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CAUTION
If filters are only suitable for heating application, advise
homeowner that filter size may need to be increased if air
conditioning is added.
Addition Of Air Conditioning
When a refrigeration coil is used in conjunction with this unit, it must
be installed on the discharge side of the unit to avoid condensation
on the heat exchanger. The coil installation instructions must be
consulted for proper coil location and installation procedures. With
a parallel flow arrangement, dampers must be installed to prevent
chilled air from entering the furnace. If manually operated dampers
are used, they must be equipped with a means to prevent operation
of either unit unless the damper is in full heat or full cool position.
A 3² clearance is required on the right side of the furnace in order to
run the condensate drain line. Copper, iron or plastic tubing may be
used for the condensate drain line.
Downflow Furnace Installation
Non- Combustible Floor Installation
Fabricate a plenum to the dimensions given in Table 8, for the fur-
nace outlet. Plenum should be flanged, approximately
port.
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 pri-
mary heat exchangers in the downflow installation
1.
Position plenum through the floor and 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.
Table 8
Subbases for Combustible Floors Dimensions
Subbase for Combustible
Floors Part Number
Floors Part Number
Furnace Subbase
NAHH001SB
NAHH002SB
NAHH003SB
NAHH010SB
Subbase for Coil Cabinets
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 37, Figure 38 and Figure 39.
32
3
/
² for sup-
4
Subbase 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
5
3
13
22
/
28
/
21
/
16
4
16
3
3
9
24
/
28
/
23
/
4
4
16
11
9
9
15
/
20
/
14
/
16
16
16
5
9
3
19
/
20
/
18
/
16
16
16
9
13
23
20
/
21
/
16
16
11
9
9
24
/
20
/
23
/
16
16
16
Combustible Floor Installation
!
FIRE HAZARD
Failure to install unit on noncombustible subbase can
result in death, personal injury and/or property damage.
Place furnace on noncombustible subbase on downflow
applications, unless installing on non- -combustible
flooring.
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 dis-
charge 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 down-
flow 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 8. The hole in
the floor must be cut to the dimensions listed in Table 8
since the base is equipped with locating tabs that center the
base over the opening.
The opening in the base is 1
recommended size of the opening in the floor. This is done to main-
tain clearance between the floor and the plenum.
2.
Fabricate the plenum to the dimensions given in Table 8.
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
1
5
16
/
16
/
23
/
4
4
8
1
1
5
16
/
16
/
14
/
4
4
8
1
1
1
16
/
16
/
18
/
4
4
4
1
1
7
16
/
16
/
21
/
4
4
8
1
5
16
16
/
23
/
4
8
4.
Drop the plenum through the opening in the base. The
flange of the plenum should rest on top of the subbase.
1
1
/
² shorter and 1
/
² narrower than the
4
8
Opening In Base
Typical Plenum
For Plenum
Dimensions
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
440 01 1020 02
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
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