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American Society of Heating and Ventilating Engineers Guide, 1929 All such pipes shall be braced in a proper manner so as not to obstruct the flow of air but to retain the full capacity throughout. All joints shall be locked and held in ])lace by means of lugs, or straps. No joint shall depend wholly upon solder to make it tight. b. Double Stacks. All double wall stacks or wall pipes, heads, boots, ells, tees, angles and other connections shall be made of bright tin, not lighter than IC or galvanized iron and shall be made double, from and including the boot or foot piece in basement to the top of each and every stack and register head on all floors. There shall be con tinuous uniform air space of not less than five-sixteenths (A*) of an inch, which must be maintained between the outer and inner walls of all such pipes and fittings of all kinds, styles and descriptions; such pipes, heads, boots and. other fittings to be of the styles, or equal to those accepted by the National Board of Fire Underwriters. All stacks and fittings either single or double must be secured firmly in place by lugs or straps attached to the outer walls of stacks and fittings, and no nails shall be driven through these stacks or fittings at any point. No lugs or straps shall be formed by cutting holes in outer walls of stacks or fittings. No wall pipes or fittings shall be used which depend wholly on soldered joints. The various members shall be so made that all joints are locked or soldered and the several members shall be attached to each other with slip joints, which are, for the purpose intended, air-tight. c. Where stacks, heads, boots or other fittings, whether double or single, go through the first floor, all openings around such heads, boots, stacks or fittings must be .filled with asbestos cement or other incombustible material to make the openings gas and dust-tight. Registers Section 7. a. When baseboard or wall registers are used, they shall be properly and permanently attached to the stack head in such a manner that will prevent any leakage of air between the head and the register. b. Floor registers shall be provided either with register borders, or double register boxes of tin or galvanized iron with an air space of not less than five-sixteenths (A*) of an inch between inner and outer boxes. c. Registers for warm air and warm-air pipes shall not be located in outside walls. d. Any furnace system having not more than two warm-air registers, at least one of the registers shall be without valve or louvers and the pipe thereto shall be without damper. Air Supply to. Furnace Section 8. a. The air supply to furnace for warm-air heating plants may be taken from outside or from within the building or may be taken partially from outside and partially from within. In no case, however, shall air be supplied to any furnace from any basement or furnace room not occupied as living quarters. b. The cold air intake or return where air is taken from within the building shall have a net area throughout its entire length of not less than the combined net area of all warm-air pipes leading from the furnace. This may be maintained in one or more ducts. No reverse incline or air trap will be allowed in any section thereof. c. When the cold air supply is taken wholly from the outside of the building the supply duct at its most contracted area must equal or exceed eighty per cent (80%) of the combined area of all warm-air pipes leading from the furnace. . d. Cold air ducts shall be constructed of metal, tile or other incombustible material having smooth inner surface and shall maintain a constant net area throughout their entire length and shall be made dust-tight.. Horizontal return ducts shall have at least 10 per cent greater area than vertical connecting pipes. Where a boot or shoe is connected to the casing at the base, the opening shall not extend higher than a line on the level of the grate of the furnace. The width of the shoe shall be of proper measure ment to make the area at least equal to that of the round or square pipe to which it is connected. e. Wherever the space between joists is used to convey cold air over head, the joists and all wooden surfaces between such joists shall be lined with metal and a sheet metal pan constructed to extend not less than two inches (2') below said joists. The con nection from this pan to the boot or shoe shall be made of galvanized iron not lighter 186 Chapter VIII--Gravity Warm-Air Furnace Heating than No. 26 U. S. standard gauge, and shall have a transition collar, the top area of which shall be at least 10 per cent greater than the area of the connecting pipe. /. When it is necessary to set the furnace over a pit and connect up cold air under the basement floor, such pit or cold air trench shall not exceed eighteen inches (18") in depth below the casing ring and the width of the trench or trenches shall be of proper measurement to make the area at least equal, to the pipe to which it is connected. The connection between the cold air pipe or duct and the underground pit shall be made with converse transition joint as described in Article IV, Section 8 (b) and (d). g. The cold air face or faces shall be made of wood, or metal. When set in floors the top of same shall be flush with,floor. Where cold air face is placed in a seat or side wall (whether furnished by owner, general contractor or furnace contractor) the open work of face must extend to within at least one inch (1") of the floor line. The free area of cold air faces shall be at least equal to the free area of the duct or ducts to which they are connected. h. The effective area of a vertical cold air face lies within fourteen inches (14") of the floor line, hence, the capacity of any vertical cold air face shall be determined by multiplying the base line in inches by not to exceed fourteen inches (14") in height and deducting for the grilles or cross bars. *' When a fan is installed in the air supply duct of a gravity system the same net area of all ducts shall be maintained as calculated under Article 3, Sections 1,2 and 3 and Article 4, Section 8-(b). Smoke Pipes Section 9. a. The smoke pipe shall be as short and direct as consistent with the location of the furnace. It shall be made of metal not lighter than No. 24 U. S. standard gauge, and not less than the full size of the collar on the furnace throughout its entire length. It must have no opening for attaching any fireplace, stove, range, water heater, gas or ventilating connection. It shall be lock seamed or riveted; all joints shall lap not less than one and one-half inches (1M") and it shall be rigidly secured. Cast iron smoke pipe may be used. . b. All smoke pipes shall be provided with check dampers, placed on the side of the pipe or at the end of a .tee; when cast iron smoke pipe dampers are used they must be placed between the check damper and the furnace and supported .on both sides of the pipe. c. Where the smoke pipe enters the flue, a thimble shall be cemented into the flue and the connections thereto made air-tight. Should any smoke pipe come within eighteen inches (18") of any combustible material, such combustible material must be covered with asbestos paper and a metal shield so fastened that a two inch air space exists between this shield and the combustible material. This shield shall be no less in size than twice the diameter of the smoke pipe and of sufficient length to cover the combustible material at all points. . d. No smoke pipe shall project through any external wall or window. No furnace connection is to be made to a flue without a cast iron or steel cleanout having first been provided in the flue (not more than eight inches (8") below the smoke pipe opening). The base of the flue shall be filled up to the bottom of the cleanout, all of which must be made air-tight. Pipeless or One-Pipe Furnaces Section 10. a. When but one duplex grating is used for both warm air and cold air in a so-called pipeless furnace, the area of the cold air intake shall be at least equal to the area of the warm-air outlet of the grating. Art. 4, Sec. 4, relative to casing shall not govern when this type of furnace is installed, but the following specification shall be followed; The inner and outer casing of this type of furnace may be made of either black or galvanized iron.not lighter than No. 26 U. S. standard gauge. -A uniform air space shall be maintained at all points between the inner and outer casing. In no case shall the top of the heater be allowed closer than twelve inches (12") to any ceiling or joists above the furnace. b. Where joists are cut. to accommodate this furnace, headers shall be put in and braced. c. Art. 3 for determining area of warm-air pipe shall not govern in figuring a pipeless furnace. B 187