Lennox SL280V Installation Instructions Manual page 9

Downflow Installation
Downflow unit installs in three ways: on non−combustible
flooring, on combustible flooring using a downflow com-
bustible flooring base, or on a reverse−flow cooling cabinet.
Do not drag the unit across the floor.
Installation on Non−Combustible Flooring (Figure 6)
1 − Cut floor opening keeping in mind clearances listed on
unit rating plate. Also keep in mind gas supply connec-
tions, 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.
SL280DFV UNIT
OPENING
FIGURE 6
TABLE 1
NON−COMBUSTIBLE FLOOR OPENING SIZE
Front to Rear
Cabinet Width
in.
A (14.5") 19−3/4
B (17.5") 19−3/4
C (21") 19−3/4
NOTE − Door opening dimensions listed are 1/4 inch (6 mm) larger than
the unit opening. See unit dimensions on page 2.
Installation on Combustible Flooring (Figure 7)
1 − When unit is installed on a combustible floor, a down-
flow combustible flooring base must be installed be-
tween the furnace and the floor. The base must be or-
dered separately.
See table 2 for opening size to cut in floor.
SUPPLY AIR
PLENUM
Side to Side
mm in. mm
502 13−1/4 337
502 16−1/4 413
502 19−3/4 502
The furnace and downflow combustible flooring
base shall not be installed directly on carpeting, tile,
or other combustible material other than wood floor-
ing.
SL280DFV UNIT
PROPERLY
SIZED FLOOR
OPENING
COMBUSTIBLE FLOOR OPENING SIZE
Cabinet Width
A (14.5")
B (17.5")
C (21")
NOTE − Floor opening dimensions listed are 1/4 inch (6 mm) larger than
unit opening. See unit dimensions on page 2.
2 − After opening is cut, set combustible flooring base into
opening.
3 − Check sealing strips on combustible flooring base to
make sure they are properly glued and positioned.
4 − Lower supply air plenum into downflow combustible
flooring base until plenum flanges seal against the
strips.
NOTE − Be careful not to damage sealing strips. Check
for a tight seal.
5 − Set the furnace over the plenum.
6 − Ensure that the seal between the furnace and plenum
is adequate.
Installation on Cooling Cabinet (Figure 8)
1 − Refer to reverse−flow coil installation instructions for
correctly sized opening in floor and installation of cabi-
net.
NOTE − Downflow combustible flooring kit is not used
2 − When cooling cabinet is in place, set and secure the
furnace according to the instructions that are provided
with the cooling coil. Secure the furnace to the cabinet.
3 − Seal the cabinet and check for air leaks.
Page 9
CAUTION
SUPPLY AIR PLENUM
DOWNFLOW
COMBUSTIBLE
FLOORING BASE
FIGURE 7
TABLE 2
Front to Rear Side to Side
in. mm in.
22 559 15−3/4
22 559 18−3/4
22 559 22−3/4
mm
400
476
578