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Horizontal Application
Unit Installed on Platform
clearances.
GAS
ENTRY
VENT
PIPE
See the unit nameplate for
Line contact is permissible
SERVICE PLATFORM
FIGURE 14
WARNING
Improper installation of the furnace can result in
personal injury or death. Combustion and flue 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
fireplace or stove, etc. Fire, explosion, carbon monoxide
poisoning, personal injury and/or property damage could
result.
WARNING
The inner blower 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 filter or rack. A field-pro
-
vided high-velocity filter is required for the unit to operate
properly. Table 1 lists recommended filter sizes.
A filter must be in place any time the unit is operating.
WARNING
If a highefficiency filter is being installed as part of this
system to ensure better indoor air quality, the filter must
be properly sized. Highefficiency filters have a higher
static pressure drop than standardefficiency glass/foam
filters. 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 filter with this system, check the
specifications provided by the filter manufacturer against
the data given in the appropriate Lennox Product
Specifications bulletin. Additional information is provided
in Service and Application Note ACC002 (August 2000).
TABLE 1
Furnace Cabinet
Width
Filter Size
Side Return
Bottom Return
14-1/2”
16 X 25 X 1 (1)
14 X 25 X 1 (1)
17-1/2”
16 X 25 X 1 (1)
16 X 25 X 1 (1)
21”
16 X 25 X 1 (1)
20 X 25 X 1 (1)
24-1/2”
16 X 25 X 1 (2)
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 0.8 inche
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 reflected 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.
Return Air Plenum
NOTE - Return air must not be drawn from a room
where this furnace, or any other gas-fueled appliance
(i.e., water heater), or carbon monoxide- producing
device (i.e., wood fireplace) is installed.
When return air is drawn from a room, a negative pressure
is created in the room. If a gas appliance is operating in
a room with negative pressure, the flue products can be
pulled back down the vent pipe and into the room. This
