12
3. When the furnace is installed on a fac-
tory or site-built cased air conditioning
coil, the sub-base is not necessary.
However, the plenum attached to the
coil casing must be installed such that its
surface is at least 1” from combustible
material in Figure 6.
VENTING AND COMBUSTION
AIR REQUIREMENTS
General
Provisions must be made in the installation of
this furnace to provide an adequate supply of air
for combustion. Detailed instructions for deter-
mining the adequacy of an installation can be
found in the current revision of the National Fuel
Gas Code (ANSI Z223.1 / NFPA54) or in appli-
cable local building codes.
Consult local codes
for special requirements
. For Canadian in-
stallations consult Canadian Installations Codes
and (CAN/CGA B149.1 or .2).
If the furnace is operated with inadequate air for
combustion one of the flame roll-out switches
located in the burner compartment or the vent
switch will open, turning off the gas supply to the
burners. These safety devices are manually
reset switches. DO NOT install jumper wires
across these switches to defeat their function.
DO NOT reset a switch without identifying and
correcting the fault condition. If a switch must be
replaced, use only the correct part specified in
the Replacement Parts List.
Air openings in the furnace door, warm air
registers, and return air grilles must not be
restricted.
When determining combustion air space,
the full rate input of this two-stage furnace
must be used.
Combustion Air Quality
To maximize heat exchanger life, the combus-
tion air must be free of chemicals which form
corrosive acidic compounds in the combustion
gases. The recommended source of combus-
tion air is to use the outdoor air supply. How-
ever, 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 combus-
tion 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
Out-
door 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 perchloroethyl-
ene)
• Printing inks, paint removers, varnishes,
etc.
• Hydrochloric acid
• Cements and glues
• Antistatic fabric softeners for clothes dryers
• Masonry acid washing materials
! CAUTION:
Combustion air must not be drawn from
a corrosive atmosphere.
! WARNING:
Furnace installation using methods other
than those described in the following
sections must comply with the National
Fuel Gas Code and all applicable local
codes to provide sufficient combustion
air for the furnace.
Installation In An Unconfined Space
An unconfined space is an area including all
rooms not separated by doors with a volume
greater than 50 cubic feet per 1,000 Btuh of the
combined input rates of all appliances which
draw combustion air from that space. For ex-
ample, a space including a water heater rated
at 45,000 Btuh input and a furnace rated at
75,000 Btuh requires a volume of 6,000 cubic
feet [50 x (45 + 75) = 6,000] to be considered
Summary of Contents for TA-060C-08A
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