440 01 1024 01
Specifications are subject to change without notice
41
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
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
1
/
4
″
shorter and 1
1
/
8
″
narrower than
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.
Table 13
Subbases for Combustible Floors Dimensions
Sub--base for
Combustible Floors
Part Number
Sub--base for Combustible
Floor Dimensions
Opening In
Floor
Opening In
Base For Ple-
num
Typical Plenum
Dimensions
H
*
J*
K**
L
M
N
P
R
S
T
Furnace Only
NAHH001SB
15
11
/
16
28
3
/
4
14
9
/
16
16
16
1
/
4
14
5
/
8
15
13
1
/
2
15
13
1
/
2
NAHH002SB
19
5
/
16
28
3
/
4
18
3
/
16
16
16
1
/
4
18
1
/
4
15
17
1
/
8
15
17
1
/
8
NAHH003SB
22
15
/
16
28
3
/
4
21
13
/
16
16
16
1
/
4
21
7
/
8
15
19
3
/
4
15
19
3
/
4
NAHH010SB
24
11
/
16
28
3
/
4
23
9
/
16
16
16
1
/
4
23
5
/
8
15
22
1
/
2
15
22
1
/
2
Subbase for Coil Box
NAHH004SB
15
3
/
4
20
9
/
16
14
9
/
16
16
1
/
16
16
1
/
4
14
5
/
8
15
13
1
/
2
15
13
1
/
2
NAHH005SB
19
3
/
8
20
9
/
16
18
3
/
16
16
1
/
16
16
1
/
4
18
1
/
4
15
17
1
/
8
15
17
1
/
8
NAHH006SB
23
20
9
/
16
21
13
/
16
16
1
/
16
16
1
/
4
21
7
/
8
15
19
3
/
4
15
19
3
/
4
NAHH009SB
24
3
/
4
20
9
/
16
23
9
/
16
16
1
/
16
16
1
/
4
23
5
/
8
15
22
1
/
2
15
22
1
/
2
*
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.
5. Position furnace or coil cabinet and furnace on subbase so it
aligns between the locating tabs.
Figure 47
Plenum
S
T
A
Hole in
Floor
M
N
25--20--46
Combustible
Floor Base
L
R
H
K
2
″
2
″
1
″
J
P
A = 4 1/4” Minimum clearance from back of hole to wall or other obstruction.
Exploded View of Sub--Base for
Furnace ONLY
Figure 48
Exploded View of Base for
Downflow Cased Coil
2
1
/
2
″
1
1
/
2
″