Document ROqaXz7zQkQXn2Z6a5OYQmLB

American Society of Heating and Ventilating Engineers Guide, 1937 PROPORTIONING WALL STACKS The wall stack for an upper floor should be made not less than 70 per cent of the area of the leader. In cases where 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 serious for stacks having areas in 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 Chapter 23--Gravity Warm Air Furnace Systems REGISTER SELECTIONS The registers used for discharging warm air into the rooms should have a free or net area not less than the area of the leader in the same run of piping. The free area should be at least 70 per cent of the gross area of the register. No upper-floor register should be wider horizontally than the wall stack, and it should be placed either in the baseboard or side wall, if this can be done without the use of offsets. First-floor registers may be of the baseboard or floor type, with the former location preferred. High Fig. 2. Influence of Leader Pipe Length on Temperature Loss in Air Flowing through Pipe order to offset the greater temperature losses (Fig. 2) in the longer leader. In gravity circulating systems, this ratio of stack to leader area is a very important matter. The curves in Figs. 4 and 5 indicate that , for rooms having a heat requirement exceeding approximately 9000 Btu. per hr, exceedingly.high register temperatures are required for stacks whose width is less than 3J4 in. For such requirements either multiple stacks, or stacks having larger. cross-sectional area (placed in 6 in. studding-spaces) will be required. 414 Fig. 3. Relative Heating Effect of Stacks at Constant Heat Input to Furnace NoU.--Exterior surface of all ducts is bright tin except at joints where asbestos sealing strips are used. sidewall locations for warm air registers in gravity circulating systems are not recommended on account of the tendency for stratification of the air in the room, resulting in high temperatures at the ceiling. RECIRCULATING DUCTS AND GRILLES The ducts through which air is returned to the furnace should be designed to minimize friction and turbulence. They should be of ample area, in excess of the total area of warm-air pipes, and at all points where 415