DIAMETER OF RADIATOR CONNECTIONS. Size of pipe, in inches Area, in square feet 1122 18 40 70 120 200 300 For indirect hot-water heating, the sectional area of the mains should approximate the sum of the area of the branches taken therefrom, but where there is no indirect work, the sizes may be less. All fittings used on hot-water mains should have easy curves and the branches should be Y's, to reduce resistance to a minimum. Special distributing fittings should be used to induce circulation through radiators on the first floor. SIZES OF MAINS AND BRANCHES. Sizes of Main. 1" will supply two ". Sizes of Branches. 14" will supply two 1"; or one 1" and two ". 2" will supply two 13" and one 1"; or one 2" and one 1". All flow and return pipes should be of the same size. All pipes must rise from the boiler to the radiators with a pitch of at least 1 in. in 10 ft. The expansion-tank capacity should be at least onetwentieth that of the entire apparatus, if it is an open tank. Closed tanks are not recommended. RADIATING SURFACE SUPPLIED BY HOT-WATER RISERS. DIRECT RADIATION. FALL OF TEMPERATURE, 20°. The manner of determining the proper sizes of the various parts of a hot-water piping system, by means of the foregoing tables, may be explained by means of the accompanying illustration, which shows the area of heating surface of each radiator, the height of the various risers, and the length of the horizontal branches and mains. The figures having the symbol attached to them, thus: 60, indicate the area, in square feet, of the radiator at that branch. The risers are numbered No. 1, No. 2, etc. for convenience in reference. Having a suitable working drawing, the work of computing the diameters of pipes should begin at the point most remote from the boiler, which, in this case, is the radiator on the fourth floor on riser No. 4. The riser must supply water sufficient for 60 sq. ft. of heating surface at that point. Referring to the last table given, it appears that a 1" pipe will serve a maximum of 128 sq. ft. on the fourth floor; in order to reduce as much as possible the frictional resistance to the flow of water a 14" pipe therefore should be used. The pipe leading from the second to the third floor must supply the 60' radiator on the fourth floor and also the 66' radiator on the third floor-a total of 126 sq. ft. The table shows that a 1" pipe should be used to supply 126 ft. of radiation on the third floor, the next smaller size being a trifle too small. The riser from the main to the second floor must supply three radiators, aggregating 210 sq. ft. The table shows that 2" pipe is a little larger than is necessary; but it should be noted that there are elbows at the foot of these pipes; therefore, it is wise to use pipe of 2" diameter. The sizes of the other risers should be determined in a similar manner. The horizontal lines may then be considered. That portion of the main extending from No. 4 riser to the connections to No. 3 must supply a first-story radiator in addition to No. 4 riser, aggregating 312 sq. ft. The length of the flow pipe is 100 ft., which, added to the same length of return pipe, makes a circuit of 200 ft. Referring to the table of sizes of mains, it appears that 312 sq. ft. of surface, on a 200' circuit, requires a 3" pipe. This size is a little larger than that actually required, and will compensate for the elbows at b. At the point c another circuit is attached, No. 3, which supplies 240 sq. ft. of heating surface, making the total surface to be supplied at that point 240 + 312 = 552 sq. ft. The distance between the points c and d is 75 ft., making the circuit 150 ft. long. The table, "Sizes of Mains," shows that 552 sq. ft. of surface, on a 200' circuit, will require a 3" pipe. The return may be continued to the boiler with that size, but the flow main should be enlarged to 4 in. at d to provide for the radiator at e. Although the length of the connections to this radiator is much greater than is ordinarily found in practice, the radiator is comparatively close to the boiler, the branch connection is taken from the top of the main, and hence a 1" pipe is sufficiently large to supply it. It will be noted that this radiator is also provided with an independent return connection, as shown at f. This construction insures a more positive and rapid circulation than if the return were connected into the return main at d. If the radiator were located close to the mains, there would be no considerable advantage in providing it with an independent return. The circulation in circuit No. 2 would probably be improved by providing the return pipe g with an independent connection to the boiler, instead of connecting it to the return main, as shown in the illustration. The radiator h, on circuit No. 2, has long connections. As indicated further on, a given size of pipe will supply 1.72 times as much radiating surface on the third floor as on the first; hence, this radiator corresponds to one on the first floor having 48 ÷ 1.72 28 sq. ft. of surface. The preceding table shows that 1" pipes will be sufficiently large to furnish an adequate supply of hot water to the radiator. = The horizontal pipes on the upper floors of a building, and also the risers leading thereto, may be made smaller in diameter than those on the lower floors, because the force that impels the water increases with the height of the cir cuits. The proper size of a pipe having been determined for a given service on the first floor, the diameter for equal service on higher floors-the temperatures remaining the same-may be found by multiplying by the following factors: 2d 3d 4th 5th Story. .87 .80 .76 .73 The area of heating surface that may be supplied by a pipe of given diameter will increase as the circuit is made higher. If the area known to be right for a given size of pipe on the first floor is taken as 1, the areas on the upper floors will increase in the following order: Story BLOWER SYSTEMS OF HEATING. PURPOSE, ADVANTAGES, AND REQUIREMENTS. Blower systems are used for ventilating as well as warming buildings by forcing or by inducing a flow of air through them by means of fans. The terms forced blast and hot blast are frequently applied to such systems to distinguish them from natural, or gravity, methods of heating and ventilating buildings. Properly speaking, the term forced blast should be applied only to blower systems of the plenum or pressure type, in order to distinguish these from induced blast or exhaust systems. Strictly speaking, blower systems are those in which the air for warming and ventilation is supplied by cased fans or blowers. Among the principal advantages in the use of the blower, or mechanical, systems of heating and ventilating are the following: Positive circulation of fresh air at a desired temperature, any and all parts of the building being warmed with like certainty; perfect ventilation, regardless of temperature; and positive movement of the heated air through the ducts and flues at a pressure independent of atmospheric conditions. |