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Subbase for Combustible Floor
NOTE: The three(3) screws in the top panel of the furnace next to
the duct flange MUST be removed to provide serviceability of the
primary heat exchangers in the downflow installation
Note: When using the subbase for combustible floors, the
discharge air duct flanges on the furnace MUST be broken down to
provide proper fit up to the subbase. Use duct pliers to bend the
duct flanges flat onto the furnace casing. DO NOT bend the duct
flanges inward (toward the heat exchangers) as air flow
restrictions may occur.
The Subbase for Combustible Floors MUST be used when a
Table 13
Subbases for Combustible Floors Dimensions
Sub- -base for
Combustible Floors
Part Number
Furnace Only
NAHH001SB
NAHH002SB
NAHH003SB
NAHH010SB
Subbase for Coil Box
NAHH004SB
NAHH005SB
NAHH006SB
NAHH009SB
*
Outside Dimension
**
Base Spacer Side To Side
3.
Set the base over the opening in the floor, centering it over
the opening. Fasten the base to the floor with screws or
nails. See Figure 47, Figure 48 and Figure 49.
4.
Drop the plenum through the opening in the base. The
flange of the plenum should rest on top of the subbase.
Exploded View of Sub- -Base for
Figure 47
Furnace ONLY
T
Plenum
H
K
R
P
2"
L
M
N
Hole in
Floor
A
A = 4 1/4" Minimum clearance from back of hole to wall or other obstruction.
440 01 1024 01
Sub- -base for Combustible
Floor Dimensions
*
H
J*
K**
11
3
9
15
/
28
/
14
/
16
4
16
5
3
3
19
/
28
/
18
/
16
4
16
15
3
13
22
/
28
/
21
/
16
4
16
11
3
9
24
/
28
/
23
/
16
4
16
3
9
9
15
/
20
/
14
/
4
16
16
3
9
3
19
/
20
/
18
/
8
16
16
9
13
23
20
/
21
/
16
16
3
9
9
24
/
20
/
23
/
4
16
16
S
Combustible
Floor Base
J
2"
1"
25--20--46
Specifications are subject to change without notice
downflow furnace is set on a combustible floor, even when the
furnace is installed on a coil box.
1.
Cut the opening in the floor according to Table 13. The hole
in the floor must be cut to the dimensions listed in Table 13
since the base is equipped with locating tabs that center the
base over the opening.
The opening in the base is 1
the recommended size of the opening in the floor. This is done to
maintain clearance between the floor and the plenum.
2.
Fabricate the plenum to the dimensions given in Table 13.
Note that the dimensions given are outside dimensions.
Opening In
Floor
L
M
N
1
5
16
16
/
14
/
4
8
1
1
16
16
/
18
/
4
4
1
7
16
16
/
21
/
4
8
1
5
16
16
/
23
/
4
8
1
1
5
16
/
16
/
14
/
16
4
8
1
1
1
16
/
16
/
18
/
16
4
4
1
1
7
16
/
16
/
21
/
16
4
8
1
1
5
16
/
16
/
23
/
16
4
8
5.
Position furnace or coil cabinet and furnace on subbase so it
aligns between the locating tabs.
Figure 48
1
1
/
" shorter and 1
/
" narrower than
4
8
Opening In
Typical Plenum
Base For Ple-
Dimensions
num
P
R
S
1
15
13
/
15
2
1
15
17
/
15
8
3
15
19
/
15
4
1
15
22
/
15
2
1
15
13
/
15
2
1
15
17
/
15
8
3
15
19
/
15
4
1
15
22
/
15
2
Exploded View of Base for
Downflow Cased Coil
1
2
/
2
1
1
/
2
T
1
13
/
2
1
17
/
8
3
19
/
4
1
22
/
2
1
13
/
2
1
17
/
8
3
19
/
4
1
22
/
2
"
"
41
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