507712-01
Page 10 of 36
Issue 1642
Return Air
Return air must be brought in through the top of the furnace
installed in an downflow application.
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
air in the living space. Use sheet metal screws and joint
tape to seal return air system to furnace.
In platform installations with furnace return, 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.
For no reason should return and supply air duct systems
ever 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
Figure 10. Installation Clearances
*Front
0
Back
0
Sides
0†
Vent
0
Floor
NC‡
* Front clearance in alcove installation must be 24 in. (610
mm). Maintain a minimum of 24 in. (610 mm) for front service
access.
† Allow proper clearances to accommodate condensate trap
and vent pipe installation.
‡ The furnace may be installed on a combustible wood floor if
an optional additive base is installed between the furnace and
the combustible floor.
Installation on Non-Combustible Flooring
See Figure 11
1.
Cut floor opening keeping in mind clearances listed
on unit rating plate. Also keep in mind gas supply
connections, electrical supply, flue and air intake
connections and sufficient installation and servicing
clearances. See Table 1 for correct floor opening size.
2. Flange warm air plenum and lower the plenum into the
opening.
3. Set the unit over the plenum and seal the plenum to
the unit.
4. Ensure that the seal is adequate.
Table 1. Non-Combustible Floor Opening Size
Cabinet Width
Front to Rear
Side to Side
in.
mm
in.
mm
B Cabinet (17.5”)
19-3/4
502
16-5/8
422
C Cabinet (21”)
19-3/4
502
20-1/8
511
NOTE
: Floor opening dimensions listed are 1/4 inch (6 mm)
larger than the unit opening. See dimension drawing on page
2.
Figure 11
Installation on Combustible Flooring
See Figure 12
1.
When unit is installed on a combustible floor, a
downflow combustible flooring base must be installed
between the furnace and the floor. The base must be
ordered separately. See Table 2 for opening size to
cut in floor.
The furnace and combustible flooring base shall not be
installed directly on carpeting, tile, or other combustible
material other than wood flooring.
CAUTION
