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Section G2442 (618) Forced-Air Warm-Air Furnaces
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Forced-air warm-air furnaces shall be tested in accordance with ANSI Z21.47/CSA 2.3 or UL 795 and shall be installed in accordance with the manufacturer's instructions.
Outdoor or return air for forced-air heating and cooling systems shall not be taken from the following locations:
- Closer than 10 feet (3048 mm) from an appliance vent outlet, a vent opening from a plumbing drainage system or the discharge outlet of an exhaust fan, unless the outlet is 3 feet (914 mm) above the outside air inlet.
- Where there is the presence of objectionable odors, fumes or flammable vapors; or where located less than 10 feet (3048 mm) above the surface of any abutting public way or driveway; or where located at grade level by a sidewalk, street, alley or driveway.
- A hazardous or insanitary location or a refrigeration machinery room as defined in the International Mechanical Code.
- The appliance is a direct-vent appliance or an appliance not requiring a vent in accordance with Section G2425.8.
- 2.1. The return air shall be taken from a room or space having a volume exceeding 1 cubic foot for each 10 Btu/h (9.6 L/W) of combined input rating of all fuel-burning appliances therein.
- 2.2. The volume of supply air discharged back into the same space shall be approximately equal to the volume of return air taken from the space.
- 2.3. Return-air inlets shall not be located within 10 feet (3048 mm) of a draft hood in the same room or space or the combustion chamber of any atmospheric burner appliance in the same room or space.
- Rooms or spaces containing solid fuel-burning appliances, provided that return-air inlets are located not less than 10 feet (3048 mm) from the firebox of such appliances.
- Where return air intakes are located not less than 10 feet (3048 mm) from cooking appliances and serve only the kitchen area, taking return air from a kitchen area shall not be prohibited.
- Dedicated forced-air systems serving only a garage shall not be prohibited from obtaining return air from the garage.
- A crawl space by means of direct connection to the return side of a forced-air system. Transfer openings in the crawl space enclosure shall not be prohibited.
Required outdoor air inlets shall be covered with a screen having 1/4-inch (6.4 mm) openings.