Document ypr1bgK83EkM0oKzKx8eM3Nr3

American Society of Heating and Ventilating Engineers Guide, 1930 It may be desirable in some cases to utilize a condensation pump rather than a vacuum pump where the heaters are too close to, or must be below, the boiler water line. Fig. 6 illustrates an approved hook-up for such a .condition though, of course, the apparatus may be used with a wet return as well as with the dry return shown. It will be noted that each heater has a trap. When a condensation pump is used with a one-pipe system a false water line should be established so that the sealing of each dry return against the others, so important with one-pipe systems, shall be main tained. Sometimes, in this contingency, it is desirable to place a float trap on the end of each separate dry return connection to the pipe which supplies the pump-suction. There are a number of meritorious proprietary types of steam, vacuum return line, differential, and vapor heating systems, which' vary in certain particulars from the foregoing typical examples. These systems have been developed to meet the requirements of the newer architecture of modern building construction and are based on well established engineer ing principles of control for. occupancy; wind and sun effect, zone demands, etc. Descriptions of these systems will be found in the catalog section of The Guide. Table 11. Maximum Allowable Capacities of Up-Feed Risers for Two-Pipe Low Pressure Steam Based on A. S. H. V. E. Research Laboratory Tests Pipe Sma Inches A V* i 1 Yi 114 2 m 3 3M 4 . Velocitt Feet peb Second Pressure Drop Ounces per 100 Ft. B c 20 23 1.78 27 1.57 30 1.48 35 1.33 . 38 1.16 41 0.95 42 0.81 43 0.71 Sq. Ft .. Radiation D 40 74 151 228 438 678 1129 1548 2042 Capacity B.ta. per Hour E 9550 17,900 36,500 55,200 106,100 164,100 . 273,500 375,500 495,000 Lb. Steam per Hour F 10.0 18.45 37.65 57.0 109.5 169.4 282.2 387.0 510.5 INSTRUCTIONS FOR USING TABLE 11 1. The capacities given in this table should never be exceeded on two-pipe risers. . 2. Capacities based on Vi lb. condensation per square foot equivalent radiation and actual diameter of standard pipe. 3. All pipe should be well reamed and free from constrictions. Fittings should be up to size. (See Tables 7 and 8). 350 Chapter 20--Piping for Steam Heating Systems Table 12. Pipe Sizes for Two-Pipe, Gravity, Vapor*> Systems, where Equivalent Length of Run from Boiler or Source of Supply to Farthest Radiator does.not exceed 200 ft. Capacity in Sq. Ft. of Equivalent Radiation Based on Total Pressure Drop of 1 oz. per 100 ft. Pipe SlEB Inches Supply Main Dripped and Branches to Risers Dripped Steam and Con densate flowing in atm* direction. AB Vi i 56 8upply Risers Up-Feed Branches to Supply Risers and Radiators Not Dripped Return Rtherw C Dl B 30 190 56 26 450 Wet Return Main '700 Dry Return Main G 320 Wi 122 190 122 190 58 990 1200 670 95 1500 1900 1058 2 386 386 195 3000 4000 `2300 635. 635 395 6700 3800 3 1163 3H 1737 4 2457 1129 1548 2042 700 1150 1700 -- .... 10,700 -- 7000 10,000 -- 5 4546 -- 3150 -- -- -- 6 7462 Different makes of supply and return valves, steam traps and other specialties vary as to capacity, therefore use size as recommended for any particular make. Vertical connections to be of same size as valve and trap used. Return horizontal runout to be not less than H in* \Q-rj / or \American Socistt Heating and Ventilating Enpinrzhs Not to be Reprinted Wlth- copyngn , J Healing and Piping Contractors National Association / out Special Permission INSTRUCTIONS FOR USING TABLE 12 1. Radiator branches more than 8 ft. in length should be one size larger than shown n Column D. b2. This table is for systems which are open to atmosphere or operate under slight pressure or partial vacuum without use of vacuum pumps. 3. These tables apply where pipes are properly reamed. No allowances for defective material or workmanship have been made. (Also see Tables 7 and 8). 4. Capacities based on V lb. condensation per square foot per hour equivalent radiation and actual diameter of standard pipe. 5. Extra length to be added to straight run of pipe for various fittings and valves to determine equivalent length. (See Table 4). 6. Where it. is necessary to drip a supply main, supply riser or branch to a supply riser, same should be dripped separately intb a wet return.* The drip for a vapor or vacuum system may be taken into a dry return through a steam trap. 7. Pitch of mains should be not less, than A in. in 10.ft.; on horizontal branches to radiators and risers at least Vs in. in 10 ft. 8. In general it is desirable not to have a supply main smaljer than 2 in. in diameter. When the supply main is larger than 2in. at the beginning, it is desirable that it shall not be smaller thahr2J^ in. at the end. 351