Lennox G51MP SERIES Installation Instructions Manual page 13

Installation on Combustible Flooring
(Using an Additive Base)
1 − When unit is installed on a combustible floor, an addi-
tive 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.
CAUTION
The furnace and additive base shall not be installed
directly on carpeting, tile, or other combustible ma-
terial other than wood flooring.
TABLE 2
ADDITIVE BASE FLOOR OPENING SIZE
Cabinet Catalog
Width Number
B Cabinet
11M60
(17.5")
C Cabinet
11M61
(21")
D Cabinet
11M62
(24.5")
2 − After opening is cut, set additive base into opening.
3 − Check fiberglass strips on additive base to make sure
they are properly glued and positioned.
4 − Lower supply air plenum into additive base until ple-
num flanges seal against fiberglass strips.
NOTE − Be careful not to damage fiberglass 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.
G51MP UNIT
PROPERLY
SIZED FLOOR
OPENING
FIGURE 14
Front to Rear Side to Side
in. mm in. mm
22 559 18 − 3/4 476
22 559 22 − 3/4 578
22 559 25 − 3/4 654
SUPPLY AIR PLENUM
ADDITIVE BASE
Installation on Cooling Cabinet
1 − Refer to reverse−flow coil installation instructions for
correctly sized opening in floor and installation of cabi-
net.
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.
Return Air Opening −− Downflow Units
The following steps should be taken when installing ple-
num:
1 − Bottom edge of plenum should be flanged with a
hemmed edge (See figure 15 or 16).
2 − Sealing strips should be used to ensure an airtight seal
between the cabinet and the plenum.
3 − In all cases, plenum should be secured to top of fur-
nace using sheet metal screws.
4 − Make certain that an adequate seal is made.
PLENUM
(Field Provided)
SEALING STRIP
(Field Provided)
PLENUM
(Field Provided)
SECURE FROM
INSIDE CABINET
Page 13
SECURE FROM
OUTSIDE CABINET
É É É É
CABINET
SIDE PANEL
Side View
FIGURE 15
SEALING STRIP
(Field Provided)
É É É É
CABINET
SIDE PANEL
Side View
FIGURE 16