Document K6Y54YK4rEvyj6rBZ8mdRX68Q

".'2S5 American Society of Heating and Ventilating Engineers Guide, 1925-26 The system is to supply 12,500,000 B.t.u. per hour to a group of eleven buildings with a temperature drop of 40 deg. The system is provided with a reversed return. The pipe sizes are selected so that the friction heads in the eleven circuits are practically equal. The velocity of the water varies from.334 to 7J^ ft. per second. The therretical horsepower required to circulate the water through the main is Fig. 38. Layout for Sizing Hot Water Mains 11.9. The table in Fig. 37 shows the calculations for one of the eleven circuits. If the circulation within the buildings is maintained by the pump, the power required therefore must be added to that already calculated. Each flow and return pipe, connecting a building and the mains, should be provided with a gate valve and a thermometer and the gate valves should be adjusted so that the temperature drop in each of the eleven buildings is 40 deg! SIMPLE RULE FOR SMALL GRAVITY SYSTEMS In designing a hot-water system for a residence or other small buildings the following simplified method by N. S. Thompson and C. A. Fuller gives good results for the usual two-pipe basement main system. 86 ' American Society of Heating and Ventilating Engineers Guide, 1925-26 Determine the size of radiator tapping and connection from Table 49 and the size of riser and main from Table 50. To illustrate assume the layout in Fig. 38. The radiator connections determined from Table 49.are as follows: A -- 1 in. B = 1 in. C = 134 in. D = 1 in. E = 134 in.' F = 134 inG = 1 in. H = 1/4 in. Where one radiator only is supplied the riser and mains are sized the same as the radiator connection. Where more than one radiator is supplied the pipe size is determined from Tables 49 and 50 as follows: A = 1 in. = 10 Equivalent carrying capacity B- l in.' - 10 " 20 = 1 34 in. pipe between D and C C = 1}4 in. = 20 Equivalent carrying capacity 40 = 2 in. pipe between D and C D = 1 in. = 10 50 = 2 in. pipe between J and D '. Proceeding in like manner the other sections of pipe are found to be as follows: E to F = 134 in. ^ . F to G = 2 in. Gto F = 2 in. H to Mains = 234 in. J to K = 3 in. , Table 49. Hot Water System Pipe Sizes and Connections Pipb Size First Floor Second Floor Third Floor Fourth Floor 1" 134' 134" 2" 40 70 110 180 300 50 60 70 80 90 100 120 135 150 195 210 230 350 400 500 In connection with Table 49, the following equalizing Table 50, should be used to determine the size of risers and basement mains. Table 50. Equalizing Table for Sizing Risers and Mains ______ Size or Pipe Equivalent Carrying Capacity Size of Pipe Equivalent Carrying Capacity 34" l" 134" 134" 2" 234" 2 3" 5 334" 10 4" .20 5" 30 6" 60 7". 110 8" 87 175 260 380 650 1050 1600 2250