INSTALLATION INSTRUCTIONS
Gas Furnace: (F/G)MAC
440 01 4201 01
23
Specifications subject to change without notice.
Filter Arrangement
!
WARNING
FIRE, CARBON MONOXIDE AND POISONING
HAZARD
Failure to follow this warning could result in personal
injury, or death.
Never operate a furnace without a filter or filtration device
installed. Never operate a furnace with filter or filtration
device access doors removed.
Furnaces shipped without a filter rack:
There are no provisions for an internal filter in these furnaces.
An external filter rack is required and is purchased separately.
A field supplied accessory air cleaner may also be used in
place of the filter rack.
For upflow applications, the filter can be installed on either side
of the furnace, the bottom of the furnace or any combination of
side and bottom of the furnace. (See
Figure 27
,
Figure 29
, and
Figure 30
)
For downflow applications, the filter rack (or field supplied
accessory air cleaner) must only be connected to the bottom
opening on the furnace (See
Figure 26
and
Figure 30
and
Table 7
).
For horizontal applications, the filter rack (or field supplied
accessory air cleaner) can be connected to the bottom opening
on the furnace. For side return use in the horizontal position,
refer to
Figure 28
. If both side and bottom openings are used in
Figure 28
, each opening used will require a filter.
A filter rack or any field supplied accessory air cleaner can also
be installed in the common return duct prior to entering the
return air opening in any orientation.
See
Table 6
for recommended filter size details.
Table 6
Filter Size Information
−
inch (mm)
FURNACE
CASING
WIDTH
FILTER SIZE
FILTER
TYPE
SIDE RETURN
BOTTOM
RETURN
17-1/2
(445)
16 x 25 x 3/4
(406 x 635 x 19)
16 x 25 x 3/4
(406 x 635 x 19)
Washable*
21 (533)
16 x 25 x 3/4
(406 x 635 x 19)
20 x 25 x 3/4
(508 x 635 x 19)
Washable*
24-1/2
(622)
16 x 25 x 3/4
(406 x 635 x 19)
24 x 25 x 3/4
(610 x 635 x 19)
Washable*
* Recommended to maintain air filter face velocity. See Product Data for part
number.
Refer to the instructions supplied with the Filter Rack or
accessory air filter
for additional assembly and installation
options
.
Figure 26
Downflow Return Air
Configurations and Restrictions
L10F033
Figure 27
Upflow Return Air Configurations
and Restrictions
L10F032
Figure 28
Horizontal Return Air
Configurations and Restrictions
HORIZONTAL TOP
RETURN NOT
PERMITTED FOR
ANY MODEL
SIDE RETURN AIR NOT
PERMITTED FOR 2000 CFM
AND ABOVE OF AIR FLOW
L10F034
