the water depends somewhat upon the method of making the 
 supply and return connections. When both are at the bottom 
 and at opposite ends of the radiator, the entering water rises 
 through the first sections, then flows along the top through the 
 
HOT-WATER HEATING BY GRAVITY CIRCULATION 
 
 131 
 
 connecting nipples and has a downward movement through the 
 remaining sections toward the outlet as shown in Fig. SQ. 
 
 Actually there is a certain amount of circulation directly through 
 the lower part of the radiator as indicated by the arrows which in- 
 terferes somewhat with the efficiency of the radiator. This can be 
 
 Fig. 91. 
 
 S^ 
 
 b7 
 
 ^ 
 
 ^ 
 
 «^ 
 
 
 
 P 
 
 P 
 
 Fig. 92. 
 
 (S 
 
 (^ 
 
 Fig. 93. 
 Coils for Hot Water. 
 
 
 ^D 
 
 avoided in two ways, either by making the supply connection at 
 the top or by inserting a diaphragm or blind nipple between the 
 first and second sections at the bottom as shown at d in Fig. 90. 
 This latter arrangement gives a better appearance and simply 
 causes the first section to form a continuation of the flow pipe for 
 
132 
 
 HEATING AND VENTILATING PLANTS 
 
 delivering the supply at the top of the radiator. With this ar- 
 rangement there is a uniform downward movement through the 
 entire radiator, except in the first section, where it is of course 
 upward. 
 
 Wall radiators are adapted to hot-water heating as well as 
 steam. The sizes of hot-water radiators for a given number of 
 sections are the same as for steam, and the dimensions given in 
 Table XXV. may be used for both steam and water. 
 
 Fig. 94. Usual System of Hot-Water Heating. 
 
 When circulation coils are used they must be designed in such 
 a manner as to produce a continuous flow of water from the 
 supply to the return end. 
 
 Figs. 91, 9i2, and 93 show different methods of making up and 
 connecting coils for hot water. The ordinary branch coil, passing 
 around the comer of a room, can be used for this purpose when 
 properly graded. 
 
 Efficiency of Direct Radiators. 
 
 The efficiency of a direct hot- water radiator depends princi- 
 pally upon the temperature at which the water is circulated. The 
 
HOT-WATER HEATING BY GRAVITY CIRCULATION 133 
 
 best practical results in gravity heating are obtained with the 
 water leaving the boiler at a maximum temperature of about 180° 
 in zero weather and returning at about 160°, which gives an aver- 
 age temperature of 170° in the radiators. 
 
 Assuming a room temperature of 70°, and a heat transmission 
 of 1.7 B. T. U. per degree difference per square foot of surface 
 per hour, the same as for steam, we have a radiator efficiency of 
 (170 — 70) X 1.7 = 170 B. T. U., which may be used under all 
 ordinary conditions. 
 
 Systems of Piping, and Auxiliary Equipment. 
 
 System with Several Supply Branches. — -A system of hot- 
 water heating should produce a perfect circulation from the 
 boiler to the radiating surface, and thence back to the boiler 
 through the returns. The system of piping usually employed, is 
 shown in Fig. 94 and is similar to the ordinary two-pipe system 
 used for steam. 
 
 The supply or flow pipes in this arrangement are given an 
 upward pitch toward the risers, both for accelerating the flow 
 and for the prevention of air-pocketing in the mains. The re- 
 turn pipes are usually made to parallel the supplies, with a slight 
 pitch in the opposite direction. 
 
 The methods of running the supply and return risers, and of 
 making the radiator connections, are practically the same as in 
 steam heating. As the force for producing the flow is very slight 
 in gravity circulation, care should be taken to equalize the resist- 
 ance as much as possible in order to prevent short-circuiting 
 through parts of the system nearer the boiler This condition is 
 usually obtained by locating the boiler as centrally as possible and 
 carrying branches of nearly the same length to diflferent parts of 
 the building. 
 
 If for any reason this arrangement is not practicable, a single 
 main of large capacity may be carried entirely around the base- 
 ment, bringing back a return of the same size. 
 
 Pipes of this kind should not, in general, exceed 8 inches in 
 diameter, and provision should be made against short-circuiting 
 near the boiler either by taking the supply risers from the side of 
 the pipe or by the use of throttle valves. 
 
134 
 
 HEATING AND VENTILATING PLANTS 
 
 The expansion tank, shown at the top, is for catching the over- 
 flow when the water expands due to its rise in temperature, and 
 is an important feature in all hot-water heating systems. 
 
 Circuit System. — This system is similar to that already de- 
 scribed for steam, and is shown in Fig. 95. The main, which 
 should be of uniform size for its entire length, is first carried to 
 
 
 EXPANSION 
 TANK 
 
 t I 
 
 
 ■ yy'yyyyyyyyyyy/-A' ^yyyA 
 
 '77777?7 
 
 Fig. 95. Circuit System of Hot-Water Heating. 
 
 a point near the ceiling, and from here makes a complete circuit 
 of the basement with a slight downward pitch. 
 
 The supply risers are taken from the top of the main and the 
 returns are connected into the side 5 or 6 feet away in the direc- 
 tion of flow. As the cooler return water passes into the same 
 pipe it is evident that the temperature of the supply falls con- 
 tinuously throughout its length, and the sizes of the successive 
 radiators must be increased to offset it. In dwellings or apart- 
 ments of eight to twelve rooms it will usually be sufficient to 
 
HOT-WATER HEATING BY GRAVITY CIRCULATION 
 
 135 
 
 increase the surface of the last radiator about 15 per cent and the 
 intermediate ones in proportion. 
 
 Overhead System. — Fig. 96 shows a system of piping often 
 used with very satisfactory results. A single riser extends 
 directly to the expansion tank, from which branches are carried 
 to the radiators as shown. With this system of piping the air 
 
 hI^. 
 
 1 
 
 
 V>X/VX/V^^^-' 
 
 
 Fig. 96. Hot- Water, OTerhead System of Piping. 
 
 liberated from the water rises at once to the expansion tank and 
 escapes through the vent, thus preventing to a large extent its 
 collecting in the radiators. 
 
 The principal objection to this arrangement is that the water 
 in the tank is under a less pressure than in the boiler, hence, if 
 the temperature is raised above SIS" the water will break into 
 steam upon reaching the tank. No trouble will be experienced 
 from this, however, at the temperatures ordinarily carried in 
 house-heating work, and no damage will result if the tank is 
 properly vented. 
 
 The advantages of air venting noted above may be retained 
 
136 
 
 HEATING AND VENTILATING PLANTS 
 
 To Expansion 
 Tank. 
 
 without the objectionable features, by simply making a small 
 connection between the top of the riser and the tank, instead of 
 having the entire volume of water pass through it. (See Fig. 
 108). In this arrangement the air is carried off as before, while 
 the hot water does not flow into the tank in any quantity, there 
 being nothing to produce a circulation through it. 
 
 When the attic space is limited so as to 
 bring the expansion tank very near the top of 
 the riser, the main may be made to branch 
 at the ceiling directly below the upper floor, 
 and the return from the radiators above taken 
 back into the supply mains the same as in the 
 circuit system. 
 
 Pressure Systems. 
 
 In the ordinary open tank system of hot-_ 
 water heating, the temperature of the water 
 circulated through the radiators is limited to 
 something less than 212°, the boiling point at 
 atmospheric pressure. In order to raise this 
 limit and place hot water on practically the 
 same basis as steam for heating purposes, 
 "circulators" or "generators" are often used. 
 
 A generator is a device for maintaining a 
 certain pressure on the system, and at the 
 same time, allowing the surplus water due 
 to expansion to escape to the expansion tank 
 in the usual manner. Generators are of pig. 97 
 different kinds, and are commonly designed to 
 maintain a pressure of about 10 pounds, which corresponds to a 
 temperature of !240°. A device of this kind, employing a mer- 
 cury seal, is shown in Fig. 97. 
 
 This consists essentially of a cylinder C, connecting at the up- 
 per end with a chamber D by means of the tube E, the lower end 
 of which is closed by a mercury seal 1 or 2 inches in depth. The 
 generator is connected into the expansion pipe at any convenient 
 point, the inlet being in the side and the outlet from the top, as 
 indicated in the cut. When placed in a location where there is 
 
 Hot- Water Gen- 
 erator with Mercury Seal. 
 
HOT-WATER HEATING BY GRAVITY CIRCULATION 
 
 137 
 
 danger of freezing, a circulating pipe is carried to a nearby return 
 in order to keep the water constantly moving through it. When 
 in action the entire space between the mercury seal and the ex- 
 
 CONNECTION 
 
 FROM 
 
 SYSTEM 
 
 Fig. 98. 
 
 CONNECTION 
 FROM 
 SYSTEM 
 
 Fig. 99. 
 Expansion Tanks for Hot-Water Systems. 
 
 pansion tank is filled with water. As the temperature in the 
 heating system rises and the water expands, the surface of the 
 mercury is forced down in C, which causes it to rise in E. This 
 
138 HEATING AND VENTILATING PLANTS 
 
 continues until enough has been forced out of the cylinder C to 
 uncover the end of the tube, the effect of which is to allow the 
 surplus water to pass upward through the mercury into the cham- 
 ber D and thus to the expansion tank with which it connects. In 
 the meantime, the pressure must be maintained at a point suffi- 
 cient to hold the surface of the mercury slightly below the end 
 of the tube in order to provide an outlet for the water as it in- 
 creases in volume. 
 
 Other forms of generators make use of spring valves in place 
 of a mercury seal. 
 
 Expansion Tank. — Every system for hot-water heating should 
 be connected with an expansion tank placed at a point somewhat 
 above the highest radiator as shown in Figs. 94 to 9-6. The tank 
 must in every case be connected to a line of piping which cannot 
 by any possible means be shut off from the boiler. When water 
 is heated, it expands a certain amount, depending upon the tem- 
 perature to which it is raised, and a tank or reservoir should 
 always be provided to care for this increase in volume. 
 
 Two common forms of expansion tank are shown in Figs. 9i8 
 and 99, the latter being especially adapted to locations where the 
 head room is limited. The usual connections are indicated in the 
 cuts, and consist of the expansion pipe from the system, which 
 should enter the bottom of the tank; an overflow near the top, 
 usually carried down to a basement sink; and a vent pipe, which 
 should extend through the roof. If it is necessary to place the 
 tank in a cold attic or other exposed location where there is 
 danger of freezing, a circulation pipe should be taken from the 
 side of the tank, a few inches from the bottom, and connected 
 into a nearby return. 
 
 This arrangement serves to produce a continuous circulation 
 through the tank and thus prevents freezing. Water may be fed 
 into the system either at the tank or in the basement near the 
 boiler. When the latter method is employed an altitude gauge 
 should be furnished for indicating the height of the water level 
 in the tank. Sometimes a ball-cock is provided which automat- 
 ically prevents the water from falling below a given level. 
 
 Expansion tanks for dwelling house work are usually con- 
 structed of heavy galvanized iron, while steel or wrought-iron 
 
HOT-WATER HEATING BY GRAVITY CIRCULATION 139 
 
 plate, from 3/16 to 14 inch in thickness, is commonly used in 
 buildings of larger size. 
 
 The required capacity of the tank will depend upon the volume 
 of water contained in the system and the maximum temperature 
 to which it is raised. A simple rule, which has been found to 
 give satisfactory results in practice, is to find the total square 
 feet of radiation in the system, both direct and indirect, and di- 
 vide by 40. This gives the required capacity of the tank in gal- 
 lons. 
 
 Air Venting. — Cold water contains in solution a considerable 
 quantity of air which is driven off when heated. In the case of 
 steam heating this finds its way into the radiators and passes out 
 automatically through the air valves as previously described. 
 
 The removal of air from a hot-water system is not so simple, 
 because automatic valves are not always to be depended upon, 
 and the damage from leakage, due to a sticking valve is much 
 more serious than in the case of steam. The object sought, in 
 laying out a system of piping for hot-water heating, is to pre- 
 vent the air from entering the radiators, so far as possible, and 
 thus reduce the number of air valves to a minimum. As air is 
 lighter than water it will immediately collect in the higher parts 
 of the system, and especial care should be taken to divert as 
 much of it as possible to the expansion tank, from which it will 
 pass to the atmosphere through the vent. 
 
 In the usual two-pipe system, shown in Fig. 94, a portion of 
 the air may be disposed of by connecting the expansion pipe 
 directly into the top of the main as it rises from the boiler, thus 
 utilizing it as an air vent as well as an overflow or expansion pipe. 
 
 It will be found in practice, however, that a certain amount of 
 air will find its way into the radiators, and vents, preferably of 
 the pet-cock or non-automatic type, must be provided in the top 
 of each. 
 
 In the circuit system, shown in Fig. 95, the conditions are prac- 
 tically the same as those just described and should be provided 
 for in a similar manner. The ideal arrangements for air venting 
 are those shown in Figs. 96 and 108, where a single main is 
 carried directly to the top of the building and the radiators sup- 
 plied from a downward feed. 
 
140 
 
 HEATING AND VENTILATING PLANTS 
 
 In both of these diagrams the expansion tank, is the highest 
 point, and as the radiators have top connections there are no 
 air pockets in any part of the system. 
 
 Any air which is liberated from the water rises at once to the 
 
 ^ i>i}/,^fif,^fi/f/^MfJfW/W,77777A>777. ^ 
 
 •5 
 
 ero :,M,Wi//„M,/„lt,„„„/,;,./,,,,M. V. 
 
 Fig. 100. 
 
 o 
 -o 
 
 ^ 
 
 YAlMW/M//f,^J„/MJ/i,-iJ,JJ77777: 
 
 ■,MMJy/J^M/„i>,MM,j,ij;77>T7777: 
 
 Fig. 101. 
 
 Fig. 102. 
 
 Kr 
 
 h. 
 
 WM//MMMMMMMMM^/!7^!!!r, 
 
 MM,MMMm,ymm^^^^m^^^,m^m^ 
 
 Fig. 103. 
 
 Fig. 100. Radiator Coimected with Mains Below Floor. 
 
 Fig. 101 . Connecting with Vertical Riser and Return Drop. 
 
 Fig. 102. Connecting with Radiator on an Upper Floor. 
 
 Fig. 103. Connection Used with Overhead System. 
 
 expansion tank without hindrance and passes outboard through 
 the vent pipe. 
 
 Radiator Connections. 
 
 The best method of making the radiator connections will de- 
 pend somewhat upon their location and the piping system em- 
 ployed. The connection shown in Fig. 100 is for a first-floor 
 radiator with supply and return mains at the ceiling below. 
 
 In Fig. 10,1, radiators on different floors are connected with 
 the same pair of risers. Attention should be given to the method 
 employed for strengthening the flow to the lower radiator by 
 taking the supply from the top of an offset in the riser, while the 
 
HOT-WATER BEATING BY GRAVITY CIRCULATION 141 
 
 pipe leading to the upper floor is taken from the side. The 
 method of making the connections with the upper radiator, men- 
 tioned above, are shown in Fig. 102. When the overhead feed 
 system is employed (Figs. 96 and 108), the connections are often 
 made as in Fig. 103. This arrangement does away with separate 
 return risers, and is quite extensively used on this account. One 
 objection, however, is the discharging of the cool return water 
 back into the feed pipe, thus reducing the temperature of the 
 supply to the lower floors. 
 
 Fig. 104. Sterling Indirect Radiator. 
 
 In buildings of two or three stories, this cooling effect is small 
 and may be neglected, but in the case of tall office buildings the 
 radiating surface should be increased about 5 per cent on each 
 successive floor downward. 
 
 If the connections were such that all of the water passed 
 through the radiator before reaching the floor below the cooling 
 effect would be much greater and it would be necessary to in- 
 crease the radiating surface considerably more than stated above. 
 
 As a matter of fact, only a portion of the water is by-passed 
 through the radiator, and as the supply drop is made large for 
 its work, the actual cooling is proportionately reduced. 
 
 Valves. — It is customary to place a valve in the supply con- 
 nection only, as that is sufficient to stop the circulation of water 
 through the radiator. Sometimes each riser is separately valved 
 at top and bottom and provided with a draw-off pipe and valve, 
 so that in case of leaks the riser to which the faulty radiator is 
 connected can be shut off and the radiator drained before making 
 
142 
 
 HEATING AND VENTILATING PLANTS 
 
 repairs. This arrangement should always be employed in the case 
 of large or important buildings. 
 
 Gate valves should be used in connection with hot-water piping, 
 although angle valves may be used at the radiators. Special 
 forms of both radiator and air valves have been described in 
 Chapter VI. 
 
 Pipe Fittings. — All fittings in the mains, such as elbows, tees, 
 etc., should be of the "long-turn'' pattern. If the common short 
 
 Fig. 105. Primus Indirect Radiator. 
 
 fittings are used, they should be a size larger than the pipe, bushed 
 down to the proper size. The long-turn fittings, however, are 
 preferable, and give a much better appearance. 
 
 Connections between the radiators and risers may be made with 
 the ordinary short-pattern fittings, as the other form is not well 
 adapted to the close connections necessary for this work. 
 
 Indirect Heating. 
 
 The radiators used for indirect hot-water heating are of the 
 same general form as those for steam, and in most cases are 
 interchangeable. All of the indirect radiators shown in Chapter 
 VIII. are equally adapted to hot-water heating. The essential 
 feature in any case is that there shall be a free passage for 
 the circulation of water from the top to the bottom of the section, 
 as illustrated in Figs. 104 and 105. 
 
 The Stirling indirect radiator shown in Fig. 104 contains 30 
 
HOT-WATER HEATING BY GRAVITY CIRCULATION 143 
 
 square feet of heating surface, is 37 inches in length, 16 inches 
 in height, and occupies 3^ inches in the stack. 
 
 The Primus indirect (Fig. 105) is 38 inches in length, 11 inches 
 in height. Each section occupies 3% inches in the stack, and is 
 rated at 8 square feet of heating surface. 
 
 Fig. 106. Pipe Connections to Stacks. 
 
 Hot-water radiators should be of good depth to give the best 
 results; and in general should not be much less than 15 inches, 
 unless double banks are used. 
 
 Size of Stacks. — As indirect hot water is used principally in 
 the warming of dwelling houses, and in combination with direct 
 radiation, the easiest method is to compute the surfaces required 
 for direct radiation and multiply these results by 1.5 for pin 
 radiators of good depth. For other forms the factor should 
 vary from 1.5 to 2, depending upon the depth and proportion of 
 free area for air flow between the sections. 
 
 If it is desired to calculate the required surface directly by the 
 thermal unit method, we may allow an efficiency of about ,360 
 B. T. U. for good types in zero weather. 
 
 In hospital and schoolhouse work, where larger. volumes of air 
 are warmed to lower temperatures, efficiencies of 340 B. T. U. 
 and 400 B. T. U. respectively may be allowed for radiators of 
 good form. 
 
 Flues and Casings. — ^Both the cold and warm-air flues may be 
 
144 
 
 HEATING AND VENTILATING PLANTS 
 
 computed in the same manner as for steam. This gives a some- 
 what larger flue for a given room, but as the temperature of the 
 air is less, the velocity of flow is correspondingly reduced. 
 
 The stack casings are practically the same as for steam, 
 although it is well to make the air spaces slightly larger if con- 
 venient. 
 
 Pipe Connections. — A diagram illustrating the general method 
 
 Fig. 107. Stacks Arranged in Groups. 
 
 of connecting indirect stacks with the boiler is shown in Fig. 106. 
 It is customary to take off the branches supplying the stacks from 
 a point near the basement ceiling, grade them downward, and 
 make the connection at the top, as indicated in the cut. The sys- 
 tem is air-vented through the expansion pipe, which is connected 
 into the main riser directly above the boiler, as already described 
 in connection with direct heating. 
 
 In order to obtain a uniform circulation through a stack of 
 large size it is customary to divide it into a number of sections, 
 as shown in Fig. 107, limiting the surface to 80 or 100 square 
 feet per section, and providing each with separate supply and 
 return connections. 
 
 In actual construction the main flow pipe is carried near the 
 ceiling, either above or in front of the stack, while the return 
 is run along the wall at the rear in order to obstruct the basement 
 
HOT-WATER HEATING BY GRAVITY CIRCULATION 
 
 145 
 
 space as little as possible. Valves are placed in the main supply 
 branches, as indicated, for shutting off the stack in case of re- 
 pairs. 
 
 When a building contains a considerable amount of indirect 
 radiation it is usually supplied through independent basement 
 mains when the direct system has an overhead supply, as shown 
 in Fig. 108. Small isolated stacks at some distance from the 
 
 Flow 
 
 jH ^^= M- 
 
 ■A 
 
 Kxpansion Taiik 
 
 -M- 
 
 iH-.-p=r 
 
 '.-^ 
 
 W777. y/^/z/^/.T 
 
 v.'// ^ ,• ////M//.;w/, / ■ ' /- ■^ T^ y.'T -. 'M'^/ v//^//^/^//?^ , ;^ 
 
 ^.-^ 
 
 -+H^j 
 
 3 
 
 I Heater I 
 
 lietuni 
 
 Boiler 
 
 ' lietiun ' ' 
 
 Fig. 108. Piping System for Combined Direct and Indirect Heating. 
 
 boiler, or the basement mains, may be connected with the over- 
 head system if found more convenient. Some engineers make 
 a practice of carrying all of the indirect radiation on the over- 
 head system in order to obtain a stronger circulation. This is 
 hardly necessary if the basement mains are of good size, properly 
 graded and kept free from air. 
 
 Another arrangement sometimes employed is that of carrying 
 the supply main to the second floor and then returning to the 
 basement in the form of a loop before connecting with the hori- 
 zontal mains. This has the effect of starting a circulation through 
 the system more rapidly when first warming up in the morning. 
 As soon as a portion of the water in the boiler becomes heated it 
 rises 'to the top of the loop and produces at once an tmbalanced 
 pressure due to the difference in weight of the water in the two 
 
146 
 
 HEATING AND VENTILATING PLANTS 
 
 legs of the loop. This is available for producing a flow through 
 the system and tends to start up the circulation more promptly 
 than when the discharge is directly into the basement mains. 
 After the system is in full operation the loop has very little effect 
 because the temperature in the two pipes is practically the same. 
 A small difference may be produced by covering the pipe having 
 the upward flow and leaving the other bare. 
 
 This effect may be still further increased by connecting a hall 
 
 Flow Main 
 
 Fig. 109. Apparatus Required to Replace Hot- Water Boiler. 
 
 radiator with the top of the loop and returning the cooler water 
 into the downward leg. This cools the water slightly in the latter 
 and tends to strengthen the circulation through the loop and 
 therefore throughout the entire system. 
 
 Combination Systems. 
 
 The arrangement shown in Fig. 109 is sometimes used in con- 
 nection with a steam heating plant where it is desired to obtain 
 the advantages of hot-water heating in one or more rooms, as in 
 the ofifices of a manufacturing plant. It often happens that an 
 institution is increased in size by adding new buildings from time 
 to time, each having its independent hot-water heating system. 
 Plants of this kind are difficult to care for when a certain limit is 
 reached, arid may be simplified by removing the various hot-water 
 boilers, substituting coil heaters, and installing a central steam 
 
HOT-WATER HEATING BY GRAVITY CIRCULATION 147 
 
 plant for doing the entire heating. Sometimes new plants are 
 installed on this principle where the buildings are so scattered as 
 to make gravity circulation from a central plant impracticable and 
 where ^ system of forced circulation is objected to. The appar- 
 atus required to replace the hot-water boiler in each building 
 consists of a closed tank containing a steam coil of suiificient size 
 to heat the water for warming purposes. Steam is commonly 
 carried to the buildings under a comparatively high pressure 
 and reduced at each heater in order to reduce the size of mains, 
 although it is often found more desirable to reduce it in the boiler 
 room and carry a uniform pressure in the entire system of steam 
 mains. This will depend upon various local conditions, such as 
 the steam pressures required for other purposes, as sterilizing, 
 cooking, laundry and power purposes. The condensation from 
 the coil flows into a trap which discharges into a main return 
 leading to a vented receiver in the boiler room. The trap should 
 be provided with a by-pass and drain connection, as shown. The 
 flow main supplying the radiators is taken from the top of the 
 tank and the return is brought into the bottom at the opposite 
 end, as shown, with provision for draining the tank and entire 
 heating system to the sewer, if desired. An expansion pipe, with- 
 out valve, connects the heating tank with the expansion tank as 
 indicated. 
 
 Assuming the average temperature of the water passing through 
 the heater as 170°, each square foot of coil surface will supply 
 about 40 square feet of direct radiation for a steam pressure of 
 5 pounds; 50 square feet for a pressure of 10 pounds; and 60 
 square feet for a pressure of 20 pounds. By using a heater in 
 which the water passes through tubes surrounded by steam the 
 above ratios may be increased from 30 to 30 per cent depending 
 upon the velocity of flow. 
 
 Calculation of Pipe Sizes. 
 
 It has already been shown that the velocity of flow through the 
 pipes of a hot-water heating system is dependent upon the dif- 
 ference in temperature of the water in the supply and return 
 mains, and upon the height of the radiation above the boiler. 
 
 If these quantities are known, the "pressure head" for pro- 
 
148 
 
 HEATING AND VENTILATING PLANTS 
 
 ducing. flow may be found by the following equation, from Chap- 
 ter I, 
 
 H = T X hX 0.000367, 
 in which 
 
 H = pressure head, in feet. 
 
 T = difference in temperature between supply and return. 
 h = height of radiation above the boiler, in feet. 
 Table XXXIV. gives the pressure or friction heads required to 
 
 Table XXXIV. 
 Pressure Heads for Flow Through Hot- Water Pipes. 
 
 ? 
 
 Gallons per minute 
 
 S.S"" 
 
 5 10 15 1 20 30 40 60 1 60 80 
 
 100 1 120 140 160 1 180 200 250 300 350 400 500 
 
 
 
 o^s-s 
 
 Friction loss in feet head per 100 feet length of pipe 
 
 4 
 
 .005 
 .003 
 
 .011 
 .005 
 
 .020 
 .009 
 
 .031 
 .013 
 
 .07 
 .025 
 
 .12 
 .04 
 
 .19 
 .OB 
 
 .26 
 
 .47 
 .15 
 
 .76 
 .23 
 
 i.or 
 
 .34 
 
 
 
 
 
 
 
 
 
 
 5 
 
 .47 
 
 .60 
 
 .77 
 
 .i:5 
 
 
 
 
 
 
 6 
 
 
 .OIB 
 
 .(KI4 
 
 .(KHi 
 
 .01(1 
 
 .OIK 
 
 .023 
 
 .032 
 
 .058 
 
 .085 
 
 .13 
 
 .18 
 
 .24 
 
 .») 
 
 .37 
 
 ..58 
 
 .83 
 
 
 
 
 
 
 
 .002 
 
 .003 
 
 .006 
 
 .008 
 
 .012 
 
 .016 
 
 .027 
 
 .043 
 
 .061 
 
 .(18.S 
 
 .11 
 
 .14 
 
 .17 
 
 .26 
 
 .38 
 
 .51 
 
 .67 
 
 1.05 
 
 8 
 
 
 
 
 .(m 
 
 .(XM 
 
 .005 
 
 .(XI7 
 
 Am 
 
 .015 
 
 .022 
 
 Am 
 
 Am 
 
 .054 
 
 .069 
 
 .085 
 
 .13 
 
 .19 
 
 .26 
 
 .-M 
 
 ..53 
 
 9 
 
 
 
 
 
 
 .002 
 
 .003 
 
 .004 
 
 .005 
 
 .(108 
 
 .012 
 
 .015 
 
 .023 
 
 .0.30 
 
 .(118 
 
 .047 
 
 .073 
 
 .10 
 
 .14 
 
 .18 
 
 .29 
 
 10 
 
 
 
 
 
 
 .002 
 
 .003 
 
 .004 
 
 .005 
 
 .008 
 
 .010 
 
 .014 
 
 .018 
 
 .0?2 
 
 .027 
 
 .043 
 
 .061 
 
 .083 
 
 .110 
 
 .17 
 
 produce a given flow in gallons per minute through pipes of dif- 
 ferent diameters, 100 feet in length, and is to be used in connec- 
 tion with the formula. 
 
 Example 1. — A group of hot-water radiators is located 50 ft. 
 above the boiler ; it is desired to supply them with 120 gallons of 
 water per minute. Allowing for a drop in temperature of 30°, 
 what will be the required size of the supply and return risers? 
 
 H = 20 X 50 X 0.000,367 = 0.367 ft. 
 As the supply and return risers are each 50 ft. in height, the 
 total length of run is 100 ft., which corresponds with Table 
 XXXIV. 
 
 Following down the column for 120 gallons we find that a 5-in. 
 pipe will discharge this quantity of water with a head of Oj34 ft. 
 and is the size required. 
 
 Example 2. — What size of main and riser will be required to 
 supply 3,000 sq. ft. of direct radiation, allowing a drop in tem- 
 perature of 10° ? The radiation is on the third floor of a building. 
 
HOT-WATER HEATING BY GRAVITY CIRCULATION 
 
 149 
 
 m 
 
 "I 100 I , 
 
 ^^^ ''^^^" ■/^^i'^^^ft 
 
 
 1 
 
 
 40 ft. above the boiler, and the horizontal run to the foot 
 of the riser is 60 ft. 
 
 3,000 X 170 (efficiency of radiators) = 5.10,000 B. T. U. per 
 hour, or 8,500 B. T. U. required per minute. One pound of 
 water cooled 10° gives off 10 B. T. U., or one gallon will give 
 off 10 X S.3 = 83 B. T. U. under the same conditions. There- 
 fore, 8,500 -T- 83 = 102 gallons of water 
 I must be supplied to the radiators per 
 
 minute. 
 
 The available head for producing flow 
 is 10 X 40 X 0.000367 = 0.147 ft. The 
 total length of the supply and return 
 mains and risers, neglecting the branchesi 
 is 200 ft. The friction heads in Table 
 XXXIV. are for 100 ft., so in this case 
 we must look for a pipe which will dis- 
 charge the given volume of water with 
 a head equal to 0.147 ^ 2 = 0.074 ft. 
 Calling the quantity 100 gallons, and 
 looking in the table, we find that a 6-in. 
 pipe will discharge this quantity of 
 water with a head of 0.085 ft., while a 
 7-in. pipe requires only 0.043. Prob- 
 ably the larger size would be used, es- 
 pecially if there were a number of bends in the line. 
 
 Average Elevation of Radiation. — In the preceding examples 
 it has been assumed that the radiation was all on one floor. In 
 tall buildings this of course is not the case, and the average ele- 
 vation of the entire system must first be found. If each floor has 
 approximately the same amount of radiation it may be assumed 
 that it is all located upon the middle floor, but if the amount 
 varies on the different floors to a considerable extent we must 
 multiply the square feet of radiation on each floor by its height 
 above the boiler, and divide the sum of these products by the 
 total radiation in the building. 
 
 1 
 
 Fig. 1 10. 
 
150 
 
 HEATING AND VENTILATING PLANTS 
 
 For example, the average elevation of the system shown in 
 Fig. 110 is 
 
 (100 X-30) + (50 X 20) + 085 X 10) _ „, .. 
 100 + 50+25 -~"^^ ^^^^• 
 
 The methods above described are especially for computing the 
 size of the main riser for systems having an overhead distribu- 
 tion, or for the main supplying a whole building. As this process 
 would be too cumbersome to. apply to the various branches and 
 
 Table XXXV. 
 Sizes of Direct Hot-Water Heating Mains. 
 
 Size of pipe, 
 
 Square £eet of radiating surface 
 
 
 
 
 
 
 
 
 
 
 inches 
 
 100 ft. 
 
 800 it. 
 
 300 ft. 
 
 400 ft. 
 
 500 ft. 
 
 600 ft. 
 
 700 ft. 
 
 800 ft 
 
 1000ft. 
 
 
 run 
 
 run 
 
 run 
 
 ruu 
 
 run 
 
 run 
 
 run 
 
 run 
 
 run 
 
 1 
 
 30 
 
 
 
 
 
 
 
 
 
 it 
 
 60 
 
 50 
 
 
 
 
 
 
 
 
 100 
 
 75 
 
 50 
 
 
 
 
 
 
 
 3 
 
 800 
 
 150 
 
 185 
 
 100 
 
 75 
 
 
 
 
 
 8i 
 
 350 
 
 850 
 
 800 
 
 175 
 
 ISO 
 
 185 
 
 
 
 
 3 
 
 550 
 
 400 
 
 300 
 
 8r5 
 
 850 
 
 885 
 
 800 
 
 175 
 
 150 
 
 31 
 
 850 
 
 60O 
 
 450 
 
 400 
 
 350 
 
 386 
 
 300 
 
 250 
 
 885 
 
 4 
 
 1800 
 
 850 
 
 700 
 
 600 
 
 585 
 
 475 
 
 450 
 
 400 
 
 350 
 
 5 
 
 
 1400 
 
 1150 
 
 1000 
 
 700 
 
 850 
 
 775 
 
 785 
 
 650 
 
 .. 6 . 
 
 
 
 
 1600 
 
 1400 
 
 1300 
 
 1800 
 
 1150 
 
 1000 
 
 .! ;7,i i 
 
 
 
 
 
 
 
 1706 
 
 1600 
 
 1500 
 
 
 
 
 
 
 
 
 
 Table XXXVI. 
 Sizes of Direct Hot-Water Heating Risers. 
 
 Size of 
 
 Square feet of radiating surface 
 
 
 
 
 
 
 
 inches. 
 
 1st story 
 
 2d story 
 
 3d story 
 
 4th story 
 
 5th story 6th story 
 
 1 
 
 30 
 
 55 
 
 65 
 
 75 
 
 85 
 
 95 
 
 IJ 
 
 60 
 
 90 
 
 110 
 
 125 
 
 140 
 
 160 
 
 if ■ 
 
 100 
 
 140 
 
 165 
 
 185 
 
 210 
 
 840 
 
 2 
 
 200 
 
 875 
 
 375 
 
 425 
 
 500 
 
 
 2J 
 
 350 
 
 475 
 
 
 
 
 
 3 
 
 550 
 
 
 
 
 
 
 35 
 
 850 
 
 
 
 
 
 
 risers in a building, the accompanying tables are given for ready 
 use. These are based on the square feet of radiation to be sup- 
 plied, and apply to the average conditions found in actual prac- 
 tice. 
 
 Pipe Sizes for Direct Radiation. — Table XXXV. is for deter- 
 mining the sizes of the horizontal mains and branches, and gives 
 
HOT-WATER HEATING BY GRAVITY CIRCULATION 
 
 151 
 
 the square feet of radiation which may be supplied by pipes of 
 different sizes for runs of 100 to 1,000 feet. 
 
 Table XXXVI. gives the sizes of risers and the square feet of 
 radiation which they will supply on the different floors of a build- 
 ing. 
 
 They are computed by the same general method given above, 
 with a certain allowance for bends and other obstructions. 
 
 Pipe Sizes for Indirect Radiation. — It is evident that the diam- 
 eter of supply and return pipes must be considerably larger in the 
 case of indirect heating than for direct, because of the lower 
 elevation of the stacks and the higher efficiency of the radiating 
 surface. 
 
 The general method of computing the size of mains is the same 
 as for direct radiation. 
 
 Table XXXVII. 
 Sizes of Indirect Hot-Water Heating Mains. 
 
 Diameter of 
 
 Square feet of radiating surface 
 
 
 
 
 pipe, inches 
 
 100 feet 
 
 200 feet 
 
 300 feet 
 
 400 feet 
 
 
 run 
 
 run 
 
 run 
 
 run 
 
 1 
 
 15 
 
 
 
 
 U 
 
 30 
 
 25 
 
 
 
 n 
 
 60 
 
 40 
 
 25 
 
 
 2 
 
 100 
 
 75 
 
 60 
 
 50 
 
 8J 
 
 175 
 
 125 
 
 100 
 
 90 
 
 3 
 
 275 
 
 200 
 
 150 
 
 140 
 
 3h 
 
 425 
 
 300 
 
 325 
 
 200 
 
 4 
 
 600 
 
 425 
 
 350 
 
 300 
 
 5 
 
 
 700 
 
 575 
 
 500 
 
 6 
 
 
 
 
 800 
 
 r 
 
 
 
 
 1200 
 
 
 
 
 
 
 In this case it is safe to assume a drop in temperature of about 
 20° between the supply and return. The elevation may be taken 
 as approximately the distance from the grate of the boiler to the 
 center of the stacks. 
 
 Table XXXVIL, prepared by the methods previously given, 
 will be found sufficiently accurate for all ordinary conditions of 
 indirect heating. 
 
152 HEATING AND VENTILATING PLANTS 
 
 Boilers and Connections. 
 
 What has already been said in regard to steam boilers applies 
 equally well to those employed for hot-water heating, and the 
 method of computing the capacity is practically the same. 
 
 The supply and return connections for a single boiler are very 
 simple. One or more flow mains are taken from the top, depend- 
 ing upon the type of boiler, and corresponding returns are 
 brought back to the openings near the bottom. Neither gauge 
 glass, cocks, nor check valves are used in connection with a hot- 
 water boiler. 
 
 When two boilers are connected in a battery it becomes neces- 
 sary to place valves in the expansion pipes unless a separate tank 
 is provided for each boiler. If valves are used,- each boiler should 
 be furnished with a relief or safety valve as a safeguard against 
 explosion in case the fires should be started up before opening 
 the valves in the expansion pipes. The safer way is to use two 
 tanks, although more expensive. If the system is in charge of a 
 careful attendant, a relief-valve gives sufficient protection, and is 
 the arrangement commonly used. 
 
 Testing Steam and Hot-Water Heating Systems. 
 
 Guarantees are frequently called for stating that a plant shall 
 be of sufficient capacity to maintain an inside temperature of 70° 
 at a given minimum outside temperature, and with a stated steam 
 pressure or water temperature in the radiators. While tests 
 should be made under conditions approximating those stated in 
 the guarantee, it is not always possible to get the exact combina- 
 tion called for. 
 
 When an inside temperature of 70° is specified, with zero con- 
 ditions outside, and it is necessary to make the test at a some- 
 what higher outside temperature, the nezv inside temperature to 
 be maintained to give the same plant capacity may be obtained 
 by use of the following factors. These, however, require the 
 test to be made with steam at the same pressure, or water at the 
 same temperature, called for in the specifications. 
 
 The factors for steam heating are as follows, for different 
 pressures : 1 pound, 0.'675 ; 3 pounds, 0.678 ; 5 pounds, 0.'69i3. 
 
 For hot-water heating, the factors vary with the temperature 
 
HOT-WATER HEATING BY GRAVITY CIRCULATION 153 
 
 of the water circulated, and are as follows: 160 degrees, 0.561; 
 170 degrees, 0.588 ; 180 degrees, 0.611. 
 
 In making use of these factors, the following formula is em- 
 ployed : 
 
 f = 70+ (r X -F) in which, 
 t = the inside temperature to be maintained during the test 
 
 T = outside temperature during test 
 
 F — factor for the given steam pressure or water temperature 
 
 Example. — A guarantee calls for an inside temperature of 70° 
 with zero conditions outside, and a steam pressure of 2 pounds 
 on the system. 
 
 The final test is to be made when it is +50° outside; what 
 inside temperature must be maintained to denote the same ca- 
 pacity of plant? 
 
 Substituting in the formula we have 
 
 f = 70 + (20 X 0.678) = 83.5 deg. 
 
CHAPTER X. 
 HOT-WATER HEATING BY FORCED CIRCULATION. 
 
 While the gravity system of hot-water heating is well adapted 
 to .buildings of small and medium size, there is a limit to which it 
 can be carried economically. This is due to the slow movement 
 of the water which calls for pipes of excessive size. To over- 
 come this difficulty pumps are used to force the water through 
 the mains at a comparatively high velocity. 
 
 The water may be heated in a boiler in the same manner as 
 for gravity circulation, or exhaust steam may be utilized in a 
 feed-water heater of large size, supplemented by live steam if 
 necessary. 
 
 Sometimes part of the heat is derived from an economizer 
 placed in the smoke passage from the boilers, as described in a 
 previous chapter. 
 
 Piping. 
 
 Systems of Piping. — The mains for forced circulation are 
 usually run in one of two ways. In the two-pipe system shown 
 in Fig. Ill the supply and return are carried side -by side, the 
 former reducing in size and the latter increasing as the branches 
 are taken off. 
 
 The flow through the risers is produced by the difference in 
 pressure in the supply and return mains, hence, care must be 
 taken in arranging the piping to equalize the resistance as much 
 as possible in order to prevent short circuiting and to secure an 
 even distribution through all parts of the system. Sometimes it 
 is necessary to supplement this by the use of throttling valves in 
 some of the branches. 
 
 Fig. 113 shows the single-pipe or circuit system. This is simi- 
 lar to the one already described for gravity circulation, except it 
 can be used on a much larger scale. 
 
 A single main is carried entirely around the building in this 
 case, the ends being connected with the suction and discharge 
 of the pump as shown. 
 
 154 
 
HOT-WATER HEATING BY FORCED CIRCULATION 
 
 155 
 
 In some of the latest systems of forced hot-water heating the 
 supply mains have been combined with the sprinkler system, thus 
 reducing the amount of extra piping and radiation and also the 
 cost of installation. 
 
 Head Necessary for Circulation. — As the pressure or head in 
 the main drops constantly throughout the circuit, from the dis- 
 charge of the pump back to the suction, it is evident that if a 
 supply riser be taken off at any point and the return be con- 
 
 
 Badiator 
 
 \\ Flow" 
 
 1 Expansion 
 J Tank 
 
 Badiator 
 
 BadiatOT 
 
 irm ' 
 
 Pump ( 6 
 
 wmM 
 
 — *e= — 
 Eeturn 
 
 rio\y ]t 
 
 Heater 
 
 Eeturn 
 
 Fig. III. Two-Pipe System for Forced Hot- Water Heating. 
 
 nected into the main a short distance along the line, there will be 
 a sufficient difference in pressure between the two points to pro- 
 duce a circulation through these pipes and the connecting radia- 
 tors. The distance required between the supply and return con- 
 nections to produce a given head can be computed in any case if 
 the total drop in pressure is known between the discharge and 
 suction of the pump. As this drop is practically uniform through- 
 out the entire circuit, the drop per foot in length can be com- 
 puted by dividing the total drop by the length of the circuit, 
 and knowing this, the required distance between the connections 
 can be easily determined by the methods already described for 
 gravity circulation. Usually, however, 6 or 8 feet is ample to 
 produce the necessary circulation, and even less if the supply is 
 
156 
 
 HEATING AND VENTILATING PLANTS 
 
 taken from the top of the main and the return connected mto 
 the side. 
 
 Sizes of Mains and Branches. — As the velocity of flow is inde- 
 pendent of the temperature and elevation when a pump is used, 
 it is only necessary to consider the volume of water to be moved 
 and the length of run. 
 
 The volume is found by th& equation 
 
 Q= 
 
 RXE 
 
 500xr 
 
 I _ 
 
 f Expansion 
 Tank 
 
 6 iPiunp 
 
 Fig. 1 12. Circuit System for Forced Hot- Water Heating. 
 
 in which 
 ,Q= gallons of water required per minute. 
 2?= square feet of radiating surface to be supplied. 
 jE= efficiency of radiating surface in B. T. U. per square foot per 
 
 hoiur. 
 r=drop in temperature of the water in passing through the heat- 
 ing system, commonly taken as .30°. 
 
 Velocity of Flow. — Having determined the gallons of water to 
 be moved, the required size of main can be found by assuming 
 the velocity of flow, which for pipes from 5 to 8 inches in diam- 
 eter may be taken at 400 to 500 feet per minute. A velocity as 
 high as 600 feet is sometimes allowed for pipes of large size, while 
 the velocity in thgse of smaller diameter should be proportionately 
 reduced to 250 or 300 feet for a 3-inch pipe. The next step is to 
 
HOT-WATER HEATING BY FORCED CIRCULATION 157 
 
 find the pressure or head necessary to force the water through 
 the main at the given velocity. This in general should not exceed 
 40 or 50 feet, and better efficiencies will be obtained with heads 
 not exceeding 30 or 35 feet with the usual form of centrift^al 
 pump. 
 
 Loss Through Friction. — As the water in a heating system is 
 under a state of equilibrium, the only power necessary to produce 
 a circulation is that required to overcome the friction in the pipes 
 
 Table XXXVIII. 
 Comparative Loss of Head in Fittings and Straight Pipe. 
 
 Number of feet of clean, 
 T^, - ^..i. straight pipe of same 
 
 Name of flttmg ^j^^ ^Ij^jj ^oai^ cause 
 
 the same loss as fitting 
 
 6-inch Pratt & Cady check valve 50 
 
 6-inch Walworth globe check valve. 200 
 
 4-inch Pratt & Cady check valve 25 
 
 4- inch Walworth globe check valve. 130 
 
 2J-inch to 8-inch long-turn ells 4 
 
 gi-inch to 8-inch short turn ells 9 
 
 .3-mch to 8-inch long-turn tees 9 
 
 3-inch to 8-inch short-turn tees 17 
 
 Uh bend 5 
 
 and radiators, affd as the area of the passageways through the 
 latter is usually large in comparison with the former, it is cus- 
 tomary to consider only the head necessary to force the water 
 through the mains, taking into consideration the additional fric- 
 tion produced by valves and fittings. 
 
 Table XXXVIII., taken from the catalogue of the Lawrence 
 Machine Company, gives the loss of hea,d produced by different 
 fittings, this loss being expressed in the additional length of pipe 
 which must be added to the length of the main. 
 
 Table XXXIX. is prepared especially for determining the size 
 of mains for different conditions, an.d is used as follows : 
 
 Example. — A heating system requires the circulation of 4-80 
 gallons of water per minute through a circuit main 600 ft. in 
 length. The pipe contains 12 long- turn elbows and 1 Pratt & 
 Cady check valve. What diameter of main should be used? 
 • Assuming a velocity of 480 ft. per minute as a trial velocity, 
 we follow along the line corresponding to this velocity and find 
 that a 5-in. pipe will deliver the required volume of water under 
 a head of 4.9 ft. for each 100 ft. length of run. 
 
158 
 
 HEATING AND VENTILATING PLANTS 
 
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HOT-WATER HEATING BY FORCED CIRCULATION 159 
 
 The actual length of the main, including the equivalent of the 
 fittings as additional length, is 600 + (15 X 9) + 50 = 75S feet, 
 hence the total head required is 4.9 X 7.58 = 37 ft. As both 
 the assumed velocity and the necessary head come within prac- 
 tical limits, this is the size of pipe which would probably be used. 
 If it was desired to reduce the power for running the pump, the 
 size of main could be increased. That is-. Table XXXIX. shows 
 that a 6-in. pipe would deliver the same volume of water with a 
 
 Fig. 1 13. Fig. 1 14. 
 
 Runners for Centrifugal Pumps. 
 
 friction head of only about 2 ft. per 100 ft. in length, or a total 
 head of 3 X 7.58 = 15 ft. 
 
 The risers in the circuit system are usually made the same size 
 as for gravity work. With double mains as shown in Fig. Ill 
 they may be somewhat smaller, a reduction of one size for diam- 
 eters over 13^ inches being common. 
 
 The branches connecting the risers with the mains may be 
 proportioned from the combined areas of the risers, using Table 
 XX. for this purpose. When the branches are of considerable 
 size, the diameter may be computed from the available head and 
 voluine of water to be moved. 
 
 Centrifugal Pumps. 
 
 Principle of Operation. — Centrifugal pumps are usually em- 
 ployed in connection with forced hot-water circulation in prefer- 
 ence to the piston or plunger type. They are simple in construe- 
 
160 
 
 BEATING AND VENTILATING PLANTS 
 
 tion, having no valves, produce a continuous flow of water, and, 
 for the low heads against which they are operated, have a fair 
 efficiency. These pumps are similar in principle and operation 
 to the centrifugal fans described in Chapter XIII. 
 
 They consist primarily of a wheel or impeller of two or more 
 curved blades attached to a shaft, and revolving in a case or shell 
 so arranged that the inlet is at the center of the wheel and the 
 
 Table XL. 
 
 Capacities, Speeds and Horse Powers of Centrifugal Pumps of Various 
 Sizes for Friction Heads from 16 to 90 Feet. 
 
 I 
 
 1a- 
 
 Friction head in feet and revolutions per minute 
 
 ■s . 
 
 || 
 
 SI 
 
 
 
 .a.s~ 
 p 
 
 °4 
 
 
 16 ft. 
 
 20 ft. 
 
 25 ft. 
 
 30 ft. 
 
 35 ft. 
 
 40 ft. 
 
 50 ft. 
 
 60 ft. 
 
 70 ft. 
 
 80 ft. 
 
 90 ft. 
 
 U9 |1}(M 
 
 2 
 
 100 
 
 460 
 
 510 
 
 570 
 
 620 
 
 670 
 
 710 
 
 795 
 
 870 
 
 940 
 
 1000 
 
 1060 
 
 18 
 
 0.06:3 
 
 8 
 
 842 
 
 380 
 
 420 
 
 470 
 
 510 
 
 550 
 
 680 
 
 645 
 
 700 
 
 750 
 
 800 
 
 850 
 
 88 
 
 0.136 
 
 4 
 
 430 
 
 310 
 
 340 
 
 370 
 
 405 
 
 435 
 
 465 
 
 515 
 
 560 
 
 600 
 
 640 
 
 670 
 
 26 
 
 0.817 
 
 5 
 
 734 
 
 879 
 
 295 
 
 320 
 
 350 
 
 370 
 
 400 
 
 435 
 
 470 
 
 510 
 
 545 
 
 570 
 
 89 
 
 0.309 
 
 6 
 
 1050 
 
 240 
 
 865 
 
 890 
 
 880 
 
 840 
 
 360 
 
 395 
 
 485 
 
 465 
 
 490 
 
 520 
 
 32 
 
 0.446 
 
 7 
 
 1439 
 
 880 
 
 850 
 
 275 
 
 800 
 
 820 
 
 340 
 
 375 
 
 405 
 
 435 
 
 465 
 
 490 
 
 34 
 
 0.606 
 
 ' 
 
 1880 
 
 210 
 
 835 
 
 260 
 
 280 
 
 800 
 
 320 
 
 355 
 
 390 
 
 415 
 
 440 
 
 465 
 
 36 
 
 0.791 
 
 delivery tangent to the circle described by the outer ends of the 
 blades. 
 
 The pressure produced by the pump is due to the centrifugal 
 force imparted to the water as it is thrown from the tips of the 
 revolving blades into the surrounding scroll or casing. With 
 low heads and high speeds the water is discharged with but little 
 rotary motion, when the blades are of the proper form. This 
 condition is desirable, as the power used in producing this mo- 
 tion is lost, so far as doing useful work is concerned. 
 
 Design and Construction. — The passages through the pump 
 should be so designed as to produce a gradually increasing ve- 
 locity of the water until it reaches the circumference of the 
 wheel, then a gradually decreasing velocity until it is discharged 
 
HOT-WATER HEATING BY FORCED CIRCULATION 
 
 161 
 
 Table XLI. 
 
 Capacities, Speeds and Horse Powers of Centrifugal Pumps of Various 
 Sizes for Friction Heads from 6 to 60 Feet. 
 
 t^ 
 
 .■s-9 
 
 
 
 ^-+j 
 
 SI 
 
 Rated quant 
 of discharge 
 gallons per 
 minute 
 
 Friction head in feet and revolutions per minute 
 
 3-^ 
 
 1^ 
 
 •S.S 
 
 6 ft. 
 
 8 ft. 
 
 12 ft. 
 
 16 ft. 
 
 20 ft. 
 
 26 ft. 
 
 80 ft. 
 
 35 ft. 
 
 40 ft. 
 
 60 ft. 
 
 60 ft. 
 
 
 2 
 
 100 
 
 440 
 
 500 
 
 595 
 
 700 
 
 780 
 
 860 
 
 945 
 
 1020 
 
 1090 
 
 1210 
 
 1820 
 
 12. 
 
 0.063 
 
 3 
 
 243 
 
 430 
 
 470 
 
 565 
 
 640 
 
 710 
 
 780 
 
 850 
 
 910 
 
 970 
 
 1080 
 
 1180 
 
 13 
 
 0.136 
 
 4 
 
 480 
 
 380 
 
 430 
 
 510 
 
 580 
 
 640 
 
 705 
 
 765 
 
 820 
 
 870 
 
 960 
 
 1040 
 
 14 
 
 0.217 
 
 5 
 
 V34 
 
 825 
 
 860 
 
 480 
 
 436 
 
 680 
 
 686 
 
 036 
 
 676 
 
 720 
 
 800 
 
 860 
 
 16 
 
 0.809 
 
 6 
 
 1058 
 
 295 
 
 330 
 
 385 
 
 400 
 
 480 
 
 530 
 
 570 
 
 610 
 
 650 
 
 715 
 
 770 
 
 18 
 
 0.446 
 
 r 
 
 1439 
 
 350 
 
 280 
 
 330 
 
 370 
 
 406 
 
 450 
 
 485 
 
 620 
 
 550 
 
 606 
 
 665 
 
 21 
 
 0.606 
 
 8 
 
 1880 
 
 216 
 
 230 
 
 286 
 
 826 
 
 856 
 
 890 
 
 420 
 
 450 
 
 480 
 
 630 
 
 575 
 
 24 
 
 0.791 
 
 Table XLII. 
 
 Capacities, Speeds and Horse Powers of Centrifugal Pumps of Various 
 Sizes for Friction Heads from 4 to 40 Feet. 
 
 'O'g 
 
 Rated quantity 
 of discharge in 
 gallons per 
 minute 
 
 Friction head in feet and revolutions per minute 
 
 . 
 
 ^**j 
 
 n 
 
 ■3.3 
 
 4 ft. 
 
 6 ft. 
 
 8 ft. 
 
 10 ft. 
 
 12 ft. 
 
 16 ft. 
 
 20 ft. 
 
 25 ft. 
 
 30 ft. 
 
 35 ft. 
 
 40 ft. 
 
 ^H»w O 
 
 2 
 
 100 
 
 570 
 
 690 
 
 790 
 
 860 
 
 930 
 
 1060 
 
 1190 
 
 1310 
 
 1480 
 
 1535 
 
 1635 
 
 8 
 
 0.063 
 
 8 
 
 242 
 
 600 
 
 600 
 
 680 
 
 746 
 
 810 
 
 920 
 
 1020 
 
 1130 
 
 1220 
 
 1320 
 
 1400 
 
 9 
 
 0.136 
 
 4 
 
 430 
 
 440 
 
 610 
 
 680 
 
 646 
 
 695 
 
 790 
 
 876 
 
 970 
 
 1060 
 
 1130 
 
 1195 
 
 10 
 
 0.217 
 
 5 
 
 734 
 
 370 
 
 430 
 
 525 
 
 670 
 
 615 
 
 690 
 
 765 
 
 840 
 
 910 
 
 970 
 
 1080 
 
 11 , 
 
 0.309 
 
 6 
 
 1068 
 
 330 
 
 430 
 
 480 
 
 530 
 
 570 
 
 650 
 
 710 
 
 780 
 
 845 
 
 906 
 
 960 
 
 12 
 
 0.446 
 
 7 
 
 1439 
 
 320 
 
 370 
 
 420 
 
 460 
 
 490 
 
 650 
 
 605 
 
 670 
 
 720 
 
 775 
 
 820 
 
 14 
 
 0.606 
 
 8 
 
 1880 
 
 280 
 
 320 
 
 860 
 
 395 
 
 425 
 
 480 
 
 626 
 
 680 
 
 630 
 
 675 
 
 715 
 
 16 
 
 0.791 
 
162 
 
 HEATING AND VENTILATING PLANTS 
 
 from the pipe. These conditions are met by having a conical 
 end to the suction pipe and a spiral casing surrounding the wheel. 
 The form of the casing should be such that the water flowing 
 around it will move with the same velocity as that issuing from 
 the blades of the wheel, then enlarging into the discharge pipe 
 through a conical mouthpiece. 
 
 Fig. 113 shows the form of wheel or impeller commonly used 
 in pumps of small size, and Fig. 114 the hollow-arm type, em- 
 
 Fig. 1 15. Lawrence Centrifugal Pump. 
 
 ployed in those of larger size. The latter has the advantage that 
 the water is thrown outward without any churning motion, and 
 also that there are no dead spaces within the casing. 
 
 Efficiency and Horse Power. — Under ordinary conditions the 
 eiificiency of a centrifugal pump falls off considerably for heads 
 above 30 or 35 feet, but multiple-stage pumps are constructed 
 which work with a good efficiency against 1,000 feet or more. 
 
 Under favorable conditions an efficiency of 60 to 70 per cent is 
 often obtained, but for hot-water circulation it is more common 
 to assume an efficiency of about 50 per cent for the average case. 
 
HOT-WATER HEATING BY FORCED CIRCULATION 
 
 163 
 
 The horse power required for driving a pump is given by the 
 formula : 
 
 H. P.= 
 
 gXFX 8.3 
 33,000X£ 
 
 in which 
 
 ff= friction head in feet. 
 
 F= gallons of water delivered per minute. 
 
 £=efl5ciency of pump. 
 
 Fig. 116. DeLavel Centriiugal Pump. 
 
 Centrifugal pumps are made in many sizes and with varying 
 proportions to meet the different requirements of capacity and 
 head. 
 
 Tables XL., XLI. and XLII. give the capacity, speed and horse 
 power for some of the smaller sizes of the Lawrence pump. 
 
 Fig. 115 shows one of these pumps driven by a direct-connected 
 engine. 
 
 When the conditions call for a higher speed than can well be 
 maintained with a reciprocating engine, a steam turbine or elec- 
 tric motor may be employed. Such an outfit is shown in Fig. 
 
164 
 
 HEATING AND VENTILATING PLANTS 
 
 116, which represents one of the De Laval centrifugal pumps 
 with direct-connected motor. 
 
 Example. — A heating system requires the circulation of 430 
 gallons of water per minute against a friction head of 30 ft. 
 What will be the required size of pump? Also the speed and 
 horse power? 
 
 Looking in Table XL. we find that a pump with a 4-in dis- 
 charge and a g'G-in. impeller will deliver the required volume of 
 water. In order to overcome a friction head of 30 ft. the pump 
 
 Fig. 117. Baffle Plates. 
 
 must run at a speed of 405 revolutions per minute, and requires 
 0.217 horse power per foot head pumped against, or a total of 30 
 X 0.217 = 6.5 horse power. 
 
 Should it be desired to use a turbine or electric motor at a 
 higher speed, we find from Table XLIL that the same results will 
 be produced by a 4-in. pump having a 10-in. impeller running 
 at a speed of 1,050 revolutions per minute. 
 
 Heaters. 
 
 If the water is heated in a boiler, any good form may be used 
 the same as for gravity work. In case tubular boilers are em- 
 ployed the entire shell may be filled with tubes, as no steam space 
 is required. 
 
 In order to prevent the water from passing in a direct line 
 from the inlet to the outlet, a series of baffle plates should be used 
 to bring it in contact with all parts of the heating surface, as 
 shown in Fig. 117. Although this method of heating the water 
 may be advisable in some cases it is usually better, especially in 
 new plants, to install steam boilers and special heaters as de- 
 scribed below. 
 
HOT-WATER HEATING BY FORCED CIRCULATION 185 
 
 When steam is used for heating the water, tubular heat- 
 ers are employed similar to closed feed-water heaters. These 
 are usually designed to have the water flow through the tubes, 
 with the steam on the outside, as a higher efifiiciency is obtained 
 by this arrangement. A number of the standard makes of feed- 
 water heaters may be used for this purpose by equipping them 
 with nozzles of the proper size. 
 
 Heating Surface and Efficiency. — The efficiency of the tube 
 surface in a heater of this kind will vary with the material and 
 form and with the velocity of the water. 
 
 A coating of grease or scale also affects the transmission of 
 heat. For ordinary conditions an efficiency of 250 to 300 B. T. 
 U. per square foot of surface per hour per degree difference in 
 temperature between the water and steam may be assumed when 
 the water flows through the tubes. 
 
 The higher figure, however, corresponds more nearly with 
 modern practice and is used in the following examples. 
 
 It is usual to circulate the water at a somewhat higher tem- 
 perature in systems of this kind, and an initial temperature of 
 at least 200°, with a drop of ,30° in the heating system may be em- 
 ployed in computing the size of heater. If exhaust steam is used 
 at atmospheric pressure, there will be a difference of 212 — 190 
 = 22° between the average temperature of the water and the 
 steam, giving an efficiency of 300 X 2^ = 6,600 B. T. U. per 
 square foot of heating surface. 
 
 Owing to the higher temperature of the water a higher radiator 
 efficiency is also obtained. Which may be taken as 300 B. T. U. 
 instead of 170 as in gravity circulation. In case high-pressure 
 steam is used in the heater and a closed expansion tank employed, 
 the same radiator efficiency may be assumed as in steam heating. 
 
 From the above, with exhaust steam, it is evident that 6,600 
 -i- 300 = 33 square feet of direct radiating surface, or 6,600 
 -^ ,360 = 35 square feet of indirect may be supplied from each 
 square foot of tube surface. 
 
 Example. — A building having 6,600 sq. ft. of direct, and 3,000 
 sq. ft. of indirect radiation is to be warmed by hot water under 
 forced circulation. Steam at atmospheric pressure is to be used 
 for heating the water. 
 
166 HEATING AND VENTILATING PLANTS 
 
 How many square feet of tube surface should the heater con- 
 tain, and what would be its rated horse power? 
 
 6,600 -=- 33 = 200, and 2,000 -;- 25 = 80, therefore 200 + 80 
 = 280 sq. ft. are called for. 
 
 Commercial heaters are commonly built on a basis of 1/3 of a 
 square foot of heating surface per horse power, so that in the 
 above case a heater of .280 -h 1/3 = 810 rated horse power is 
 required. 
 
 Auxiliary Heater. — When the exhaust steam is not sufficient 
 for the requirements, an auxiliary live-steam heater is often used 
 in connection with it. This is better practice than turning live 
 steam into the exhaust heater at a reduced pressure, unless the 
 amount required is comparatively small. 
 
 The two heaters are usually connected into the heating main 
 in series, the exhaust heater being placed next to the pumps. 
 The efficiency of a heater using live steam is of course greater 
 than one using exhaust, owing to the higher temperature of the 
 stearri. The efficiency for any given pressure can easily be de- 
 termined by the methods already given. 
 
 In plants where it is desired to save all condensation, so far as 
 possible, the exhaust steam may be purified by passing through 
 an oil separator and live steam added to it at a reduced pressure. 
 In this case a single heater is used, and all of the condensation 
 may be returned to the boilers. 
 
 "Vacuo" Hot-Water Heating. — In the methods just described 
 the engines are run non-condensing and a steam pressure equal 
 to that of the atmosphere, or slightly above, is carried in the 
 heaters. In the "vacuo" system the engines are run condensing, 
 special heaters being used which either wholly or partly replace 
 the usual condensers. The advantage of this arrangement is the 
 production of a vacuum for the engines and turbines, while at the 
 same time the heat taken up by the cooling water is utilized in 
 warming the building instead of being wasted as with the usual 
 condensing equipment. 
 
 When the cooling effect of the radiation is not sufficient to 
 produce the required vacuum it is supplemented by a cooling 
 tower, or regular condenser which is also necessary for summer 
 use when the heating system is out of commission. 
 
 Pump and Heater Connections. — The general methods of mak- 
 
HOT-WATER HEATING BY FORCED CIRCULATION 167 
 
 ing the connections between the pumps and heaters are shown in 
 diagram in Figs. 118 and 119, the arrangement being such that 
 
 EXHAUST STEAM 
 HEATER 
 
 Fig. 118 
 
 Jixhaast Steam 
 Heater 
 
 Fig. 119. 
 Methods o{ Connecting Pumps and Heaters. 
 
 any part of the apparatus can be cut out without interfering with 
 the operation of the remainder. In the series connection, shown 
 in Fig. 119, the pumps may be run together, thus increasing the 
 
168 BEATING AND VENTILATING PLANTS 
 
 pressure head and accelerating the velocity of flow through the 
 mains above the normal, if desired. With the parallel connection 
 (Fig. 118) this is not possible. 
 
 The steam and drip connections for the heaters are the same 
 as for any feed-water heater, under similar conditions. 
 
 All fittings about the pumps and heaters should be of the long- 
 turn pattern, and sweep bends of wrought-iron pipe should be 
 used in the mains for making right-angled turns whenever pos- 
 sible. 
 
CHAPTER XI. 
 EXHAUST STEAM HEATING. 
 
 Exhaust steam is commonly used for heating in connection 
 with power plants, as in shops and factories, or in office build- 
 ings which generate their own electricity. It may be circulated 
 by carrying a low back-pressure on the engine or by attaching a 
 suction to the return pipes or radiators. 
 
 Steam after being used in an engine contains the greater part 
 of its heat, and if not condensed or used for other purposes it 
 can usually be employed for heating without affecting to any 
 great extent the power of the engine. In general, we may say 
 that it is a matter of economy to use the exhaust for heating, 
 although various factors must be considered in each case to de- 
 termine to what extent this is true. 
 
 Factors to be Considered. — The more important considerations 
 bearing upon the subject are: The relative quantities of steam 
 required for power and for heating, the length of the heating 
 season, the type of engine used, the pressure carried, and, finally, 
 whether the plant under consideration is entirely new or whether, 
 on the other hand, it involves the adapting of an old heating 
 system to a new plant. 
 
 Feed-Water Heating. — The first use to be made of the exhaust 
 steam is the heating of the feed water, as this effects a constant 
 saving both summer and winter, and can be done without ma- 
 terially increasing the back pressure on the engine. 
 
 Under ordinary conditions about one sixth of the steam sup- 
 plied to the engine can be used in this way, or more nearly one 
 fifth of the exhaust discharged from the engine. 
 
 We may assume in average practice that about 80 per cent of 
 the steam supplied to an engine is discharged in the form of 
 steam at a lower pressure, the remaining 30 per cent being partly 
 converted into work and partly lost through cylinder condensa- 
 tion. 
 
 169 
 
170 . HEATING AND VENTILATING PLANTS 
 
 The latent heat in a pound of steam at atmospheric pressure is 
 966 B. T. U. ; therefore, out of each pound of live steam fur- 
 nished to the engine there will be 966 X 0.8 = 773 heat units 
 available for heating purposes. It requires practically 310 — 50 
 = 160 heat units to raise 1 pound of feed water from 50° to 
 
 aiO°; and this is tj^q^ITq. or about 1/5 of the available heat 
 
 in 1 pound of exhaust steam. Taking this into account, there 
 remains for other heating purposes 0.8 X 4/5 = 0.64 of the en- 
 tire quantity of steam supplied to the engine. 
 
 In the above computation it is assumed that the condensation 
 from the exhaust is wasted and that cold water must be con- 
 stantly supplied to take its place. In all modern plants the oil is 
 removed from the exhaust steam before turning it into the heat- 
 ing system and the condensation returned to the boilers, thus 
 reducing the "make-up" water to a minimum. 
 
 When the steam required for heating equals, or exceeds, the 
 exhaust from the engine, practically no allowance need be made 
 for feed-water heating, as the only make-up water required is 
 that for replacing the loss due to cylinder condensation. Under 
 these conditions we may assume that at least 80 per cent of the 
 steam supplied to the engine will be available in the exhaust for 
 heating purposes. 
 
 When only a part of the exhaust can be utilized, the conditions 
 are changed, and the amount of steam required for feed-water 
 heating will vary with the proportion discharged outboard. 
 
 Conditions when Live Steam Should be Used. — ^When the 
 quantity of steam required for heating is small compared with 
 the total amount supplied to the engine, or when the heating sea- 
 son is short, it is often more economical to run the engine con- 
 densing and use live steam for heating. This can be determined 
 in any particular case by computing the saving in fuel by the use 
 of a condenser, taking into account the interest and depreciation 
 on the first cost of the condensing apparatus, and the cost of 
 water, if it must be purchased, and comparing it with the cost of 
 heating with live steam. 
 
 Usually, however, in the case of office buildings and institu- 
 tions, and commonly in the case of shops and factories, especially 
 
EXHAUST STEAM HEATING 
 
 171 
 
 in northern latitudes, it is advantageous to use the exhaust for 
 heating, even if a condenser is installed for summer use only. 
 
 Effect of Back-Pressure. — The principal objection to the use 
 of exhaust steam for heating has been the higher back pressure 
 required on the engine, resulting in a loss of power nearly pro- 
 portional to the ratio of the back pressure to the mean effective 
 pressure. There are two ways of offsetting this loss; one by 
 raising the initial or boiler pressure, and the other by increasing 
 the cut-off of the engine. 
 
 BY-PASS 
 VALVE 
 
 Fig. 120. Float Trap. 
 
 Fig. 121. Bucket Trap. 
 
 Engines are usually designed to work most economically at a 
 given cut-off, so that in the majority of cases, it is undesirable to 
 change it to any extent. Raising the boiler pressure, on the other 
 hand, is not so objectionable if the increase amounts to only a 
 few pounds. 
 
 To Offset Back Pressure. — The necessary change in either 
 initial pressure or cut-off to offset a given rise in back pressure 
 is easily obtained. 
 
 Computations for an engine having a clearance of 5 per cent, 
 supplied with steam at 80 pounds pressure and cutting off at ^4 
 stroke, show that raising the back pressure 3 pounds calls for a 
 corresponding increase of only 5 pounds in the boiler pressure to 
 maintain the same power of the engine. 
 
 The indicator card shows a back pressure of about 3 pounds 
 when an engine is exhausting into the atmosphere, so that an in- 
 crease of 3 pounds would bring the pressure up to a total of 5 
 
172 
 
 HEATING AND VENTILATING PLANTS 
 
 pounds, which should be more than ample to circulate the steam, 
 through any well-designed heating system, even though it be of 
 comparatively large size. 
 
 A modern heating plant with ample mains and branches should 
 circulate freely on a pressure not exceeding 2 pounds, and good 
 results are often obtained with 1 pound or even less. 
 
 Improvements in the apparatus employed for vacuum heating- 
 have caused this system, in different forms, to be quite generally 
 
 
 Fig. 122. Pratt Return Tiap. 
 
 used in exhaust heating, especially in plants of large size. Im 
 this case there is no increase in the back-pressure on the engine: 
 and in most instances it is somewhat reduced. 
 
 Special Apparatus. 
 
 Steam Traps are used for draining the water of condensation- 
 from steam pipes, coils, heaters, etc., without allowing the steami 
 to escape at the same time. There are a great many different 
 forms, most of them, however, coming under the heads of float,, 
 bucket, and expansion traps. Fig. 120 shows the Curtis trap, a, 
 simple form of the first type. When the water line reaches a. 
 certain point, the float rises and opens the discharge valve A, 
 which is placed near the bottom of the trap. As the water flows; 
 out, the float falls, and the valve closes before being uncovered,, 
 so that no steam is allowed to escape. 
 
EXHAUST STEAM HEATING 
 
 173 
 
 Bucket Traps. — A bucket trap is shown in Fig. 181. In this 
 case the entering water fills the space around the bucket and 
 floats it, thus closing the valve A. After the space becomes filled, 
 the water overflows into the bucket, causing it to sink. As the 
 conical plug is attached to the bucket, the valve is opened, and 
 the water flows through openings in the surrounding sleeve, as 
 indicated by the arrows, and is forced upward through the inner 
 
 Fig. 123. Automatic Return Pump. 
 
 tube by the steam pressure acting upon its surface. As soon as 
 the bucket is partly emptied it again rises and closes the valve 
 before the opening has become uncovered to admit the passage 
 of steam. Both of the traps above described are provided with 
 by-pass valves for blowing out. 
 
 Expansion Traps. — These work upon the same general prin- 
 ciple as an automatic air valve, and are frequently used where the 
 amount of condensation is small. 
 
 Return Traps. — The systems of steam heating previously de- 
 scribed are those in which the water of condensation flows back 
 to the boiler by gravity. When exhaust steam is used the pres- 
 sure is much below that of the boiler and the condensation must 
 be returned either by a return trap or pump. 
 
 A return trap differs from the ordinary steam trap in that it 
 
174 
 
 HEATING AND VENTILATING PLANTS 
 
 will discharge against a higher pressure than the system with 
 which it connects, and for this reason is often used in small 
 plants for returning the condensation from an exhaust steam 
 heating system back into the boilers. 
 
 The Pratt return trap is shown in Fig. 123. In operation, con- 
 densation enters at the top of the trap; when nearly full, the 
 rising of an interior bucket tilts an outside lever, thus causing 
 the weight M to move to the other end of its travel, and in so 
 doing, open a valve which admits steam at boiler pressure to the 
 
 Fig. 124. Webster on Separator. 
 
 trap. The pressures thus being equalized, the water flows into 
 the boiler by gravity. Check valves in the inlet and outlet con- 
 nections prevent any movement in the wrong direction during the 
 filling and emptying of the trap. In order to operate success- 
 fully a return trap should be placed at least 2 feet above the water 
 line of the boiler. 
 
 Return Pumps. — In plants of larger size the condensation is 
 returned to the boilers by an automatic return pump, usually 
 combined with a receiver, as shown in Fig. 123. 
 
 A float inside the tank connects with a valve in the steam pipe, 
 this starting and stopping the pump automatically as may be re- 
 quired to maintain a constant water level. Receiving tanks of 
 this kind are usually vented to the atmosphere and the condensa- 
 tion from different parts of the system admitted through traps. 
 
EXHAUST STEAM HEATING 
 
 175 
 
 As the make-up water is usually delivered into the receiving 
 tank, and fed into the boilers with the condensation, the size of 
 pump should be based upon the horse power of the boilers rather 
 than the size of the heating plant. Two pumps should always be 
 provided, connected with a common receiver, each of sufficient 
 capacity to do the entire work. 
 
 ATTIC SPACE 
 
 <(^^^^y^^^^-<yy^^yyyy(y^7^??7^. 
 
 yyyyyyyyyA 
 
 Fig. 125. Heating Main fiom Exhaust Pipe in Attic. 
 
 Oil Separator. — Before entering the heating main the exhaust 
 should be passed through a good form of oil separator, and it is 
 well in some cases, to purify the return water still further by the 
 use of a separating chamber or filter. Oil separators are com- 
 monly constructed upon the bafHe-plate or the centrifugal princi- 
 ples, and remove the particles of oil as they pass through with 
 the steam. A baffle-plate separator, for use in a horizontal pipe, 
 is shown in Fig. 124. The oil and condensation removed by a 
 separator should be trapped to the sewer, and not to the receiving 
 tank. 
 
 Piping and Valves. 
 
 When the exhaust steam is not sufficient for the entire heating 
 work, live steam must be admitted through a pressure reducing 
 
176 
 
 HEATING AND VENTILATING PLANTS 
 
 valve. This condition is especially liable to occur in office build- 
 ings and similar plants where the required power, and hence the 
 available exhaust, varies widely during different parts of the day. 
 In order to make the steam supply automatic the system must 
 be equipped both with a reducing valve and a relief or back- 
 pressure valve ; the former for admitting live steam when the ex- 
 haust is not sufficient to maintain the required pressure, and the 
 latter for allowing the surplus to pass outboard when the quantity 
 is greater than can be condensed in the heating system. 
 
 BALANCE PIPE 
 
 Fig. 126. Curtis Trap as a Water-Line Trap. 
 
 Supply and Return Piping. — Any of the systems of piping 
 already described may be used, but great care should be taken 
 that as little resistance as possible is introduced at bends and 
 fittings, and the mains and branches should be of ample size. 
 Usually the best results are obtained from the system in which 
 the main steam pipe is carried directly to the top of the building, 
 the distributing pipes run from that point, and the radiators sup- 
 plied by a down-flowing current of steam. 
 
 Exhaust Pipe and Heating Main. — When this system is em- 
 ployed, it is customary to carry the main exhaust pipe through 
 the roof and provide it with an exhaust head draining back to 
 the basement. The heating main is taken off from the vertical 
 pipe in the attic space as shown in Fig. 185 and a back-pressure 
 valve placed in the outboard branch just above the connection. 
 
EXHAUST STEAM HEATING 
 
 177 
 
 0^= 
 
178 HEATING AND VENTILATING PLANTS 
 
 The main should be pitched downward and outlets taken from 
 the bottom in order to drain the condensation through the drops. 
 As these gradually reduce in size from top to bottom it results 
 in smaller pipes through the lower floors, which is a decided ad- 
 vantage. It is frequently advisable to combine this system with 
 the up-fed method of heating for the first floor, which is gen- 
 erally high studded and requires a large amount of radiation. 
 
 Relieving the down-fed system of this load means smaller 
 risers, which, in modern office buildings, results in a considerable 
 saving. Another reason for putting the first floor on a separate 
 system is that dryer steam may be had directly from the base- 
 ment mains. 
 
 Pipe sizes should generally be based on a drop in pressure of 
 14 pound in each 200 feet length of run. 
 
 In order to secure the benefit of a sealed return a "false 
 water-line," so called, may be established by the use of a water- 
 line trap. This consists of a constant discharge float trap of large 
 size mounted at such an elevation as may be necessary to produce 
 the desired depth of water seal. The return pipe should be 
 brought into the bottom of the trap instead of the upper part, as is 
 usually the case, and a balance pipe for equalizing the pressure 
 connected with the top. This pipe should be connected into the up- 
 per side of a return or steam main, and should be, if possible, not 
 less than 15 or 20 feet in length and provided with a globe valve 
 near its connection with the main. The reason for this is to allow 
 the space above the water in the trap to become filled with air, 
 after which the valve may be opened just enough to allow the 
 steam pressure to act upon the air cushion in the trap without 
 driving it out. If steam is allowed to enter the trap, its contact 
 with the cooler return water will cause a rapid condensation, thus 
 producing a partial vacuum, which will often result in draining 
 the entire system of sealed returns. 
 
 Fig. 126 shows a Curtis trap connected for use as a water- 
 line trap. 
 
 The general method of making the main supply and return con- 
 nections for an exhaust steam heating system is shown in Fig. 
 127. 
 
EXHAUST STEAM HEATING 
 
 179 
 
 Vacuum Systems. 
 
 When exhaust steam is used for heating in large buildings, and 
 especially where there are long runs of horizontal pipe as in man- 
 ufacturing plants, it is usually advisable to employ some form of 
 vacuum system. This not only removes the back pressure from 
 the engine but also ensures a rapid and positive circulation of 
 steam through the radiators and prevents any tendency to water- 
 hammer. 
 
 Types of Vacuum Systems. — Vacuum systems are of two 
 
 RETURN 
 CONNECTION 
 
 Fig. 1 28 . Webster Sylphon Thermotor ' 
 
 general classes. In one, the radiators require two connections, 
 but the usual hand valve on the return is replaced by a special 
 automatic valve, which opens when in contact with air or water 
 and closes in the presence of steam. 
 
 The returns are gathered into a single main, and are connected 
 with a vacuum pump, which delivers the condensation and air 
 into a receiving tank, where separation takes place and from 
 which the water is pumped back to the boilers. Short circuiting 
 through the various coils and radiators is prevented by the action 
 of the automatic return valves, which cause each radiator to act 
 independently of the others. 
 
180 
 
 HEATING AND VENTILATING PLANTS 
 
 There are various makes of these valves upon the market, two 
 of which are shown in Figs. 12.8 and 129. 
 
 The first of these is a thermostatic valve operated by a volatile 
 liquid enclosed in a metal sylphon or bellows. The second is a 
 float valve and is actuated by changes in the height of the water- 
 line within the chamber "A." Valves of this kind are similar in 
 
 RETUR N 
 CONNECflOm 
 
 Fig. 129. Monash Radifier. 
 
 principle and operation to automatic air valves, except they are 
 made to discharge water also, and have a much larger port open- 
 ing. 
 
 Webster System. — The general arrangement of basement piping 
 for the Webster System is shown in Fig. 130. 
 
 Exhaust steam is brought from the engine as shown; one 
 branch being connected with a feed-water heater while the other 
 is carried upward and through a grease extractor where it 
 branches again, one line leading outboard through a back- 
 pressure valve and the other connecting with the heating main. 
 A live steam connection is made through a reducing valve as in 
 the ordinary system. 
 
 The main return is brought down to a vacuum pump which 
 
EXHAUST STEAM HEATING 
 
 181 
 
 discharges into a return tank where the air is separated from 
 the water and passes off through the vapor pipe at the top. The 
 condensation then flows into the feed-water heater from which it 
 is automatically pumped back into the boilers. The cold-water 
 feed supply is connected with the return tank and a small cold- 
 water jet is connected into the suction at the vacuum pump for 
 
 MAIN RETURN 
 
 Fig. 130. Webster System of Piping. 
 
 increasing the vacuum in the heating system by the condensation 
 of steam at this point. 
 
 In systems of this type there must be sufficient difference in 
 pressure between the supply and return systems to secure rapid 
 and complete drainage through the automatic valves. 
 
 If this relation is maintained it does not matter whether the 
 pressures are above or below the atmosphere so far as the circu- 
 lation of steam through the system is concerned. 
 
182 
 
 HEATING AND VENTILATING PLANTS 
 
 Systems with Exhauster for Removing Air. — In the second 
 class of vacuum systems the air valves are connected by piping 
 with an ejector or exhauster, vifhich removes the air from the 
 radiators, thus allowing the steam to flow in and take its place. 
 The condensation in this case flows to the receiving tank by 
 gravity, the same as in the ordinary pressure system. 
 
 The common expansion air valve may be used on the radiators, 
 although a special form designed with reference to the quick dis- 
 
 Fig. 131 . Steam and Air Connectioas in Paul System. 
 
 charge of air is usually employed. This system is not so well 
 adapted to plants having long horizontal runs of pipe as the one 
 previously described, where a suction is attached to the main re- 
 turn. 
 
 Paul System. — Fig. 131 shows the general method of making 
 the steam and air connections for the Paul System. 
 
 A A are the returns from the air valves and connect with the 
 
EXHAUST STEAM HEATING 183 
 
 exhausters as shown. Live steam is admitted in small quantities 
 through the valves B B and the mixture of air and steam is dis- 
 charged outboard through the pipe C. D D are gauges showing 
 the pressure in the system, and E E are check valves. The ad- 
 vantage of this system depends principally upon the quick re- 
 moval of air from the various radiators and pipes which consti- 
 tutes the principal obstruction to circulation although the induct- 
 ive action in many cases is sufficient to cause the system to oper- 
 ate somewhat below atmospheric pressure. 
 
 Practically all systems of vacuum heating employ certain pat- 
 ented devices, and plants' of this kind should be laid out under the 
 general direction of the company furnishing the special apparatus 
 to be used. 
 
CHAPTER XII. 
 ELECTRIC HEATING. 
 
 Unless electricity can be produced at a very low cost, it is not 
 practicable for Keating residences or large buildings. 
 
 The electric heater, however, has quite a wide iield of applica- 
 tion in heating small offices, bathrooms, electric cars, etc. It is a 
 convenient method of warming isolated rooms on cold mornings 
 in late spring and early fall, when the regular heating apparatus 
 of the building is not in operation. It has the advantage of 
 being instantly available, and the amount of heat can be regulated 
 at will. Electric radiators are clean, do not vitiate the air, and 
 are easily moved from place to place. 
 
 Heat is obtained from the electric current by placing a resist- 
 ance in its path, and all electric heaters are constructed upon 
 this principle. 
 
 Types of Heaters. — There are various forms of heaters in use, 
 some consisting of a series of loops or coils of iron wire so ar- 
 ranged that a variable number can be thrown into the circuit, as 
 more or less heat is required. 
 
 In other cases the heating material is embedded in enamel or 
 fire-clay or other substance of a similar nature, which is a non- 
 conductor of electricity but a good conductor of heat. The re- 
 sistance is usually so proportioned that the temperature of each 
 coil or section is constant under the action of the current sup- 
 plied; regulation being secured by varying the number of coils 
 in use. Common forms of electric heaters are shown in Figs. 
 132, 13.3 and 134. The first is a standard form of air heater and 
 is made in sizes taking from 750 to 6,000 watts per hour. The 
 second is a foot warmer, made in two sizes, taking ,200 and 400 
 watts respectively. Fig. 134 shows a luminous heater. This is 
 made in sizes taking from 750 to 1,500 watts. 
 
 Calculation of Electric Heaters. — The formula for the calcula- 
 tion of electric heaters is // = PRt X 0.24, in which 
 
 H = heat, in calories. 
 
 184 
 
ELECTRTC HEATING 
 
 185 
 
 / = current, in amperes. 
 
 R = resistance, in ohms. 
 t = time, in seconds. 
 
 Material for Heaters. — Since the resistance of metals in- 
 creases with the temperature, a thin wire heated by a current 
 passing through it will resist more and more, and grow hotter 
 until the loss of heat by conduction and radiation equals that sup- 
 plied by the current. 
 
 Fig. 132. Electric Heater. 
 
 In a short wire, fusion will begin before sufficient heat can be 
 given off for commercial purposes, so that in electric heaters it 
 is necessary to use either long lengths of thin wire, or carbon, 
 which resists fusion. In the majority of heaters, coils of thin 
 wire are used, separately embedded in some substance of poor 
 electrical, but good thermal, conductivity, as already stated. 
 
 Examples. — What resistance must an electric heater have to 
 give off 6,000 B. T. U. per hour, with a current of 30 amperes? 
 We know that 1 B. T. U. ^ 2^53 calories, so in the present case 
 6,000 X 252 = 1,512,000 calories must be provided. 
 
 Substituting the known values in the formula, we have 
 
 1, 512,000 = 202Xi?X 3,600X0.24, 
 from which 
 
 R = 
 
 1,512,000 
 345,600 
 
 = 4.37 ohms. 
 
186 
 
 HEATING AND VENTILATING PLANTS 
 
 A heater having a resistance of 3 ohms is to supply 3,000 B. T. U. 
 per hour. What current will be required? 
 
 3,000X252 = 756,000 calories. 
 
 Substituting the known values in the formula, and solving for /, 
 we have 756,000 = PX3X3,600X0.24, from which 7=V291.6 
 = 17+amperes. 
 
 Fig. 133. 
 
 Fig. 134. 
 
 Fig. 133. Electric Heater. 
 
 Fig. 134. Electric Heater of Luminous Type. 
 
 Connections for Electric Heaters. — The method of connecting 
 an electric heater with the mains is practically the same as for a 
 light which requires the same current. The principle of electric 
 heating is sometimes compared with a steam system in which the 
 radiators have two pipe connections, and the condensation is 
 returned to the boiler by a pump. 
 
ELECTRIC HEATING 187 
 
 In the electric system the boiler pressure is represented by the 
 electro-motive force, and the pump is replaced by a generator. 
 
 Cost of Electric Heating. — The commercial unit for electricit}- 
 is the ivatt-how. and from physics we learn that 
 
 1 watt = l joule per second. 
 1 joule = 0.24 of a calorie. 
 
 1 calorie= — — of a B. T. U. 
 252 
 
 r, .V,- 1 .. X, 60X60X0.24 „ .„ ^ ^ ..^ 
 
 From this 1 watt-hour = = 3.42 B. T. U. 
 
 252 
 
 Electricity is usually sold on the basis of 1,000 watt-hours, 
 called a Kilowatt-hour, which is equivalent to 3,420 B. T. U. 
 From this it is evident that the B. T. U. required per hour for 
 warming an}- given room, divided by 3,420, will the give Kilo- 
 watt-hours necessary for supplying the required amount of heat. 
 
 Comparative Cost of Steam and Electric Heating. — The ex- 
 pense of heating in this manner must always be great, unless the 
 electricity can be supplied at an exceedingly low cost. Based on 
 present practice, the average transformation into electricity does 
 not account for more than 5 or 6 per cent of the energy in the 
 fuel which is burned in the furnace. 
 
 In steam and hot-water heating, the average amount utilized 
 will probably be about 60 per cent, from which the expense of 
 electric heating is found to be from 9 to 10 times greater than by 
 these methods. 
 
 This may be shown in another v/ay by a practical example. Let 
 us assume that by the use of good coal, well-designed boilers, 
 and condensing engines, we are able to deliver 1 H. P. for each 
 214 pounds of coal burned per hour. Let us also assume the 
 combined efficiency of the dynamo and circuit to be 85 per cent. 
 Then each H. P. delivered by the engine produces 0.85 electrical 
 H. P at the heaters, which is equivalent to 
 
 0.85X33,000X60 , ^^o p t^ tt x. 
 — — = 2,163 B. T. U. per hour. 
 
 778 
 
 Since it requires 21/2 pounds of coal to produce 1 H. P., it fol- 
 
188 HEATING AND VENTILATING PLANTS 
 
 lows that the heat given out at the radiator per pound of coal 
 burned in the furnace will be 2,163 -=- 21/2 = 265 B. T. U. A 
 well-designed steam or hot-water heating system utilizes about 
 8,000 B. T. U. per pound of coal. Therefore, the efficiency of the 
 electric system is to that of the steam system as 865 is to 8,000 
 or 1 to 9.2. 
 
CHAPTER XIII. 
 FANS. 
 
 There are two types of fans in common use, known as the 
 centrifugal fan or blower, and the disk fan or propeller. 
 
 Centrifugal Fans consist of a number of straight or slightly 
 curved blades extending radially from an axis as shown in Fig. 
 135. When the fan is in motion the air in contact with the blades 
 
 Fig. 135 
 
 is thrown outward by the action of centrifugal force and deliv- 
 ered at the circumference or periphery of the wheel. A partial 
 vacuum is thus produced at the center of the wheel, and air from 
 the outside flows in to take the place of that which has been dis- 
 charged. Fig. 136 illustrates the action of a centrifugal fan, 
 the arrows showing the path of the air. 
 
 This type of fan is usually enclosed in a steel-plate casing of 
 such form as to provide for the free movement of the air as it 
 escapes from the periphery of the wheel. An opening in the 
 circumference of the casing serves as an outlet into the distribut- 
 ing ducts which carry the air to the various rooms to be ven- 
 tilated, or to the furnaces in the case of mechanical draft. 
 
 189 
 
190 
 
 HEATING AND VENTILATING PLANTS 
 
 Fig. 136. Showing Action of Centrifugal Fan. 
 
 Fig. 137. Fan with Steel-Plate Casing. 
 
FANS 191 
 
 A fan with casing is shown in Fig. 137. The discharge open- 
 ing can be located in any position desired, either up, down, top 
 horizontal, bottom horizontal, or at any angle. Where the height 
 of the fan room is limited, a form called the three-quarter housing 
 may be used, in which the lower part of the casing is replaced by 
 a brick or cemented pit extending below the floor level. (See 
 Fig. 138.) 
 
 Cone Fans. — Another form of centrifugal fan is shown in Fig. 
 139. This is known as the cone fan and is commonly placed in an 
 opening in a brick wall and discharges air from its entire peri- 
 phery into a room called a plenum chamber, with which the 
 various distributing ducts connect. This fan is often made double 
 by placing two wheels back to back and surrounding them with a 
 steel casing in a similar manner to the one shown in Fig. 137. 
 Cone fans are particularly adapted to church and schoolhouse 
 work, as they are capable of moving large volumes of air at 
 moderate speeds. 
 
 Multivane Fans. — The multivane fan, shown in Fig. 140, is 
 also of the centrifugal type. This has a large number of narrow 
 blades so formed as to produce an even discharge of air the en- 
 tire length. These fans are enclosed in a steel plate casing sim- 
 ilar to those already described and are used for the same general 
 purposes. Fans of this type are smaller and lighter for a given 
 capacity and require less power. 
 
 Uses of Centrifugal Fans. — Centrifugal fans are used almost 
 exclusively for supplying air for the ventilation of buildings, for 
 forced-blast heating, and for mechanical draft. They are also 
 used as exhausters for removing the air from buildings when 
 there is considerable resistance due to the small size or excessive 
 length of the discharge ducts and flues. 
 
 The Disk Fan is similar in construction to the propeller of a 
 vessel and moves the air in lines parallel with its axis. It is 
 made with both flat and curved blades. Fig. 141 shows one of 
 the latter with a direct-connected electric motor. 
 
 This type of fan is light in construction, requires but little 
 power at low speeds, and is easily erected. It is especially adapted 
 to exhaust ventilation when the resistance is small, being con- 
 
192 
 
 HEATING AND VENTILATING PLANTS 
 
 veniently placed in the attic or upper part of a building and 
 driven by an electric motor. Disk fans are largely used for the 
 
 Fig. 138. Fan with Three-quarter Housing. 
 
 
 Fig. 139. Cone Fan. 
 
 ventilation of public toilet-rooms, smoking-rooms, restaurants, 
 etc., and are often connected with the main vent flues of large 
 
FANS 
 
 193 
 
 buildings, such as schools, halls,' churches, theaters, etc. They 
 are especially adapted for use in connection with gravity heating 
 
 Fig. 140. Multivane Fan. 
 
 Fig. 141. Bisk-fan, Direct Connected. 
 
 systems where the flow of air through vent flues is apt to be slug- 
 gish in mild weather. 
 
194 
 
 HEATING AND VENTILATING PLANTS 
 
 Proportions of Centrifugal Fans. 
 
 The general form of a fan of the "paddle wheel" type is shown 
 in Fig. 13.5, which represents a single spider wheel with curved 
 blades. Those over 4 feet in diameter usually have two spiders, 
 while fans of large size are often provided with three or more. 
 The number of floats or bladies commonly varies from 6 to 12, 
 depending upon the diameter of the fan. They are made both 
 curved and straight; the former, it is claimed, run more quietly, 
 but if curved too much, will not work so well against a high 
 pressure. Fig. 143 represents a fan wheel in diagram and shows 
 the principal dimensions to be considered. 
 
 ■-^ 
 
 'f 
 
 I I 
 W 
 
 Fig. 142. Diagram of Fan Wheel, Showing Principal Dimensions. 
 
 Average Dimensions. — The following proportions are averages 
 taken from fans of different sizes as made by several manufac- 
 turers for general ventilating and similar work: 
 d = 0..68D. 
 
 E = 0.35Z). 
 
 W = 0.52D. 
 
 w = 0.8W. 
 In which 
 
 D = diameter of wheel. 
 
FANS 195 
 
 d = diameter of inlet to wheel. 
 
 E = distance from center of fan to heel of blades. 
 
 W = width of fan at inlet. 
 
 w = width of fan at periphery. 
 
 These proportions, as already stated, do not represent any 
 particular make, or follow any fixed rule, but are general averages 
 taken from the catalogue dimensions of several well-known man- 
 ufacturers. 
 
 Fans are made both with double and single inlets ; the former 
 being called blowers and the latter exhausters. 
 
 The dimensions of the casing or housing vary somewhat with 
 different makers and can be obtained from their catalogues. The 
 dimensions given in the accompanying tables are from the cata- 
 logue of the American Blower Company, and will be found use- 
 ful in the design of ventilating systems for approximating the 
 required space. 
 
 The size of a fan is commonly expressed in inches, as given in 
 the first column of Tables XLIII. and XLIV. This indicates 
 approximately the height in inches of a fan with full housing. 
 The diameter of the wheel is usually expressed in feet, and can 
 be found in any given case by dividing the size in inches by 20. 
 For example, a 130-inch fan has a wheel 120 -e- 20 = 6 feet in 
 diameter. 
 
 Form of Scroll. — The scroll of the casing is usually made up 
 of the arcs of three circles of different radii, and the following 
 method will be found useful in laying out a fan to scale. (See 
 Fig. 145.) 
 
 First draw the center lines and lay off the distances OA, OB, 
 OC and OD from the catalogue dimensions of the fan to be used. 
 Then with a radius R equal to OB, and a center at Oj, draw the 
 arc Aa; with the same center and a radius 2?^ equal to O-^C draw 
 the arc bC; locate the point 0^ midway between A and C, and 
 with a radius R^ equal to O^A and a center at Oj draw the arc 
 AC. The other bounding lines can then be drawn in from dimen- 
 sions taken from the catalogue table. 
 
 The width of the casing is practically the same as that of the 
 wheel with an allowance of 1 to 2 inches for clearance. 
 
196 
 
 HEATING AND VENTILATING PLANTS 
 
 Fan Calculations. 
 
 While the probable action of a fan may be quite accurately 
 computed when discharging without resistance into free air, 
 it becomes somewhat complicated in the case of a fan working 
 under the conditions of actual practice. 
 
 
 1—9^ 
 
 
 
 — 
 
 
 
 
 U- 
 
 I^ 
 
 —J 
 
 '^ 
 
 
 s 
 
 
 
 ] 
 
 
 
 
 
 
 
 Fig. 143. 
 
 Table XLIII. 
 Dimensions of Fans with Full Housing. See Fig. 143. 
 
 Size 
 
 Diameter 
 of wheel 
 
 A 
 
 B 
 
 C 
 
 D 
 
 E 
 
 P 
 
 G 
 
 H 
 
 I 
 
 J 
 
 K 
 
 L 
 
 In. 
 
 Ft. In. 
 
 in. 
 
 In. 
 
 In. 
 
 In, 
 
 In. 
 
 In. 
 
 In. 
 
 In. 
 
 In. 
 
 In. 
 
 In. 
 
 In. 
 
 50 
 
 2 6 
 
 24 
 
 27 
 
 18 
 
 20 
 
 24i 
 
 Ki 
 
 191 
 
 205 
 
 175 
 
 185 
 
 175 
 
 4 
 
 60 
 
 8 
 
 29 
 
 .33 
 
 21J 
 
 23 
 
 29J 
 
 19J- 
 
 231 
 
 24 
 
 205 
 
 21 
 
 20 
 
 4 
 
 70 
 
 3 6 
 
 33 
 
 37 
 
 215 
 
 26 
 
 335 
 
 232 
 
 27 
 
 28 
 
 24 
 
 235 
 
 225 
 
 4 
 
 80 
 
 4 
 
 3r 
 
 42 
 
 27 
 
 30 
 
 38J 
 
 264 
 
 81 
 
 315 
 
 265 
 
 245 
 
 233 
 
 4 
 
 90 
 
 4 6 
 
 42 
 
 47 
 
 30S 
 
 34 
 
 423 
 
 30i 
 
 34J 
 
 35 
 
 30 
 
 285 
 
 255 
 
 4 
 
 100 
 
 5 
 
 46 
 
 52 
 
 345 
 
 38 
 
 m 
 
 335 
 
 385 
 
 335 
 
 33 
 
 305 
 
 283 
 
 6 
 
 110 
 
 6 6 
 
 50 
 
 57 
 
 871 
 
 42 
 
 52 
 
 871 
 
 425 
 
 42 
 
 355 
 
 32 
 
 801 
 
 6 
 
 120 
 
 6 
 
 65 
 
 62 
 
 415 
 
 46 
 
 57 
 
 411 
 
 465 
 
 465 
 
 39J 
 
 355 
 
 333 
 
 6 
 
 140 
 
 7 
 
 64 
 
 72 
 
 48 
 
 63 
 
 66 
 
 48 
 
 54 
 
 58 
 
 46 
 
 395 
 
 375 
 
 8 
 
 160 
 
 8 
 
 72 
 
 82 
 
 64 
 
 60 
 
 75i 
 
 54 
 
 62 
 
 595 
 
 51 
 
 43 
 
 411 
 
 8 
 
 180 
 
 9 
 
 81 
 
 92 
 
 60 
 
 68 
 
 84J 
 
 605 
 
 695 
 
 67 
 
 575 
 
 46 
 
 441 
 
 8 
 
 200 
 
 10 
 
 90 
 
 102 
 
 66 
 
 76 
 
 935 
 
 665 
 
 77i 
 
 74 
 
 635 
 
 525 
 
 50 
 
 10 
 
 There are various methods of calculating the capacity and 
 horse power of ideal fans working against known pressures, but 
 as these results are greatly changed by variations in the propor- 
 tions of fan and casing, and also by the resistance imposed by the 
 connecting ducts and flues, it does not seem wise in a book of this 
 
PANS 
 
 197 
 
 kind to take np the purely theoretical side of the subject to any 
 great extent. 
 
 The methods given are based upon a series of carefully con- 
 
 I. D- 
 
 I 
 
 Fig. 144. 
 
 Table XLIV. 
 DrMENSioNS OP Fans with Three-quarter Housing. See Fig. 144. 
 
 Size 
 
 Diameter 
 of wheel 
 
 A 
 
 B 
 
 C 
 
 D 
 
 E 
 
 F 
 
 G 
 
 J 
 
 K 
 
 L 
 
 In. 
 
 Ft. In. 
 
 In. 
 
 In. 
 
 In. 
 
 In. 
 
 In. 
 
 In. 
 
 In. 
 
 In. 
 
 In. 
 
 In. 
 
 50 
 
 2 6 
 
 24J. 
 
 m 
 
 20 
 
 18 
 
 27 
 
 14 
 
 9J 
 
 18S 
 
 17ii 
 
 
 60 
 
 3 
 
 29i 
 
 m 
 
 28 
 
 21J 
 
 32 
 
 IBJ 
 
 12i 
 
 21 
 
 20 
 
 
 70 
 
 8 6 
 
 33J 
 
 23J 
 
 28 
 
 24J 
 
 37 
 
 17 
 
 16i 
 
 &i 
 
 224 
 
 
 83 
 
 4 
 
 38J 
 
 26S 
 
 30 
 
 27 
 
 42 
 
 19 
 
 17i 
 
 24i 
 
 23; 
 
 
 90 
 
 4 6 
 
 42J. 
 
 .3Di 
 
 34 
 
 305 
 
 47 
 
 214 
 
 19 
 
 26.S 
 
 25^ 
 
 
 100 
 
 5 
 
 47i 
 
 m 
 
 38 
 
 84i 
 
 52 
 
 24 
 
 21 
 
 30,i 
 
 283 
 
 6 
 
 110 
 
 5 6 
 
 62 
 
 37i 
 
 42 
 
 37^ 
 
 57 
 
 86 
 
 23 
 
 33 
 
 80} 
 
 6 
 
 120 
 
 6 
 
 B7 
 
 m 
 
 46 
 
 41J 
 
 62 
 
 281 
 
 26 
 
 85i 
 
 83? 
 
 6 
 
 140 
 
 7 
 
 66 
 
 48 
 
 53 
 
 48 
 
 72 
 
 32 
 
 30 
 
 39* 
 
 37J 
 
 8 
 
 160 
 
 8 
 
 75i 
 
 B4 
 
 60 
 
 54 
 
 82 
 
 865 
 
 85 
 
 43 
 
 41J 
 
 8 
 
 180 
 
 9 
 
 84S 
 
 60J 
 
 68 
 
 60 
 
 92 
 
 40 
 
 39 
 
 46 
 
 44J 
 
 8 
 
 200 
 
 10 
 
 931 
 
 66J 
 
 76 
 
 66 
 
 102 
 
 44 
 
 43J 
 
 52S 
 
 50 
 
 10 
 
 ducted tests made by one of the leading manufacturers of fans 
 upon their standard steel-plate blowers and exhausters. While 
 the results thus obtained apply particularly to fans of their own 
 make, they may be used with a faiir degree of accuracy for any 
 fan of similar type and proportions. 
 
198 
 
 HEATING AND VENTILATING PLANTS 
 
 Pressure and Velocity. 
 
 Before taking up the subject further, let us consider briefly the 
 diflferent forms of pressure involved in the action of a fan. 
 These can best be explained by the use of a practical illustration. 
 
 Let Fig. 146 represent a blower with a short pipe attached to 
 the outlet. A and B are U-tubes, or water gauges, for indicating 
 the pressure within the pipe. A has the lower end of the tube 
 bent at right angles and turned toward the fan, while the tube 
 leading from B is straight. 
 
 Dynamic Pressure. — If the fan be revolved with the end of the 
 discharge pipe wide open, the water in the two legs of tube A 
 
 Fig. 145. Laying Out a Fan to Scale. 
 
 will stand at different levels, thus indicating a pressure within 
 the pipe, while the water in tube B remains unchanged. The pres- 
 sure indicated by A is called the dynamic pressure, and is caused 
 by the air blowing into the end of the tube which is turned 
 toward the fan; or in other words, it is the pressure due to the 
 movement or momentum of the air. As the end of the discharge 
 pipe is wide open, allowing the air to pass through freely, there 
 is no radial pressure created, and therefore none indicated by the 
 tube B. 
 
 Static Pressure. — Let Fig. 147 represent the same apparatus, 
 but with the end of the air pipe partly closed. Tube A in this 
 case shows a higher pressure than before, and there is also a 
 
FANS 
 
 199 
 
 pressure indicated by B. The latter pressure, which is similar to 
 that in a steam boiler, is called the static pressure. 
 
 Velocity Pressure. — The pressure which produces the flow of 
 air through the pipe, called the velocity pressure, is the difference 
 between the dynamic and static pressures. 
 
 Gauges to Ascertain Dynamic and Static Pressures. 
 
 When the end of the air pipe was wide open there was no 
 static pressure, hence the velocity pressure and dynamic pressure 
 were equal. But if the pipe should be entirely closed, the pres- 
 sures indicated by the gauges A and B would be the same, and 
 the velocity pressure would become zero. 
 
 Fig. 147. Determining Velocity Pressure in Blowers. 
 
 Pressure and Velocity. — When air is allowed to flow from one 
 chamber into another having a lower pressure, there is always a 
 definite relation between the difference in pressure and the ve- 
 locity of flow. This, for air at a temperature of 60°, is given 
 approximately by the formula w = 66 V A, in which v is the veloc- 
 ity of flow in feet per second, and h is the difference in pressure. 
 
200 
 
 HEATING AND VENTILATING PLANTS 
 
 expressed in inches of water as indicated by the balanced height 
 of a column of that liquid in a water gauge. 
 
 Pressure in inches of water may be reduced to ounces per 
 square inch by multiplying by 0.58, and to pounds per square 
 foot by multiplying by 5.3. 
 
 The process may of course be reversed by dividing by the same 
 factors. 
 
 Results of Tests. — In the tests referred to, a pipe the size of 
 the fan outlet and about 12 feet in length was attached directly to 
 the casing. This was provided with a blast gate at the end, so 
 that the area of outlet could be varied at will. 
 
 10 20 30 40 50 60 70 
 
 RATIO OF EFFECT 
 
 90 100 
 
 Fig. 148. Ratio of Air- Velocity Pressure to Peripheral-Velocity Pressure. 
 
 The fan was then run at a constant speed and the dynamic 
 and static pressures measured at a point about midway of the 
 pipe. 
 
 Measurements were first made with the outlet wide open and 
 then with 10 per cent reductions until the gate was entirely closed. 
 
 The pressure corresponding to the peripheral velocity of the 
 fan wheel was then determined by the formula, v = 66^/h, and 
 the various measured and computed pressures plotted as ratios 
 to the peripheral-velocity pressure. 
 
 Fig. 148 shows two of these curves for outlet openings varying 
 from 40 per cent to 100 per cent, or full opening. 
 
FANS 201 
 
 The upper curve shows the ratio between the air- velocity pressure 
 
 /a V p\ 
 
 and the peripheral- velocity pressure, I ) and the lower the 
 
 ratio between the air-velocity pressure and the dynamic pres- 
 
 /A V P\ 
 
 sure, I 
 
 '\ D P / 
 
 The practical use of these curves will be shown later. 
 
 Theoretical Capacity. 
 
 The capacity of a fan is usually expressed in cubic feet of air 
 delivered per minute, and is equal to the area of the discharge 
 outlet in square feet, multiplied by the velocity of flow. 
 
 Referring to Fig. 148 we find the ratio of air-velocity pressure 
 to peripheral-velocity pressure for a fan with 100 per cent open- 
 ing and discharging into free air, to be 0.43. The relation be- 
 tween corresponding velocities is equal to the square root of 
 this ratio, or 0.65. That is, for the conditions stated above, the 
 velocity of air-flow through the fan outlet will be equal to the 
 velocity of the fan tips multiplied by 0.65. 
 
 From this it is evident that the capacity of a fan, when dis- 
 charging into free air, is expressed by the formula 
 
 e=0.65 CRO, 
 in which 
 
 Q= volume of air moved, in cubic feet per minute. 
 
 C= circumference of fan wheel, in feet. 
 
 /?= revolutions per minute. 
 
 0=area of outlet, in square feet. 
 
 Table XLV. gives data relating to the proportions of fans of 
 different diameters, and will be found useful in computing their 
 capacities at various speeds. 
 
 Size of Outlet. — The area of outlet is based on the assumption 
 that the width of the wheel is 0.52 times the diameter. The out- 
 let is made square with a dimension each way 2 inches greater 
 than the width of the wheel. When the make of fan is known, 
 the area of outlet given in the catalogue may be used instead of 
 the above, with approximate results. 
 
202 HEATING AND VENTILATING PLANTS 
 
 Example. — What volume of air will be delivered per minute by 
 a fan 7 ft. in diameter running at a speed of 150 revolutions? 
 
 = 0.65 X 33 X 150 X 14.4 = 30,888 cu. ft. 
 Table XLVI. has .been computed by the above method, and gives 
 the volume of air delivered per minute for fans discharging into 
 free air. When connected with ventilating ducts or used for 
 mechanical draft a certain correction must be made as described 
 later. 
 
 Limit of Speed. — The speed at which a fan should operate to 
 give the best results will depend upon its use. For schools, 
 churches, and similar buildings where quiet running is essential. 
 
 Table XLV. 
 Proportions of Centrifugal Fans. 
 
 Diameter of fan Circumference Area of outlet 
 
 Ft. In. Ft. Sq. Ft. 
 
 8 6 7.8 2.1 
 
 3 9.4 2.1] 
 
 3 6 11.0 8.9 
 
 4 12.5 5.0 
 
 4 6 14.1 6.2 
 
 5 15.7 7.8 
 
 5 6 17.3 9.1 
 
 6 18.8 10.7 
 
 7 22.0 14.4 
 
 8 25.1 18.6 
 
 9 28.3 23.4 
 ]0 31.4 28.7 
 
 the peripheral velocity should not exceed 4,000 feet per minute, 
 and 3,000 to 3,500 for constant use is better. 
 
 For shops and factories where noise or vibration is not ob- 
 jectionable the velocity may be increased up to 5,000 feet or more 
 per minute. 
 
 In Table XLVI. the heavy line indicates limiting speeds for 
 the first class of buildings, while for factory work speeds should 
 not ordinarily be used which exceed those given in the table. 
 
 Relation of Volume to Speed. — In general, the volume of air 
 delivered by a fan varies directly as the speed, and the power as 
 the cube of the speed. That is, doubling the speed of a fan will 
 double its capacity, but will require 3X3X2 = 8 times the 
 power. This increase in power applies only to ideal cases, and 
 does not take into account the efficiency of the fan, which, with 
 a free outlet, increases with the speed up to a peripheral velocity 
 of about 8,000 feet per minute. However, the required power in- 
 
FANS 
 
 203 
 
 creases much more rapidly than the volume of air delivered, even 
 in the case of an actual fan, and this should always be borne in 
 mind when the question of speeding up a fan to increase its 
 capacity is considered. 
 
 In cases of this kind, a comparison should be made between 
 the power necessary to drive a larger fan running at practically 
 the same peripheral velocity and that required by the present fan 
 at a higher rotative speed. 
 
 Table XLVI. 
 
 Volume of Air Delivered by Centrifugal Fans. 
 
 Revolutions per minute 
 
 100 I 126 160 175 200 
 
 260 2T5 300 
 
 360 376 400 
 
 
 
 
 
 
 Cubic feet of air 
 
 discharged per minute * 
 
 
 
 
 2 ft. 6 in. 
 
 
 
 1 
 
 
 2946 1 .**21.^ 1 .'UTft 
 
 3748 
 6211 
 
 4015 
 6655 
 
 4286 
 
 3" 
 
 i 
 
 
 
 3996 
 6271 
 9190 
 12821 
 17457 
 22986 
 
 4487 
 6969 
 10210 
 14241 
 
 4883 
 7667 
 11230 
 
 5824 
 8365 
 
 6768 
 9069 
 
 7099 
 
 3" 6" 
 
 
 
 
 
 5577 
 8160 
 11395 
 16519 
 20429 
 26216 
 
 9767 
 14290 
 19987 
 26904 
 
 10465 
 15310 
 21365 
 
 10725 
 
 4" 
 
 
 
 
 7150 
 
 13573 
 17881 
 22930 
 .34588 
 
 12250 
 17093 
 23271 
 30657 
 39311 
 
 13276 
 18513 
 25216 
 .33205 
 
 16335 
 
 
 
 
 8643 
 11635 
 15324 
 19665 
 30888 
 45670 
 
 
 4" 6'- 
 
 15667 
 21333 
 W978 
 36037 
 56620 
 
 22785 
 
 
 10219 
 13107 
 21168 
 30378 
 43126 
 68576 
 
 9697 
 12776 
 16371 
 26732 
 37962 
 6.3726 
 73218 
 
 
 6" 
 
 19395 
 25562 
 .32763 
 51480 
 
 
 6 " B " 
 
 
 
 
 
 
 
 6" 
 
 29489 
 45028 
 68.336 
 
 
 
 41184 
 60747 
 85971 
 
 
 
 
 
 
 
 
 
 
 
 8" 
 
 52950 
 76231 
 102516 
 
 
 9 " 
 
 64490 
 
 87879 
 
 
 
 
 
 
 
 
 10" 
 
 
 
 
 
 
 
 
 
 
 i 
 
 
 
 
 
 
 
 * These results are for delivery into free air; for other conditions see "Effect of 
 Resistance." 
 
 Horse Power Required. 
 
 The horse power required for moving air through a short pipe 
 (neglecting friction) is given by the equation. 
 
 H. P.= 
 
 PXAXV 
 550 
 
 (a) 
 
 in which 
 
 P= pressure per square foot producing the flow. 
 
204 
 
 HEATING AND VENTILATING PLANTS 
 
 A = area of pipe, in square feet. 
 
 F= velocity of flow, in feet per second. 
 
 £=efl5.ciency of the fan for the given speed. 
 
 Now— — =A, in which h is the equivalent pressure expressed in 
 
 inches of water; and from this we may write, P=5.2Xh. 
 A X F= cubic feet of air discharged per second =5'. 
 Substituting these values in equation (a) gives 
 
 5.2XhXQ' 
 
 H. P.= 
 
 550 
 
 (b) 
 
 Table XLVII. 
 
 Efficiencies of Centrifugal Fans. 
 
 Double inlet fans, with free discharge 
 
 Peripheral velocity 
 in feet per minute 
 
 Efficiency 
 
 Peripheral velocity 
 in feet per minute 
 
 Efficiency 
 
 1000 
 1500 
 2000 
 2500 
 8000 
 3500 
 
 0.05 
 0.08 
 0.10 
 0.12 
 0.T4 
 0.16 
 
 4000 
 4500 
 6000 
 5600 
 6000 
 6600 
 
 0.18 
 0.20 
 0.22 
 0.24 
 0.26 
 0.28 
 
 Going back to the formula for the relation between velocity and 
 pressure, we have 
 
 v=G&vh 
 
 ^ = ^^ 
 66 
 
 4,356 
 
 Substituting this value of k in equation (b) we have 
 
 (c) 
 
 This formula gives simply the power required for moving the air, 
 and does not take into account the friction of the fan itself. 
 
FANS 
 
 205 
 
 In order to make it available for practical use, the factor for effi- 
 ciency must be introduced, and the equation finally becomes 
 
 H. P.= 
 
 0.0000022 v^ Q' 
 
 E 
 
 (d) 
 
 Table XLVIII. 
 Horse Powers Required by Fans at Various Speeds. 
 
 u 
 
 Revolutions per minute 
 
 S-2 
 
 100 185 150 175 200 225 260 275 300 825 350 375 400 
 
 S 
 
 Horse power required * 
 
 2 ft. 6 in. 
 
 
 
 
 
 
 
 
 0.6 
 1.2 
 2.2 
 3.9 
 6.0 
 8.6 
 13.0 
 18.2 
 34.5 
 
 0.7 
 1.4 
 2.6 
 4.5 
 T.O 
 10.6 
 16.2 
 22.7 
 
 0.8 
 1.7 
 3.1 
 6.4 
 8.5 
 13.0 
 18.9 
 
 1.0 
 2.0 
 3.7 
 6.0 
 9.7 
 14.4 
 
 1.1 
 2.3 
 4.1 
 7.0 
 11.3 
 
 1.3 
 
 3" 
 
 
 
 
 
 
 
 0.8 
 1.4 
 2.5 
 4.0 
 5.7 
 8.9 
 12.0 
 20.5 
 39.4 
 
 1.0 
 1.8 
 3.1 
 5.0 
 7.1 
 10.3 
 15.0 
 23. 1 
 
 2.6 
 
 3" 6" 
 
 
 
 
 
 1.1 
 1.7 
 .■3.1 
 4.8 
 6.6 
 9.6 
 17.4 
 30.2 
 50.0 
 
 4.3 
 
 4" 
 
 
 ■ 
 
 
 1.4 
 2.2 
 3.4 
 5.6 
 7.2 
 12.0 
 21.9 
 36.4 
 61.0 
 
 8.0 
 
 4" 6" 
 
 
 
 1.7 
 2.6 
 3.7 
 5.2 
 9.7 
 16.5 
 26.4 
 40.2 
 
 13.1 
 
 5" 
 
 5 " 6" 
 
 1.6 
 2.2 
 4.3 
 5.2 
 11.5 
 17.9 
 
 1.6 
 2.6 
 3.5 
 6.5 
 11.6 
 18.2 
 27.2 
 
 
 6" 
 
 
 
 
 7 " 
 
 
 
 
 
 8" 
 
 
 
 
 
 
 9" 
 
 
 
 
 
 
 
 
 10" 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 * These results are for delivery into free air ; for other conditions see " Effect of 
 Resistance." 
 
 in which 
 
 ?)= velocity of air flow through the fan outlet = peripheral velocity 
 in feet per secondXO.65. 
 Q = cubic feet of air delivered per second against atmospheric 
 
 pressure. 
 Efficiency. — This varies with the peripheral velocity, and the 
 percentage of free outlet. The efficiency at various speeds will 
 depend somewhat upon the type and make of fan, but for aver- 
 age conditions with a free outlet. Table XLVII. may be used. 
 For speeds between those given in the table, the factor cor- 
 
206 HEATING AND VENTILATING PLANTS 
 
 responding to that nearest to the required speed may be used, or 
 factors may be interpolated if desired. 
 
 Table XLVIII. has been computed by the foregoing method, 
 and gives the required horse power for driving fans of different 
 diameters at various speeds when discharging into free air. 
 
 Effect of Resistance upon Capacity. 
 
 In all formulas and tables previously given for computing the 
 capacity of fans, it has been assumed that they were discharging 
 through the full size of outlet into free air. 
 
 When a fan is connected with a system of ventilating ducts, a 
 resistance is introduced which produces exactly the same effect 
 as partially closing the outlet. That is, a static pressure is set 
 up which reduces the air-velocity pressure, and consequently the 
 capacity of the fan. The tests previoijisly referred to showed 
 that when the outlet of the fan was partially closed the volume 
 of air delivered was reduced in the same proportion. For ex- 
 ample, if the area of outlet was reduced ,^5 per cent the volume of 
 air delivered was only 75 per cent of that with 100 per cent open- 
 ing, and so on. 
 
 Factors of Resistance. — In calculating the size and speed of a 
 fan for any particular case, it is necessary to estimate the probable 
 resistance in an equivalent reduction of outlet area. A certain 
 amount of experience is necessary in order to do this success- 
 fully, but for schools, churches, halls, etc., where shallow heaters, 
 not over 8 or 10 pipes in depth are used, and where the air 
 velocity through the ducts is not more than 800 to 1,000 feet per 
 minute it may be assumed that the fan will deliver at any given 
 speed about 80 per cent of the volume of air that it would if dis- 
 charging directly into the atmosphere. For factories and similar 
 buildings, where deep heaters of 15 to 20 pipes are used, and 
 where the air is passed through the ducts at velocities of 1,500 to 
 1,800 feet per minute, the volume discharged will not exceed 65 
 to 70 per cent of that with free delivery. 
 
 These factors are for average conditions, and will be found in 
 most instances to give results closely approximating those ob- 
 
FANS 207 
 
 tained in practice. For special requirements, such variations 
 may be made as the experience of the engineer has shown to be 
 necessary. 
 
 Regulating Air Volume. — In case of doubt as to the probable 
 resistance, it is best to be on the side of safety, as it is an easy 
 matter, especially if the fan is driven by a steam engine, to re- 
 duce the speed. When electric motors are employed they are 
 usually equipped with speed-regulating rheostats, so that the 
 speed may be varied about 50 per cent ; that is, 35 per cent above 
 and 35 per cent below the normal. The air volume may be still 
 further regulated by the use of an adjustable throttling damper 
 placed in the main air duct near the fan. A damper of this kind 
 is not objectionable if made rigid against vibration, for in the 
 case of a centrifugal fan, reducing the air volume by this means 
 reduces the required power in very nearly the same proportion. 
 
 Examples. — What size and speed of fan will be necessary to 
 provide a school building with ,28,000 cu. ft. of air per minute for 
 ventilation ? 
 
 Assuming the resistance equivalent to closing the fan outlet 
 20' per cent, we must look in Table XLVI. for an air volume 
 equal to 28,000 -=- 0.8 = 35,000. Following down the heavy line 
 indicating maximum speeds for this class of work, we find that 
 a 7-ft. fan running at a speed of 175 revolutions per minute will 
 deliver 34,588 cu. ft., which is sufficiently close to the volume 
 required. 
 
 What size and speed of fan will be required to handle 20,000 
 cu. ft. of air per minute for heating a factory by the hot blast 
 system ? 
 
 Assuming a reduction of fan outlet of 30 per cent we must 
 look in the table for an air volume of 20,000-^0.7 = 28,571. 
 
 This we find to be the capacity of a 5%-ft. fan running at 
 approximately 285 revolutions per minute. For volumes between 
 those given in the table, the required speed can usually be 
 estimated with sufficient accuracy for all practical purposes, as 
 illustrated in the preceding example. If closer results are desired, 
 the speed can be computed by the methods given. 
 
208 BEATING AND VENTILATING PLANTS 
 
 Effect of Resistance upon Horse Power. 
 
 Thus far the efifect of reducing the fan outlet has been con- 
 sidered only in connection with the volume of air moved, and 
 we will now see what the efifect is upon the horse .power. Tests 
 show that when the outlet is restricted, the static and dynamic 
 pressures increase, and the air-velocity pressure decreases, thus 
 reducing the volume of air moved ; at the same time, the efficiency 
 increases until the area is reduced to about 40 or 50 per cent of 
 the full opening. 
 
 These various changes in factors affecting the horse power 
 make it necessary, theoretically, to compute the power separately 
 for each variation in resistance or pressure. 
 
 This, however, is much simplified in actual practice because it 
 so happens that for reductions in outlet area down to about 50 
 per cent the power varies almost in direct ratio with the volume 
 of air moved; that is, with the reduction of outlet area. 
 
 Example. — What will be the required size and speed of fan, 
 and horse power of engine to deliver 30,000 cu. ft. of air per 
 minute to a hall ? 
 
 30,000-^0.8 = 37,500, the volume we must look for in Table 
 XLVI. and which is found to be approximately the quantity 
 delivered by an S-lt. fan at 125 revolutions per minute. 
 
 Referring to Table XLVIIL, we find that an 8-ft. fan running 
 at this speed requires 11.6 H. P., and 0.8 of this is 9.28, or in 
 round numbers 10 H. P., the size of motor required. 
 
 When an electric drive is used, instead of an engine, it is well 
 to take the horse power directly from the table without correct- 
 ing for resistance, especially for sizes below 10 H. P. This gives 
 a factor of safety for varying conditions, which, in the case of a 
 steam engine, can be met by changing the boiler pressure or 
 point of cut-off. 
 
 Mechanical Draft. 
 
 While the conditions to be fulfilled in the case of mechanical 
 draft are similar to those in ventilation, except in the matter of 
 higher pressures, the problem is usually stated in a different 
 manner. 
 
 Instead of simply furnishing a stated volume of air at a limited 
 
FANS 209 
 
 fan speed, it is also necessary to maintain a given static pressure 
 within the ash pit of the boiler. 
 
 Fan Proportions and Speed. — The methods of determining 
 the size and speed of fan and the necessary power for driving it 
 are somewhat different in this case, and can best be illustrated by 
 working a practical example. 
 
 Example. — What will be the necessary size and speed of fan, 
 and power of engine, for furnishing 10,000 cu. ft. of air per 
 minute, under a static pressure of 1 in. of water? The system 
 is to be of the forced-draft type, with the fan located near the 
 boilers. 
 
 In working problems of this kind it is necessary to first as- 
 sume a velocity of air flow through the fan outlet, and this under 
 average conditions may be taken as about 2,000 ft. per minute. 
 
 If in the above case the volume is 10,000 cu. ft., the required 
 area of outlet will be 10,000 -^- 3,000 = 5 sq. ft., which, according 
 to Table XLV., corresponds to a -l-ft. fan. 
 
 The next step is to find the necessary speed to maintain the 
 required pressure when delivering this quantity of air. It has 
 been shown in the first part of the chapter that the air- velocity 
 pressure is equal to the dynamic pressure minus the static pres- 
 sure, or in other words, the dynamic pressure is equal to the 
 static pressure plus the air-velocity pressure, and may be ex- 
 pressed as follows : 
 
 DP=SP+AVP. 
 in which 
 
 Z)P= dynamic pressure. 
 5P= static pressure. 
 ^47/*= air- velocity pressure. 
 
 Ill the present example SP=\, and AVP =0.25, the latter being 
 computed for a velocity of 2,000 ft. per minute by the formula 
 
 »=66/a. 
 From this, 
 
 Z)P= 1-1-0.25 = 1.25, 
 and the ratio 
 
 DP 1.25 
 
210 HEATING AND VENTILATING PLANTS 
 
 Referring to Fig. 148 and following down the curve marked 
 AVP 
 
 DP 
 
 we find for a ratio of 0.20, the corresponding ratio of air- 
 
 lA V P\ 
 velocity pressure to peripheral-velocity pressure I 1 as given 
 
 by the other curve, to be approximately 0.18, and the percentage of 
 opening 0.64. 
 
 If the ratio of air-velocity pressure to peripheral-velocity pres- 
 sure is 0.18, the ratio of the corresponding velocities wiU be 
 equal to V0.18 = 0.43, and the required peripheral velocity will 
 be 3,000 -^- 0.43 = 4,651 ft. per minute. The circumference of a 
 4-ft. fan is 12.5 ft., therefore the required speed will be 4,951 -;- 
 12.5 = 372 revolutions per minute. 
 
 Horse Power. — The horse power is first computed for a fan 
 of this size and speed discharging into free air, and then reduced 
 in proportion to the equivalent reduction in outlet, which in this 
 case is 0.64. 
 
 Applying this rule to the present case we have 
 
 „ _ O.O0OO022Xi'2xe'XO.64 
 
 *'®^^-X0. 65 = 50 
 
 60 
 
 from which 
 
 1)2=2,500. 
 g' = 50X5=250 cu. ft. 
 
 £=0.17. (From Table XLVII.) 
 
 Substituing these values in the above formula, we have 
 
 „ _ _ 0.0000022 X2,500X250X0.64 _ . „ 
 
 xl. ST. -r T rz — O.^ 
 
 0.17 
 
 Effect of Temperature. — All previous calculations in connec- 
 tion with fans have been based on an air temperature of 60°. 
 
 In the case of induced draft, where the gases reach the fan at 
 a temperature of 400° to 600°. certain corrections must be made 
 
FANS 
 
 211 
 
 because of the increase in volume of a given weight, due to the 
 higher temperature. The principles upon which the necessary 
 corrections are made are as follows : 
 
 First : When air is heated and expands, the weight of a given 
 volume varies as the absolute temperature. 
 
 Second : The necessary fan speed to produce a given pressure 
 is proportional to the square root of the absolute temperature. 
 
 Third : The power required to drive a fan varies as the veloc- 
 ity of air-flow, when the pressure and area of outlet remain con- 
 stant. 
 
 Table XLIX. 
 Temperature Factors for Fan Calculations. 
 
 Temperature 
 
 of gases, 
 
 degrees F. 
 
 Factor for propor- 
 tional volume at 
 60° F. 
 
 Factor for increase 
 in speed 
 
 Factor tor increase 
 in horse power 
 
 400 
 BOO 
 600 
 
 0.T7 
 0.73 
 0.70 
 
 1.88 
 1.35 
 1.42 
 
 1.28 
 1.35 
 1.42 
 
 The factors given in Table XLIX. have been computed for a 
 rise in temperature from 60° to 400°, 500°, and 600°, and may 
 be used for correcting the air quantity, speed and horse power of 
 fans used for induced draft. 
 
 Example. — A 3-ft. fan running at a speed of 590 revolutions 
 per minute discharges 5,800 cu. ft. of air per minute, at a tem- 
 perature of 60° against a pressure of 1.5 in. of water, and re- 
 quires 3.1 H. P. What speed and horse power will be required 
 to maintain the same pressure when used for induced draft, with 
 the gases at a temperature of 600°, and what volume of air at a 
 temperature of 60° will be drawn into the furnace? 
 
 Volume, 5,800X0.70 = 4,060 cu. ft. per minute; speed, 590 
 X 1.42 = 838 revolutions per minute ; H. P., 3.1 X 1-42 = 4.4. 
 
 In the factors for horse power no account has been taken of 
 the small increase in efficiency due to the higher peripheral ve- 
 locity, as it is on the side of safety. 
 
212 HEATING AND VENTILATING PLANTS 
 
 Multi-Vane Fans 
 
 Fans of this type are superceding the steel plate or paddle 
 wheel type owing to their smaller size and higher efficiency. As 
 they vary considerably in design it is not possible to give data 
 for general use as in the case of the older type of fan. 
 
 When using multi-vane fans it is best to state the volume of 
 air to be moved, the approximate static pressure to be operated 
 against, the maximum peripheral velocity and call for the man- 
 ufacturers to determine the size, speed and horsepower for their 
 particular type of fan. Under ordinary conditions the "static 
 
 Table 
 
 L. 
 
 Air Delivkked by Di; 
 
 leter of fan, 
 
 Cubic feet pi 
 
 inches 
 
 revolution 
 
 18 
 
 1.6 
 
 24 
 
 4.4 
 
 30 
 
 8.6 
 
 36 
 
 15.0 
 
 42 
 
 13. 
 
 48 
 
 35. 
 
 64 
 
 50. 
 
 60 
 
 68. 
 
 72 
 
 119. 
 
 84 
 
 187. 
 
 96 
 
 280. 
 
 pressure in schools and churches should not exceed ^ to i^ 
 ounce per square inch, with a maximum peripheral velocity of 
 3000 feet per minute. In shops and factories the static pressure 
 will run from 1 to li^ ounces with a limiting peripheral velocity 
 of 4,000 feet per min. 
 
 Disk or Propeller Fans. 
 
 The capacity of a disk fan varies greatly with the type and 
 conditions under which it operates. The rated capacities usually 
 given in catalogues are for fans revolving in free air ; that is, 
 mounted in an opening without being connected with ducts or 
 subject to other frictional resistance. 
 
 Capacity of Disk Fans. — As the capacity and necessary power 
 are so dependent upon the resistance to be overcome, it is diffi- 
 cult to give definite rules for determining them. The following 
 data based upon actual tests apply to fans working against a 
 
FANS 
 
 213 
 
 resistance equivalent to that of a shallow heater of open pattern, 
 and connecting with ducts of medium length through which the 
 air flows at a velocity not greater than 600 or 800 feet per minute. 
 Under these conditions a good type of fan will propel the air in 
 a direction parallel to the shaft, a distance equal to about 0.7 of 
 its diameter at each revolution; and from this we have the equa- 
 tion 
 
 Q = 0.7DXRXA, 
 in which 
 
 Q = cubic feet of air discharged per minute. 
 
 Table LI. 
 Speeds of Disk Fans for Given Velocities of Air-Flow. 
 
 O M 
 
 Velocity of air flow through fan in feet per minute 
 
 u u 
 
 
 
 |.s 
 
 800 1000 1200 
 
 
 
 .3 
 D-2 
 
 Revolutions of fan p'er minute 
 
 18 
 
 762 
 
 952 
 
 1142 
 
 24 
 
 573 
 
 716 
 
 859 
 
 30 
 
 458 
 
 B72 
 
 686 
 
 36 
 
 381 
 
 476 
 
 571 
 
 42 
 
 326 
 
 408 
 
 490 
 
 48 
 
 274 
 
 343 
 
 412 
 
 54 
 
 264 
 
 317 
 
 380 
 
 60 
 
 229 
 
 286 
 
 343 
 
 72 
 
 190 
 
 238 
 
 280 
 
 84 
 
 160 
 
 200 
 
 240 
 
 96 
 
 142 
 
 178 
 
 813 
 
 D = diameter of fan, in feet. 
 
 R = revolutions per minute. 
 
 A = area of fan, in square feet. 
 
 In order to obtain the best results, the linear velocity of air- 
 flow through the fan should range from 800 to 1,300 feet per 
 minute. 
 
 Table L. has been computed on this basis, and gives the cubic 
 feet discharged per revolution for fans of different diameters. 
 
 Table LI. gives revolutions per minute for fans of different 
 diameters to produce linear velocities through them of 800, 1,000 
 and 1,200 feet per minute. 
 
 Power for Disk Fans. — The power required per cubic foot of 
 air delivered depends upon the velocity through the fan and the 
 resistance. 
 
214 HEATING AND VENTILATING PLANTS 
 
 For the conditions previously assumed the figures given in 
 Table LII. may be used. 
 
 Example. — What volume of air will be moved by a 30-in. fan 
 running at a speed of 573 revolutions per minute, and what 
 H. P. will be required to drive it? 8.6 X 572 = 4,920 cu. ft. per 
 minute, and as the velocity through the fan at this speed is 
 1,000 ft., the H. P. will be 4.9 X 0.16 = 0.784. 
 
 These tables may also be used for average conditions of dis- 
 charge ventilation where the fan is connected with a system of 
 flues and ducts in which the air velocity does not exceed about 
 800 feet per minute. As the ducts become shorter and the ve- 
 locity less, that is, when the conditions more nearly approach 
 
 Table LII. 
 Horse Powers Required by Disk Fans. 
 
 m feet per minute ^ of air moved 
 
 800 0.14 
 
 1000 0.16 
 
 1800 0.18 
 
 those of a fan revolving in free air, the speed and power for 
 moving a given volume may be reduced somewhat, and for greater 
 resistances than those stated, they should be increased. The 
 amount of increase or decrease to be allowed must be learned by 
 experience. For a fan revolving in free air, the required speed 
 for moving any given volume will be about 0.6 of that given by 
 Table L., and the horse power will drop to about 0.3 of that 
 computed by the preceding methods. It is best, however, to be 
 on the side of safety, and the engineer should be thoroughly 
 familiar with the performance of the type of fan under consider- 
 ation before departing to any great extent from the resistance 
 assumed in the methods given. 
 
CHAPTER XIV. 
 FORCED BLAST HEATING AND VENTILATION. 
 
 This system of heating, in different forms, is used extensively 
 in the warming of schoolhouses, churches, theatres, etc., where 
 a generous supply of fresh air is required. It is also adapted to 
 the warming of shops and factories, either with or without ven- 
 tilation. 
 
 The air movement, being produced by fans, is positive in its 
 action, and practically independent of outside weather conditions. 
 
 This gives it a decided advantage over natural or gravity 
 methods, especially in large buildings where the air supply must 
 be constant and of large volume. 
 
 Another advantage, in buildings of this kind, is the reduction 
 in size of the air ways, made possible by the higher velocities 
 obtained where a fan is used. There are two methods of ven- 
 tilation commonly employed, known as the exhaust and plenum 
 systems. 
 
 Exhaust Ventilation. — -This is but little used except in the case 
 of special rooms or buildings, and then usually in connection 
 with some form of heating system, which furnishes a supply of 
 warm fresh air to replace that which is removed. 
 
 When this method is employed, a partial vacuum is created 
 within the room or building, and all leakage is inward; there is 
 nothing to govern definitely the quality of the air or the place 
 of introduction. Cold drafts are likely to be created around 
 doors and windows, and it is difficult to provide suitable means 
 for warming the air as it enters. 
 
 Exhaust ventilation is used most successfully in the case of 
 toilets, smoking rooms, kitchens, laundries, etc., and in combina- 
 tion with the gravity or plenum systems of warming, where the 
 vent flues are too restricted for natural ventilation to operate 
 properly. 
 
 Plenum System. — This is the reverse of the exhaust system 
 and is employed almost exclusively where fresh air is to be sup- 
 
 215 
 
216 HEATING AND VENTILATING PLANTS 
 
 plied in any considerable amount. In operation, the air is either 
 drawn or forced through a main heater and then delivered to the 
 building under a slight pressure. This prevents the inleakage 
 of cold air and places the system under complete control, both 
 as to the volume and temperature of the air supplied. 
 
 Combined Heating and Ventilating. — Forced blast may be 
 used either for heating or ventilating alone or the two may be 
 combined in a single process. In shops and factories, where the 
 air is simply recirculated within the building, the equipment is 
 used for heating only. Again, in schools and office buildings, the 
 heating is often done by direct radiation, the fan and main 
 heater being employed simply for purposes of ventilation. In 
 the case of auditoriums, like churches, halls and theatres, where 
 both heat and ventilation are provided for a single room, the 
 two are usually combined by simply using a larger heater than 
 would be necessary for ventilation alone. 
 
 An arrangement often employed in schoolhouses and similar 
 buildings, where independent temperature regulation must be 
 provided in each room, is to warm the air to 60° or S5° at the 
 main heater and supplement this, as needed, by a small inde- 
 pendent heater placed at the base of each individual flue. In 
 the "double-duct" system, so called, two ducts are carried to the 
 base of each flue, one supplying hot air and the other tempered 
 air. By means of a mixing damper these are admitted in the 
 proper proportions to give the desired temperature to the room. 
 
 Main Heaters. 
 
 The best type of heater for any particular case will depend 
 upon the volume and final temperature of the air, the steam 
 pressure, and the available space. When the air is to be heated 
 to a high temperature for both warming and ventilating a build- 
 ing, as in the case of a shop or mill, heaters of the general form 
 shown in Figs. 14'9, 150 and 151 are used. These may also be 
 adapted to all classes of work by varying the proportions as 
 required. They can be made shallow and of large superficial 
 area for the comparatively low temperatures used in purely ven- 
 tilating work, or deeper, with less height and breadth, as higher 
 temperatures are required. 
 
FORCED BLAST HEATING AND VENTILATION 
 
 217 
 
 Pipe Heaters. — Fig. 149 shows the general construction of the 
 standard hot-blast heater of the B. F. Sturtevant Company. This 
 consists of sevenal sectional cast-iron bases withloops of wrought- 
 iron pipe connected as shown. The steam enters the upper part 
 of the bases or headers and passes up one side of the loops, then 
 across the top a'nd down on the other side, where the condensation 
 is taken off through the return drip, which is separated from the 
 inlet by a partition. These heaters are made up in sections of 
 two and four rows of pipes each and can be made any depth de- 
 
 Fig. 149. sturtevant Hot-Blast Heater. 
 
 sired by adding more sections. Heaters of this type are usually 
 enclosed in a steel casing as shown, although brick walls are often 
 used for those of large size. 
 
 Fig. 150 illustrates a 4-pipe section of the heater made by the 
 American Blower Company, and Fig. 151 the siame heater com- 
 plete, with its steel plate casing. This heater is similar in ap- 
 pearance to the one just described, but differs somewhat in its 
 
218 
 
 HEATING AND VENTILATING PLANTS 
 
 construction. The base is divided lengthwise by an inside parti- 
 tion, so that the two pipes or legs of each loop connect with 
 different chambers, one of which connects with the steam supply 
 and the other with the return. 
 
 Table LIII. gives the dimensions of standard sections, but the 
 pipes can be made any height desired to suit the conditions. 
 
 These heaters are made up of 1-inch pipe, each standard sec- 
 tion being four rows deep, but can be reduced to two rows by 
 plugging part of the openings in the base. 
 
 A4 
 
 Fig. 1 50. Sectional Heater of American Blower Company. 
 
 Heating Surface of Pipe Heaters. — The square feet of heating 
 surface in a single row is obtained by multiplying the number of 
 pipes by the height in feet, and dividing by 3. This result 
 multiplied by the number of rows will give the total heating sur- 
 face in the heater. In the above, no account has been taken of the 
 surface in the base and pipe fittings; this amounts to approxi- 
 mately 1 square foot for each foot in width of the section. 
 
 Fig. 153 shows a special form of beater particularly adapted to 
 ventilating work where the air does not have to be raised above 
 75° or 80°. It is made up of 1-inch wrought-iron pipe con- 
 nected with supply and return headers; each section contains 
 
FORCED BLAST HEATING AND VENTILATION 
 
 219 
 
 14 pipes, that is, 3 pipes wide and t pipes deep, and they are 
 usually made up in groups of 5 sections each. These coils are 
 supported upon tee irons resting upon a brick foundation. 
 
 Fig. [51. Heater with Casing. 
 
 Table LIII. 
 Dimensions of Forced-Blast Pipe Heaters. 
 
 Number of 
 pipes wide 
 
 12 
 
 15 
 
 18 22 1 25 1 28 
 
 81 
 
 ,36 
 
 40 
 
 
 Ft. In. 
 
 Ft. In. 
 
 Ft. In. 
 
 Ft. In. 
 
 Ft. In. 
 
 Ft. In. 
 
 Ft. In. 
 
 Ft. In. 
 
 Ft. In. 
 
 A 
 B 
 C 
 X> 
 
 2 111 
 
 81 
 61 
 
 3 75 
 
 3 71 
 
 »i 
 
 61 
 
 4 IJ 
 
 i 35 
 61 
 
 4 m 
 
 5 21 
 8J 
 7i 
 
 5 ik 
 
 5 lOS 
 8J 
 7§ 
 
 5 10.5 
 
 6 71 
 81 
 71 
 
 6. 7J 
 
 7 31 
 81 
 
 8 44 
 
 8 51 
 8i 
 
 9 45 
 
 9 4J 
 
 8i 
 
 8i 
 
 11 15 
 
 Heaters of this form are usually made to extend across the side 
 of a room with brick walls at the sides instead of being encased 
 in steel housings. 
 
 Cast-Iron Heaters.— 'CdiSt-'non indirect radiators of the pin 
 type are well . adapted for use in connection with mechanical 
 
220 
 
 HEATING AND VENTILATING PLANTS 
 
 ventilation, and also for heating where the air volume is large 
 and the temperature not too high, as in churches and halls. They 
 make a convenient form of heater for schoolhouse and similar 
 work, for, being shallow, they can be supported upon I-beams at 
 such an elevation that the condensation may be returned to the 
 boilers by gravity. 
 
 ur^'r" ^''""'■■"'^^^■^(fj'''^''"' 
 
 3 3. 
 
 V^^A^^W/^^/^/WJ/WWj>/j>->W/' 
 
 FBONT VIEW SIDE VIEW 
 
 Fig. 1 52. Special Heater for Ventilating. 
 
 In the case of vertical-pipe and similar heaters the bases are 
 usually below the water-line of the boilers, and the condensation 
 must be returned by the use of traps and pumps. 
 
 Vento Heater. — ^The "Vento" cast-iron heater, made by the 
 American Radiator Company, is shown in Fig. 153. This is 
 constructed especially for hot-blast work and is made up of sec- 
 tions with projecting hollow pins for increasing the radiating 
 surface and for breaking up the air currents as they pass between 
 the sections. Heaters of this type are made in three sizes, as 
 follows : the 40-inch section, containing lll^ square' feet of sur- 
 face; the 50-inch section, containing 14 square feet; and the 60- 
 inch section, containing 17 square feet. 
 
FORCED BLAST HEATING AND VENTILATION 
 
 221 
 
 Table LIV, gives working data relating to this type of heater. 
 
 Efficiency of Pipe Heaters. — The efficiency of the heaters used 
 in connection with force blast varies greatly, depending upon the 
 temperature of the entering air, its velocity between the, pipes, 
 the temperature to which it is raised and the steam pressure car- 
 ried in the heater. The general method in which the sections 
 are made up is also an important factor. 
 
 The ordinary form of pipe heater is so constructed that about 
 
 Fig. 1 53. Vento Cast Iron Heater. 
 
 •0.4 of the over-all or gross area is free for the passage of air; 
 that is, a heater 6 feet wide by 7 feet high will have a gross 
 area of 6X7^ 42 square feet, and a free area between the 
 pipes of 42 X 0-4 = 17.8 square feet. 
 
 The allowable velocity of air flow through a heater of this 
 type commonly runs from 800 to 1500 feet per minute ; the lower 
 velocities applying to general ventilating work, as in schools and 
 •churches and the higher, to factory heating. The final temper- 
 ature to which the air will be raised, in any given case, depends 
 upon the depth of the heater, or number of rows of pipe which 
 it contains. For example, under certain conditions, air enter- 
 
222 
 
 HEATING AND VENTILATING PLANTS 
 
 ing a 4-row heater at zero will have a final temperature of 4,3°, 
 while if the depth of heater is increased to 16 rows, the final 
 temperature will become 120°. Increasing the velocity, while 
 other conditions remain constant, decreases the final temperature. 
 
 Table LIV. 
 Dimensions or Vento Heaters. 
 
 
 4a-Inch Section, 1 
 
 IH Square Feet 
 
 
 
 
 Equiva- 
 
 
 
 
 
 Square 
 
 lent 
 
 Area oi 
 
 Air 
 
 Width 
 
 Number 
 
 feet heat- 
 
 in lineal 
 
 face in 
 
 space. 
 
 of 
 
 of sections 
 
 ing sur- 
 
 feet, 
 
 square 
 
 net area 
 
 Group 
 
 in Group 
 
 face in 
 
 1-inch 
 
 feet 
 
 in. sq. 
 
 in 
 
 
 Group 
 
 pipe 
 
 
 feet 
 
 inches 
 
 7 
 
 80.5 
 
 241 
 
 9.72 
 
 4.34 
 
 35 
 
 8 
 
 92 
 
 276 
 
 11.10 
 
 4.96 
 
 40 
 
 9 
 
 103.5 
 
 310 
 
 12.48 
 
 5.58 
 
 45 
 
 10 
 
 115 
 
 345 
 
 13.86 
 
 6.20 
 
 SO 
 
 11 
 
 126.5 
 
 379 
 
 15.24 
 
 6.82 
 
 55 
 
 12 
 
 138 
 
 414 
 
 16.62 
 
 7.44 
 
 60 
 
 13 
 
 149.5 
 
 448 
 
 18.00 
 
 8.06 
 
 65 
 
 14 
 
 161 
 
 .483 
 
 19.38 
 
 8.68- 
 
 70 
 
 15 
 
 172.5 
 
 517 
 
 20.76 
 
 9.30 
 
 75 
 
 16 
 
 184 
 
 552 
 
 22.14 
 
 9.92 
 
 80 
 
 17 
 
 195.5 
 
 586 
 
 23.52 
 
 10.54 
 
 85 
 
 18 
 
 207 
 
 621 
 
 24.90 
 
 11.16 
 
 90 
 
 
 50-Inch Section, 
 
 4 Square Feet 
 
 
 7 
 
 . 98 
 
 294 
 
 12.15 
 
 5.37 
 
 35 
 
 8 
 
 112 
 
 .336 
 
 13.88 
 
 6.14 
 
 40 
 
 9 
 
 126 
 
 378 
 
 15.61 
 
 6.91 
 
 45 
 
 10 
 
 140 
 
 420 
 
 17.34 
 
 7.68 
 
 50 
 
 11 
 
 154 
 
 462 
 
 19.07 
 
 8.45 
 
 55 
 
 12 
 
 168 
 
 504 
 
 20.80 
 
 9.22 
 
 60 
 
 13 
 
 182 
 
 546 
 
 22.53 
 
 9.99 
 
 65 
 
 14 
 
 196 
 
 588 
 
 24.26 
 
 10.76 
 
 70 
 
 15 
 
 210 
 
 630 
 
 25.99 
 
 11.53 
 
 75 
 
 16 
 
 224 
 
 672 
 
 27.72 
 
 12.30 
 
 80 
 
 17 
 
 238 
 
 714 
 
 29.45 
 
 13.07 
 
 85 
 
 18 
 
 252 
 
 756- 
 
 31.18 
 
 13.84 
 
 90 
 
 
 OO-Inch Section, 
 
 7 Square Feet 
 
 
 7 
 
 119 
 
 357 
 
 14.58 
 
 6.45 
 
 35 
 
 8 
 
 136 
 
 408 
 
 16.66 
 
 7.37 
 
 40 
 
 9 
 
 153 
 
 459 
 
 18.74 
 
 8.29 
 
 45 
 
 10 
 
 170 
 
 510 
 
 20.82 
 
 9.21 
 
 50 
 
 11 
 
 187 
 
 561 
 
 22.90 
 
 10.13 
 
 55 
 
 12 
 
 204 
 
 612 
 
 24.98 
 
 11.05 
 
 60 
 
 13 
 
 221 
 
 663 
 
 27.06 
 
 11.97 
 
 65 
 
 14 
 
 238 
 
 714 
 
 29.14 
 
 12.89 
 
 70 
 
 15 
 
 255 
 
 765 
 
 31.22 
 
 13.81 
 
 75 
 
 16 
 
 272 
 
 816 
 
 33.30 
 
 14.73 
 
 80 
 
 17 
 
 289 
 
 867 
 
 35.38 
 
 15.65 
 
 85 
 
 18 
 
 306 
 
 918 
 
 37.46 
 
 16.57 
 
 90 
 
 The efficiency, on the other hand, increases with the velocity 
 and decreases with the depth of heater. Both the final temper- 
 ature and the efificiency increase with the steam pressure. 
 
 Most of the data relating to hot-blast heating have been ob- 
 
FORCED BLAST HEATING AND VENTILATION 
 
 223 
 
 tained from actual tests, and those given in the following tables 
 represent the approximate results to be expected for the special 
 conditions stated. These tables, however, cover the usual range 
 of heating and ventilating work and correspond well with the 
 results obtained in practical work. 
 
 Table LV. gives the final temperature of air passing through 
 pipe heaters of different depths at different velocities. These 
 figures are for an entering air temperature of zero, with steam 
 at 5 pounds pressure in the heater, which corresponds to a 
 temperature of 328 degrees. 
 
 Table LV. 
 
 Final Air Temperatures for Different Velocities Through Heater 
 WITH Steam at s Pounds Pressure. 
 
 
 Final temperature, with air enter- 
 
 Rows of 
 pipe 
 
 
 ing heater at zero 
 
 
 800 ft. 
 
 1,000 ft. 
 
 1,200 ft. 
 
 1,500 ft. 
 
 deep 
 
 vel. per 
 
 vel. per 
 
 vel. per 
 
 vel. per 
 
 
 nun. 
 
 nun. 
 
 nun. 
 
 nun. 
 
 4 
 
 42 
 
 32 
 
 28 
 
 22 
 
 8 
 
 70 
 
 60 
 
 55 
 
 50 
 
 12 
 
 95 
 
 85 
 
 80 
 
 75 
 
 IB 
 
 120 
 
 105 
 
 100 
 
 95 
 
 20 
 
 135 
 
 126 
 
 lis 
 
 110 
 
 24 
 
 150 
 
 140 
 
 130 
 
 120 
 
 28 
 
 170 
 
 155 
 
 140 
 
 130 
 
 Table LVI. gives the efficiency of the heater, in B. T. U. per 
 square foot of surface per hour per degree difference in temper- 
 ature between the steam in the heater and the entering air, for 
 various velocities and depths of heater. 
 
 Efficiency of Cast-Iron Heaters. — Heaters made up of indirect 
 pin radiators of the usual depth have an efficiency of about 1,500 
 B. T. U. with steam at 5 pounds pressure, and are easily capable 
 of warming air from zero to 80° or over when computed on 
 this basis. 
 
 The free space between the sections bears such a relation to 
 the heating surface that ample area is provided for the flow of 
 air through the heater without producing an excessive velocity. 
 
224 
 
 HEATING AND VENTILATING PLANTS 
 
 Heaters of the "Vento" type have an efficiency very nearly the 
 same as a pipe heater for an equal depth, and if taken as 90 per 
 cent, will be on the side of safety. 
 
 Example. — How many square feet of radiation will be required 
 to raise the temperature of 800,000 cubic feet of air per hour 
 from zero to 70°, with a velocity of 1,000 feet per minute 
 through the heater and a steam pressure of 5 pounds? What 
 must be the gross or over-all area of the heater and how many 
 rows of pipes must it contain? 
 
 Table LVI. 
 Efficiencies for Duterent Velocities Through Heater. 
 
 Rows of 
 pipe 
 deep 
 
 12 
 16 
 20 
 34 
 28 
 
 B.T.O. per aq. ft. of surface per hour 
 
 per degree difference between 
 
 temperature of steam and 
 
 entering air 
 
 800 ft. 
 
 vel. per 
 
 min. 
 
 8.5 
 7.5 
 6.8 
 6,3 
 5.8 
 5.4 
 5.2 
 
 1,000 ft. 
 
 vel. per 
 
 min. 
 
 9.7 
 8.7 
 8.0 
 7.3 
 6.7 
 6.3 
 5.9 
 
 1,200 ft. 
 
 vel. per 
 
 min. 
 
 11.0 
 9.8 
 9.0 
 8.3 
 7.7 
 7.2 
 6,7 
 
 1,500 ft. 
 
 vel. per 
 
 min. 
 
 12.7 
 11.5 
 10,6 
 9.5 
 9.0 
 8.3 
 7.6 
 
 Referring back to the formula for heat required for ventilation, 
 (Chapter HI.) there will be required 
 800,000 X 70 
 
 55 
 
 1,018,181 B. T. U. 
 
 Table LV. shows that for 1,000 feet velocity, a heater 10 pipes 
 deep will give a final temperature of 
 60 + 85 
 
 2 
 
 = 72.5° 
 
 which is on the side of safety. The corresponding efficiency 
 factor, from Table LVI. is 
 
 'l+L = 8.3,5. 
 
 a 
 
 Steam at 5 pounds pressure has a temperature of 228° ; hence, 
 with air entering the heater at zero, the efficiency will be 228 X 
 8.35 = 1,900 B. T. U. per sq. ft. per hour, from which the re- 
 
FORCED BLAST HEATING AND VENTILATION 225 
 
 quired amount of radiation is found to be 1,018,181 -^- 1,900 = 
 536 sq. ft. 
 
 Further, 800,000 -^ 60 = 13,333 cu. ft. of air per minute, and 
 13,333 -=- 1,000 = 13.,3 sq. ft. of free area required through the 
 heater. Assuming the free area of a standard heater equal to 
 0.4 of the gross area, the necessary gross or over-all area in 
 the present case is found to be 13.3 -=- 0.4 = 33.3 sq. ft. 
 
 Referring to Table LIIL, we find a heater 28 pipes wide has 
 an approximate width of 6% ft. Assuming the pipes to be 6 ft. 
 in height, gives a gross area of 6 X 6% = 39 sq. ft. which is 
 ample in the present case. Computing the radiating surface of 
 a heater having these dimensions we find it to be 
 
 28 X 6 
 
 — Cl — X 10 = 560 sq. ft. 
 , o 
 
 which is slightly in excess of that required and therefore on the 
 side of safety. 
 
 When a building is to be both ventilated and warmed by a fan 
 system, the general method of determining the size of heater 
 is practically the same as in indirect gravity heating. That is, 
 first obtain the heat required for ventilation, add to that the loss 
 by transmission and leakage, and divide the sum by the efficiency 
 of the heater under the given conditions. 
 
 Example. — An auditorium is to be provided with 600,000 cu. 
 ft. of air per hour. The heat lost by transmission and leakage 
 is found to be 300,000 B. T. U. per hour in zero weather. Assum- 
 ing a velocity of 800 feet per minute through the heater, what 
 will be the required radiating surface for a steam pressure of 5 
 pounds, and how many rows of pipe should it contain? 
 
 600,000 X 70 
 
 —~ =763,636 B. T. U. 
 
 00 
 
 for ventilation ; therefore, the total heat to be supplied is 300,000 
 
 4- 763,636 = 1,063,6.36 B. T. U. per hour. 
 
 The next step is to find to what temperature the entering air 
 
 must be raised to bring in the required amount of heat. This is 
 
 given by the formula 
 
 HX55 
 T = 70 + -^ 
 
226 HEATING AND VENTILATING PLANTS 
 
 in which 
 
 T = final temperature of the entering air. 
 
 H = heat loss per hour by transmission and leakage. 
 
 V = cubic feet of air entering the room per hour. 
 Substituting the known quantities in the formula, we have, 
 _ 300,000 X 55 
 
 ^-=''+ ^00,000 =^^°- 
 Referring to Table LV. we find that a heater 12 pipes deep will 
 raise the entering air to 95° under the assumed conditions, which 
 is sufficiently near in the present case. 
 
 The corresponding efficiency, from Table LVI. is 338 X 6.8 
 = 1,550 B. T. U., which calls for a heater containing 1,063,636 
 H- 1,550 = 686 sq. ft. of surface. 
 
 Hot-Water Heaters 
 
 Hot-water is not ordinarily employed in forced-blast heating 
 as there is no especial advantage in its use. The matter of 
 temperature regulation may be cared for either by shutting off 
 sections of the heater or by the use of by-pass dampers, so that 
 steam meets all the requirements without introducing the danger 
 of freezing in sections which are not in use. 
 
 When ventilation is provided in connection with a system of 
 direct hot-water radiation under forced circulation, it is cus- 
 tomary to put the main heaters on a separate line and supply 
 them with steam. 
 
 There are instances, however, where it is more convenient to 
 run the entire system under hot water, and in cases of this kind 
 there is no objection to the arrangement, provided certain pre- 
 cautions are taken against freezing. Two common methods of 
 arranging hot-water heaters for use in fan work are shown in 
 Figs. 154 and 155. In the first of these, the water is circulated 
 through the entire heater at all times, and the final temperature 
 regulation secured by means of by- pass dampers, as indicated. 
 In Fig. 155 a throttle valve is placed in the flow main, by means 
 of which the volume of water may be reduced, but without com- 
 pletely stopping the circulation in any part of the heater. 
 
 In both cases the sections are provided with valves in supply 
 and return for use in case of repairs, or for purposes of regula- 
 
FORCED BLAST HEATING AND VENTILATION 
 
 227 
 
 tion, if desired, when the outside temperature is well above the 
 freezing point. 
 
 Efficiency of Hot Water Heaters. — Cast-iron sections of good 
 depth, used as shown in Figs. 154 and 155, and supplied with hot 
 water at an initial temperature of 200°, will raise the temperature 
 of the air from zero to about 60° with a velocity of 800 feet per 
 minute through the heater. An efficiency of about 1,200 B. T. U. 
 per square foot of surface per hour may be counted upon 
 under these conditions. If a higher final temperature is required, 
 double banks of sections must be used in order to increase the 
 depth. 
 
 W//////////////////////////^^^^^^^ 
 
 '///////////////////////^^^^^ 
 
 Ot-Ji-, 
 Flow 
 Main 
 
 K^turn 
 Main -p \ 
 0+-W- 
 
 i[ 
 
 I 
 
 mm^mmmmmmmmm ^^,,%M^;^^%%^i^i^s%M^^ 
 
 Fig. 154. 
 
 Fig. 155. 
 
 Two Arrangements for Hot Water Heaters in Fan Work. 
 
 Pipe Connections. — Hot-blast heaters, commonly called main 
 heaters, are usually divided into several sections, the number de- 
 pending upon their size, and each provided with a separate valve 
 in the supply and return 
 
 In making these, divisions, special care should be taken to 
 arrange for as many combinations as possible. 
 
 For example, a heater 10 pipes deep may be made up of three 
 sections; one of two rows, and two of four rows each. By 
 means of this division, two, four, six, eight or ten rows of pipe 
 can be used at one time, as the outside weather conditions may 
 require. 
 
 In making the pipe connections to a heater of this kind, a 
 main or header is usually run along one side, from which 
 branches of the proper size are carried to the different sections. 
 The arrangement of the returns should correspond in a general 
 
228 
 
 HEATING AND VENTILATING PLANTS 
 
 way with the supplies. The main header should be properly 
 drained, and the condensation from the heater trapped to a re- 
 ceiving tank, or returned to the boilers by gravity if the heater 
 is overhead. 
 
 Returns from Heater. — If possible, the return from each sec- 
 tion should be provided with a water-seal 2 or 3 feet in depth. 
 This is because condensation is greater in the outer sections, 
 
 EXHAUST SECTIONS 
 
 ^ 5 
 
 s 
 
 OUTBOARD^ 
 
 ^•f 
 
 I'l ■ I I ri 1 1 ■>'■ III 
 
 STEAM HEADER 
 
 -JT 
 
 EXHAUST SECTIONS 
 
 -r~ - T TT \-~r f^ -P -P -Fl ■n TO BOILER 
 
 THRO' F.W, HEATER 
 
 RETURN HEADER 
 
 Fig. 1 56. Three Sections with Exhaust or Live Steajn, as Desired. 
 
 resulting in a slight difference in pressure which causes the 
 return water from the inner sections to be drawn into the outer 
 ones, thus producing water-hammer and imperfect circulation of 
 steam. 
 
 In the case of overhead heaters the returns may be sealed by the 
 water-line of the boiler or by the use of a special water-line trap, 
 but vertical-pipe heaters resting on foundations near the floor 
 are usually provided with siphon loops, extending into a pit. If 
 this arrangement is not convenient, a separate trap should be 
 placed on the return from each section. 
 
FORCED BLAST HEATING AND VENTILATION 
 
 229 
 
 The main return, in addition to its connection with the boilers 
 or pump receiver, should have a connection with the sewer for 
 blowing out when steam is iirst turned on. 
 
 Sometimes each section is provided with a connection of this 
 kind. 
 
 Large automatic air valves should be connected with each sec- 
 tion, and it is well to supplement these with a hand pet-cock, 
 unless individual blow-off valves are provided as described above. 
 
 TBAPTOSEWES TRAP TO RECEIVER 
 
 Fig. 157. Connections with Sections Interchangeable. 
 
 Provision for Exhaust from Engine. — If the fan is driven by 
 a steam engine, provision should be made for using the exhaust 
 in the heater, and part of the sections should be so valved that 
 they may be supplied with either exhaust or live steam as desired. 
 Fig. 156 shows in diagram a method of making the connections 
 for a heater in which three of the sections may be used in this 
 way. Another way of accomplishing the same result is shown 
 in Fig. 157. In this arrangement all of the sections are inter- 
 changeable. 
 
 From 50 to 60 square feet of radiating surface should be 
 provided in the exhaust portion of the heater for each engine 
 horse power, and should be divided into at least three sections, 
 
230 HEATING AND VENTILATING PLANTS 
 
 so that it can be proportioned to the requirements of different 
 outside temperatures. 
 
 The hot condensation from the exhaust sections contains oil 
 from the engine and should not be returned to the boilers ; much 
 of its heat, however, can be saved by passing it through a feed- 
 water heater. A simple heater for this purpose may be made 
 of a piece of 8-inch pipe, 7 or 8 feet in length, with flanged 
 heads, and containing a coil made up of four lengths of 1-inch 
 brass pipe. The feed to the boilers is made to pass through the 
 
 Table LVII. 
 Sizes of Pipe for Forced-Blast Heaters. 
 
 Square feet 
 of surface 
 
 Diameter of 
 
 steam pipe, 
 
 inches 
 
 Diameter of 
 return, 
 inches 
 
 150 
 
 2 
 
 li 
 
 300 
 
 25 
 
 n 
 
 500 
 
 3 
 
 2 
 
 700 
 
 3J 
 
 2 
 
 1000 
 
 4 
 
 2| 
 
 2000 
 
 5 
 
 2^ 
 
 3000 
 
 6 
 
 3 
 
 coil, while the space around it is filled with hot condensation. 
 A similar heater is sometimes placed in the exhaust pipe from the 
 engine, for use when exhausting outboard in mild weather. After 
 passing through the feed-water heater the condensation should 
 be trapped to the sewer. 
 
 Pipe Sizes. — The sizes of the mains and branches may be com- 
 puted from the tables already given, taking into account the 
 higher efficiency of the heater and the short runs of piping. 
 
 Table LVII., based on experience, has been found to give sat- 
 isfactory results where the apparatus is near the boilers. If the 
 main supply pipe is of considerable length, its diameter should 
 be checked by the methods described in Chapter I. 
 
 Fan Drives. 
 
 Fan Engines. — A simple, quiet-running engine is desirable for 
 use in connection with a fan or blower. It may be either horizon- 
 tal or vertical, and for schoolhouse and similar work should be 
 
FORCED BLAST HEATING AND VENTILATION 231 
 
 provided with a large cylinder so that the required power may 
 be developed without carrying a boiler pressure much above 30 
 or 35 pounds. In some cases a cylinder of such size is used that 
 a boiler pressure of 12 or 15 pounds is sufificient. 
 
 Engines of the latter type should always be used when the 
 main heater is placed above the boiler and the condensation re- 
 turned by gravity, as it is undesirable to carry pressures of over 
 15 or 20 pounds upon cast-iron radiation, especially if there are 
 direct radiators connected with the same system. 
 
 The quantity of steam which an engine consumes is of minor 
 importance, as the exhaust can be turned into the coils and used 
 for heating purposes. If space allows, the engSie may be 
 belted to the fan. When it is direct-connected, there is liable to 
 be more or less trouble from noise, as any slight looseness or 
 pounding in the engine will be communicated to the air ducts and 
 the sound will be carried to the rooms above. 
 
 In case an engine is belted, the distance between the shafts of 
 fan and engine should not in general be much less than 10 feet 
 for fans up to 7 or 8 feet in diameter, and 13 feet for those of 
 larger size. When possible the tight or driving side of the belt 
 should be at the bottom, so that the loose side, coming on top, will 
 tend to wrap around the pulleys and so increase the arc of con- 
 tact. The above also applies to belted motors. Engines having 
 the crank and connecting rod encased are especially adaprted to 
 this class of work, as it protects the bearings from dust and grit 
 which are liable to be present to some extent when the engine 
 is placed in the fan room. 
 
 Motors. — Electric motors are especially adapted to the driving 
 of fans where extreme quietness of action is desired, as in 
 churches, halls, etc. They are also used where the fan is at a 
 distance from the boilers or in a location where an engine would 
 be undesirable, as at the top of a building. 
 
 This method of driving a fan is more expensive than by the 
 use of an engine, especially if electricity must be obtained from 
 outside sources, but if the building contains its own power plant, 
 so that the exhaust steam can be utilized for heating, the con- 
 venience and simplicity of motor-driven fans often more than 
 offsets the additional cost of operation. 
 
232 HEATING AND VENTILATING PLANTS 
 
 Direct-connected motors are always preferable to belted, if a 
 direct current is available, on account of greater quietness of 
 action. This is due both to the slower speed of the motor and 
 the absence of belts. 
 
 Suificient speed variation for all practical purposes can be 
 obtained by the use of a regulating rheostat without excessive 
 waste of energy. 
 
 In the case of small fans, the motor may be attached directly 
 to the framework of the housing, making the fan of the single 
 inlet pattern, but for the larger sizes it should be mounted upon 
 a separate foundation at a sufficient distance away to give free 
 access to the air inlet upon that side of the fan, also. When the 
 motor is connected in this manner, the power should be trans- 
 mitted to the fan shaft, through a flexible coupling, in order to 
 prevent binding and consequent heating due to imperfect align- 
 ment of the fan and motor bearings. 
 
 If a direct current is not available, and an alternating current 
 must be used, the advantages of electric driving are greatly re- 
 duced, as high-speed motors with belts must be employed. 
 
 Belts for Fans. — Single belts, or light double on the larger 
 sizes of fans, are preferable to those of heavy weight, as they 
 are more pliable and run with greater quietness. 
 
 The width of belt is usually fixed by the width of the fan 
 pulley, but this may be checked by the following formula : 
 
 500xi?.P. 
 
 in which 
 
 w = width of belt, in inches. 
 
 L ^= arc of contact, in feet. 
 
 R = revolutions of pulley per minute. 
 
 This applies to single belts of good quality and is based on the 
 assumption that a belt 1 inch in width under a working stress of 
 33 pounds and running at a velocity of 1,000 feet per minute will 
 transmit 1 horse power. 
 
 For double belts, substitute the constant 300 for 500 in the 
 above formula. When computing the width of belt by the above 
 method, the value of L, the arc of contact, should be taken from 
 the smaller pulley. 
 
FORCED BLAST HEATING AND VENTILATION 233 
 
 Belts should be protected from the dripping of oil or water and 
 should be cleaned and greased once in five or six months, pure 
 beef tallow being recommended for this purpose. 
 
 The joint is best made by lapping and cementing, and should 
 be stretched and cemented in place upon the pulleys. 
 
 Ducts and Flues. 
 
 The method of locating and constructing the ducts and flues 
 for carrying the air from the fan to the various rooms will de- 
 pend to a large extent upon the type of building. A main duct 
 or trunk line is usually connected with the mouth of the fan and 
 carried through the basement in such a manner as to evenly 
 distribute the air supply to the different parts of the building; 
 and branches are taken off at intervals as may be required for 
 connecting the duct with the different flues or uptakes. These 
 branches are often subdivided, and One branch from the main 
 duct is made to supply several flues. 
 
 The Distributing Ducts are usually carried at the basement 
 ceiling, but where space is limited, or when, for any other reason, 
 it is desired to keep the ceiling free, they may be carried under 
 ground and the flues extended to the basement floor. 
 
 When placed at the ceiling, the trunk lines are generally made 
 of galvanized iron, or of wire lath and plaster supported upon a 
 light frame of iron construction. The smaller branches are 
 usually made of galvanized iron in all cases, on account of the 
 ease with which this material is formed into the proper shape. 
 
 Underground Ducts are generally constructed with brick side 
 walls and cement bottom, with a covering of terra-cotta or steel 
 and concrete, or the entire duct may be of concrete. 
 
 Flues. — The uptake flues are sometimes of brick, both with 
 and without terra-cotta linings, carried up in the walls of the 
 building, and sometimes of galvanized iron concealed by lath and 
 plaster furring. This is a matter of detail depending upon the 
 general construction of the building. 
 
 If of brick, great care should be taken to give the interior 
 surfaces a smooth finish, free from projecting mortar or other 
 obstructions. 
 
234 HEATING AND VENTILATING PLANTS 
 
 The flues should always be made as direct as possible and 
 without offsets, if they can be avoided. 
 
 Supply flues should not be carried in outside walls unless 
 positively necessary; in case this cannot be avoided they should 
 be properly insulated against heat loss by the use of asbestos 
 covering or some similar material. 
 
 When the ducts and flues are constructed of galvanized iron, 
 the weight of material is generally based upon the sectional area, 
 and for ordinary conditions may be taken as follows : 
 
 Table LVIII. 
 Thickness of Galvanized Iron for Ducts. 
 
 Gauge of iron Maximum sectional area of duct 
 
 28 ISO square inches 
 
 84 300 
 
 23 450 
 
 22 750 
 
 20 1500 
 
 18 All larger sizes 
 
 Air Velocity in Ducts and Flues. — The rate of air-flow in the 
 ducts and flues will depend upon the type of building. 
 
 In factory work velocities as high as 1,500 to 1,800 feet per 
 minute, or even more, are often employed, while in the case of 
 school buildings, churches, and halls, it is more common to use 
 velocities of 1,000 to 1,200 feet in the mains, and 800 to 900 feet 
 in the branches, with flue velocities of 600 to 700 feet. The 
 entering air between the inlet windows and the fan should not in 
 general have a velocity exceeding 1,000 feet per minute, and 
 800 feet is better if there is available space for it. 
 
 Some engineers make a practice of forcing the air through 
 the heater, while others prefer to draw it through by suction. 
 The former arrangement is often used in factory heating, where 
 the heater presents a comparatively small area to the fan dis- 
 charge and has considerable depth, but in the case of shallow 
 heaters with large superficial areas it is better to draw the air 
 through them, as in this way a more uniform velocity of flow is 
 obtained over the entire surface. 
 
FORCED BLAST HEATING AND VENTILATION 235 
 
 The different types of fans have been treated in a previous 
 chapter, and their application in connection with the warming 
 and ventilation of different types of buildings will be considered 
 in Chapter XVI. 
 
CHAPTER XV. 
 
 SPECIAL DEVICES. 
 
 Automatic Temperature Regulation. 
 
 Every heating plant in which a close regulation of tempera- 
 ture is desired should be provided with automatic means of some 
 form for producing this result. There are various devices of 
 this kind upon the market, among which the Johnson and the 
 Powers systems are the most widely used, and which will be- 
 taken for purposes of illustration. 
 
 Thermostat 
 
 Baxliator 
 
 g 0) 
 
 a > 
 
 Air Pipe 
 
 8 
 
 e-^ 
 
 -1 Air 
 Compressor 
 
 Pressure 
 Tank 
 
 Fig. 1 58. Diagram of Temperature Regulating Devices. 
 
 The apparatus as now used consists of three essential features- 
 as shown in Fig. 158: First, an air compressor, reservoir and 
 distributing pipes; second, thermostats placed in the rooms or 
 spaces to be regulated; and third, special pneumatic valves on 
 the radiators, or diaphragm attachments at the mixing dampers.. 
 
 Air Compressors. — The air compressor is usually operated by 
 water pressure in small and medium-size plants and by steam in. 
 larger ones, although electricity is used in some cases. A water 
 compressor is similar in principle to a direct-acting steam pump,, 
 
 236 
 
SPECIAL DEVICES 
 
 237 
 
 in which water under pressure takes the place of steam as the 
 motive power. A piston in the upper cyhnder compresses the air, 
 which is stored in a reservoir provided for the purpose. When 
 the pressure in the reservoir drops below a certain point, the com- 
 
 Fig. 159. Fig. 160. 
 
 Fig. 159. The Johnson Hydraulic Compressor. 
 Fig. 160. Thermostat with Casing Removed. 
 
 pressor is started automatically, and continues to operate until 
 the pressure is again brought up to the normal. 
 
 It is oftentimes desirable to install both types of compressors 
 in a building, the water compressor being used as a relay in case 
 of accident to the other, or for operating dampers in the summer 
 
238 
 
 HEATING AND VENTILATING PLANTS 
 
 time when the boilers are not in use. The Johnson hydraulic 
 compressor in shown in Fig. 15fl. 
 
 Thermostats. — A thermostat is simply a mechanism for opening 
 or closing one or more small valves, and is actuated by changes in 
 the temperature of the air in which it is placed. 
 
 Fig. 161. Fig. 162. 
 
 Fig. 161. Thermostat with Casing. 
 Fig. 162. Powers Thennostat. 
 
 Johnson Thermostat. — The valves in this thermostat are 
 operated by the expansion and contraction of a U-shaped metal 
 strip, consisting of two thin pieces, one of steel and one of brass, 
 soldered together. 
 
 The principle upon which this thermostat acts may be shown 
 by reference to Fig. 160, which represents the mechanism with 
 the outer casing removed. The thermostat is mounted upon the 
 wall of the room and is connected with two small pipes (not 
 shown in the cut), one leading to the air reservoir and the other' 
 
SPECIAL DEVICES 
 
 239 
 
 to the steam valve or diaphragm to be operated. E is the metal 
 strip already mentioned, and as it expands or contracts, due to 
 changes in the temperature of the surrounding air, it actuates 
 the small valve D at the top of the thermostat. When the tem- 
 perature reaches a certain maximum point for which the ther- 
 mostat is set, the valve D is thrown over so that a communication 
 is made between the pressure reservoir and the steam valve, and 
 
 Fig. 16*. 
 Section of Powers Thermostat. 
 Powers Thermostat in Casing. 
 
 the latter is closed as will be described later. When the tempera- 
 ture again drops, valve D is thrown in the opposite direction by 
 the expansion strip, cutting off the pressure , from the reservoir 
 and exhausting the air from the steam valve, thus allowing it to 
 open under the action of a spring provided for this purpose. 
 
 Fig. 161 shows the thermostat with the casing in place. 
 
 The Powers Thermostat operates on a somewhat different 
 principle, the metal strip being replaced by an expansion disk. 
 This consists of two corrugated circular pieces of metal joined at 
 
240 
 
 HEATING AND VENTILATING PLANTS 
 
 the edges and supported and stiffened by flat steel springs as 
 shown in Fig. 162. The interior of this hollow disk contains a vol- 
 atile liquid having a boiling point of about 55°, and which is un- 
 der a pressure of about 4 pounds per square inch at a temperature 
 of 70°. Any change in temperature of the surrounding air 
 produces a corresponding change in the pressure within the disk, 
 
 Fig. [65. Fig. 166 
 
 Fig. 165. Johnson Hot- Air Thermostat. 
 Fig. 166. Johnson Pneumatic Valve. 
 
 thus increasing or diminishing its thickness. Fig. 163 shows the 
 Powers thermostat in section. A is the expansion disk, M a 
 movable flange attached to a flexible diaphragm and operating 
 the valve /. L is the exhaust valve, and H and / the pipe con- 
 nections with the pressure reservoir and with the steam valve or 
 diaphragm. 
 
 When the temperature rises the disk A expands, pressing 
 against M and thus opening the valve /. This allows the air to 
 pass from H into / through the chamber K, and thus admits the 
 pressure to the steam valve and closes it. When the temperature 
 falls, the disk contracts and the valve / is closed by the action 
 of a coil spring. The air pressure is relieved from the steam 
 
SPECIAL DEVICES 241 
 
 valve through the small exhaust valve L. Fig. 164 shows the 
 thermostat as it appears enclosed in its casing. 
 
 Hot-air Thermostat. — Fig. 165 is a side view of the Johnson 
 thermostat especially designed for insertion in the side of an air 
 duct. These are used in connection with main or primary heaters 
 at the fan, and are for regulating the temperature of the air used 
 for ventilation. 
 
 All thermostats have a certain range of regulation, generally 
 from 60° to 80°, so that they may be set to keep the room at 
 any temperature desired within these limits. A change in tem- 
 
 Fig. 167. Powers Pneumatic Valve. 
 
 perature of about 1° is sufficient to cause a thermostat to act 
 when in proper adjustment. 
 
 Valves. — ^The pneumatic valves which replace the usual shut- 
 off valves on the radiators are similar in construction to the 
 ordinary globe or angle valve, except the stem slides up and 
 down instead of being threaded and running in a nut. The top 
 of the stem connects with a flat plate which rests against a rubber 
 or corrugated metal diaphragm. The valve is held open by a 
 spring, and is closed by admitting compressed air to the space 
 above the diaphragm. In connecting up the system, small con- 
 cealed pipes are carried from the air reservoir to the thermostat, 
 which is placed upon an inside wall of the room, and from here 
 to the pneumatic valve at the radiator. 
 
242 
 
 HEATING AND VENTILATING PLANTS 
 
 Fig. 166 shows a section through a pneumatic steam valve. 
 A is the connection for the air pressure, F the rubber diaphragm 
 and G the spring for opening the valve after the pressure is 
 exhausted. Fig. 167 shows an external view of a similar valve. 
 
 Diaphragm Motors. — Dampers are operated pneumatically in 
 a similar manner to steam valves. A diaphragm motor, so called, 
 is acted upon by the air pressure, and this in turn lifts an arm 
 
 Fig. 1 68. Diaphragm Motor for Operating Dampers. 
 
 Fig. 1 69. Mixing Dampers. 
 
 which is connected to the damper by means of chains or levers, 
 thus securing the desired movement. A diaphragm of this kind 
 is shown in Fig. 168. 
 
 Dampers. — A common form of mixing damper for use in con- 
 nection with indirect heating stacks is shown in Fig. 169, and Fig. 
 170 shows the same in position and connected with a diaphragm 
 motor for pneumatic actuation. Fig. 171 illustrates a good ar- 
 rangement of mixing dampers for the double-duct system where 
 the hot and tempered air are mixed at the bases of the uptake 
 flues. 
 
SPECIAL DEVICES 
 
 243 
 
 When mixing dampers are operated pnuematically a specially 
 designed thermostat for giving a graduated movement to the 
 damper should be used. By this arrangement the damper is held 
 in such a position at all times as to admit the proper proportions 
 of hot and cold or tempered air for producing the desired tem- 
 perature in the room with which it is connected. 
 
 With the ordinary form of thermostat the damper will be either 
 entirely closed or thrown wide open, thus causing the temperature 
 of the entering air to fluctuate between wide limits. 
 
 / 
 
 \ 
 
 lEO ^ 
 
 A 
 
 / 
 
 Fig. 170. Fig. 171. 
 
 Fig. 170. Damper Connected with Diaphragm Motor. 
 Fig. 171. Damper for Douhle-Duct System. 
 
 m 
 
 Large dampers which are to be operated pneumatically should 
 be made up in sections or louvres, the spindle of each being at- 
 tached by means of a crank or lever to a common connecting rod. 
 Dampers constructed in this manner are handled much more 
 easily than when made in a single piece. It often happens in 
 large plants that there are valves and dampers in places which are 
 not easily reached for hand manipulation. These may be pro- 
 vided with diaphragms and connected with the air-pressure sys- 
 tem for operation by hand switches or cocks conveniently located 
 at some central point in the basement or boiler room. 
 
 Methods of Automatic Control. 
 
 The general method of applying automatic temperature regula- 
 tion to a heating system will depend largely upon the arrangement 
 
244 
 
 HEATING AND VENTILATING PLANTS 
 
 of the radiating surface. In a system of direct;steam or hot- 
 water heating, pneumatic valves are placed upon the radiators 
 instead of the usual hand valves. In the case of indirect steam, 
 graduated mixing dampers are used. With indirect hot water, 
 mixing dampers may be employed or the stacks may be made up 
 of two banks of radiators, one above the other, the upper being 
 provided with pneumatic valves and the lower with hand valves. 
 
 Fig. 172. Johnson Regulator Attached to Hot- Water Boiler. 
 
 In mild weather the hand-controlled sections may be shut off, 
 but in cold weather they should be kept on continuously, both for 
 furnishing additional heat and for preventing the automatic sec- 
 tions from freezing when temporarily closed. In the case of 
 combination systems, temperature regulation is usually secured 
 by placing pneumatic valves upon the direct radiation in the 
 rooms. Automatic control may also be provided for one or more 
 sections of the main heater, being operated by a thermostat placed 
 in the main air-duct beyond the fan. 
 
SPECIAL DEVICES 245 
 
 In churches or other auditoriums where the warming is done 
 by a single large heater, two thermostats in series should be used ; 
 one placed in the air-duct and the other in the room above. These 
 are both connected with the heater, and set in such a manner 
 that if the temperature of the room rises above 70° the automatic 
 sections will be shut off, but if the air in the main duct falls 
 below 65°, they will be turned on independently of the room 
 thermostat. This arrangement prevents sending air to the room 
 at such a low temperature as to produce unpleasant drafts or 
 chilling of the floor. 
 
 Hot- Water Regulators. 
 
 In addition to the methods of regulation already described, 
 there are devices for controlling the temperature of the water in 
 heating boilers and- tanks. 
 
 Fig. 173 shows the Johnson hydraulic thermostat and regulator 
 attached to a hot-water boiler. The thermostatic tube consists of 
 an outer shell and an inner tube of two metals having different 
 coefficients of expansion, and so arranged that when the tem- 
 perature of the water reaches the maximum for which the device 
 is set, the unequal expansion of the two tubes opens a small valve 
 and admits water under pressure to a diaphragm draft regulator, 
 thus checking the fires, and so reducing the temperature of the 
 water in the boiler. 
 
 The Powers hot-water regulator for heating boilers operates 
 on a somewhat different principle. The thermostat (see Fig. 
 173), which is placed in the room, consists of a hollow disc with 
 a flexible diaphragm passing through the center. The space B is 
 partly filled with a volatile liquid which boils at a temperature of 
 60°. The space A is filled with air and is connected by a small 
 tube with the chamber D, which is filled with water and also 
 connects with the space between the two rubber diaphragms ff. 
 
 When the temperature of the room rises above 60°, vapor 
 under pressure is formed in B and forces the diaphragm over 
 against A. The air pressure from the thermostat enters the 
 chamber D through the air pipe at the top and forces the water 
 down and into the space between the two diaphragms, raising the 
 upper one and with it the lever, thus causing the damper to close. 
 
246 
 
 HEATING AND VENTILATING PLANTS 
 
 The attachment at the right is for preventing the water in the 
 boiler from reaching the boihng point, and answers in a way to 
 the safety valve on a steam boiler. It consists of a chamber E 
 enclosed in a surrounding shell F. E is partially filled with water 
 under atmospheric pressure and sealed, therefore having a boil- 
 ing point of '212°. This chamber is connected with the space 
 below the lower diaphragm as shown. F is connected at top and 
 bottom with the boiler so that water at boiler temperature circu- 
 lates through the space around E. When the temperature reaches 
 213°, the water in E boils and the pressure produced forces the 
 lower rubber against the upper one and so closes the damper 
 
 Fig. 173. Sectional View of Powers Hot- Water Regulator. 
 
 as before. As the water in the boiler is under a pressure greater 
 than the atmosphere, due to the elevation of the expansion tank, 
 it necessarily has a higher boiling point than the water in E, hence 
 the closing of the damper will occur before boiling in the heater 
 can take place. 
 
 Sylphon Regulator. — The regulator shown in Fig. 174 acts in 
 a similar manner to the one just described, but upon a somewhat 
 different principle. 
 
 This consists of two chambers, the lower one being connected 
 with the piping in such a manner that there is a circulation of 
 water through it directly from the boiler. Inside this chamber 
 and exposed to the flow of water, ds a brass cylinder containing 
 a certain amount of volatile liquid. The upper chamber contains 
 a flexible metal bellows also filled with fluid and connected by 
 a small pipe with the brass cylinder below. 
 
SPECIAL DEVICES 
 
 247 
 
 When the temperature of the water reaches the point at which 
 the regulator is set to operate, the vapor from the volatile liquid 
 exerts sufficient pressure to force enough liquid upward through 
 the tube to expand the bellows and raise the weighted lever at 
 the top, which being connected with the draft-door by a chain, 
 as in Fig. 17'3, checks the fire and thus reduces the temperature 
 of the water. 
 
 Devices of this kind may be set to automatically control the 
 temperature of the water supplied to a heating system, and may 
 
 p'l'om Holler 
 
 Fig. 1 74. Sylphon Hot- Water Regulator. 
 
 be set to act at different temperatures within certain limits. It is 
 evident from their action that they control the system as a whole 
 and cannot be made to affect the different rooms separately. 
 
 Telethermometer. 
 
 This is a device for indicating on a dial at some central point 
 the temperatures of various rooms or ducts in different parts of 
 a building. 
 
 A special transmitter is placed in each of the rooms and elec- 
 trically connected with a central switchboard. Then by means 
 of suitable switches any room may be thrown into circuit with the 
 recorder, and the temperature existing in the room at that time 
 read from the dial. 
 
248 
 
 HEATING AND VENTILATING PLANTS 
 Humidostat. 
 
 The humidostat is a device to be placed in one or more rooms 
 of a building for maintaining an even precentage of moisture 
 in the air. The apparatus consists of two essential parts, the 
 hicmidostat and the humidifier. The former corresponds to the 
 thermostat in a system of temperature control, and operates a 
 
 Fig. 175. Johnson Humidostat. 
 
 pneumatic valve or other mechanism connected with the humidi- 
 fier when the percentage of moisture rises above or falls below 
 certain limits. The operating medium is compressed air, the same 
 as for temperature control, and the two devices are usually con- 
 nected with the same pressure system. The Johnson humidostat 
 is shown in Fig. 175 and has a working range from 30 to 75 per 
 cent of moisture. The humidity of the rooms should be kept 
 between 60 and 70 per cent under ordinary conditions. In cold 
 weather, however, it will be necessary to reduce the amount of 
 moisture somewhat, owing to the "sweating" of walls and win- 
 
SPECIAL DEVICES 
 
 249 
 
 dows. In extreme weather it may be necessary to carry it as 
 low as 40 to 50 per cent on this account. The moisture in the air 
 of living rooms should never exceed 70 per cent. 
 
 The method of moistening the air will depend somewhat upon 
 circumstances. If the air for ventilation is delivered to the rooms 
 at a temperature not exceeding 70°, the humidifier is best placed 
 in the main air duct. If the air enters at a higher temperature, 
 the humidifier must be located in the same room with the 
 humidostat. 
 
 Fig. 1 76. Evaporating Pan used with Humidostat. 
 
 The moistener or humidifier may be one of several forms. 
 Where steam heating is in use and the steam is clean and odor- 
 less, a perforated pipe in the air-duct is the simplest arrangement. 
 Sometimes a spray, particularly of warm water, is used in 
 place of steam. When neither steam jet nor water spray is 
 advisable, an evaporating pan is often used. Fig. 176 shows such 
 a pan placed in the air-duct. As may be seen, a steam coil is 
 immersed in the water to heat it to the evaporating point. The 
 humidostat controls the steam supply by means of a diaphragm 
 valve and the water is kept at a constant level in the pan by the 
 use of a ball cock. Pure water is generally used, or medicated 
 water may be substituted in special cases if desired. 
 
250 HEATING AND VENTILATING PLANTS 
 
 When a spray filter or air washer is employed, this may be 
 arranged to control the humidity also and makes one of the sim- 
 plest and most effective devices for this purpose. 
 
 Air Filters. 
 
 The importance of purifying the air supply, especially to city 
 buildings, has already been taken up in Chapter III, together with 
 the most effective methods employed for this purpose. In the 
 present chapter some of the devices used in this work will be 
 briefly described. 
 
 If the air quantity is small and there is plenty of room between 
 the inlet windows and the fan, screens of light cheesecloth may 
 be used for this purpose. The cloth should be tacked to light but 
 substantial wooden frames which can be easily removed for fre- 
 quent cleaning. These screens are usually set up in "saw-tooth" 
 fashion, as shown in Fig. 177, in order to give as much surface 
 as possible in the least space. Another arrangement sometimes 
 used for larger volumes of air, is to provide a number of light 
 cloth bags of considerable length, through which the air is drawn 
 before reaching the heater. These are fastened to a suitable 
 frame or partition for holding them open, as shown in Fig. 178, 
 and should also be easily removable for cleaning. 
 
 In some cases, where space permits, the bags are hung in a 
 vertical position with heavy iron rings at the bottom, and the air 
 drawn downward through them. 
 
 The great objection to filters of this kind is their obstruction 
 to the passage of the air, especially when filled with dust. The 
 frequency with which they must be cleaned, and the great 
 amount of filtering surface required often makes their use im- 
 possible. 
 
 In order to be efficient, and not throw too great a resistance 
 upon the fan, the velocity through the filter should not be over 
 60 to 80 feet per minute. It is not often that surfaces of sufficient 
 extent to produce this low velocity can be provided and generally 
 the air volume is reduced somewhat in consequence. 
 
SPECIAL DEVICES 251 
 
 Air Washers. 
 
 The spray filter or air washer overcomes the obstacles noted 
 above and is now considered an essential part of a well designed 
 ventilating plant, especially in buildings exposed to dust or soot. 
 
 i 
 
 /VVv 
 
 V 
 
 V V 
 
 r 
 
 Fig. 177. Screen for Filtering Air. 
 
 ^ww-e3 
 
 GAL.IRON ^ 
 PARTITION 
 
 AIR FROM 
 INLET 
 
 Fig. 178. Another Form of Filter. 
 
 Air washers may be utilized for humidity control as previously 
 stated, and also for air cooling under certain conditions. 
 
 Principle of Operation. — ^^The principle of operation is practi- 
 cally the same in most of the standard machines and is illustrated 
 in the following descriptions. 
 
 The McCreery air purifying and cooling device is shown in 
 section in Fig. 179. Air enters as indicated, and first passes 
 through a tempering coil to raise it above the freezing point in 
 
252 
 
 HEATING AND VENTILATING PLANTS 
 
 winter weather; then through a double sheet of water discharged 
 from specially designed spray heads or nozzles, under a pressure 
 of 5 to 10 pounds per square inch. 
 
 Before leaving the spray chamber the air passes through an- 
 other curtain of water as shown by the arrows. It is next drawn 
 through a series of V-shaped baffles for removing the surplus 
 moisture, and then passes through a secondary or re-heater be- 
 fore reaching the fan. The water is supplied to the spray 
 heads by means of a small centrifugal pump, either belted to the 
 fan shaft or driven by an independent motor. 
 
 Fig. 179. McCreery Air Purifying and Cooliiig Device. 
 
 The spray and the water which is removed by the baffle plates 
 falls into a tank at the bottom of the spray chamber and is used 
 over and over again. When it becomes too dirty to effectually 
 cleanse the air, it is drawn off and replaced by a fresh supply. 
 
 Fig. 180 shows a plan and elevation of the Thomas purifier. 
 This is similar in principle to the one just described, except the 
 air passes through a shallower spray of water, and its path is 
 somewhat more direct. 
 
 Form, of Spray. — It has been found by experience that sheets 
 of water in the form of rain are the most efficient for removing 
 dust from the air, while a fine mist has a greater cooling effect. 
 
 Certain washers make use of a combination of these sprays in 
 the standard machines and emplo)' the latter, alone, where cool- 
 ing is the principle object sought. 
 
 Air Velocity Through Washer.- — In order to effectively re- 
 move the particles of water from the air it is necessary to limit 
 
SPECIAL DEVICES 
 
 253 
 
 the velocity of flow over the eHminator blades. For ordinary 
 conditions this usually runs from about 300 feet per minute in 
 the smaller sizes up to 500 feet in the larger ones. 
 
 Humidity Control. — During the heating season any desired per- 
 centage of humidity, within working limits, may be mtaintained 
 with an air washer by automatically controling the temperature of 
 the air leaving the eliminator and that of the water discharged 
 from the spray heads. The relative humidity of the air delivered 
 to the building will depend upon the relation of these two tem- 
 peratures, and is therefore easily regulated. 
 
 Fie. I so. Thomas Air Piu ifler. 
 
 Air Cooling. — The cooling effect obtained by re-circulated 
 spray water is due entirely to evaporation, which in turn, varies 
 with the relative humidity; evaporation taking place much more 
 rapidly with a low humidity than when the air contains a large 
 amount of moisture. 
 
 According to data published by the Warren Webster Co., air 
 •entering the washer at a temperature of 90°, with a relative 
 humidity of 70 per cent, will fall in temperature about 4.7° while 
 passing through their standard machine using a re-circulated 
 spray. If the entering air has a relative humidity of 40 per 
 cent, the drop in temperature will be 10° under the same condi- 
 tions. If running water is available for the spray, either from 
 a deep well or city mains, at a temperature of 60°, the cooling 
 ■effects will be 13.5° and 15.5° respectively, for the conditions 
 noted above. These results are for the standard Webster air 
 
254 HEATING AND VENTILATING PLANTS 
 
 washer ; with a special machine, equipped with mist nozzles only, 
 the effect will be somewhat greater. Air cooling by this method 
 is limited by the excessive humidity produced when due to 
 evaporation, and by the quantity of cooling water required when 
 due to heat transmission. 
 
 Under practical conditions, in the case of hospitals and banking 
 rooms, a temperature drop of 10 to 12 degrees is about the limit 
 for a device of this kind. 
 
CHAPTER XVI. 
 
 HEATING AND VENTILATING DIFFERENT TYPES OF 
 BUILDINGS. 
 
 The preceding chapters have been devoted to the subject of 
 heating and ventilation in a general way without applying the 
 different kinds of apparatus described to any particular type of 
 building. 
 
 An attempt will now be made to show some of the more com- 
 mon arrangements employed in different classes of buildings. 
 
 Dwelling Houses. 
 
 The warming of a dwelling house requires a system so simple 
 in construction that no special description is required other than 
 that given under the general heads of furnace, steam, and hot- 
 water heating. The first point to be considered is the selection 
 of a system, and this is usually determined by the cost of installa- 
 tion and the size and location of the house. 
 
 This point being decided, a simple plan may be drawn show- 
 ing the general arrangement and the sizes of the different parts 
 of the apparatus as previously described for the particular system 
 chosen. 
 
 Schoolhouses. 
 
 Here, as in the case of a dwelling house, the first step is the 
 selection of a system, and this as before depends upon the avail- 
 able funds and the size of building. 
 
 Assuming that a selection has been made, we will describe in 
 some detail the principle points to be considered in proportioning 
 the different parts of the equipment and in laying out the working 
 plans. 
 
 Furnace Heating. — For school buildings of small size, the fur- 
 nace system is simple, convenient and usually effective. Its use 
 is confined as a general rule to buildings having from two to four 
 rooms, although furnaces are sometimes used for eight-room 
 buildings. One furnace is not commonly made to warm more 
 
 256 
 
256 HEATING AND VENTILATING PLANTS 
 
 than two classrooms, as the warm-air pipes connecting the fur- 
 nace with the flues must be short to obtain the best results. 
 
 Like all systems which depend upon natural circulation, the 
 supply and removal of air are considerably affected by changes 
 in the outside temperature and by winds. The furnaces used for 
 schoolhouse warming are usually built of cast iron, this material 
 being durable, and easily made to present large and effective 
 heating surfaces. To adapt the larger sizes of house-heating 
 furnaces to schoolhouses, a much larger space must be provided 
 between the body and casing, to permit a sufficient volume of air 
 to pass to the rooms. The free area of the passage should be 
 sufficient to maintain a velocity of about 400 feet per minute. 
 
 Size of Furnace. — In this class of work a somewhat higher 
 rate of combustion is obtained than in the case of dwelling houses, 
 owing to more regular attendance and a stronger chimney draft. 
 
 Assuming a combustion of 6 pounds of coal per square foot 
 of grate per hour, and 8,000 B. T. U. per pound of coal, we have 
 6 X 8,000 = 48,000 B. T. U. available from each square foot of 
 grate. The heat loss by transmission and leakage from a standard 
 class room is approximately 40,000 B. T. U. per hour in zero 
 weather. 
 
 Assuming an air supply of 1,800 cu. ft. per occupant for 50 
 pupils, calls for 50 X 1,800 X 1.3 = 117,000 B. T. U. for ven- 
 tilation, making a total of 40,000 + 117,000 = 157,000 B. T. U. 
 per hour. Therefore, 157,000 -=- 48,000 = 3.3 sq. ft. of grate 
 required. In practice, this amount of grate area per standard 
 class room, will usually be found sufficient in buildings of good 
 construction. 
 
 Uptake Flues. — The velocity of the warm air within the up- 
 take flues depends upon their height and the difference in tem- 
 perature between the air within the flues and the cold air outside. 
 The action of the wind also affects the velocity of air-flow. 
 
 It has been found by experience that flues having sectional 
 areas of about 6 square feet for first-floor rooms, 5 for the second 
 floor, and 4^/2 for the third, will be of ample size for standard 
 classrooms seating from 40 to 50 pupils in primary and grammar 
 schools. These sizes may be used for both furnace and indirect 
 gravity steam heating. 
 
DIFFERENT TYPES OF BUILDINGS 
 
 257 
 
 In mild, damp weather the air supply will fail somewhat below 
 the standard desired; but if the flues are made much larger they 
 will furnish more air than can be heated in cold and windy 
 weather. 
 
 Cold-Air Duct. — The cold-air supply duct may be made three 
 fourths the size of all the warm-air flues, if free from bends, or 
 the full size, if obstructed in any way. Each furnace should, if 
 possible, receive air from two sides of the building, preferably 
 the north and south or the northwest and southeast. Each duct 
 should be of sufficient size to supply the full amount of air re- 
 
 ^ 
 
 ^ 
 
 L" 
 
 t 
 
 m 
 
 
 ^ — 1^ 
 
 r 
 
 3^ 
 
 Fig. 181. Fig. 182. 
 
 Fig. 181. Check for Cold-Ail Duct. 
 Fig. 182. Arrangement of Warm-Air Flues. 
 
 quired, and should be provided with an air check similar to that 
 shown in Fig. 181, made up of flaps of duck or light canvas, 
 closing against a screen of wire netting. To make the system 
 more complete, mixing dampers may be placed in the warm-air- 
 flues. A typical arrangement of furnace, air ways and dampers 
 is shown in Fig. 183. 
 
 Vent Flues. — The vent flues should be made about 5 square 
 feet for the first floor and 6 for the second and third. They may 
 be arranged in banks and extended through the roof in the form 
 of large chimneys, or may be carried to the attic space and there 
 gathered by means of galvanized-iron ducts connecting with roof 
 vents of wood or copper construction. The former method, how- 
 ever, is to be preferred, when it can be easily arranged. All roof 
 vents should extend well above the ridge of the building in order 
 
258 
 
 HEATING AND VENTILATING PLANTS 
 
 to prevent down draughts caused by the air currents striking 
 the roof and being deflected into the flues. Vents starting above 
 the basement should in general be covered with a hood of some 
 form to keep the snow and rain from entering them. Where a 
 hood is used, the free opening under it should be made twice 
 the area of the flue. This is done because in case of winds the 
 entire discharge from the flue is in one direction and must pass 
 through only two of the external side openings under the hood. 
 Roof vents starting at the attic floor, or above, should be pro- 
 vided at the bottom with water-tight pans of copper or galvanized 
 
 
 \ i 
 
 
 i 1 
 
 
 
 
 COLD AIR 
 CHAMBER 
 
 
 COLD Ain 
 CHAMBER 
 
 
 CONNECTING 
 
 DUCT 
 
 CONNECTING 
 DUCT 
 
 
 COLD AIR 
 CHAMBER 
 
 COLO AIR 
 CHAMBER 
 
 t r 
 
 t t 
 
 Fie. 183. 
 
 Fig. 184. 
 
 Fig. 183. Arrangement so Vent Flues will "Draw." 
 Fig. 184. Heating Stacks in Indirect Gravity System. 
 
 iron, with suitable drains,' to prevent rain or melting snow from 
 reaching the ceilings below. All vent flues through the roof 
 should be provided with dampers for closing when school is not 
 in session. In order to make the flues "draw" sufflciently in mild 
 or heavy weather, it is necessary to provide some means for 
 warming the air within them to a temperature somewhat above 
 that of the rooms with which they connect. This may be done 
 by placing a small stove, made especially for the purpose, at the 
 base of each flue. With this arrangement it is necessary to carry 
 the vent downward and connect with the flue below the'fetove. 
 
 A much better method, and one equally effective, is to use 
 a wrought-iron chimney stack for the furnace and carry it up 
 between the two vent flues, as shown in section in Fig. ISS. If 
 a separate furnace is provided for each two rooms this arrange- 
 ment may be used in each case. The inlet and outlet openings 
 
DIFFERENT TYPES OF BUILDINGS 259 
 
 from the rooms into the flues are commonly furnished with grilles 
 of iron wire, having a mesh of 2 to 3% inches. Both flat and 
 square wire are used for this purpose, the weight of wire depend- 
 ing upon the size of opening. For ordinary work, 5/16-inch 
 flat wire or % to 3/16-inch square wire may be used, set in 
 light channel-iron frames. In the best class of work, flanges are 
 riveted to the channels and the grilles screwed to wood grounds 
 or frames. 
 
 Dampers in Flues and Vents. — Dampers are commonly placed 
 back of the inlet grilles for closing when the rooms are not in use. 
 Similar dampers should be provided for the vents, although cur- 
 tains with rolls and pull cords, similar to ordinary window shades, 
 are sometimes used for this purpose. The use of dampers at the 
 vent openings is for night closing and for regulation in the case of 
 temporary down draughts or excessive ventilation during high 
 winds. Shut-off dampers should be placed in all cold-air inlets, 
 and doors opening from the basement into the cold-air box should 
 be provided for use at night or when school is not in session. 
 
 Indirect Gravity System, and Modifications. — The indirect 
 gravity system of steam heating comes next in cost of installa- 
 tion. This is adapted to larger buildings than furnace heating 
 because a stack or heater may be placed at the base of each flue 
 and a single boiler made to supply them all, thus doing away 
 with the necessity of carrying several fires. Heating or aspirating 
 coils may be used in place of stoves in the vent flues, thus sim- 
 plifying the system still more. 
 
 Uniform Air Supply. — The gravity system has the fault of not 
 supplying a uniform quantity of air under all conditions of out- 
 side temperature, the same as a furnace, but when properly 
 arranged may be made to give quite satisfactory results during 
 4he greater part of the heating season. The greatest care should 
 be taken to provide an abundant supply of cold air to the heaters, 
 and ducts should be arranged for taking it from at least two 
 sides of the building, or, if possible, from all four sides. When it 
 is taken from four sides, each inlet should be made large enough 
 to supply one-half the amount, or, in other words, any two should 
 give the total quantity required. 
 
 Heating Stacks. — It is often possible to arrange thg flues in 
 groups so that all of the heating stacks may be placed in two or 
 
260 
 
 HEATING AND VENTILATING PLANTS 
 
 more cold-air chambers, depending upon the size of the building. 
 A cold-air trunk line may be run through the center of the base- 
 ment, connecting with the outside on all four sides, and having 
 branches supplying each cold-air chamber. Sometimes the stacks 
 may be placed as shown in Fig. 184, each cold-air room having 
 an outside inlet window and, in addition, a cross-connection with 
 the air chamber upon the opposite side of the building. 
 
 Cold-Air Chamber. — The inlet to each cold-air chamber should 
 be; of sufficient size to supply both stacks. Fig. 185 shows a 
 typical arrangement for a cold-air chamber with heaters supply- 
 ing four rooms, the other flues being/duplicates of those shown. 
 
 »> 
 
 i^w 
 
 MIX DAMPER 
 
 heaAi 
 
 COLD AIR 
 CHAMBER 
 
 , HEATER tf 
 
 AIR CHECKS 
 
 Fig. 185. Typical Airangement of Cold- Air Cliamber. 
 
 and located directly back of them. The cold air is admitted 
 through inlet windows as shown in Fig. 186. The sashes are 
 hinged at the top and close against frames set at a slight angle 
 from the vertical, so that their weight will cause them to shut 
 tightly without the use of levers or weights. A galvanized-iron 
 casing with cloth air checks should be provided to prevent back 
 draughts from carrying the air from the chamber out of doors. 
 The sashes are usually operated by chain-and-pulley attachments 
 as shown. 
 
 Supply and Vent Flues. — These flues may be either of gal- 
 vanized-iron or of brick; the former is preferable on account of 
 its smooth surface, but if brick flues are plastered inside they 
 may be made to give satisfactory results, and are somewhat more 
 durable than iron. 
 
DIFFERENT TYPES OF BUILDINGS 
 
 261 
 
 The opening into the flue from the hot-air space over the 
 heater should be practically the full size of the flue, care being 
 taken to arrange the mixing dampers so that the warm air will 
 enter through the lower part of the inlet registers, as described 
 in a previous chapter. The flue areas for both supply and vent 
 may be practically the same as for furnace heating. 
 
 Dampers. — Mixing dampers are arranged in the flues as indi- 
 cated, and are operated from the rooms with which they con- 
 nect. The chains should be of good size, running over full 
 guarded pulleys and passing into the rooms 3 or 4 feet above the 
 floor through catch plates marked to indicate their use. Ad just- 
 
 Fig. 186. Inlet Windows for Cold Air. 
 
 able dampers should be placed in the flues at some point above the 
 mixing dampers, for regulating the flow of air to the different 
 rooms. Special care is necessary in order to make the mixing 
 dampers tight-closing, and they should be stiffened with light 
 angle iron to hold them in shape. 
 
 Temperature Regulation. — Where mixing dampers are em- 
 ployed it is well to hang dial thermometers at the center of the 
 inlet grilles to indicate the temperature of the entering air. A 
 little experience will then enable one to tell what temperature 
 of air is necessary to warm the room under different outside 
 conditions. Without this, the damper is very apt to be thrown 
 wide open for either hot or cold air as the immediate require- 
 ments may indicate, with the result of either overheating the 
 room on the one hand, or of producing draughts and reducing 
 the air supply below the normal, on the other. For the best re- 
 
262 HEATING AND VENTILATING PLANTS 
 
 suits, a mixing damper should be set in an intermediate position, 
 so that the mixture of warm and cool air will be in the right 
 proportion to maintain an even temperature at all times. 
 
 Pin Radiators. — Cast-iron pin radiators are particularly adapted 
 to this class of work, the " School Pin," having a section about 
 10 inches in depth and rated at 15 square feet of heating sur- 
 face, being used extensively for this purpose. The free air space 
 between the sections is a little over 60 square inches, and an 
 efficiency of at least 550 B. T. U. may be safely counted upon 
 in zero weather with steam radiators of the above form. Assum- 
 ing the same requirements for a standard class room as in furnace 
 heating, calls for 157,000 -=- 550 = 285 sq. ft. of radiating surface 
 in each stack. 
 
 In practice it is customary to allow about 2-90 square feet of 
 surface for each southerly room and 330 square feet for those 
 having a northerly exposure. 
 
 if, however, more generous ventilation is desired," or a lower 
 outside temperature must be provided for, the size of the stack 
 must be increased accordingly. 
 
 Each stack should be divided into two groups in the ratio of 
 1 to i3, with valves in the supply and return, so that the surface 
 may be partly proportioned to the outside temperature. 
 
 More accurate regulation may then be obtained by the use 
 of the mixing damper which is under the control of the teacher. 
 
 Aspirating Coils. — The vent flues should be provided with 
 steam coils for use in mild weather and also in cool weather until 
 an outward flow is well established. It has been found by ex- 
 perience that an efficient coil having from 30 to 40 square feet 
 of heating surface is sufficient for the vent of an ordinary sized 
 schoolroom. One of the best forms of heater for this purpose is 
 made up of Nason tubes screwed into a cast-iron base and placed 
 in an inclined position within the flue just above the vent open- 
 ing from the room, as illustrated in Fig. 83. Each heater should 
 have a separate supply pipe running up from the basement ; these 
 being placed upon an independent line of piping so that the 
 heaters may be used when the rest of the building is shut off. 
 Especial care must be taken to locate the air valves upon the vent- 
 flue heaters at points where they can be reached for adjustment. 
 
DIFFERENT TYPES OF BUILDINGS 263 
 
 A good arrangement is to bring down a. small pipe from each 
 heater and place the air valves just back of the grille in such a 
 manner that they may be easily reached by means of a screw- 
 driver or key. Valves connected in this way should be dripped 
 to the basement. 
 
 A separate boiler of small size for supplying the vent flue 
 heaters is often provided for use in spring and fall before the 
 main heating boilers are fired up. 
 
 Air Rotation. — In any system of indirect heating, provision 
 should be made for air rotation by means of doors opening from 
 the basement into the cold air-chambers. At night or when 
 school is not in session the outside cold-air windows should be 
 closed and the rotation doors opened. Doors from classrooms 
 into corridors, and from corridors into basement stairways, 
 should also be opened to allow a complete rotation of air through 
 the heaters for warming without ventilation. 
 
 Foot Warmers, so called, should be placed under the first-floor 
 corridor near the entrances. These consist of indirect stacks con- 
 taining from 80 to 100 square feet of heating surface placed 
 at the basement ceiling with large registers above them. A long 
 narrow register, f roni ,12 to 18 inches in width, will accommodate 
 more pupils at the same time than one of the same area more 
 nearly square. These heaters are sometimes made to take their 
 air directly from the basement through large openings in the bot- 
 toms of the casings, but it is better to connect them with the out- 
 side air supply and thus furnish ventilation for the corridors. 
 
 Small Rooms and Basement Rooms. — Small rooms, such as 
 teachers' rooms, toilet and coat rooms, are best heated by direct 
 radiation, but should be provided with vent flues. The radiator 
 sizes may be computed by the methods already given. In base- 
 ment rooms it is usually necessary to place the heating coils near 
 the ceiling in order to bring them above the water-line of the 
 boiler. When this is done it is necessary to increase the surface 
 from 30 to 50 per cent above that computed, as coils placed in 
 this position are less efficient than when near the floor. 
 
 Combined Direct and Indirect Heating. — One of the disadvan- 
 tages of indirect heating for schoolhouse work is the delivery of 
 the heat through a single inlet, and that often located in an in- 
 
264 HEATING AND VENTILATING PLANTS 
 
 side wall. This leaves the windows unprotected and the seats 
 near the outer walls are exposed to draughts in cold and windy 
 weather. This defect may be overcome by proportioning the 
 indirect stacks for ventilating purposes only, and warming the 
 room independently by means of direct coils placed along the 
 walls beneath the windows. 
 
 Area of Stack Surface. — Indirect stacks, when used in this 
 manner, should contain about 215 square feet of heating surface 
 for each room. If we assume 50 pupils per room, with an air 
 supply of 30 cubic feet per minute each, we shall have 50 X 30 
 X 60 = 90,000 cubic feet per hour, and 90,000 X 1.3 = 117,000 
 B. T. U., from which 117,000 ^ 550 = 213 square feet of heat- 
 ing surface required. 
 
 It is evident that for much of the time this amount of heating 
 surface will be sufficient for both warming and ventilating and, if 
 mixing dampers are provided, the direct surface will be needed 
 only in the coldest weather and may be operated by hand. Where 
 the first cost must be kept as low as possible, this arrangement 
 may be used, but if the most satisfactory results are desired at 
 an increased cost, the mixing dampers may be used for regulat- 
 ing the temperature of the air supply, and automatic control 
 applied to the direct coils. In addition to this the indirect stacks 
 should be divided into sections and valved as already described. 
 
 Area of Direct Surface. — The direct surface may be computed 
 by the methods previously given or by a simple rule which has 
 been found to give satisfactory results in a large number of 
 buildings of this class: 
 
 Rule. — Divide the outside wall surface by 12, and the glass 
 surface by 5 ; add the quotients, and the result will be the square 
 feet of heating surface required for wall coils. If cast-iron 
 radiators are to be used in any of the rooms the surface com- 
 puted by the above rule should be multiplied by 1.3. 
 
 These sizes are for rooms having a southern exposure; for 
 other exposures, multiply by the factors already given in Chapter 
 II. for this purpose. If the building has a cold attic, the heating 
 surface in rooms on the upper floor should be increased about 15 
 per cent. Where a building is in a very exposed location, or 
 
DIFFERENT TYPES OF BUILDINGS 265 
 
 where the temperature frequently drops below zero, the factors 
 10 and 4 may be used in place of 12 and 5. 
 
 Location of Direct Radiators. — The direct radiation is best 
 made up in the form of circulation coils and placed along the 
 outer walls beneath the windows. This supplies the heat where 
 most needed, and does away with the tendency to draughts. 
 Where direct radiation is used, the quantity of heat supplied is 
 not affected by varying wind conditions, as is the case in indirect 
 heating. Although the air supply may be reduced at times, the 
 heat quantity is not changed. Circulation coils are usually made 
 up of 1%^-inch pipe screwed into branch tees and supported upon 
 hook plates attached to the wall. It is common in schoolhouse 
 work to run the pipes around the two outside walls in corner 
 rooms, making the steam connection at one end and the return at 
 the other. Coils of this form should have a grade of about 1 inch 
 in 20 feet toward the return end in order to secure proper drain- 
 age and quietness of operation. 
 
 Pipe Connections. — As the classrooms are usually superposed 
 on the different floors, supply risers may be carried up and the 
 coils on each floor supplied from the same riser. The returns are 
 sometimes connected with a common return in a similar manner. 
 Where this is done they should be dropped through the floor and 
 the connection made with the vertical, drop at the ceiling of the 
 room below. A check valve should be placed in each connection 
 to prevent the steam from one coil backing into another through 
 the return when it is first turned on. This method of connection 
 and the proper location of air valve are shown in Fig. 187. A 
 better arrangement is to carry a separate %-inch return from each 
 coil to the basement, and connect with the main horizontal return 
 below the water-line of the boiler ; this seals each connection and 
 makes each coil independent of the others. When the connections 
 are made in this manner, the air valves may be placed in the re- 
 turn drops just below the basement ceiling instead of on the coil. 
 
 Special Conditions. — Sometimes the rooms are so arranged that 
 the heating surface must all be placed upon a single wall. In this 
 case a "return bend" or "trombone" coil should be used instead 
 of a branch coil, to allow for the expansion of the pipes. Over- 
 head coils in basement rooms are usually of the "miter" form laid 
 
266 
 
 HEATING AND VENTILATING PLANTS 
 
 on the side and suspended about 18 inches below the ceiling ; they 
 are less efficient than when placed nearer the floor, as the warm 
 air stays at the ceiling and the lower part of the room is likely to 
 remain cold. They are only used when wall coils or radiators 
 would be in the way of fixtures, or when they would come below 
 the water-line of the boiler if placed near the floor. The pipe 
 sizes for both supply and return may be taken from the tables 
 already given. 
 
 Fan Systems. — The most satisfactory method of ventilating 
 buildings having six or more rooms is by means of a fan or 
 blower. With this system the air supply is practically constant 
 
 3i-y 
 
 JjAtRV. 
 
 j 
 
 ^ 
 
 Fig. 187. Pipe Connections and Location ol Air Valve. 
 
 under all usual conditions of outside temperature and wind action. 
 This gives it a decided advantage over natural gravity methods 
 which are affected to a greater or lesser degree by outside condi- 
 tions as already stated. 
 
 Plenum Method. — In the plenum method, the air is forced 
 into the building after being passed through a heater for 
 raising it to the desired temperature. The heater is usually made 
 up in sections so that steam may be admitted to or shut off from 
 any section independently of the others, and the temperature of 
 the air regulated in this manner. Sometimes a by-pass damper is 
 employed, so that part of the air will pass through the heater and 
 part around or over it; in this way the proportions of cold and 
 heated air may be so adjusted as to give the required temperature 
 to the air entering the rooms. These forms of regulation are 
 common where a blower is used for warming a single room, as 
 
DIFFERENT TYPES OF BUILDINGS 267 
 
 in the case of a church or hall ; but where several rooms are to be 
 warmed, as in a schoolhouse, it is customary to use the main or 
 primary heater at the blower for warming the air to a given tem- 
 perature, somewhat below that which is actually required, and to 
 supplement this by placing secondary coils or heaters at the bases 
 of the different fiues, or by the use of direct radiation in the 
 rooms. By means of these arrangements the temperature of each 
 room can be regulated independently of the others. The so-called 
 double-duct system is sometimes employed for this purpose. In 
 this case two ducts are carried to the base of each flue, one con- 
 veying hot air and the other cool or tempered air. A mixing 
 damper is provided at this point for regulating the quantity of 
 each and thus producing the desired temperature. 
 
 Size of Ducts. — With the blower type of fan the size of the 
 main ducts may be based on a velocity of from 1,000 to 1/300 feet 
 per minute, and the branches on a velocity of 800 to 900 feet 
 per minute, and as low as 600 to 800 when the pipes are small. 
 The velocity in the vertical flues may be from 600 to 700 feet per 
 minute, although the lower velocity is preferable. The sizes of the 
 inlet registers should be such that the velocity of the entering air 
 will not exceed 350 to 400 feet per minute. The velocity between 
 the inlet windows and the heater may be from 800 to 1,000 feet, 
 provided the distance is short. 
 
 Diffusers. — When the air is delivered through a register at the 
 high velocities mentioned, some means must be provided for 
 diffusing the entering current in order to prevent disagreeable 
 draughts. This is usually accomplished by the use of deflecting 
 blades of galvanized iron set in a vertical position and at varying 
 angles, so that the air is thrown toward each side as it issues from 
 the register. The proper angle for the blades depends upon the 
 position of the register, whether in the corner of a room or in a 
 central position. 
 
 Fig. 188 shows a diffuser of this kind for hanging in front of 
 a register or grille. In some cases the diffuser is made to form 
 a part of the inlet construction, the grille being omitted. 
 
 Vent Flues. — The sizes of the vent flues should be about the 
 same as for a gravity system; that is, 6 square feet for a 
 standard classroom, and in the same proportion for smaller rooms. 
 
268 HEATING AND VENTILATING PLANTS 
 
 In some buildings large vent flues are used, extending from the 
 basement through the roof and are connected with two or more 
 rooms on each floor. In cases of this kind the cold air is apt to 
 settle down the flue at night, even though a damper is provided, 
 and flow into the rooms. To prevent this, light checks of gos- 
 samer cloth are sometimes used, consisting of strips about 5 inches 
 in width strung on wires and fastened to the backs of the vent 
 grilles. The pressure in the room due to the fan will cause the 
 checks to open outward and allow, the air to pass by them, but 
 a reversal of the current will close them tightly and prevent the 
 inleakage of cold air. An arrangement of this kind is shown in 
 Fig. 189. 
 
 Fig. 188. Oifiusei for Inlet Register. 
 
 Vent-flue heaters are not usually required in connection with a 
 fan system, as the action of the fan is sufficient to supply the 
 required quantity of air at all times without the aspirating effect 
 of the vent flues. 
 
 Main Heater. — The usual form of heating coil as made by the 
 manufacturers of blowers is better adapted to hot-blast heating 
 where high temperatures of air are required than to schoolhouse 
 ventilation which calls for large volumes at moderate tempera- 
 tures. A heater for ventilating purposes does not need to be 
 more than 8 or 10 pipes deep, so, if this type is employed, large 
 sections should be used and a sufficient number placed side by side 
 to make up the required amount of radiating surface for a heater 
 
DIFFERENT TYPES OF BUILDINGS 
 
 269 
 
 of this depth. The form shown in Fig. 152 is particularly adapted 
 to buildings where a large volume of air is to be supplied, and the 
 space available for the heating apparatus is somewhat limited. 
 
 In designing a system of ventilation for a school building the 
 main heater is usually made large enough to raise the total air 
 supply to a temperature of 70 to 75 degrees in the coldest weather. 
 The heat for warming is then provided by a separate system of 
 direct radiation placed in the rooms, or by indirect stacks at the 
 bases of the flues. 
 
 Fig.. 1 89. To Prevent Cold Air Entering Rooms Through Vent Flues. 
 
 Arrangement with Cast-iron Heater. — Fig. 190 shows a typical 
 arrangement of fan and overhead cast-iron heater. The air is 
 drawn through the inlet windows, as shown, and passes into the 
 space above the heater; it is then drawn through it and into the 
 fan, from which it is discharged into the main distributing duct 
 at the basement ceiling. The bottom of the heater should be at 
 least 30 inches above the water line of the boiler so that the con- 
 densation will easily flow back by gravity through a check valve.- 
 
 This is one of the simplest arrangements of fan and heater, as 
 it does away with the use of pumps and traps for returning the 
 condensation to the boiler. When this system is used, an engine 
 with a large cylinder should be employed so that the steam pres- 
 sure need not exceed 15 or 18 pounds, and the whole system, in- 
 
270 
 
 HEATING AND VENTILATING PLANTS 
 
 eluding the direct surface, may be run upon the same pressure. 
 This arrangement is adapted to all buildings of small and medium 
 size where the heater can be placed at a sufficient height above 
 the boilers. 
 
 For large high schools this form of cast-iron heater becomes 
 somewhat cumbersome on account of its size, and an exceedingly 
 large engine would be required for running the fan on a low steam 
 pressure. In this, case it is best. to carry a boiler pressure of 35 or 
 40 pounds, and reduce to about 10 pounds for the main heater, 
 and 3 to 5 pounds for the supplementary or direct radiation. The 
 main heater is usually made of wrought-iron pipe or "Vento" 
 sections in the case of large buildings, being more compact for a 
 given heating surface and thus occupying less space. 
 
 Fig. 1 90. Typical Arrangement of Fan and Orerhead Heater. 
 
 Arrangement for Pipe Heater. — Fig. 191 shows a typical ar- 
 rangement for a pipe heater, with a fan discharging into an un- 
 derground airway. As heaters of this type are made to rest upon 
 foundations near the floor, the lower portion is below the water 
 line of the boilers, and it becomes necessary to return the con- 
 densation by the use of a pump or return trap. 
 
 Return of Condensation. — ^The pumps used for returning the 
 condensation to the boilers are automatic in action. They are 
 usually combined with a receiving tank of wrought or cast iron 
 mounted upon the same foundation. 
 
 In buildings of considerable size it is customary to use a 
 wrought-iron tank somewhat larger than is usually furnished 
 for this purpose, and to connect it with two duplex pumps, each 
 of sufficient capacity to do the entire work. In this arrangement 
 a pump-governor is often employed instead of a float in the tank. 
 
DIFFERENT TYPES OF BUILDINGS 
 
 271 
 
 When two pumps are provided they are generally used alter- 
 nately, changing once a week or so, thus keeping them both in 
 working order. If one is allowed to remain idle too long at one 
 time, it is apt to become rusty or gummed with oil inside. 
 
 Where different parts of the system are run on different pres- 
 sures, it is necessary to discharge the condensation from each 
 into the receiving tank through a trap * the tank being connected 
 with atmospheric pressure through a vapor pipe carried to the 
 top of the building. Overhead returns and the condensation from 
 the main heater are trapped directly into the receiver, while, in 
 case of the direct or supplementary heating system, it is desirable 
 
 Fig. 191. Typical Airangement for Pipe Heater. 
 
 to seal the long horizontal return pipes in order to ensure quiet- 
 ness of operation. This is accomplished by establishing a "false 
 water-line" at such a height as desired by means of a "water- 
 line trap." 
 
 Fig. 193 shows a common arrangement for the return connec- 
 tions in a combination system of this kind. 
 
 The traps for draining the different systems discharge into a 
 vented receiver, as shown, and the water is pumped back to the 
 boilers automatically. 
 
 Valve Connections. — Part of the sections of the main heater 
 should be valved for taking either exhaust or live steam as pre- 
 viously described, and a back-pressure valve opening at about 
 5 pounds should be placed in the outboard exhaust pipe, as shown. 
 
272 
 
 HEATING AND VENTILATING PLANTS 
 
 This acts as a relief, and opens when the pressure in the exhaust 
 sections rises above the point for which it is set. If it is de- 
 sired to run the fan in mild weather when no heat is required, the 
 back-pressure valve should be opened and all of the steam ex- 
 hausted outboard. 
 
 r 
 
 In case indirect supplementary heaters are used at the bases 
 of the flues, the surface may be reduced to about one-half that 
 required for direct heating. This is because the higher velocity 
 of the air passing over the heaters when placed in this position 
 doubles their efficiency. Heaters of wrought-iron pipe are some- 
 times supported in the flues, but more commonly pin radiators 
 are hung at the basement ceiling and encased in galvanized iron. 
 
 WATEH UNE TRAP 
 
 WATER LINE 
 
 MAIN RETURNS 
 
 Fig. 192. Special Arrangement for Return of Condensation. 
 
 Temperature regulation may be obtained by placing mixing or 
 by-pass dampers at the heaters, or by the use of automatic supply 
 and return valves, which shut off and turn on the steam as 
 required. 
 
 In all cases where a fan is used for ventilation, a dial ther- 
 mometer of large size or a special bulb thermometer with mag- 
 nifying prism should be connected into the main duct at a con- 
 venient point near the fan for indicating the temperature of the 
 air supplied to the rooms. 
 
 Ventilation of Toilet-Rooms and Hoods. 
 
 The ventilation of the toilet-rooms of a school building is a 
 matter of the greatest importance. The first requirement is that 
 the air movement shall be into these rooms from the corridors 
 
DIFFERENT TYPES OF BUILDINGS 273 
 
 instead of outward. To obtain this result it is necessary to pro- 
 duce a slight vacuum within, and this cannot well be done if 
 fresh air is forced into them. 
 
 Exhaust Ventilation. — One of the most satisfactory arrange- 
 ments is to provide exhaust ventilation only, and to remove the 
 greater part of the air through local vents connecting with the 
 fixtures. 
 
 There are different ways of doing this; one being to carry a 
 galvanized-iron duct back of the fixtures, having a sectional area 
 of about 12 square inches for each one, and connecting with the 
 local vents by short branches. 
 
 A better arrangement consists of a closed chamber of slate or 
 marble having the local vents connected directly with it. A duct 
 is taken from the top of the chamber and connected with a 
 heated flue or exhaust fan. 
 
 In the case of grammar schools or small high schools a loop 
 of 2-inch pipe from 30 to 40 feet high within the flue will usually 
 furnish sufficient heat to produce the necessary draught. Where 
 it is convenient, a heater of open construction containing 30 or 40 
 square feet of heating surface and placed in the flue just above 
 the connection from the fixtures will be found somewhat more 
 effective. 
 
 Ventilation by Fans. — In large buildings an exhaust fan is 
 usually connected with the sanitary fixtures, having a sufficient 
 capacity to discharge from 10 to 12 cubic feet of air per fixture 
 per minute. This gives a velocity of 135 to 150 feet per minute 
 through a pipe 4 inches in diameter, which is ample to carry 
 ofif all odors and also provide sufficient ventilation from the 
 room. Disk fans are generally employed for this purpose, 
 although steel plate exhausters are advisable if the flues are long 
 or restricted in area. Data for the size and speed of fan will be 
 found in a previous chapter. 
 
 Small Toilet-Rooms having a single fixture may be ventilated 
 entirely through the local vent, the same being connected with a 
 
 5 or 6-inch vertical pipe containing a loop of %-inch steam pipe 
 
 6 or 8 feet in height. This vent pipe may be carried up inside 
 the vent flue from a class room to a point 12 or 15 feet above the 
 last register opening, and may then discharge into the general 
 
274 HEATING AND VENTILATING PLANTS 
 
 ventilation. When extended to this height there is very little 
 danger of odors being carried downward into the rooms by back 
 draughts. 
 
 Chemical Hoods are either connected with a hot flue or are 
 ventilated by means of a fan. Where there are only three or four, 
 a gas jet placed in the top of each, just below the outlet will often 
 give sufficient draught. When there is a larger number of 
 hoods to be ventilated, it is better to connect them with a fan of 
 sufficient capacity to change the entire contents of all the hoods 
 five or six times per minute. A fan for this purpose should be 
 provided with copper blades and the connecting ducts should be 
 either coated with asphaltum or made of tile. Fig. 193 shows a 
 good form of construction for a chemical hood. A is the fume 
 closet, provided with a sliding sash in front, which is prevented 
 from closing entirely by a stop C. 5 is a chamber common to 
 all of the hoods and connects with a flue at the back as shown. 
 
 The path of the air currents is indicated by the arrows. 
 
 The bottoms of the fume closets are covered with slate slabs, 
 and each is provided with a cupboard and shelf beneath. 
 
 Hospitals, Asylums, Etc. 
 
 The best system for heating and ventilating a hospital depends 
 upon the character and arrangement of the buildings. It is 
 desirable in all cases to do the heating from a central plant 
 rather than to carry fires in the separate buildings, both on 
 account of economy and cleanliness. 
 
 Cottage Hospitals. — In the case of small cottage hospitals with 
 two or three buildings placed close together, indirect hot water 
 affords a desirable system for the wards, with direct heat for the 
 other rooms ; but where there are several buildings, and especially 
 if these are some distance apart, it becomes necessary to substitute 
 steam, uriless the water is pumped through the mains. For large 
 city buildings, a fan system is always desirable. If the building 
 is tall compared with its ground area, so that the horizontal sup- 
 ply ducts will be comparatively short, the double-duct system may 
 be used with good results. Where the rooms are of good size 
 and the number of supply flues limited, the use of supplemen- 
 tary heaters at the bases of the flues makes a satisfactory arrange- 
 
DIFFERENT TYPES OF BUILDINGS 
 
 275 
 
 merit. Direct radiation is not usually placed in the wards, unless 
 of special construction, as it offers too great an opportunity for 
 the accumulation of dust in places which are difficult to reach. 
 
 The usual ward building of a modern cottage hospital generally 
 contains a main ward having from 8 to 12 beds, and a number 
 
 Fig. 193. Chemical Hood. 
 
 of private rooms with one bed each. In addition to these there 
 are a diet kitchen, duty room, toilet rooms, bathrooms, linen 
 closets, and lockers. 
 
 Radiating Surface. — For moderately sheltered locations 30 
 square feet of indirect steam radiation has been found sufficient 
 in zero weather for a single ward with one exposed wall and a 
 single window, when upon the south side of the building. For 
 
276 HEATING AND VENTILATING PLANTS 
 
 northerly rooms, 40 square feet should be used. In exposed loca- 
 tions the heaters may be made 40 and 50 square feet for southerly 
 and northerly rooms respectively. Standard pin radiators, rated 
 at 10 square feet of heating surface per section, are com- 
 monly used for this purpose. In case hot water is used, the same 
 number of sections of the deep-pin pattern, rated at 15 square 
 feet each, may be employed, making a total of 45, and 60 square 
 feet per room. For corner rooms having two exposed walls and 
 two windows, the amount of radiation should be increased about 
 50 per cent over that given above. 
 
 In the case of the main wards, each bed should be treated as a 
 single room with one exposed wall unless the ratio of wall and 
 window surface per bed is greatly out of proportion. 
 
 Air Supply. — The warm air in both large and small rooms 
 is usually admitted through wall registers placed just below the 
 windows. One of the most satisfactory arrangements for the 
 cold-air supply to the heaters beneath the main ward is to use the 
 whole basement as a cold-air chamber, with inlets upon both sides. 
 The heating stacks are suspended at the ceiling and provided with 
 casings having open bottoms and taking their air directly 
 from the basement. The air supply to the heaters for the private 
 wards may be taken from the cold-air chamber under the main 
 ward or they may have separate inlets from out of doors, as is 
 most convenient. In any case there should be at least 3 square 
 inches area in the ducts for each square foot of radiation in the 
 heaters. The steam mains and branches to the stacks are left 
 uncovered, and so supply enough heat to produce a layer of warm 
 air at the ceiling, and thus prevent the floor above from becoming 
 chilled. Fig. 194 shows a stack arranged in the manner described. 
 The cold-air inlets to the basement air chamber should be fur- 
 nished with cloth checks, and the total opening required should be 
 provided on each side of the building. 
 
 It is common to provide from 80 to 100 cubic feet of air per 
 minute per patient in ordinary wards, and from 100 to 120 cubic 
 feet in contagious wards. 
 
 The quantity of heat required per room may be computed by 
 first finding that necessary for ventilation, and adding to it the 
 amount required to offset that lost by transmission and leakage. 
 
DIFFERENT TYPES OF BUILDINGS 
 
 277 
 
 Air Ducts. — The warm-air ducts exposed in the basement, and 
 the back and sides of the flues running up in the outside walls 
 of the building should be covered with an inch of good insulating 
 material such as seaweed quilting or asbestos air-cell with the 
 spaces running cross wise. In either case, that portion exposed 
 in the basement should be covered with canvas. The area of the 
 warm-air flues should be about 100 square inches for each bed, 
 a flue 6 inches by 16 inches being commonly used in single rooms. 
 The wards are usually provided with fireplaces, and these may be 
 utilized for the discharge ventilation. The vent flues should not 
 be less than 8 inches by 12 inches for single wards, and the 
 
 
 -^ J- 
 
 . ^^ 7 
 
 CASING OPEN AT BOTTOM 
 
 Fig. 194. Special Form of Heating Stack. 
 
 equivalent for each bed in the large ward. Each flue used for 
 this purpose should be provided with a loop of 1-inch steam pipe 
 10 or 12 feet high, for producing a draught. This may be brought 
 into the flue above the throat of the fireplace, and if made of 
 extra heavy pipe will not be injured by the heat from the fire. 
 If there is a fireplace in the large ward it should be of ample 
 size and provided with an aspirating coil. In wards containing 
 10 or 12 beds good results have been obtained by providing a 
 fireplace at one end, having a flue area of about 4 square feet, 
 with an aspirating coil containing 20 square feet of heating 
 surface, in the form of a return-bend coil placed in an inclined 
 position on its side across the flue. Another vent of the same 
 
278 HEATING 'AND VENTILATING PLANTS 
 
 size should be provided at the other end of the ward, preferably 
 near the ceiling; this is especially for summer use, but may be 
 used at other times when the fireplace does not prove sufficient. 
 Adjustable shut-off dampers should be placed in each of the 
 vents and provided with chains for operating from the floor. 
 Small wards having no fireplace should have a galvanized- 
 iron vent flue with a connecting register near the floor. Other 
 rooms such as diet kitchens, bathrooms, etc., should have vent 
 flues of about 1 square foot area each. All vents, except fire- 
 places, should be gathered in the attic space and connected with 
 one or more main shafts passing through the roof. The roof 
 ventilators. may have an area of from 0.7 to 0.8 of all the flues 
 connecting with them, and should be provided with suitable 
 cowls or heads, with shut-off dampers which can be operated from 
 the floor beneath. The vents from the small rooms should be 
 provided with steam loops, the same as the fireplace flues. 
 
 Modern hospital practice makes free use of natural or window 
 ventilation, but as this is confined largely to flushing out the 
 wards at more or less frequent intervals, a system of artificial 
 ventilation must be provided for regular use. 
 . Miscellaneous Heating. — Other rooms than wards are usually 
 heated with direct radiators, the sizes of which may be computed 
 in the same manner as for dwelling houses. The operating wing 
 may be treated in a similiar manner to the wards. Sufficient air 
 should be provided in the operating, etherizing and recovery 
 rooms to change the entire contents at least ten times per hour. 
 The radiating surface for heating and ventilating may be com- 
 puted by the methods already given, allowing an efficiency of 450 
 B. T. U. for steam and 340 B. T. IT. for water, under these 
 conditions. 
 
 The large window and skylight in the operating room are usually 
 made with double sashes, with one or two lines of l^-inch 
 pipe carried around the perimeter, between them. A high-speed 
 electric fan, 13 or 16 inches in diameter, for a small operating 
 room, placed near the ceiling and discharging into an outboard 
 vent flue is very useful for clearing the room of ether during or 
 after an operation. 
 
 Steam tables for the kitchen, sterilizers, and laundry machinery 
 require a higher pressure than is necessary for heating. 
 
DIFFERENT TYPES OF BUILDINGS 279 
 
 Boiler Arrangement. — If the grade of the different buildings is 
 such that the entire heating system can be run with a gravity 
 return to the boilers, it is best to do so and employ a separate 
 high-pressure boiler for other puirposes. A laundry mangle 
 requires from 60 to 80 pounds pressure to operate successfully; 
 sterilizers 25 to 30 pounds, and steam tables 10 to 15, although 5 
 pounds is often sufficient for this purpose if the supply pipes are 
 made of ample size. A good arrangement for small plants, is to 
 provide sufficient boiler power for warming and ventilating pur- 
 poses, and run at a pressure of 3 to 5 pounds. In addition to this 
 a small high-pressure boiler carrying 70 or 80 pounds should be 
 furnished for laundry work and water heating. 
 
 Steam at ,25 or 30 pounds pressure for sterilizers and steam 
 tables may be obtained by the use of a reducing valve, and the 
 small amount of condensation trapped to the sewer. 
 
 In the case of large institutions the entire boiler plant may be 
 run at high pressure, and reduced as required for the different 
 purposes. When this is done, each reducing valve must have its 
 corresponding trap in the return, discharging into a vented re- 
 ceiver from which the condensation is pumped back to the 
 boilers automatically. When the buildings are much scattered, 
 steam at 30 to 30 pounds pressure may be carried in the mains 
 and each building provided with its own reducing valve and trap ; 
 the trap from each building discharging into a common main 
 leading to a vented receiver. With systems like the above, it is 
 necessary to maintain a sufficient pressure day and night to 
 operate the pumps, or the returns will become filled with water. 
 High pressure steam for laundry and other purposes is supplied 
 through a separate line as already described. 
 
 The necessary boiler power for heating water for laundry, 
 kitchen, and bathing purposes may be taken as 1 horse power 
 for each five inmates, including both patients and attendants. 
 
 Return Connections. — When the buildings differ in elevation, 
 it is necessary to establish a false water-line in each by the use 
 of a water-line trap discharging into a vented receiver located in 
 the boiler room. 
 
 Sometimes the buildings can be grouped so that one v^ater-line 
 trap will care for several. Each building should be separately 
 connected with the mains, and provided with valves so it can be 
 
280 
 
 HEATING AND VENTILATING PLANTS 
 
 shut off in case of accident or repairs. An arrangement for 
 making the return connections without the use of a receiver is 
 shown in Fig. 195. In this case all traps discharge into a return 
 main which is vented through the balance pipe of a pump regu- 
 lator connected into the outboard exhaust. 
 
 This method of making the return connections is only adapted 
 to cases where all of the returns are under practically the same 
 pressure. Otherwise there will be danger of water hammer when 
 traps under a higher pressure discharge into the cooler water of 
 the main return. When the different traps discharge into a vented 
 receiver above the water line, all trouble of this kind is avoided. 
 
 Fig. 195. Return Connections without Use of a Receiver. 
 
 The exhaust from the laundry engine should be turned into 
 the drying coils, with a connection for admitting high-pressure 
 steam through a reducing valve, as may be necessary to make 
 up the full amount required. The trap on the return should be 
 arrange so as to discharge either to the receiving tank or sewer 
 according as live or exhaust steam is used. Fig. 196 shows a 
 typical arrangement for laundry piping. 
 
 Temperature of Air. — In large buildings where the double-duct 
 system is employed a certain proportion of the air is heated to 
 the maximum required to maintain the desired temperature in 
 the most exposed rooms, while the temperature of the other 
 rooms is regulated by mixing with the hot air a sufficient volume 
 of cool or tempered air at the bases of the different flues. This 
 result is best accomplished by designing a hot-blast apparatus 
 
DIFFERENT TYPES OF BUILDINGS 
 
 281 
 
 SO that the air shall be drawn through the primary or tempering 
 heater, and then forced through the secondary heater, a by-pass 
 damper being provided in connection with the latter. 
 
 The temperature to which the air must be raised to warm the 
 coldest rooms may be determined as follows : 
 
 Select one having the greatest wall exposure compared with 
 the number of occupants and first compute the quantity of heat 
 necessary to raise the required volume of air for ventilation from 
 zero to 70°. Next determine the heat loss by transmission and 
 leakage thTough walls and windows, and find to what final tem- 
 
 11 
 
 o w 
 
 ^ BACt(.PRE8SURe 
 Q — VALVE 
 
 Id O 
 
 £ O 
 
 HIGH FREBBURE 
 
 :H 
 
 -jS— iO— Sl 
 
 •J BY-PASS T 
 —ft W- 
 
 MP I jj' l 
 
 ^gt 
 
 •n SEWER 
 
 Fig. 196. Airangement of Laundry Piping. 
 
 perature the air must be raised in order to furnish this additional 
 quantity of heat. This process can best be shown by working a 
 practical example. 
 
 Example. — The air supply to a ward is 13,000 cu. ft. per hour, 
 and the heat loss through walls and windows is 10,000 B. T. U. 
 per hour. To what temperature must the entering air be heated 
 to warm the room, and what will be the total heat required for 
 both heating and ventilation? 
 
 The heat required for ventilation, that is, for raising the air 
 supply from zero to 70°, is 
 
 12,000 X 1.3 = 15,600 B. T. U. 
 and the total heat required is 15,600 + 10,000 = 35^600 B. T. U. 
 
282 HEATING AND VENTILATING PLANTS 
 
 The question now becomes, to what temperature will 34,000 
 B. T. U. raise 13,000 cu ft. of air? 
 This may be found by the formula: 
 
 B. T. U. X 55 ^. . 
 — V-. — J — - — 7 — — = Rise m temperature, 
 cubic feet of air '^ 
 
 Substituting the quantities in the problem in the above, we have 
 
 25,600 X 55 
 
 13,000 
 
 = 117° F. 
 
 which is the temperature to which the above quantity of air must 
 be raised in zero weather. 
 
 Referring to Tables LV. and LVL, we find that with steam at 
 5 pounds pressure the heater must be 16 pipes deep in order to 
 raise the entering air to this temperature in zero weather, and 
 that the efficiency under these conditions will be about 1400 
 B. T. U. per square foot of surface per hour. The heater must 
 then be proportioned to warm, say, 80 per cent, of the entire air 
 supply of the building up to this temperature. 
 
 In designing a system of this kind the tempering coil should 
 be of sufficient capacity to raise the temperature of the air to 
 about 60°, and the secondary heater then proportioned to raise 
 it to the desired maximum. When this arrangement is used the 
 first heater may be made 7 or 8 pipes deep and the second of 
 sufficient depth to bring the total up to the number required. 
 
 In the present case, both heaters would be made 8 pipes deep. 
 The total heating surface may be computed as though it were 
 all placed in one heater. Each unit should have practically the 
 same free area for the passage of air through it, although only 
 a part will pass through the secondary heater. 
 
 Arrangement of Apparatus. — Fig. 197 shows a typical arrange- 
 ment of fan and heaters, and Fig. 1&8 a common form of mixing 
 damper for use at the bases of the flues. In the best equipped 
 plants, graduated mixing dampers, controlled by thermostats, are 
 used in place of hand dampers. 
 
 When supplementary heaters are used at the bases of the flues 
 a main or primary heater of sufficient size should be provided to 
 raise the air to 60° or 65°, and the secondary heaters pro- 
 portioned the same as in schoolhouse work; that is, made one 
 
DIFFERENT TYPES OF BUILDINGS 
 
 283 
 
 half as large as direct radiators would need to be if placed in the 
 rooms. 
 
 Fig. 199 shows a layout where the upper part of the basement 
 corridor is used for an air-duct, with secondary heaters at each 
 side. 
 
 Fig. 197. Arrangement of Fan and Heaters. 
 
 
 VE 
 
 Fig. 198. Mixing Damper at Base of Flues. 
 
 Exhaust Fans. — In large hospitals, where a supply fan is used, 
 an exhaust fan of either the disc or steel-plate type is usually 
 employed for removing the air from the building instead of 
 relying upon natural draught. This makes it possible to use 
 smaller vent flues and results in the saving of valuable space, 
 which is always a matter of importance in large city buildings. 
 The exhaust fan is generally proportioned to remove about three 
 fourths of the air supplied to the building, leakage being de- 
 
284 
 
 HEATING AND VENTILATING PLANTS 
 
 pended upon to care for the remaining portion. The flues may 
 be connected with centrally located chambers in the roof or attic 
 space by means of galvanized-iron ducts, and one or more fans, 
 provided for discharging the air outboard through properly pro- 
 tected vents. 
 
 Direct-connected electric motors are used for driving the fans 
 whenever a direct current is available; otherwise, belted motors 
 must be used. 
 
 SAME 
 
 ARRANGEMENT 
 
 HERE 
 
 Fig. 199. Air Duct witli Heaters on Each Side. 
 
 Insane Asylums are necessarily heated by hot air and a fan is 
 generally employed for this purpose. The flues are carried up in 
 the briek walls and should, if possible, be provided with terra- 
 cotta linings. The air inlets to the rooms should have registers of 
 the lock pattern. Very good results may be obtained by grouping 
 the rooms according to the outside exposure and furnishing air 
 at the same temperature to all of the rooms in one group. About 
 three complete changes of air per hour are allowed for the 
 rooms, and it is heated at the fan to a temperature sufficient to 
 warm those which are the least exposed. Supplementary or re- 
 heaters of proper size are placed in the branches leading to the 
 more exposed sections of the building for use as required. The 
 whole apparatus is operated from the basement and is under the 
 direct control of the engineer. 
 
DIFFERENT TYPES OF BUILDINGS 285 
 
 Churches. 
 
 Churches may be warmed by furnaces, indirect stearti,. or by 
 means of a fan. 
 
 Furnace Heating.— For small buildings, the furnace is more 
 commonly used. This apparatus is the simplest of alirand is 
 comparatively inexpensive. Heat may be generated quickly, and 
 when the fires are no longer needed they may be allowed to go 
 out without danger of damage to any part of the system from 
 freezing. It is not usually necessary to make the heating ap- 
 paratus large enough to warm the entire building at one time to 
 70° with frequent change of air. If the building is thoroughly 
 warmed before occupancy, either by rotation or by a slow upward 
 movement of outside air, the chapel or Sunday-school room 
 may be shut off vmtil near the close of the service in the audi- 
 torium, when a portion of the warm air may be turned into it. 
 When the service ends, the switch damper may be opened wide 
 and all of the air discharged into the Sunday-school room. The 
 position of the warm-air registers will depend somewhat upon 
 the construction of the building, but it is well to keep them near 
 the outer walls and the colder parts of the room. Large inlet 
 registers should be placed in the floor near the entrance doors, 
 to stop cold draughts from blowing up the aisles when the doors 
 are opened, and also to be used as foot warmers. 
 
 Ventilators. — The main part of the exhaust ventilation should 
 be through registers or grilles located near the floor and connect- 
 ing with one or more outboard flues, depending upon the size 
 of the building. Here, as in the case of school buildings, the 
 flues should be heated and the air brought in below the stoves 
 or heaters. In addition to these, ceiling vents of'fgood size 
 should be provided for use in warm weather or for cBoling the 
 room quickly when crowded or over heated. 
 
 Indirect Steam. — The same general rules follow in the case of 
 indirect steam as have been described for furnace heating. The 
 stacks are placed beneath the registers or flues and mixing 
 dampers provided for regulating the temperature. If there are 
 large windows, flues should be arranged to open in the window 
 sills, so that a sheet of warm air may be delivered in front of the 
 windows to counteract the efifects of cold down draughts from 
 
286 
 
 HEATING AND VENTILATING PLANTS 
 
 the exposed glass surface above. These flues may usually be 
 made 3 or 4 inches in depth and should extend the full width of 
 the window. Small rooms, such as vestibules, library, pastor's 
 room, etc., are generally heated with direct radiation. 
 
 Rooms which are used during the week are often connected 
 with an independent heater so that they may be warmed without 
 running the large boilers, as would otherwise be necessary. 
 
 Fan System. — The most eiificient method of warming and 
 ventilating churches of larger size is by means of a fan system. 
 The best results in this case are obtained by introducing the air 
 supply through a large number of small openings in or near the 
 
 AIR FROM 
 DUCT RELOW 
 
 Fig. 200. Fan System for Delivering Air Through Small Openings. 
 
 floor. One arrangement successfully employed is to provide a 
 shallow chamber under each seat and connect these with a plenum 
 space beneath the floor. These connections may be either at the 
 center or ends of the pew as most convenient, and should be con- 
 cealed in the woodwork by thickening the supports or legs. By 
 this method the air is delivered at a low velocity through a long 
 slot as shown in Fig. 300. 
 
 Plenum Space. — If the auditorium has a sloping floor, a 
 plenum space may be provided between the upper or raised por- 
 tion and the main floor. 
 
 Sometimes a shallow basement 3 or 4 feet in height, with a 
 cemented floor, and extending under the entire auditorium is 
 used as an air space. If the basement is of good height and 
 used for storage or other purposes, it is necessary to carry large 
 
DIFFERENT TYPES OF BUILDINGS 
 
 287 
 
 galvanized-iron ducts at the ceiling under ' the center of each 
 double row of pews, and connect with each pair by means of 
 branch uptakes. The size of these uptakes should allow for 
 3 or 4 square inches for each occupant. 
 
 When the lower part of the church is occupied by finished 
 rooms the problem of a sufficient plenum space beneath the audi- 
 torium floor becomes more difficult, but even then it can often be 
 provided for by placing a false ceiling 18 or 20 inches below the 
 main ceiling of the basement. Another method of supply is to 
 deliver the air through a small register in the end of each pew 
 
 /--' 
 y 
 
 Dudr FROM 
 BELOW 
 
 END VIEW 
 
 ""be 
 
 BACK VIEW 
 
 Fig. 201. Supplying Ail in Cliaicli Buildings. 
 
 near the floor as shown in Fig. 201. This simplifies the pew con- 
 struction somewhat, but otherwise is not as satisfactory as the 
 preceding arrangement. 
 
 Discharge Ventilation. — When the air supply is introduced 
 through the pews, discharge ventilation should be at the ceiling 
 instead of through vents near the floor as in furnace or indirect 
 gravity heating. 
 
 When the air enters through a comparatively small number of 
 registers of large size, the greater part rises to the ceiling and is 
 diffused through the upper part of the room. As it cools it falls 
 slowly toward the floor, and is fairly well distributed throughout 
 the church. 
 
288 HEATING AND VENTILATING PLANTS 
 
 In reality the supply to the central portion is by means of down- 
 ward currents. Under these conditions the exhausted air should 
 be discharged through vent registers at the floor. When a fan is 
 used, and the supply is through a large number of small openings 
 near the floor, the conditions are changed, for in this case there 
 is a slow upward movement of a practically solid volume of pure 
 air throughout the entire room, which, after passing the breathing 
 line of the audience, continues upward and is taken off at the 
 ceiling. 
 
 Air Supply. — If the special pew construction is too expensive, 
 or for any other reason cannot well be used, and the fan is to be 
 retained, the greater part of the air is best introduced through 
 wall registers placed about 8 feet above the floor, with exhaust 
 openings at or near the floor. By this arrangement the air is 
 thrown horizontally toward the center of the church, and much of 
 it falls to the breathing level without rising to the upper part of 
 the room. Diff users of some inconspicuous design should be 
 placed over the inlets to prevent uncomfortable draughts upon 
 the heads of the audience directly below. 
 
 Exhaust Fans are seldom employed in church work except in 
 special cases. With furnace and indirect-steam systems heated 
 flues are relied upon to produce the necessary draught. When 
 a supply fan is used the pressure caused within the auditorium 
 will force the air outboard, if the necessary outlets are provided. 
 Ceiling vents should be gathered by means of galvanized-iron 
 ducts into central chambers, which are connected with suitable 
 roof ventilators well protected against back draughts. 
 
 Dampers should always be placed back of the ceiling vents, 
 with means for operating them from the auditorium or gallery 
 floors. 
 
 Air Volume and Velocity. — Velocities of 400 to 500 feet per 
 minute may be counted upon for the passage of the full volume 
 of air through the ceiling vents. 
 
 As the church service is usually only an hour in length, and 
 the cubic contents of the room large in proportion to the number 
 of occupants, an air supply of from 1,000 to 1,300 cubic feet 
 per hour per occupant will generally be found sufficient. If 
 the church is warmed by air rotation to a temperature of 65° 
 
DIFFERENT TYPES OF BUILDINGS 2S9 
 
 before service, and then fresh air from out of doors be delivered 
 at the same temperature during the service, the heat generated 
 by the audience will usually be sufficient to keep the room warm 
 in all ordinary winter weather. This makes it possible to use a 
 smaller main heater than is required in other buildings where the 
 floor space is less closely packed. 
 
 A heater capable of. raising the full volume of air to 85° 
 or 90° in zero weather is usually sufficient. As it is often de- 
 sirable to keep the auditorium moderately warm during the week 
 without running the fan, it is well to provide a separate sys- 
 tem of indirect stacks placed beneath floor registers located 
 at inconspicuous places around the room. These heaters may 
 take their air directly from the basement, which in turn should 
 be connected with the room above either by special openings or 
 by the use of stairways and open doors. 
 
 When the fan is running these registers should be closed unless 
 it is desired to utilize the heaters in warming up the auditorium 
 before service. 
 
 A fan driven by a direct-connected motor at a comparatively low 
 speed is preferable for this class of work on account of its 
 quietness of action. The warm-air flues in ' the window sills 
 should be retained, if the windows are large, but may be made 
 narrower if a fan is used, owing to the higher velocity of the 
 air ; slots 1 inch in width are usually sufficient for this purpose. 
 Heaters should be placed at the bottom of the window flues to 
 raise the air to a temperature of 110° to 130°. 
 
 Halls. 
 
 The treatment of a large audience hair is similar to that of a 
 church, and such a room is usually warmed in one of the three 
 ways already described. When a fan is used, the air is com- 
 monly delivered partly through registers in or near the floor, and 
 partly through those placed in the wall about 8 feet above it, 
 depending upon the arrangement and general construction of the 
 building. They should be made of large size so that the velocity 
 of the entering air will not exceed 200 or, better, 150 feet per 
 minute over the whole area of the register face, in order to avoid 
 draughts. If dififusers are used over the wall registers, velocities 
 
290 HEATING AND VENTILATING PLANTS 
 
 twice the above may be allowed. Where there are raised floors, 
 as in a balcony, the air may be forced into the space beneath, 
 and then delivered through openings in the risers, as shown in 
 Fig. .30,3. A part of the vents should be placed in the ceiling and 
 the remainder near the floor ; the former being especially for sum- 
 mer use or in case the room becomes overheated. All ceiling 
 vents, both in halls and churches, should be provided with 
 dampers, having means for holding them in any desired position. 
 Gravity Heating. — If indirect gravity heating is used, it will 
 generally be necessary to place heating coils in the vent flues for 
 use in mild weather; but if fresh air is supplied by means of a 
 
 RAISED PLATFORM 
 
 Fig. 202. Delivery of Air in Large Halls. 
 
 fan there will usually be pressure .enough in the room to force the 
 air out without the aid of other means. When the vent airways 
 are restricted, or the air is impeded in any way^electric ventilat- 
 ing fans are often used. These give especially good results in 
 mild or heavy weather when natural ventilation is sluggish. The 
 temperature of the room may be regulated by varying the num- 
 ber of sections in use in the main heater, or by the use of a by-pass 
 damper which allows part of the air to pass around the heater 
 instead of through it. 
 
 Combination Methods.— ^One of the best arrangements is a 
 combination of these two methods. A rough or partial regulation 
 may be obtained by manipulating the steam valves and a finer 
 adjustment by the use of the by-pass damper. For the best re- 
 sults the latter should be operated automatically by a graduated 
 thermostat placed in the hall. After an audience hall is once 
 warmed and filled with people, very little heat is required to keep 
 
DIFFERENT TYPES OF BUILDINGS 
 
 291 
 
 it comfortable even in the coldest weather. The air supply per 
 occupant may be taken about the same as for a church. 
 
 Theaters. 
 
 In designing a heating and ventilating system for a theater a 
 wide experience is necessary in order to secure the best results. 
 
 Heating Auditoriums.- — A theater consists of three parts : the 
 body of the house or auditorium ; the stage and dressing rooms ; 
 and foyer, lobbies, corridors, stairways and offices. The only 
 satisfactory way of warming and ventilating the auditorium is 
 
 Fig. 203. Heating System for Theaters. 
 
 by the use of a fan, and the most approved method of air dis- 
 tribution is to force it into closed spaces beneath the floors, and 
 allow it to discharge upward among the seats in a large number 
 of finely divided streams. One of the best arrangements is 
 through chair legs of special latticed design, which are placed 
 over floor openings of about 4 square inches for each leg. In this 
 way the air is delivered to the room at a low Velocity without 
 draughts or currents and is thoroughly diffused among the audi- 
 ence. A chair of the form mentioned above is shown in Fig. 20:5. 
 Another method, widely used at the present time, is the placing 
 of a "mushroom" inlet, so called, beneath each chair and con- 
 
292 
 
 HEATING AND VENTILATING PLANTS 
 
 necting it with a plenum space below the floor as already 
 described. 
 
 Sections through an inlet of this type are shown in Fig. 204. 
 The form is such as to deflect the entering air downward and 
 so diffuse it without sensible drafts. A regulating damper, 
 operated by a thumb-screw or similar device, is provided in each 
 inlet for adjusting the air flow to the amount desired. 
 
 In small theaters where the expense must be kept as low as 
 possible the arrangement already illustrated in Fig. .303 may be 
 used to good advantage wherever raised floors or risers occur. 
 
 /Dn(\\\\\ 
 
 Fig. 204. Longitudinal and Cross-Sections through Mushroom Air Inlet. 
 
 Discharge Ventilation. — The discharge ventilation should be 
 largely through ceiling vents, assisted by the use of exhaust 
 fans. Vent openings should also be provided at the rear of the 
 balconies, either in the wall or ceiling. The exhaust fans may be 
 placed either in the attic or basement as is most convenient. 
 The close seating of the audience produces a large amount of 
 animal heat, which is usually sufficient to increase the tempera- 
 ture of the room from 8° to 10° or even more; so that in 
 considering a theater once filled, and thoroughly warmed, it be- 
 comes more a question of cooling than of warming. 
 
 The temperature of the air supply to the auditorium is regulated 
 at the fan, the same as in the case of churches and halls. 
 
 Ventilating Dressing Rooms and Foyer. — The dressing rooms 
 should be provided with a generous supply of fresh air, sufficient 
 to change the entire contents once in 10 minutes at least, and 
 should have discharge flues of sufficient size to carry away this 
 amount of air at a velocity not exceeding 300 feet per minute, 
 unless connected with an exhaust fan, in which case the velocity 
 may be doubled. 
 
DIFFERENT TYPES OF BUILDINGS 293 
 
 In order to maintain a constant air supply the temperature of 
 the room is usually regulated in some independent way. This 
 is best done by means of direct radiation. 
 
 The foyer, corridors, etc., are generally heated by direct radi- 
 ators which may be concealed by ornamental screens if desired. 
 
 When there are offices connected, they may be treated in a 
 similar manner to rooms of like kind in other buildings. 
 
 The air supply for theaters may be taken at 1,200 to 1,500 
 cubic feet per hour per occupant. 
 
 Office Buildings. 
 
 Office buildings are satisfactorily warmed by direct steam, hot- 
 water, and in some cases by the fan system. Probably direct 
 steam is used for this purpose more frequently than any other, 
 although forced hot-water circulation is well adapted to this type 
 of building. 
 
 Exhaust Steam Heating. — As most modern office buildings 
 have their own power plant, provision should be made for utiliz- 
 ing the exhaust steam in the heating system. This can be done 
 by passing it through an oil separator and condensing it in the 
 radiators, either with or without the use of a vacuum system, 
 or by utilizing it for heating the water in a forced hot-water 
 system. 
 
 The methods already described under exhaust-steam heating 
 and forced hot-water circulation cover the ground quite thor- 
 oughly, and the problem becomes one of applying these methods 
 to the conditions as found in any particular case. 
 
 The overhead distribution of steam or water is to be preferred 
 for reasons previously given, and special care must be taken to 
 provide sufficient flexibility in the radiator connections, owing to 
 the great length of the drops or risers and consequent expansion. 
 
 Fan System. — When a fan system is used the arrangement of 
 the airways is usually somewhat different from any of those 
 yet described. Owing to the great height of these buildings and 
 the large number of small rooms which they contain, it is im- 
 possible to carry up separate flues from the basement. 
 
 One of the best arrangements is to construct false ceilings in 
 the corridors on each floor, thus forming air ducts which 
 
294 
 
 HEATING AND VENTILATING PLANTS 
 
 may receive their supply through one or more large uptakes ex- 
 tending from the basement to the top of the building. 
 
 Corridor Airways may be tapped over the door of each room, 
 the openings being provided with suitable regulating dampers for 
 gauging the air supply to each. 
 
 Adjustable deflectors should be placed in the main air shafts 
 for proportioning the quantity of air to be delivered to each 
 floor. 
 
 1 
 
 FALSE CEILING 
 
 Fig. 205. Sectional View of Corridor with Airways. 
 
 Fig. 305 shows a section through a corridor where this method 
 is employed. 
 
 Shops and Factories. 
 
 Shops and factories are warmed both by direct radiation and 
 by hot-blast systems. 
 
 Direct Radiation. — For heating by direct radiation either steam 
 or hot water under forced circulation may be used. The radiating 
 surface is usually in the form of pipe coils placed under the 
 windows or overhead, depending upon the character and use of 
 the rooms. The amount of radiation required will depend upon 
 the temperature it is desired to maintain, and also upon whether 
 heat is generated by the machinery or mechanical processes car- 
 ried on within the building. 
 
 The latter vary so widely in different cases that no definite rules 
 can be given. The conditions and requirements of each particular 
 case must be carefully studied, and the regular methods applied 
 with such modifications as the judgment and experience of the 
 engineer may direct. There are two general methods employed in 
 
DIFFERENT TYPES OF BUILDINGS 
 
 295 
 
 the use of a fan for factory heating, as illustrated in Figs. 206 
 and .207. 
 
 Fan Systems. — In the former, a large supply flue is carried up 
 through the building at a central point, from which galvanized- 
 iron distributing ducts are taken off near the ceiling of each story. 
 The air is discharged at a high velocity through numerous open- 
 ings toward the outer walls of the building, as indicated by the 
 arrows. 
 
 This arrangement is adapted to conditions where the ceilings 
 are comparatively free from projecting girders, etc., which would 
 break up the currents and prevent a good distribution of air. 
 
 
 MOISTENING CHAM BER- 
 
 r==^^=T 
 
 
 1 
 
 
 
 1 r 1 
 
 
 
 
 
 
 
 ^^ 
 
 
 
 
 ' 
 
 V 
 
 T t 
 
 
 t 
 
 T / 
 
 
 
 
 ) 
 
 =3 =^ % 
 
 i \ 
 
 / 
 
 ; ! 
 
 
 Fig. 206. Distribution of Air in Factory. 
 
 Duct in Basement. — The second ' arrangement consists of a 
 distributing duct in the basement, either of galvanized iron or 
 brick, running along one side of the building. From this, uptake 
 flues are carried in the outer wall to the different floors and the 
 air discharged horizontally near the ceiling. This method is 
 largely employed in textile mills, the movement of the belts and 
 pulleys being depended upon in part to distribute the air evenly 
 throughout the building. Adjustable dampers should be provided 
 at all outlets to properly regulate the supply to each floor. 
 
 In addition to these methods are various modifications designed 
 to meet different forms of building construction one of the most 
 important of which is the steel and concrete shop building with 
 
296 
 
 HEATING AND VENTILATING PLANTS 
 
 monitor roof. In buildings of this type the distributing ducts are 
 carried through the roof trusses and the air discharged down- 
 ward at an angle toward the outer walls. 
 
 Heating Surface.— In determining the size of heater, the first 
 step is to compute the heat loss by the methods given in 
 Chapter II. 
 
 "^*^^^^^*^f^pn'fVT^fet^ 
 
 Xfis;.xutti.lt'^-ii:j^Jiii!=iiliSi^ S& 
 
 Fig. 207. Heating Ducts in Factory. 
 
 In case all of the air is taken from out of doors, the problem 
 is of the same general nature as for any large room or building 
 heated by a hot-blast system and should be treated accordingly. 
 
 When rotation is employed the air simply becomes a medium 
 for transferring the heat to the different parts of the building and 
 the volume required to be moved will depend upon the quantity 
 of heat to be transferred and the temperature range through 
 which it is to be warmed. 
 
 Assuming the air to be returned to the heater at 60° and de- 
 livered by the fan at 140°, which may be taken as an average 
 working range, the rise in temperature will be 140 — 60 = 80°. 
 
DIFFERENT TYPES OF BUILDINGS 297 
 
 In cooling 1°, 1 cubic foot of air gives off ^/gj of a B. T. U., and in 
 cooling 80° it gives off 80 X Vbs = 1-4 B. T. U. Therefore the 
 total heat required per hour for warming, divided by 1.4, will 
 give the cubic feet of air to be passed through the heater in the 
 same tength of time. 
 
 With this data at hand it is a simple matter to proportion the 
 fan and heater by the methods already given. • 
 
 The amount of ventilation to be provided will depend some- 
 what upon the character of the work carried on in the building 
 and the cubic space per occupant. 
 
 A common method in the case of machine shops and buildings 
 of similiar construction and use, is to employ air rotation in zero 
 weather and take in outside air in increasing proportions as the 
 outside temperature rises. 
 
CHAPTER XVII. 
 
 CARE AND MANAGEMENT OF HEATING AND VEN- 
 TILATING PLANTS. 
 
 « 
 
 The proper care of a heating system is as important to its 
 successful operation as the first design, and it therefore becomes 
 necessary for the architect or designing engineer to understand 
 the principle points of its management, so that he may be able 
 to give suitable instructions to the operating engineer or janitor 
 who is to take charge of the plant. 
 
 Such information is also necessary to determine the cause of 
 difficulties which may come up later, should they be due to faulty 
 management. 
 
 Furnaces. 
 
 Although different makes of furnaces vary somewhat in con- 
 struction, the following general rules will apply equally well to 
 nearly all cases. 
 
 The fire should be thoroughly shaken once or twice daily in 
 cold weather, and the firepot kept even full at all tirnes, as in 
 this way a more even temperature may be maintained, less atten- 
 tion is required, and no more coal burned than when the pot, is 
 only partially filled. 
 
 In mild weather, when it is desired to reduce the temperature 
 in the house, ashes may be allowed to accumulate on the grate by 
 shaking less frequently ; these will hold the heat and render it an 
 easy matter to maintain and control the fire. 
 
 When feeding coal on a low fire, open the drafts and neither 
 rake nor shake the fire until the fresh coal has become ignited. 
 The air supply to the fire is of the greatest importance. An insuffi- 
 cient amount results in incomplete combustion and loss of heat. 
 To secure proper combustion the fire should be controlled princi- 
 pally by means of the ash pit, through the ash-pit door or slide. 
 
 The smoke-pipe damper should be opened only enough to 
 carry off the gas or smoke and to give the necessary draught. 
 The openings in the feed door act as a check to the fire and 
 
 298 
 
CARE AND MANAGEMENT 299 
 
 should be kept closed during cold weather, except just after fifing, 
 when with a good draught they may be partly opened to increase 
 the air supply and promote the proper combustion of the gases. 
 
 Keep the ash pit clear to avoid warping or melting the grate. 
 The cold-air box should be kept wide open except during high 
 winds or when the fire is low. At such times it may be partly, 
 but never completely, closed. ' Too much stress cannot be laid on 
 the importance of a sufficient air supply to the furnace. 
 
 If the building does not heat evenly, the registers in the warmer 
 rooms may be closed temporarily until a circulation is established 
 in the flues leading to the colder rooms. This result being secured, 
 the closed registers may again be opened, after which, in most 
 cases, all parts of the building will be found to receive their 
 proportion of warm air. 
 
 The best size and quality of coal will depend gomewhat upon 
 the grate area and strength of chimney draft. In general, the 
 best results will be obtained with egg size or smaller, and with 
 as hard a quality as the availaljle draft will readily burn. 
 
 After shutting down the furnace in the spring all parts should 
 be thoroughly cleaned and put in repair for the coming season. 
 The custom of delaying this until fall often increases the amount 
 of corrosion and may result in great inconvenience. 
 
 Low-Pressure Steam Heating. 
 
 Before starting the fire see that the boiler contains sufficient 
 water. The water-line should be at about the center of the 
 gauge glass. The smoke pipe and chimney flue should be clean 
 and the draught good to obtain the best results. Build the fire in 
 the usual way, using a quality and size of coal best adapted to the 
 heater. The general rules given for furnaces apply equally well 
 to the management of cast-iron house heating boilers. To con- 
 trol the fire see that the damper regulator is properly attached to 
 the draught doors and damper; then regulate the draught by 
 weighting the automatic lever as may be required to obtain the 
 necessary steam pressure for warming. 
 
 Never fill an empty boiler when hot. Should the water leave 
 the boiler from any cause, such as a broken gauge glass, priming, 
 etc., the fire should be checked by covering with wet ashes or 
 
300 HEATING AND VENTILATING PLANTS 
 
 fresh coal and the boiler be allowed to cool before admitting 
 cold water. 
 
 As long as the water level shows in the gauge glass the boiler 
 may be fed at any time with safety, but never when it has dis- 
 appeared, except after cooling down, as stated above. 
 
 The safety valve should be kept in working order and tested 
 frequently to prevent sticking. 
 
 Heating boilers should be cleaned at least once a year by empty- 
 ing and washing out with fresh water. 
 
 New boilers often contain oil, which works in from the joints 
 in the piping, these being usually made up with an oil and lead 
 filling. In cases of this kind a few pounds of caustic soda should 
 be put into the boiler and allowed to stand for a day or so, after 
 which, the boiler should be emptied and thoroughly rinsed. 
 
 During the summer months it is recommended that the water 
 be drawn off from the system, and that air valves and safety 
 valve be opened to permit the boiler to dry out and to remain so. 
 
 Good results are, however, obtained by filling the boiler full of 
 water, driving off the air by boiling slowly, and allowing it to re- 
 main in this condition until needed in the fall. The water should 
 then be drawn off and a fresh supply added. 
 
 The heating surfaces of the boiler should be kept clean and 
 free from ashes and soot by means of a brush made especially for 
 this purpose. 
 
 Should any of the rooms fail to heat, examine the steam valves 
 at the radiators and also see that the air valves are properly ad- 
 justed and in working order. 
 
 If the building is to be unoccupied in cold weather draw all 
 the water out of the system by opening the blow-oif pipe at the 
 boiler and all steam and air valves at the radiators. 
 
 Hot-Water Heating. 
 
 The general methods of firing and cleaning a hot-water heater 
 are practically the same as for a steam boiler, therefore, only 
 special points of difference need be considered. Before starting 
 up a hot-water system care should be taken to see that it is com- 
 pletely filled, as indicated by the water level in the expansion 
 tank or by the altitude gauge in the basement. 
 
CARE AND MANAGEMENT 301 
 
 Should the water in any of the radiators fail to circulate, 
 see that the valves are wide open and that the radiator is free 
 from air. Water must always be added at the expansion tank 
 or. boiler when for any reason it is drawn from the system. 
 
 The required temperature of the water will depend upon the 
 outside conditions and only enough fire should be carried to keep 
 the rooms comfortably warm. Thermometers should be placed in 
 the flow and return pipes near the heater as a guide. Special 
 forms are made for this purpose in which the bulb is immersed in 
 loil or mercury. 
 
 School Buildings. 
 
 Starting in the boiler room, special care should be given tb 
 •the quality of the fuel and the methods of firing. All flues and 
 :smoke passages should be kept free and clear from accumula- 
 tions of soot and ashes by means of a brush or steam jet. 
 Pumps and engine should be kept clean and in perfect adjust- 
 :ment, and extra care should be taken when they are in rooms 
 '.through which the air supply is drawn, or the odor of oil will be 
 •carried to the rooms. All steam traps should be examined at 
 regular intervals to see that they are in working order, and upon 
 .any sign of trouble they should be -taken apart and carefully 
 •cleaned. 
 
 The air valves on all direct and indirect radiators should be 
 inspected often, and upon the failure of any room to heat properly 
 the air valve should first be looked at as a probable cause of the 
 difficulty. 
 
 Adjusting dampers should be placed at the base of each 
 supply flue, so that the flow of air to each room may be regu- 
 lated independently. In starting up a new plant the system should 
 be put in proper balance by a suitable adjustment of these 
 dampers, and when once adjusted they should be marked and 
 left in these positions. The temperature of the rooms should 
 never be regulated by closing the inlet registers. These should 
 always remain open unless the room is to be unused for a day or 
 more. 
 
 In designing a fan system provision should be made for air 
 [rotation ; that is, the arrangement should be such that the same 
 
302 HEATING AND VENTILATING PLANTS 
 
 air may be taken from the building and passed through the fan 
 and heater continuously. This is usually accomplished by clos- 
 ing the main vent flues and the cold-air inlet to the building, 
 then opening the classroom doors into the corridor ways and 
 drawing the air down the stair wells to the basement and into 
 the space back of the main heater through doors provided for 
 this purpose. In warming up a building in the morning this 
 should always be practiced until about fifteen minutes before 
 school opens. The vent flues should then be opened, doors into 
 corridors closed, cold-air inlets opened wide, and the full volume 
 of fresh air taken from out of doors. At night the dampers in 
 the main vents should be closed, to prevent the warm air contained 
 in the building from escaping. 
 
 The fresh air should be delivered to the rooms at a tempera- 
 ture of 70° to 75°, and this temperature must be maintained, 
 by a proper use of the shut-off valves, thus running a greater 
 or lesser number of sections on the main heater. A little ex- 
 perience will show the engineer how many sections to carry for 
 different outside temperatures. A dial thermometer placed in the 
 main warm-air duct near the fan, will indicate the temperature of 
 the air delivered to the rooms, thus placing the apparatus under 
 his immediate control. 
 
INDEX 
 
 AlH PAGE 
 
 Velocity of flow 7 
 
 Composition 20 
 
 Analysis 21 
 
 Supply to different buildings 23 
 
 Quality 24 
 
 Filtering 25 
 
 Filtering 250 
 
 Cooling 25 
 
 Cooling 253 
 
 Distribution 27 
 
 Measurement 29 
 
 Air Washebs 
 
 General data 251 
 
 BOILEBB 
 
 Types of Heating Boilers 
 
 General data 49 
 
 Sectional boilers 50 
 
 Tybular boilers 53 
 
 Rating of Cast-iron Boilers 
 
 Computing size 54 
 
 Efficiency 55 
 
 Rate of combustion 55 
 
 Ratio of heating to grate surface .... 56 
 Rating of Tubular Boilers 
 
 Computing size 57 
 
 Rate of combustion 58 
 
 Rate of evaporation 58 
 
 Ratio of heating to grate surface 58 
 
 Cake and Management of H. and V, 
 Plants 
 
 Fiurnaces 298 
 
 Low-pressure steam heating 299 
 
 Hot-water heating 300 
 
 School buildings 301 
 
 Chimneys 
 
 Chimneys for heating boilers 59 
 
 ' Chimneys for power boilers 60 
 
 Circulation Coils 
 
 Coils for steam 82 
 
 Coils for hot water 131 
 
 Cost 
 
 Cost of heating 18 
 
 Cost of ventilation 31 
 
 Comparative cost of furnace, steam 
 
 and hot^water heating 48 
 
 Cost of electric heating 187 
 
 Ducts 
 
 Air ducts for fan systems 223 
 
 Air velocities in ducts 234 
 
 Electric Heating page 
 
 Application 184 
 
 Types of heaters 184 
 
 Calculation of electric heaters 184 
 
 Material for heaters 185 
 
 Connections for heaters 186 
 
 Cost of electric heating 187 
 
 Cost compared with steam 187 
 
 Expansion 
 
 Expansion of pipes 64 
 
 Expansion tanks 138 
 
 Fans 
 
 Centrifugal 189 
 
 Cone 191 
 
 Multivane 191 
 
 Disk or propeller 191 
 
 Proportions of Centrifugal Fans 
 
 Average dimensions 194 
 
 Form of scroll 195 
 
 Fan Calculations 
 
 General assumptions 196 
 
 Dynamic pressure 198 
 
 Static pressure 198 
 
 Velocity pressure . . . . j^. 199 
 
 Pressure and velocity 199 
 
 Results of tests 200 
 
 Size of outlet 201 
 
 Limit of speed 202 
 
 Relation of volume to speed 202 
 
 Horse power required 203 
 
 Efficiency 205 
 
 Effect of resistance upon capacity. . . . 206 
 
 Factors of resistance 206 
 
 Regulating air volume 207 
 
 Effect of resistance upon horse power . 208 
 Mechanical Draft 
 
 Fan proportions and speed 209 
 
 Horse power required 210 
 
 Effect of temperature 210 
 
 Multivane Fans 
 
 General data , 212 
 
 Disk or Propeller Fans 
 
 Capacity 212 
 
 ' Power required 213 
 
 Fan Drives 
 
 Different methods 230 
 
 Flues 
 
 Warm-air flues for furnaces 44 
 
 Warm-air flues for indirect steam. ... 118 
 
 Cold-air flues for indirect steam 119 
 
 Vent flues for indirect steam 120 
 
 303 
 
304 
 
 INDEX 
 
 Fltje^ page 
 
 Flues for fan systems 233 
 
 Flue velocities for fan systems 234 
 
 Forced Blast Heating 
 
 Advantages 215 
 
 Exhaust ventilation 215 
 
 Plenum system 215 
 
 Combined heating and ventilation. , . . 216 
 Main Heaters 
 
 General types 216 
 
 Pipe heaters 217 
 
 Heating surface of pipe heaters 218 
 
 Cast-iron heaters 219 
 
 Vento heaters 220 
 
 Efficiency of pipe heaters 221 
 
 Efficiency of cast-iron heaters 223 
 
 Hot-Water Headers 
 
 General form 226 
 
 Efficiency of hot-water heaters 227 
 
 Pipe Connections for Heaters 
 
 General arrangement 227 
 
 Returns ' 228 
 
 Exhaust sections 229 
 
 Pipe sizes 230 
 
 Fan Drives 
 
 Engines 230 
 
 Motors 231 
 
 Belts 232 
 
 Ducts and Flues 
 
 Distributing ducts 233 
 
 Underground ducts 233 
 
 Flues 233 
 
 Air velocity in ducts and flues 234 
 
 Furnace Heating 
 
 Advantages and disadvantages 32 
 
 Types of furnaces 33 
 
 Materials of construction 34 
 
 Parts of Furnace 
 
 Fire pot 35 
 
 Dome 36 
 
 Radiator 36 
 
 Heating surface 37 
 
 Casing 37 
 
 Air passages 37 
 
 Grate , 37 
 
 Evaporating pan 37 
 
 Determining Size of Furnace 
 
 Methods employed 38 
 
 Efficiency 38 
 
 Rate of combustion 38 
 
 Thermal unit method 39 
 
 Cubic space method 40 
 
 Auxiliary Equipment 
 
 Smoke pipe 41 
 
 Chimney 41 
 
 Cold-air box 42 
 
 Cold-air room 43 
 
 Return flues 43 
 
 Furnace Heating page 
 
 Hot-air pipes 44 
 
 Registers 46 
 
 Combination Systems 
 
 Proportions 47 
 
 Heat 
 
 Theory of heat 1 
 
 Unit of heat 3 
 
 Speeffic heat 3 
 
 Latent heat 3 
 
 Conduction 3 
 
 Convection 4 
 
 Radiation 4 
 
 Methods of Transmission 
 
 By air 5 
 
 By water 5 
 
 By steam 6 
 
 Hea;t for Ventilation 
 
 Methods of computation 26 
 
 Heating 
 
 Computations and design 18 
 
 Cost of heating 18 
 
 Furnace heating 32 
 
 Comparative cost of different systems . 48 
 
 Steam heating (direct) 74 
 
 Steam heating (indirect) *106 
 
 Steam heating (exhaust) 169 
 
 Steam heating (vacuum) 179 
 
 Hot^water heating (direct) 128 
 
 Hot-water heating (indirect) 142 
 
 Hot-water heating (forced circulation) . 154 
 
 Vacuum heating 179 
 
 Electric heating 184 
 
 Forced-blast heating 215 
 
 Combined heating and ventilation. . . . 216 
 
 Heat Loss from Buildings 
 
 Causes of heat loss 12 
 
 Loss by transmission 12 
 
 Loss by leakage 13 
 
 Correction for leakage 13 
 
 Correction for exposure 14 
 
 Approximate method for heat loss: . . 17 
 
 Heating and Ventilating Different 
 Types op Buildings 
 Dwelling Houses 
 
 General considerations 255 
 
 Schoolhotises 
 
 Furnace heating 255 
 
 Size of furnace 256 
 
 Uptake flues 256 
 
 Cold-air duet 257 
 
 Vent flues 257 
 
 Dampers 259 
 
 Indirect gravity system 259 
 
 Uniform air supply 259 
 
 Heating stacks 259 
 
 Cold-air chamber 260 
 
 Supply and vent flues 260 
 
INDEX 
 
 Heating and Ventilating Dipfbrent 
 
 Types of Buildings page 
 
 SehooUimLaes 
 
 Dampers 261 
 
 Temperature regulation 261 
 
 Pin radiators 262 
 
 Aspirating coila 262 
 
 Air rotation 263 
 
 Foot warmers 263 
 
 Small roon^ and basement 263 
 
 Combined direct and indirect heating. 263 
 
 Area of stack surface 264 
 
 Area of direct surface 264 
 
 Location of direct radiators 265 
 
 Pipe connections 265 
 
 Special conditions 265 
 
 Fan systems 266 
 
 Plenum method 266 
 
 Size of ducts 267 
 
 Diffusers 267 
 
 Tent flues 267 
 
 Main heater 268 
 
 Arrangement with cast-iron heater. . . 269 
 
 Arrangement with pipe heater 270 
 
 Keturn of condensation 270 
 
 Valve connections 271 
 
 Temperature regulation 272 
 
 Toil^s and Chemical Hoods 
 
 Exhaust ventilation 273 
 
 Ventilation by fans 273 
 
 Small toilet rooms 273 
 
 Chemical hoods 274 
 
 Hospitals and Asylums 
 
 Cottage hospitals 274 
 
 Radiating surface 275 
 
 Air supply 276 
 
 Air ducts 277 
 
 Miscellaneous heating 278 
 
 Boiler arrangement 279 
 
 Return connections. 279 
 
 Temperature of air 280 
 
 Arrangement of apparatus 282 
 
 Exhaust fans 283 
 
 Insane asylums 284 
 
 Churches 
 
 Furnace heating 285 
 
 Ventilators 285 
 
 Indirect steam 285 
 
 Fan system 286 
 
 Plenum space 286 
 
 Discharge ventilation 287 
 
 Air supply 288 
 
 Exhaust fans 288 
 
 Air volume and velocity 288 
 
 Halls 
 
 General treatment 289 
 
 Gravity heating 290 
 
 Combination methods 290 
 
 Heating and Ventilating Difebrent 
 
 Types of Buildings page 
 
 Theatres 
 
 Heating auditoriums 291 
 
 Discharge ventilation 292 
 
 Dressing rooms and foyer 292 
 
 Office Buildings 
 
 Exhaust steam heating 293 
 
 Fan system 293 
 
 Corridor air ways 294 
 
 Shops and Factories 
 
 Direct radiation . . , 294 
 
 Fan system 295 
 
 Duct in basement 295 
 
 Heating surface 296 
 
 Hot-Watbe Heating (Gravitt) 
 
 Principles involved 8 
 
 Pressure head . .^ 8 
 
 Advantages and disadvantages 128 
 
 Types of radiating surface 130 
 
 Efficiency of direct radiators 132 
 
 Systems of Piping 
 
 Two-pipe system . l33 
 
 Circuit system l34 
 
 Overhead system l35 
 
 Pressure Systems of Heating 
 
 Generators with mercury seal 136 
 
 Generators with spring valves l38 
 
 Details of Construction 
 
 Expansion tank 13S 
 
 Air venting 139 
 
 Ra(Hator connections 141 
 
 Valves 141 
 
 Pipe fittings 142 
 
 Indirect Heating 
 
 Size of stacks 143 
 
 Flues and casings 143 
 
 Pipe connections 144 
 
 Combination Systems 
 
 Data for design 146 
 
 Pipe Sizes 
 
 General data 147 
 
 Average elevation of system 149 
 
 Pipe sizes for direct heating 150 
 
 Pipe sizes for indirect heating 151 
 
 Boilers 
 
 General data_ 152 
 
 Hot-Water Heating (Forced) 
 Piping 
 
 Systems of piping 154 
 
 Head necessary for circulation 155 
 
 Sizes of mains and branches 156 
 
 Velocity of flow. . 156 
 
 Loss through friction. . 157 
 
 Centrifugal Pumps 
 
 Principle of operation 159 
 
 Design and construction 160 
 
 Efiiciency and horse power 162 
 
INDEX 
 
 Hot-Water Heating (Forced) page 
 
 Heaiers 
 
 General design 164 
 
 Heating surface and efficiency 165 
 
 Auxiliary heater 166 
 
 "Vacuo" heating 166 
 
 Pump and heater connections 166 
 
 Humidity 
 
 Definition 25 
 
 Humidistat 248 
 
 Humidity control 253 
 
 Pipe and Fittings 
 
 Wrought-iron pipe 61 
 
 Cast-iron fittings 62 
 
 Flanged joints and gaskets 64 
 
 Hangers 64 
 
 Pipe expansion 64 
 
 Piping Systems 
 
 Steam heating (direct) 87 
 
 Steam heating (indirect) 116 
 
 Steam heating (exhaust) 176 
 
 Steam heating (vacuum) 179 
 
 Hotr-water heating (gravity) 133 
 
 Hot-water heating (forced) 154 
 
 Pipe connections for main heaters. . . . 227 
 
 Pumps 
 
 Centrifugal 159 
 
 Return 174 
 
 Radiation 
 
 Computing direct steam radiation .... 86 
 Computing indirect steam radiation. . 109 
 Computing direct hot-water radiation . 132 
 Computing indirect hot-water radia- 
 tion 143 
 
 Computing pipe heaters for forced- 
 blast 221 
 
 Computing cast-iron heaters for forced- 
 blast..., 223 
 
 Computing hot-water heaters for 
 
 forced-blast 227 
 
 Radiators 
 
 Direct steam radiators 77 
 
 Indirect steam radiators 107 
 
 Direct hot-water radiators 130 
 
 Indirect hot-water radiators 143 
 
 Main heaters, for steam 216 
 
 Main heaters, for hot water 226 
 
 Rbgibtebs and Grilles 
 
 Location 125 
 
 Construction 126 
 
 Size for dwellings 127 
 
 Requlators 
 
 Hot-water regulators 245 
 
 Temperature regulators 236 
 
 Special Devices 
 
 Automatic Temperatute Regulation 
 
 General types 236 
 
 Air compressors -. . . 236 
 
 Thermostats 238 
 
 Special Devices page 
 
 Johnson thermostat 238 
 
 Powers thermostat 239 
 
 Hot-air thermostat 241 
 
 Valves 241 
 
 Diaphragm motors 242 
 
 Dampers 242 
 
 Methods of automatic control 243 
 
 Hot-Water Regulatora 
 
 Johnson hydraulic regulator 245 
 
 Powers hot-water regulator 245 
 
 Sylphon regulator 246 
 
 Telethermometer 
 
 General description 247 
 
 HuTnidostac 
 
 General description 248 
 
 Air Filters 
 
 Dry filters 250 
 
 General construction 250 
 
 Air Washers 
 
 Principle of operation 251 
 
 Form of spray 262 
 
 Air velocity through washer 252 
 
 Humidity control 253 
 
 Air cooling 253 
 
 Steam 
 
 Flow in pipes 10 
 
 Steam Heating (Direct) 
 
 Advantages and disadvantages 74 
 
 Features to be considered 76 
 
 Types of Radiating Surface 
 
 Cast-iron radiators 77 
 
 Wall radiators 77 
 
 Pipe radiators 81 
 
 WaU coils 82 
 
 Overhead coils 83 
 
 Efficiency of Radiators 
 
 Determining factors 84 
 
 Size and Location of Radiators 
 
 Computing size of radiators 86 
 
 Location of radiators 87 
 
 Systems of Piping 
 
 Two-pipe system 87 
 
 Advantage of wet return 88 
 
 Arrangement of drips 89 
 
 One-pipe rehef system 90 
 
 Arrangement of risers 91 
 
 Expansion of risers 91 
 
 One-pipe circuit system 92 
 
 Valves and piping 93 
 
 Radiator connections 96 
 
 Vapor Systems 
 
 Principal features 95 
 
 Webster modulation system . 96 
 
 Vacuum Syst&na < 
 
 Different kinds 97 
 
 Eddy vacuum system , 98 
 
 Construction of Pipe Lines 
 
 Pipe sizes 99 
 
INDEX 
 
 307 
 
 Steam Heating (Direct) page 
 
 Constmctifm of Pipe Lines 
 
 Returns 101 
 
 Floor and ceiling plates 101 
 
 Boiler Equipment 
 
 Types of boilers 103 
 
 Boiler connections 103 
 
 Blow-off tanks 105 
 
 Steam Heating (Indirect) 
 
 Advantages and disadvantages 106 
 
 Types of Radiating Surface 
 
 Cast-iron radiators 107 
 
 School-pin radiator 107 
 
 Cardinal radiator 108 
 
 Pipe radiator 108 
 
 Efficiency 108 
 
 Computing Indirect Radiation 
 
 Calculations for achoolhouees 109 
 
 Calculations for dwellings 110 
 
 Calculations for hospitals 110 
 
 Stack Casings and Supports 
 
 Construction Ill 
 
 Method of support Ill 
 
 Arrangement of heaters 112 
 
 Mixing dampers 113 
 
 Heating two or more rooms 115 
 
 Heating by air rotation 115 
 
 Steam Pipe Connections 
 
 Systems of piping 116 
 
 Pipe sizes 117 
 
 Warm-Air Fluea 
 
 Flues for dwellings 118 
 
 Flues for school houses 1 18 
 
 Cold-Air Supply Ducts 
 
 Area and construction 119 
 
 Vent Fluea 
 
 Material and construction 120 
 
 Dimensions of flues 120 
 
 Air velocity in flues 121 
 
 Aspirating coils 122 
 
 Vent hoods 125 
 
 Registers and Grilles 
 
 Location of registers 125 
 
 Construction 126 
 
 Computing size 127 
 
 Steam Heating (Exhaust) 
 
 Factors to be considered 169 
 
 Feed-water heating 169 
 
 Conditions for using live steam 170 
 
 Effect of back-pressure 171 
 
 Special Apparatus 
 
 Steam traps 172 
 
 Bucket traps 173 
 
 Expansion traps 173 
 
 Return traps 173 
 
 Return pumps 174 
 
 Oil separators 175 
 
 Piping and Valves 
 
 General data 175 
 
 Steam Heating (Exhatjbt) page 
 
 Supply and return piping 176 
 
 Exhaust pipe and heating main 176 
 
 Vacuum Systems 
 
 Types of vacuum systems 179 
 
 Webster system 180 
 
 Paul system 182 
 
 Telethebmometer 
 
 Description 247 
 
 Temperature 
 
 Definition 1 
 
 Thermometers 2 
 
 Fahrenheit scale 2 
 
 Centigrade scale 2 
 
 Method of conversion 2 
 
 Temperature Control 
 
 Systems of temperature regulation , , . 236 
 
 Testing 
 
 Testing steam and hot- water systems . 152 
 
 Traps 
 
 Steam 172 
 
 Return 173 
 
 Valves 
 
 General requirements . . 65 
 
 Gate valves ] 65 
 
 Globe valves 66 
 
 Angle valves 66 
 
 Radiator valves 66 
 
 Hot-water valves 67 
 
 Check valves 67 
 
 Air valves 69 
 
 Pressure reducing valves 72 
 
 Back pressure valves 72 
 
 Ventilation 
 
 , Importance of ventilation 20 
 
 Atmospheric Composition 
 
 Constituents 20 
 
 Oxygen 21 
 
 Nitrogen 21 
 
 Carbon dioxide 21 
 
 Analysis of air 21 
 
 Air Supply and Conditioning 
 
 Standard of purity 22 
 
 Air supply for different buildings.'. . . 23 
 
 Effect of gas jets 24 
 
 Air quality 24 
 
 Air filtering 26 
 
 Air cooling 26 
 
 Humidity 25 
 
 Heat for Ventilation 
 
 Method of computation 26 
 
 Air Distribution 
 
 Methods employed 27 
 
 Arrangements of inlets and outlets ... 28 
 Measurement of Velocity 
 
 Anemometers 29 
 
 Methods of measurement 30 
 
 Coat of Ventilation 
 
 Method of computation 31 
 
308 
 
 INDEX 
 
 VentiIuAtion page 
 
 Systems of Ventilation 
 
 Exhaust ventilation 215 
 
 Plenum system 215 
 
 Combined heating and ventilation 216 
 
 TABLES 
 
 I. Pressure temperature and latent 
 
 heat of steam 6 
 
 II. Constants and fifth powers for 
 formula for flow of steam 10 
 
 III. Flow of steam in pounds per 
 minute 11 
 
 IV. Heat transmission through various 
 building structures 14 
 
 V. Correction factors for exposure of 
 rooms 15 
 
 VI. Amount of air required for ventila- 
 tion 22 
 
 VII. Air supply for various buildings. . 23 
 
 VIII. Air supply for various rooms .... 24 
 
 IX. Cubic feet of space heated by fur- 
 naces of different size 41 
 
 X. Chimney sizes for furnace heating . . 42 
 
 XI. Areas of round hot-air pipes 45 
 
 XII. Areas of oval hot-air pipes 46 
 
 XIII. Standard sizes of registers for 
 various diameters of hot-air pipes. . 47 
 
 XIV. Heating surface in furnaces for 
 combination systems 47 
 
 XV. Rates of combustion for house- 
 heating boilers 56 
 
 XVI. Proportions of tubular boilers ... 57 
 
 XVII. Relation between boiler horse 
 power and radiation 58 
 
 XVIII. Chimney dimensions for heat- 
 ing 59 
 
 XIX. Chimneys for power boilers 60 
 
 XX. Dimensions of wrought-iron pipe . 62 
 
 XXI. Sizes of single-column radiators . 78 
 
 XXII. Sizes of double-column radiators 78 
 
 XXIII. Sizes of three-column radiators 79 
 
 XXIV. Sizes of four-column radiators . 79 
 
 XXV. Heating surface and linear di- 
 mensions of wall radiators 80 
 
 XXVI. Relative efl&ciencies of various 
 types 01 radiators 86 
 
 XXVII. Area of radiating surface for 
 different pipe sizes 99 
 
 XXVIII. Areas for different sizes of cir- 
 cuit mains 100 
 
 XXIX. Areas of radiator surface for 
 different risera 101 
 
 XXX. Sizes of connections between 
 risers and radiators 102 
 
 PAGE 
 
 XXXI. Sizes of returns 102 
 
 XXXII. Sizes of steam pipes for in- 
 direct radiator^ 118. 
 
 XXXIII. Velocities of air flow in feet 
 per minute 123 
 
 XXXIV. Pressure heads for flow 
 through hot-water pipes. . 148 
 
 XXXV. Sizes of direct hot-water heat- 
 ing mains 150 
 
 XXXVI. Sizes of direct hot-water 
 heating risers 150 
 
 XXXVII. Sizes of indirect hot-water 
 heating mains 151 
 
 XXXVIII. Comparative loss of bead in 
 fittings and straight pipe 157 
 
 XXXIX. Sizes of hot-water mains and 
 velocities of flow 158 
 
 XL. Capacities, speeds and horse 
 powers of centrifugal pumps for fric- 
 tion heads from 16 to 90 feet 160 
 
 XLI. Capacities, speeds and horse 
 powers of centrifugal pumps for 
 friction heads from 6 to 60 feet. . . . 161 
 
 XLII. Capacities, speeds and horse 
 powers of centrifugal p\imps for 
 friction heads from 4 to 40 feet. , . . 161 
 
 XLIII. Dimensions of fans with full 
 
 housing 196 
 
 XLIV. Dimensions of fans with three- 
 quarter housing 197 
 
 XLV. Proportions of centrifugal fans. . 202 
 
 XL VI. Volume of air delivered by 
 
 centrifugal fans 203 
 
 XL VII. Efficiencies of centrifugal fans . 204 
 
 XLVIII. Horse powers required by 
 
 fans at various speeds 205 
 
 XLIX. Temperature factors for fan 
 
 calculations 211 
 
 L. Volume of air delivered by disk fans . 212 
 
 LI. Speeds of disk fans for given ve- 
 locities of air-flow 213 
 
 LII. Horse powers for disk fans 214 
 
 LIII. Dimensions of forced-blast pipe 
 
 heaters 219 
 
 LIV. Dimensions of vento heaters. . . . 222, 
 
 LV. Final air temperatures for different 
 
 velocities through heater 223 
 
 LVI. Efficiencies for different velocities 
 
 through heater 224 
 
 LVII. Sizes of pipe for forced-blast 
 
 heaters 230 
 
 LVIII. Thickness of galvanized iron for 
 
 ducts 234