1.1 SCOPe 1.1.1 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. 1.1.2 In Canada, this standard applies to gas-fired central furnaces having
inputs up to and including 400,000 Btu per hour (ll7 228 W). 1.1.3 This standard applies to Category I, Category II, Category III and
Category IV Central Furnaces (see Part XI, Definitions). 1.1.4 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. 1.1.5 This standard covers the thermal efficiency (2.38) 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* or not covered in Canada by Exhibit M (M1.1), when
connected to single phase electrical supply. 1.1.6 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. 1.1.7 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. 1.1.8 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. 1.1.9 A furnace for manufactured (mobile) home installation shall be designed
so when installed in accordance with the manufacturer's installation
instructions supplied with the furnace, it shall provide complete separation of
its combustion system from the living space of the manufactured (mobile) home. The complete separation of the furnace combustion system from the living space
of the manufactured (mobile) home is accomplished by the furnace being designed
and installed so (1) all air supplied for combustion, (2) the combustion system
of the furnace and (3) all products of combustion are completely isolated from
the living space. Doors, panels and any other access openings of the structure
serving an enclosure required for such isolation are to communicate only to the
outdoors. A furnace which by its inherent design provides such complete
separation is referred to as a direct vent central furnace (see Part XI,
Definitions). 1.1.10 A furnace shall be for use with one or more of the gases specified in
2.1.1 A furnace for manufactured (mobile) home installation shall be
convertible for use with natural gas and liquefied petroleum gases. 1.1.11 Special construction provisions applicable to Category II, III, or Iv
furnaces are outlined under 1.1.10, 1.2.23, 1.2.24, 1.14, 1.15.15 through
1.15.17, 1.23.1, -c13, -c16, -d4, and -d5, 1.24.2-i and -j, 1.25.2-d and
1.25.9-f. 1.1.12 A furnace for indoor installation designed to vent the flue gases
horizontally through an outside wall shall be specified as Category III or IV,
except Category I furnaces utilizing a listed mechanical venter applied
externally to the venting system. 1.1.13 Special construction provisions applicable to a furnace for
manufactured (mobile) home installation are outlined under 1.1.8, 1.1.9,
1.1.10, 1.2.22, 1.6.5, 1.11.17, 1.23.1-c4, 1.23.5, 1.25.2-f, 1.25.9-b and
1.25.9-h and Part III. 1.1.14 Special construction provisions