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Unconfined Space
An unconfined space is defined as “a space whose volume
is more than 50 cubic feet per 1000 BTU per hour of the
combined input rating of all appliances installed in that
space.” When a furnace is installed in an unconfined space
in a building, it can be assumed that the infiltration will be
sufficient to supply the required air. If the furnace is
installed in a ventilated attic or crawl space, it is assumed
that the infiltration is sufficient to supply the required air.
However, in a building of unusually tight construction,
additional outdoor air should be provided.
Confined Space
A confined space is defined as “a space whose volume is
less than 50 cubic feet per 1000 BTU per hour of the
combined input rating of all appliances installed in that
space.”
Confined Space Installation/Air from Inside Structure
If the furnace is installed in a confined space within the
building and combustion air is taken from a heated space,
the combustion air and ventilating air must enter and leave
the space through two permanent openings of equal area.
One opening shall be located within 12" of the ceiling and
the other within 12" of the floor, each having a free area of
1 square inch per 1000 BTU/HR of total input rating of all
appliances within the space and not less than 100 square
inches each (see Figure 3).
Confined Space Installation/Air from Outside Structure
If air from outside is brought in for combustion, the confined
space shall be provided with two permanent openings. One
opening shall be within 12" of the ceiling and one opening
within 12" of the floor. Several methods can be used to bring
the outside air in through these openings. The openings
shall open directly or by ducts with the outdoors, through
spaces (crawl space or attic) that freely open to the out-
doors, or indirectly through vertical ducts (see Figures 4 and
5). If any of these methods are used, each opening shall
have a free area of 1 square inch per 4000 BTU/HR of the
total input rating of all appliances within the enclosure.
Do not use the furnace as a heater in a
building under construction. The furnace can
be severely damaged due to the abnormal
environment caused by construction. Chlo-
rides from sources such as paint, stain, or
varnish; tile and counter cements; adhesives;
and foam insulation are abundant in a struc-
ture under construction and can be highly
corrosive. Low return air temperature can
cause condensation in the furnace and other
damage that can shorten the life of the unit.
CAUTION
G1N80BR, G1N80BT, CG80RB, and CG80TB models may
be installed as suspended units in the horizontal position.
These furnaces are not designed for direct attachment of
suspension rods to the furnace casing.
The suspending means must be field fabricated, and
should consist of two “cradles” made by attaching two rods
to a length of angle iron or suitable gage steel. Locate the
cradles so that they are as close as possible to the ends
of the furnace (this will provide access for removal of
major components such as the blower assembly). Provide
enough clearance between the suspension rods and the
furnace to allow removal of access panels.
Combustion and Ventilation Air
Adequate provisions for combustion air and ventilation of
furnace must be made. Refer to Section 5.3, “Air for
Combustion and Ventilation,” of the National Fuel Gas
Code, ANSI Z223.1/NFPA54 (latest edition), Sections 7.2,
7.3, or 7.4 of CSA B149.1 Natural Gas and Propane
Installation Codes (latest editions), or applicable provi-
sions of the local building codes.
Air openings in the front of the furnace must
be kept free of obstructions. Any obstruction
may cause improper operation that can result
in a fire hazard or carbon monoxide injury.
WARNING
Figure 3
Note: Each opening shall have a free area of at least one square
inch per 1000 BTU per hour of the total input rating of all
equipment in the enclosure, but not less than 100 square
inches.
Water
Heater
Chimney or
Gas Vent
Openings
Furnace
Equipment in Confined Space
All Air From Inside
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