c. When ducts are used, they must be of the same cross-
sectional area as the free area of the openings to which
they connect. The minimum dimension of rectangular
ducts must not be less than 3 in. (See Fig. 3.)
WARNING:
Do not install the furnace on its back;
safety control operation will be adversely affected. 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.
III.
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. 4 for side return application and Fig. 5
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 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 strip 1 X 3 X 24-1/2
in. and install it along side of the filter as shown in Fig. 5. 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.
WARNING:
Never operate unit without a filter or with
filter access door removed. Failure to follow this warning
can cause fire, personal injury, or death.
IV.
LEVELING LEGS (IF REQUIRED)
When the furnace is used with side inlet(s) and leveling legs are
required, refer to Fig. 6, 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. 6.
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.)
For Example:
480BAV FURNACE
INPUT BTUH
FREE AREA PER OPENING
(SQ IN.)
ROUND PIPE
(IN. DIA)
44,000
11.0
4
66,000
16.5
5
88,000
22.0
6
110,000
27.5
6
132,000
33.0
7
154,000
38.5
7
For Example:
480BAV FURNACE
INPUT BTUH
FREE AREA PER OPENING
(SQ IN.)
ROUND PIPE
(IN. DIA)
44,000
22.0
6
66,000
33.0
7
88,000
44.0
8
110,000
55.0
9
132,000
66.0
10
154,000
77.0
10
Fig. 3—Air For Combustion and Ventilation
(Outside Air)
A89013
1 SQ IN.
PER
4000
BTUH*
DUCTS
TO
OUTDOORS
1 SQ IN.
PER 4000
BTUH*
SUPPLY
AIR
VENT
THROUGH
ROOF
D
B
A
C
E
1 SQ IN.
PER 4000
BTUH*
DUCT
TO
OUTDOORS
RETURN AIR
1 SQ IN.
PER 2000
BTUH*
1 SQ IN.
PER 2000
BTUH*
DUCTS
TO
OUTDOORS
12
″
MAX
12
″
MAX
12
″
MAX
Use any of the following
combinations of openings:
A & B C & D D & E F & G
NOTE:
*Minimum dimensions of 3-In.
CONFINED
SPACE
12
″
MAX
12
″
MAX
OUTDOORS
1 SQ IN.
PER
4000
BTUH*
F
G
Fig. 4—Side Filter Arrangement
(Control Removed for Clarity)
A93045
FILTER
RETAINER
WASHABLE
FILTER
—5—
