All these layouts would require the same grate, chimney, and a like amount of heating surface in the boiler although with widely varying quantities of direct radiation. These principles used in computing the schedules apply to all buildings and dwellings with heating surface directly connected to the boiler or heat source. Ready comparison may be made as to the actual effect of different assumptions on the ultimate solution. The roof and wall construction are assumed and heat losses figured. The radiators marked on the plan (Fig. 7) are for the first condition of water or steam at 210 deg. F. and 70 deg. F. in the rooms, and 10 deg. F. outside. No allowance is made for exposure and the infiltration loss is calculated by two methods which show about 10% difference in results. This is well within the error of the assumptions.

It is always safe to increase the air change to at least 1 per hour where doors open directly out of doors. This was done in the example under consideration. The theory of air leakage would not hold under these conditions. It is also well to reduce the air change on the top floor, especially if elevator doors open into the room. These shafts create a natural draft tending to take the heated air from the lower floors overheating the top floor. The heat losses were determined regardless of the type of system or type of radiator, as they would be the same in any

case.

10c. Radiators.-The heat losses of the building and rooms are compensated by radiators of various types. Radiators when placed directly in the rooms are known as direct radiators. When placed in a central location and supplied with air ducts, they are known as indirect radiators, the air being supplied either by a fan or by gravity circulation. Radiators with an out-door connection through the wall are known as direct indirect radiators. Column Radiators.-These are built up of sections of various heights put together with screw or push nipples. The sections are known as leg and loop sections. Each screw nipple has two lugs which engage a mandril so that the sections and corresponding nipples which have right and left threads may be screwed together. Round paper gaskets are placed between the sections. The push nipples are machined and sections pressed together and through bolts are put in to hold the sections in place.

There are also special column radiators known as circular, corner, stairway, and hot closet. extra high legs or be legless and supported on wall brackets.

These may have

Hot Water Radiators.-What are known as hot water radiators have a top connection tapped 11⁄2 in. up to and including 3-column radiators. Four-column radiators are tapped 2

in. These openings are provided with bushings and plugs so as to provide connections of various sizes. The steam radiators have only a bottom connection and cannot be used on hot water systems due to air pockets in the top of each section. It is becoming customary to utilize hot water radiators for steam as better results are obtained due to the ease with which the pressure within the radiator is equalized on account of the top connection giving a better drainage and circulation, a practice to be commended. Some claim these radiators air bind when used on steam systems but if the air valve is placed low down on the end section and the radiator is properly connected, there should be no trouble. It also facilitates air removal through the return piping system when hot water radiators are used on a steam heating system.

Pressed Steel Radiators.-These are made of very light sheet steel, the sections being welded together, making them practically jointless. They weigh less than 2 lb. per sq. ft. of surface as against 7 lb. per sq. ft. for cast iron, and they are tested to 40-lb. pressure. These

-Screen 10 wide 64%

Screen 5 wide 64%

FIG. 8. Enclosure for concealed direct radiation.

radiators should be built up with small circular elements so that higher pressures may be used with a minimum weight of metal and so that they will have maximum transmission capacity and good drainage.

The weight of cast iron is a serious objection, especially for use in high buildngs, as the weights have to be carefully determined. Where caisson work to bed rock is necessary, a reduction of 500,000 lb. weight in 100,000 sq. ft. of radiation may be made by the use of sheet metal instead of cast iron. This saving in weight is equivalent to an increase of 2500 sq. ft. or a space 50 X 50 ft. of floor space for the same foundation, estimating 200 lb. per sq. ft. load on the foundation.

A great deal has been said about corrosion in pressed steel radiators but if pure metal is used, and the radiators can be thoroughly drained, there is no danger. On hot water systems with the water unchanged, these radiators will last indefinitely as the water acts as a preservative to the iron when all air is removed.

The present sheet metal radiator with only 40-lb. test pressure is very limited in its use. Cast-iron radiators are tested to 80-lb. pressure and where higher pressures are desired, the metal thickness may be increased to stand any desired pressure. The weight and cost, however, is increased in proportion to the thickness.

Enclosed Radiators.-Enclosed radiators should be increased in amount of surface from 15 to 25% depending upon the type of enclosure. From tests by Harding and Lichty at the University of Illinois, the effect of shelves was to reduce the transmission 5% and, if very close to the top of the radiator, 10%. Recessed radiators, 21⁄2 in. from the wall on the back, were reduced 10%. The most efficient type of enclosure, reducing the efficiency to 80 % of the open radiator, is shown in Fig. 8. Enclosed radiators, however, are to be avoided if possible.

10d. Pipe Coils.-Pipe coils are the most efficient form of heating surface and when constructed properly, are really better and less offensive looking than radiators, but high labor costs and the cheapness of cast-iron radiators have caused them to be superseded except in cases where long coils may be utilized, as in factory work, thus reducing the labor cost for connections.

Angle valve

breaks in the wall prevent the use of long coils. When the pipes are so short as to prevent the swing of the return bend in screwing them on the pipe, right and left threaded bends are used generally for coils under 10 ft. long. A box coil is made from a series of return bend coils screwed into two headers at the ends. With header and return bends an infinite number of combinations may be made in coil work.

Coils are often placed overhead in factory work to get them out of the way. Since heated air rises, the heat has to back down to about 6 ft. from the floor before the heating effect is obtained. This means the coils are in a temperature 10 or 15 deg. higher than the average room temperature. Where used on ground floors with open doors, it has been found difficult to get the first floor warm as most of the heat was dissipated in raising the temperature of the floor above. Where there are moving belts, and where high pressure steam is used with corresponding high temperatures, fairly good results are obtained.

dow accelerating the upward and downward flow along the ceiling from the radiator, thus increasing the velocity of the air and the heat transmission by convection.

Persons sitting at the window will feel a disagreeable draft due to the cooling effect of the cold glass surface on the downward current of air, but if a radiator is placed under the window, the heat by convection from the radiator neutralizes the downward air current over the cold glass, thus reducing the air movement materially in the room and therefore counteracting the draft. However, both of these effects are small as compared with the possible and probable errors of assumption in computing the heat losses and square feet of radiation.

11. Principles of Piping.-Figs. 11, 12, and 13 show diagrammatically principles that, if observed, will facilitate the solution of the problem of proper pipe sizes for steam and water systems and insure better results in operation.

Fig. 11 is the generally accepted method of laying out steam and water systems. Thermostatic traps or choke valves are absolutely necessary to insure operation when the piping is arranged in this manner. With the same work in each radiator and the same drop per unit of

distance, without the thermostatic traps the fluid would actually be required to flow up hil! or from a lower to a higher pressure or temperature. There would be in any case, a retardation of the flow and this is frequently the cause of trouble on heating systems, although somewhat exaggerated in the sketch. By observing the above principles, errors of calculation and assumption are largely eliminated and adjustments of flow after installation are avoided. In Figs. 12 and 13 all radiators are exactly the same distance from the source and the cooling increments are all

in the same direction or added in the direction of the flow. Fig. 13 is a method applying to hot water systems whereby the radiators are shunted, although the radiators at A may be somewhat cooler than those at B; it is readily seen that all cooling effects are in the same direction, and as the average mean temperature is used, it will have little effect on the system. In Fig. 13 all tees are full size on the run which has a great deal to do with reducing friction, as reducing tees offer the greatest obstruction to flow. This defect does not appear in systems of steam and water with low velocities. All pipes should also be carefully reamed to remove the burr, as sometimes 4 in. of the diameter is lost where the burr is left. The principle involved in a shunt circuit may be stated as follows: The drop in pressure between B' and B is the main. The quantity of water flowing from C to B' is the same as From formula of Art. 9 for loss of head in friction IV2 71 V12 = d di

FIG. 11.-Diagram showing distances unbalanced, with supply and return flowing in opposite directions, causing the cooling increments to be positive and negative.

same through the radiator as through the from B' to B through both passages (Fig. 13).

in which IV and d refer to the main (BB′), and lı, V1, and di to the shunt (BB'). This formula gives the relation between the velocities in the two circuits between B and B' and makes possible the solution of the proper size of pipes for any required flow.

12. Low Pressure Gravity Steam System.-The boiler on this type of system is connected to the radiators by a series of supply and return pipes, arranged so that the condensation flows

4.8 2.24 9.65.04

14.4.9.0

7.51.55 15.03.44 22.5 6.08

114

0.29 11.61.14

23.22.6

34.8 6.64

132

0.205 16.80.82

33.6 1.8

2

0.48

212

3

316

4

42

5

6

7

8

9

10

12

14

16

19.2 14.0 30.0 10.0 46.0 7.25 58.0 10.44 50.4.3.28 67.0 5.0 84.0 7.2 60.01.09 90.0 1.92 120.0 3.14 150.0 4.36 180 5.88 0.34 92.80.76 139.5 1.34 186.0 2.11 232.0 3.04 278 4.1 0.25 134.0 0.56 200.7 1.0 267.0 1.56 334.0 2.25 401 3.06 182.00.48 274.0 0.82 365.0 1.32 456.0 1.9 547 0.37 357.0 0.66 476.0 1.04 595.0 1.5 714 2.04 0.53 602.0 0.82 752.0 1.2 902 1.64 1,052.0 0.48 744.0 0.75 930.0 1.08 1,116 1.47 1,302.0 0.39 1,073.0 0.56 1,341.0 0.83 1,609 1.13 1,877.0 0.29 1,460.0 0.45 1,825.0 0.65 2,190 0.25 1,908.0 0.39 2,385.0 0.56 2,862 0.33 3,021.0 0.47 3,624 0.3 3,720.0 0.43 4,464 0.58 5,208.0 0.26 5,370.0 0.34 6,444 0.46 7,518.0

back to the boiler by gravity. Radiators may be connected with single pipe risers and runouts or with separate supply and returns, known as one and two pipe systems of piping.

All steam systems connected in direct circuit with the boiler require a head of water in the vertical return as it enters, to counterbalance the difference in pressure in the boiler and radiation due to the condensation of the steam and friction of the fluid. This necessitates a difference in level between the lowest dry return pipe and the water line of the boiler of 2 ft. for each 1 lb. difference in pressure, or, in most cases, 3 or 4 ft. The greater the initial pressure carried, the greater the difference in level required. If the dry return is too close to the water line, water will collect in the horizontal pipe, and failing to return, will cause low water in the boiler. If the boiler pressure is

lowered, the necessary counterbalancing head in the return is also reduced and the water will flow back to the boiler. The job, however, should be designed so this will not occur or it should be remedied by raising the return or lowering the boiler. Returns are known as wet and dry. Those above the water line carry very wet steam and water, and those below the water line, known as wet returns, carry water only.

124. Size of Steam Pipes.-Diagram 2 and Table 14 may be used for the steam lines on all low pressure steam systems from atmosphere to 10-lb. pressure. Their use will give somewhat greater capacity at the higher pressures due to the increase of the density of the steam. Diagram 2 shows two sets of lines, one dash and one full. The dash lines refer to the

4.0

534.0

5.06

602.1

6.24

3.3

2.64

2.13

1.92

730.0 4.21
952 O 3.33
1,203 0
2.7
1,488.0 2.43 1,674.0 3.0

821 0 5.3 1,071.0 4.16 1,354.0 3.3

669 7.55 912 6.4 1,190 5.04 1,504 4.22 1,861 3.68

1.47

2,682 2.78

13.2

6.2

15.8

12.0

18.5

22.0

735.9 1,003.0 7.6 1,309.0 5.9 1,654.0 4.8 2,046.0 4.32 2,146.0 1.87 2,414.0 2.3 2,950.0 3.32 1.15 2,920.0 1.46 3,285.0 1.8 3,650 2.19 4,015.0 2.60 1.0 3,816.0 1.25 4,293.0 1.55 4,770 1.86 5,247.0 2.25 0.84 4,833.0 1.06 5,437.0 1.3 6,041 1.58 6,646.0 1.87 0.76 5,952.0 0.96 6,696.0 1.2 7,440 1.44 8,184.0 1.71 0.61 8,592.0 0.76 9,666.0 0.95 10,740 1.15 11,814.0 1.36 12,888 1.6 13,962 103 0 11,100.0 0.50 11,688.0 0.64 13,149.0 0.784 14,610 0.95 16,071.0 1.14 17,532 1.34 18,993 113.0 16,590.0 0 42 15,264.0 0.53 17,172.0 0.66 19,080 0.80 20,988.0 0.96 22,986 1.12 24,894 123.0 23,490.0

6,870.0

Pressure drop in lb. per sq. in. per 100 lin.ft. (x16 for oz. per sq. in)
8888

Pounds of steam per hour (÷.25 for sq.ft standard radiation) "Pipe to 42"Pipe.

Pounds of steam per hour (÷.25 for sq.ft standard radiation) 4"Pipe to 16' Pipe.

Pressure drop in oz. per sq. in per 100 lin. ft.