Step 5—Filter Arrangement
Do not install furnace on its back. Safety control operation
will be adversely affected. Never connect return-air ducts to
back of furnace. Failure to follow this warning could result in
fire, personal injury, or death.
The air filter arrangement will vary due to application and filter
type. The filter may be installed in an external Filter/Media cabinet
(if provided) or the furnace blower compartment. Factory supplied
washable filters are shipped in the blower compartment.
If a factory-supplied external Filter/Media cabinet is provided,
instructions for its application, assembly, and installation are
packaged with the cabinet. The Filter/Media cabinet can be used
with the factory-supplied washable filter or a factory-specified
high-efficiency disposable filter (see cabinet instructions).
If installing the filter in the furnace blower compartment, deter-
mine 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.
Fig. 3—Confined Space: Air for Combustion and
Ventilation from an Unconfined Indoor Space
A89012
SUPPLY
AIR
6
″
MIN
(FRONT)
†
RETURN AIR
VENT THROUGH ROOF
1 SQ IN.
PER 1000
BTUH* IN DOOR
OR WALL
12
″
MAX
1 SQ IN.
PER 1000
BTUH* IN DOOR
OR WALL
12
″
MAX
INTERIOR
HEATED
SPACE
* Minimum opening size is 100 sq in. with
minimum dimensions of 3 in.
†
Minimum of 3 in. when type-B1 vent is used.
UNCONFINED
SPACE
CONFINED
SPACE
Fig. 4—Confined Space: Air for Combustion and
Ventilation from Outdoors
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
Table 2—Minimum Free Area Of Combustion Air Opening*
58YAV
FURNACE
INPUT
(BTUH)
AIR FROM INDOOR
UNCONFINED SPACE
OUTDOOR AIR THROUGH
VERTICAL DUCTS
OUTDOOR AIR THROUGH
HORIZONTAL DUCTS
OUTDOOR AIR THROUGH
SINGLE DUCT
Free Area
of Opening
(Sq In.)
Free Area of
Opening and Duct (Sq
In.)
Round
Pipe
(In. Dia)
Free Area of
Opening and Duct
(Sq In.)
Round
Pipe
(In. Dia)
Free Area of
Opening and Duct (Sq
In.)
Round
Pipe
(In. Dia)
66,000
100
16.5
5
33.0
7
22.00
6
88,000
100
22.0
6
44.0
8
29.33
7
110,000
110
27.5
6
55.0
9
36.67
7
132,000
132
33.0
7
66.0
10
44.00
8
154,000
154
38.5
8
77.0
10
51.33
9
* Free area shall be equal to or greater than the sum of the areas of all vent connectors in the confined space. Opening area must be increased if other gas appliances
in the space require combustion air.
6
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