All installations and services must be performed by qualified service personnel.
2.The return air opening may be located in the top, the center or (ideally) the bottom of the closet door, or side wall.
: Do not obstruct any return air openings, including the return grille on the furnace. To do so may cause the furnace to activate the high temperature limit and shutdown, or it may cause asphyxiation.
3.The
4.The total free area of openings in the floor or ceiling registers serving the return air duct system must be at least 350 square inches. At least one register must be located where it is not likely to be covered by carpeting, boxes, furniture, or any other objects.
5.Materials located in the return duct system must have a flame spread classification of 200 or less.
6.Pans made of a
7.Wiring materials located in the return air duct system must conform to Article
8.Gas piping shall not be located in, or extend through, the return air duct system.
9.Refer to section G. COMBUSTION AIR for additional combustion air requirements.
G. COMBUSTION AIR
The furnace requires the proper amount of combustion air be available to combust the fuel cleanly and efficiently. An inadequate combustion air supply can result in unsafe and erratic operation of the burner, sooting of the combustion chamber and the heat exchanger, and possibly, offensive fuel odors. The combustion air intake must provide an adequate source of combustion air to the appliance. Refer to part 5.3 of the National Fuel Gas Code, ANSI Z223.1 / NFPA
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