scope:

This standard applies to automatically operating gas-fired central furnaces (see Part XI, Definitions), hereinafter referred to as furnaces, for installation in residential, commercial, and industrial structures including furnaces for Direct Vent, Recreational Vehicle, Outdoor, and Manufactured (Mobile) Homes.

These furnaces may include a cooling unit. All units shall be constructed entirely of new, unused parts and materials.

In Canada, this standard applies to gas-fired central furnaces having inputs up to and including 400,000 Btu per hour (117 228 W).

This standard applies to Category I, Category II, Category III and Category IV Central Furnaces (see Part XI, Definitions).

This standard applies to furnaces of the types defined in Part XI, Definitions, which are designed to supply heated air through ducts to spaces remote from or adjacent to the furnace location. Location and use of such furnaces with respect to the spaces being heated necessitates automatic operation of the appliance.

This standard covers the thermal efficiency (2.39, Thermal Efficiency) and related markings of only those furnaces whose efficiencies are not regulated in the U.S.A. by the Energy Policy Act and Conservation Act of 1975 and the National Energy Conservation Policy of 1978(Footnote *) or not covered in Canada by Exhibit K (K.1.1), when connected to single phase electrical supply.

A furnace of a type not specifically defined in this standard may be subjected to such examination and tests as deemed necessary by the testing agency to determine compliance with the intent of this standard.

This standard also applies to a furnace which is factory equipped with both a draft hood and an automatic vent damper device (see Part XI, Definitions), hereinafter referred to as vent damper device.

Unless otherwise indicated on its rating plate, a furnace shall be for installation indoors in accordance with its markings and the manufacturer's installation instructions. When specified additional or alternate provisions are met, a furnace may be for manufactured (mobile) home installation or for use outdoors.