For bottom air-return applications, filter may need to be cut to fit
some furnace casing widths. A bottom closure panel is factory
installed in the bottom of the furnace. When bottom return inlet is
desired, remove and discard the bottom closure panel. Two sets of
hardware are needed for furnaces in 24-1/2-in. wide casings using
2 filters for bottom return. All hardware is provided for filter
installation.
NOTE: Furnaces with a 17-1/2-in. wide casing require an addi-
tional procedure when locating the filter for bottom return-air
application. Field fabricate a sheet metal filler strip1X3X24-1/2
in. and install it along side of the filter as shown in Fig. 6. Drive
2 screws through the casing side and into the filler strip to secure
it in place. Filter should rest on the top of the filler strip when
installed.
Never operate unit without a filter or with filter access door
removed. Failure to follow this warning can cause fire,
personal injury, or death.
Step 6—Leveling Legs (If Required)
When the furnace is used with side inlet(s) and leveling legs are
required, refer to Fig. 7, and install field-supplied, corrosion-
resistant 5/16-in. machine bolts and nuts.
NOTE: The length of the bolt should not exceed 1-1/2 in.
1. Lay furnace on its back. Locate and drill 5/16-in. diameter
hole in each bottom corner of furnace as shown in Fig. 7.
2. Install nut on bolt and install bolt and nut in hole. (Install flat
washer if desired.)
Fig. 5—Side Filter Arrangement
(Control Removed for Clarity)
A93045
FILTER
RETAINER
WASHABLE
FILTER
→Fig. 6—Bottom Filter Arrangement
(Control Removed for Clarity)
A00290
WASHABLE
FILTER
FILTER
SUPPORT
FILTER
RETAINER
17
1
⁄2-IN. WIDE
CASINGS ONLY:
INSTALL FIELD-SUPPLIED
FILTER FILLER STRIP
UNDER FILTER.
1″
24
1
/
2
″
3″
21-IN. WIDE
CASINGS ONLY:
SUPPORT RODS (3)
EXTEND 1/4" ON EACH
SIDE OF FILTER AND
REST ON CASING FLANGE
→Table 3—Filter Information (In.)
FURNACE
CASING WIDTH
FILTER SIZE*
FILTER
TYPE
Side Return Bottom Return
14-3/16 (1)16X25X1† (1) 14 X 25 X 1 Cleanable
17-1/2 (1)16X25X1† (1)16X25X1† Cleanable
21 (1)16X25X1 (1)20X25X1† Cleanable
24-1/2 (1 or 2) 16 X 25 X 1† (1)24X25X1† Cleanable
* Filters can be field modified by cutting the frame as marked and folding to the
desired size. Alternate sizes can be ordered from your distributor or dealer.
† Factory provided with the furnace.
Fig. 7—Leveling Leg Installation
A89014
1
3
⁄4″
1
3
⁄4″
1
3
⁄4″
1
3
⁄4″
5
⁄16″
5
⁄16″
5
⁄16″
5
⁄16″
7
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