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Table 5
Sub!bases for Combustible Floors Dimensions in(mm)
Sub!base for
Combustible Floors
Part Number
*
H
Subbase for Furnace Only
11
15
/
16
NAHH001SB
(398.5)
5
19
/
16
NAHH002SB
(490.5)
15
22
/
16
NAHH003SB
(582.6)
Subbase for Coil Box
3
15
/
4
NAHH004SB
(25.4)
3
19
/
8
NAHH005SB
(181.1)
NAHH006SB
23 (284.2)
*
Outside Dimension
**
Base Spacer Side To Side
Converstion: 1 in = 25.4 mm
Exploded View of Base for
Figure 29
Downflow Cased Coil
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 1
(28.6mm) narrower than the minimum required size of the
opening in the floor. This is done to maintain a 1" (25.4mm)
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.
26
Sub!base for Combustible
Floor Dimensions
J*
K**
3
9
28
/
(730.3)
14
/
(369.9)
16(406.4)
4
16
3
3
28
/
(730.3)
18
/
(462)
16(406.4)
4
16
3
13
28
/
(730.3)
21
/
(554)
16(406.4)
4
16
9
20
/
16
16
9
14
/
(369.9)
16
(522.3)
(408)
9
20
/
16
16
3
18
/
(462)
16
(522.3)
(408)
9
20
/
16
16
13
21
/
(554)
16
(522.3)
(408)
Plenum
1
2
/
(63.5mm)
2"
1
(38.1mm)
1
/
2"
25-21-65n
1
" 〈31.8mm) shorter and 1
/
4
Specifications are subject to change without notice
Subject to change without notice.
Opening In Floor
L
M
N
1
5
16
/
14
/
4
8
(412.8)
(371.5)
1
1
16
/
18
/
4
4
(412.8)
(463.6)
1
7
16
/
21
/
4
8
(412.8)
(555.6)
1
1
5
/
16
/
14
/
16
4
8
(412.8)
(371.5)
1
1
1
/
16
/
18
/
16
4
4
(412.8)
(463.6)
1
1
7
/
16
/
21
/
16
4
8
(412.8)
(555.6)
3.
Set the base over the opening in the floor, centering the
opening in the base over the opening in the floor. Fasten the
base to the floor with screws or nails. See Figure 28.
4.
Drop the plenum through the opening in the base. The flange
of the plenum should rest on top of the combustible floor base.
Consideration must be given to the height of the base to allow for
easy installation of the condensate drain. See Figure 30. 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 30
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
connection through the side(s) or back of the furnace is NOT
allowed.
Duct Design and Duct Installation Requirements
See Section 10.
1
"
/
8
Internal Filter in Top Return Installation
When installing top!mounted filter inside the furnace, install the
filter clips on the edge of the top duct opening with the wider end of
the clips toward the blower as shown in Figure 31. Clips may be
obtained from your distributor or fabricated from sheet metal
National Excelsior Company
www.excelsiorhvac.com
Opening In
Typical Plenum
Base For Plenum
Dimensions
P
R
S
1
13
/
2
15 (381)
15 (381)
(342.9)
1
17
/
8
15 (381)
15 (381)
(435.6)
3
19
/
4
15 (381)
15 (381)
(501.7)
1
13
/
2
15 (381)
15 (381)
(342.9)
1
17
/
8
15 (381)
15 (381)
(435.6)
3
19
/
4
15 (381)
15 (381)
(501.7)
Condensate Line Raised by Base
25!20!52
T
1
13
/
2
(342.9)
1
17
/
8
(435.6)
3
19
/
4
(501.7)
1
13
/
2
342.9)
(
1
17
/
8
(435.6)
3
19
/
4
(501.7)
441 01 2613 05
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