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CAUTION
If this unit is being installed in a space serviced by an
exhaust fan, power exhaust fan, or other device which
may create a negative pressure in the space, take care
when sizing the inlet air opening. The inlet air opening
must be sized to accommodate the maximum volume
of exhausted air as well as the maximum volume of
combustion air required for all gas appliances serviced
by this space.
Horizontal Application
Unit Installed on Platform
clearances.
GAS
ENTRY
VENT
PIPE
See the unit nameplate for
Line contact is permissible
SERVICE PLATFORM
Figure 13
WARNING
Improper installation of the furnace can result in
personal injury or death. Combustion and ue products
must never be allowed to enter the return air system or
the living space. Use screws and joint tape to seal the
return air system to the furnace. In platform installations
with bottom return air, the furnace should be sealed
airtight to the return air plenum. A door must never be
used as a portion of the return air duct system. The
base must provide a stable support and an airtight seal
to the furnace. Allow absolutely no sagging, cracks,
gaps, etc. The return and supply air duct systems must
never be connected to or from other heating devices
such as a replace or stove, etc. Fire, explosion,
carbon monoxide poisoning, personal injury and/or
property damage could result.
WARNING
The blower access panel must be securely in place
when the blower and burners are operating. Gas
fumes, which could contain carbon monoxide, can be
drawn into living space resulting in personal injury or
death.
Filters
This unit is not equipped with a lter or rack. A eld-pro-
vided high-velocity lter is required for the unit to operate
properly. Table 1 lists recommended lter sizes.
IMPORTANT
If a highefciency lter is being installed as part of this
system to ensure better indoor air quality, the lter must
be properly sized. Highefciency lters have a higher
static pressure drop than standardefciency glass/foam
lters. If the pressure drop is too great, system capacity
and performance may be reduced. The pressure drop
may also cause the limit to trip more frequently during
the winter and the indoor coil to freeze in the summer,
resulting in an increase in the number of service calls.
Before using any lter with this system, check the
specications provided by the lter manufacturer
against the data given in the appropriate Lennox
Product Specications bulletin. Additional information
is provided in Service and Application Note ACC002
(August 2000).
A lter must be in place any time the unit is operating.
TABLE 1
Furnace Cabinet
Width
Filter Size
Side Return Bottom Return
A - 14-1/2” 16 X 25 X 1 (1) 14 X 25 X 1 (1)
B - 17-1/2” 16 X 25 X 1 (1) 16 X 25 X 1 (1)
C - 21” 16 X 25 X 1 (1) 20 x 25 x 1 (1)
D - 24-1/2” 16 X 25 X 1 (1) 24 x 25 x 1 (1)
Duct System
Use industry-approved standards (such as those pub-
lished by Air Conditioning Contractors of America or Amer-
ican Society of Heating, Refrigerating and Air Condition-
ing Engineers) to size and install the supply and return
air duct system. This will result in a quiet and low-static
system that has uniform air distribution.
NOTE - Do not operate the furnace in the heating mode
with an external static pressure that exceeds 0.5 inches
w.c. Higher external static pressures may cause erratic
limit operation.
Supply Air Plenum
If the furnace is installed without a cooling coil, a remov-
able access panel must be installed in the supply air duct.
The access panel should be large enough to permit in-
spection (either by smoke or reected light) of the heat
exchanger for leaks after the furnace is installed. The
furnace access panel must always be in place when the
furnace is operating and it must not allow leaks into the
supply air duct system.
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