Document 93mON24mOemB27bjD6JkLBdE5

American Society of Heating and Ventilating Engineers Guide, 1932 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 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 order to offset the greater temperature losses (Fig, 2) in the longer leader. In gravity circulating systems, this stack to leader area ratio is a very important consideration. Specific data for a great variety of cases are presented in Figs. 4 and 5 and the designer should check the stack to leader com binations with the nearest comparable case as shown in these figures. Any second floor stack supplying heat to a room whose heat loss is 9,000 Btu or above (see Figs. 4 and 5 which show that high temperatures are necessary if rooms of more than 9,000 Btu requirement are heated by one stack each in 4-in. studding), should be run within 6-in. studded walls or should have multiple stacks. Stack sections, wherever possible, should be changed from the thin rectangular to the more nearly square shape. REGISTER AREA The registers used for discharging warm air into the rooms should have 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. 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, the air stream must change direction or shape, streamline fittings should be employed. Horizontal ducts should pitch at least one-half inch per foot upward from the furnace. The recirculating grilles (or registers) should have a free area at least equal to the ducts to which they connect, and their free area shoukF never be less than 50 per cent of their gross area. The location and number of return grilles will depend on the size, details and exposure of the house. Small compactly built houses may frequently be adequately served by a single return effectively placed in a central hall. More often it is desirable to provide two or more returns, provided; however, that in two-story residences one return must be* placed to effectively receive the cold air returning by way of the stairs. Where a divided system of two or more returns is used the grilles must be placed to serve the maximum area of cold wall or windows. 86 Chapter 5--Gravity Warm Air Heating Systems Thus in rooms having only small windows the grille should be brought as closer to the furnace as possible, but if the room has a bay window, Q0W6 < -J nu z CO n Of<Hcd C/5 (&oA 2 :> oos b in 0W6 U c3w* H wubCM,.J o z H <w X 40 o french, doors, or other large sources of cooling and leaking of cold air, the grille should be placed close by, so as to collect the cool air and 87