Bryant 312AAV - Manual (Page 6)

other flow control must prevent chilled air from entering the
furnace. If the dampers are manually operated, they must be
equipped with means to prevent operation of either unit unless the
damper is in the full-heat or full-cool position.
AIR FOR COMBUSTION AND VENTILATION
Provisions for adequate combustion and ventilation air must be
provided in accordance with Section 5.3 of the NFGC, Air for
Combustion and Ventilation, or applicable provisions of the local
building codes.
Canadian installations must be installed in accordance with NSC-
NGPIC Part 7 and all authorities having jurisdiction.
WARNING: When the furnace is installed in a residen-
tial garage, the burners and ignition sources must be
located at least 18 inches above the floor. The furnace
must be located or protected to avoid damage by vehicles.
When the furnace is installed in a public garage, airplane
hangar, or other building having a hazardous atmosphere,
the furnace must be installed in accordance with the
National Fire Protection Association, Inc. requirements.
CAUTION: Air for combustion must not be contami-
nated by halogen compounds, which include fluoride,
chloride, bromide, and iodide. These elements are found
in aerosol sprays, detergents, bleaches, cleaning solvents,
salts, air fresheners, and other household products.
All fuel-burning equipment must be supplied with air for fuel
combustion. Sufficient air must be provided to avoid negative
pressure in the equipment room or space. A positive seal must be
made between the furnace cabinet and the return-air duct to
prevent pulling air from the burner area and from blocked vent
safeguard opening.
CAUTION: The operation of exhaust fans, kitchen ven-
tilation fans, clothes dryers, or fireplaces could create a
NEGATIVE PRESSURE CONDITION at the furnace.
Make-up air MUST be provided for the ventilation
devices, in addition to that required by the furnace.
The requirements for combustion and ventilation air depend upon
whether the furnace is located in an unconfined or confined space.
I. UNCONFINED SPACE
An unconfined space has a volume of at least 50 cu ft for each
1000 Btuh total input for all appliances (furnaces, clothes dryers,
water heaters, etc.) in the space.
For example:
If the unconfined space is constructed unusually tight, air for
combustion and ventilation must come from either the outdoors or
spaces freely communicating with the outdoors. Combustion and
ventilation openings must be equivalent to those used for a
confined space (defined below). Return air must not be taken from
the room unless an equal or greater amount of air is supplied to the
room.
II. CONFINED SPACE
A confined space has a volume less than 50 cu ft per 1000 Btuh
of total input ratings of all appliances installed in that space. A
confined space must have provisions for supplying air for com-
bustion, ventilation, and dilution of flue gases using 1 of the
following methods in Table 2 and Fig. 7and 8.
NOTE: When determining the free area of an opening, the
blocking effect of louvers, grilles, and screens must be considered.
If the free area of the louver or grille design is unknown, assume
wood louvers have a 20 percent free area and metal louvers or
grilles have a 60 percent free area. Screens must not be smaller
than 1/4-in. mesh. Louvers and grilles must be constructed so they
cannot be closed.
The opening size depends upon whether air comes from outside of
the structure or an unconfined space inside the structure.
1. Air from inside the structure requires 2 openings (for
structures not of unusually tight construction):
a. Each opening must have a minimum free area of not less
than 1 sq in per 1000 Btuh of total input rating for all gas
utilization equipment in the confined space, but not less
than 100 sq in. The minimum dimension of air openings
should be no smaller than 3 in. (See Table 2 and Fig. 7
and 8).
b. If building construction is unusually tight, a permanent
opening directly communicating with the outdoors shall
be provided. (See next section).
c. If the furnace is installed on a raised platform to provide
a return-air plenum, and return air is taken directly from
the hallway or space adjacent to furnace, all air for
combustion must come from outdoors.
2. Air from outside the structure requires 1 of the following:
a. If combustion air is taken from outdoors through 2
vertical ducts, the openings and ducts must have at least
1 sq in. of free area per 4000 Btuh of total input for all
equipment within the confined space. (See Fig. 8 and
Table 2.)
b. If combustion air is taken from outdoors through 2
horizontal ducts, the openings and ducts must have at
least 1 sq in. of free area per 2000 Btuh of total input for
all equipment within the confined space. (See Fig. 8 and
Table 2.)
c. If combustion air is taken from the outdoors through a
single opening or duct (horizontal or vertical) commenc-
ing within 12 in. of the top of the confined space, the
opening and duct must have at least 1 sq in. of free area
Fig. 6–Location to Burners
A93044
18-IN. (457.2 mm)
MINIMUM TO BURNERS
TABLE 1–312AAV FLOOR AREA
312AAV FURNACE
INPUT (BTUH)
MINIMUM WITH
7–1/2 FT CEILING (SQ. FT.)
88,000 587
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