Installation & Operation Manual
12
1
Determine boiler location
3. If air is taken from another interior space combined with
the equipment room:
(a) Two spaces on same story: Each of the two openings
specified above should have a net free area of one square
inch for each 1000 Btu/hr (22 cm
2
per kW) of input, but
not less than 100 square inches (645 cm
2
) (see FIG. 1-5).
(b) Two spaces on different stories: One or more openings
should have a net free area of two square inches per 1000
Btu/hr (44 cm
2
per kW).
Figure 1-6_Combustion Air from Outside - Single Opening
DIR #2000528624 00
4. If a single combustion air opening is provided to bring
combustion air in directly from the outdoors, the
opening must be sized based on a minimum free area
of one square inch per 3000 Btu/hr (7 cm
2
per kW). This
opening must be located within 12” (30 cm) of the top of
the enclosure (see FIG. 1-6).
All dimensions based on net free area in square inches. Metal
louvers or screens reduce the free area of a combustion air
opening a minimum of approximately 25%. Check with
louver manufacturers for exact net free area of louvers.
Combustion air requirements are based on the latest edition
of the National Fuel Gas Code, NFPA 54 / ANSI Z223.1; in
Canada refer to the latest edition of CGA Standard CAN/CSA
B149.1. Check all local code requirements for combustion air.
Where two openings are provided, one must be within 12"
(30 cm) of the ceiling and one must be within 12" (30 cm) of
the floor of the equipment room. Each opening must have a
net free area as specified in Table 1B. Single openings shall
commence within 12" (30 cm) of the ceiling. The minimum
dimension of air openings shall not be less than 3" (80 mm).
CAUTION
Under no circumstances should the
equipment room ever be under negative
pressure. Particular care should be taken
where exhaust fans, attic fans, clothes dryers,
compressors, air handling units, etc., may
take away air from the unit.
The result is improper combustion and a non-warrantable,
premature appliance failure.
EXHAUST FANS:
Any fan or equipment which exhausts air
from the equipment room may deplete the combustion air
supply and/or cause a downdraft in the venting system. Spillage
of flue products from the venting system into an occupied
living space can cause a very hazardous condition that must be
corrected immediately.
The combustion air supply must be completely free of any
flammable vapors that may ignite or chemical fumes which
may be corrosive to the appliance. Common corrosive
chemical fumes which must be avoided are fluorocarbons
and other halogenated compounds, most commonly present
as refrigerants or solvents, such as Freon, trichlorethylene,
perchlorethylene, chlorine, etc. These chemicals, when burned,
form acids which quickly attack the heat exchanger, headers,
flue collectors, and the vent system.
