All installations and services must be performed by qualified service personnel.
4.The total free area of openings in the floor or ceiling registers serving the return air 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 air system must have a flame spread classification of 200 or less.
6.Wiring materials located in the return air duct system must conform to Article
7.Gas piping shall not be located in, or extend through, the return air duct system.
8.Refer to section G. COMBUSTION AIR for additional combustion air requirements.
G. COMBUSTION AIR
CAUTION: Flexible, spiral, or corrugated duct is not recommended, due to the relatively
The furnace requires the proper amount of combustion airflow through the combustion air intake 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. Refer to chapter 5.3 of the National Fuel Gas Code, ANSI Z223.1 / NFPA
The preferred location of the outside combustion air intake terminal (e.g. an optional stainless steel intake hood, part no. AOPS7402) is through the side of the structure, skirting, or enclosure. An acceptable alternate location is under the structure in the skirted or crawlspace area providing a minimum of 50 square inches of free area exists around the perimeter for outside combustion air to be drawn through. The opening of the termination must be at least 7 inches below the top of the floor.
The
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