Step 4—Return Air Connections
Never connect return-air ducts to the back of the furnace. A
failure to follow this warning can cause a fire, personal injury,
or death.
The return-air duct must be connected to bottom, sides (left or
right), or a combination of bottom and side(s) of main furnace
casing as shown in Fig. 1. Bypass humidifier may be attached into
unused side return air portion of the furnace casing. DO NOT
connect any portion of return-air duct to back of furnace casing.
Step 5—Filter Arrangement
The factory-supplied filter(s) is shipped in the blower compart-
ment. Determine location for the filter and relocate filter retaining
wire if necessary. See Fig. 5 for side return application and Fig. 6
for bottom return application. See Table 3 to determine correct
filter size for desired filter location. Table 3 indicates filter size,
location, and quantity shipped with the furnace.
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 for
bottom return. All hardware is provided for filter installation.
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 maximum 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.)
3. Install another nut on other side of furnace base. (Install flat
washer if desired.)
4. Adjust outside nut to provide desired height, and tighten inside
nut to secure arrangement.
Fig. 5—Side Filter Arrangement
(Control Removed for Clarity)
A99278
FILTER
RETAINER
WASHABLE
FILTER
Fig. 6—Bottom Filter Arrangement
(Control Removed for Clarity)
A99279
WASHABLE
FILTER
FILTER
SUPPORT
FILTER
RETAINER
Table 3—Filter Information (In.)
FURNACE
CASING WIDTH
FILTER SIZE*
FILTER TYPE
Side Return
Bottom Return
14-3/16
(1) 16 X 25 X 1†
(1) 14 X 25 X 1
Cleanable
17-1/2
(1) 16 X 25 X 1†
(1) 16 X 25 X 1
Cleanable
21
(1) 16 X 25 X 1
(1) 20 X 25 X 1†
Cleanable
24-1/2
(2) 16 X 25 X 1
(1) 24 X 25 X 1†
Cleanable
* Filters can be field modified by cutting 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
