7
Venting Options
The furnace can be installed as either direct vent or nondirect
vent units.
For either type of installation, special venting considerations
must be followed. See “Determine Vent Pipe Direction” for the
type of furnace and venting being installed.
Direct Vent
A direct vent (two pipe) installation requires that all the air
necessary for combustion be supplied from outside the dwelling
through an air intake pipe.
Nondirect Vent
A nondirect vent (one pipe) installation uses air from inside the
dwelling for combustion.
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The furnace is shipped with the air inlet pipe terminated to the
top panel for either inside or outside combustion air. An inlet
air restrictor plate is supplied with this furnace and can be
found in the plastic bag containing these Installation
Instructions and the User’s Information Manual.
■
For installations using inside air for combustion (nondirect
vent), attach a 90° elbow (not supplied) to the inlet coupler
and install the restrictor plate inside the elbow. See
“Nondirect Vent Installation.”
Inlet Air Restrictor Plate
IMPORTANT: The inlet air restrictor plate must be installed in all
nondirect vent systems.
Flue Pipe Screen
A flue pipe screen designed to keep objects out of the flue pipe is
included in the plastic bag.
In all installations, this screen should be installed at the
termination of the flue pipe.
Flue Pipe Screen
IMPORTANT: The flue pipe screen should be installed at the
termination of the flue pipe in all installations.
Unconfined Space
An unconfined space is defined as “a space whose volume is
more than 50 cu. ft (1.4 m
3
) per 1,000 Btu/h 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 air infiltration is sufficient to supply the required
combustion 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 cu. ft (1.4 m
3
) per 1,000 Btu/h of the combined input
rating of all appliances installed in that space.” Use direct vent
method. See “Plan Vent System.”
Contaminated Combustion Air
Excessive exposure to contaminated combustion air will result in
performance related problems. The recommended source of
combustion air is outdoor air.
Outdoor air as the source of combustion air
If the furnace is installed in a confined space, it is recommended
that the necessary combustion air come from the outdoors by
way of an attic, crawl space, air duct, or direct opening.
Outdoor air is required as the source of combustion air when the
indoor air is contaminated with chemical substances and in the
following types of installations:
■
Furnaces installed in commercial buildings
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Furnaces installed in buildings with indoor pools
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Furnaces installed in hobby or craft rooms
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Furnaces installed near chemical storage areas
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Furnaces installed in laundry rooms
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Furnaces installed in hair salons
Indoor air as the source of combustion air
Indoor air as the source of combustion air is acceptable in most
applications if the following guidelines are met:
■
All provisions for indoor combustion air must meet the
requirements for combustion air indicated in the National Fuel
Gas Code, ANSI Z223.1/NFPA 54 (latest edition), and/or any
applicable local codes.
■
If indoor combustion air is used, the air supply to the furnace
should not be exposed to the following substances:
Permanent wave solutions
Chlorinated waxes and cleaners
Chlorine-based swimming pool chemicals
Water softening chemicals
Deicing salts or chemicals
Carbon tetrachloride
Halogen-type refrigerants
Cleaning solvents (such as perchloroethylene)
Printing inks, paint removers, varnishes, etc.
Cements and glues
Antistatic fabric softeners for clothes dryers
Masonry acid washing materials
Chlorinated laundry products
Hydrochloric acid
