Installation guide

The minimum clearances to combustion construction MUST be
maintained between the furnace and adjacent construction, as
shown in Figure 1.
In addition to clearances in Figure 1, clearance for the vent pipe
must be considered.
A su bbase for combustible floors MUST be used when the furnace
is installed on combustible material. See "9. DuctworkandFilter't
GAS SUPPLY
Typical Downflow Installation
RETURN
AIR
SUPPLY
AIR
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3. Combustion & Ventilation Air
CARBON MONOXIDE POISONING HAZARD.
evaluated carefully as it may be necessary to provide outdoor air
for combustion.
Failure to provide adequate combustion and
ventilation air could result in death or personal
injury.
Use methods described here to provide
combustion and ventilation air.
Furnaces require ventilation openings to provide sufficient air for
proper combustion and ventilation of flue gases. All duct or open-
ings for supplying combustion and ventilation air must comply with
the gas codes, or in the absence of local codes, the applicable na-
tional codes.
Combustion and ventilation air must be supplied in accordance
with one of the following:
1. Section 8.3, Air for Combustion and Ventilation, of the National
Fuel Gas Code, (NFGC), ANSI Z223.1-2002/NFPA 54-2002
in the U.S.,
2. Sections 7.2, 7.3, 7.5, 7.6, 7.7, and 7.8 of National Standard of
Canada, Natural Gas and Propane Installation Code
(NSCNGPIC), CSA B149.1-05 in Canada,
3. Applicable provisions of the local building code.
• Commercial buildings.
• Buildings with indoor pools.
• Furnaces installed in laundry rooms.
• Furnaces installed in hobby or craft rooms.
• Furnaces installed near chemical storage areas.
• Permanent wave solutions for hair.
• Chlorinated waxes and cleaners.
• Chlorine based swimming pool chemicals.
• Water softening chemicals.
• De-icing salts or chemicals.
• Carbon tetrachloride.
• Halogen type refrigerants.
• Cleaning solvents (such as perchloroethylene).
• Printing inks, paint removers, varnishes, etc.
• Hydrochloric acid.
• Sulfuric Acid.
• Solvent cements and glues.
• Antistatic fabric softeners for clothes dryers.
• Masonry acid washing materials.
Outdoor Combustion Air Method
A space having less than 50 cubic feet per 1,000 BTUH input rating
for all gas appliances installed in the space requires outdoor air for
combustion and ventilation.
When the installation is complete, check that all appliances have
adequate combustion air and are venting properly. See Venting
And Combustion Air Check in "4. Gas Vent Installation "Section in
this manual.
Air Openings and Connecting Ducts
1. Total input rating for all gas appliances in the space MUST be
considered when determining free area of openings.
Contaminated Combustion Air
Installations in certain areas or types of structures could cause ex-
cessive exposure to contaminated air having chemicals or halo-
gens that will result in safety and performance related problems
and may harm the furnace. These instances must use only out-
door air for combustion.
The following areas or types of structures may contain or have ex-
posure to the substances listed below. The installation must be
2. Connect ducts or openings directly to the outdoors.
3. When screens are used to cover openings, the openings
MUST be no smaller than 1/4" mesh.
4. The minimum dimension of air ducts MUST NOT be less than
3 _ .
When sizing a grille, louver, or screen use the free area of
opening. If free area is NOT stamped or marked on grill or lou-
ver, assume a 20% free area for wood and 60% for metal.
Screens shall have a mesh size not smaller than 1/4".
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