507324-01B
Page 10 of 32
Issue 1809
Figure 12. Typical Horizontal Application Unit
Suspended in Attic or Crawlspace
Return Air - Horizontal Applications
Return air must be brought in through the end of a furnace
installed in a horizontal application. The furnace is equipped
with a removable bottom panel to facilitate installation. See
Figure 13. Horizontal Application Unit installed on
Platform
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.
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
Filters
This unit is not equipped with a filter or rack. A field provided
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.
Furnace Cabinet
Width
Filter Size
Side Return
Bottom Return
A - 14-1/2”
16 x 25 x 1
14 x 25 x 1
B - 17-1/2”
16 x 25 x 1
C - 21”
20 x 25 x 1
Table 1.