6
Outside air openings shall directly communicate with
the outdoors. When combustion air is drawn from the
outside through a duct, the net free area of each of the
two openings must have twice (2 times) the free area
required for Outside Air/2 Open ings. Table A lists the
re quire ments for the ap pli ance only, additional gas fired
appliances located in the same room will require an
increase in the net free area to supply adequate
com bus tion air for all appliances. Combustion air
require ments are based on the latest edition of the
National Fuel Gas Code, ANSI Z223.1, in Canada refer
to National Standard CAN B149.1 or B149.2. Check all
local code re quire ments for combustion air.
All dimensions are based on net free area in square
inch es. 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. Where two openings are pro vid ed,
one must be within 12" (30 cm) of the ceiling and one
must be within 12" (30 cm) of the floor of the room
where the appliance is installed. Each opening must
have a net free area as specified in Table A. Single
openings shall be located with in 12" (30 cm) of the
ceiling.
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, tricholorethylene,
perchlorethylene, chlorine, etc. These chemicals, when
burned, form acids which quickly attack the heat
exchanger finned tubes, headers, flue collectors, and the
vent system. The result is improper combustion and a
non-warrantable, premature appliance failure.
45,000 12 in
2
15 in
2
100 in
2
75,000 19 in
2
25 in
2
100 in
2
90,000 23 in
2
30 in
2
100 in
2
135,000 34 in
2
45 in
2
135 in
2
180,000 45 in
2
60 in
2
180 in
2
199,999 50 in
2
67 in
2
200 in
2
215,000 55 in
2
74 in
2
224 in
2
225,000 56 in
2
75 in
2
225 in
2
260,000 67 in
2
89 in
2
269 in
2
270,000 68 in
2
90 in
2
270 in
2
315,000 79 in
2
105 in
2
315 in
2
360,000 90 in
2
120 in
2
360 in
2
399,999 100 in
2
133 in
2
400 in
2
500,000 125 in
2
167 in
2
500 in
2
TABLE - A
MINIMUM RECOMMENDED COMBUSTION AIR SUPPLY
Combustion Air Source
Input Outside Air/2 Outside Air/1 Inside Air/2
Btu/hr Openings Opening Openings
Under no circumstances should the room where
the appliance is installed ever be under a
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 appliance.
ƽ CAUTION
