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designed to burn solid fuel. If the furnace vent is
to be connected to a chimney serving a fireplace,
the fireplace must be sealed off from the chimney.
Single wall metal vents shall not be used for
Category I venting. Category I furnaces
must be vented vertically or near vertically.
For Category I furnace installations, the furnace
shall be connected to a factory built chimney or
vent complying with a recognized standard, or
a masonry or concrete chimney lined with a
lining material acceptable to the authority having
jurisdiction. Venting into an unlined masonry
chimney or concrete chimney is prohibited.
The furnace vent, if metal, may be insulated if
local codes allow. Any part of the vent system,
metal vent only, not exposed to weather, but
which are exposed to ambient temperatures
below 35° F must be insulated to prevent
condensation. All vent insulation shall be foil
backed fiberglass of one inch minimum
thickness.
Three sheet metal fasteners (field supplied)
should be used to secure the vent pipe to the
furnace flue. These fasteners should be evenly
spaced around the flue diameter, if possible.
Combustion Air Quality
The recommended source of combustion air is
to use the outdoor air supply. However, the use
of indoor air in most applications is acceptable
except as follows:
1. If the furnace is installed in a confined
space it is recommended that the necessary
combustion air come from the outdoors by
way of attic, crawl space, air duct, or direct
opening.
2. If outdoor combustion air is used, there
must be no exposure to the installations or
substances listed in Item 3 below.
3. The following types of installation may
require Outdoor Air for combustion, due
to chemical exposures:
• Commercial buildings
• Buildings with indoor pools
• Furnaces installed in laundry rooms
• Furnaces installed in hobby or craft
rooms
• Furnaces installed near chemical storage
areas
Exposure to the following substances in
the combustion air supply may also require
Outdoor Air for combustion:
• Permanent wave solutions
• 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
• Cements and glues
• Antistatic fabric softeners for clothes
dryers
• Masonry acid washing materials
Category I - Common Venting
When an existing furnace is removed from a
venting system serving other appliances, the
venting system is likely to be too large to properly
vent the remaining appliances. An improperly
sized venting system can result in the formation
of condensate, leakage, spillage, etc.
The venting system should be designed to have
the minimum number of elbows or turns. All
horizontal runs shall be sloped upwards from
the furnace at 1/4 inch per running foot of vent.
Supports for the vent pipe must be installed a
minimum of every five feet along the vent run to
ensure no displacement after installation.
Under no circumstances shall any portion of the
vent system extend into or pass through any
return air duct, supply air duct, or plenum.
If the furnace is operated with blocked or restricted
venting, the burner roll-out limit switch will open,
turning off the gas supply to the burners. The roll-
out limit switch is a manually reset device. DO
NOT install a jumper wire across this switch to
defeat its function. DO NOT reset the switch
without identifying and correcting the fault
condition which caused the switch to trip. If this
switch must be replaced, use only factory-
approved replacement parts.
!
WARNING:
Upon completion of the furnace
installation, carefully inspect the entire
flue system both inside and outside the
furnace to assure it is properly sealed.
Leaks in the flue system can result in
serious personal injury or death due to
exposure of flue products, including
carbon monoxide.
