Document 2KOxyezwJ1XExNNyBV6yewE6

American Society of Heating and Ventilating Engineers Guide, 1930 * jy Leader areas for first floor, square inches = = approximately 0.012/7 (4) . Leader areas for second floor, square inches = H = approximately 0.007H (5) Leader areas for third floor, square inches = .fir = approximately 0.006H (6) These equations are applicable to straight leaders from 6 to 8 ft. in length. Longer leaders must be very thoroughly covered or else the ( Fig. 2. Loss in Temperature in 8-in. Leader Pipe of Various Lengths at Different Register Temperatures ' vertical stacks must be increased in area as discussed under wall stacks. If some provision is not made for these longer leaders, the air tempera ture may be much lower than anticipated and the room will not be properly heated. While Fig. 1 takes care of the drop in temperature in straight leaders up to 8 ft. in length connected to stacks having about 75 per cent the area of the leader, the designer must make allowances for all other conditions. The temperature drop in leaders of various lengths at three different register temperatures is shown in Fig. 2. Leader sizes should in general be not less than obtained by equations 130 Chapter 5--Heating with Warm Air Furnaces by Gravity (lj to (3) nor should leaders less than 8 in. in diameter be used. It is not considered good commercial practice to specify diameters except in whole inches, although there is no real reason for not using half inches if necessary. The tops of leaders should be at the same elevation as they leave the furnace bonnet, and from this point there should be a i H4th coinsti anrt benat /nrpo t 7* LOO to heater, of 2/,'OOO 3. t.a *r / 1 1 II LJ bnot to S' register. L eaders. A y t 0.90 8-0" to if boof /o V tt /. 1 / tm t" to-, )080 7 /kSit Single Wall Stack Doab/e Wa// Stack-, f/ ~r / A 6 V/7 u ter ^6in<?/e Watt Stack b/e /Va ft - fac.k I^ 0.70 !/ h/ 1 T 1~ A Ustat ks come ed 'iff I 060 t,he best s/na/e watt stack 1 /h both iO-i/7. and 3-in. Leader Tests. o o./ a2 G3 o.4 o.s a6 a7 08 a9 /.o Patio Stack Area to L eacter Area Fig. 3. Relative Heating Effect of Stacks at Constant Heat Input to Furnace Note.--Pipe bare, bright tin except asbestos strips for joints. uniform up-grade of 1 in. per foot of run in all cases. Leaders over 12 ft. in length are to be avoided or should receive very special attention. WALL STACKS The wall stack for an upper floor should be made not less than 70 per cent of the area of the leader which has been selected from Fig. 1. So long as the leader is short and straight as was the case for Fig. 1, such a practice is probably justified since the loss (Fig. 3) in capacity occasioned by the smaller stack is not very serious for stacks having areas iii excess of 70 per cent of the leader area. For leaders over 8 ft. in length or for leaders which are not straight,-the ratio of stack area to leader area should be .greater than 70 per cent in order to offset the greater temperature losses (Fig. 2) in the longer leader. In gravity 131