Sears N8MPL050B12B1 - Manual (Page 26)

Sub-base for Combustible Floors - Downflow Coil
Adapter Box
The subbase for combustible floors is required when a downflow
furnace, used with a downflow coil box, is set on combustible
flooring.
1. Cut the opening in the floor according to the dimensions in
Table 5 because the base is equipped with locating tabs that
center the base over the opening.
The opening in the base is 1V4 "shorter and iVg " narrower
than the minimum required size of the opening in the floor.
This is done to maintain a T'clearance between the floor and
the plenum.
2. Fabricate the plenum to the dimensions given in Table 5.
Note that the dimensions given are outside dimensions.
3. Set the base over the opening in the floor, centering the open­
ing in the base over the opening in the floor. Fasten the base
to the floor with screws or nails. See Figure 29 and
Figure 30.
4. Drop the plenum through the opening in the base. The flange
of the plenum should rest on top of the combustible floor base.
Figuro 29
Exploded View of Base for
Downflow Cased Coil
Figure 30 Setting the Base
Coil Box
Subbase
Insulation
Wood Screw- Plenum
Floor
2S-20-46A
Consideration must be given to the height of the base to allow for
easy installation of the condensate drain. See Figure 31. This
subbase for combustible floors has been designed so that the
height of the subbase raises the downflow coil off the floor to allow
easy installation of the condensate drain
Figure 31 Condensate Line Raised by Base
25-20 52
Non-Combustible Floor
Set the furnace over the opening in the floor. If necessary, grout
around the base to seal air leaks between the base and the floor.
Duct Connections
In the downflow position, the return-air duct must be connected to
only the top of the furnace. Top return connections can be made by
removing the knockout panel in the furnace base. Return air con­
nection through the side(s) or back of the furnace is NOT allowed.
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