MC-NRLF 
 
 075 
 
UNIVERSITY OF CALIFORNIA 
 
 ANDREW 
 
 SMITH 
 
 HALLIDIC: 
 
 1868^^^, 19O1 
 
THE ENGINEERING RECORD SERIES 
 
 STEAM HEATING 
 
 AND 
 
 VENTILATION 
 
 BY 
 
 WILLIAM S. I^ONROE, M. E. 
 
 Member American Society of Mechanical Engineers. 
 Member American Society of Heating and Ventilating Engineers. 
 Member Western Society of Engineers. 
 
 NEW YORK 
 
 THE ENGINEERING RECORD 
 1902 
 
<A 
 
 HALLIDiE 
 
 COPYRIGHT, 1902, BY THE ENGINEERING RECORD. 
 
Preface. 
 
 The chapters comprising this book were originally written as a 
 series of articles for The Engineering Record and have been some- 
 what revised for their present form. 
 
 It has been the aim of the writer to present briefly the theoreti- 
 cal considerations involved in the design of heating and ventilating 
 plants, and to compile the best of the large array of empirical 
 formulas and data in a way that will be of value to those interested 
 in the current practice of the art. 
 
 The writer has taken the liberty to refer frequently to previous 
 works on the subject, and principally to those of Mills, Baldwin 
 and Carpenter. He wishes to acknowledge special indebtedness 
 to Mr. Alfred E. "Wolff for many valuable data. 
 
 WM. S. MONROE. 
 
 Chicago, August, 1901. 
 
Table of Contents* 
 
 Page 
 
 Chapter I. Introductory 7 
 
 Chapter II. Steam Heating; Systems of Piping and Steam Supply.. 13 
 
 Chapter III. Steam Heating Apparatus 31 
 
 Chapter IV. Indirect Radiators 48 
 
 Chapter V. Design of Radiation 60 
 
 Chapter VI. Piping and Construction Details 72 
 
 Chapter VII. Mechanical Ventilation General Principles 96 
 
 Chapter VIII. Systems of Mechanical Ventilation 103 
 
 Chapter IX. Ventilating Ducts 113 
 
 Chapter X. Ventilating Fans, Heaters and Other Apparatus 124 
 
 Index 147 
 
STEAM HEATING AND VENTILATION, 
 
 CHAPTEE L INTRODUCTORY. 
 
 The first really practical treatise on heating and ventilatioir 
 seems to have been published in 1824 by Thomas Tredgold, and in 
 that volume much space is given to the importance of securing 
 adequate ventilation, and also to the merits of heating by systems 
 of steam pipes. Mr. Tredgold gives accounts of several buildings 
 which were successfully heated in this way. It is cited that the 
 first factory in which steam was used for heating was a cotton mill 
 belonging to a Mr. Neil Snodgrass, in which a steam heating sys- 
 tem was installed in 1799. This was doubtless about the first in- 
 stance of the employment of steam primarily and systematically 
 for the purpose of heating. Mr. Tredgold describes a factory 
 which was equipped with a steam-heating system in 1817 as a sub- 
 stitute for stoves, which had been previously used. The building 
 was 90 feet by 30 feet, exposed on all sides, and four floors high. 
 Each floor was warmed by a single pipe running the length of the 
 building at the ceiling and midway between the sides. The sys- 
 tem carried 30 pounds steam pressure, but besides embodying the 
 most inefficient location for the radiating surface, the system, as 
 described, did not have over 450 square feet of heating surface for 
 a building containing 91,800 cubic feet of space. Mr. Tredgold 
 states that the system showed great improvement, both in economy 
 and results, over the previous method, adding that the employees 
 suffered much less from "chaps and chills," so that one can only 
 imagine the wretched condition of factory employees in cold 
 weather previous to that time, even in the comparatively mild cli- 
 mate of England. 
 
 The problem of artificial ventilation antedates that of steam 
 heating by more than half a century, though, of course, it does 
 not antedate the heating of buildings by various methods more 
 primitive. Mr. W. F. Butler, in a handbook on ventilation, pub- 
 
8 STEAM HEATING AND VENTILATION. 
 
 lished some years ago, states that the first scientific consideration 
 of the subject of artificial ventilation occurred in 1723, when a 
 certain Dr. Desaguliers was commissioned to institute some means 
 for making the atmosphere in the House of Commons more habit- 
 able ; and the doctor seems to have installed a system which proved 
 satisfactory, although it had been previously attempted by no less 
 a personage than the celebrated architect, Sir Christopher Wren. 
 Since that time the question of ventilation has occupied increasing 
 attention in the minds of physicians, architects and other scien- 
 tific men interested in the public welfare, but even to this day 
 what may be called "artificial" or forced ventilation remains to 
 a large extent a luxury. 
 
 From the earliest times in the latitudes of northern Europe and 
 North America, some form of heating in cold weather has been a 
 necessity for all buildings, whether caves or palaces, but even as 
 late as the latter part of the nineteenth century such a thing as 
 a uniform temperature in heated rooms in severe weather was 
 never expected, while ventilation was invariably secured only by 
 such means as would be accomplished by the circulation of air 
 through doors and other openings. In the days of our forefathers, 
 when houses were built with large rooms and great, high-ceiling 
 halls, and when people spent a large part of their time in the open, 
 air, there was in reality but little need of artificial ventilation ; and 
 in the rude homes of the poorer classes that which was secured 
 through poorly constructed walls and through loose windows of 
 oiled paper was generally much more than was desired. With the 
 improvement of transportation facilities, however, and the gath- 
 ering of large numbers of people into small areas, and compara- 
 tively large numbers in single buildings, the need of artificial ven- 
 tilation, in order to secure anything like a wholesome atmosphere, 
 gradually became apparent, and it is natural that the demand for 
 such ventilation should be recognized first in a building like the 
 House of Commons. 
 
 Out of the same economic conditions arose the necessity of heat- 
 ing buildings by steam. Buildings of all kinds had from the ear- 
 liest days been heated by open fireplaces, in which logs, and later 
 coal, were burned in considerable quantities, while the larger pro- 
 portion of the heat escaped up the flue. But forests were in time 
 reduced, cities grew, and buildings were made larger and with a 
 much larger number of rooms; and people were forced to find 
 
STEAM HEATING AND VENTILATION. 9 
 
 more economical ways of heating than by laboriously carrying ex- 
 pensive fuel to separate fires in each individual room. Stoves were 
 built to get more uniform combustion and save some of the heat 
 lost up the flue, and gradually various forms of distributing heat 
 through many rooms from one central fire were developed TO 
 economize labor. Heated air, heated water and steam were all in 
 turn experimented with as a means of distributing heat, anil sys- 
 tems employing them have been rapidly and scientifically evolved 
 to meet various requirements, and are to this day very widely 
 used. But since the time of Tredgold, heating by steam has in- 
 creased in extent and popularity year after year, especially since 
 the increase in size of buildings began to be very rapid, and its 
 economy of operation and incidental advantages of convenience 
 and simplicity have become more and more apparent, until at the 
 present day, in some form or another, it is used almost universally 
 in all installations requiring distribution of heat over any consid- 
 erable area. In this country it is well within the memory of most 
 men in active life when even our largest factories and office build- 
 ings were heated by means of open fires and stoves, but the de- 
 velopment from a primitive life to a congested and complex civili- 
 zation has been phenomenally rapid, especially in the last quarter 
 century, and the greatest advances in steam heating, as well as 
 in most practical sciences, have been made in that period. These 
 have chiefly been due to the almost universal application of steam 
 power and the tremendous economy effected by the use of exhaust 
 steam for heating. 
 
 The problem of mechanical ventilation, therefore, though grow- 
 ing out of much the same economic conditions, was solved, to a 
 large extent, independently of the question of heating; and with 
 the development of heat distribution by steam much was lost in 
 the way of ventilation. The old-time fireplace and stove insured 
 a certain amount of ventilation, to say nothing of the mental ex- 
 hilaration of the former, but heating by steam was accomplished 
 with no ventilation whatsoever. Hygienically, therefore, it was a 
 step in the wrong direction, but economically the lack of ventila- 
 tion made it more advantageous, as ventilation requires the heat- 
 ing of all incoming air. Heat in cold weather was the prime es- 
 sential, and it was always possible to obtain some amount of ven- 
 tilation by what might be called the "natural circulation" of air 
 through doors and windows. The fallacy of resorting to such 
 
10 STEAM HEATING AND VENTILATION. 
 
 methods exclusively has been pointed out in many tracts and 
 treatises published since the latter part of the eighteenth century, 
 but the fact remains that even to the present day a vast majority 
 of our buildings, a large proportion even of our factories, churches 
 and schoolhouses, and most of our fine office buildings, with their 
 boasted modern improvements, have no mechanical means for in- 
 suring an adequate ventilation. 
 
 At the present day we have arrived at a considerable degree of 
 advancement, however, and buildings might now be divided into 
 two quite distinct classes those which are "densely peopled" and 
 those which are "sparsely peopled" and our advancement is such 
 that mechanical ventilation is generally looked upon as a necessity 
 for all buildings of the former class, which may include school- 
 houses, churches, hospitals, theaters, and other audience halls. 
 In buildings of the second class, such as residences, office build- 
 ings and hotels, we have been, as a rule, satisfied with sufficient 
 heat, and have relied upon such ventilation as is secured by the 
 natural circulation methods. In such buildings, therefore, the 
 system of heating most used is that known as "direct radiation," 
 in which radiators, or some form of radiating surface, are located 
 in each room, and connected by an arrangement of piping to a cen- 
 tral source of steam or hot-water supply. The rooms are heated 
 by radiation from the hot surface and by contact of the air with 
 it, but no provision is made for the supply of fresh air. 
 
 Several adaptations of the ordinary direct-radiation system of 
 steam heating have been developed, however, with a view of ob- 
 taining the advantage of ventilation which was secured in the old- 
 time stoves and fireplaces. The principal one of these is what i* 
 known as the system of "indirect radiation," in which the radia- 
 tors, instead of being located in the rooms to be heated, are all 
 placed below them, generally in the basement of the building, and 
 are enclosed in boxes, which are provided with air inlets from the 
 outside of the building, and with flues running to the room to be 
 heated. Fresh air coming through the inlet in contact with the 
 radiator is heated and rises through the vertical flue by the natu- 
 ral upward tendency of hot air. Both heat and ventilation are in 
 this way provided to the rooms by the incoming hot air. This sys- 
 tem has been much used in residences, and also to a small extent 
 in some buildings of the "densely-peopled" class, such as hos- 
 pitals and hotels. But the system has a decided disadvantage, due 
 
STEAM HEATING AND VENTILATION. 11 
 
 to the fact that the amount of ventilation secured is practically 
 proportional to the amount of heat required, and in warm weather 
 but little, if any, ventilation is obtained. Furthermore, experience 
 shows that in order to ensure reliability it is necessary to have a 
 separate flue for almost every room and to locate the radiators, 
 directly beneath the vertical flue, so that in buildings of any size,, 
 especially those more than one or two stories in height, the ar- 
 rangement of radiators in the basement becomes difficult, and the 
 system of air flues, which are necessarily large, is complex and ex- 
 pensive in space and also in construction. 
 
 In order to avoid the difficulties of the system of "indirect radia- 
 tion" and yet secure some ventilation, a combination has been de- 
 veloped which goes under the significant title of "direct-indirect 
 radiation." In this the radiators are located in each separate room,, 
 but they are of special construction, and provided with air connec- 
 tions through the walls of the building so arranged that a certain 
 amount of air can be admitted through this connection so as to 
 pass around the radiator, becoming heated by contact with it. The 
 room is therefore heated both by direct radiation and by the in- 
 coming current of fresh hot air, and considerable ventilation is- 
 secured. 
 
 In this system, as in the "indirect," ventilation in warm weather 
 is dependent on open windows and doors, and it has been as yet 
 but little used. It has, however, in a few cases been adapted to 
 office buildings and hotels, and in the opinion of the writer we 
 may look for a very decided development of the "direct-indirect'* 
 during the immediate future in buildings of the more sparsely- 
 peopled character, where the amount of ventilation required per 
 square foot of floor area is comparatively small. But for such 
 buildings this system only achieves its best results when combined 
 with a mechanical system for exhausting the air. 
 
 As already mentioned, we have, perhaps, arrived to-day at a 
 point in the advancement of hygienic science where some system 
 of artificial or mechanical ventilation is looked upon as necessary 
 for all buildings of what the author has called the densely-peopled 
 class. It is difficult to define the limits of such buildings, as the 
 height and nature of the room and length of time occupied affect 
 the question, but in a general way any room or apartment in which 
 each individual occupies less than 40 square feet of floor area 
 should be included in such a classification, especially if occupied 
 
12 STEAM HEATING A\D VENTILATION. 
 
 more than two or three hours at a time. The systems which may 
 be employed for mechanical ventilation are numerous and varied, 
 "but they all embody the use of fans of one kind or another for 
 forcing.the air into the rooms, or exhausting it, or both, with prop- 
 er provision for heating the incoming air in cold weather, and some 
 one of the three heating systems is frequently, if not generally, 
 employed in connection with a system of mechanical ventilation. 
 
CHAPTER II. STEAM HEATING; SYSTEMS OF PIPING 
 AND STEAM SUPPLY. 
 
 Systems of piping. The three systems of steam heating as de- 
 scribed in Chapter I. the direct, indirect and direct-indirect 
 radiation are governed by much the same- rules- in the matter of 
 piping arrangement and steam supply, the two latter requiring 
 only special rules for proportioning the amount of heating sur- 
 face and for the arrangement of air supply-. As- regards piping, 
 there are the one-pipe and two-pipe systems, with several varieties 
 and combinations of each; and as regards the steam supply, there 
 are high and low-pressure systems, exhaust systems, gravity sys- 
 tems, vacuum systems terms more or less indefinite and somewhat 
 mixed in their application. 
 
 The essential requisites of a steam-heating system comprise: 
 First, a source of steam supply, which may be either an independ- 
 ent boiler or a heater or tank of some description supplied with 
 exhaust steam from an engine. Second, a system of piping to 
 conduct the steam from the .source of supply to the radiators. 
 Third, a series of radiators or radiating surfaces consisting of en- 
 closed spaces in which the steam is condensed by the cooler air 
 of the room on the outside of the surface. Fourth, a system of 
 return pipes through which the water condensed in the radiators 
 is removed; and fifth, a receptacle into which this water is drained. 
 
 The second and fourth of these requisites may be either wholly 
 or in part embodied in one, as may also the first and fifth. It might 
 be more briefly stated, therefore, that the prime requisites are 
 only the source of steam supply, the radiating surface and a sys-i 
 tern of piping connecting them. . But even though the supply and 
 the return pipes be embodied in the same system, it is just as 
 necessary that they be so arranged as to dispose of the water of 
 condensation as it is for them to supply steam to the radiator, 
 which fact should never be lost sight of. 
 
 One-pipe system. The simplest possible heating system, there^ 
 fore, is one which would be known as .a one-pipe gravity system, 
 
14 
 
 STEAM HEATING AND VENTILATION. 
 
 such as is indicated in Figure 1. The steam is generated in the 
 boiler, flows through the pipes to the radiators, the water condensa- 
 tion as it is formed in the radiators draining out along the bottom 
 of the pipes and back to the boiler by gravity, to be re-evaporated 
 into steam. Such a system as this could be applied only to a very 
 small plant, and one in which the pipes could be made comparative- 
 
 Figure 1. The One-pipe System. 
 
 JO, 
 
 
 1^^ 
 
 Q, ! 
 
 
 
 
 
 rj rt 
 
 
 o 
 
 
 
 
 O- 
 
 
 
 a 
 
 
 
 
 
 
 
 
 5^o/n Wa/>f. 
 
 ' 
 
 
 r Draln. 
 
 
 
 
 J 
 
 >Wr f tvet 
 
 0nm-* 
 
 0c//er 
 
 
 in ttoilv. 
 
 
 Figure 2. The Two-pipe System. 
 
 ly of large size and given a very decided fall toward the boiler from 
 all directions. 
 
 Two-pipe system. The more usual system of piping, and that 
 first employed, is known as the "two-pipe system," and is repre- 
 sented in Figure 2. In this, each radiator has one pipe for supply- 
 ing steam and another to remove the water of condensation. The 
 only object in the two-pipe connection is to provide a freer and 
 more positive flow of steam and condensed water, but this is a 
 
STEAM HEATING AND VENTILATION. 15 
 
 very important consideration. In a one-pipe system, such as indi- 
 cated by Figure 1, the water of condensation flows from the radia- 
 tors back to the boilers against the current of steam, falling 
 through the steam in the vertical pipes and flowing along the bot- 
 tom of the horizontal pipes. Such a simple system as this, shown 
 in Figure 1, might be employed, and to a considerable extent, if 
 the pipes are of ample size, and also if there are no valves on the 
 radiators, so that steam can be turned on the entire system at 
 all times. In this case there would be a constant and practically 
 uniform flow of water through the pipes, and, if these were prop- 
 erly laid out, the system might give perfect satisfaction. But it is 
 impracticable to have all the radiators of a system turned on at 
 one time, and the difficulty with such a system is made evident 
 the minute steam is turned into a cold radiator. When the steam 
 comes in contact with a perfectly cold radiator a large amount is 
 condensed at once in heating the cold iron, and as soon as the 
 pressure becomes adjusted this bulk of water flows out of the radia- 
 tor connection at one time and drops down the vertical pipe. When 
 it reaches the horizontal main in the basement it is picked up by 
 the current of steam and carried to other parts of the system, 
 filling up the pipes in places; and as it is relatively much colder 
 than the steam, the latter, in trying to get by it, is suddenly con- 
 densed, disturbing the equilibrium of pressure, as we might say, 
 and producing the disagreeable crackling and pounding noises 
 which are always encountered in poorly constructed heating sys- 
 tems, and which are commonly known undei the name of water- 
 hammer. This noise, besides being very annoying to the occupants 
 of the building, interferes with the circulation of steam and also 
 produces undue strains in the piping. 
 
 The two-pipe system to a certain extent does away with these 
 difficulties ; that is, in using the two-pipe connectioL it is generally 
 easier to avoid the water-hammer and other annoyances incident to 
 imperfect circulation; but unless the pipes are properly propor- 
 tioned and properly drained the sarrnj difficulties will be encoun- 
 tered. The simple one-pipe system, indicated in Figure 1, is there- 
 fore, as before stated, rarely, if ever, used, but there are a number 
 of modifications of it which are used with decided success, and in 
 some of the largest installations. 
 
 One-pipe system with separate return main. The simplest one- 
 pipe system usually employed is represented in Figure 3. In this 
 
16 
 
 STEAM HEATING AND VENTILATION. 
 
 the horizontal steam main in the basement is pitched so as to drain 
 away from the boiler, and at its extreme end a return pipe is con- 
 nected and led back to the boiler, entering it below the water-line. 
 In this way the flow of steam and water of condensation is in the 
 same direction in the mains, and upon the sudden condensation of 
 considerable steam, as will occur when turning steam into a cold 
 radiator, the water falls down the risers against the current of 
 steam; but in the main it is propelled along in the same direction 
 as the steam current. If the mains are extensive they can, more- 
 over, be drained at several different points. This system is exten- 
 sively used for residences and buildings of only a few stories in 
 height, and it has also been used in larger installations. The Chi- 
 cago Athletic Club, a building ten stories in height, is heated by 
 
 O .Oar. 
 
 Figure 3. A Common Type of One-pipe System. 
 
 exhaust steam with this system of piping with a pressure of not 
 over 2 pounds in the coldest weather, and with little, if any > 
 difficulty with water-hammer. In such a plant the risers as well 
 as the mains must be of ample size, and the latter must have suffi- 
 cient pitch and be thoroughly drained. The consideration of these 
 questions as affecting the size of the pipes will be taken up in a 
 subsequent chapter. 
 
 Mills' system. The only system of single-pipe connection which 
 has been very extensively .used in high buildings, such as the mod- 
 ern office building, is that known as the one-pipe overhead, or 
 Mills' system, and is indicated diagrammatically in Figure 4. In 
 this system the steam is conducted through a large main supply 
 pipe to the attic of the building, or to the ceiling of the top floor. 
 
STEAM HEATING AND VENTILATION. 
 
 17 
 
 and from this the mains extend around the building to supply the 
 risers. The risers are connected to the return mains in the base- 
 ment. It will be seen that in this system the current of steam 
 and water of condensation is everywhere in the same direction ex- 
 cept in the connections to the radiators, and the risers should be 
 sufficient in number so that these connections may be compara- 
 tively short. This arrangement has the very decided advantage 
 over the ordinary upward-supply one-pipe system that the water 
 of condensation that falls down the risers from the radiators does 
 not, when it reaches the horizontal pipe at the bottom, encounter 
 the main current of steam, as the horizontal pipe is only a drain 
 pipe, in which there is practically no steam current, and which is 
 designed solely to dispose of this water. 
 
 a 
 
 a 
 
 
 a 
 
 cr 
 
 cr 
 
 Floor. 
 
 L//.r 
 SL^w* 
 
 Q noon 
 
 a 
 
 a 
 
 
 a 
 
 
 a 
 
 a 
 
 ^n ^ 
 
 
 -a 
 
 cr 
 
 
 
 a 
 
 * | 
 
 
 cr 
 
 a 
 
 a 
 
 OLflto: 
 _Jasemenr. 
 
 a 
 
 a . .. 
 
 
 
 
 
 ffeturri. 
 
 3H 
 
 r 
 
 Rttvrn. 
 
 ~f 
 
 C- - 
 
 Figure 4. The Mills System. 
 
 Two-pipe, overhead system. The principle of the two-pipe system 
 is much the same in all cases, but special adaptations of it are made 
 to meet special conditions. There is, for example, a two-pipe over- 
 head system in which steam mains are in the attic as well as in the 
 one-pipe overhead, but there is a separate set of return risers 
 which connect with the return mains in the basement. But each 
 supply riser should also be drained into the basement returns. The 
 arrangement has been but very little used. 
 
 Drainage of pipes. It must be remembered that in any system 
 
18 STEAM HEATING AND VENTILATION. 
 
 there is always a certain amount of water in the supply mains and 
 risers due to the radiation from the pipes themselves. If the 
 pipes are thoroughly covered with a good non-conductor of heat 
 there is but very little water from this cause ; but little as it is, the 
 mains must be so run that it will flow to certain points, where it 
 must be drained into the return or into proper receptacles. If the 
 steam pipes are arranged so that water can accumulate at any 
 point, trouble is sure to follow. It is a fundamental principle in 
 steam heating that pipes shall be so graded that water of conden- 
 sation will tend, by the action of gravity, to flow with the current 
 of steam to certain points, where it can be properly drained off. 
 
 The various systems of piping are sometimes more or less com- 
 bined in the same installation, and when radiators are of very large 
 size they should, if possible, be given both a supply and return con- 
 nection, as the principal advantage of the double connection lies 
 in the internal circulation which tends toward the more rapid 
 removal of air and water. More will be said on the subject of 
 radiator connections in a subsequent chapter on radiators. 
 
 Gravity systems. In the preceding discussion and the accom- 
 panying diagrams we have assumed that the water of condensation 
 returns through the return pipes directly to the boiler, there to 
 be re-evaporated into steam by the fire on the grate. This is 
 what is known as the "gravity system" of steam supply, and is 
 self-regulating as to water consumption, except for such small 
 amounts of steam and water as may be lost by leaks. It is but one 
 of the many methods of steam supply, though the one now most 
 employed where the plant is used only for heating and there is 
 no steam power. 
 
 In the gravity system the water stands in the return pipes and 
 risers at practically the same level as that in the boiler, though in 
 the remote parts of the system it rises above the boiler level by a 
 height equivalent to the pressure required to effect the circula- 
 tion through the system. For this reason gravity systems should 
 l>e designed for free circulation, with pipes of ample size, the dif- 
 ference of pressure required between the steam mains and the 
 most extreme point of the returns never exceeding a pound or two 
 per square inch. Gravity systems are therefore generally run at 
 very low pressures, though frequently in very cold weather as much 
 as 15 pounds is carried for the sake of the higher temperature of 
 steam. The operation of this system is the same at any pressure. 
 
STEAM HEATING AND VENTILATION. 19 
 
 The gravity system is a comparatively recent development, the 
 earliest steam-heating systems being generally auxiliary to a steam- 
 power plant. In these the steam was taken direct from the boiler 
 supplying the engine, and the return water was run through a 
 steam trap into an open tank, from which the water supply was 
 taken for the boilers. This method is still employed in many 
 old plants. 
 
 Exhaust steam heating. The greater economy in high-pressure 
 steam for engines, however, gradually increased the boiler pressure 
 used for steam power, and with this increase in pressure it be- 
 came difficult to heat a building directly from the same boiler 
 that supplied steam to the engines, as steam heating at high press^ 
 ure was found unsatisfactory for many reasons, principally on ac- 
 count of the very high temperature of the radiators and the lia- 
 bility to leaks and the increased danger from water-hammer. And 
 furthermore, the same desire for greater economy which had in- 
 creased engine pressures drew the attention of steam users to 
 the value of the latent heat in exhaust steam for heating purposes. 
 
 A brief study of the steam engine shows us that not much over 
 12 per cent, of the heat energy supplied to an engine is transformed 
 into mechanical work, and by far the major part of the wasted heat 
 escapes in the latent heat of the exhaust steam. This heat, though 
 it has been thus far impossible to transform it into mechanical 
 energy, is readily available for heating purposes; but a generation 
 ago, when it was first proposed to use exhaust steam for heating, 
 the problem involved the then serious question of back pressure 
 on the engines. Heating systems at that time were built to ac- 
 commodate the high pressure then in use and with what would 
 now be called very small pipes, and admitting exhaust steam into 
 such a system required a considerable pressure on the exhaust side 
 of the engine to force steam through the piping and radiators and 
 the water of condensation out through the returns. 
 
 The back pressure necessary frequently amounted to 10 or 15 
 pounds per square inch, and certainly made a decided reduc- 
 tion in the economy of the engine. It at once became a question 
 whether the saving by using exhaust steam exceeded the loss on 
 account of the back pressure on the engine. If the back pressure 
 was very high in comparison to the mean pressure in the engine 
 cylinder there might be difficulties in the practical operation of 
 the engine ; but as far as the theoretical consideration of the coal 
 
20 STEAM HEATING AND VENTILATION. 
 
 pile goes, it is more economical to use exhaust steam even at a 
 high back pressure. 
 
 As heating systems are now designed, one which requires a 
 pressure of 5 pounds to ensure a good circulation is defective in 
 design, and 2 pounds is more than ought to be required in most 
 cases. A back pressure of this amount on an engine running at 
 50 pounds mean effective pressure would increase the coal con- 
 sumption but a fraction of 1 per cent., while taking the heating 
 power that is available in the exhaust steam directly from the 
 boiler would increase the coal consumption over 60 per cent. 
 
 Another consideration enters, however, into the question of cir- 
 culation in a steam-heating apparatus. Besides merely forcing the 
 steam and water through the radiators and piping, it is necessary 
 to force out the air which accumulates, and to do this the S3 r stem 
 must carry a pressure somewhat above that of the atmosphere, 
 unless a vacuum system, which will be described later, be used. 
 
 Theoretically it would be possible to operate a simple gravity 
 system below the atmospheric pressure if the whole system was per- 
 fectly air tight and the air was all boiled out of the water and 
 forced out of the system in the first place. In such a case if the 
 fires were put out and the system allowed to become cold, the con- 
 densation of steam would leave a perfect vacuum, and on starting 
 up the fire, steam could be carried at any pressure below or above 
 the atmospheric, according to the intensity of the fire. 
 
 But if it be attempted to run much below atmospheric pressure 
 the slightest leak anywhere in the system will rapidly break the 
 vacuum and allow air to accumulate. It is, however, impossible 
 to make a system theoretically air tight, and steam invariably 
 contains some air from the feed water, as water will absorb sev- 
 eral times its own volume. Air in the radiators and piping is, 
 therefore, an evil that cannot be avoided, and it rapidly accumu- 
 lates in the radiators or ends of pipes where the flow of steam is 
 slowest. Consequently an air valve is- almost a 'necessity on every 
 radiator, and those which are now almost universally used are au- 
 tomatic ; that is, they close as soon as the hot steam comes in con- 
 tact with them, and open if air accumulates and they become cold. 
 To some extent these automatic air valves enhance the air prob- 
 lem, inasmuch as when the radiator is cold it entirely fills with air 
 at atmospheric pressure. In any case the result of the presence of 
 air is that the pressure of steam in the system must be sufficient 
 
STEAM HEATING AND VENTILATION. 
 
 21 
 
 to force the air out, though for this purpose a fraction of a pound 
 above the atmospheric should suffice; and frequently better re- 
 sults are obtained with such a slight excess than with a greater 
 pressure. A subsequent chapter on radiators will discuss the action 
 of air and position of an air valve. 
 
 Arrangement of exhaust heating systems. This brings us to a 
 discussion of the methods by which low-pressure exhaust steam is 
 employed for heating. The simplest method, and the one usually 
 employed in exhaust-steam heating, consists in dividing the main 
 exhaust pipe, which receives the exhaust steam from all engines 
 and pumps about the steam plant, into two branches, one leading 
 to the atmosphere, the other being connected to the heating sys- 
 tem. On the pipe to the atmosphere is placed a back-pressure 
 valve, the object of which is to automatically maintain a uniform 
 pressure upon the exhaust and upon the heating system, so that 
 
 FiG.SA Fio.SB 
 
 Forms of Back-Pressure Valve. 
 
 the steam may flow into the heating system as fast as it condenses 
 in the radiators. Two forms of back-pressure valves are shown in 
 Figure 5, A and B, the essential feature consisting of a disk that is 
 weighted so that when the pressure on the inlet side exceeds a 
 certain amount the disk rises and allows sufficient steam to escape 
 to the atmosphere. The water formed by the condensation of 
 steam in the heating system is carried back through the main 
 return pipe to some kind of receiver, and is pumped into the boil- 
 ers. It is generally arranged to pass through some kind of an 
 
22 STEAM HEATING AND VENTILATION. 
 
 exhaust-steam feed-water heater on its way to the boiler. The 
 pump is also usually operated automatically, as will be discussed 
 later. 
 
 The feed-water heater is an essential in all steam plants, and its 
 purpose is to utilize as much as possible of the heat in the exhaust 
 steam in heating the water fed to the boiler. As, however, not 
 more than 18J per cent, of the exhaust steam can in any case be 
 required to heat the coldest feed water to the full temperature of 
 the exhaust steam, 212 degrees Fahr., there is always a con- 
 siderable quantity left, which can be utilized in heating the build- 
 ing; and furthermore, as the hot return water is always in one 
 way or another fed back to the boiler, the more steam that is re- 
 quired for the building the more return water there is and the less 
 steam is needed to heat cold feed water. If the heat in the exhaust 
 steam is not thus used in heating the feed water or heating the 
 building, or both, it would be wasted, and its equivalent in coal 
 would have to be used under the boiler to replace it. 
 
 There are two distinct classes of exhaust-steam feed-water heat- 
 ers; the closed or pressure heaters, and the open heaters. In the 
 former the feed water is pumped through the heater against the 
 boiler pressure; the exhaust steam passing into an inlet chamber,, 
 and generally through a series of tubes into the outlet chamber,, 
 the tubes being set in wrought-iron plates, which divide the inlet 
 and outlet chambers from the water space around the outside of 
 the tubes. In a water-tube heater the position of the steam and 
 water is reversed. In the open heater the water and steam are 
 practically together in the same chamber, the water flowing in 
 from some source against only the pressure of the exhaust steam. 
 The suction of the feed pump is connected to the heater and the 
 delivery direct to the boilers. With the closed heater cold water 
 is pumped through the heater to the boiler, while with the open 
 heater hot watei from the heater is pumped direct to the boiler. 
 
 The scheme of steam supply described is represented in Figure 
 6, and is, with various modifications of detail, almost universally 
 employed in heating systems in which exhaust steam is used. It 
 will be noticed that in the figure the pipe to the heating system is 
 provided with a live-steam connection. This is necessary in a 
 great many plants where, in extremely cold weather, the exhaust 
 steam is not sufficient to heat the building. In modern practice 
 such a connection is always provided with a reducing-pressure 
 
STEAM HEATING AND VENTILATION. 23 
 
 valve. These valves, one of which is represented by Figure 5 C, 
 are of such construction that they can be set for any desired differ- 
 ence between the highland low-pressure sides. The reducing valve 
 must always be set for a pressure somewhat 
 lower than that at which the back-pressure 
 valve opens, as otherwise some live steam from 
 the reducing valve might pass through the 
 back-pressure valve to the atmosphere and thus 
 be wasted. 
 
 Figure 7 shows an arrangement with a press- 
 ure heater which is much employed in steam- 
 heating systems. The exhaust steam enters 
 the bottom of the heater and goes out at the 
 top. The connection is also provided with a 
 by-pass so arranged that in case it is necessary 
 to shut out the heater for repairs or cleaning,, 
 the valve B in the by-pass may be opened and 
 the valves A and C closed, so that the steam will pass around 
 the heater. In ordinary use the valve B in the by-pass is closed 
 and A and C opened. The arrangement of the supply to the heat- 
 ing system, which is connected to the outlet of the heater, and. 
 
 * -Free Exhaust, 
 y Back-Pressure Valve. 
 
 Figure 6 Exhaust Steam-Heating Supply Connections. 
 
 the back-pressure valve on the free exhaust, is the same as indi- 
 cated in Figure 6. The main return pipe is run into a cylindrical 
 receiving tank, from which the water is pumped through the 
 heater. Attached, to the receiving tank is an automatic pump 
 governor, which, by means of a float operating on the steam sup- 
 
 /& 
 
 /ir -. 
 
 I UNIVERSITY , 
 
24 
 
 STEAM HEATING AND VENTILATION. 
 
 ply to the pump, regulates the level of water in the receiving tank. 
 As soon as the water in the tank rises above the proper level the 
 pump is started by the float, and when it falls below this level 
 the pump is stopped. 
 
 Figure 8 represents an arrangement with an open heater. The 
 steam connection is precisely similar in principle, but a different 
 arrangement of details is indicated, the valves being lettered to 
 correspond with those in Figure 7. The returns are run into a 
 receiving tank similar to the other arrangement, but this tank 
 
 t free Exhaust to Open Air. 
 Back- Pressure Valve. 
 
 Main Supply to Heating System. 
 
 Water Level in Returns. 
 I \ Main Return 
 
 Glass. {Receiving 
 
 Figure 7 Arrangement with Pressure Heater. 
 
 is connected directly to the heater, and practically forms a part 
 of it. The automatic float which controls the operation of the 
 pump is generally, in such cases, connected directly on to the heat- 
 er, as indicated in the governor marked D. 
 
 In Figure 8, on the left of the heater, is indicated another float 
 governor, E, which is frequently attached to heaters of this charac- 
 ter. This operates on the cold-water supply. In this connection 
 it will be noted that frequently in moderate weather only a portion 
 of the exhaust steam is needed to heat the building, the remainder 
 escaping through the back-pressure valve. In such cases it is neces- 
 sary to make up the loss of water by taking a certain amount from 
 the city mains or other source of supply. With the open type of 
 
STEAM HEATING AND VENTILATION. 
 
 25 
 
 heater this is generally run directly into the heater and sprayed 
 through the current of exhaust steam. It is for the control of 
 this cold-water supply that the governor, E, is provided. In this 
 case the governor on the cold-water supply should be set for a 
 level of water a few inches below the level which operates the feed 
 pump. Otherwise the cold water might be let into the heater while 
 the pump was running and when it was not needed. The open 
 heater should in all cases be provided with an overflow connected 
 to a low-pressure trap. This outlet should be a few inches above 
 
 live Steam. 
 
 Supply to' Heating System. 
 
 W////^///yM^///y//^ 
 
 Figure 8 Arrangement with Open Heater. 
 
 the water-line, but should be low enough to prevent the possibility 
 of a sudden inflow of return water flooding the exhaust pipes. 
 
 With the arrangement shown in Figure 7 the cold water may be 
 supplied by a pipe running direct to the receiving tank, and it may 
 be regulated by hand, according to the level of the water, shown 
 by the gauge glass, or by a float governor similar to the one indi- 
 cated on the open heater in Figure 8. 
 
 In large plants also there are frequently two or more feed pumps, 
 one of which has a suction connected to the cold-water supply, or 
 the boilers are provided with injectors. Further details of piping 
 will be discussed in a subsequent chapter. 
 
 It will be seen that, in connection with the open heater, the re- 
 
26 STEAM HEATING AND VENTILATION. 
 
 ceiving tank is merely a part of the heater, forming an additional 
 reservoir for the return water. It is possible to do away with the 
 tank entirely, connecting the returns direct into the water cham- 
 ber of the heater, but as the water space of the heater is generally 
 comparatively limited, the water level in such cases is subject to 
 more or less extreme fluctuations, due to the fact that the return 
 water does not always come back with a uniform flow. This is 
 especially the case with large office buildings, when the building 
 is being heated in the morning and a number of cold radiators are 
 apt to be turned on at nearly the same time. In the same way it 
 is possible also to do away with the receiving tank represented in 
 Figure 7, but this is subject to the same objection as in the other 
 case, only to a more extreme degree, as the small governor pro- 
 vides scarcely any reservoir volume for the return water and the 
 pump is subject to sudden changes in speed. In the arrangement 
 shown in Figure 7 the main return pipe is generally connected at 
 the point, F, and not directly to the tank. 
 
 The writer has installed a number of large plants with open 
 heaters and no receiving tanks whatever which have given perfect 
 satisfaction; and recently installed a plant having over 16,000 
 square feet of radiating surface with practically the same arrange- 
 ment as indicated in Figure 7, but without any receiving tank. 
 This system requires rather careful attention, especially in the 
 early morning, but it was impracticable on account of local condi- 
 tions to put in a receiving tank, and the system has given thorough 
 satisfaction. 
 
 It should be noted here that the system represented in Figure 8 
 is practically a gravity system, the heater and tank taking the 
 place of the boiler represented in Figures 1 to 4, and acting both 
 as steam-producing chamber and reservoir for return water, both 
 being at this point under precisely the same pressure. The water 
 level in the return pipes and return risers will stand at a higher 
 level than in the heater or boiler in the case of Figures 1 to 4, by 
 a distance representing the difference in pressure required to force 
 the steam through the system, just as in the ordinary gravity sys- 
 tem. As a matter of fact, also, it is found that in the system 
 shown in Figure 7 the pump operates much more smoothly and 
 ;uniformly if the system is made a gravity system by connecting 
 a small equalizing steam pipe between the main steam supply of 
 -the heating system and the top of the receiving tank and governor. 
 
STEAM HEATING AND VENTILATION. 27 
 
 If the plant referred to operates without a tank this equalizing 
 pipe is found to be practically a necessity. In any case an equaliz- 
 ing pipe above the water line between the heater and its tank, or 
 the heater and the governor, is necessary to maintain the same, 
 pressure upon the water in the tank as exists elsewhere in the re- 
 turn-water reservoirs. 
 
 The water-line of the heating system sometimes becomes an 
 important consideration,, especially when it is desired to place 
 radiators in the basement of a building. If these are set so low 
 that the return water is liable to rise above the connections, the 
 radiators will fill with water when turned on, which will prevent 
 the steam from circulating into the radiator and will be sure to 
 give trouble from water-hammer. Besides this, with anything 
 except the overhead-supply systems, the water from the returns 
 will back through the radiator and run down the supply riser, and 
 it is therefore generally necessary to set radiators several feet 
 above the water-line, according to the maximum pressure which 
 is necessary to create circulation of steam through the system in 
 coldest weathp* If the system is designed for very low pressure, 
 1 or 2 pounds, the radiator may be placed within 4 feet of the 
 water-line, but should never be lower than this, especially in 
 parts of the building far removed from the heater. For this 
 reason basements are usually heated by steam coils suspended from 
 the ceiling or placed on the walls, near the ceiling, although radi- 
 ators are sometimes put on brackets attached to the walls; fre- 
 quently, in order to lower the water-line, the pump, governor, and 
 heater also, when the open heater is used, are placed in a pit. There 
 are, however, special arrangements of radiator connections which, 
 may be used with safety, even though they are set below the water 
 line. These are discussed in the chapter on radiators. 
 
 There are many combined automatic pumps and receivers de- 
 signed for taking care of the return water which are very satis- 
 factory, but all work on the same principle of a tank with a float 
 governor to operate the pump. There are also automatic traps de- 
 signed to return the water of condensation from the exhaust-steam 
 heating systems, without using a pump, direct to a high-pressure 
 boiler by means of an ingenious combination of float valves, traps, 
 reservoirs and check valves, and some of these work with consid- 
 erable satisfaction if carefully watched and kept in good repair. 
 
 In many mills and factories which use condensing engines, and 
 
28 STEAM HEATING AND VENTILATION. 
 
 in which, consequently,, exhaust steam is not readily available for 
 heating, steam for this purpose is taken direct from the boilers 
 through a, reducing pressure valve and used in the heating system 
 at a pressure of 5 to 20 pounds per square inch. In such systems 
 the water is generally returned to the boilers by an automatic pump 
 and receiver, or by one of the special styles of traps referred to, 
 which for operating at such pressures can be made much simpler 
 than when used for the extremely low pressure of the ordinary 
 exhaust systems. 
 
 Vacuum systems. As a refinement of exhaust-steam heating 
 there has been developed within the last decade what is known as 
 vacuum systems of steam heating, the object of these being to ex- 
 haust the air from the system by artificial means so that circulation 
 may be effected at atmospheric pressures with absolutely no back 
 pressure on the exhaust pipes from the engines. There are two 
 distinct forms, one known as the Paul system, the other as the 
 Webster. The former system provides each radiator with an auto- 
 matic air valve of special construction and connects a very small 
 pipe, usually | inch, to each of these valves, bringing them together 
 in pipes of proper size in the basement of the building, and con- 
 necting to a special exhauster, which maintains a constant suc- 
 tion on the entire system of air piping. The steam and return 
 pipes for this system are entirely independent of the air pipe and 
 it may be installed on any of the systems previously mentioned. 
 
 The Webster system operates on an entirely different principle, 
 in that it employs an automatic air-and-water valve at the return 
 outlet of the radiator. This thermostatic valve, as it is called, is 
 constructed on a principle much like the automatic air' valve, but 
 is of larger proportions. It is adjusted so that it closes automati- 
 cally when it comes in contact with the steam temperature, and 
 opens when water or air collects about it, and the temperature is 
 reduced. The system is necessarily a two-pipe system, the returns 
 being connected to these thermostatic valves, but no other air 
 valves or air piping are used. The return pipes are connected in 
 the basement to a vacuum pump which puts a strong suction on 
 the returns, and by means of which both air and water are drawn 
 through the thermostatic valves, the water being delivered by the 
 vacuum pump to an open heater or receiving tank, while the air 
 is separated by an automatic device. The return pipes of this 
 system are very small, just sufficient to take care of the water, no 
 
STEAM HEATING AND VENTILATION. 29 
 
 steam being allowed to circulate in them. The steam mains, where 
 necessary, are drained into the return pipes through thermostatio 
 valves. The return mains being under suction, and having 110 
 direct connection with the steam pipes, can, a certain extent, 
 be run independent of the usual necessity of draining by gravity, 
 in some cases the water being lifted out of radiators placed below 
 the return -mains. 
 
 In the Union Depot at Columbus, Ohio, which is equipped with 
 this system, the radiators in the basement are about 13 feet below 
 the supply and return mains, which run parallel along the base- 
 ment ceiling, and the return water is drawn up out of the radiators 
 without any water-hammer or other inconvenience. 
 
 A modification of the Paul system was recently installed in a 
 large office building in Chicago which has given decided satisfac- 
 tion. Instead of the air valve on each radiator, a small tee with 
 an aperture only 1/16 inch in diameter was screwed into the air 
 hole of the radiator, and these connected together into a system 
 of small air pipes running to an air pump or exhauster. This 
 maintains a constant suction on the air holes. Although there is 
 apparently a continual leakage of steam in this system,, it is not 
 more than with the automatic air valves, as the latter are seldom 
 maintained in perfect adjustment. The tees were made w r ith a 
 plug on the outside which could be removed for the purpose of 
 cleaning the pin-hole by means of a wire. 
 
 Plants equipped with vacuum systems frequently operate slight- 
 ly below the atmospheric pressure, and besides entirely doing 
 away with back pressure on engines and removing the air from 
 the system, there are many incidental advantages in the operation 
 of plants of this character which will lead to a very extended 
 adoption. The principal objection to vacuum systems lies in the 
 fact that the exhausters or vacuum pumps take considerable live 
 steam to operate them, and almost as much in moderate weather 
 as on very cold days. 
 
 The recent development of vacuum pumps, however, has been 
 of great value to steam-heating work. Pumps of this class are 
 now made which will not run away when all the water is pumped 
 out of the suction, the water end of the pump receiving only air 
 and steam. They will run along slowly under such conditions, 
 taking care of the water as it comes. If a pump of this descrip- 
 tion is connected to the lower point of the main return from 
 
30 STEAM HEATING AND VENTILATION. 
 
 e heating system, it can be made to maintain what is now called 
 a dry return. This is in some cases valuable, as it obviates the 
 necessity of considering the water-line, as before mentioned, in 
 placing radiators in basements. Vacuum pumps used in this way 
 are especially valuable in cases where return water is to be brought 
 l>ack from a heating system at some distance from the source of 
 steam supply. 
 
CHAPTEE III. STEAM-HEATING APPARATUS. 
 
 Boilers. The questions of boiler design, construction, setting, 
 etc., involve so many considerations requiring careful scientific 
 study, that the entire problem is omitted from this work and the 
 reader is referred to the valuable treatises devoted exclusively to 
 the subject. There is, however, one kind of boiler which should be 
 given some special mention- in this place. This is the self-contained 
 cast-iron sectional boiler which is used only for small, low-pressure 
 gravity-heating systems in residences. These boilers are built up 
 in sections of various shapes bolted together, the joints being kept 
 tight merely by the pressure caused by the bolts. On account of 
 their material, as well as the method of construction, they are 
 not adapted for anything but very low pressures. For the larger 
 plants in which cast-iron boilers are used, it is better to install 
 two small ones than to attempt to use one large one, as it gives 
 better economy in operation, and there is less danger of accident 
 to small boilers than to those with large castings. 
 
 In selecting these boilers it should always be borne in miud 
 that the demands of commercial competition cause them to be 
 very generally overrated by their makers, so that in choosing sizes 
 from catalogues it is advisable to make considerable reduction from 
 the rated capacities. Mr. James R. Willett, in a pamphlet on the 
 heating and ventilating of residences, gives the accompanying table 
 for the sizes of cast-iron boilers. Where boilers of the kinds used 
 for steam power are employed in simple heating plants of large 
 size of which there are to-day but few there is an old rule for 
 proportioning the size, to the effect that there must be 1 square 
 foot of boiler surface to 10 square feet of radiating surface. This 
 rule when applied to a boiler with a well-designed furnace, stack 
 and setting should be very conservative. It is much better to 
 estimate the steam consumption of the entire plant (see Chapter 
 V., page 60 for steam consumption of radiation) and calculate 
 the boiler requirements according to the rules of boiler design. 
 The designs of the cast-iron heating boilers are innumerable and 
 
32 
 
 STEAM HEATING AND VENTILATION. 
 
 can only be selected by the careful judgment of the engineer. The- 
 chief points to be considered -are efficiency of heating surface and 
 capacity of grate in proportion to surface, strength of parts, tight- 
 ness of joints, ease of cleaning and effectiveness of circulation 
 there should be no "dead ends" where the water is not kept in 
 circulation by the heat of the fire. 
 
 Willett's Table of Cast-iron Boiler Capacities. 
 
 Radiators; Area of boiler Radiators; Area of boiler 
 
 total sq. ft. grate in sq. in. total sq. ft. grate in sq. in. 
 
 400 500 1,600 1,420 
 
 500 580 1,800 1,560 
 
 600 650 2,000 1,700 
 
 700 740 2,250 1,880 
 
 800 820 2,500 2,020 
 
 900 890 2,750 2,230 
 
 1,000 970 3,000 2,400 
 
 1,200 1,120 3,500 2,770 
 
 1,400 1,270 4,000 3,120 
 
 There might also be classed under the head of steam-heating 
 apparatus the various traps, automatic receivers and other special 
 
 4pt 
 
 iiiliiiHaa 
 
 Fio.9 
 
 FiG.IO FIG. II 
 
 One, Two and Three Column Radiators. 
 
 appliances which are used especially in connection with exhaust 
 heating for returning the water of condensation to the boiler, 
 and which were described in the preceding chapter. But besides 
 these the only apparatus pertaining to a heating system without 
 
STEAM HEATING AND VENTILATION. 
 
 33 
 
 mechanical ventilation are the radiators, and in the design of the 
 system the rtmost consideration should be given to their selection 
 and proportioning. 
 
 Radiators. Radiators are made either of cast or wrought iron 
 and are classified according to kind of heating for which they are 
 used into direct, direct-indirect, and indirect radiators. A few 
 years ago wrought-iron pipe made up with bends and headers into 
 coils of various sizes and shapes was used very largely for radia- 
 tors, and especially for indirect radiators; but on account of their 
 greater economy of construction, cast-iron radiators are rapidly 
 supplanting the wrought-iron pipes for all purposes. To-day 
 
 FIG. 12 
 
 wrought-iron pipe coils are used in direct heating where very large 
 radiators are required spread over a large area of wall surface., 
 such as in factory rooms or warehouses, where a series of long^ 
 pipes connected into headers at each end are run along the walls-, 
 either over'or under the windows, preferably under. Pipe coils are- 
 also used for large indirect radiators, but in this case, as a rule, , 
 only in connection with ventilating fans, as will be described in 
 subsequent chapters. 
 
 The styles and kinds of cast-iron radiators 'are innumerable.. 
 They are made in sections or loops, which are fastened together 
 
34 STEAM HEATING AND VENTILATION. 
 
 by pipe nipples of various kinds, with a paper or thin metal gasket 
 between the faced surfaces of the joint. These nipples are some- 
 times threaded and screwed up tight by special wrenches, but what 
 is known as the push-nipple is extensively used. These nipples 
 are not threaded but are turned to a close fit with the holes in the 
 loops, at the joint, which are bored out perfectly true, and they are 
 driven tight by pressure with jacks or presses made for the pur- 
 pose. 
 
 Cast-iron radiators are classified according to the kind of sur- 
 face, into plain-surface and extension-surface radiators, and ac- 
 cording to their style of construction into open and flue radiators, 
 &nd of the open one, two, three and four column type, according 
 to the formation of the loops. The different classifications will be 
 better understood from inspection of the accompanying illustra- 
 tions. The extension-surface radiators, Figures 14 and 18, as 
 the name implies, have extensions of various kinds in the form of 
 ridges or pins cast on to the otherwise plain surface, and are used 
 principally for indirect radiators. The flue radiators, Figure 1C, 
 are used extensively for direct-indirect radiation, but for such pur- 
 pose are provided with shields and provision of some kind for con- 
 nection with the outer air. Flue radiators, such as shown in Fig- 
 ures 12 and 13, are sometimes spoken of as veiled-surface radiators. 
 Most low radiators of considerable width in proportion to the 
 lieight are of the flue type. The radiator that has been used for 
 direct radiation much more widely than any other is the two- 
 column plain-surface radiator, such as is shown in Figure 10, but 
 the numerous other forms are being more and more extensively 
 introduced. 
 
 . Most radiators for steam heating have all the loops connected 
 by only one steam passage through the bottom, but some are also 
 connected at the top as well. Such radiators are adapted to steam 
 heating from hot-water heating practice, as they are the only 
 kind that can be used in the latter, and are hence known as the 
 hot-water type. See Figure 20. Almost all low and wide steam 
 radiators are made in this way, and by some authorities this con- 
 struction is preferred in all kinds. Further discussion of this sub- 
 ject will be taken up later. 
 
 Measuring radiators. Eadiators are universally rated by the 
 number of square feet of surface which they contain. This, at the 
 present time, is for many reasons a very arbitrary method and 
 
STEAM HEATING AND VENTILATION. 
 
 holds chiefly for want of a better. The main difficulty lies in the 
 great difference in the value of the various kinds of surfaces, no 
 distinction being made in such rating between plain, extension or 
 veiled surface. The variation is enhanced also by the fact that 
 radiators are to a large extent overrated, especially in the less com- 
 mon sizes and styles; and owing to the difficulty of accurately 
 measuring the surface, this fact is very generally overlooked. A 
 number of methods have been proposed and tried for measuring 
 the surface of radiators which are made in ornamental design and 
 with all kinds of irregular surfaces. In the course of a large ex- 
 perience with radiators of all kinds, the author tried many different 
 methods and finally devised one which he has found comparatively 
 
 ; 
 
 Fio.15 
 
 
 Direct 
 
 FIG. 16 
 
 Indirect Radiators. 
 
 FIG. 17 
 
 THE ENGINEERING 
 
 simple and very reliable. By this method all irregular surfaced are 
 measured by covering them with very thin flexible paper which 
 must be carefully turned and folded into all irregularities of the 
 surface. After being thus fitted, the paper should be rubbed by 
 blackened fingers. They are generally sufficiently soiled for the 
 purpose from handling the radiators. In this way when the paper 
 is spread out, the part that was folded under can be readily distin- 
 guished, and the actual area of the surface can be determined by 
 measuring the blackened parts with a planimeter. In lieu of a 
 planimeter, thin cross-section paper can be used and the areas de- 
 termined by counting the small squares. In measuring up a ra- 
 diator loop, it is best to divide the surface by thin lines of white 
 chalk or paint and measure each division separately. The parts 
 
36 
 
 STEAM HEATING AND VENTILATION. 
 
 that have a uniform cross-section, as the columns of most direct 
 radiators, can be measured by determining the actual circumfer- 
 ence of the surface by fitting a paper around it and multiplying 
 this by the length of the column. It was once objected to this 
 method that it does not take into account the effect of the raised 
 ornamentation on a radiator. This is not the case, or at least any 
 ornament that it does not take into account would not increase 
 the total surface to an appreciable degree. Measurements of ra- 
 diators by this method by different observers acting independently 
 have been found to check within less than I per cent. 
 
 FlO.18 Indirect Radiator. 
 
 Action of radiators. Before proceeding further in the discussion 
 of radiators, it may be well to consider some of the principles which 
 govern their operation in practical use. The fundamental prin- 
 ciple of their, operation is undoubtedly the axiomatic theory that 
 there is a universal tendency toward the equalization of tempera- 
 ture; in other words, that hot bodies give up their heat to the 
 colder ones which surround them. In general this is accomplished 
 by three different processes, namely: conduction, convection and 
 radiation, the word radiation being used here in the special sense 
 of -radiant heat. These may best be defined by illustrations. When 
 one part of a rigid body is in contact with a warmer body heat 
 passes or flows from the latter through the former to its cold por- 
 
STEAM HEATING AND VENTILATION. 
 
 37 
 
 lions as long as there is any difference of temperature. This is 
 conduction of heat, and the rate of flow under the same conditions 
 of temperature varies as a factor known as the heat conductivity 
 of the body concerned. The heat conductivity of fluids, liquids 
 and gases is very low, practically zero, but heat is transferred in 
 them by convection. The particles in direct contact with the 
 source of heat are heated above the temperature of the rest, and an 
 increase in temperature of any liquid or gas invariably decreases 
 
 p 
 
 ujy 
 
 FIG. 2O Hot- Water and Steam Pipe Loops. 
 
 THE IKCJNttHIHQ BAQ, 
 
 its specific gravity and causes an upward current of the hot parti- 
 cles, which brings the colder particles in turn in contact with the 
 hot body, thus maintaining a circulation which tends to raise the 
 temperature of the entire mass. Eadiation or radiant heat is en- 
 tirely different from either of -these in its action. It is a wave 
 motion and travels through air and all transparent bodies with 
 the velocity of light without heating them, and only appears as 
 sensible heat when its course is interrupted by opaque bodies by 
 which it is absorbed.* 
 
 *Some bodies which are quite opaque to light waves are more or less 
 transparent to heat waves, and vice versa, and nothing except the im- 
 material ether is absolutely transparent to them. The earth's atmos- 
 phere absorbs a considerable amount of the radiant heat from the sun. 
 
38 STEAM HEATING AND VENTILATION. 
 
 A radiator gives out its heat to its surroundings by radiation to 
 the walls and objects and by convection to the air. What propor- 
 tion is given out in each way it is difficult to measure in any case 
 and depends principally on the construction of the radiator and 
 the way it is set, but also more or less upon the conditions of tem- 
 perature, nature of surface, etc. Peclet, the great French physi- 
 cist, in the middle of the century, fully investigated the laws of ra- 
 diant heat as well as those of convection in still air. The formulas 
 which he deduced are applicable only in a limited degree to ra- 
 diator practice. His investigations, as well as those of others since 
 that time, showed that for a single iron pipe in still air* under 
 conditions of temperature which prevail in radiator practice, the 
 heat given off as radiant heat is just about equal to that given out 
 by convection. t 
 
 But radiators are invariably built of clusters of pipes or sur- 
 faces, and as radiant heat travels only in straight lines and per- 
 pendicular to the surface of its source, a large proportion of the 
 surface is wasted so far as radiant heat is concerned, due to what 
 may be called the mutual interception of the rays. In the ordi- 
 nary one-column cast-iron radiator, the proportion of surface from 
 which no radiant heat takes place is nearly 20 per cent., in the 
 two-column, 45 to 55 per cent, and in the three-column, 55 to 65. 
 Assuming that the radiant heat amounts to one-half the total, the 
 reduction of heat emitted would be one-half of these percentages. 
 Another fact which further reduces the radiant heat is that ra- 
 diators are usually set very close to a wall which becomes heated 
 to a comparatively high degree and consequently radiates back a 
 large portion of the heat to the wall side of the radiator. This is 
 true to an extreme degree in the case of indirect radiators which 
 are enclosed in boxes of wood or sheet metal and are not located in 
 the room they are to warm. With these the heating is accom- 
 plished entirely by convection, while with direct radiators the ra- 
 diant heat rarely amounts to 40 per cent., generally not over 30, 
 and often in practice considerably less. For a radiator in any par- 
 ticular location the radiant heat is constant for the same conditions 
 
 *By "still air" in this sense is meant the air of a room in which there 
 are no currents except those created by a column of hot air rising from 
 the heated surface. 
 
 tFor a complete account of Peclet's experiments and his results see 
 "A Treatise on Heat" by Thos. Box; London: E. & T. N. Spon. 
 
STEAM HEATING AND VENTILATION. 39> 
 
 of temperature of the radiator and surrounding objects, and is in- 
 dependent of currents of air. This is by no means the case with 
 the convected heat, which is increased greatly by a slight draft 
 from any extraneous source. In this connection it is very remark- 
 able what a great effect an almost imperceptible draft will have on 
 the heat given out by a radiator. This is partly due to the lower- 
 ing of the temperature of the air between the loops, but also to the 
 fact that with the same temperatures any increase in velocity in- 
 creases the amount of heat the air absorbs. 
 
 Radiator tests. Numerous tests of radiators have been made 
 since those of Mills, Eichards and others in the early '70's, bur 
 there is a wide variation in the results obtained, due partly to the 
 different kinds of radiators tested and partly to the different meth- 
 ods of testing. As yet, no standard means of testing radiators has 
 been adopted. The steam radiator as a heat-using device is theo- 
 retically perfect; that is, all of the heat that is put into the ra- 
 diator by the latent heat of the steam condensed is given out to 
 the air and objects surrounding. Its efficiency is therefore 100 
 per cent. The question of practical efficiency is, therefore, more 
 strictly speaking, only one of effectiveness of surface. That is, 
 of two radiators under exactly the same conditions of tempera- 
 ture and surroundings, that one which has such an arrangement of 
 its surfaces as to give out the most heat per square foot is the 
 most effective, usually called the most efficient. In all tests of 
 radiators, the heat given off is measured by connecting them so 
 that the steam which condenses can be accurately weighed, its 
 pressure, quality and temperature being determined at the same 
 time. The results are generally reduced to British thermal units 
 given off per square foot per hour per degree difference of tem- 
 perature between the air of the room and the steam of the ra- 
 diator. 
 
 Tests of radiators have been made in various ways by Mr. George 
 H. Barrus, by Profs. Denton and Jacobus of the Stevens Institute, 
 by Prof. R. C. Carpenter, of Sibley College, Cornell University, 
 and by the author. The results of Prof. Carpenter's tests are pub- 
 lished in detail in his valuable work on "Heating and Ventilation 
 of Buildings.'' In these tests the radiators were located in sepa- 
 rate compartments, 7 xlO feet, built together in a large room, and 
 as shown in Figures 21 and 22. In order to allow some circulation 
 of air so that the temperature of air of the compartments might 
 
40 
 
 STEAM HEATING AND VENTILATION. 
 
 not get as high as that of the radiators, small openings were made 
 in each at the bottom and top. In 1895 and 1896 the author had 
 occasion to make comparative tests of a large numher of radiators 
 of various kinds and types, and the arrangement used by him for 
 testing is shown in Figures 23 to 25. The two test rooms were 
 built in the main floor of a large warehouse, and each was 15 feet 
 by 11 feet 8 inches, and extended to the ceiling, 15 feet 5 inches 
 high. The walls of the test rooms were built of matched and 
 beaded pine and lined with lapped courses of heavy building paper. 
 The warehouse room in which the test rooms were located was 
 
 Fl G. 2 1 Prof. Co rpente r's Arrangement for Testing Radiators. 
 
 about 85 by 50 feet, with brick walls on both sides and wood and 
 glass partitions at each end. Neither end of this large room, how- 
 ever, was open to the outside air and the side walls were party 
 walls. Every effort was made to keep the air of the test rooms 
 free from all drafts except those induced by the column of hot air 
 rising from the radiators and to otherwise make the conditions as 
 nearly as possible those of actual practice. To permit some cir- 
 culation in the test room, so that the air would not get too hot, 
 an opening 4 inches long and 1 8 inches high was cut in the front 
 
STEAM HEATING AND VENTILATION. 
 
 41 
 
 wall at the floor, and to prevent direct drafts on the radiators, 
 those openings were surrounded inside by a wooden screen, 2 feet 8 
 inches high. The front partition was also opened 18 inches at the 
 ceiling. The piping, as shown in Figure 25, was arranged so that 
 the steam was supplied to the radiators on what is known as the 
 one-pipe overhead system. Steam was supplied to the separator 
 at a pressure of 2 or 3 pounds above atmosphere through a 2-inch 
 pipe from a small heating boiler. The pressure carried at tho 
 boiler was slightly in excess of that on the separator, it being 
 throttled at the latter. By this means and by leaving the drip on 
 the separator slightly opened, the steam was supplied free from 
 all entrained moisture. The piping, separator, etc., were all care- 
 fully covered. The heat given off was measured by drawing off the 
 condensed steam from the drip pots into cold water and accurately 
 weighing it. 
 
 FlG. 22 Prof Carpenter's Arrangement 
 of Each Radiator and Compartment Removed 
 
 In practically all of the tests made in this plant, one radiator 
 was used as a standard and all the others tested and compared with 
 it In each test the radiators were connected and a preliminary 
 run made with open air-valves until the conditions became con- 
 stant and uniform, and a test run made for two to three hours. The 
 radiators were then interchanged and the test repeated. Even 
 with these precautions it was only by exercising the greatest care 
 that it was possible to obtain results which checked closely. It is 
 very remarkable what a decided effect can be created by a very 
 
42 
 
 STEAM HEATING AND VENTILATION. 
 
 slight motion of the air from an external source. Opening a door 
 at one end of the warehouse room, although, as before stated, these 
 doors did not open outdoors, made a decided difference, and if a 
 strong wind was blowing outside, the radiator to the windward side 
 
 Ceiling of Wardroom. . 
 
 
 to- f || 
 
 
 
 Opening for Air. 
 
 
 
 Door 
 Opening 
 for Air. 
 
 Door. 
 
 '///v//////////////////////////////////////////////////////////// /////. 
 FIG. 23 Front Elevation of Testing Rooms. 
 
 Brick Wail of Wareroom. 
 ty//////////////////////////////////////////////////////////////////. 
 
 
 Radiator 
 
 Room A. 
 , Partition 2'8"Hiqh in front 
 ( of Opening at Floor. 
 
 \^\ \ 
 
 Radiator. ^ 
 
 so Room B. 
 I 
 
 
 
 
 FIG. 24- Plan of Testinq Rooms. 
 
 Twe EnoOiUniMO P 
 
 (Partition between Rooms. 
 Floor of Testing Room . 
 
 rio.25 Elevation of Piping.Radiator Tests 
 
 Dnp Pot-^ 
 4'Pipt. IG'Lony. 
 
 had some advantage, although no draft would be perceptible. 
 However, with due care, the two tests for each comparison were 
 made to check with fair accuracy. 
 
STEAM HEATING AND VENTILATION. 43 
 
 The radiator used as the standard on these tests was an ordinary 
 cast-iron two-column steam radiator, 38 inches high, with but little 
 ornamentation. The writer believes that this is the only way of 
 accurately testing radiators, and the adoption of any one definite 
 make of radiator as a universal standard of comparison would do 
 much to extend the knowledge of the comparative effect and value 
 of radiators. Tests of radiators made in different ways or in dif- 
 ferent locations are valueless for accurate comparison. But all 
 comparative tests made against the same standard if accurately 
 and carefully carried out, could be compared in percentages of the 
 heating effect of the standard used. The writer found that under 
 tne conditions in his testing plant the 38-inch two-column cast- 
 iron radiator used as a standard gave out 1.60 British thermal units 
 per square foot per hour per degree difference of temperature with 
 an average steam temperature of 224 degrees Fahr., and aver- 
 age temperatures of the rooms of 76.5 degrees. The average 
 difference of temperatures was 147.5 degrees. 
 
 This cofficient of 1.6 B. T. U. per square foot per hour per de- 
 gree difference of tempt ra~u~"2 between the steam and air is some- 
 what lower than that which Prof. Carpenter obtained for a ra- 
 diator of almost the same size and design. Assuming that the ra- 
 diators were exactly alike, such variation as there was can be due 
 to two causes: 1, a variation in the difference of temperature be- 
 tween the steam and the surrounding room; and 2, the mode of 
 setting and the consequent freedom of air circulation around the 
 radiator. In regard to the first cause, all tests of radiating sur- 
 faces from Peclet down show that the coefficient is greater, the 
 greater the difference of temperature, and for extreme variations 
 in the difference of temperature, the coefficient is very much great- 
 er than in the limits of ordinary radiator practice, with steam tem- 
 peratures from 212 to 230 and mean air temperatures from 40 
 to 70; within which range the variation in the coefficient from 
 this cause is less than 9 per cent. In regard to the second 
 cause the freedom of the air-circulation around the radiator 
 this is by far the. chief cause of difference in action of radia- 
 tors. Profs. Denton and Jacobus of the Stevens Institute of 
 Technology made some comparative tests of radiators, published 
 in The Engineering P n cord of September 8, 1894, with a plant very 
 similar to that used by the author, except, besides having an open- 
 ing at the top, there was in each of the test rooms an outside win- 
 
44 STEAM HEATING AND VENTILATION. 
 
 dow, "which was opened a certain amount during the tests" a 
 dangerous way, the author believes, to test radiators with the ex- 
 pectation of jbtaining checking results although "a screen was 
 placed between the radiators and windows to prevent direct drafts 
 from striking the radiators/' These tests were unquestionably 
 carefully made and were checked by reversing the position of the 
 radiators, so that the comparative results obtained may be taken 
 as reliable; but the coefficients were in the neighborhood of 20 per 
 cent, higher than that obtained by the writer on similar radiators, 
 due entirely to the greater freedom of air-circulation from the 
 open windows. This is a matter of great importance in practice 
 and in consequence the results obtained in radiator tests depend 
 largely upon the setting of the radiator. It is this fact also which 
 makes a radiator to some extent automatic or self -adjustable. 
 Take for example, an ordinary room say with a north exposure and 
 one direct radiator set, as they generally are and always should 
 be, under the window. On a moderately cold day with the ther- 
 mometer outside at 20 degrees and the wind from the south or 
 east, the radiator will be turned on the entire time. On another 
 day with the thermometer outside at zero and the wind from the 
 north, the radiator very probably keeps the room at the same 
 mean temperature with practically the same temperature of steam. 
 The reason is that in the latter case the cold air which leaks in 
 through the walls and around the window casing, besides keeping 
 the air immediately in contact with the radiator at a lowpr mean 
 temperature, causes a much more rapid circulation around the rad- 
 iator, with the result that it gives out more heat units per square 
 foot. It is for this reason, too, that one may put down for a posi- 
 tive and infallible rule in radiator design that the radiator which 
 has the most open space around its surfaces and the most inter- 
 rupted exposure to the surrounding air will give out the most heat 
 per square foot under the same conditions of setting. In compliance 
 with this rule, other things being equal, narrow radiators are more 
 effective than wide ones, and low ones than high ones; but the 
 effect of width and height can more than be offset by a slight in- 
 crease in the distance between the loops; for example, the author 
 found that a four-column 38-inch radiator gave out exactly the 
 same heat per square foot of measured surface as a two-column 
 38-inch radiator, because the former had a mean distance between 
 the loops about 16/100 of an inch greater than the latter; also a 
 
STEAM HEATING AND VENTILATION. 45 
 
 38-inch flue radiator was improved 7 per cent, in heating effect by 
 separating the loops % inch. 
 
 It is largely for this reason of freer circulation around the sur- 
 face that the ordinary wall coils of 1 or l^-inch wrought-iron 
 pipe, which are extensively used in factories, are much more ef- 
 fective than cast-iron radiators. Some careful tests by Prof. M. 
 E. Cooley of the University of Michigan showed that a single layer 
 coil of horizontal pipes gives out 40 per cent, more heat per square 
 foot than a two-column cast-iron radiator under the same condi- 
 tions of setting. 
 
 It may be further stated in compliance with the same rule that 
 the hot-water type of radiators is somewhat less effective than the 
 steam type on account of the obstruction offered by the loop con- 
 nection at the top, and also that flue radiators are less effective 
 than the ordinary open type. Just how much less effective the 
 flue types are depends upon the kind and design, but the wide low 
 flue radiators, not considering extension-surface types, are some- 
 times over 23 per cent, less effective than the ordinary two-column 
 radiators of the same height. It may also be stated that there is 
 a greater difference between the high and low radiators of the flue 
 type than of the open types. One make of two-column cast-iron 
 radiator proved 6^ per cent, more effective in the 20-inch height 
 than in the 38-inch, and another make nearly 10 per cent., while 
 an 8-inch wide flue radiator showed over 20 per cent, improvement 
 in the 20-inch over the 38-inch. 
 
 Condensation at different pressures. Mr. W. J. Baldwin made 
 some tests some years ago to determine the relative heating effect 
 of radiators under different steam pressures, with the same con- 
 ditions of setting. Taking the condensation at 1 pound steam 
 pressure as 100, he found the condensation at other pressures to 
 be represented by the following figures : 
 
 1 Ib. pressure 100 1 15 Ibs. pressure 126 
 
 5 Ibs. pressure 108 j 20 Ibs. pressure 134 
 
 10 Ibs. pressure 118 | 
 
 Extension-surface radiators. In regard to what is known as ex- 
 tension-surface radiators, they are generally made in the flue form, 
 and numerous tests show they are never as effective per square foot 
 of actual surface as are the radiators which have no extension sur- 
 face. Profs. Denton and Jacobus made some tests to illustrate 
 this point. They tested two forms of extension-surface flue ra- 
 
46 STEAM HEATING AND VENTILATION. 
 
 diators and then planed off the extensions and re-tested them. 
 They found that with one radiator, which had 43 per cent, more 
 surface in the first condition than in the second, gave only about 
 17 per cent, more heating effect. This, however, is not exactly a 
 fair comparison on the grounds of extension surface alone, as the 
 radiators had a much more effective proportioning of air-space 
 design with the extensions planed off. 
 
 Surface of radiators. There are other considerations which 
 alter the effectiveness of a radiator besides the design and setting, 
 notably the condition of the surface. Radiators are rarely used 
 with the natural iron surface, but are painted in all possible ways. 
 The nature of the surface has practically no effect on the con- 
 vected heat, but a very decided effect on the radiant heat; but as 
 the latter is generally less than 35 per cent, of the whole, the 
 effect on the total heat emitted is not so marked. Furthermore, 
 usually only the top and outside surface of one side is painted at 
 all. In general the dark and lustreless paints are the most effect- 
 ive, and may even improve the heating power, while the bright 
 shiny metallic paints may reduce the effect quite decidedly. 
 
 But few tests as to the effect of paints have been made. Prof. 
 Carpenter found that two coats of black asphaltum increased the 
 total heating effect by 6 per cent., two coats of white lead 9 per 
 cent., rough bronzing about 6 per cent., while a coat of glossy 
 white paint reduced it by 10 per cent., although the kind of ra- 
 diator considered is not mentioned. The author found that two 
 coats of ordinary "radiator japan paint" had but little, if any, 
 effect, but in one case, on a 38-inch flue radiator, three coats of 
 gold bronze reduced the heating power by over 12 per cent. This 
 loss was probably due partly to the reduction in radiant heat from 
 the polished surface and also to the fact that the convected heat 
 was somewhat reduced by the heavy coating of paint acting as a 
 non-conductor. This is doubtless sometimes the effect with old 
 radiators which have been painted several times. 
 
 Location of radiators. As before stated, the setting of the ra- 
 diator has a decided effect on its heat-giving power, and no two 
 conditions can be considered exactly alike in this regard. For di- 
 rect radiators, the best place to set them is unquestionably under 
 a window. The reason of this is that the greatest leaks of cool 
 air from outside are around the window frames and the greatest 
 loss of heat by radiation is from the glass. There is in conse- 
 
STEAM HEATING AND VENTILATION. 47 
 
 quence a decided downward current of cold air at the window 
 which, if the radiator is on the opposite side of the room, rushes 
 across the floor and is accelerated by the upward current of hot 
 air from the radiator. Such a condition tends very decidedly to 
 make cold currents along the floor. If the radiator be placed 
 under the window the cold drafts are interrupted and the heat 
 more diffused moreover, the upward current from the radiator, 
 the downward current from the window and the leakage drafts, 
 all combine to make a resultant draft of cold air against the side 
 of the radiator which lowers the temperature between the loops 
 and altogether tends to increase the effectiveness of the surfaces 
 very considerably over what would be found in still air. 
 
 Direct radiators are often put in recesses under windows and 
 low radiators are sometimes placed under window seats. Such 
 settings, while highly desirable from an aesthetic consideration, de- 
 cidedly change the effectiveness of the radiator both by shutting 
 off the radiant heat and by lessening the free convection. From 
 some rough experiments the author is led to believe that the or- 
 dinary marble top, which is often placed on radiators, will reduce 
 the heating effect from 6 to 15 per cent., depending on the size, 
 kind and height of the radiator; but this is not stated on the au- 
 thority of a careful comparative test. 
 
CHAPTER IV. INDIRECT RADIATORS. 
 
 The preceding chapter comprised mainly a discussion of the 
 principles involved in the action of radiators in giving out their 
 heat to the air and objects surrounding, but was confined almost 
 entirely to direct radiation. Many of. the deductions as to the 
 relative value of different kinds of surface may be applied to indi- 
 rect radiators as well, but a theoretical discussion of the latter re- 
 quires some entirely different considerations from those presented 
 in the last chapter on direct radiation. The indirect radiator is. 
 located below and outside of the room to be heated; it is enclosed 
 by a casing, which has an air connection to the outside of the 
 building, and a hot-air flue to the room to be heated. In this dis- 
 cussion it should be stated that the term indirect radiation is often 
 applied to radiators or heating coils which are used in connection 
 with a fan whjch creates a forced draft. In the author's opinion 
 this is a mistake, as the element of forced draft involves still other 
 considerations, and such radiators are merely heating coils for 
 mechanical ventilation and should be discussed separately as such. 
 The indirect radiator proper depends entirely upon the draft ac- 
 tion of the heated column of air above it for its ventilating effect,, 
 and also for a means of communicating its heat to the room above. 
 
 Theory of indirect radiator. The theory of the indirect radiator 
 may be illustrated by the accompanying Figure 26, in which R is 
 the radiator set in a box, B, and provided with a cold-air connec- 
 tion, C, to the outside air (generally having a damper, d), and a 
 hot-air duct, D, to the room to be heated, with a register, r, in the 
 floor or wall of the room. Steam is supplied to the radiator by 
 the pipe, p, through the casing. The heat of the radiator causes 
 a column of hot air to rise through D, and the current is main- 
 tained by the excess of pressure of the column of cold air outside 
 over that of the column of hot air in D. The exact pressure which 
 creates this current is found in the excess weight of a column of 
 cold air of height H over that of a column of the same height 
 and of the temperature of the air in D. 
 
 This may be calculated as follows, since the weight of a cubic 
 
STEAM HEATING AND VENTILATION. 49 
 
 4 
 
 foot of a gas of any temperature is inversely proportional to its. 
 absolute temperature, which is the temperature in degrees Fahren- 
 heit + 460, or W = c -h (t -f- 460), where W is the weight per cu- 
 "bie foot, t the temperature in degrees Fahrenheit, and c a constant, 
 different for each gas and which, for air, equals approximately 40.. 
 If t be the temperature of the cold air and T be that of the air in 
 D, then the pressure per square foot due to a column of cold air of 
 height H feet would be p = 40 H -r- (t + 460) and the pressure 
 
 Figure 26. Diagram of Indirect Apparatus. 
 
 due to a column of hot air of the same height would be P = 
 40 H -T- (T + 460). The difference of pressure which creates the 
 flow of air then is 
 
 40 H 40 H 40H(T t) 
 
 t + 460 T + 460 (t + 460) (T + 460) 
 The head, h, which creates the velocity of flow, is equal to the 
 height of a column of air of temperature T which would give the 
 pressure p, or 
 
 h = 
 
 H(T t) 
 
 40 t + 460 
 
 By the laws governing the flow of fluids the theoretical velocity 
 
50 STEAM HEATING AND VENTILATION. 
 
 with which the current of air would move through D is v = j/ 2gh 
 where h is, as above, the head producing the flow. This would be 
 the velocity produced in D by the difference in pressure p were it 
 not for the resistance to the flow caused by the friction of the air 
 in passing through the radiator and ducts and past dampers, regis- 
 ters, etc. This resistance often reduces the velocity to less than 
 half of the theoretical velocity. Mr. Alfred E. Wolff, however, 
 recommends that 50 per cent, of the theoretical velocity be taken 
 in the case of ventilating flues which depend on a heated column 
 for their action. 
 
 The practical application of this theory is, however, one of con- 
 siderable difficulty. In an indirect radiator in a given situation 
 we do not know the temperature of the heated column, and, what 
 is most important, we do not know the resistance of the air pas- 
 sages. What we do know is that we have a radiator of so many 
 square feet surface located in a certain system of boxing, ducts, 
 etc., and supplied with steam, or hot water, at a certain tempera- 
 ture. The temperature of the air outside being also known, or 
 assumed for extreme conditions, the question is how much air will 
 be delivered by this radiator to the room and also to what degree 
 it will be heated. 
 
 The amount of heat given off to the air depends upon the ve- 
 locity and upon the difference between the temperature of- the 
 steam in the radiator and the mean temperature of the air around 
 it; and the velocity depends, again, upon the difference of tem- 
 perature between the entering and out-going air as well as upon 
 the air resistance as embodied in the arrangement of ducts, struc- 
 ture of radiator, etc. All of these make a complicated system of 
 variables which it is impossible to apply in theoretical formulas and 
 anticipate what the actual result will be. In practice, a given ra- 
 diator in a given setting, and with given temperatures of steam and 
 outside air, condition of wind being constant, will deliver a definite 
 amount of air heated to a definite degree and the velocity and final 
 temperature adjust themselves until there is an equality between 
 the temperature head acquired and the velocity head plus the head 
 necessary to overcome the resistance. But exactly how this com- 
 bination will adjust itself it is wellnigh impossible to say before- 
 hand, inasmuch as the air resistance is a quantity very difficult tc 
 predetermine, it being very greatly affected by a slight change in 
 the arrangement. 
 
STEAM HEATING AND VENTILATION. 
 
 51 
 
 Mills' test of indirect radiators. For these reasons, all rules thus 
 far deduced for installing indirect radiators are entirely empirical. 
 But very few tests have been made upon indirect radiators with a 
 view to establishing the relation between any of the variables in- 
 volved; but SQme valuable results might be obtained by a thorough 
 series of experiments carefully and systematically carried out. Mr. 
 J. H. Mills, in his work on Heat, published in 1883, presents the 
 collected results of a number of tests on several indirect radiators 
 of different types. These tests were made on various radiators at 
 various times and by several different experimenters. 
 
 The writer has taken from the Mills table the results given for 
 the two radiators upon which the greater number of tests were 
 :made and has endeavored by plotting some diagrams from them to 
 determine something of the relationships between the existing 
 variables. The results published by Mr. Mills on the Gold pin 
 radiator and the Whittier radiator are presented in the accom- 
 
 TESTS ON GOLD'S PIN INDIRECT RADIATOR. 
 
 Tempera- Diff. Temp.^ % $ 
 
 tures. . . , a rt a t: OT 
 
 Experimenter. 
 
 C. B. Richards.... 1873-4 
 
 W. J. Baldwin.... 1875 
 
 W. Warner ....... 1880 
 
 Dr. Gray ......... 1875 
 
 C. B. Richards.... 1873-4 
 
 J. R. Reed ......... 1875 
 
 C. B. Richards.... 1873-4 
 
 J. H. Mills ........ 1876 
 
 W. J. Baldwin ____ 1885 
 
 J. H. Mills ........ 1876 
 
 W. J. Baldwin.... 1885 
 
 C. B. Richards.... 1873-4 
 
 J. H. Mills ........ 1876 
 
 J. H. Mills ........ 1876 
 
 J. H. Mills ........ 1876 
 
 J. H. Mills ........ 1876 
 
 4 
 
 j 
 
 1 ' 
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 bfi 
 
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 <u X 
 
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 1$ 
 
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 C 
 
 j 
 
 -(-> I 
 
 
 H 
 
 W 
 
 w 
 
 O 
 
 <5 
 
 PQ 
 
 
 215 
 
 
 
 160 
 
 160 
 
 215 
 
 5.44 
 
 111 
 
 340 
 
 60 
 
 239 
 
 71 
 
 168 
 
 97 
 
 168 
 
 3.83 
 
 128 
 
 239 
 
 70 
 
 222 
 
 42 
 
 145 
 
 103 
 
 180 
 
 4.60 
 
 145 
 
 288 
 
 90 
 
 259 
 
 33 
 
 125 
 
 92 
 
 226 
 
 6.54 
 
 231 
 
 400 
 
 
 215 
 
 
 
 139 
 
 139 
 
 215 
 
 9.15 
 
 214 
 
 572 
 
 58 
 
 222 
 
 52 
 
 127 
 
 75 
 
 170 
 
 7.92 
 
 343 
 
 495 
 
 
 215 
 
 
 
 129 
 
 129 
 
 215 
 
 12.65 
 
 319 
 
 791 
 
 76 
 
 239 
 
 81 
 
 159 
 
 78 
 
 158 
 
 8.49 
 
 354 
 
 531 
 
 60 
 
 227 
 
 82 
 
 150 
 
 68 
 
 145 
 
 8.16 
 
 290 
 
 510 
 
 76 
 
 239 
 
 90 
 
 158 
 
 67 
 
 148 
 
 8.91 
 
 433 
 
 557 
 
 60 
 
 227 
 
 70 
 
 137 
 
 67 
 
 158 
 
 8.93 
 
 433 
 
 558 
 
 
 215 
 
 
 
 121 
 
 121 
 
 215 
 
 15.92 
 
 428 
 
 995 
 
 77 
 
 230 
 
 88 
 
 158 
 
 70 
 
 142 
 
 10.04 
 
 467 
 
 628 
 
 76 
 
 259 
 
 90 
 
 166 
 
 76 
 
 169 
 
 15.16 
 
 649 
 
 948 
 
 76 
 
 222 
 
 90 
 
 145 
 
 55 
 
 132 
 
 12.54 
 
 741 
 
 784 
 
 77 
 
 227 
 
 94 
 
 145 
 
 51 
 
 133 
 
 13.43 
 
 855 
 
 839 
 
 TESTS ON G. WHITTIER'S INDIRECT RADIATOR. 
 
 C. B. Richards.... 1873-4 
 
 J. R. Reed 1875 
 
 . B. Richards.... 1873-4 
 
 J. R. Reed 1875 
 
 J. R.- Reed 1875 
 
 C. B. Richards.... 1873-4 
 
 ..215 135 135 215 
 
 68 222 45 129 84 177 
 
 ..215 102 102 215 
 
 68 222 52 110 58 170 
 
 .. 222 52 114 62 170 
 
 215 87 87 215 
 
 4.40 106 275 
 
 5.09 197 318 
 
 6.66 212 416 
 
 5.50 308 344 
 
 5.86 307 366 
 
 8.53 319 533 
 
 C. B. Richards.... 1873-4 215 77 77 215 10.14 428 634 
 
STEAM HEATING AND VENTILATION. 
 
 panying table. In the accompanying diagrams, Figures 27 and 
 28, the relation between the British thermal units given off per 
 hour per square foot of radiator and the cubic feet of air per square 
 foot of radiator per hour has been plotted from these results. 
 This last quantity is,, of course, a measure of velocity and is the 
 only one which is of practical value in the comparison of different 
 radiators.* The author has -marked each of the points on the 
 diagrams with the difference of temperature between the steam 
 and the entering air. At first inspection there seems to be but 
 little uniformity in the arrangement of points, but a little study 
 shows that for those representing the same difference of tempera- 
 ture the relation between the heat units per squa-re foot and the 
 cubic feet of air per square foot may be represented by a fairly 
 uniform curve. 
 
 . 
 
 DI200 
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 Approximate Eq 
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 r 
 
 ?y 
 
 "* cy 
 
 
 
 
 
 g. 
 400 
 
 
 \/ 
 
 ? ' 
 
 ^ 5? 
 
 ^ 
 
 
 
 
 
 -j tvv 
 _; 300 
 
 
 /, 
 
 r 
 
 
 
 
 
 
 
 10 200 
 
 / 
 
 ^ 
 
 
 
 ft 
 
 qyres at Points art Differences 
 "Ttmperature Between Steam 
 id Entering Air. 
 
 100 
 
 
 // 
 
 3 
 
 
 
 in 
 
 r 
 
 
 
 
 
 . s: AAir in Cub. Ft. per Hour per Sq. Ft. of Radiation . 
 
 Figure 27. Tests of Gold Pin Radiator. 
 
 On the diagram of the tests of the Gold pin radiator are plotted 
 the curves representing the relation for a difference of tempera- 
 ture of 215 degrees Fahr., and also approximately that for a 
 difference of 150 or 160 degrees. On the diagram for the Whit- 
 tier radiator are plotted only the curve for tests at a difference of 
 temperature of 215 degrees. There are some points, which are 
 marked by a cross on the diagram, that seem to be decidedly out 
 of place; that is, for the difference of temperature the ratio be- 
 tween the British thermal units per square foot and the cubic feet 
 of air per square foot is too low. Considering the fact, however, 
 
 * Mr. Mills gives a diagram somewhat similar to these, but tue au- 
 thor cannot find that the points given are taken directly from the tests 
 which he produces. 
 
STEAM HEATING AND VENTILATION. 
 
 53 
 
 that the tests under discussion were made on radiators of different 
 sizes, and several years apart, by different men, and under very dii ? - 
 ferent conditions of setting, the uniformity of the curves is very 
 striking, and the few points which are evidently out of place are 
 doubtless due either to some error of observation or in some 
 marked difference in the way of taking measurements. 
 
 Inasmuch as in practice we are most concerned with extreme 
 conditions, the curves for the difference of temperature of 215 de- 
 grees are of most value, as they may be taken to represent an 
 initial air temperature of degree and low-pressure steam at 215 
 degrees. It will be noticed that the 215-degree curve for the Gold 
 pin radiator is quite different from that for the Whittier. As these 
 curves show for a constant difference of temperature, the relation 
 between the cubic feet of air per square foot of radiator, which 
 is a measure of the velocity of air flow, and the heat given off per 
 
 1- I3UU 
 1200 
 ^ 1100 
 1000 
 
 Approx 
 
 mate Equation ofCurvz 
 y Difference of Temperat 
 
 M oga r 
 
 
 
 
 
 
 form 
 
 - H=m 
 
 jre 
 
 
 
 
 
 
 
 
 
 
 ft: 9 
 
 800 
 (0 TOO 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 | 
 
 ^- ' 
 
 
 
 
 fe cno 
 
 
 
 
 !P ^ 
 
 3^ 
 
 
 
 
 
 -500 
 H 400 
 <d 300 
 
 
 
 K) ^ 
 
 ^ 
 
 
 
 
 
 
 
 
 *^% 
 
 
 
 
 
 
 
 
 ^/^ 
 
 
 5 
 
 
 
 
 
 
 I ** 
 
 , ,00 
 
 / 
 
 r 
 
 5 
 
 c 
 
 
 figures 
 
 at Points areDiffei 
 erature between 
 teringAir 
 
 ences 
 Steam 
 
 / 
 
 
 
 
 
 iirTemp 
 
 
 / 
 
 
 
 
 
 
 "Q 100 20O 3OO 400 5OO &OO TOO 80O 90O 
 A- Air in Cub. Ft.per Hour per Sq. Ft .of Radiation. 
 
 THE ENGINEERING RECORD, 
 
 Figure 28. Tests of Whittier Indirect Radiator. 
 
 square foot, they take into consideration all variations in setting; 
 and the similar curves for any two radiators indicate precisely the 
 relative values of the two radiators. For example, the 215-degree 
 curve of the Gold pin radiator shows a uniformly higher ratio be- 
 tween the British thermal units per square foot and the cubic 
 feet of air per square foot than the similar curve of the Whittier. 
 The former is, by just so much, therefore, the more effective ra- 
 diator. Mr. Mills states of the Gold pin radiator, which was first 
 introduced by Mr. Samuel Gold in 1862, that it "has proved the 
 most efficient indirect-heating surface ever produced." It is still 
 extensively used, although some modern makes are largely sup- 
 planting it. It is to be regretted tests have not been made on some 
 of the more modern types in comparison with it. 
 
54 STEAM HEATING AND VENTILATION. 
 
 If it is desired to consider this question mathematically, the 
 equation of the 215-degree curve of the Gold pin radiator is ap- 
 proximately H = 8.28 A ' 79 , whereas the equation of the similar 
 curve of the Whittier radiator is H = 11.8 A k68 , in which H repre- 
 sents the British thermal units per square foot and A the cubic, 
 feet of air per square foot. In other words, with the Gold pin 
 radiator the heat is proportional to the 79/100 power of the num- 
 ber of cubic feet of air per square foot of radiation (nearly equal 
 to the fourth root of the cube), while with the Whittier it is pro- 
 portional to the 0.68 power (nearly the cube root of the square); 
 and the nearer this exponent approaches unity the more effective 
 will the radiator be, unless there is a large variation in the coeffi- 
 cient. 
 
 As yet there is not very much practical data on indirect radia- 
 tors. It would be of special value if some tests were made of the 
 more modern forms of indirects to establish corresponding dia- 
 grams for them. Such tests should be made preferably in cold 
 weather and with a constant difference of temperature between 
 the steam and entering air of about 215 or 220 degrees. The 
 setting of the radiator and air ducts should approximate practical 
 conditions and the velocity (as cubic feet of air per square foot of 
 radiator) could be varied by changing the resistance to air flow 
 by means of dampers. In this connection some experiments of 
 much practical value could also be made on the air resistance by 
 determining the velocity in cubic feet of air per square foot of 
 radiator attained for different temperatures in the hot-air duct, 
 D, in Figure 26. 
 
 Indirect radiators are seldom installed except for rooms on the 
 first or second floors; and in the former case the duct, D, is very 
 short, and in the latter it is usually from 12 to 16 feet long. It 
 should be stated in this connection that indirects of large size 
 should be spread out as much as possible so as to give a large area 
 against the current of air. If they are made of several radiators, 
 one above the other, as is sometimes the case, by the time the 
 air reaches the upper ones it is of so high a temperature that they 
 have but little effect in comparison with the lower section. 
 
 Direct-indirect radiators. In regard to direct-indirect radia- 
 tors, their action is much the same as that of the indirect; but 
 they have the added effect of radiation, whereas with the indirect 
 all heat is conveyed by convection. Furthermore, with the direct- 
 
STEAM HEATING AND VENTILATION. 53 
 
 indirect type, the flues are much shorter and the air resistance 
 much less than with the indirect setting. As a matter of fact, the 
 principal air resistance with the former is due to the passage of 
 the air through the radiator itself. 
 
 The author knows of no tests that have been made on direct- 
 indirect radiators, but considers they would be of value if they 
 should establish the relation between the heat given out and the 
 air delivery per square foot of radiator for constant differences of 
 temperature between the steam and entering air. As stated in a 
 previous chapter, in the opinion of the author the use of the direct- 
 indirect radiator, which has been, up to this time, and is now, very 
 limited, will be materially increased in the immediate future, as 
 in connection with exhaust fans they form an effective means of 
 introducing adequate ventilation into buildings which are not very 
 densely populated but in which there is a decided need of ventila- 
 tion. This class of buildings includes especially our palatial mod- 
 ern office buildings and also a certain class of factories. The more 
 extensive introduction of these radiators, as well as of the indi- 
 rects, is greatly delayed by the lack of accurate information as to 
 what the different makes on the market will do in the way of heat- 
 ing under various practical conditions of temperature and setting. 
 There seems, therefore, to be a considerable field for investiga- 
 tion in this regard. 
 
 Circulation in radiators. In the preceding chapter, and thus 
 far in this one, we have discussed the action of radiators in doing- 
 the work they are intended for, and have pointed out the theo- 
 retical and practical considerations involved. Before discussing 
 the bearing of these principles upon the design of a heating plant 
 it is necessary to turn the attention to another consideration in- 
 volved in the action of radiators, and one which is of much im- 
 portance in the practical efficiency of a heating plant. This is 
 the circulation of steam within the radiator. 
 
 Any one who has had even a slight experience with radiators 
 well knows the troubles that arise on .account of dripping air 
 valves, water-hammer, and the pocketing of air, and other evils 
 that are due to imperfect steam circulation. While evils of this, 
 kind are frequently attributable to imperfect circulation in the 
 piping, yet there is a great difference in the operation of radiators, 
 in this respect. 
 
 As shown in a previous chapter, any heating system contains a 
 
 UMIWCDQITV S 
 
56 STEAM HEATING A\'D VENTILATION. 
 
 considerable amount of air, and it is necessary to provide means 
 for venting the piping and radiators so as to allow it to escape in 
 the proper way. Ordinarily, when steam is shut off from a radiator 
 it fills with air at atmospheric pressure, through the air valve; 
 and when steam is turned on, this air must in some way be allowed 
 to escape before all of the surface can'have full heating effect. The 
 rapidity with which the air will be displaced by the steam depends 
 on where the air valve is placed and on the design of the radiator. 
 In some radiators the air will flow out the air valve and be fol- 
 
 Water Line formed by raising of 
 connection. 
 
 I 
 
 Steam Radiator. 
 
 I 
 
 Hot- Water Radiator. 
 
 Figure 29. A Cause of Retarded Air Expulsion. 
 
 lowed up by the steam rapidly and uniformly; while in others the 
 air will pocket in places, and it may be hours before it all works 
 out. The action of radiators in this regard is very peculiar, and 
 it is frequently exceedingly difficult to predict beforehand whether 
 or not a radiator will allow good circulation. 
 
 As a general thing the simplest radiators are the most ef- 
 fective. Air is heavier than steam of the same pressure, but in a 
 lieating system the air will always find its way to the dead end, 
 or point where there is no circulation. If a straight, vertical pipe, 
 closed at the top, be connected to a source of steam supply, any 
 air in the system will accumulate at its top. If steam is turned on 
 
STEAM HEATING AND VENTILATION. 57 
 
 an ordinary two-column steam radiator which is full of air and 
 has a tight air valve, after some moments the first few loops will 
 become filled with steam and perfectly hot, the remaining loops 
 being full of air and cold. If the radiator has a two-pipe connec- 
 tion the air may work out to some extent through the return; but 
 if it has only a one-pipe connection it will remain in this condi- 
 tion as long as the air valve is kept closed. If, however, the radia- 
 tor be of the hot-water type that is, it has its loops connected 
 by openings through the top as well as at the bottom the steam 
 will run along the top of the radiator, and as long as the air valve 
 is closed it will remain hot across the top and the lower part of 
 the loops will be cold, with the possible exception of the two end 
 ones. If now the air valves be opened, the air will flow uniformly 
 from the regular steam type, the steam filling one loop after an- 
 other; but with the hot-water type, as soon as the air valve is 
 opened the steam will flow first across the top, then across the 
 bottom, and the air will gradually work out, first from the loops 
 near the air valve. This will serve to illustrate to some extent the 
 action of air in radiators. 
 
 Circulation in direct radiators. As regards direct radiators, the 
 ordinary two-column steam type gives the most perfect circula- 
 tion. When steam is turned on it compresses the air to the press- 
 ure of the steam, and immediately fills a portion of the bottom 
 and the nearest loops to the inlet. Each loop then acts independ- 
 ently and the air syphons out of each, one after another, until 
 all are full of steam. In the hot-water type, as shown, the steam 
 has a free circulation around the radiator as a whole, which inter- 
 feres with the air circulation in each loop, so that these radiators 
 will often remain air bound in the center for a considerable length 
 of time. In the same way three and four-column radiators will 
 become air bound in the middle columns, the air syphoning out of 
 the two outside columns and establishing a circulation there, while 
 the contents of the inner columns remain quiet. In this connec- 
 tion it should be stated that a strictly one-column radiator would 
 not allow circulation at all, or but very slowly, but the so-called 
 one-column radiators are practically two columns, as they are cast 
 with a partition running up the loop with an opening at its top. 
 Radiators of the flue pattern always have one or two similar parti- 
 tions. Direct radiators which are low and wide are almost uni- 
 versally built with the loop opening in the top as well as the bot- 
 
58 STEAM HEATING AND VENTILATION. 
 
 torn, under the impression that otherwise the outside portions of 
 the loops would easily become air bound. Some of the author's 
 experiences, however, lead him to think that as far as this is con- 
 cerned the circulation in this type also is better without the top 
 connection. There is, however, one practical advantage which the 
 top-connection radiators have over the steam type, that is more 
 especially marked in long, low radiators. If, with a one-pipe con- 
 nection, the supply end is somewhat raised, on account of bad steam 
 fitting, the unwarranted expansion of a riser, or other cause, it 
 may trap the end loops of the steam type so as to shut off the air 
 valve entirely, whereas the top-connection type would have a cir- 
 culation in any such case, as is illustrated in Figure 29. Such a 
 
 Figure 30, Gold's Pin Radiator, 
 
 condition, though the result either of poor design or bad work- 
 manship, is still a frequent occurrence in practice. 
 
 Circulation in indirect radiators. Indirect radiators, which are 
 always made to lie horizontal, are usually made with loops equiva- 
 lent to the two-column form, but of greatly exaggerated width and 
 very low, and have the steam connection at one of the lower cor- 
 ners. There are, however, some special forms, and one has to use 
 his judgment as to their qualities in respect to circulation. 
 
 It is important that radiators be built and set so that but little, 
 if any, water will stand in them. The openings for pipe connec- 
 tions should be at the lowest point and the radktor should drain 
 perfectly. The loops of some radiators are built so that there is 
 quite a pocket under the opening. This should be avoided, as the 
 
STEAM HEATING AND VENTILATION. 59 
 
 water which stands in them, and is allowed to become cold, is a 
 fertile cause of water-hammer as well as dripping air valves. When 
 the steam is turned' into the cold radiator it is apt to gather up 
 this water, together with the freshly condensed water, and drive 
 it into the back end, clogging up the passages and causing water- 
 hammer and dripping air valves, to the great discomfort of those 
 in proximity. 
 
 Air valves. In regard to air valves there is but little to be said. 
 They are a necessity to every radiator; without them any radiator 
 would soon become dead by being filled with air. Automatic air 
 valves have almost entirely superseded the old-time hand air 
 valves. They are made with a composition disc, with a high coeffi- 
 cient of expansion, which is arranged to close the valve as soon 
 as the hot steam comes in contact with it. They are also pro- 
 vided with a screw attachment by which the valve opening can 
 be adjusted after the valves are in place. The disadvantage of 
 the automatic air valve is that when steam is turned on, the entire 
 radiator will become heated. For this reason the author prefers 
 the plain hand air valve on radiators in his own rooms, as the 
 amount of the radiator heated can be very accurately regulated 
 by means of them, especially when they are connected on a one- 
 pipe system. The automatic air valve, however, takes the circu- 
 lation in the radiator entirely out of the hands of persons who 
 are not acquainted with their principles, and in the case of indi- 
 rects is a necessity. 
 
 Air valves are generally placed about 18 inches from the bottom 
 of the last loop. Theoretically the best location would be near 
 the bottom of this loop, but if there is danger of much water in 
 the radiator they are safer near the top. The author has cured 
 several cases of a dripping air valve by tapping it into the extreme 
 top of the loop. When so placed the last loop will sometimes re- 
 main partially air bound on one side, hut otherwise they are quite 
 effective in this position. The trouble referred to, however, is 
 much more often due to improper piping than to anything in the 
 design of the radiator. 
 
CHAPTER V. DESIGN OF KADIATION. 
 
 Heat loss in buildings. There have been considered in previous 
 chapters the various kinds of radiators in use and the amount of 
 heat given off by them under different conditions; and the subject 
 now approaches a study of the particular way in which the heat is 
 utilized. The object of any heating system is, of course, to main- 
 tain a uniform temperature in the building in question, and to do 
 this it is necessary: First, to replace the heat lost by convection 
 and radiation from the windows and walls of the building to the 
 colder surroundings outside; second, to heat to the required tem- 
 perature any air that may be intentionally admitted for ventila- 
 tion; and third, to heat also the air that may be admitted unin- 
 tentionally through cracks of window frames and porous walls and 
 opening doors. The amount of heat required for this last cause 
 is much greater than is generally supposed. 
 
 The amount of air that will pass through the walls of an ap- 
 parently tight room is incredible to those who are not familiar 
 with it by actual experiment. The author knows of no experi- 
 mental data on the subject, but Dr. John S. Billings, in his valua- 
 ble work on "Ventilation and Heating," describes a simple and in- 
 teresting experiment that may be undertaken by any one. Take 
 a room of average proportions, heated by a hot-air furnace or in- 
 direct radiation, and the air will, on a fairly cold day, be coming 
 through the register with a very considerable velocity. If now 
 this velocity be measured by an anemometer, or other means, and 
 all doors and windows be closed and the measure be again taken, it 
 will generally be found that there is scarcely an appreciable reduc- 
 tion in this velocity. If now all the cracks of the doors and win- 
 dows be carefully stopped up with cloth or paper, the reduction in 
 the velocity of the incoming air will still be but very little reduced. 
 Some of the air in such cases escapes directly through the plastered 
 and papered walls, but more through floors and into the outside 
 air through brick walls, between the floors, and at such points as 
 are not plastered and papered. In cold weather it will generally 
 
STEAM HEATING AND VENTILATION. 61 
 
 be noticed that with all windows and doors closed, there is a de- 
 cided current of air flowing through any building, in the same di- 
 rection as the wind out of doors, and this is always most noticeable 
 at the floors. 
 
 It may be stated in general that brick buildings are much tighter 
 than wooden; and fireproof buildings which have wooden flooring 
 laid on some kind of a concrete filling are much tighter than the 
 ordinary brick buildings. It is perhaps a valuable thing that the 
 walls of buildings are not less porous than they are, for in far too 
 many cases there is no ventilation in winter, except what is ob- 
 tained in this way. It is, however, much better to make the walls 
 tight and provide some proper inlet for ventilation, especially as 
 from a sanitary standpoint the floor is the worst place to let cold 
 air into an otherwise warm room. An ordinary brick building can 
 be much improved in this respect, if, during construction, the walls 
 around the joists and for some inches above and below be painted 
 with a heavy coat of asphalt paint. It is for these reasons mainly 
 that all rules for proportioning radiation surface are very largely 
 empirical. 
 
 The heat required for a definite amount of ventilation can be 
 very accurately calculated. A cubic foot of ordinary air, at 60 or 
 TO degrees Fahr., weighs about 0.0745 pound, or there are 13.4 
 cubic feet per pound; and the specific heat is about 0.24, so 
 that one British thermal unit will heat 55.8 cubic feet of air 1 
 degree Fahr. This factor is, however, subject to considerable 
 variation according to the final temperature considered and the 
 degree of moisture, and is usually taken at 55. 
 
 The heat lost by radiation and convection from the walls of 
 buildings has been variously calculated by different authorities, 
 from Peclet down, and a great variety of results have been given. 
 It is unquestionably very difficult to determine it experimentally, 
 because of the fact that the loss of heat from walls, etc., depends 
 first upon the construction of the walls, but more especially upon 
 the condition of the air outside, the loss of heat being very greatly 
 increased by a slight wind blowing against the exposed surface. 
 The loss of heat is greatest from the glass surface of windows. 
 Mr. W. J. Baldwin, in his book on "Steam Heating for Buildings," 
 which has for some years been a standard, publishes a table of the 
 relative "heat-transmitting power of various building substances/* 
 which is given here. 
 
62 STEAM HEATINU AND VENTILATION. 
 
 BALDWIN'S TABLE OF HEAT-TRANSMITTING POWER OF BUILDING 
 
 SUBSTANCES. 
 
 Window glass 1,000 
 
 Hardwood sheathing on walls 66 to 100 
 
 White pine and pitch pine 80 to 100 
 
 Lath and plaster, good 75 to 100 
 
 common 100 to 150 
 
 Common brick, rough 150 
 
 hard finish 200 
 
 hollow walls, hard finish 150 
 
 Sheet iron 1,100 to 1,200 
 
 Mr. Baldwin further implies that the coefficient representing 
 the amount of heat given off by glass surface per square foot per 
 hour per degree difference in temperature between one side of the 
 glass and the other is about the same as the similar coefficient for 
 radiation, which may be taken at about 1.8 British thermal units. 
 
 The German Government made an investigation into this sub- 
 ject, and the results of its work have been translated into English 
 measures by Mr. Alfred E. Wolff (Journal Franklin Institute, Vol. 
 134); and Prof. R. C. Carpenter has translated the results of 
 Peclet's original investigations. The factors given differ very de- 
 cidedly, as may be seen by the accompanying table, in which are 
 given the coefficients of heat transmission for different surfaces : 
 
 TABLE OF COEFFICIENTS OF HEAT TRANSMISSION. 
 
 (British thermal units transmitted per hour per square foot of sur- 
 face per degree difference of temperature.) 
 
 Peclet. German Gov. 
 Baldwin. (Carpenter.) (Wolff.) 
 
 Single skylight .. 1.12 
 
 Double skylight .. 0.62 
 
 Single window 1.8 .91 to .98 1.03 
 
 Double window .60 to .66 .52 
 
 4-inch brick wall. ) ( .27 .43 .68' 
 
 S-inch brick wall. [ -{to .27 .46 
 
 13-inch brick wall. ) ( .36 .32 .32 
 
 17-inch brick wall .26 .24 
 
 Wooden beams planked over as flooring 0.083 
 
 Wooden beams planked over as ceiling 0.104 
 
 Fireproof construction as flooring 124 
 
 Fireproof construction as ceiling 145 
 
 Wooden door 414 
 
 Mr. John J. Hogan gives 1.57 British thermal units as the co- 
 efficient for glass. Mr. Charles Hood, the English authority, 
 states that one square foot of glass will cool 1.279 cubic feet of 
 air one degree per minute per degree difference in temperature. 
 This is equivalent to a coefficient of heat transmission of about 
 1.40 British thermal units per hour. Mr. Hood adds that this was 
 determined in still air and that it is very greatly increased by the 
 
STEAM HEATING AND VENTILATION. 63 
 
 effect of wind. He states, however, that it is well known that in 
 extremely cold weather there is invariably but little wind, so that 
 he considers this a safe coefficient to use. 
 
 Mr. Wolff has constructed a diagram of heat transmission from 
 buildings, which embodies the German coefficients with some slight 
 modifications based on his own very extended practice. He states 
 that he has used this diagram in the calculations of heating sur- 
 face for buildings, during the past six years, with the most satis- 
 factory results. This is a valuable recommendation, and the 
 author takes much satisfaction in presenting the diagram here- 
 with. 
 
 In using his diagram for proportioning radiation surface, Mr. 
 Wolff calculates by it the number of heat units lost from the ex- 
 posed wall and glass surfaces and further makes allowance for the 
 direction of winds on the outside exposure, as shown on the small 
 diagram on page 65 facing the main one. As indicated 5 to 25 
 per cent, is added to the calculated amount of heat dissipated in 
 transmission through the actual wall surface and 10 per cent, for 
 reheating the air constantly leaking in. An allowance is also ad- 
 vised, to the amount of 10 per cent., for the transmission of heat 
 through floors, ceilings, etc. Where the rooms are not large, one 
 calculation is made for all these factors by adding to the heat 
 transmission as obtained by means of the main diagram, the per- 
 centage given in the small circle. 
 
 For "wooden floors" in cheaply constructed buildings, the author 
 would recommend even more allowance than Mr. Wolff gives, since 
 where such floors are used a great loss of heat comes from a large 
 amount of cold air, which, even with a light wind blowing, will 
 work through the brick walls where the joists are set in and where 
 the walls are unsealed by lathing or plaster, and find its way into 
 the rooms. This is a common source of heat loss in cheaply con- 
 structed brick houses and apartment buildings, and is the usual 
 cause of the cold floors which are noticeable in many buildings in 
 cold weather. In fireproof structures, on the contrary, the con- 
 struction of the walls and floors is much more substantial and 
 offers but little opportunity for air to blow in between the floor 
 and ceiling. 
 
 Baldwin's rule for direct radiation. The wide variation in these 
 coefficients of heat transmission have led to a corresponding varia- 
 tion in the rules laid down for proportioning radiating surface. 
 
64 
 
 STEAM HEATING AND VENTILATION. 
 
 100 
 
 90 
 
 80 
 
 o 
 
 X 
 
 k 
 
 60 
 
 50 
 
 L 
 
 O- 
 
 30 
 
 
 
 10 20 30 40 50 60 7Q 80 50 JOO 
 Difference in Temperature. ( De9rees FahrenVieii.) 
 Alfred R. Wolff's Diagram of Transmission of Heat in Buildings. 
 
 A, vault light; E, single window; C, single skylight; D, 4-inch brick wall; 
 E, double window; F, double skylight; G, 8-inch brick wall; H, 1-inch pine 
 board door; I, 12-inch brick wall; J, concrete floor on earth; K, fireproof par- 
 tition; L, 2-inch pine board heavy door; M. 16-inch brick wall; N, 20-inch 
 brick wall; O, concrete floor on brick arch; P, 24-inch brick wall; Q, 28-inch 
 brick wall; R, 32-inch brick wall; S, wood floor on brick arch; T, 36-inch brick 
 wall; U, 40-inch brick wall; V, wood floor, double. 
 
STEAM HEATING AND VENTILATION. 
 
 65 
 
 25 
 25 10 
 
 10 
 
 25 
 10 15 
 
 In the early days of steam heating, radiating surface was generally 
 figured by various rule-of-thumb methods, based chiefly upon the 
 cubic contents of the room to be heated. These varied all the way 
 from one square foot of radiation for 30 cubic feet of space, up to 
 one square foot to 100 cubic feet, according to the building con- 
 sidered. Mr. Baldwin, in the earlier editions of the work men- 
 tioned, gives a rule which only takes into account the exposed sur- 
 face of the building. According to this rule it is first necessary 
 to figure what may be called the "glass equivalent surface/' This 
 is the actual glass surface in a room added to the wall surface re- 
 duced to its equivalent in glass. Mr. Baldwin refers to his table 
 of relative heat transmitting powers, previously given, and his rule 
 is as follows: 
 
 "In figuring wall surface, etc., multiply the superficial [exposed] 
 area of the wall in square feet by the number opposite to the sub- 
 stance in the table, and divide by 1,000 (the value of glass), the 
 product is the equivalent of so many square feet of glass in cooling 
 
 power, and may be added to the win- 
 dow surface." Mr. Baldwin then gives 
 a rule for finding the number of square 
 feet of radiating surface for each 
 square foot of glass, or the equivalent 
 of other building substances in glass, 
 which may be expressed by the follow- 
 ing formula : 
 
 K = (t ^-r-CT t)XE 
 where t is the required temperature- 
 of the room, ^is the temperature of 
 
 the outside air, T the temperature of steam in the radiator, R the 
 radiation surface, and E, the glass equivalent surface. 
 
 With an outside temperature of 5 degrees, an inside tempera- 
 ture of 70 and steam at temperature of 220, this formula would 
 allow \ square foot of radiating surface for each square foot of 
 glass or its equivalent. Mr. Baldwin further adds: {i lt must be-, 
 distinctly understood that [this] . '. . offsets only the .win- 
 dows and other cooling surfaces it is figured against and does not 
 provide for cold air admitted around loose windows, or [through 
 walls] of poorly constructed . . . houses. These latter con- 
 ditions, when they exist, must be provided for separately, and 
 usually require as much as 50 per cent, additional; a good com- 
 
 2? 10 
 
 Floor 
 or Roof. 
 10 
 10 6& 
 
 5 6A 
 
 10 15 
 
 10 15 
 
 5 (2C 
 
 Exposure Diagram. 
 
66 STEAM HEATING AND VENTILATION. 
 
 mon rule for ordinary purposes being three-fourths of a square 
 foot of heating surface to each square foot of glass, or its equiva- 
 lent." He further states that he has used this rule in preference 
 to any other for several years and found it very satisfactory. Fol- 
 lowing in Mr. Baldwin's footsteps, the writer has used this method 
 of calculating surface in the design of a large number of heating 
 systems, chiefly for large office buildings in Chicago and else- 
 where. He has found, however, for low-pressure systems in office 
 buildings that from 60 to 70 per cent, of the glass-equivalent sur- 
 face in figuring radiation gives ample and satisfactory results. 
 For such buildings he has counted each square foot of wall sur- 
 face as being equivalent to one-tenth of a square foot of glass. 
 For brick houses or apartment buildings of ordinary construction 
 it is better to take the wall surface as 15 or 20 per cent, of the 
 glass. For office buildings 65 per cent, of the glass-equivalent 
 surface in radiating surface is ample in most cases, and it may 
 average rather less. It should be greatest on the sides of the 
 building which are exposed to the severest winds in winter, and 
 .may be less on the southern exposures. 
 
 Mills' rule for direct radiation. Mr. Baldwin's method of calcu- 
 lating radiation surface calls for the exercise of careful judgment 
 on the part of engineers using his rule, and many authorities have 
 devised rules which are more specific. Most of these take into 
 raccount the glass surface, the wall surface, and also the cubic con- 
 tents of the room. The rule recommended by Mr. Mills in his 
 work is 
 
 E = 0.50 G + 0.05 W + 0.005 C 
 
 in which E is the number of square feet of radiating surface; G, 
 the square feet of glass surface; W, the square feet of wall sur- 
 face (exclusive of windows); and C, the contents in cubic feet. 
 This rule is recommended where the rooms are to be heated to a 
 temperature of 70 degrees with an outside temperature of 10 to 
 15 degrees Fahr. If the outside temperature is less or great- 
 er, the result should be multiplied by the proportionate fac- 
 tor. This is a very good rule and perfectly safe. The writer 
 knows of a contractor who has had a very wide experience in 
 steam heating who uses this rule universally, except that he mul- 
 tiplies the cubic contents by 0.004. 
 
 Willetfs rule for direct radiation. Mr. Jas. E. Willett, an archi- 
 tect of wide experience, who has given much study to heating 
 
STEAM HEATING AND VENTILATION. 67 
 
 and ventilation, formulated, several years ago, a very valuable rule 
 for proportioning direct radiation, which is expressed by the fol- 
 lowing formula : 
 
 R o.9 (t tj (0.60 G + 0.10 W + 0.0025 C) FJ -M 
 where F is a factor depending on the method of heating (0.8 for 
 low-pressure steam) and J, a factor depending on the exposure, 
 which Mr. Willetts puts as 1.0 for ordinary south and east ex- 
 posures and 1.4 for north and west. The other letters in the 
 formula have the same reference as in the formulas previously 
 given, but Mr. Willett states that t should be taken 10 degrees 
 higher than the lowest recorded temperature of the locality in 
 question. With t t taken at minus 8 degrees; t, 70 degrees; F, 0.8; 
 and J, 1, Mr. Willett's formula becomes : 
 
 E = 0.48 G + 0.08 W + 0.002 C. 
 
 This equation compares very closely with Mills, though less al- 
 lowance is made for the cubic contents and more for the wall sur- 
 face. The writer considers that if J, in Mr. Willett's formula, be 
 taken as 1. for south and east exposures, it is sufficient in most 
 cases to take it as 1.2 for north exposures. For such exposures, 
 therefore, the same formula can be used as for south and east 
 rooms and the radiation increased one-fifth. 
 
 Carpenter's rule for direct radiation. Prof. Carpenter, in his 
 work on heating and ventilation, has devised a formula which is 
 very carefully derived. He first calculates the amount of heat 
 lost from the room in question and then the amount of radiating 
 surface necessary to offset this heat, using coefficients for heat 
 transmission which he substitutes in his formula. According to 
 Prof. Carpenter's method, the heat in British thermal units lost 
 from a room for every degree difference in temperature between 
 the inside and outside air is h = nC -f- 55 + G + (W-i-4),in which 
 G, C, and W represent the quantities previously assigned them, and 
 n is the number of times the air of the room is to be changed per 
 hour. Prof. Carpenter states that for direct radiation it is neces- 
 sary to take n = 2 for ground-floor rooms and n = 1 for others, 
 to allow for leakage of air. The quantity, nC -=- 55 gives the num- 
 ber of heat units necessary to raise nC cubic feet of air 1 degree 
 in temperature. Prof. Carpenter states that the radiating sur- 
 fact should be equal to R = [ (t tj * (T t) a ] h in which 
 t is the required temperature of the room, t the outside tem- 
 perature, T the temperature of the steam in the radiator, and a 
 
68 STEAM HEATING AND VENTILATION. 
 
 is a coefficient of heat transmission from a radiator which varies 
 from 1.7 for low-pressure steam heating to 1.9 for steam pressure 
 of 40 pounds and 2.4 for steam pressure of 100 pounds. Taking 
 the usual conditions of t = 70 degrees and t t = 10 degrees and 
 with low-pressure steam heating, the factor, (t t a ) -=- (T t) a 
 becomes 0.324, so that with n = I the equation for radiation sur- 
 face becomes: 
 
 R 0.324 G + 0.08 W + 0.006 C. 
 
 This formula differs very considerably, in the factors used, from 
 those already cited, and it will be seen that it is based upon the 
 coefficient of heat transmission for glass of 1 British thermal 
 unit per square foot per degree difference in temperature, and the 
 radiation surface due to^the glass area is consequently much less 
 than in the other formulas. The difference is more than made up, 
 however, by the larger allowance for the cubic contents. In the 
 opinion of the author, Prof. Carpenter's coefficient for glass is con- 
 siderably too small, and his equation gives results which are too 
 large for rooms having large cubic contents with comparatively 
 small window surface, and results which are too small when the 
 proportions are reversed. 
 
 Monroe's rule for direct radiation. The author has recently de- 
 duced a formula which is a combination of Willett's and Carpen- 
 ter's, and is as follows: 
 
 R = (1.3 G + 0.25 W + 0.008 C) J (t t x ) -4- (T t) a. 
 In this the letters stand for the quantities previously assigned, J 
 being a coefficient depending upon the exposure (being unity in 
 ordinary cases) and for the usual conditions as assumed in previous- 
 cases, this formula becomes 
 
 R = 0.42 G + 0.08 W + 0.0026 C. 
 
 In the following table are given the proportions of four repre- 
 sentative rooms of an office building for which the writer was en- 
 Radiation Surface by 
 
 S T3 
 
 d 1 I I I I 11 
 
 Q, n-rcrn z2 a "- r: *-> 
 
 o & 
 8 H 
 
 1. West ,.., 
 
 2. N. & W.. 118 
 3 N 1 ^ & E. 
 
 4. NE. 
 
 u 
 
 W 
 
 u 
 
 a 
 
 g 
 
 d 
 
 S_j 
 
 
 3 
 
 * m 
 
 
 
 
 s 
 
 p 
 
 Q 
 
 
 
 
 PH ~ 
 
 59 
 
 160 
 
 3360 
 
 54.5 
 
 47 
 
 51 
 
 44 
 
 49 
 
 46 
 
 .18 
 
 312 
 
 2150 
 
 85 
 
 86 
 
 76 
 
 81 
 
 97 
 
 84 
 
 8.5 
 
 420 
 
 4070 
 
 85 
 
 84 
 
 87 
 
 82 
 
 85 
 
 80 
 
 59 
 
 129 
 
 1730 
 
 44.5 
 
 42.5 
 
 40 
 
 46 
 
 47 
 
 40 
 
STEAM HEATING AND VENTILATION. 69 
 
 gaged to design the heating system, and for which the heating 
 surface has been figured out according to Mills', Willett's, Carpen- 
 ter's and the author's formulas, and also according to Mr. Bald- 
 win's formula taking 65 per cent, of the glass equivalent surface. 
 
 The table also gives the amount of surface which was installed in 
 .each of the four rooms, and which has given perfect satisfaction 
 throughout two or three severe winters. The radiator used was 
 the two-column cast-iron radiator, 32 inches high, except in room 
 2, which had a 26-inch flue radiator. The radiation in room 2 was 
 made slightly less than the amount calculated, because a large por- 
 tion of the wall surface was a 25-inch brick wall, for which tho 
 multiplier for W might be taken about 0.15 instead of 0.25. 
 
 It might be stated that in using the formula given, i l is to be 
 taken 10 degrees above the lowest recorded temperature, and the 
 factor, J, should be taken from 1.05 to 1.15 for severe exposures, 
 and may also be increased 0.1 for ordinary brick buildings with 
 wooden floor joists, and 0.2 for wooden buildings. The factor a is 
 to be taken at 1.7 for ordinary conditions of exhaust-steam heat- 
 ing. It may be increased somewhat for heating at higher press- 
 ures and for buildings with low-pressure heating and no power, in 
 which steam pressure of 10 or 15 pounds may be carried, it may be 
 made equal to 1.8. In such cases, also, the temperature, T, may 
 T^e taken at 235 degrees. The factor a should be decreased where 
 the radiators are of an unfavorable pattern or are unfavorably lo- 
 cated, according to their relative heat-giving power, under such 
 conditions as has been pointed out in Chapter III. The last part 
 of the formula need be calculated but once for each building. The 
 factor a may be taken as high as 2.8 in some greenhouses and in 
 some factories in which wrought-iron pipe coils are used, which 
 are quite an effective type of surface. Unless the coils are espe- 
 cially favorably located, however, the factor should be somewhat 
 less than 2.8. 
 
 In the general application of the formula given above it will be 
 noted that the expression (t t x ) (1.3 G + 0.25 W + 0.008 C) rep- 
 resents the total heat given off by the room, and it is equal to 
 K (T t) a, which is the heat given off by the radiation surface. 
 
 Mr. Wolff in his practice calculates the heat lost per hour from 
 each room according to his diagrams previously given, with the 
 allowance for exposure as shown thereon. He then (divides this 
 amount by the number of British thermal units given off per 
 
70 STEAM HEATING AND VENTILATION. 
 
 square foot of radiator per hour, which he takes as 250 for a two- 
 column radiator (bronzed) set under the window, but this factor 
 varies within wide limits, as before described, according to the 
 kind of surface used and the nature of the setting. 
 
 Indirect radiation. With indirect radiation the heat lost from 
 the glass and wall surface must be made up by the heated air com- 
 ing in from the indirect radiator, and to accomplish this the en- 
 tering air must, in cold weather, have a temperature considerably 
 above the mean temperature desired in the room. The total heat 
 lost by the room is (t t t )' h where h is the expression (1.3 G-f- 
 0.25 W + 0.008 C) and the volume of air required in cubic feet per 
 hour is V= (t 1 1 ) h X 58 -=- (T t) where T is the temperature 
 of the air leaving the radiator. Now it is necessary for the in- 
 direct radiator to heat all of this air from the outside temperature 
 to the temperature T, and the total heat required to be given off 
 by the radiator is 
 
 U = V(T ^^58 = ^ tOCT yh-r-CT t). 
 
 It will be seen that both U and V vary rapidly with a change in 
 T, decreasing as T is increased. If t 70 degrees and tj = 10 
 degrees for extreme conditions, and if T = 150, V will be one-half 
 and U two-thirds of what they would be if T were taken at 110. 
 It is this fact that makes the indirect radiator quite a flexible de- 
 vice, for in extreme weather it is possible, by partially shutting off 
 the air supply, to maintain easily the required inside temperature 
 at the sacrifice of a small amount of ventilation. If T = 120, 
 U=:20Sh, and V = 93h; and with T 130, U = 18G h, and 
 V = 77 h. As a rule, it is safe to assume from 450 to 500 British 
 thermal units per hour per square foot of surface for an indirect 
 radiator, as will be seen by reference to the tests as described in 
 the last chapter, and taking the former figure, with T = 120, E = 
 0.46 h, and with T = 130, E = 0.415 h. 
 
 Inasmuch as it has been found that for the same conditions of 
 inside and outside temperatures E for direct radiation = 0.325 h, 
 it will be seen that according to this calculation from 28 to 40 per 
 cent, more heating surface is required for indirect heating than 
 for direct. The author has in his practice used these proportions 
 for indirect radiators, usually installing about 30 per cent, more 
 than for direct; although in some cases, where an exceptional de- 
 gree of ventilation is desired and the room has a comparatively 
 
STEAM HEATING AND VENTILATION. 71 
 
 large amount of glass surface, more radiating surface is neces- 
 sary. In such cases, and especially where a large amount of ven- 
 tilation is desired, it is necessary to see that the quantity V, tis 
 obtained above, is equal to the amount of air required for ven- 
 tilation. It will be found sufficient in all ordinary cases to change 
 the air four times per hour, which is generally satisfactory for 
 private houses; but where much entertaining is to be allowed for, 
 six times per hour is better. In designing indirect radiators it is 
 necessary to be very careful in the proportion of flues, but such 
 details of construction will be considered in the next chapter. 
 
 In proportioning direct-indirect radiators the same rules apply 
 as for the indirect type, although their action as direct radiators 
 may be counted on to some extent. Where this kind of radiator 
 is used in connection with an exhaust ventilating system very good 
 results are obtained by using the author's formula for direct ra- 
 diators, with an addition to the 0.008 C of 2/3 K -f- 55, where 
 K is the cubic feet of air per hour required for ventilation. This 
 gives additional surface necessary to heat 2/3 K cubic feet of air 
 from the outside temperature to that of the room. The author 
 figures on 2/3 K (in some cases f ), as in extreme weather the de- 
 gree of ventilation may be somewhat reduced. For these ra- 
 diators also, the factor a in the formula may be taken as 1.9 or 2. 
 
CHAPTER VI. PIPING AND CONSTRUCTION DETAILS. 
 
 Having selected the system of heating to be employed accord- 
 ing to the needs of the building in hand, and having proportioned 
 the radiator surface according to the requirements of the various 
 rooms, it then remains to lay out the system of piping and arrange 
 the various details of construction. 
 
 In regard to piping connections, it should be stated at the out- 
 set that the flow of steam through any system of piping depends 
 primarily upon the difference in pressure between that at the sup- 
 ply end and that at the delivery or return end, and without any 
 difference of pressure no flow of steam can exist. In exhaust heat- 
 ing or low-pressure gravity systems, this difference of pressure is 
 very slight, and consequently for such systems the pipes have to be 
 larger than for high-pressure heating or vacuum systems in which 
 the pressure in the returns is reduced by connecting them to a 
 vacuum pump. Again, in most systems of steam heating there is 
 another consideration which affects the sizes of pipes ; that is, 
 the water of condensation from the radiators. If the steam cir- 
 culation were uniform and continuous and the water of condensa- 
 tion kept separate from the steam supply, as in properly arranged 
 two-pipe systems, the pipes might be very small; but it is neces- 
 sary to allow for sudden opening of radiator valves, so as to take 
 care of the momentary demand for steam which this causes, as 
 well as the rush of water of condensation which accompanies it. 
 For exhaust and low-pressure gravity systems, it may be laid down 
 as a general rule that pipe sizes should be larger for the 'simple 
 one-pipe system than for any other arrangement. They may be 
 smaller for the one-pipe overhead, or Mills system, and still smaller 
 for the two-pipe systems. A description of various systems of 
 steam distribution was given in Chapter II. 
 
 Baldwin's rule for pipe sizes. In the early days of steam heat- 
 ing, pipe sizes were proportioned by various empirical rules, the 
 usual basis of which was the principle of being sure to get the 
 pipes large enough; and such rules are, to a large extent, blindly 
 followed to-day. Mr. William J. Baldwin, in his earlier work on 
 
STEAM HEATING AND VENTILATION. 73 
 
 steam heating, gave a rule for proportioning steam pipes which is 
 very convenient and has been very widely used. This rule states 
 that in the sectional area of the pipe there should be allowed the 
 area of a 1-inch pipe for every 100 square feet of radiator surface. 
 Inasmuch as the areas of circles are proportional to the square of 
 their diameters, this means a 1-inch pipe for 100 square feet, 2- 
 inch pipe for 400 square feet, 3-inch pipe for 900 square feet, 8- 
 inch pipe for 6,400 square feet, etc. These sizes are none too 
 large for many cases, although in plants with the system care- 
 fully arranged so that the circulation is all in one direction and 
 the water of condensation does not have to flow back against the 
 current of steam, pipes can be very considerably decreased below 
 the sizes given by this rule. Mr. Baldwin also gives a diagram of 
 minimum sizes for short horizontal supply mains from which few 
 branches are taken, which give sizes very much smaller than the 
 rule above quoted. [See Table I.] 
 
 Mills' rule for pipe sizes. Mr. J. H. Mills gives a diagram for 
 the sizes of mains for one-pipe overhead system? of which he is the 
 originator. This diagram gives sizes somewhat smaller than those 
 obtained by Mr. Baldwin's rule. In the accompanying table are 
 given the maximum square feet of radiation on pipes of each size 
 according to the rules of Baldwin and Mills, as well as Mr. Bald- 
 win's sizes for return pipes. In regard to his figures for minimum 
 sizes for mains, Mr. Baldwin states that they represent minimum 
 conditions for lengths of 50 feet or thereabout, but that for large 
 buildings one size larger should be used. 
 
 Monroe's rule for pipe sizes. In his own practice the author has 
 divided mains and risers of steam-heating systems into the follow- 
 ing classifications: 
 
 (a) Supply mains for one-pipe systems, which carry all water of 
 condensation, but in the direction that the steam flows. 
 
 TABLE I. PIPE SIZES FOR STEAM HEATING ACCORDING TO BALD- 
 WIN AND MILLS. SQUARE FEET OF HEATING SURFACE. 
 
 Size of pipe in inches.. 1 23 45 6 8 10 
 
 A. Mills Supply mains 
 
 and risers ....;...... ... 900 1,750 2,500 3,300 4,000 7,250 10,500 
 
 B. Baldwin Supply 
 
 mains and risers..,.. 100 400 9001,600 2,5003,600 6,40010,000 
 C. Baldwin Minimum 
 
 for mains 1.700 3,000 5,500 8,700 16,000 22,000 
 
 D. Baldwin Returns 1,650 3,700 6,200 10,000 
 
 (b) Mains for two-pipe or one-pipe overhead systems, into which 
 there is no water of condensation from the radiators. 
 
74 
 
 STEA:J HEATING AND VENTILATION. 
 
 (c) Supply risers for ordinary one-pipe systems which carry all 
 the water of condensation and in a direction opposite to the flow 
 of steam. 
 
 (d) Risers for one-pipe overhead systems which carry all the 
 water of condensation but in the same direction as the flow of 
 steam, the lowest part of riser below last radiator being solely a 
 return pipe. 
 
 (e) Supply risers for two-pipe systems which carry no water 
 condensation,, except that due to the pipes themselves. 
 
 In addition to these the following classification is made for re- 
 turn pipes : 
 
 (f) Return mains for two-pipe and overhead systems which are 
 above the water-line of the system. 
 
 (g) Horizontal return mains for two and one-pipe systems which 
 are below the water-line. 
 
 (h) Return risers for two-pipe systems. 
 
 Table II. herewith gives the maximum amount of radiation to 
 be put on each size* of pip'e for the different classifications: 
 
 TABLE II. PIPE SIZEb FOR HEATING SYSTEMS (MONROE). 
 
 
 (a) 
 
 (b) 
 
 (c) 
 
 (d) 
 
 (e) 
 
 (f) 
 
 (g) 
 
 (h) 
 
 fl 
 
 
 So 
 
 2" 
 
 ? i 
 
 of 
 
 02 i 
 
 of -1 
 
 F 
 
 
 9 
 
 .2 
 
 9 
 
 ^ 
 
 I 
 
 _d ^ 
 
 C3 c? 
 
 Lri 
 
 9 
 
 1 
 
 M 
 Ctf OJ 
 ^ ft 
 
 IP.-' 
 
 03 . 
 
 3J. 
 
 PH a> 
 
 .2 w 
 
 
 
 1| 
 
 II 
 
 gS, 
 
 ft 
 
 
 ft _S 
 
 
 ft 
 
 ft 
 
 V 
 
 
 H 
 
 4-1 
 
 !>> a 
 
 > o *" 
 
 *f 
 
 
 >> o 
 
 S aJ 
 
 do - 
 
 gd> 
 
 O 
 
 "a 
 
 "a ^ > 
 
 ! 
 
 gJl 
 
 "ft ^ 
 
 ^ o 
 
 i* ~* m 
 
 d^ 
 
 O> 
 
 (Q 
 
 ftQ 
 
 ftHO 
 
 
 
 ' 
 
 ^-> <J ^3 
 
 -> PQ S 
 
 S^- 1 
 
 ''I. 
 
 W 
 
 d 
 
 a 
 
 02 
 
 03 
 
 n 
 
 K 
 
 M 
 
 S 
 
 1 
 
 70 
 
 .... 
 
 50 
 
 60 
 
 80 
 
 400 
 
 400 
 
 250 
 
 
 150 
 
 
 120 
 
 150 
 
 200 
 
 900 
 
 900 
 
 700 
 
 2 
 
 300 
 
 *400 
 
 250 
 
 300 
 
 400 
 
 1,600 
 
 1,600 
 
 1,200 
 
 2^2 
 
 500 
 
 650 
 
 400 
 
 500 
 
 700 
 
 2,600 
 
 3,500 
 
 2,000 
 
 3 
 
 750 
 
 1,200 
 
 700 
 
 900 
 
 1,200 
 
 3,800 
 
 8,000 
 
 3,000 
 
 4 
 
 1,400 
 
 2,000 
 
 1,500 
 
 1,800 
 
 2,000 
 
 7,000 
 
 14,000 
 
 . . . . 
 
 5 
 
 2,400 
 
 3,500 
 
 2,500 
 
 2,600 
 
 3,600 
 
 12,000 
 
 26,000 
 
 
 6 
 
 4,000 
 
 5,500 
 
 3,600 
 
 4,200 
 
 .... 
 
 16,000 
 
 .... 
 
 .... 
 
 7 
 
 5,500 
 
 8,000 
 
 
 
 
 30,000 
 
 
 
 g 
 
 7*000 
 
 12*000 
 
 
 
 
 
 
 
 10 
 
 12*000 
 
 16,000 
 
 
 
 
 
 
 
 12 
 
 18.000 
 
 25^000 
 
 
 
 
 
 
 
 The table here given represents the conditions which are to be 
 met with in ordinary buildings, and exceptional conditions will 
 have to be met with by the judgment of the engineer conducting 
 the work. It will be noted in general that this table gives less 
 
STEAM HEATING AND VENTILATION. 7 
 
 radiation on the small pipe sizes and more on the large than that 
 by either Baldwin's or Mills' rules. In small plants, or in plants, 
 where a large number of small radiators are supplied from the 
 risers, the number of radiators on a given riser may affect its size 
 irrespective of the amount of radiation. Eisers less than 1 inch 
 in size are rarely used on a two-pipe system, or less than 1J on *n 
 ordinary one-pipe system, unless perhaps for only one small ra- 
 diator. In an overhead system the height of the building and the 
 consequent number of radiators on the riser affect the size, espe- 
 cially at the lower end. In such a system it must be borne in 
 mind that all the water of condensation from the higher radiators 
 is falling down the pipe, passing the connections to the lower ra- 
 diators. For such systems in high office buildings it is therefore 
 well to make the risers fairly large toward the bottom while the 
 upper portion can be proportioned according to the sizes given in 
 column (d). For buildings about ten stories high, the lower part 
 of the riser should be not less than 2 inches, and if the amount of' 
 radiation on the riser is large or the building is over 15 stories 
 high, this may better be 2^ inches. The table given is intended 
 for low-pressure gravity systems and exhaust heating where not 
 more than 2 or 3 pounds back pressure can be carried on the- 
 engine. 
 
 For high-pressure systems working at 20 or 30 pounds pressure,, 
 such as are used sometimes in factories, when engines are used 
 with a condenser, the pipe sizes may be somewhat smaller than 
 those given in columns (e) and (h), although for the smaller 
 connections it is not advisable to reduce them on account of the 
 possibility of water from the radiators backing into the supply 
 pipes. 
 
 Pipes for vacuum systems. In vacuum systems in which the 
 vacuum is maintained on the return side, pipe connections may be- 
 reduced very materially, and Table III, given herewith, shows 
 sizes recommended by Messrs. Warren Webster & Company for 
 mains, risers and radiator connections for the vacuum systems 
 which they install. As already described, their system is in prin- 
 ciple an ordinary two-pipe system with a vacuum pump on the re- 
 turns, but also having the special feature, of an automatic thermo- 
 static valve on the return connection, which valve closes auto- 
 matically when it is heated to steam temperature and opens when 
 it becomes cooler. From the author's experience he would 
 
76 STEAM HEATING AND VENTILATION. 
 
 sider the sizes given in this table somewhat too small and would 
 in general recommend about one pipe size larger. 
 
 TABLE III. PIPE SIZES WEBSTER VACUUM SYSTEM.. 
 
 Sizes of supply 
 
 pipes, in % 1 iy 2 2 3 4 5 6 8 10 
 
 Maximum sq. ft. on 
 runs not over 
 50 ft 100 150 400 900 2,000 4,000 8,000 12,000 30,000 60,000 
 
 Sq. ft. surf, for long 
 
 runs, 300 to 400 ft. 40 100 300 600 1,500 3,000 6,000 10,000 22.000 40,000 
 
 Minimum for re- 
 turn for above, 
 in % % V 2 % 1 1% l x /4 1% 2 2% 
 
 With vacuum systems which have a vacuum only on the air-valve 
 connection, such as the Paul system, it is impracticable to reduce 
 much the sizes of the steam pipes below those given in Table II, 
 as the only feature of this system is that it keeps pipe and ra- 
 diators perfectly free from air, and does not greatly affect the 
 flow of steam and water of condensation. 
 
 Radiator connections. The connections from the risers to the 
 radiators are always made somewhat larger in proportion than the 
 mains and risers, and Table IV gives sizes which represent good 
 practice for low-pressure systems. 
 
 TABLE IV. RADIATOR CONNECTIONS. 
 
 One-pipe Systems. Two-Pipe Systems. 
 
 r 
 
 Max. surf. 
 
 ' 
 
 
 Max. surf. 
 
 
 in rad. 
 
 Supply. 
 
 Returns. 
 
 in rad. 
 
 in. 
 
 sq. ft. 
 
 in. 
 
 in. 
 
 sq. ft. 
 
 % 
 
 25 
 
 % 
 
 K 
 
 40 
 
 1 
 
 50 
 
 1 
 
 % 
 
 75 
 
 1% 
 
 85 
 
 1% 
 
 l 
 
 120 
 
 1% 
 
 130 
 
 1% 
 
 l 
 
 180 
 
 Carpenter and Sickles' rule for steam pipe sizes. In designing 
 piping for large systems it must be borne in mind that there are 
 many things which affect the flow of steam in a piping system, and 
 special cases must have special consideration. Elbows, bends and 
 valves greatly increase friction in the pipes. According to the 
 recent investigation of Professor Carpenter and Mr. E. C. Sickles, 
 as given in a paper before the American Society of Mechanical 
 Engineers, Volume XX, a single 90-degree elbow is equal in 
 frictional resistance to a length of pipe equal to about 520 
 times the diameter, while the resistance of a globe valve is equal 
 to a length of 706 times the diameter, and a good gate valve 
 
STEAM HEATING AND VENTILATION. 77 
 
 does not add any practical resistance. They gave the following 
 approximate formula for diameters of pipes, which they say is 
 practically accurate for sizes over 2J inches: 
 
 d = 0.184 y w* L H- pD 
 
 in which d equals the diameter in inches ; w, the weight of steam, 
 to be delivered in pounds per minute; L, the length of the pipe in 
 feet; D, the density or weight in pounds per cubic foot, and p, the 
 difference in pressure in pounds per square inch between the ends 
 of the pipe. Transposed, this formula becomes : 
 
 w= V pDd 6 -5- 0.00021 L. 
 
 From this it will be seen that, other things being equal, the de- 
 livery is proportional to the square root of the fifth power of the 
 diameter. 
 
 The accompanying table, Table Y, is calculated from this for- 
 mula, assuming p = 1 pound per square inch difference of pressure 
 and D = 0.04, which is the density of steam at a pressure of about 
 one pound above the atmosphere. In this table allowance is made 
 also for two globe valves and two elbows to each length of pipe. 
 The square feet of surface each pipe would supply, allowing 0.30 
 pound of steam per square foot per hour (0.005 pound per minute), 
 which is very liberal for direct radiation, is also given in the table. 
 This table is chiefly interesting when compared with Table II> 
 but may be of value for long mains where the building to be 
 heated is at a distance from the plant. It should be noticed, how- 
 ever, that the greatest resistance is due to the elbows and valves. 
 For example, the 8-inch pipe, 600 feet long, with two elbows and 
 
 TABLE V. CAPACITIES OF STEAM PIPES. 
 
 w wt. of steam delivered per min. per 1 Ib. difference of pressure. 
 R = sq. ft. of radiation supplied at 0.005 Ib. per sq. ft. per min. 
 
 Diameter, Length of pipe allowing for 2 valves and 2 elbows, 
 
 in. feet. 
 
 3 w 
 
 3 R 
 
 4 w 
 4 R 
 6 w 
 6 R 
 8 w 
 8 R 
 
 10 w 
 
 10 R 
 
 12 w 
 
 12 R 
 
 
 ) 200 
 
 400 
 
 600 
 
 1,000 
 
 8.1 
 
 > 7.7 
 
 6.9 
 
 6.3 
 
 5.5 
 
 ,70< 
 
 ) 1,540 
 
 1,380 
 
 1,22 
 
 1,100 
 
 15.( 
 
 ) 14.2 
 
 12.9 
 
 12. 
 
 lO.b' 
 
 00( 
 
 ) 2,840 
 
 2,580 
 
 2,400 
 
 2,120 
 
 
 33. 
 
 31. 
 
 29. 
 
 26.2 
 
 
 6,600 
 
 6,200 
 
 5,800 
 
 5,240 
 
 
 59.5 
 
 56.5 
 
 54. 
 
 49. 
 
 
 11,900 
 
 11,300 
 
 10,800 
 
 9,800 
 
 
 95. 
 
 90.4 
 
 87. 
 
 81. 
 
 
 19,000 
 
 18.080 
 
 17,400 
 
 16,200 
 
 
 138. 
 
 132. 
 
 128. 
 
 120. 
 
 
 27,600 
 
 26,400 
 
 25,600 
 
 24,000 
 
78 STEAM HEATING AND VENTILATION. 
 
 two valves is equivalent to 2,240 feet of straight pipe, and the 
 -addition of another elbow would be equivalent to 350 feet 
 of straight pipe and would reduce the delivery in the ratio of 
 V2,240 -f- 2,590. 
 
 Draining pipes. In laying out the piping system for a heating 
 plant, besides the proper size of pipes there are two points which 
 must 'be very carefully considered : (1) That pipes as well as radia- 
 tors are properly drained so that the water of condensation will 
 flow off easily and uniformly to its proper receptacle; and (2) that 
 proper provision be made for the expansion of pipes, so that such 
 expansion shall not interfere with the flow of steam or water or 
 disturb the setting of the radiators. 
 
 Pipes for an ordinary one-pipe system, which are run around 
 the basement of a building, should be pitched toward the extreme 
 ends, from which the return connection should be taken and run 
 back to the receiver below the water-line. If the mains are very 
 long they should be drained at intervals into this pipe. 
 
 In a two-pipe system in which the mains are similarly run, they 
 should be drained into the return pipes, and in making these 
 drip connections care should be taken that the return pipes into 
 which they drain are lower than the supply mains, so that there 
 will be no opportunity for water to flow from the returns into 
 the supply mains. The return pipes are generally, where possi- 
 ble, run under the basement floor, and should be lower than the 
 supplies. Figures 31 and 32 represent typical connections from 
 mains to risers. Where, on account of economy of space, it is 
 necessary to run the supply and return mains on nearly the same 
 level, as in Figure 32, the supply main must be dripped into a 
 separate pipe run back under the floor or along the wall and con- 
 nected into the principal return main below the water-line of 
 the system. In two-pipe systems where the supply mains are 
 short and properly covered, so that there is not much condensa- 
 tion, they may be given a slight rise from the boiler or source 
 of supply and the water of condensation allowed to flow back. 
 Riser connections should be taken out of the top of the mains so 
 as to prevent any water of condensation that may be in the mains 
 from getting into the risers. 
 
 In the one-pipe overhead system there is always a main supply 
 riser running to the branch mains in the attic, and this should have 
 a drain pipe from its lowest point extending back to the receiving 
 
ISTEAM HEATING AND VENTILATION. 19 
 
 tank. The attic mains are drained directly into the supply risers, 
 which drop from the bottom of them. 
 
 In connecting up radiators on a one-pipe system they should be 
 set so as to pitch slightly toward the connection from the riser, 
 and the connection should always pitch toward the riser. Con- 
 nections which, on account of carelessness in workmanship, were 
 pitched in the opposite way, are a very fertile cause of water- 
 hammer. Eadiators set on two-pipe systems should be pitched 
 slightly toward the return connection, which should not be con- 
 nected from the same end as the supply. There are a number of 
 plants in which radiators connected on two-pipe systems have 
 both the supply and return connections at the same end of the 
 radiator, but in the opinion of the author this is a very bad prac- 
 tice, as the radiator might very much better be connected on the 
 one-pipe system. In fact, when radiators with such connections 
 are in operation, unless the return connection is lower than the 
 supply, which is not generally the case, the water of condensation 
 is just as apt to Tun down the supply connection as down the re- 
 turn. Furthermore, when such radiators are turned on, if the sup- 
 ply valve is opened first, any water which may be in the radiator 
 runs out of this connection, as well as the large amount that 
 is formed by the first contact of steam with the cold radiator; 
 and if the return valve is opened first, the water in the return 
 pipe backs up into the radiator, so that when the supply valve 
 is opened, a large amount of it will run out to the supply connec- 
 tion. At this point it should be stated that in turning on radia- 
 tors with two-pipe connections the supply valve should always 
 be opened first; and the fact that the uninformed occupants of 
 rooms frequently do not know which is the supply valve is one 
 of the objections of two-pipe systems. 
 
 Expansion of pipes. The expansion of pipes is an important 
 consideration in any case, and where there are long mains or in 
 high office buildings, which consequently have long vertical risers, 
 it becomes a consideration of vital importance. The coefficient 
 of expansion of wrought-iron pipe is 0.000007 per degree Fahr. 
 This amounts to about 1.5 inches in a 100-foot length for 
 low-pressure steam pipes. In horizontal mains this can be gen- 
 erally taken care of by making turns or offsets in the mains in 
 every 50 or 75 feet of pipe, the expansion being taken up by the 
 spring of the pipe. All connections from mains or risers should 
 
80 
 
 STEAM HEATING AND VENTILATION. 
 
 be made with sufficient length of horizontal connection to allow for 
 this expansion. In Figures 31 and 32 the expansion of the 
 mains and risers is taken up in the spring of the arms, AB. An 
 old rule for the length of such expansion arms is that the length 
 in feet should be equal to twice the diameter in inches. This, 
 is a fair rule in most cases, but much depends on the amount of 
 expansion to be taken care of, and no set rule can be given. 
 
 The most serious difficulties on account of expansion are met 
 with in the long vertical risers of the modern high office buildings. 
 In such cases any considerable movement of the riser is apt to re- 
 sult in trouble, as the radiator connections are generally short. 
 
 Pipe 
 
 Elevation. p |O 32 Section. 
 
 Provisions for Drainage and Expansion of Piping. 
 
 Various means are employed to overcome this. In buildings over 
 ten stories in height it can generally be taken care of by anchor- 
 ing the risers rigidly in the middle so they expand in both direc- 
 tions, and allowing for the expansion, by the connections to the 
 supply main in the attic and to the returns in the basement. The 
 radiators on the upper and lower floors, where most of the ex- 
 pansion takes place, must have connections sufficiently long to 
 allow for it, and they must have sufficient pitch, so that they will 
 not be trapped by the expansion of the risers. The author is fa- 
 miliar with one building 14 stories high in which expansion is en- 
 tirely? tak^-iir care of in this way. Radiators on the extreme floors 
 
STEAM HEATING AND VENTILATION. 
 
 81 
 
 Radiator. 
 
 are made with extra high legs, and the connection from riser is- 
 as shown in Figure 33. In another case, in a 14-story building,, 
 an offset was made in each riser over the windows of the seventh 
 floor, the upper part running on the opposite side of the tier of 
 windows from the lower part, the spring of the pipe in this offset- 
 taking care of the expansion at this, point. The risers were an- 
 chored rigidly in the center of each section. Arrangements of 
 this kind are frequently used, and the chief objection is that un- 
 less they are concealed the offsets make an unsightly appearance, 
 and it is frequently very inconvenient to put them in on account 
 of the arrangement of the building. 
 
 In one large 16-story building with which the author is ac- 
 quainted, a loop, as indicated in Fig- 
 ure 34, was made with each riser and 
 sealed in the seventh floor; but he 
 would not recommend this arrange- 
 ment, inasmuch as leaks are most apt 
 to occur at the points marked C when 
 the expansion and contraction works 
 on the threads of the joint. Besides 
 this, the framing of the building and 
 extra construction details in the floor 
 necessary to conceal these offsets are 
 difficult and expensive. The expansion 
 of such risers is frequently taken care 
 of by means of expansion joints, a dia- 
 gram of which is shown in Figure 35. 
 The author has used these joints to 
 
 a large extent, and although in some localities there is a prejudice 
 against them, he thinks this rather unwarranted. By proper ar- 
 rangement the expansion risers in any building not over 12 or 
 14 stories high .can be taken care of with one set of expansion 
 joints. In a 14-story building heated on the overhead system 
 the author installed an expansion joint in each riser above the 
 radiator connection at the seventh floor. The risers were an- 
 chored rigidly to the beams of the fifth and twelfth floors so 
 that expansion was in both directions from these points. This 
 gave about f inch expansion downward at the first and eighth 
 floors and about f inch upward at the seventh and fourteenth. Ead- 
 iator connections on the eighth floor were long enough to admit of 
 
82 
 
 STEAM HEATING AND VENTILATION. 
 
STEAM HBZfING AND VENTILATION. 83 
 
 this expansion, and on the first floor they were connected as in 
 Figure 33. If the radiator connections were very short, two joints 
 would have been put on each of these risers. 
 
 In laying out large systems, valves should be placed on each 
 riser so that each one can be shut off independently of the others 
 in case of leaks or in case of repairs or changes to be made on 
 any of the radiators. Gate valves should be used preferably on 
 account of the fact that they interpose infinitely less resistance 
 to the flow of steam or water than do globe valves. Furthermore, 
 in such cases provision should be made for changes in the arrange- 
 ment of rooms and consequent changes in the location of radiators. 
 It is a very good practice to put tees on each riser at each floor 
 whether or not, in the first instance, a radiator connection is re- 
 quired, as subsequent changes in the arrangement of rooms may 
 make it desirable to change the radiators. 
 
 Figure 36 shows the arrangement of piping in the attic of the 
 Ellicott Square, a large 10-story building in Buffalo, N. Y., which 
 is heated by direct radiation on the overhead system. The figure 
 illustrates the method of connecting the overhead mains to the 
 risers, and also the way in which expansion of the mains is pro- 
 Tided for by bends and offsets. In this instance the piping was 
 rigidly anchored at four points marked D, and the expansion al- 
 lowed in all directions from these four points. It may be noted 
 here that branch mains were taken off at points marked E and F, 
 instead of connecting each riser to the main 10-inch pipe at these 
 points. This was done for the purpose of saving the expense and 
 'the delay to the work of connecting each riser into the 10-inch 
 pipe. 
 
 Valves. Much care should be used in placing valves on a piping 
 system. Gate valves should always be used on mains. If globe 
 valves are used anywhere, the stems must be placed horizontally, 
 as otherwise they form a water pocket. Thermostatic valves, so- 
 called, are often used on radiators, being connected with an auto- 
 matic device which opens the valve when the temperature falls, 
 -and closes when it rises. 
 
 Location of risers. In laying out the floor plans for the heating 
 system of a large office building it is a mistake to try to reduce 
 the number of risers to a minimum. It is much better to put in 
 risers enough so that a radiator can be placed under any window 
 in the building without too long a connection from the riser, for 
 
84 
 
 STEAM HEATING AND TENTTLATION. 
 
 in such buildings one can never know what changes in the arrange- 
 ment of rooms or in the location of radiators may ultimately be 
 desired. Figure 37 shows the t} r pical floor plan of the heating 
 diagrams for a fourteen-story building in Chicago, showing the 
 location of risers and radiators. This building is exceptional on 
 account of the large number of bay windows and large amount of 
 "glass surface. Furthermore, the risers were all concealed in the 
 columns in the manner shown in Figures 38 and 39, the building 
 being framed with Gray columns, built as indicated. An expan- 
 
 Figure 37. Plan Showing Location of Risers and Radiators. 
 
 sion joint was placed on each riser, above the radiator connection 
 at the eighth floor, with flange unions above and below the joint. 
 At these joints a removable wooden panel was placed over each 
 riser, as indicated at Figure 38, but otherwise they were enclosed 
 by the wire-lath and plaster forming the ordinary finish of the 
 columns. Figure 39 shows a section of the column at the four- 
 teenth floor. The radiator connections were exposed above the 
 floor and run about as indicated on the floor plan. This building 
 is heated on the one-pipe overhead system. It contains 11,000 
 square feet of radiation, supplied by an 8-inch main to the attic. 
 The typical floor has 1,055 square feet of glass surface, 
 
STEAM HEATING AND VENTILATION. 
 
 85 
 
 square feet of wall surface and 47,400 cubic feet of space, includ- 
 ing corridors, and is heated by 18 radiators containing 787 square 
 feet of surface. By the author's formula given on page 68 the 
 amount of surface required amounts to 730 square feet> but the 
 exposure of the upper stories of this building is unusually severe. 
 It is frequently a very difficult matter to conceal risers in fire- 
 proof buildings on account of the floor plates of the columns and 
 the beams, which frequently interfere with placing the risers very 
 close to them. Figure 40, however, represents the manner in 
 which they were enclosed in a building which was framed with 
 ~box columns.. In this case the tile fireproofing was put on over 
 both column and riser. In concealing risers in the walls of wooden 
 buildings it is necessary to protect the pipes carefully from imme- 
 diate contact with the woodwork. In hanging risers in buildings 
 
 Fio.38 
 
 FiG.39 FiG.4O 
 
 Methods of Running Risers in Columns. 
 
 great care must be taken that the pipe be cut to the proper lengths 
 so that the fittings for the radiator connections will come exactly 
 in the proper place. 
 
 Riser anchors. As previously stated, risers are usually, espe- 
 cially in large buildings, anchored rigidly at certain points so that 
 expansion shall be in both directions from these points. This 
 should be carefully done so that the pipe will not slip, and the 
 method to be employed to accomplish this depends largely upon 
 the local conditions. Figures 41 and 42 show two methods of ac- 
 complishing this, the latter being especially adaptable where the 
 riser can be run close to the floor beam, but to make it perfectly 
 rigid it should be made strong and shrunk in place. The method 
 indicated by Figure 41 can be adapted to anchoring the pipe to 
 a column instead of to the floor beams. In some cases risers are 
 also secured at the other floors so as to allow expansion, but at 
 
86 
 
 STEAM HEATING AND VENTILATION. 
 
 the same time maintain proper alignment ; but this is not generally 
 necessary, as the rigidity of the piping and connections is gener- 
 ally sufficient to keap the pipes property in line. 
 
 Protecting pipes. Where risers or other pipes run through the 
 floors or walls they are generally protected by floor sleeves with 
 floor and ceiling plates. These are usually made of galvanized 
 iron in a telescopic form so as to fit any thickness of floor. In 
 buildings with wooden floors they are necessary so as to give an 
 air space around the pipe and prevent immediate contact of the 
 steam pipe with the woodwork. In fireproof buildings they ara 
 
 FiG.4t 
 
 Types of Riser Anchors. 
 
 frequently omitted, but it is preferable to use them, as they make 
 a better finish around the pipe at the ceiling and prevent the ex- 
 pansion of the pipe from disturbing the flooring or plaster. Floor 
 and ceiling plates should be used in any case. 
 
 Eadiator connections are frequently encased in the floor, but 
 it is generally difficult to accomplish this in fireproof buildings, 
 as the space between the floor level and the top of the iron beams 
 is not generally sufficient to box in the connections and make 
 proper allowance for the vertical movement of these connections 
 due to riser expansion. It can be done in some cases, however, 
 but the connections should always be enclosed in a galvanized-iron 
 box and the flooring should be so laid that a strip over the pipes 
 can be easily removed. 
 
 Supporting pipes. Horizontal pipes are almost invariably sup- 
 
STEAM HEATING AND VENTILATION. 
 
 87 
 
 ported from the ceiling above by means of some kind of an expan- 
 sion hanger, two common types of which are shown in Figures 
 43 and 44, the two shown in each case being, one for wooden beams 
 and the other for iron. The rods can be cut to the length desired 
 after the pipe is in place. There is sufficient movement of the rod 
 at the top to allow for the small play of the pipe due to expan- 
 sion. A simple and cheap form of hanger frequently used for 
 small pipes in buildings with wooden floors is made of a piece of 
 light chain looped under the pipe and hung from the nails in the 
 floor beams. The chain can be cut to length with wire nippers. 
 In case of very large pipes in the basement of buildings, they are 
 
 FiG.43a. Fio.43b 
 
 Ti 
 
 Expansion Pipe Hangers. 
 
 sometimes supported by some kind of a standard erected from 
 the floor. 
 
 Arrangement of pipes. In laying out the main piping connec- 
 tions of the power plant of a large building great care must be 
 taken to arrange the pipes as systematically as possible so that 
 they take up no more room than necessary, and also to properly 
 provide for the drainage of all pipes into proper receptacles. This- 
 is frequently a difficult matter, but one can hardly give too much 
 consideration to the subject, as the successful operation of a plant 
 depends largely upon the way piping connections are arranged. 
 It is impossible to give any detailed rules, as each plant is a prob- 
 
88 
 
 STEAM HEATING AND VENTILATION. 
 
STEAM HEATING AND VENTILATION. 
 
 89 
 
 lem in itself, and is entirely subject to local conditions. The main, 
 connections to the heating system must be laid out in connection 
 with the exhaust and live-steam pipes of the power plant, accord- 
 ing to the principles established in Chapter II. Simplicity in n 
 piping system is always primarily desirable, but sufficient valves 
 and by-passes should be installed, so that if any accident occurs 
 to one part of the system that part can be shut off without crip- 
 pling more than a small section. 
 
 Figure 45 shows the arrangement of the main piping connec- 
 tions in a large office building in Syracuse, N. Y., in which, on 
 account of the extreme difference in floor levels and the crowded 
 condition of the machinery, a really systematic arrangement of 
 piping it was impossible to obtain. (The Engineering Record of 
 November 5, 1898.) The main valves controlling the heating sys- 
 
 Fis.44a. 
 
 tern are indicated at A, B, C and D. During the heating season 
 the valve, D, is opened and the back-pressure and reducing-press- 
 ure valves put into service, while during the summer months the 
 valve, D, is closed entirely, shutting off the heating mains, and 
 the 10-inch back-pressure valve is opened wide. Ordinarily, both 
 in winter and summer, the valve, A, is closed, so that all exhaust 
 steam from the pumps and engines goes through the muffler tank 
 and heater; but in case it is necessary to' open these for cleaning, 
 the valves B and C are closed and the valve, A, opened, so that 
 the exhaust steam may go directly either into the free exhaust 
 or the heating system, as the case may be. The building in ques- 
 tion contains about 15,000 square feet of radiators and is heated 
 on a two-pipe system with basement mains. The returns come 
 back to the two automatic governors which control the 6x4x6-' 
 
90 STEAM HEATING AND VENTILATION. 
 
 inch pumps. These deliver the return water through the closed 
 heater into the boilers. There are three pumps used for this pur- 
 pose, and so connected that any one can be used on the governors 
 separately or together, and any one can be used to pump cold 
 water through the heater. The feed pipe has a by-pass around 
 the heater, to be used when the heater is being cleaned. 
 
 Eeturn pipes should be given as much pitch as possible except 
 where they are below the water-line of the system. In running 
 these below basement floors they should be put in trenches, prefer- 
 ably of brick or concrete, and with movable covers. If there is 
 danger of water underground the trenches must be arranged so 
 that they can be kept dry, and no better trench can be made than 
 one of good concrete. 
 
 Pipe coverings. All the piping connections should, as far as. 
 possible, be covered with some kind of non-conducting pipe cov- 
 ering, of which there are innumerable varieties made. In some 
 cases risers and other pipes are left uncovered so as to utilize the- 
 heating effect, but the disadvantage of this is that heat is given 
 out from such pipes whether it is wanted or not, and it is much 
 better practice to cover the risers and depend on the radiators, 
 for heating. One of the greatest sources of fuel waste is found 
 in uncovered mains in basements of buildings where heat is noth- 
 ing but an inconvenience, and in order to dispel it in moderate 
 weather windows are opened, which greatly increase the wasteful 
 condensation. A good pipe covering will save from 65 to 80 per 
 cent, of the heat which would ordinarily be wasted from the pipes. 
 Coverings of which 85 per cent, is carbonate of magnesia, certain 
 molded forms of pure asbestos fiber, and molded forms of mineral 
 wool are the best kinds of protection for steam pipes to reduce 
 condensation. Some coverings which show very good results when 
 new, deteriorate rapidly, due to the charring effect of the pipes and 
 to disintegration. 
 
 Pipes and flues for indirect radiators. "We come now to the con- 
 sideration of certain details of construction which are especially 
 requisite in indirect heating. In this class of steam heating the 
 piping connections are subject to much the same rules for run- 
 ning pipes as those for direct radiators, but indirects are almost 
 invariably located in the basement of buildings and the pipes run- 
 ning to them are horizontal. Furthermore, the condensation per 
 square foot of indirect radiator is from 25 to 50 per cent, more 
 
STEAM HEATING AND VENTILATION. 
 
 91 
 
 than that per square foot of direct radiatpr, so that the piping 
 connections are generally made about a size larger, and, except 
 in rare cases, connected on two-pipe systems. Indirect radiators 
 are usually hung from the beams of the first floor, and various 
 methods, which are dependent upon the local conditions, are 
 adopted for supporting them. A frequent form of support is in- 
 dicated in Figure 46, the radiator resting on short pieces of pipe 
 which are hung by rods bolted to the floor joists, or hung from a 
 pipe over them. Indirect radiators are always encased in some 
 kind of a metal box, either of galvanized iron or tin, or of wood 
 lined with tin. These boxes connect directly with the hot-air 
 flues which run to the rooms above and which are of heavy tin 
 or sheet iron. Both the flues and boxes should, of course, be as 
 nearly air tight as possible. In regard to sizes of hot-air flues, an 
 
 
 loor L ire i / Pipz doorf 1 
 
 
 
 WrJoists- 
 
 1 1 
 
 
 c 
 
 
 Fadiator. 
 
 
 \ 
 
 /'Floor Line. 
 
 % 
 
 j) : ( 
 Joists. 
 
 n 
 
 
 
 
 
 Radiator. 
 
 
 Pipe about 2." / 
 
 Figure 46. Indirect Radiator Support. 
 
 10 
 
 1.2 
 
 15 
 1.0 
 
 20 
 
 0.85 
 
 25 
 0.75 
 
 old rule gives 1 square inch of flue area to 1 square foot of radia- 
 tor. This is very satisfactory in most cases, but the following 
 table, which gives the sizes recommended by Prof. J. H. Kinealy, 
 is to be preferred, as the size of flue should depend upon its height : 
 
 SIZES OF FLUES FOR INDIRECT RADIATORS. 
 
 Height in feet from center of radiator to 
 
 center of register 5 
 
 Sq. in. of flue area for 1 sq. ft. radiation 1.7 
 
 The indirect-radiator boxes must, of course, have a fresh-air 
 inlet. This should always be run from the outside and from a lo- 
 cation removed from the possibility of contamination to the in- 
 coming air; and it is preferable that the cold-air inlet be located 
 at least a few feet above the ground. Cold-air supply connections 
 from the outside to indirect boxes should be made as short as pos- 
 sible; 1 square inch area per 1 square foot is generally sufficient, 
 
STEAM HEATING AND VENTILATION. 
 
 although if the flues a:ce of considerable length or are winding, a 
 larger ratio should be given. If a number of radiators receive 
 air from the same cold-air flue, the flue may be somewhat smaller. 
 In buildings in which there are a considerable number of indirect 
 
 radiators there are two 
 general methods of con- 
 necting the fresh-air 
 flues, which are illus- 
 trated in Figures 47 and 
 48. Figure 47 represents 
 the cellar plan of a large 
 Massachusetts residence 
 (The Engineering Bec- 
 ord, August 5, 1893; Mr. 
 A. A. Sanborn, Boston, 
 heating contractor), in 
 which there are seven 
 large clusters of indirect 
 radiators which supply 
 about 30 hot-air flues ris- 
 ing to the rooms above, 
 the hot-air pipes run- 
 ning horizontally from 
 the radiator boxes, in 
 some cases for 50 feet, 
 to the vertical flues. 
 radiators in this 
 are all Gold's 
 Pin in 16-foot sections.) 
 In the Philadelphia resi- 
 dence shown in Figure 
 48 (The Engineering 
 Eecord, December 15, 
 1894), there is, on the 
 contrary, a long main 
 cold-air duct which sup- 
 plies a large number of 
 
 indirect radiators, one for each of the vertical flues, the radiator 
 in all cases being located directly under the vertical flues. In 
 the opinion of the author this is much the preferable method, 
 
 (The 
 
 building 
 
STEAM HEATING* AND VENTILATION. 
 
 93 
 
 as a much more positive circulation of air to the separate rooms 
 can be secured than by the other method. 
 
 The system shown in Figure 48 is interesting also on account cf 
 the construction of the main cold-air duct and the connections 
 from it to the radiator boxes. These are well illustrated in Figure 
 49, the main duct, it will be noted, being of brick, and underground. 
 In the author's opinion there is one particular in which the system 
 shown in Figure 48 might have been much improved. The colcl- 
 air duct is long and winding, and had it been more uniform in size 
 
 Figure 48. The Indirect System in a Philadelphia Residence. 
 
 and supplied with another cold-air connection on the side of 
 house opposite the existing one, it would have insured a more posi- 
 tive circulation to all the radiators. The reason of this is that 
 in cases, such as shown in Figure 48, where there is only one cold- 
 air connection for a number of radiators, when there is a strong 
 wind blowing against the side of the house opposite the fresh-air 
 inlet it is sometimes very difficult to get a good draft in the flues, 
 especially in those most removed from the cold-air inlet, as the 
 force of the wind (which, with the best constructed houses, blows 
 through the walls to a great extent), seriously opposes the current 
 
94 STEAM HEATING AND VENTILATION. 
 
 of air in the ducts. If there are two fresh-air connections, each 
 provided with dampers, the one on the leeward side of the build- 
 ing can be closed and the one on the windward side opened to give 
 a proper amount of cold air. It is, moreover, desirable to put a 
 tight damper in the duct to each radiator. 
 
 Setting direct-indirect radiators. In regard to the setting of di- 
 rect-indirect radiators, the piping connections are made according 
 to precisely the same rule as for directs, although in cases of large 
 radiators of this kind it may be desirable to increase slightly the 
 pipe sizes on account of the somewhat increased condensation. A 
 
 Plan 
 
 first floor Register, 
 
 Indirect 
 Radiator: 
 
 Elevation. 
 
 Cellar Floor. 
 
 Brick 
 Duct. 
 
 F.G.49 
 
 THE ENGINEERING RECORD. 
 
 frequent form of fresh-air connection for this kind of radiator is 
 indicated in Figure 50, and the connection to the outside air should 
 in all cases be provided with an easily adjusted damper. One 
 trouble with direct-indirect radiators is that when a strong wind 
 is blowing against the outside wall it is difficult to prevent objec- 
 tionable drafts, due to sudden gusts of wind, which, in cold weath- 
 er, will make frequent cold waves across a room notwithstanding 
 the average temperature may be about right. Figure 51 represents 
 a special form of setting for large radiators of this kind adopted 
 % Mr. Alfred E. Wolff, in the Singer Building, New York City. 
 (The Engineering Record, September 3, 1898.) It will be seen 
 that the effect mentioned is here avoided by making the cold-air 
 
STEAM HEATING AND VENTILATION. 
 
 95 
 
 Iiilet to the radiator somewhat tortuous, so that, as far as possible, 
 the draft is due only to the hot air from the radiator. The same 
 effect is accomplished in the United States Government method 
 
 Inlet Damper. 
 
 ~~ -___ 
 
 "TMS ENOINECRINO RECORD. 
 
 Figure 50. A Direct-Indirect Radiator. 
 
 Fie. 51 
 Types of Direct-Indirect Radiator Casings. 
 
 of setting indirects in the Detroit Post Office, which is shown in 
 Figure 52. Mr. Henry Adams, of Baltimore, Md., was the engineer 
 for this work. (The Engineering Eecord, August 7, 1897.) 
 
CHAPTER VII. MECHANICAL VENTILATION- 
 GENERAL PRINCIPLES. 
 
 Need of proper ventilation. It may be stated as an undeniable 
 truth that no system of ventilation is adequate to give proper 
 results at all times and in all kinds of weather, unless it is a me- 
 chanical system. As has been seen in a previous chapter, the air 
 discharge of an ordinary ventilating flue with the gravity system 
 depends upon the difference in temperature between the air in the 
 flue and the outside air, so that its discharge is very different in 
 moderate from what it is in very cold weather. Very satisfactory 
 results are in many cases obtained from indirect radiators, but the 
 same is true of these as of an ordinary ventilating flue. And every 
 one now knows of the precarious nature of ventilation by open 
 doors and windows, since in cold weather the occupants of rooms 
 invariably prefer warm and bad air to that which is cold and fresh. 
 Yet those who have been interested in the subject, for as long as 
 a decade, can readily recall the days when such means of ventila- 
 tion were considered entirely sufficient even for schools, churches 
 and other densely-peopled buildings. It is part of the marvelous 
 scientific development of the close of the nineteenth century that 
 there has been such an advance in the popular appreciation of the 
 necessity and value of good ventilation, that a very fair percent- 
 age of school-houses now erected, even in the smaller communities, 
 boasts of a complete ventilating plant. 
 
 There are, however, many such plants that are in reality not 
 the perfect ones they are made to appear, and the problems con- 
 nected with the proper distribution of an adequate volume of air 
 to and through buildings and rooms of various kinds are more 
 varied and complicated than is ordinarily supposed. Only those 
 who have had much experience with them and who have met with 
 failures in some of their cherished schemes of ventilation, realize 
 that air is a very subtle medium of control. It is a comparatively 
 simple matter to obtain a large blower and connect it by a system 
 of ducts to the rooms to be ventilated, but to admit the air into 
 the rooms in sufficient volume without drafts and make it circu- 
 late where it is needed is a different proposition. The air currents 
 
STEAM HEATING AND VENTILATION. 97 
 
 have an exasperating way of going around the ceiling instead of 
 across the breathing line; or of running down walls and out of 
 doorways instead of across the room and out of properly-prepared 
 vent openings. Another source of tribulation is the fact that in 
 winter the temperature of the fresh air blown in is in most cases 
 warmer than the average temperature of the room; while in sum- 
 mer it is somewhat cooler, so that in the former case the incom- 
 ing air tends to go to the ceiling., and in the latter to the floor. 
 
 There are a few old-time fallacies,, vestiges of which still linger 
 to a surprising degree in the minds of many who appreciate the 
 necessity of good ventilation. Among these are the ideas that 
 fresh air must be cold and that it must be admitted through win- 
 dows, and the foul air be drawn off through vent flues-. But the 
 worst of all is one of the carbonic-acid theories, which is to the 
 effect that exhaled air is laden with carbonic-acid gas (C0 2 ), which, 
 being heavier than pure air, sinks to the floor, and may be tapped 
 off by putting an outlet anywhere at the floor-level. This notion 
 seems to be firmly grounded into the minds of many, who cling 
 to it steadfastly. It is difficult to explain to these unfortunates 
 that the air exhaled by man contains ordinarily 'less than 5 per 
 cent, of carbonic acid, which would not affect the specific gravity 
 to an appreciable degree; and that furthermore there is an indis- 
 putable natural law known as the diffusion of gases, in accordance- 
 with which two gases in 'contact tend to form a perfect mechan- 
 ical mixture. 
 
 The carbonic-acid gas in the air of rooms is, however, an impor- 
 tant consideration, as it serves as an accurate index of the degree 
 of vitiation. It must be understood, of course, that the carbonic- 
 acid gas in itself is not injurious and is merely an index. The air 
 of the stuffiest lecture room that one ever goes into does not con- 
 tain more than 50 parts in 10,000, and air that contains as much 
 as 15 parts in 10,000, due to being repeatedly breathed, is of a, 
 very unhealthy quality. Notwithstanding this, in soda-water fac- 
 tories the air frequently contains as much as 150 or 200 parts of; 
 C0 2 to 10,000, and is in no way injurious. In air that contains as, 
 much as 10 or 15 parts of C0 2 in 10,000, due entirely to exhala-. 
 tions from the body, it is not so much the C0 2 that constitutes the 
 obnoxious element, as it is the organic matter and the germ-laden 
 moisture that accompanies it not necessarily disease germs, but 
 all kinds of natural germs, which are more or less injurious, and 
 
8 STEAM HEATING AND VENTILATION. 
 
 which, together with the organic matter given off in the moisture 
 of the breath, gives to confined air that oppressive and stuffy ef- 
 fest which is at once disagreeable and exceedingly unhealthful. 
 
 It is not intended here to go into detail in regard to the ill effects 
 of breathing vitiated air and the hygienic value of good ventilation. 
 The absurdity of expecting to develop bright and healthy children 
 by sending them day after day to shut-up school rooms, or of ex- 
 pecting inspiring results from sermons or lectures delivered in 
 close and stuffy halls, or of having popular reading rooms or thea- 
 ters where the air is laden with the peculiar aroma of a mixed and 
 varied populace, is rapidly being better and better understood, and 
 more and more widely appreciated. 
 
 There is no doubt but that in a large room which is occupied for 
 some length of time by a crowded assembly it is impossible to se- 
 cure air of the same purity as that outside, as the breath from 
 the occupants vitiates the incoming air as well as that which is 
 already in the rooms. In other words, it is impossible for the 
 occupants of a room to inhale pure incoming air and exhale it so 
 that it will pass out by a vent shaft without a portion of it com- 
 ing in contact with anyone else. If this were the case it would 
 only be necessary to supply from 12 to 15 cubic feet of air per 
 person per hour, which is about the rate of breathing of adults, in 
 order to insure perfect ventilation. As a matter of fact, however, 
 the best we can do is to dilute the vitiated air as much as possi- 
 ble, and it has been found that to accomplish this to a satisfactory 
 degree requires from 100 to 200 times the amount of air above 
 mentioned per person per hour. 
 
 Pure air is found by investigation to contain very close to 4 parts 
 of C0 2 in 10,000. The opinions of many able hygienists agree that 
 when the proportion of C0 2 exceeds 6 parts in 10,000 the bad 
 effects of poor ventilation begin to be noticeable, and when 8 
 parts in 10,000 are found, the characteristic odor of an ill-venti- 
 lated room is apparent; and to those who remain in such an at- 
 mosphere for any length of time there comes a feeling of close- 
 ness, lassitude and dullness. It is therefore universally agreed 
 that when the carbonic acid is formed entirely by the breathing 
 of the occupants, the quantity should not exceed 6 parts in 10,000, 
 though 8 parts may in some cases be permitted for short periods, 
 and that anything in excess of this figure indicates poor ventila- 
 tion. 
 
STEAM HEATING AND VENTILATION. 99 
 
 Air required for ventilation. The amount of fresh air required 
 depends upon the number of people and the amount of carbonic- 
 acid gas given off by each individual in breathing. This last factor 
 is exceedingly variable, depending upon the weight, age and physi- 
 cal, as well as mental, condition of the person. Pettenkofer, a 
 very painstaking scientist, gives the following figures for the aver- 
 age amount of carbonic-acid gas given off per hour by adults per 
 pound of weight: 
 
 In repose 0.00424 cubic feet. 
 
 In general exercise 0.00591 cubic feet. 
 
 In hard work 0.0122 cubic feet. 
 
 In sleep, about 0.00320 cubic feet. 
 
 He also adds that the amount given off by young children is nearly 
 twice as much per pound of weight as for adults. Some diseases, 
 such as fever, increase the amount, and others decrease it. Pet- 
 tenkofer's figures would make the average for persons in repose 
 about as follows: 
 
 Males (160 pounds weight) 0.68 cu. ft. per hr. 
 
 Females (120 pounds weight) 0.51 cu. ft. per hr. 
 
 Children (80 pounds weight) 0.68 cu. ft. per hr. 
 
 Parkes, in his work on hygiene, gives as the amount of carbonic- 
 acid gas given off during repose the following: 
 
 Males (160 pounds weight) 0.72 cu. ft. per hr. 
 
 Females (120 pounds weight) 0.60 cu. ft. per hr. 
 
 Children (80 pounds weight) 0.40 cu. ft. per hr. 
 
 Average mixed community 0.6 cu. ft. per hr. 
 
 These figures show some variation from Pettenkof er's ; but cer- 
 tainly for adults the variation is not more than might be found in 
 two sets of individuals. It is very generally accepted by hygienists 
 that 0.6 cubic foot per hour represents a very fair average for 
 such mixed assemblies as are found in theaters, lecture rooms, 
 churches, etc. 
 
 The amount of air required per person per hour to maintain 
 the air of a room at a certain standard of purity may be worked 
 out by a simple algebraic calculation, as follows : 
 
 Let V be the volume of air required per person per hour for 
 continuous occupation: 
 
 N, the number of persons in the room; 
 
 E, the number of parts of C0 2 gas to be allowed per 10,000, the 
 number of parts in the fresh incoming air being 4; 
 
100 STEAM HEATING AND VENTILATION. 
 
 C, the total number of cubic feet of C0 2 acquired by the air of 
 the room per hour; 
 
 10,000 C 
 Then R = - , 
 
 VN 
 
 VIST X 4 
 
 But C = -- h 0.6 N, 
 10,000 
 
 VN X 4 + 6,000 N" 
 So that E = - - . 
 
 VN 
 
 Solving this equation with N = 1, we find V = 6,000 -f- (R 4). 
 For R = 6, we have V = 3,000; f or R = 7, V = 2,000; while if we 
 allow R = 8, we have V = 1,500. 
 
 Now if the room is of large volume and is only to be occupied 
 for a short period, and before occupancy the air is brought to the- 
 same standard of purity as the outside air, then a less amount of 
 air is required. For example, if the room contains 500 cubic feet 
 of space per person and is to be occupied but one hour, then ob- 
 viously 3,000 500 = 2,500 cubic feet will have -to be supplied 
 the first hour to have the air within the standard of 6 parts of 
 carbonic acid gas per 10,000. 
 
 We may reduce this to algebraic form as follows: 
 
 Let V be as already given ; 
 
 v, the volume per person per hour for a short occupancy, 
 H, the number of hours to be occupied, 
 
 and Y, the cubic feet of space in the room per person. 
 
 Y 
 
 Then v = V -- . 
 H 
 
 From this formula Table No. 1 is calculated. 
 
 TABLE NO. 1. THE VOLUME OF AIR TO BE SUPPLIED PER PERSON 
 PER HOUR THAT THE PURITY OF THE AIR AT THE END OF THE 
 OCCUPANCY WILL NOT EXCEED THE AMOUNT GIVEN. 
 Number of hours to be occupied. 
 
 space in Parts of CO 2 in 10,000 not to be exceeded at end of occupancy, 
 room per 67 8 678 67 
 
 person. 
 
 Cubic feet to be supplied per person per hour. 
 
 100 
 
 2,900 1,900 1.400 
 
 2,950 1,950 1,450 
 
 2,970 1,970 1,470 
 
 200 
 
 2,800 1,800 1,300 
 
 2,900 1,900 1,400 
 
 2,935 1,935 1,435 
 
 300 
 
 2,700 1,700 1,200 
 
 2,850 1,850 1,350 
 
 2,900 1.900 1,400 
 
 400 
 
 2,600 1,600 1,100 
 
 2,800 1,800 1,300 
 
 2,870 1,870 1,370 
 
 600 
 
 2,400 1,400 900 
 
 2,700 1,750 1,250 
 
 2,800 1,800 1,300 
 
 900 
 
 2,100 1,100 800 
 
 2,550 1,550 1,050 
 
 2,700 1,700 1,200 
 
STEAM HEATING AND VENTILATION. 101 
 
 Prom the figures given it will be seen that the quantity of air to 
 be supplied per person depends upon the size of the room and the 
 length of time it is occupied as well as the standard of purity de- 
 manded. 
 
 The standard of purity to be required depends somewhat upon, 
 the nature of the room. Some rooms, such as churches, lecture 
 rooms, theaters, libraries, and some reading rooms, are occupied 
 by widely varying numbers of people, being sometimes very 
 crowded and sometimes but partially filled; while others, school 
 rooms and hospitals in particular, are occupied almost always by 
 about the same number. Of the former class, if the cubic feet of 
 air required is based upon the maximum crowded capacity, we 
 may allow between 7 and 8 parts carbonic acid gas per 10,000 at 
 the end of the period of occupancy, inasmuch as they are crowded 
 only on rare occasions, and are also assumed to be thoroughly ven- 
 tilated before occupancy, as of course should be the case, the pro- 
 portion of carbonic acid gas reaching the maximum only toward 
 the end of the occupancy period. In schools and hospitals we 
 -should never allow over 6 parts in 10,000, and as these are occu- 
 pied for long periods fully 3,000 cubic feet of air should be allowed 
 per person per hour, and in many hospitals, on account of the 
 condition of the occupants, much more. Churches, theaters and 
 lecture rooms, besides being occupied by a variable number, are 
 occupied for from one to three hours at a time, while libraries and 
 reading rooms may be said to be occupied continuously. 
 
 An inspection of the table and formulas already given, with 
 proper allowance for the considerations here cited, will warrant 
 the use of Table No. 2. 
 
 TABLE NO. 2. AMOUNT OF AIR TO BE SUPPLIED PER PERSON PER 
 HOUR IN BUILDINGS OF VARIOUS KINDS. 
 
 Hospitals 3,600 to 5,000 cu. ft. per hour 
 
 Barracks 3,000 cu. ft. per hour 
 
 Schools 2,500 to 3,000 cu. ft. per hour 
 
 Libraries based on crowded capacity 2,000 cu. ft. per nour 
 
 Reading rooms based on crowded capacity 2,200 cu. ft. per hour 
 
 Churches based on crowded capacity 1,400 cu. ft. per hour 
 
 Lecture rooms based on crowded capacity 1,500 cu. ft. per hour 
 
 'Theaters based on crowded capacity 1,400 cu. ft. per hour 
 
 For the latter, based on maximum seating capacity : 
 
 Churches 1,400 cu. ft. per hour 
 
 Lecture rooms 1,800 cu. ft. per hour 
 
 Theaters 1,600 to 1,800 cu. ft. per hour 
 
102 STEAM HEATING AND VENTILATION. 
 
 No room which is occupied for more than five hours continuously 
 by a definite number of adults is adequately ventilated with a less, 
 allowance than 2,400 cubic feet per hour per individual, and 3,000 
 should be given. 
 
CHAPTEE VIII. SYSTEMS OF MECHANICAL VENTILA- 
 TION. 
 
 In the last chapter were discussed the general principles on 
 which depend the volume of air necessary to give good ventilation ; 
 the next point for consideration is the method by which this air 
 is to be supplied and distributed. In the earlier days of me- 
 chanical ventilation two general systems of air distribution were 
 considered, the plenum or pressure system, and the exhaust sys- 
 tem. In the former the fresh air is drawn from the outside and 
 forced by the fans into the rooms to be ventilated, and finds its 
 way out again through flues provided for t e purpose. In the ex- 
 haust system, flues or ducts are provided for the inlet of the air, 
 but the fans are connected to the outlets and the circulation of 
 air is maintained by drawing out the vitiated air and allowing the 
 fresh air to take its place. 
 
 The plenum system is generally considered more direct and posi- 
 tive, but this idea arises largely from the fact that when the ex- 
 haust system has been used alone the fans are connected to flues in 
 the top of the room, and the inlets, if provided at all, are small and 
 poorly located, so that most of the incoming air comes from doors 
 and windows and passes out of the flue without coming much in 
 contact with the occupants. Theoretically, either system is effi- 
 cient if it is properly designed and arranged, but the best results 
 are, generally obtained in practice, especially for large halls or 
 rooms, by a combination of both systems. Some years ago many 
 rooms were ventilated on the principle that if a sufficient quantity 
 of fresh air were forced into a room, it could find its way out 
 through doors and windows. This was soon found to be a mis- 
 take, as in winter all windows and doors would be closed on ac- 
 count of cold and the outside winds ; and it is impossible to force air 
 into a room unless an adequate outlet is provided. 
 
 In the opinion of the author, the distribution of the air supply is 
 even more important to the success of a ventilating system than 
 the volume, and there is much that might be written on what not 
 to do. It is difficult to lay down general rules, as each separate 
 
104 STEAM HEATING AND VENTILATION. 
 
 ease requires careful study, with proper consideration of the local 
 conditions. The use to which the room is to be put, the arrange- 
 ment of the occupants (whether the seats are fixed or movable), 
 the duration of occupancy, the method of heating, the kind and 
 extent of the outside exposure and the height of the room must 
 all be taken carefully into account in determining the location of 
 inlets and outlets. The point that must be borne constantly in 
 mind is that the most perfect ventilation is desired not at the 
 top of the room, or along the floor, but at the breathing line, which, 
 as a rule, is about 4 feet above the floor level. There are very 
 many rooms, unfortunately, which are much better ventilated at 
 the ceiling than at the breathing line. 
 
 Upward versus downward ventilation. There is one question 
 which enters more or less into every problem of ventilation, but 
 especially into that of theaters, churches and other large halls, 
 which is a source of continual and arduous discussion among archi- 
 tects and ventilating engineers that is, the respective value and 
 merits of upward and downward ventilation, the former referring 
 to supplying the fresh air at the floor and drawing the vitiated air 
 out at the top, and the latter to the reverse of this method. The 
 upward method is decidedly the natural one, as the temperature 
 of the air is normally about 30 degrees lower than the temperature 
 of the body, and the latter gives off enough heat when in repose to 
 raise the temperature of 1,800 cubic feet of air per hour 10 de- 
 grees. A person, therefore, standing in an open space, creates 
 an upward current which naturally carries the exhalations from 
 the body away from it. The downward method of ventilation must 
 necessarily be opposed to the tendency of the individual currents 
 from the bodies of the occupants of the room, and carries the 
 breath back upon them, requiring a larger volume of incoming air 
 to effect proper dilution than the upward method. 
 
 In rooms which are heated entirely by the incoming air, the 
 temperature of the latter is frequently much higher than the aver- 
 age temperature near the occupants, and in cold weather is fre- 
 quently higher than that of the body. In this case the air loses 
 its heat, as the air descends, and to a large extent the natural cir- 
 culation is downward. But in such cases the chief loss of heat is 
 due to outside walls and windows, and the consequence is that 
 there is a strong current downward at the windows, and along 
 the floor to the outlets, while a large part of the breathing line 
 
STEAM HEATING AND VENTILATION. 105 
 
 escapes with what ventilation conies from a meager degree of dif- 
 fusion. Prof. S. H. Woodbridge, in his admirable report to the 
 Committee on Rules of the United States Senate (rendered De- 
 cember 14, 1895), on the Heating and Ventilation of the Senate 
 Wing of the United States Capitol at Washington, has an interest- 
 ing discussion of this subject, especially in reference to large halls, 
 and contains the following summary of his views upon the sub- 
 ject : 
 
 "Especially when the walls of the auditorium are inside walls 
 and warm, the air supply does not then have to carry surplus heat 
 to compensate for loss through cold outer walls and windows. It 
 must generally enter the room cooler than the air of the room be- 
 cause of the animal furnaces within it, each occupied chair repre- 
 senting approximately the heating effect of a burning candle. In 
 legislative halls the temperature of the air supplied is generally 
 from 2 to 5 degrees lower than the air of the room. In crowded 
 auditoriums, as theaters, the temperature of the supply has been 
 known to have been held for hours from 10 to 15 degrees lower 
 than the auditorium temperature, the per capita hourly supply 
 being in excess of 1,200 cubic feet. 
 
 "When air cooler than the air of a room enters it in large quan- 
 tities, the most rational, as also the safest, way of admitting it is 
 in a quiet and well-diffused manner through the floor. It then 
 finds itself in its natural position of stable equilibrium. Because 
 cooler, it is also heavier than the air of the warmer room, and it 
 is at once in its normal position at the floor, where it envelops the 
 breather, or is ready for easy, short and direct movement to the 
 user. The warmer and polluted air is above, and in its own natural 
 position or stable equilibrium, and ready for the shortest and 
 easiest escape through the ceiling vent. 
 
 "Ventilation by removal is the most perfect of all methods, both 
 in the completeness of its work and in the economy of its opera- 
 tion. The nearest possible approach in practice to ventilation of 
 occupied rooms by the removal method is found when one is sur- 
 rounded by cool, pure, quiet and abundant air which the heat of 
 the body can freely move in an approaching and enveloping and 
 ascending current about and from the body. That is upward ven- 
 tilation. If the conditions are reversed, the fresh air entering 
 at the ceiling and the spent being withdrawn at the floor, the fol- 
 lowing results seem inevitable : 
 
106 
 
 STEAM HEATING AND VENTILATION. 
 
STEAM HEATING AND VENTILATION. 107 
 
 "First, the entering air being cooler and more dense than that 
 within the room, it must be entered in greatly diffused form to 
 escape the production of drafts, since its weight must cause its 
 precipitation ; and if it falls either by the swooping down en masse, 
 now here and now there, or by continuous flow from large and 
 scattered wall or ceiling inlets, the effects will vary from the an- 
 noying to the intolerable, according to the momentary or continu- 
 ous action of such down-flowing drafts. The condition of stable 
 equilibrium is reversed by such a procedure, and nature's effort 
 to restore that equilibrium must necessarily result in disturbance. 
 
 "Second, the mass movement of air being downward, is in direct 
 conflict with the individual currents, which are upward. The indi- 
 vidual currents rise, as may be shown by experiment, and as may 
 be also seen by the ascent of smoke entangled in the breath, with 
 a movement varying from 20 to 40 feet per minute. To turn these 
 individual currents downward, and to insure their moving from 
 the nostrils and body floorward would require a mass downward 
 movement of the air over the entire area of the Chamber of about 
 30 feet per minute, which would be equivalent to a per-minute 
 supply for the floor alone of 129,000 cubic feet of air. The ascend- 
 ing individual currents average from 40 to 50 cubic feet per min- 
 ute, under favorable conditions of supply of fresh air to the body, 
 and of rise of vitiating air from it. To completely reverse this air 
 flow, about twenty-five times such quantities in mass movement 
 would be required. 
 
 "Unless such a complete reversal is effected, the occupant must, 
 in downward ventilation, breathe air which contains his own and 
 others exha 1 1 breath and dermal vapors turned back upon him. 
 He is in the p^Jtion of a candle burning at the bottom of an open 
 pipe through which the air current is being unnaturally forced 
 downward. He is at the discharge end of the ventilating system 
 rather than at the supply end. He is breathing a dilution of com- 
 posite eliminations. The effect on gas flames distributed and 
 burning at the floor of a chamber, to which the controlled air 
 supply was admitted in diffused form, showed that by the down- 
 ward method of supply the luminosity of flame is less than 5 per 
 cent, of that obtained when the same air quantity is used with 
 upward ventilation, the quantity of air used being a little more 
 than sufficient to bring the flames to a maximum luminosity by up- 
 ward ventilation. The life of the flame seemed even then to de- 
 
108 
 
 STEAM HEATING AND VENTILATION. 
 
 pend on the local down drafts of fresh and cool air, which was 
 denied admission at the bottom of the Chamber, the place of its 
 natural entrance. 
 
 "Upward movement makes necessary the use of only enough 
 air to supply the individual upward currents, in order to envelop 
 the occupant in the purest air it is possible to provide by artificial 
 ventilation methods. In crowded theaters it has recently been 
 found that with a well-diffused air supply of 1,200 cubic feet per 
 capita per hour the air below the breathing line can be kept with- 
 in 1 part in 10,000 of carbonic-acid increment. 
 
 F'O-58 U F.G.59 
 
 THC EMGMtcnt 
 
 Types of Diffusers for Theaters. 
 
 "The contrast between results of upward and downward audi- 
 torium ventilation with equal air quantities can perhaps be best 
 imagined by considering the effects on a theater floor crowded 
 with smokers. 
 
 "Third. In the case of the Senate Chamber, the galleries, fre- 
 quently occupied with persons of varying degrees of cleanliness, 
 become an important factor. To so ventilate as to carry the gal- 
 lery air downward through the Chamber floor would be a piece of 
 professional malpractice. 
 
STEAM HEATING AND VENTILATION. 10i> 
 
 "The only logical reason to be advanced in favor of downward 
 ventilation is cleanliness; that is, if the air passages of the floor 
 are foul, then downward ventilation does not bring a contamina- 
 tion due to that foulness into the Chamber. Practically, however, 
 it is exchanging a seen and relatively harmless offense for the un- 
 seen menaces of vitiated airs. Moreover, the only vestige of a 
 reason for downward ventilation disappears when air is draftlessly 
 moved through the floor and through channels and chambers so 
 constructed and cared for as to insure cleanliness. In this con- 
 nection it should be said that a thorough investigation of the 
 supply chambers made at the close of the .last Congress and before 
 any cleaning had been done, revealed a condition of cleanliness 
 which was as gratifying as it was surprising, because of much that 
 has been said and also because of my own preconceptions to the 
 contrary." 
 
 This is a strong argument in behalf of the upward system for 
 ventilating halls of such a character. In the writer's opinion, the 
 argument is unassailable and the success of Prof. Woodbridge's 
 work in the Senate Chamber makes it especially forceful. The 
 argument that is frequently made against the upward method is 
 that it is difficult to secure a proper distribution of the incoming- 
 air without causing disagreeable drafts on the feet and legs of 
 the occupants. With the upward system the inlets must be dis- 
 tributed among the seats, since, if the air is admitted through 
 large registers in the aisles, it ascends straight to the ceiling with 
 but little effect on the occupants. 
 
 Air inlets and outlets. When the air is admitted by small open- 
 ings under the seats the creation of drafts is difficult to avoid. Dif- 
 ficult it is, but by no means impossible. The inlets must be so 
 large that the incoming air has a low velocity (not over 150 feet, 
 or at the most 200 feet per minute) and so arranged that the air 
 does not strike directly against the legs of the occupants. The 
 trouble in most cases of the kind is that the inlets are not nearly 
 large enough. If in a theater, for example, we are going to have 
 1,800 cubic feet per person per hour, and this is to come in at a 
 velocity of 150 feet per minute, it will be seen that a register 
 about 6 inches by 5 inches or 2| inches by 48 inches will be re- 
 quired under every seat in the house. Furthermore, this inlet 
 should not be right in the floor, but should be raised up a few 
 inches. Figures 53, 54, 55 and 56 show some forms of "diffusers" 
 
110 
 
 STEAM HEATING AND VENTILATION. 
 
 recommended by Prof. Woodbridge for the Senate Chamber, and 
 Figures 57, 58 and 59 some other practical forms for theaters. 
 For churches it is easy to contrive simple forms for long narrow 
 inlets along the pews. It will be seen that all of these arrange- 
 ments requires that the inlets be connected to a large plenum cham- 
 ber underneath or that the arrangement of ducts be such as to give 
 a perfectly uniform distribution of the air to the numerous inlets. 
 
 F.e.60 
 
 Infet: 
 
 Fio.61 
 
 A little reflection will show that in a large theater, for example, 
 if the downward ventilation is employed, it is quite as necessary to 
 have the outlets well distributed as with the reverse method. The 
 Chicago Auditorium, a very large theater, is ventilated on this 
 scheme. The outlets are under the seats, but are small and not 
 frequent. The consequence is that most of the air, coming down 
 from above, goes out the exits, which are numerous, and the 
 large outlets back of the boxes, leaving a pocket in the middle of 
 the house which frequently becomes very close. 
 
 For smaller rooms, such as school rooms, small churches, lee- 
 
STEAM HEATING AND VENTILATION. 
 
 Ill 
 
 ture and reading rooms, there are many methods of air distribution 
 which have proved successful in accomplishing the desired result 
 of ventilating along the breathing line. Figure 60 shows a method 
 which is much used in schoolhouses, and in rooms not over 30 feet 
 
 wide it is very suc- 
 cessful. If the rooms 
 are of much greater 
 width there should be 
 inlets and outlets on 
 both sides. Figure 61 
 is another method 
 much used in school 
 houses. Figure 62 is 
 a very practical ar- 
 rangement for small 
 churches, but it obvi- 
 ously requires that, 
 especially in winter, 
 the roof and windows 
 be very tight. These 
 three figures show 
 vertical sections 
 through the rooms. 
 
 Figure 63 shows a 
 very wasteful method 
 of ventilation which is 
 employed in the read- 
 ing rooms of a large 
 library. Most of the 
 air in this case (especi- 
 ally in mild weather) 
 goes down the walls 
 and out without af- 
 fecting the breathing 
 line. An improvement 
 Figure 64. Ventilation in a Syracuse Bank. could be effected by 
 
 putting inlets at the 
 
 point A. There is always a tendency of air currents to cling to 
 
 wall surfaces and this should always be taken into consideration. 
 
 Figure 64 shows a diagram of the ventilation of the large bank- 
 
 Plan. 
 
112 STEAM HEATING AND VENTILATION. 
 
 ing room of the Onondaga County Savings Bank at Syracuse, N. Y. 
 The arrangement is very successful, and, on account of the fact 
 that the clerks are employed at the windows all day long, may be 
 preferable to a reversed arrangement of inlets and outlets; but 
 with the system employed, the air supply is very ample in propor- 
 tion to the number of regular occupants. 
 
 Air velocities through inlets and outlets. As to the size of inlets 
 and outlets for large registers for ventilating schemes of this kind, 
 standard practice allows a velocity of about 300 feet per minute 
 through the gross area of the register. Naturally a rule of this 
 kind is dependent upon circumstances, and if an inlet has to be 
 where air will blow directly on any of the occupants, the velocity 
 should be slower. Mr. Wolff states that when air enters at or near 
 the floor, the velocity should not exceed 120 feet per minute. The 
 author has taken 180 feet per minute as a maximum in such cases. 
 This figure may be used if diffusers are arranged so that the air 
 will not blow directly on the feet and ankles of the occupants. 
 Where the inlets are removed from the danger of direct drafts on 
 the occupants, a velocity of 300 feet per minute may be used with 
 safety. In hospitals and similar institutions, the inlets and out- 
 lets should be very carefully placed to meet the requirements of 
 the particular arrangement of beds, and velocities should be low. 
 The velocities through outlets may range from 400 to 600 feet per 
 minute. 
 
 There is another consideration which should be discussed at 
 this point, as it seriously affects the question of air distribution. 
 That is the question of heating by means of the ventilating air. In 
 the opinion of the author, this is never desirable in a room of what 
 we have called the densely peopled character. Especially where 
 there is any considerable amount of glass or exposed wall surface, 
 there should be heating coils in the room sufficient at least to 
 counteract the loss of heat from such surfaces; otherwise the in- 
 coming air must in cold weather have a temperature of about 130 
 degrees or more and is very hard and dry. In such cases the inlets 
 must be very high, so as not to be near the occupants. Besides 
 this, such a great difference in temperature between the incoming 
 air and the average of the room creates currents which interfere 
 with the uniform circulation desired, in addition to making it very 
 difficult to maintain a uniform temperature throughout the room. 
 
CHAPTEE IX. VENTILATING DUCTS. 
 
 Theory of the flow of air in ducts. Any flow of air is created only 
 by an inequality in the pressure of the air at two different points, 
 and it follows that the primary requisites for a ventilating system 
 are a means for creating the required difference in pressure and 
 a means for distributing the flow of air to required points. As 
 accessory to the first of these there is generally required some 
 means for heating the air and frequently for washing it. 
 
 The theoretical laws which govern the flow of air are very dif- 
 ficult of direct application to ventilating conditions, and yet a clear 
 
 FIG. 65 
 
 FiQ.66 
 
 Fio.67 
 
 understanding of the principles governing the air flow is necessary 
 to the successful understanding of the way in which air can be 
 handled in a ventilating system. 
 
 Consider the simplest case : a pipe or duct, AB, Figure 65, of in- 
 definite length, in which a flow of air is created from A to B. This 
 flow can only be kept up by maintaining the air pressure at A in 
 excess of that at B; and the greater this excess, the greater will 
 be' 'the velocity of air in the duct. Let us denote this excess, or 
 difference, of pressure by p. It can be measured in pounds per 
 square inch, ounces per square inch or in the height of the water 
 
114 STEAM HEATING AND VENTILATION. 
 
 column which it will balance. In ventilating work, since p is gener- 
 ally small, it is measured in one of the two latter units; and a 
 column of water 1 inch high is equivalent to 0.579 ounce per square 
 inch. The pressure p has two functions to perform; it must create 
 the velocity (v) of air in the duct and it must overcome the fric- 
 tional resistance to the passage of the air. X ow, if it were not for 
 the friction of the air in the pipes, the velocity could be expressed 
 by the familiar formula 
 
 v = 1/Tgh 
 
 in which v is given in feet per second and h is the height in feet 
 of a column of air, the weight of which would give the pressure p 
 which creates the flow. If p is expressed in inches of water 
 column, h = [67.7 + (t -f- 520)] p, where t is the temperature of 
 the air; and as g = 32 (approximately) in the foot-pound-second 
 fiystem of units, the formula becomes: 
 
 t \ 
 
 (1) 
 
 As already stated, this represents the theoretical velocity that 
 would be attained if there were no frictional resistance to be over- 
 come. This formula is not absolutely accurate even for the theo- 
 retical velocity without friction, on account of the compressibility 
 of air, but with the pressures attained in ventilating plants, the 
 factor of correction would amount to a very small fraction of 1 
 per cent. But as it is, the actual velocity (v 1 ) may be anything 
 irom 0.2 v to 0.7 v, and under the conditions of most ventilating 
 plants it is from 0.3 v to 0.6 v. Or, v 1 being the actual velocity, 
 we may put 
 
 where c is a coefficient which will vary from 2.4 to 5 according to 
 the nature of the resistance to be overcome, its maximum value 
 teing 8 for the theoretical velocity without friction. 
 
 Prof. Unwin gives a formula for the flow of air in round pipes 
 which is as follows : 
 
 = / 
 
 V 
 
 T d 
 
 4ml p o s 
 
 in which k = 53.15; T = absolute temperature of air; g = 32.2; 
 
STEAM HEATING AND VENTILATION. 115 
 
 d diameter in feet; 1 = length in feet; m = a coefficient of fric- 
 tion; p = the greater absolute pressure and p x = the lesser press- 
 ure. The difficulty, however, with any such formula as this is that 
 in any ventilating system with a complicated arrangement of ducts, 
 containing, as it must, bends and branches, dampers, rectangular 
 pipes and round, registers, heating coils, etc., it is beyond the pos- 
 sibility of theoretical calculation to obtain any adequate value for 
 a coefficient of friction. 
 
 The pressures employed in ventilating systems do not usually 
 exceed 1 ounce per square inch, nor the velocity 50 feet per sec- 
 ond, or 3,000 feet per minute. 
 
 The accompanying table gives the velocity v 1 as obtained by 
 formula (2), already stated, for air at 60 degrees Fahr. and 
 various values of c and different pressures, p. This table is rather 
 
 TABLE OF AIR VELOCITIES TEMPERATURE 60 DEGREES FAHR. 
 
 ., p x , v 1 in feet per second * 
 
 Inches Oz. per 
 
 water. sq. in. c = 2.4 c = 3. c = 4. c = 5. 
 
 0.01 .006 2.0 2.5 3.3 4.1 
 
 0.05 .030 4.4 5.6 7.4 9.2 
 
 0.10 .058 6.2 7.8 10.4 13.0 
 
 0.20 .116 8.8 11.0 14.6 18.4 
 
 0.40 .232 12.5 15.6 20.8 26.0 
 
 0.60 .347 15.1 18.8 25.2 31.5 
 
 0.80 .463 17.4 21.8 29.2 36.4 
 
 1.00 .579 20.0 25.0 33. 41.2 
 
 2.00 1.158 28.2 34.8 46.4 57.8 
 
 3.00 1.737 34.6 42.7 56.9 71.2 
 
 4.00 2.316 40. 49.5 66.2 82.5 
 
 difficult to apply practically, but it is the writer's experience tha j ; 
 in a well-proportioned system a coefficient of 5 can be used. If 
 the ducts are very long or tortuous, or contain many dampers, a 
 smaller one should be used. 
 
 It will be seen from this table, as well as from formulas (1), (2) 
 and (3) that p is proportional to v 2 . (In formula (3), p p x is 
 equivalent to the p of the table and of the other formulas, and for 
 small values of p, p + p x would be practically a constant.) On this 
 account, in a given system of ventilating ducts, any increase in 
 velocity can be obtained only by increasing the pressure created 
 by the fan, proportionally to the square of the velocities. And 
 as the power required to move the air is practically proportional 
 to the product of the pressure, area and velocity, the power re- 
 quired, exclusive of that used by the friction of fan and engine 
 or motor, is proportional to the cube of the velocity. These laws 
 
116 STEAM HEATING AND VENTILATION. 
 
 should be thoroughly understood by all who have anything to do- 
 with ventilating systems. They would be still more important 
 were it not that the pressures employed in ventilating systems 
 are always small, rarely exceeding 1 inch of water column, equal 
 to 0.579 ounce per square inch. 
 
 Velocity of air in ducts. From what has been said it may be 
 gathered that the design of a system of ventilating ducts is largely 
 a matter of velocities. The velocity in the main ducts may vary 
 from 30 to 65 feet per second, the latter figure being somewhat 
 excessive if the ducts are of any considerable length. For branch 
 ducts the velocities must be lower the smaller the duct the lower 
 the velocity in order to maintain'the proper distribution through- 
 out the system. This seems rather indefinite, and so it is, but 
 there is no branch of engineering which is more strictly dependent 
 upon empirical rules and the experience and study of the designer, 
 than the design of a ventilating system. We may take 35 to 40 
 feet per second as a standard velocity for air in the main ducts, 
 from a fan delivering from 20,000 to 40,000 cubic feet of air per 
 minute. In the branch ducts the velocity should be reduced, ac- 
 cording to the size of the ducts, as low as 20, or even 15 feet per 
 second in small ducts (8 x 10-inch or 6 x 12-inch) supplying indi- 
 vidual registers in small rooms. 
 
 The velocity through the registers should not exceed 5 feet 
 per second through the gross area, except through large ones so- 
 located that there is no possibility of a direct draft on the occu- 
 pants of the room. If these proportions are carried out, the neces- 
 sary pressure at the fan to force air through the ducts will not 
 generally exceed 0.3 ounce per square inch, but it must be borne in- 
 mind that additional pressure is required for heating coils and 
 other similar obstructions. This will be more particularly consid- 
 ered in a subsequent chapter. The pressure necessary will in- 
 crease rapidly as velocities are increased, and must be made up by 
 increased capacity of fans and increased power. 
 
 Branch ducts. In laying out ducts the utmost ingenuity should 
 be exercised in arranging the branches, dampers, etc. All short 
 bends and T-branches should be carefully avoided, as they greatly 
 reduce the flow of air. A frequent specification in regard to bends 
 is that the inside radius of the bend must be equal to the diameter, 
 or equivalent, of the pipe. This should certainly be a minimum 
 and twice that radius would be a preferable minimum. The air 
 
STEAM HEATING AND VENTILATION. 117 
 
 -will frequently pass right by a right-angle branch, as in Figure 
 G6. The velocity in the branch being but a small percentage of 
 that in the main, such connections should be made as in Figure 67. 
 
 Dampers. Dampers are a necessary evil, as they certainly im- 
 pede the flow. They should be used with caution, and the duct 
 system should be laid out in the first place with as few dampers 
 as possible, and in the second place with the idea that under nor- 
 mal conditions the system should be run with all dampers wide 
 open. 
 
 There is a common practice when laying out a complicated sys- 
 tem of ducts with numerous branches and sub-branches of put- 
 ting a damper on every branch, the idea being that if one branch 
 gets more than its share of air it can be "throttled down" by 
 means of its damper, so .that the other branches will get more. 
 The author has hardly found a case in practice where dampers 
 were used in this way but that, in the course of practical experi- 
 ment on the part of an ignorant attendant to proportion the air 
 supply, most, if not all, of the dampers were more or less closed, 
 thus diminishing the air supply and throwing a greater load on 
 the fan. It is not alone the velocity in the ducts that we must 
 look after, but also that at the dampers; a few half-closed damp- 
 ers will have a decided effect upon the pressure required at the 
 fan. 
 
 Dampers should only be put in at or near the registers, and in 
 many cases the system is better off without them even there. The 
 branches must be systematically laid out, and with reasonable 
 care they can be properly proportioned without adding dampers 
 to act as a safeguard on the designer. 
 
 The ordinary butterfly damper, hung by the rod in the middle, 
 is the type most employed. They should be firmly attached to 
 the rod, so that they cannot work loose. The damper should fit 
 loose in its duct and should always be provided with a substantial 
 attachment by which its position can be set and secured from the 
 outside. 
 
 Arrangement of ducts. In large plants the ducts usually radiate 
 from the fan to the registers in a tree-like pattern; but in the 
 opinion of the author, although apparently the simplest, this is 
 in reality the most complicated possible way to lay out a ventilat- 
 ing system; and it is his firm opinion that much better results 
 can be obtained by a system of mains and feeders, to borrow elec- 1 
 
118 
 
 STEAM HEATING AND VENTILATION. 
 
 trical phraseology. The idea of the first system is indicated in 
 Figure 68, and that of the second in Figure 69. The diagram in 
 each case represents the basement of a building, VW being ver- 
 tical flues which it is necessary to supply with air. In Figure 69 
 M may be called the mains and F the feeders. In the "tree" sys- 
 tem of Figr.re 68 it is difficult indeed to prevent the ducts near- 
 est the fan ifrom taking most of the air, and a much more uniform 
 distribution is obtained by the other system, especially if the mains 
 are made large so that the velocity is low. The feeders can then. 
 
 ENGINEERING RECORD. 
 
 Types of Duct Arrangement. 
 
 be proportioned for a comparatively high velocity (45 to 60 feet 
 per second for large systems) without loss. The connection to 
 the vertical flues should, of course, be curved upward from the 
 mains, or the connection made very free. In this system the 
 object is to make the mains something of a plenum chamber in 
 which the velocity is slow and the pressure uniform throughout. 
 
 In a large system, where several fans are used, the best results 
 will be obtained by locating two or three plenum chambers, as 
 mains or as centers of distribution, at central points, from which 
 
STEAM HEATING AND VENTILATION. 119 
 
 the ducts can radiate, and to each of which feeders from the 
 fans can be conducted. 
 
 A large library building in the Middle West is a case in point. It 
 is ventilated by an elaborate system with five large supply fans and 
 as many exhaust fans. The ducts radiate from the fans on the 
 "tree" system, each fan connecting to its own independent system 
 of ducts. The ducts are large and long and ramify through the 
 basement so as to render useless a large amount of valuable space. 
 As the system stands, it is very difficult to adjust the air supply 
 to the different ducts and the pressures on the different fans are 
 very unequal. If two plenum chambers had been located in the 
 center of each end of the building and each of the supply fans 
 connected into one or the other, it would have greatly simplified 
 the air distribution, taken up much less space and equalized the 
 pressure and the load on the different fans, some of which at 
 present are considerably overloaded, while others are the reverse. 
 
 Figure 70 shows the basement plan of a building taken from 
 The Engineering Eecord. The following description of the ar- 
 rangement of ducts accompanied the plan: Fresh air enters 
 through windows at the northeast corner of the basement, where 
 the fan is located. In cold weather the air passes through the 
 windows of a tempering chamber provided with tempering coils,, 
 but in moderate weather this chamber is shut off and windows in. 
 the fan room adjoining are opened to allow the air to pass di- 
 rectly to the fan. By means of an 8-foot blower the air is de- 
 livered into a plenum chamber about 10 x 17 feet in size adjoin- 
 ing the fan room. From this the air is forced to three indirect 
 heating chambers, constructed of brick, located at convenient 
 points in the basement, from which both heated and tempered 
 air may be uniformly distributed by the double duct system to 
 the base of the heat flues. One of these heating chambers is built 
 within the plenum chamber, while the other two are located at, 
 distant points and connected with it by galvanized-iron ducts.. 
 The heating chambers are numbered 1, 2 and 3 in the drawing.. 
 Number 1 is located inside of the main plenum, while the other- 
 two are located at distant points of the basement, as shown. 
 
 It will be seen that in this plant the vertical ducts are sup- 
 plied from the three chambers, which are practically three centers 
 of distribution, but, in the opinion of the author, the system could 
 have been improved by locating four main ducts at M, N, 0, P, and 
 
120 
 
 STEAM HEATING AND VENTILATION. 
 
STEAM HEATING AND VENTILATION. 
 
 121 
 
 supplying these by feeders from the fan at points about at the 
 middle of the mains. The four mains would supply the vertical 
 flues in the four sections of the building and they could be con- 
 nected together by a small equalizing duct forming a sort of ring 
 system around the building. Of course there may be objections 
 to such a system on account of the constructional features of the 
 building, or the special use of certain rooms, and in the case un- 
 der consideration the engineer wished to place a heating coil 
 in each of his centers of distribution; but this being the case, it 
 would have been better to locate four centers of distribution; for 
 example, at D, E, F and G, the object being to make the connec- 
 tions from them to the vertical flues as short and direct as pos- 
 sible. In this case they should each have a feeder from the fan 
 and could be profitably connected by an equalizing duct from 
 which the stray vertical ducts between them could be 
 connected. The question of the distribution of heat- 
 ing coils in ducts will be further considered in a 
 subsequent chapter. Figure 72 represents another 
 building in which three centers could have been 
 very advantageously located at A, B and C. The 
 ducts shown, it may be pointed out, form the ex- 
 haust system of a downward ventilating apparatus 
 installed in this building. 
 
 In regard to vertical flues, they should, if possible, 
 be separate for each outlet; and the longer the duct, 
 the slower the velocity to be allowed. The author 
 is familiar with one building in which some of the 
 vertical flues supply three registers. Each outlet is provided 
 with an adjustable swing damper, as indicated in Figure 71, and 
 it is exceedingly difficult to adjust them so as to give anything 
 like a uniform distribution to the three outlets. 
 
 Materials for ducts. As to the material for the construction of 
 ducts, they are usually made of galvanized iron, in which case they 
 should be soldered at the joints, as it is very essential that they 
 be made air tight. Large ducts are frequently made of sheet iron, 
 and these should be close riveted; and when they are painted, the 
 joints should be thoroughly doped with an asphalt or other simi- 
 lar paint. 
 
 Underground ducts should be made of brick. Wood is objec- 
 tionable in any case, and especially so unless the ground is very 
 
 Fie.71 
 
 V 
 
 V 
 
122 
 
 STEAM HEATING AVZ) VENTILATION. 
 
STEAM HEATING AND VENTILATION. 123 
 
 dry, and they should be lined with tin or galvanized iron to make 
 them tight. Brick ducts should be plastered inside and out all 
 around with a f-inch coat of rich cement mortar, or, preferably, 
 asphalt. There is, among some engineers, but more particularly 
 among ventilating contractors, an opposition to underground 
 ducts. The author has thought this originated with the latter 
 largely from the fact that there is less profit for the ordinary ven- 
 tilating contractor in building brick ducts than there is in iron. 
 The objection is raised that they are liable to become damp and 
 dirty. This is not at all the case if they are properly made. In 
 fact, from the standpoint of cleanliness, they are preferable to 
 iron, as any duct will become very dirty in time, and brick ones 
 can be easily arranged so as to be washed out with a water stream 
 from a hose. Underground ducts must, of course, as a rule, be 
 laid out before the building is built, and it is not generally prac- 
 ticable to put very small ones underground; but with a system 
 designed with centers of distribution and feeder ducts, as sug- 
 gested, the latter could, in most cases, be put underground with 
 great advantage. In the building first referred to, not only the 
 feeder ducts, but the centers of distribution as well, might have 
 been put underground, and at less expense than the existing sys- 
 tem, if the work had been laid out at the proper time. There 
 is an objection to blowing heated air through underground ducts, 
 but this will be considered in the following chapter. 
 
CHAPTEE X. VENTILATING FANS AND OTHEE APPA- 
 
 EATUS. 
 
 Types of fans. There are but two kinds of fans commonly used 
 in ventilating plants. These are the centrifugal fan, or blower, 
 and the propeller,, or disk fan. The distinctive characteristics of 
 the two types are well shown in Figures 73 and 74. 
 
 Figure 73. The Centrifugal Fan. 
 
 The centrifugal fan consists of a wheel with several vanes 
 mounted on a horizontal shaft, as shown in Figure 75, where the 
 covering or casing is removed. It is always mounted in this cas- 
 ing, which may be of wood, brick or iron, but usually the last, 
 although for large fans the bottom part is generally of brickwork 
 and the top of iron. The air enters through an opening in the 
 
STEAM HEATING AND VENTILATION. 
 
 125 
 
 center and is forced to the outlet by the centrifugal action due to 
 the rapid revolution of the fan wheel. 
 
 The disk fan is mounted in an opening in a wall, or in the end 
 of a pipe, and drives air by means of its screw-like action. The 
 disk fan is only used against very light pressures, and consequent- 
 ly, when ducts are very short and openings large and few, the disk 
 fan loses in efficiency rapidly as the pressure rises. 
 
 Centrifugal fan capacities. There is no manufactured machine 
 about which there are so many varying data as there is in connec- 
 
 Figure 74. The Disk Fan. 
 
 tion with ventilating fans. The makers' claims as to capacity are 
 generally too high. 
 
 Mr. Alfred E. Wolff, in his very excellent pamphlet on "The 
 Ventilation of Buildings," publishes the accompanying table, Ta- 
 ble I, for centrifugal fans. This table, like everything else from 
 Mr. Wolff's pen on the subject, is very valuable, although the ex- 
 perience of the author in testing some large fans would indicate 
 that even the capacities here given are somewhat too liberal. 
 
 Mr. M. C. Huyett, an ex-fan manufacturer of extended experi- 
 ence, has published a valuable table of centrifugal fan capacities 
 which is given in Table II. Mr. Huyett's table is based on the 
 
126 
 
 STEAM HEATING AND VENTILATION. 
 
 
 s 
 
 ra- 
 
 
 in 
 
 
 3 
 
 g 
 
 O 
 
 
 i i 
 
 fa 
 
 s 
 
 fc 
 
 
 H 
 
 
 O 
 
 
 U 
 
 
 g 
 
 O 
 
 g 
 
 <l 
 
 
 
 
 
 i 
 
 $ 
 
 m X 
 
 $ 
 
 10 us c-q o i> i 
 
 O5O'-HrH 
 
 TH o o as 
 
 t as c i 
 
 i - y. o -i 
 
 ^CaCCOO 
 
 O ! 9 M* t W 00 U> MB IO WJO IO O O O ^ *** *O ^ O *O fH O 00 
 
f STEAM HEATING AND VENTILATION. 127 
 
 velocity of the fan-wheel periphery multiplied by the "blast area" 
 of the fan. The blast area being practically the area of the blade, 
 is taken as the width of the wheel multiplied by one-third of the 
 diameter. As Mr. Huyett points out, it will be seen that this rep- 
 lesents a maximum velocity for the air, as it is impossible to give 
 to it a velocity greater than that of the wheel rim. The table 
 may, therefore, be taken as representing practically a free air 
 discharge, and checks very close with the author's tests made on 
 fans working under low velocities or free delivery in the ducts. 
 
 TABLE I. QUANTITY OP AIR SUPPLIED BY BLOWERS OF VARIOUS 
 
 SIZES AGAINST A PRESSURE OF ONE OUNCE PER SQUARE 
 
 INCH. (ALFRED R. WOLFF.) 
 
 Diam. 
 
 Revs, per 
 
 H.-P. to 
 
 Cubic ft. 
 
 wheel, ft. 
 
 minute. 
 
 drive blower. 
 
 per minute. 
 
 4 
 
 350 
 
 6. 
 
 10,635 
 
 5 
 
 325 
 
 9.4 
 
 17,000 
 
 6 
 
 275 
 
 13.5 
 
 29,618 
 
 7 
 
 230 
 
 18.4 
 
 42,700 
 
 8 
 
 200 
 
 24. 
 
 46,000 
 
 9 
 
 175 
 
 29. 
 
 56,800 
 
 10 
 
 160 
 
 35.5 
 
 70,340 
 
 12 
 
 130 
 
 49.5 
 
 102,000 
 
 14 
 
 110 
 
 66. 
 
 139,000 
 
 15 
 
 100 
 
 77. 
 
 160,000 
 
 The theoretical calculation of fan discharge is very compli- 
 cated, and, so far as the author's experience goes, is very unreliable 
 on account of the difficulty of obtaining accurate values for the 
 coefficients. 
 
 In a paper in the "Transactions" of the American Society of 
 Heating & Ventilating Engineers, for 1899, Prof. R. C. Car- 
 penter deduces a formula in which the fan "capacity is equal to 
 the product of three constants multiplied by the width of wheel, 
 diameter of inlet, and by diameter of fan wheel into the number 
 of revolutions." He states also that since, by common practice 
 the three first factors are now always made proportional to one 
 another, the formula becomes 
 
 q = c n d 3 , 
 
 by which q is obtained as cubic feet per minute, d being the diame- 
 ter in feet of the fan wheel, n the number of revolutions per min- 
 ute, and c a coefficient, the value of which Prof. Carpenter gives 
 as 0.6 for single-inlet fans under free discharge, 0.5 with a press- 
 ure of 1 inch of water, and 0.4 with a pressure of 1 ounce per 
 square inch. "For fans with double inlets the coefficient should 
 be increased 50 per cent." For practical work on ventilating 
 
128 
 
 STEAM HEATING AND VENTILATION. 
 
 plants Prof. Carpenter recommends c = 0.4. This coefficient 
 gives capacities which are about 10 per cent, less than those of 
 Mr. Wolff's table, and is very reliable where duct velocities are 
 employed such as the author recommends in the preceding chap- 
 ter, with 45 to 55 feet per second in the main duct; but where 
 heating coils and other similar resistance are interposed in the 
 air passages, as is generally the case, a coefficient of c = 0.35 is 
 much safer. 
 
 Prof. Carpenter also gives a formula for the power required to 
 drive centrifugal fans ("Transactions" Am. Soc. Htg. & Vent. 
 Engrs., Vol. V., p. 237), which is: 
 
 HP = b d 5 n 3 -T- 10 6 , 
 in which H P is horse-power delivered to the fan; d, the diameter 
 
 Figure 75. Centrifugal Blast Wheel. 
 
 in feet; n, the number of revolutions per second, and b a coeffi- 
 cient, which should be taken as 30 for free delivery and 20 for de- 
 livery against 1 ounce pressure. This formula, with a coefficient 
 of 20, gives results almost identical with those of Mr. Wolff's 
 table, and may be taken as very reliable for practical work. It is. 
 interesting to note that according to Prof. Carpenter's coefficient,, 
 the power required for free delivery is 50 per cent, greater than 
 when working against a pressure of 1 ounce. This is in accord- 
 ance with experience, as well as theory, but is, of course, due to 
 the fact that the volume of air delivered under free discharge 
 is much greater than under 1 ounce pressure. 
 
 Disk fans. Disk fans, as stated above, are not generally used 
 
Diam. 
 
 Revs, per 
 
 H.-P. to 
 
 wheel, ft. 
 
 minute. 
 
 drive fan. 
 
 2.0 
 
 600 
 
 0.50 
 
 2.5 
 
 550 
 
 0.75 
 
 3.0 
 
 500 
 
 1.00 
 
 3.5 
 
 500 
 
 2.50 
 
 4.0 
 
 475 
 
 3.50 
 
 5.0 
 
 350 
 
 4.50 
 
 6.0 
 
 300 
 
 7.00 
 
 7.0 
 
 250 
 
 9.00 
 
 STEAM HEATING AND VENTILATION. 129 
 
 where large capacity is required, except where the delivery is very 
 free. They are usually employed where exhaust fans are required 
 on roofs, or in other elevated positions where it is impracticable 
 to set the large foundation which the centrifugal fan requires. It 
 is the opinion of the author that the field of usefulness of the 
 disk fan is larger than is generally considered, and that its de- 
 livery is not as much reduced by increasing the resistance under 
 which it works as is usually supposed. The disk fan seems to be 
 used much more in Europe than it is in America. Mr. Wolff 
 gives some valuable data upon disk fans in Table III. 
 
 TABLE III. QUANTITY OF AIR MOVED BY APPROVED FORMS OF 
 EXHAUST FAN DISCHARGING DIRECTLY INTO AT- 
 MOSPHERE. (ALFRED R. WOLFF.) 
 
 Cubic ft. 
 per minute. 
 5,000 
 8,000 
 12,000 
 20,000 
 28,000 
 35,000 
 50,000 
 80,000 
 
 In an article in the "Transactions" of the American Society 
 of Heating & Ventilating Engineers, 1899 (See Vol. V, p. 128;, 
 Prof. J. H. Kinealy gives the following formula for disk fans with, 
 straight vanes set at an angle of 40 or 45 degrees: 
 
 Q = d 3 n -h 3,050, 
 
 where d is the diameter in inches; n, the revolutions per minute;, 
 and Q, the number of cubic feet per minute. He also gives for 
 the Blackman fan (which has a blade constructed with a peculiar 
 curve) : 
 
 Q = d 3 n -r- 1,880. 
 
 Prof. Kinealy states that the proper velocity for a fan is given by 
 the formula 
 
 n = 21,000 -a- d, 
 
 where d is again the diameter in inches. The formula is based! 
 on a velocity at the rim of 90 feet per second. Prof. KinealyV. 
 formula for the Blackman fan corresponds quite closely with the> 
 figures given in Mr. Wolff's table, and may undoubtedly be ac- 
 cepted as reliable for free delivery. If the disk fan is used on a 
 complicated system of ducts the author would favor multiplying 
 Prof. Kinealy's formulas by a coefficient of 0.65; and if heating 
 
130 STEAM HEATING AND VENTILATION. 
 
 coils and other similar resistances are added, this coefficient should 
 be made not greater than 0.5. 
 
 Ventilation ~by gravity. There is one method of creating a cir- 
 culation of air which may properly be discussed in connection 
 with other apparatus for the purpose, and which is frequently 
 of great value. This is the heated flue. In Chapter IV the au- 
 thor discussed the effect produced by heating the column of air 
 in an open flue, and the formula 
 
 was derived for the theoretical velocity in feet per second (with- 
 out friction) obtained in the flue, where T is the temperature to 
 which the air in the duct is heated, and t is external temperature, 
 H being the height of the flue, and g the acceleration of gravity 
 = 32.2. 
 
 Mr. Alfred R. "Wolff is of the opinion that 50 per cent, must 
 be deducted from the formula for friction of air in ducts, etc., in 
 order to get the actual velocity that can be attained, and he re- 
 duces the formula to the following* form : 
 
 V = 
 
 (T - t) 
 
 492 
 
 in which V is the velocity in feet per minute. Mr. Wolff also gives 
 the following table calculated from this formula : 
 
 TABLE IV. VELOCITY OF AIR, IN FEET PER MINUTE, THROUGH A 
 
 VENTILATING DUCT (THE EXTERNAL TEMPERATURE 
 
 OF THE AIR BEING 32 DEGREES FAHR. 
 
 Excess of Temperature of Air in Vent Duct Above 
 
 Height of Vent- 
 Duct in ft. 5 
 10 77 
 
 that of External Air, 
 10 15 20 25 
 108 133 153 171 
 133 162 188 210 
 153 188 217 242 
 171 210 242 271 
 188 230 265 297 
 203 248 286 320 
 217 265 306 342 
 230 282 325 363 
 242 297 342 383 
 
 Degrees Fahr. 
 30 50 100 
 188 242 342 
 230 297 419 
 265 342 484 
 297 383 541 
 325 419 593 
 351 453 640 
 375 484 656 
 398 514 726 
 419 541 766 
 
 150 
 419 
 514 
 593 
 663 
 726 
 784 
 838 
 889 
 937 
 
 15 
 
 94 
 
 20 
 
 108 
 
 25 
 
 121 
 
 30 
 
 133 
 
 35 
 
 143 
 
 40 
 
 153 
 
 45 
 
 162 
 
 50.. 
 
 171 
 
 It will be seen from this table that the velocities obtained are 
 small, and as V is proportional to the square root of (T t) and 
 also to the square root of H, it is necessary to multiply one of 
 these factors by four in order to double the velocity. It is, there- 
 
STEAM HEATING AND TENTILATiON. 
 
 131 
 
 fore, necessary to have a very considerable difference in tempera- 
 ture, or a great height of flue, or a large area, in order to produce 
 the volume of flow that would be required in a moderate ventil- 
 ating plant. The cost of heating a large volume of air to the 
 required temperature is excessive in comparison with the cost of 
 fan power. 
 
 There are many special cases, such as the ventilation of the 
 toilet rooms, where continual circulation is desired, and especially 
 where cheap gas is available, in which the heated flue is a valuable 
 means to be employed. In many cases a vent shaft can convenient- 
 ly be located around a metal chimney, from which sufficient heat 
 is obtained to produce a decided draft. 
 
 Figure 76. A Type of Heating Coil. 
 
 Heating coils. In the latitudes of most of the United States 
 it is necessary to provide heating coils for all fans which take air 
 from the outside and blow it into buildings for ventilating pur- 
 poses. These coils are of many kinds and forms. They are usually 
 located either between the air intake and the fan, or just at the 
 outlet of the fan, but frequently separate coils are placed at the 
 base of the vertical flues to each room; and often, indeed, a tem- 
 porary coil for use in very cold weather is placed at the fan and 
 additional ones at the separate vertical flues. Figure 76 shows one 
 form of heating coil for a fan, the casing being removed. Figures 
 
132 STEAM HEATING AND VENTILATION. 
 
 77 and 78 show fan and coil together, in the former the heater 
 being on the suction side, and in the latter on the blast side. 
 
 The heating coils are generally made of loops of 1-inch pipe, 
 and the rules for proportioning them are very conflicting. The 
 same general theories apply to them as to indirect radiators, as 
 given in a preceding chapter of this series. 
 
 In a brief article in the issue of May 13, 1899, The Engineering 
 Eecord gives some valuable data from the authorship of Mr. W. S. 
 Blessed of the American Blower Company. The data refers to> 
 coils similar to that shown in Figure 76, each section of which con- 
 tains four rows of 1-inch pipes set 2f inches center to center, and 
 give the final temperature attained by the air under different 
 "mean velocities" through the coil. With air at an initial "tem- 
 perature of 30 degrees Fahr. passing through the coils at a mean 
 velocity of 1,600 feet per minute, a common velocity with a cen- 
 trifugal fan, the air will be raised to the temperature shown in 
 the following table, with the steam pressures and number of coils, 
 in use as mentioned : 
 
 Steam, 5 Ibs. Pressure. Steam, 75 Ibs. Pressure. 
 
 Final Temp. Final Temp. 
 
 Number of Air. Number of Air. 
 
 of Sections. Deg. Fahr. of Sections. Deg. Fahr. 
 
 4 74 4 92 
 
 5 88 5 117 
 
 6 100 6 137 
 
 7 110 7 143 
 
 8 117 8 156 
 
 "With a mean velocity of air of 900 feet per minute the rise in 
 temperature of the air will be : 
 
 Steam, 5 Ibs. Pressure. Steam, 75 Ibs. Pressure. 
 
 Final Temp. Final Temp. 
 
 Number of Air. Number of Air. 
 
 of Sections. Deg. Fahr. of Sections. Deg. Fahr. 
 
 4 85 4 125 
 
 5 110 5 158 
 
 6 130 6 186 
 
 7 147 7 210 
 
 8 160 8 230 \ , 
 
 "With 5 pounds pressure about 1,720 B. T. U. are given off per 
 hour per square foot of heating surface, and with 70 pounds press- 
 ure about 2,520 B. T. U." 
 
 Commenting further on this subject, in response to an inquiry, 
 The Engineering Eecord of June 3, 1899, says: 
 
 "It may be well to describe how the manufacturers of this ap- 
 
STEAM HEATING AND VENTILATION. 
 
 133 
 
 paratus usually determine the size of hot-blast coils necessary to 
 do a certain amount of work. It is manifest that the amount of 
 heat which can be transferred from one substance to another, as 
 from the steam-heated pipes of a hot-blast coil to the air which 
 is being blown past them, is proportional, in a measure, to the time 
 that the air is subject to the heating influence of the steam pipes. 
 Consequently, hot-blast coils must be large enough in a plane 
 perpendicular to the direction of the moving air; or, in other words, 
 
 Figure 77. Heater on Suction Side. 
 
 Exhaust. ', i Live Steam 
 
 Figure 78. Heater on Blast Side. 
 
 they must be a sufficient number of pipes wide, and the pipes must 
 be of such a length that the combined area of the openings be- 
 tween the pipes will be sufficient in size to insure the proper veloc- 
 ity of the air to be forced through them. 
 
 "For instance, if the mean velocity of air through the coils is to 
 be 1,600 feet per minute, which is not an uncommon one with cen- 
 trifugal blowers, and it is desired to put 16,000 cubic feet of air 
 j)er minute through the coils, the area of the openings between the 
 
134 
 
 STEAM HEATING AND VENTILATION. 
 
 pipes should be 16,000 -4- 1,600 = 10 square feet. Makers of hot- 
 blast coils know the area of the openings between the pipes of 
 coils of various sizes, and select the size which will give them the 
 clear opening needed. With the data given in the note referred 
 to, it is possible to calculate the rise in temperature of the air 
 which will occur with various rows of pipes and with steam of 5 
 and 75 pounds pressure. 
 
 "The mean velocity of air should be explained. If 16,000 cubic 
 feet of air at a temperature of say 120 degrees are to pass through 
 the registers of a ventilating plant in a minute, this air, when at 
 zero degrees, will have a volume of about 12,800 cubic feet. Con- 
 sequently, as the air expands as it is heated in passing through the 
 
 200 
 190 
 .180 
 
 >I50 
 1 130 
 
 "!oo 
 
 I 90 
 
 O Of) 
 
 tn 80 
 70 
 60 
 50 
 
 100 300 500 700 900 1100 BOO 1500 1700 
 
 Velocity of Air passing over Heater Coils 
 
 Figure 79. Influence of Velocity of Air in Heaters. 
 
 coils, its velocity must increase, and its mean velocity is the one 
 upon which most calculations are based. If the 12,800 cubic 
 feet is expanded to 16,000 cubic feet its mean volume is (12,800 
 + 16,000) -f- 2 = 14,400 cubic feet. Then 14,400 ~ 1,600 (the 
 mean velocity assumed) = 9 square feet, the area of the clear 
 opening between the coils that would be needed." 
 
 Mr. Walter B. Snow, of the B. F. Sturtevant Company, in a 
 lecture delivered before various technical colleges, gives some dia- 
 grams which, taken in connection with the data given above, are 
 of great value in proportioning heatinsr coils. These diagrams 
 give only the relative effects of varvinor velocities through the free 
 area of the coils, as well as the relative effect of different depths. 
 of coils. The diagrams are given in Figures 79 and 80, and aa 
 
STEAM HEATING AND VENTILATION. 
 
 135 
 
 quoted from The Engineering Record of April 21, 1900, Mr, Snow 
 gives the following explanation: 
 
 "The effect of varying velocities* and of different steam press- 
 ures is shown in the accompanying curves drawn from the results 
 of tests of Sturtevant heaters used in connection with fans. The 
 relative condensation increases with both of these factors, but, 
 as indicated by the third curve, the relative temperature increment 
 with a given steam pressure decreases with the velocity. This is 
 the natural result of moving a larger volume of air across the 
 heating surface, and decreasing the time of contact. Disregard- 
 ing the expansion by heat, the volume is proportional to the ve- 
 
 150 
 
 140 
 130 
 #120 
 
 60 
 
 > 
 I 50 
 
 2 <o 10 14 18 22 26 30 34 58 
 Depth of Heater - Rows 
 
 Mt Cftcmtoww *tOO*fr 
 
 Figure 80. Influence of Depth in Heaters. 
 
 locity; therefore the relative heat transmission may be determined 
 by multiplying the given velocity by the relative condensation. 
 
 "The rate of condensation is naturally dependent upon the tem- 
 perature difference "between the air and steam, anc* is therefore 
 greatest with the maximum difference. Hence, the less the depth 
 of the heater, the less the total temperature increment of the air, 
 but the more rapid the rate of transmission from steam to air. 
 With increasing depth of heater there is a corresponding decrease 
 in the average condensation per square foot. The surface first 
 exposed to the air, of course, continues to maintain the same 
 efficiency, but the surfaces subsequently passed over are progres- 
 sively exposed to smaller and smaller temperature differences. 
 
 "The exact conditions in a Sturtevant heater operated in con- 
 
 OFTME 
 
136 STEAM HEATING AND VENTILATION. 
 
 nection with a fan which produces a mean air-velocity flow of 
 1,200 feet per minute through the free area of the "heater, are 
 presented in the accompanying curves. From these and the pre- 
 ceding curves it is evident that the greatest surface efficiency is 
 secured with the highest velocity of air and the least depth of 
 heater. Practically, however, it is necessary to limit the velocity 
 of the air, and to make the heater of sufficient depth to give the 
 required temperature increment to the air." 
 
 Heating coils should always be provided with a by-pass around 
 the coil, with a damper that can be opened in warm weather, when 
 the heating coil is not in use; and also in moderate weather, to 
 regulate the temperature of the entering air. 
 
 Heating coils, although an absolute necessity, in almost every 
 case form a resistance to the movement of air which invariably 
 reduces the output of the fan ; and few, even among those familiar 
 with ventilating plants, realize the full 'extent of the resistance 
 offered by such coils. The author, in a paper in the "Transac- 
 tions" of the American Society of Heating & Ventilating Engi- 
 neers, for 1899 (Vol. V, p. 117), presented some tests made on 
 g'ome large fans in the Chicago Public Library. In the accom- 
 panying tables, V and VI, are given the principal results of the 
 tests: 
 
 TABLE V. Test of Fan E. Diam. wheel, 78 inches; width of blade, 45 inches; 
 diam. inlet, 54 inches; net area, 13.1 sq. ft. Main duct, 45x45 inches; area, 
 14.1 sq. ft. Gross area heating coil, 34.7 sq. ft. ; surface, 7,200 sq. ft. 
 
 a* Pressure of Air Velocity of Air. "cs ft^ 
 
 in oz. per sq. in. Ft. per min. ft M S z 
 
 *-l flj . O> O 
 
 m 
 
 a>S "'J3 
 
 O o * 
 
 g Q a> o. 
 
 ll I I -I I dl * I- 
 
 PH w H gU fc < 
 
 By-pass Open. 
 
 102 
 
 110 .144 
 
 137 
 
 152 .259 
 
 157 
 
 .086 
 
 .173 
 
 1,230 
 
 .... 
 
 
 
 6.2 
 
 65 
 
 .086 
 
 .230 
 
 1,430 
 
 1,330 
 
 18,700 
 
 8.6 
 
 65 
 
 .115 
 
 .302 
 
 1,700 
 
 1,580 
 
 22,300 
 
 13 
 
 65 
 
 .144 
 
 .403 
 
 1,870 
 
 1,740 
 
 24,500 
 
 17.3 
 
 65 
 
 .144 
 
 .403 
 
 1,920 
 
 1,780 
 
 25,100 
 
 20.6 
 
 65 
 
 By-pass Closed. 
 
 77 
 
 .151 
 
 .029 
 
 .180 
 
 621 
 
 580 
 
 8,180 
 
 2.9 
 
 65 
 
 77 
 
 .165 
 
 .007 
 
 .172 
 
 650 
 
 605 
 
 9,500 
 
 3 
 
 130 
 
 77 
 
 +.180 
 
 .015 
 
 .165 
 
 690 
 
 640 
 
 9,010 
 
 '2.9 
 
 160 
 
 144 
 
 
 .072 
 
 .310 
 
 1,120 
 
 1,040 
 
 14,650 
 
 12 
 
 65 
 
 164 
 
 .334 
 
 .086 
 
 .420 
 
 1,420 
 
 1,320 
 
 18,670 
 
 19.2 
 
 65 
 
STEAM HEATING AND VENTILATION. 
 
 TABLE VI. Test of Fan F. Diam. wheel, 78 inches; width blades, 45 
 diam. inlet, 54 inches; net area, 13.1 sq. ft. Main duct, 45x45 inches 
 14.1 sq. ft. Gross area heating coil, 40 sq. ft.; surface, 7,200 sq. ft. 
 
 pj Pressure of Air Velocity of Air. 
 in oz. per sq. in. Ft. per min. a 
 
 fe 
 
 A a a d 
 
 Is f 1 ; 1 i 1 di 
 
 S H ~ 3 
 
 137 
 
 inches.; 
 ; area, 
 
 <3 -*j 
 
 1 
 
 By-pass Open. 
 
 (No steam on coil.) 
 
 73 
 
 .040 
 
 .026 
 
 .065 
 
 788 
 
 730 
 
 10,320 
 
 . . . 
 
 86 
 
 .054 
 
 .032 
 
 .086 
 
 945 
 
 830 
 
 12,380 
 
 3.36 
 
 100 
 
 .068 
 
 .040 
 
 .108 
 
 1," Q 3 
 
 1,020 
 
 14,320 
 
 5.16 
 
 114 
 
 .123 
 
 .053 
 
 .176 
 
 1,240 
 
 1,150 
 
 16,250 
 
 7.11 
 
 123 
 
 ... 
 
 .061 
 
 
 I,o50 
 
 1,255 
 
 17,680 
 
 8.88 
 
 139 
 
 ... 
 
 .075 
 
 
 1,520 
 
 1,415 
 
 19,900 
 
 12.1 
 
 143 
 
 ... 
 
 .075 
 
 ... 
 
 1,580 
 
 1,470 
 
 20,650 
 
 13.5 
 
 
 
 By-pass 
 
 Closed. 
 
 (No steam 
 
 on coil.) 
 
 
 
 76 
 
 .071 
 
 , .011 
 
 .072 
 
 554 
 
 
 
 7,260 
 
 3.05 
 
 141 
 
 
 .043 
 
 .257 
 
 1,075 
 
 .... 
 
 14,080 
 
 11. 
 
 A comparison is also given between the air deliveries and power 
 required'f or both open and closed by-pass in Table VII. It should 
 l)e noted here that the values in columns (2), (3), (5) and (6) were 
 obtained from Tables V and VI, but in some cases by interpola- 
 
 TABLE VII. EFFECT ON AIR DELIVERY AND POWER OF CLOSING 
 
 BY-PASS. 
 
 (1) 
 
 (2) 
 
 (3) 
 
 (4) 
 
 (5) 
 
 (6) 
 
 (7) (8) 
 
 (9) 
 
 (10) 
 
 * 
 
 02 
 
 1 
 
 y - t 
 
 1 
 
 i 
 
 f-4 -t ** * 
 
 
 " 03 
 
 d 
 
 fl ! | 
 
 .a 1 * 
 
 5 
 
 Pi 
 
 g 
 
 
 p, ^co 
 
 
 a, 
 
 ' 
 
 A 
 
 
 
 
 a 
 
 w 
 
 '*"' g< 
 
 
 '"'do? 
 
 m 
 
 fs 
 
 C-2 
 
 C<1 
 
 -1 
 
 o 
 
 ^ o 
 
 S g5g 
 
 00 
 
 g - 
 
 
 "c3 pi 
 
 to 
 
 ^"^ 
 
 fl 02 
 
 02 
 
 V 'jj t* o. 
 
 1 
 
 4 ' Q 
 
 JH 
 
 
 % 
 
 [ fl 
 
 C^ 02 
 
 
 |> d i5 i 
 
 .j. 
 
 ^> ^ 
 
 O!M 
 
 ^ o 
 
 . CO 
 
 3 P. 
 
 a 
 
 h p, 
 
 Pi 
 
 OJ ^ GJ >> 
 
 ^s a > B 
 
 
 fa Q 'w 
 
 <3 
 
 > ' 
 
 > 
 
 $3 
 
 O 
 
 o 
 
 ^ <5 
 
 2- 
 
 
 
 
 
 
 Fan 
 
 E. 
 
 
 
 
 77 
 
 935 
 
 621 
 
 66.3 
 
 3.2 
 
 2.9 
 
 91. 
 
 ... 
 
 65 
 
 77 
 
 935 
 
 650 
 
 69.5 
 
 3.2 
 
 3.0 
 
 94. 
 
 ... 
 
 130 
 
 77 
 
 935 
 
 690 
 
 74.0 
 
 3.2 
 
 2.9 
 
 91. 
 
 
 160 
 
 144 
 
 1,800 
 
 1,120 
 
 64.0 
 
 15.5 
 
 12.0 
 
 77.5 4.9 
 
 2.44 
 
 70 
 
 164 
 
 2,050 
 
 1,420 
 
 69.1 
 
 23.8 
 
 19.2 
 
 80.6 8.4 
 
 2.3 
 
 70 
 
 
 
 
 
 Fan' 
 
 F. 
 
 
 
 
 76 
 
 850 
 
 554 
 
 65.1 
 
 2.9 
 
 
 
 
 
 141 
 
 1,550 
 
 1,075 
 
 69.0 
 
 12.5 
 
 11.0 
 
 88.0 4.7 
 
 2.35 
 
 70 
 
 tion, so as to obtain for comparison the values corresponding to 
 the same number of revolutions per minute of the fan for open 
 and closed by-pass. 
 
138 
 
 STEAM HEATING AND VENTILATION. 
 
STEAM HEATING AND VENTILATION. 
 
 13$ 
 
 The following comments on the results of these tests were made, 
 and they have a valuable bearing on practical installations : 
 
 "It will be seen that the air delivery was decreased from 21 
 
 Scale 
 o/ i' r ?' * 
 
 Figure 82. Elevations of the Hot-Blast Unit. 
 
 to 36 per cent, merely by closing the by-pass. Two tests on fan 
 E, with part of the heater turned on, and a high temperature 
 through the fan, gave a somewhat less reduction. But even with 
 the by-pass closed, and as high a temperature as 160 degrees, the 
 
140 STEAM HEATING AND VENTILATION. 
 
 delivery was 20 per cent, less than with the by-pass open. The 
 only tests at these high temperatures were made with very low 
 fan speeds, and the test of 160 degrees showed a negative pressure 
 on the blast side of the fan, due to the draft of the hot air in the 
 vertical ducts. The author regrets that it was impossible to repeat 
 these temperature tests at higher fan speeds, but they do not have 
 much bearing on practical results, as temperature in air ducts of 
 much over 100 degrees would not be good practice anywhere. It 
 will be noted also that whereas the delivery of air is reduced about 
 24 per cent, by closing the by-pass, the power required (for same 
 speed of fan) is reduced only from 9 to 22 per cent., while it will 
 be seen that for equal air deliveries the power was increased from 
 2.3 to 2.44 times by closing the by-pass. 
 
 "Attention should also be called at this point to the fact, as 
 shown by the pressure observations in Tables V and VI, that even 
 with the by-pass wide open the resistance due to intake and pas- 
 sages through and around the heater or, in other words, the 
 total resistance on the inlet of the fans was in all cases quite 
 considerably more than the total resistance of the delivery ducts, 
 dampers and registers. This was a matter of considerable sur- 
 prise, as the intake seemed to be of ample size, and area of the 
 by-pass large. It was probably due, however, to the height of 
 intake [about 40 feet], and as such resistances are very often but 
 little considered, it will be valuable to note their importance in 
 this case." 
 
 In regard to the fan capacities obtained by these tests it will 
 be interesting to note that those on fan E, with by-pass open, cor- 
 respond very closely with those given by Mr. Huyett's table, and 
 also correspond with Prof. Carpenter's formula (Q = end 3 ) using a 
 coefficient c = 0.57, while with by-pass closed the coefficient for 
 Prof. Carpenter's formula is c = 0.43. The velocities in the de- 
 livery duct, however, even the highest attained, were rather low, 
 the maximum being about 30 feet per second (1,780 per minute), 
 which would indicate a very free delivery. 
 
 Arrangement of heating coils in air ducts. The possible arrange- 
 ments of heating coils in ducts are limitless, but thoroughly sat- 
 isfactory ones, which operate with perfect success in all kinds of 
 weather, are by no means easy to obtain. Figure 81 shows the 
 arrangement of air ducts, fan and heating coils adopted for a 
 schoolhouse in a large city, and Figures 82 and 83 show a detail 
 
STEAM HEATING AND VENTILATION. 
 
 141 
 
 of the arrangement of fan and heaters. It will be seen that there 
 is a separate duct for each room in the building, each emanating 
 from the central distributing point, and each provided with a 
 mixing damper. 
 
 Front Elevation of Heater 
 Showing SteamGonnections. 
 
 ciHNO RECORD. 
 
 flush. 
 
 Airim.i 
 
 Fresh Air Met.**, 
 
 Figure 83. Plan of One of the Hot-Blast Units. 
 
 The system shown is a good example of a method sometimes 
 used to distribute air through long ducts of small size. The 
 author believes, however, that it is open to criticism, as the large 
 number of long, small ducts cannot fail to greatly increase the 
 
142 
 
 STEAM BEATING AND VENTILATION. 
 
 frictional resistance to the flow of air, thus either diminishing 
 the fan capacity or, for a given capacity, greatly increasing the 
 power required to run the fan. Besides this, the air in the ducts 
 opposite the center of the fan will unquestionably have a higher 
 velocity than those at the sides. It would have been much bet- 
 ter to locate centers of distribution convenient to the vertical 
 ducts at each end of the building and at each bicycle room, and 
 
 Figure 84, 
 
 Figure 85. 
 
 locate the heating coils with mixing dampers at these points with 
 "feeder" ducts (underground, perhaps) from the fans to the cen- 
 ters of distribution. 
 
 In this connection it is well to state that it is not advisable to 
 run heated air through underground ducts, for the reason that 
 they rapidly absorb heat in cold weather. Where mixing dampers 
 are employed, however, with coils located at a distance from the 
 fan, it is not generally necessary to temper the air with a coil at 
 
STEAM HEATING AND VENTILATION. 
 
 143 
 
 the fan; but all the required heating surface can be placed at the 
 centers of distribution. 
 
 Mixing Dampers. There are innumerable arrangements for 
 constructing mixing dampers, the idea being to provide a cold-air 
 and a hot-air connection to the vertical flue to each room,, the 
 temperature of the air to the room being regulated by the posi- 
 tion of the mixing damper. They usually consist of a double 
 damper, one in the cold-air connection and one in the hot-air 
 connection, fastened together so that when one is entirely closed 
 the other is entirely open, and vice versa. Three types of mixing 
 dampers, selected at random, are shown in Figures 84, 85 and 86. 
 
 Thermostats. Mixing dampers are frequently arranged to be 
 operated by automatic thermostats, which regulate their position 
 
 Room. 
 
 Figure 86. 
 
 by the temperature of the room being heated. The principal diffi- 
 culty is that they frequently throw the dampers to the extreme 
 "cold-air position" when the temperature rises, and to the extreme 
 "hot-air position" when it falls again. It is very difficult to obtain 
 a thermostat which will move a mixing damper gradually through 
 its arc by means of a small range of temperature at the thermo- 
 stat, and this is the most important requirement. 
 
 Air purification.- There is much auxiliary apparatus employed 
 in ventilating systems besides the heating coils, and among these 
 may be mentioned especially means for cleaning and purifying the 
 air. In our large cities, especially for hospitals, something of this 
 kind is very essential. The air is frequently blown through loose 
 cloth screens. The most effective way of cleaning the air, how- 
 ever, is to blow it through a spray of water or through wire screens 
 
144 
 
 STEAM HEATING AND VENTILATION. 
 
 over which water is kept running, or over shallow trays of water. 
 Care must be taken to provide against the annoyance due to freez- 
 ing, and the formation of icicles in winter. In summer the water 
 will lower the temperature of the air somewhat,, but the danger 
 from the washing process lies in making the air too damp. 
 
 Mr. K. H. Thomas, of Chicago, a ventilating contractor of wide 
 
 THE ENGINEERING I 
 
 Figure 87. Plan of Air- Washing Apparatus. 
 
 experience, has recently patented a dirt "eliminator," represented 
 in the accompanying cuts, Figures 87 and 88, which has proved 
 very effective in severa, -^e ventilating plants. The air is blown 
 through a special form o .pray and the eliminator proper collects 
 the dirt and removes the excess of moisture from the air. 
 
 Air cooling. Trays of ice are sometimes used, and refrigerating 
 coils also, for cooling the air in summer for theaters ; but this is a 
 
STEAM HEATING AND VENTILATION. 
 
 145 
 
 luxury which has not as yet been employed to a large extent. It 
 must always be remembered that any apparatus of the kind de- 
 scribed will add to the resistance through which the fan has to 
 force its air, and will therefore lessen its capacity, or must be 
 made up by increased speed and power. 
 
 Figure 88. The Eliminator of the Air-Washing Apparatus. 
 
 Measuring air currents. Before closing a chapter on the ap- 
 paratus of ventilating systems it seems necessary to say a few 
 words about the instrument most always used for testing pur- 
 poses. It is not the author's intention to treat of the many 
 
 Figure 89. The Anemometer. 
 
 methods to be employed in testing ve* iting apparatus for dif- 
 ferent objects, but the anemometer, w>. >-h is used to measure air 
 velocities, is so generally employed, and so necessary in inspect- 
 ing plants, that a brief description seems advisable. There are 
 many forms, but they all consist of a set of vanes attached to a 
 
146 STEAM HEATING AND VENTILATION. 
 
 revolving shaft like a small windmill or disk fan and a registering 
 device as shown in Figure 89. They are rarely accurate, and 
 should not be used ^ without being calibrated. This is usually ac- 
 complished by attaching the instrument to the end of a stick about 
 8 or 10 feet long, and revolving in a circle at different uni- 
 form speeds in still air and plotting a diagram showing the rela- 
 tion between the actual velocities and the reading of the instru- 
 ment. This will give data for correcting the indications of the 
 instrument obtained during a test, 
 
INDEX. 
 
 Adams, Henry Boilers 
 
 Form of direct-indirect radiator Cast-iron, 
 
 setting t-5 Capacities of 32 
 
 Air Types of 31 
 
 Action of, in radiators.... 18, 20, 56 Brick, Heat losses through.... 62, 64 
 
 Amount of, required for individ- Bronzing, Radiator 46 
 
 uals under different conditions 99 Butler, W. F. 
 
 Circulation Handbook on ventilation 7 
 
 Around radiators 43 
 
 In rooms 96, 110 Carbonic-acid gas 
 
 Cooling of 144 Amount given oil by individuals S9 
 
 Flow of Relation of, to purity of air 97 
 
 In ducts , 113 Carpenter, Prof. R. C. 
 
 In heated ventilating flue 130 Centrifugal fan capacities 127 
 
 Through indirect radiators 50 Coefficients of heat transmission 
 
 Leakage into buildings 60 of building substances 62 
 
 Pressures of, in ventilating sys- Power to drive centrifugal fans.. 128 
 
 terns 115 Radiator tests 39 
 
 Purification of 143 Rule for direct radiation 67 
 
 Purity, standards of 97 Rule for steam pipe sizes 76 
 
 Specific heat and weight of.... 61 Tests of effect of paint on radi- 
 
 Velocities of ator 4G 
 
 In ducts 116 Condensation 
 
 Measurement of 145 Coefficient of radiator 43 
 
 Through inlets and outlets 112 Indirect radiators 
 
 Volumes required for different Tests of 51. 
 
 buildings and different periods Curves of, in 54 
 
 of occupancy 100 Relative, in radiators at differ- 
 
 Air inlets ent steam pressures 45 
 
 Diffusers for, Cooley, Prof. M. E. 
 
 Theaters 108 Tests of wrought-iron pipe coils 45 
 
 Upward svstem of ventilation 106 Cooling, Air 144 
 
 Indirect radiators 91 
 
 Proper arrangement of J09 Dampers 
 
 Velocities through 112 Mixing 143 
 
 Air outlets Use of, in air ducts 117 
 
 Proper location of 109 Denton & Jacobus, Profs. 
 
 Velocities through 112 Radiator tests 43 
 
 Air valves, see Valves. Tests of extension-surface radi- 
 
 Anchors, riser 85 ators 45 
 
 Anemometer 145 Desaguliers. Dr. 
 
 System of ventilation 8 
 
 Baldwin, William J. Diffusers 
 
 Heat-transmitting power of For theaters 108 
 
 building substances 62 For U. S. Senate chamber 306 
 
 Rule for direct radiation 63 Drainage of pipes 78 
 
 Rule for pipe sizes 72 Ducts 
 
 Tests of indirect radiators El Arrangement of 
 
 Tests of radiator condensation For indirect radiator installa- 
 
 at different pressures 45 tions 92 
 
 Billings, Dr. John S. Schemes for 117 
 
 T,eakaere of air into buildings... CO Branch 116 
 
 Blessed, W. S. Brick underground 122 
 
 .tieat given off by heating coils 132 Flow of air in .113 
 
INDEX. 
 
 Layout of, in the basement of a Hcod, Charles 
 
 large building 119 Coefficient of heat transmission 
 
 Materials tor 121 through glass 62 
 
 Underground 94 Huyett, M. C. 
 
 Expansion Centrifugal fan capacities 125 
 
 Method of providing for, in pipes 79 
 
 Kn nSi n J intS - 81 Jacobus & Denton, Profs. 
 
 JH.XpOSUre Rurlintnr t^etc At 
 
 Influence of, in determining ra- TeStsof extension-surface -radl 
 diatlon 63, b5 iators 45 
 
 Blackman Kinealy, Prof. J. H. 
 
 Capacity of 129 Capacities of disk fans 129 
 
 Centrifugal Sizes of flues for indirect radia- 
 
 Capacity of 125 tors ?1 
 
 Capacities, of, compared by dif- 
 ferent formulas 140 Mills, J. H. 
 
 Description of 124 Rule for direct radiation 66 
 
 Power to drive 127 Rule for pipe sizes 73 
 
 Combined unit of heater and.... 133 System of piping 16 
 
 Disk Tests of indirect radiators 51 
 
 Capacities of 129 Mills' system of piping 16 
 
 Description of 125 Monroe, William S. 
 
 Tests of, with heating coils 136 Radiator tests 40 
 
 Filters for air purification 143 Rule for direct radiation 8 
 
 Flues Rule for pipe sizes 73 
 
 For indirect radiator installa- Tests of fans and heating coils.. 136 
 
 tions DO Muffler tank in an office building 
 
 Heated, velocity in the 130 power plant 89 
 
 Several outlets from same 121 
 
 Friction Paints, Effect of, on radiation 46 
 
 In steam pipes 77 Parkes. Individual exhalation of 
 
 See under Ducts, etc. carbonic-acid gas 99 
 
 Paul vacuum system of steam 
 
 Glass, Window heating 28 
 
 Heat losses through 62, 64 Pettenkofer, Individual exhalation 
 
 Governors, Pump of carbonic-acid gas 99 
 
 On closed and open heaters.. 23, 26 Plenum chambers in duct sys- 
 
 Gray, Dr., Tests of indirect radia- terns 117 
 
 tors 51 Pressures 
 
 Air, in ventilating systems 115 
 
 Hangers Heating at high 19 
 
 Indirect radiator supports 91 Pumps 
 
 Pipe, expansion 87 Automatic for return water 27 
 
 Heat Vacuum 29 
 
 Amount given off by direct rad- Pipes 
 
 iators 43 Drainage of 17 
 
 Amount given off by indirect Expansion of 7& 
 
 radiators 50, 51, 70 Protection of 86 
 
 Loss in buildings 60 Supports for 6 
 
 Required for ventilation 61 Pipe covering 
 
 Heaters, Feed-water Values of different kinds of... 90 
 
 Location of, in an office building Pipe sizes 
 
 plant 89 Baldwin's rule 72 
 
 Open and closed or pressure Carpenter & Sickles' rule for 76 
 
 types 22, 23 For high-pressure systems r .5 
 
 Value of 22 For vacuum systems 75 
 
 Heating, Steam Mills' rule for ' 73 
 
 Earliest instance 7 Monroe's rule for 73 
 
 Exhaust Radiator connections 76 
 
 Arrangement of 21, 23 Pipe systems 
 
 Considerations of 19 One-pipe 
 
 Gravity IS Arrangement of mains for 78 
 
 High pressure 19 Overhead or Mills' .'.. 36 
 
 Vacuum .-.. 28 Simple type 13 
 
 Heating coils Sizes of radiator connections 
 
 Arrangement in air ducts 140 to 76 
 
 Capacity of 132 With separate return main.... 15 
 
 For use with fans 131 Overhead system 
 
 Influence of depth of 135 Description of large 83 
 
 Tests of, with fans 136 Two-pipe 
 
 Velocity of air through 132, 134 Arrangement of mains for 78 
 
 Hogan, John J, Overh'ead 17 
 
 Coefficient of heat transmission Simple type 34 
 
 through glass... ^ 62 Sizes of radiator connections. . 76 
 
INDEX. 
 
 Piping 
 
 Arrangement of main in an of- 
 fice building power plant 8? 
 
 Connections to feed-water heat- 
 ers 23 
 
 For indirect radiator installa- 
 tions 
 
 Heating coil connections 131, 141 
 
 Radiant heat, amount of, from va- 
 rious types of radiators 38 
 
 Radiation 
 Boiler capacity for required 
 
 amount of 32 
 
 Calculation of 85 
 
 Direct 
 
 Adaptation of 10 
 
 Baldwin's rule for C3 
 
 Carpenter's rule for 67 
 
 Mills' rule for 66 
 
 Monroe's rule for 68 
 
 Willett's rule for 66 
 
 Wolff's rule for 69 
 
 Direct-indirect 
 
 Adaptation of 11 
 
 Rule for 71 
 
 Indirect 
 
 Adaptation of 10 
 
 Rule for 70 
 
 Raaiant heat from 38 
 
 Radiators 
 
 Action of 36 
 
 Air circulation in hot-water and 
 
 steam types E6 
 
 Circulation of 18, 55 
 
 Classification according to sur- 
 face 34 
 
 Connections 
 
 One and two-pipe 58 
 
 Riser 79 
 
 Sizes of 76 
 
 Direct, circulation in , 57 
 
 Direct-indirect 
 
 Action of.. 54 
 
 Settings, type of 94 
 
 Types of 35 
 
 Extension-surface, tests of 45 
 
 Flue 
 
 Compared with open 45 
 
 Types of 33 
 
 Gold's pin 58 
 
 Hot-water 
 
 Compared with steam 45 
 
 Types of 34, 37 
 
 Indirect 
 
 Circulation in 58 
 
 Heating residences by 92 
 
 Theory of 48 
 
 Types of 36 
 
 Location of 46 
 
 Measuring 34 
 
 Narrow and wide compared with 
 
 high and low.....' 44, 45 
 
 One, two and three-column types 32 
 
 Painting of 46 
 
 Protection of connections to 86 
 
 Tests of 38 
 
 Water in 79 
 
 Wrought-imn 33 
 
 Reed, J. R. Tests of indirect rad- 
 iators 51 
 
 Registers 
 
 Velocity of air through 116 
 
 Return mains. Location of 78 
 
 Richards. C. B. Tests of indirect 
 
 radiators 51 
 
 Risers 
 
 Anchors for 85 
 
 Concealment in columns 81 
 
 Connections of, to mains 78 
 
 Location of 83 
 
 Sickles, E. C. Rule for steam 
 
 pipe sizes 76 
 
 Sleeves, Floor 86 
 
 Snow, Walter B. 
 Influence of velocity of air in 
 heaters and of the depth of 
 
 heaters 134 
 
 Steam 
 
 Flow of, in pipes 72, 76 
 
 Proportion of heat energy avail- 
 able for heating 19 
 
 Supports 
 Indirect radiator 91 
 
 Tables 
 
 Air velocities at different duct 
 pressures; Chap, ix 115 
 
 Amount of air per person in 
 buildings of various kinds; Ta- 
 ble 2, Chap, vii 101 
 
 Capacity of heating coils; Chap. 
 x 132 
 
 Capacity of steam pipes; Table 
 v, Chap, vi 77 
 
 Carbonic-acid gas exhalation; 
 Chap, vii 99 
 
 Cast-iron boiler capacities; 
 Chap. iii... 32 
 
 Centrifugal fan-wheel capacity 
 coefficients; Table ii, Chap. x. 126 
 
 Condensation in radiators at dif- 
 ferent pressures; Chap, iii 45 
 
 Effect of by-pass on air deliv- 
 ery and power; Table vii, Chap. 
 x 137 
 
 Fan and heating-coil tests; Ta- 
 bles v and vi, Chap, x 136, 137 
 
 Flue sizes for indirect radia- 
 tors; Chap, vi 91 
 
 Heat-transmitting power of 
 building substances; Chap, v 62 
 
 Pipe sizes according to Baldwin 
 and Mills; Table i, Chap. vi. 73 
 
 Pipe sizes, according to Monroe; 
 Table ii, Chap, vi 74 
 
 Pipe sizes, Webster vacuum sys- 
 tem; Table iii, Chap, vi 76 
 
 Quantity of air moved by ex- 
 haust fans; Table iii, Chap, x 129 
 
 Quantity of air supplied by 
 blowers, and power required to 
 drive; Table i, Chap, x 127 
 
 Radiator connections; Table iv, 
 Chap, vi 76 
 
 Tests of indirect radiators; 
 Chap, iv 51 
 
 Velocity of air in heated flues; 
 Table iv, Chap, x 130 
 
 Volume of air necessary to 
 maintain given degree of pur- 
 ity for different periods; Ta- 
 ble i, Chap, vii 100 
 
 Temperatures 
 
 Air in heating- coils 132 
 
 Tests 
 
 Standards, in radiator tests 43 
 
 (See under apparatus concerned.) 
 Thermostats 
 
 Use with mixing dampers 143 
 
INDEX. 
 
 .56, 
 
 Thomas, R. H. Air washing ap- 
 paratus 144 
 
 Traps, automatic, for return wa- 
 ter 27 
 
 Tredgold, Thomas. Treatise on 
 heating and ventilation 7 
 
 Unwin, Prof. W. C. Flow of air 
 in round pipes 114 
 
 Valves 
 Air 
 
 Automatic 
 
 Location of radiator. 
 
 Radiators 
 
 Back pressure 
 
 Forms of 
 
 Location of 
 
 For a vacuum system in a Chi- 
 cago office building 
 
 Location of, in heating systems. 
 Reducing pressure 
 
 Form of 
 
 Location of 
 
 Ventilation 
 
 Air circulation in rooms 
 
 Amount of heat required for. 61, 
 
 By gravity 
 
 Early examples of artificial 
 
 Need of proper 
 
 Plenum and exhaust systems 
 Upward versus downward 
 
 110 
 
 Wall coils, Wrought-iron 
 Efficiency of 
 
 pipe, 
 
 -15 
 
 Warner, W. Tests of indirect rad- 
 iators 51 
 
 Water 
 
 In radiators 79 
 
 Spray for air purification 143 
 
 Water line of heating systems.. 27 
 
 Webster, Warren, & Co. 
 Pipe sizes for vacuum system.. 75 
 System of steam heating 28 
 
 Willett, James R. 
 Capacities of cast-iron boilers... 31 
 Rule for direct radiation 66 
 
 Wind 
 
 Influence of, on air leakage into 
 buildings 60 
 
 Wolff, Alfred R. 
 Air velocity through indirect 
 
 radiators 50 
 
 Capacities of disk fans 129 
 
 Centrifugal fan capacities 125 
 
 Coefficients of heat transmission 
 
 of building substances 62, 63 
 
 Form of direct-indirect radiator 
 
 setting 95 
 
 Rule for direct radiation 69 
 
 Velocity of air through heated 
 ventilating flues 130 
 
 Wood 
 Heat losses throuerh ....62, 64 
 
 Woodbridge, Prof. S. H. 
 Upward versus downward ven- 
 tilation 105 
 
 Wren, Sir Christopher. Attempt 
 at ventilation 8 
 
Ventilation and Heating, 
 
 By JOHN S. BILLINGS, A. M., M. D., 
 
 LL.D., Edinb. and Harvard. D. C. L. Oxon. Member of the 
 National Academy of Sciences. Surgeon, U. S. Army, etc. 
 
 FROM THE PREFACE. 
 
 IN preparing this volume my object has been to produce a book which will not only be 
 useful to students of architecture and engineering, and be convenient for reference by 
 those engaged in the practice of these professions, but which can also be understood by 
 non-professional men who may be interested in the important subjects of which it treats ; 
 and hence technical expressions have been avoided as much as possible, and only the sim- 
 plest formulae have been employed. It includes all that is practically important of my 
 book on the Principles of Ventilation and Heating, the last edition of which appeared in 
 1889 ; but it is substantially a new work, with numerous illustrations of recent practice. 
 For many of these I am indebted to THE ENGINEERING RECORD, in which the descriptions 
 first appeared. JOHN S. BILLINGS. 
 
 TABLE OF CONTENTS. 
 
 CHAPTER I. Introduction. Utility of 
 
 Ventilation. 
 CHAPTER II. History and Literature of 
 
 Ventilation. 
 CHAPTER III. The Atmosphere : Its 
 
 Chemical and Physical Properties. 
 CHAPTER IV. Carbonic Acid. 
 CHAPTER V. Conditions Which Make 
 
 Ventilation Desirable or Necessary. 
 
 Physiology of Respiration. Gaseous and 
 
 Particulate Impurities of Air. Sewer 
 
 Air. Soil Air. Dangerous Gases and 
 
 Dusts in Particular. Occupations or 
 
 Processes of Manufacture. Drying 
 
 Rooms. 
 CHAPTER VI. On Moisture in Air, and Its 
 
 Relations to Ventilation. 
 CHAPTER VII. Quantity of Air Required 
 
 for Ventilation. 
 CHAPTER VIII. On the Forces Concerned 
 
 in Ventilation. 
 CHAPTER IX. Examination and Testing 
 
 of Ventilation. 
 CHAPTER X. Methods of Heating. Stoves. 
 
 Furnaces. Fireplaces. Steam and Hot 
 
 Water. Thermostats. 
 CHAPTER XI. Sources of Air Supply. 
 
 Filtration of Air. Fresh Air Flues and 
 
 Inlets. By-passes. " 
 CHAPTER XII. Foul-Air or Upcast Shafts. 
 
 Cowls. Svphons. 
 CHAPTER XIII. Ventilation of Mines. 
 
 CHAPTER XIV. Ventilation of Hospitals 
 and Barracks. Barrack Hospitals. Hos- 
 
 S'.tals for Contagious Diseases. Blegdam 
 ospitals. U. S. Army Hospitals. Cam- 
 bridge Hospital. Hazleton Hospital. 
 Barnes Hospital. New York Hospital. 
 Johns Hopkins Hospital. Hamburg Hos- 
 pital. Insane Asylums. Barracks. 
 
 CHAPTER XV. Ventilation of Halls of 
 Audience and Assembly Rooms. The 
 Houses of Parliament. The U. S. Capi- 
 tol. The New Sorbonne. The New York 
 Music Hall. The Lenox Lyceum. 
 
 CHAPTER XVI. Ventilation of Theaters. 
 Manchester Theaters. Grand Opera 
 House in Vienna. Opera House at Frank- 
 fort-on-the-Main. Metropolitan Opera 
 House, New York. Madison Square 
 Theater. Academy of Music, Baltimore. 
 Pu'eblo Opera House. Empire Theater, 
 Philadelphia, 
 
 CHAPTER XVII. Ventilation of Churches. 
 Dr. Hall's Church, New York. Hebrew 
 Temple, Keneseth-Israel, Philadelphia. 
 
 CHAPTER XVIII. Ventilation of Schools. 
 Bridgeport School. Jackson School, Min- 
 neapolis. Garfield School. Chicago. Bryn 
 Mawr School, near Philadelphia. College 
 of Physicians and Surgeons, New York. 
 
 CHAPTER XIX. Ventilation of Dwelling 
 Houses. 
 
 CHAPTER XX. Ventilation of Tunnels, 
 Railway Cars, Ships. Shops, Stables. 
 Sewers. Cooling of Air. Conclusion. 
 
 Over 500 Pages. 2JO Illustrations. Sent Postpaid on Receipt of $4.00. 
 
 THE ENGINEERING RECORD, 
 
 21 PARK ROW, 
 
 NEW YORK. 
 
THE WAINWRIGHT 
 
 SAFETY VALVE 
 
 SOFT 
 
 fil/BSf, 
 
 EVEN FLOW 
 FEED WATER 
 HEATER is 
 
 IN USE IN THE 
 LARGEST POWER 
 STATIONS IN 
 THE COUNTRY, 
 ALSO THE 
 
 WAINWRIGHT 
 
 EXPANSION 
 
 JOINTS. 
 
 Send for Catalogue. 
 
 The 
 
 Taunton 
 
 Locomotive 
 
 Manufacturing 
 
 Company, 
 
 Taunton, 
 Mass. 
 
American Steam and Hot- Water 
 Heating Practice* 
 
 From THE ENGINEERING RECORD. 
 
 A Selected Reprint of Descriptive Articles, Questions and Answers* 
 With Five Hundred and Eighty-Five Illustrations* 
 
 PREFACE* 
 
 THE ENGINEERING RECORD (prior to 1887 THE SANITARY EN- 
 GINEER) has for sixteen years made its department of Steam and Hot- 
 Water Heating and Ventilation a prominent feature. Besides the weekly 
 illustrated descriptions of notable and interesting current work, a great 
 variety of questions in this field have been answered. In 1888 Steam- 
 Heating Problems was published. This was a selection of questions, 
 answers, and descriptions that had been published during the preceding 
 nine years, and dealt mainly with steam heating. The present book is 
 intended to supplement this former publication, and includes a selection 
 of the descriptions of hot-water, steam-heating and ventilating installa- 
 tions in the different classes of buildings in the United States, prepared 
 by the staff of THE ENGINEERING RECORD, besides a collection of ques- 
 tions and answers on problems arising in this department of building 
 engineering, covering the period since 1888, in which the heating of 
 dwellings by hot water has become popular in the United States. The 
 favor with which Steam-Heating Problems has been received encourages 
 the hope that American Steam and Hot- Water Heating Practice may 
 likewise prove useful to those who design, construct and have charge of 
 ventilating and heating apparatus. 
 
 Size, 8x JJ inches* Three Hundred and Seventeen Pages* Price, $4.00; postpaid* 
 
 THE ENGINEERING RECORD, 
 
 21 PARK ROW, NEW YORK. 
 
Pipe Threading. . . 
 
 = Cutting Machines 
 
 Combining in design all tHat is latest and 
 best, and fully guaranteed as to construction 
 
 FIG. I. 
 
 Apex Nipple and Pipe 
 Mill Machine 
 
 IS SHOWN BY FIG. I. 
 
 The gearing is entirely protected 
 from dust ; six different speeds pos- 
 sible with but a three-step cone. 
 Pump is out of way of operator ; vise 
 open or closed while machine is in 
 motion. Nipple grips may be closed 
 on threaded ends of pipe without in- 
 jury to thread, thus avoiding the 
 necessity of screwing nipple into 
 grips after they are closed ; this 
 feature possessed by no other machine. 
 With this machine we furnish an au- 
 tomatic threading gauge. Both left 
 and right-hand threads may be made. 
 A description in more detail will be 
 found in our catalogue. 
 
 Combined Hand and Power Pipe 
 Threading and Cutting Machine 
 
 IS SHOWN BY FIG. II. 
 
 We make this machine in several sizes. It is so 
 arranged that either hand or power may be used 
 at will, and it may be readily taken from its base 
 and us3i as a portable hand machine. It occupies 
 less floor space and guaranteed to do better work 
 than any other combined machine on the market. 
 Equipment substantially the same as that of our 
 portable machine, the description of which follows. 
 
 FIG. II. 
 
 Our Portable Machine 
 
 IS SHOWN BY FIG. III. 
 Made in a number of sizes. In quality 
 of work and rapidity of action, both in 
 threading and cutting, this machine is 
 far superior to any other. The possible 
 range of its work is greater, and quicker 
 changes from size to size 'are a feature. 
 We furnish with this machine our 
 Standard Adjustable Quick Opening 
 and Closing Die Head and our improved 
 Cutting-off Knife. The chasers are set 
 by graduation to any size desired, are 
 released from threading while in motion, 
 open to permit the cutting of the pipe, 
 and closed instantly and positively ; 
 readily replaced by other sizes. The 
 vise is self-centering and actuated by 
 
 rack and pinion. Gears completely housed from dust and to no part of the machine 
 
 are chips accessible, to its detriment. 
 
 We issue a complete catalogue fully describing and illustrating the various types 
 
 of our machines and will be glad to send it on request. 
 
 THE HERRELL flFQ. CO., Toledo, Ohio. 
 
 European Office: The Fairbanks Co., 16 Great Eastern St., London, E. C. 
 
 FIG. 
 
Water- Works for Small Cities and Towns, 
 
 By JOHN GOODELL. 
 
 PUBLISHERS' ANNOUNCEMENT. 
 
 THIS book is a, description of the methods of construction of the various portions of 
 a water-works plant, outside of a few features, like pumps, which are now left, in a 
 large measure, to the manufacturers of standard specialties. Even in respect to these 
 specialties enough general information is given to enable anyone with ordinary intelligence 
 to understand the technical descriptions in manufacturers' catalogues and the statements 
 of their agents. 
 
 The theory of the flow of water, the strength of materials entering into a water-works 
 plant, of the wind pressure on stand-pipes and similar matters are mentioned as briefly as 
 possible because they are thoroughly taught in technical schools and explained in numerous 
 text books. On the other hand, there is no book giving a general account of the methods 
 of building and maintaining works, dams, pipe lines, reservoirs, stand pipes and other fea- 
 tures in sufficient detail to enable an engineering student to understand properly the ap- 
 plication of the theories he learns in school. 
 
 There is another class to whom it is believed the book will ba particularly valuable, 
 and that is superintendents of works and engineers who may have occasion to require tho 
 compilation of the best information of any feature of such a plant. Even if a superinten- 
 dent is thoroughly acquainted with the subject on which he must prepare a report, it often 
 happens that from lack of experience in writing he may have difficulty in preparing it. In 
 such a case, 'it is confidently believed, this book will prove of assistance, particularly as it 
 has been written very largely with the idea of proving serviceable to men without technical 
 education called upon to act as members of a water commission. 
 
 In view of the fact that the information presented has been acquired by correspondence 
 with water-works officials in many parts of the country and a review of all the published 
 information of value on the subject, it is believed that even engineers and water-works 
 managers cf experience in their specialty will find the book of interest in a number of par- 
 ticulars. 
 
 TABLE OF CONTENTS. 
 
 CHAPTER I. SURFACE WATER 
 
 The Yield of Catchment Areas Gauging 
 
 Stream Flow The Meaning of Water 
 
 Analyses. 
 CHAPTER IT. EARTH DAMS 
 
 Clay -Gravel Masonry Core Walls 
 
 Water in Earthwork Cross-section cf 
 
 the Embankment Starting the Core 
 
 Wall. 
 
 CHAPTER ITI. MINOR DETAILS OF 
 RESERVOIRS 
 
 Outlet Pipes Gate-Houses Waste- 
 Weirs. 
 CHAPTER IV. TIMBER DAMS 
 
 Brush Dams Crib Dams Framed 
 
 Dams. 
 CHAPTER V. MASONRY DAMS 
 
 Foundations Materials Eart h Backing 
 Design Specifications Rock-Fill 
 
 Dams. 
 
 CHAPTER VT. SPECIAL FEATURES OF 
 RIVER AND POND SUPPLIES 
 
 Head-Works Effect of Storage on Water 
 
 Odors in Water. 
 
 CHAPTER VII. GROUND-WATER SUP- 
 PLIES 
 
 Methods of Collecting Ground Water 
 
 Quantity of Ground Water. 
 CHAPTER VIII. THE UTILIZATION OF 
 SPRINGS 
 
 Springs in Plains Hillside Springs. 
 CRAPTER IX. OPEN WELLS. 
 CHAPTER X. DRIVEN WELLS 
 
 Sinking Wells Air in Wells Well 
 
 Specifications. 
 
 CHAPTER XI. DEEP AND ARTESIAN 
 WELLS 
 
 Sinking Wells Specifications Yield of 
 Wells Quality of Ground Water. 
 
 CHAPTER XII. PUMPS 
 
 Steam Consumption Power Pumps 
 Details of the Water End Special Power 
 Pumps. 
 
 CHAPTER XIII. THE AIR LIFT. 
 
 CHAPTER XIV. PUMPING STATIONS. 
 
 CHAPTER XV. INTAKES AND INTAKE 
 PIPES. 
 
 CHAPTER XVI. CLARIFICATION AND 
 PURIFICATION OF WATER 
 Turbidity Slow Sand Filters Mechani- 
 cal Filters. 
 
 CHAPTER XVII. THE PIPE SYSTEM 
 Flow of Water in Pipes Data Concern- 
 ing Pipe and Accessories -Submerged 
 Pipe Clay Pipes and Open Channels. 
 
 CHAPTER XVIII. SERVICE RESER- 
 VOIRS AND STAND PIPES 
 Concrete-Lined Reservoirs Asphalt- 
 Lined Reservoirs Stand Pipes and 
 Water Towers Substitutes for Stand 
 Pipes. 
 
 CHAPTER XIX. THE QUANTITY OF 
 WATER TO BE PROVIDED 
 Relative Capacities of Small Works for 
 Domestic Supply and Fire Protection 
 The Influence of Small Street Mains- 
 Fire Streams. 
 
 CHAPTER XX. THE WATER WORKS 
 DEPARTMENT 
 
 Financial Considerations Checking 
 Water Keeping up the Works. 
 
 Bound in Cloth, 8vo. 
 
 28J Pages. 
 
 Price, $2.00, Postpaid. 
 
 THE 
 
 2J PARK ROW, 
 
 ENGINEERING RECORD, 
 
 NEW YORK. 
 
-MASON 
 
 Reducing Valves 
 
 ARE THE WORLD'S STANDARD VALVES 
 
 For automatically reducing and absolutely 
 maintaining an even steam or air pressure. 
 
 THey are adapted for every need and 
 guaranteed to -worK perfectly in every 
 instance. 
 
 For Vacuum Systems of Heating we maKe 
 a special valve. 
 
 WRITE FOR FULL INFORMATION AND 
 
 SPLENDID REFERENCES. 
 
 THE MASON REGULATOR CO., BOS T*. A ASS "' 
 
 / T~ A HE best designed system of heating and ventila- 
 tion may be rendered almost worthless by the 
 use of inferior apparatus inferior either in design, 
 material or workmanship. 
 
 Our design 
 represents 
 the most 
 advanced 
 practice. 
 
 Mechanical 
 Draft 
 Fans. 
 
 The circula- 
 tion in this 
 coil is posi- 
 tive, either 
 under vac- 
 uum or 100 
 .Ifce. steam 
 pressure. 
 
 We cheerfully furnish plans and drawings 
 to those interested. 
 
 Massachusetts Fan Company, 
 
 Room 50, Stock Exchange Building, = 
 
 BOSTON, MASS. 
 
American Plumbing Practice. 
 
 From THE ENGINEERING RECORD. 
 
 A. Selected Reprint of Articles Describing Notable Plumbing Installations 
 in the United States, and Questions and Answers on Problems 
 
 Arising in Plumbing and House Drainage. 
 With Five Hundred and Thirty-Six Illustrations. 
 
 PREFACE. 
 
 THE. ENGINEERING RECORD, prior to 1887 THE SANITARY EN- 
 GINEER, has for 17 years given much attention to domestic water supply, 
 house drainage, ventilation, and plumbing. Beside the frequent illustrated 
 descriptions of notable and interesting current work, a great variety of 
 questions in this field have been answered. In 1885 "Plumbing and House 
 Drainage Problems" was published. 
 
 The present volume, " American Plumbing Practice," is a compilation 
 of illustrated descriptions of plumbing installations in modern buildings 
 of every character, together with Notes and Queries touching interesting- 
 points developed in practice, from articles which have appeared in THE 
 ENGINEERING RECORD since the publication of "Plumbing and House 
 Drainage Problems/' Within this period the towering office building has 
 been developed, involving special problems of drainage and plumbing. 
 The equipment of hotels, hospitals, amusement halls, swimming baths, and 
 other public buildings has been upon the most thorough and elaborate 
 scale, and in the description of the plumbing of residences examples may 
 be found of nearly every class of dwelling. Its division of Notes and 
 Queries is intended to supplement "Plumbing Problems/ 7 bringing these 
 queries well up to date. The greater part of the book consists of descrip- 
 tive matter nowhere else available in this permanent form. 
 
 Sent Postpaid on Receipt of $3.00. 
 
 THE ENGINEERING RECORD, 
 
 21 PARK ROW, NEW YORK. 
 
GURNEY HEATERS 
 
 Are of uniform excellence. In all of them the 
 heating surfaces are so arranged as to produce a 
 maximum of heat from a minimum amount of coal. 
 All are made from the best grades of iron, have the 
 most efficient types of grates, and embody all the 
 latest improvements. 
 
 The "Doric "and "400 Series," Steam and Hot 
 Water Heaters are made for a moderate line of 
 work, particularly house heating purposes, and the 
 "BRIGHT IDEA" Series for the larger systems. 
 Their capacities are fully guaranteed. 
 
 SEND FOR LATEST TRADE CATALOGUE. 
 
 GURNEY HEATER flFQ. CO., 
 
 74 Franklin St., Boston. Ill Fifth Ave., New York. 
 
 Western Selling Agents: JAMES B. CLOW & SONS, 222-224 Lake St., Chicago, III. 
 
 ASBESTOS AND MAGNESIA PRODUCTS 
 
 NON-HEAT-CONDUCTING COVERINGS 
 FOR HEATING AND POWER PLANTS 
 
 Send for pamphlet "SAVE FUEL. ' ' 
 
 Asbesto, Sponge Felted, Magnesia, 
 Asbestos Fire Felt. 
 Asbestocel (Air-Cell). 
 
 Sectional Pipe and Boiler Coverings. 
 Keystone Hair Insulation 
 
 Structural Insulator, Sound Deadener, Cold 
 Preserver. 
 
 "Nonburn" Asbestos Building Paper. 
 Asbesto-Metallic Steam Packings. 
 
 H. W. JOHNS-MANVILLE CO., 
 
 100 WILLIAM STREET, NEW YORK. 
 
 MILWAUKEE. CHICAGO. 
 
 CLEVELAND 
 
 ST. LOUIS. 
 PITTTSBURGH. 
 
 BOSTON. PHILADELPHIA. 
 
 NEW ORLEANS. 
 
Some Details of Water-Works 
 Construction, 
 
 By W. R. BILLINGS. 
 
 Formerly Superintendent of Water-Works at Taunton, Mass. 
 
 With Illustrations from Sketches by the Author* 
 
 AUTHOR'S INTRODUCTORY NOTE. 
 
 Some questions addressed to the editor of THE ENGINEERING RECORD by persons 
 in the employ of new water-works indicated that a short series of practical articles 
 on the Details of Constructing a Water- Works Plant would be of value; and, at 
 the suggestion of the editor, the preparation of these papers was undertaken for 
 the columns of that journal. The task has been an easy and agreeable one, and now, 
 in a more convenient form than is afforded by the columns of the paper, these notes 
 of actual experience are offered to the water-works fraternity, with the belief that 
 they may be of assistance to beginners and of some interest to all. 
 
 TABLE OF CONTENTS. 
 
 CHAPTER I. MAIN PIPES 
 
 Materials Cast-Iron Cement-Lined 
 Wrought Iron Salt-Glazed Clay Thick- 
 ness of Sheet Metal Methods of Lining 
 
 List of Tools Tool-Box Derrick 
 Calking Tools Furnace Transportation 
 
 Handling Pipe Cost of Carting Dis- 
 tributing Pipe. 
 
 CHAPTER II. FIELD WORK 
 
 Engineering or None Pipe Plans Spe- 
 cial Pipe Laying out a Line Width 
 and Depth of Trench Time-Keeping 
 Book Disposition of Dirt Tunneling 
 Sheet Piling. 
 
 CHAPTER III. TRENCHING AND PIPE- 
 LAYING 
 
 Caving Tunneling Bell-Holes 
 Stony Trenches Feathers and Wedges 
 Blasting Rocks and Water Laying 
 Cast-Iron Pipe Derrick Gang Hand- 
 ling the Derrick Skids Obstructions 
 
 Pipe Derrick 
 g th 
 Left in Pipes Laying Pipe in Quicksand 
 
 Cutting Pipe. 
 
 CHAPTER IV. P I P E-L A Y I N G AND 
 JOINT-MAKING 
 
 Laying Cement-Lined Pipe "Mud" Bell 
 and Spigot Yarn Lead Jointers 
 Roll Calking Strength of Joints 
 Quantity of Lead. 
 
 CHAPTER V. HYDRANTS, GATES, AND 
 SPECIALS. 
 
 CHAPTER VI. SERVICE PIPES 
 
 Definition Materials Lead vs. Wrought 
 Iron Tapping Mains for Services Dif- 
 ferent Joints Compression Union Cup. 
 
 CHAPTER VII. SERVICE-PIPES AND 
 METERS 
 
 Wiped Joints and Cup-Joints The Law- 
 rence Air-Pump Wire-Drawn Solder 
 Weight of Lear Service-Pipe Tapping 
 Wrought- Iron Mains Service- Boxes 
 Meters. 
 
 Large 8vo. Cloth, $2.00, Postpaid* 
 
 THE ENGINEERING RECORD, 
 
 21 PARK ROW, 
 
 NEW YORK. 
 
The Architect or Engineer 
 
 who fails to investigate claims to surpassing merit 
 made by any apparatus entering into his work, 
 constantly runs the risk of remaining ignorant of 
 something he would most gladly know of. The 
 
 "Webster System" 
 
 of Steam Circulation for Heating Purposes lays 
 claim to an efficiency and economy which, if 
 vindicated, constitute that system a class by itself. 
 If the steam heating of a large and important 
 building is a problem you must shortly solve, 
 we shall be pleased to have you write us. 
 
 \Varren AVebster (SL Co., Camden, N. J. 
 
 NEW YORK, 322 Broadway. PHILADf LPHIA, 1105 Stephen Girard Bldg. 
 BOSTON, 743 Fremont Bldg. CHICAGO, 1509 Monadnock Bldg. ST. LOUIS, 621 Century Bidg. 
 
 STEAM PIPE AND BOILER COVERINGS 
 
 ASBESTOS GOODS 
 TRADE SUPPLIED CONTRACTS EXECUTED 
 
 ROBERT A. KEASBEY 
 
 Telephone is i s coniandt 83 Warren Street, Ne'w York 
 
 The "EM-ESS" SELF-CLOSING FAUCETS 
 
 having been honestly made by us for twenty years, 
 were naturally reliable, never "stuck open," and de- 
 servedly popular. Hence the numerous imitations 
 that have appeared. The word "Doherty" is now pub- 
 lic property, and is used simply to designate a type of 
 self-closing Faucet which is made by so many people 
 that the name no longer affords a guarantee of dura- 
 bility. Plainly specify The "Em-Ess" Self-C los- 
 ing Cocks, which are made by us, exclusively, and 
 look for our stamp. 
 
 The MEYER=SNIFFEN CO., Ltd., 
 
 CLOSING 5 East 19th Street, New York. 
 
PHILADELPHIA. 
 
 WESTFIELD, MASS. 
 
 THE H. B. SMITH CO. 
 
 133-135 CENTRE STREET, N. Y. 
 
 Manufacturers of 
 
 The Mercer Boiler. 
 
 STEAM & WATER 
 
 HEATING 
 APPARATUS 
 
 For all Kinds of Buildings. 
 Send for Catalogue. '' 
 
 BOILERS. Mills, Mercer, Gold, Cottage, Menlo. 
 RADIATORS] Imperial, Princess, Union, Royal Union, 
 
 (Direct), j Sovereign, Coronet, Diadem, etc. 
 RADIATORS j Gold's School Pins, R & L Nipple Pins, 
 
 (Indirect), j Drum Pins, etc. 
 
 Reliable News Regarding New Construction. 
 
 THE ENGINEERING RECORD 
 
 work for which bids are to be asked, likewise reports of bids submitted all care- 
 fully edited in order to eliminate items of no value to a contractor, manufacturer or 
 dealer in building and engineering supplies. 
 
 It was established in 1877, and spends a good deal of money to secure and 
 print only useful items. Hence the reputation for reliability which it has attained. 
 
 Its Contracting news and Advertisements inviting bids for projected work from 
 the Government, State and Municipal authorities, cover work in all sections of the 
 United States and Canada. 
 
 They relate to Water- Works, Sewers, Sewage Disposal, Bridges, Public Build- 
 ings, Business Buildings, Schools, Railroad Depots, New Manufactories, Dwellings 
 (exceeding $10,000 in value), Railroads, Electric Railways, Power, Gas and Electric 
 Light Plants, Paving, Roadmaking, Street Cleaning, Garbage Disposal, U. S. 
 Government Work and Miscellaneous Work including contract prices as recorded 
 in bids submitted. 
 
 Each issue contains important news items not previously published elsewhere. 
 
 It is issued so as to reach subscribers within a radius of 400 miles of New York, 
 on Saturday; within fifteen hundred miles, on Monday, and the Pacific Coast, on 
 Thursday, of each week. 
 
Hot- Water Heating and Fitting, 
 
 A Treatise on the Practice of Warming: by Hot Water, with Modern 
 Methods Described and Explained. 
 
 By WILLIAM J. BALDWIN, M. E. 
 
 The book contains much of the matter on this subject which has appeared in the 
 columns of THE ENGINEERING RECORD, together with a large amount of 
 additional original data; the whole containing a large amount of practical 
 and useful information of great value to the Engineer, Architect, Mechanic, 
 and Householder. Handsomely bound in cloth and fully illustrated, 392 pp. 
 Among the questions treated are the following: 
 
 The cause cf the circulation of the water 
 within heating apparatus. 
 
 Motion explained by the use of diagrams. 
 
 liow to find the velocity of .the flow of water 
 in pipes of an apparatus. 
 
 Simple lormulse explaining the laws which 
 govern the flow of water in an apparatus. 
 
 Diagrams showing the coefficients of the 
 curve of the expansion of the water. 
 
 Diagram showing the velocity of water in 
 feet per second when the height from 
 which it flows is known. 
 
 The use of the diagrams in estimating the 
 flow of the water through the apparatus. 
 
 Table of the quantity of water in U. S. gal- 
 lons that will pass through pipes of a 
 given diameter. 
 
 Table giving the friction loss in inches of 
 the water head for each ten feet of 
 length of different sizes of clean iron 
 pipes discharging given quantities of 
 water per minute. 
 
 The loss of head by friction and resistance 
 of elbows. 
 
 Saving by long radius elbows. 
 
 Saving by smooth elbows. 
 
 Resistance caused to the flow of water by 
 elbows and return bends. 
 
 Resistance caused by valves, etc., and how 
 it may be made less. 
 
 How to find the flow of water through main 
 pipes of an apparatus. 
 
 To find the quantity of water in U. S. gal- 
 lons that will pass when the total head 
 is known. 
 
 To find the fM^meter of a pipe for a given 
 discharge of water. 
 
 To find the discharge of pipes for given 
 diameters. 
 
 How to compute radiating surfaces. 
 
 Experiments of Tredgold and Hood in warm- 
 ing surface. 
 
 modern investigators on 
 
 Experiments of 
 radiators. 
 
 How to find the amount of water that 
 should pass through a radiator to do 
 certain duty. 
 
 How to determine the size of inlet and out- 
 let to hot-water radiators. 
 
 How to estimate the quantity of water that 
 should pass through a radiator for a loss 
 of 10 degrees. 
 
 Diagram giving the diameter of flow and re- 
 turn pipes when the radiating surface 
 and the length of the pipes are known. 
 
 Experiments illustrating use of diagram in 
 the. piping of buildings. 
 
 The different systems of mains used in hot- 
 water heating. 
 
 Treatment of single circuits. 
 
 Branch circuits. 
 
 Compound circuits. 
 
 How to proportion the apparatus for in- 
 direct heating. 
 
 Heat given off per square foot of surface. 
 
 Loss of heat through walls and windows of 
 a room. 
 
 Heat lost by ventilation how to consider it. 
 
 How to find heating surface of a room 
 warmed by indirect radiation. 
 
 Comparative experiments with hot-water 
 coils. 
 
 Diagram of sizes of main pipes for indirect 
 radiation. 
 
 Examples of buildings warmed by hot water. 
 
 Boilers used in hot- water apparatus. 
 
 Direct and indirect radiators used in hot- 
 water apparatus. 
 
 Expansion tanks and how they should be used. 
 
 Special fittings for hot-water apparatus. 
 
 How to conduct experiments in testing the 
 efficiency of hot-water radiators. 
 
 How to control fires by the temperature of 
 water. 
 
 Large 8vo. 392 Pages, Fully Illustrated. Sent Postpaid on Receipt of $2.50. 
 
 THE 
 
 21 PARK ROW, 
 
 ENGINEERING RECORD, 
 
 NEW YORK. 
 

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