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Install Duct Work
IMPORTANT:
Install duct work in accordance with NFPA 90B and any local
codes.
If there is no complete return air duct system, the return air
connection must be sealed to the furnace casing and run full
size to a location outside the utility room or space housing
the furnace to prevent a negative pressure on the venting
system.
Installation with Return Ducts
A return air duct system is recommended. If the unit is installed in
a confined space or closet, a return connection must be run, full
size, to a location outside the closet. The air duct in the closet
must be tight to prevent any entrance of air from the closet into
the circulating air.
Installation with an Evaporator Coil
When an air conditioning unit is used in conjunction with the
furnace, the evaporator coil must be installed in the discharge
(supply) air. Do not install an evaporator coil in the return air;
excessive condensation will occur within the furnace.
Installation without an Evaporator Coil
If a cooling coil is not installed with the furnace, then a removable
access panel should be provided in the supply plenum for
purposes of inspecting the heat exchanger. This opening must be
accessible when the furnace is installed. It must be large enough
that the heat exchanger can be viewed for possible openings
using light assistance or so that a probe can be inserted for
sampling the airstream. The cover for the opening must be leak
tight.
Filter Specifications
Upflow Models
A filter rack and cleanable 16 in. x 25 in. x 1/2 in. filter are
supplied with model WGFDU only. Filter rack and filters are not
supplied with models WFCU, WFCC, or WGFDC. (Models
designed for more than 1600 CFM nominal air delivery include
two of each.)
Some model furnaces can be installed with either a side or
bottom air return. For bottom air return the bottom air return
knockout plate must be removed. For units that do not include a
side or bottom return filter rack, kit no. AFILT524-1 (side return) or
kit no. AFILT529-1 (bottom return) can be used.
To provide sufficient filter area for installations requiring more
than 1600 CFM nominal air delivery, return air will have to be
brought through both sides of the furnace, or through one side
and the bottom, or an optional filter rack WAFILTHA7 may be
used.
Counterflow Models
Filters are not supplied with these furnaces; however, filters must
be used. It is the installer's responsibility to install a filter rack with
the ductwork and to install properly sized filters in accordance
with the "Minimum Filter Requirements Chart."
The Airflow Descriptor is the 2 digits immediately preceding
the hyphen (-) in the furnace model number. Example: 16 is
the Airflow Descriptor for furnace model WFAT075B16-1A.
The model number is located on the rating plate inside the
access panel.
Areas and dimensions shown for cleanable filters are based
on filters rated at 600 ft per minute face velocity.
Typical filter sizes are shown; however, any combination of
filers whose area equals or exceeds the minimum area shown
is satisfactory.
Minimum Filter Requirements Chart
Disposable Filters
Airflow
Min. Area
Size
Descriptor
(sq. in.)
(in.)
09
480
20 x 25
10
480
20 x 25
12
576
16 x 20
14
672
20 x 20
16
768
20 x 20
20
960
20 x 25
If a central return air filter-grille is used, the furnace does not
require a filter.
To install a filter at the furnace only, use the following kits:
AFILT524 for side return on upflow installations.
AFILT529 for bottom return on upflow furnace installations.
WAFILTHA7 for single side return in installations requiring
more than 1600 CFM nominal air delivery.
Cleanable Filters
Qty. Min. Area
Size
Qty.
(sq. in.)
(in.)
1
240
16 x 20
1
1
240
16 x 20
1
2
288
16 x 20
1
2
336
20 x 20
1
2
384
20 x 20
1
2
480
20 x 25
1
15
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