Goodman AMH8 Service Instructions Manual page 35

PRODUCT DESIGN
A return air filter is not supplied with the furnace. The in-
staller must supply a means of filtering all of the return air.
Filter(s) shall comply with UL900 or CAN/ULC-S111 Stan-
dards. If the furnace is installed without filters, the warranty
will be voided.
MINIMUM FILTER SIZES for DISPOSABLE FILTERS
FURNACE INPUT
40M / 45M
60M / 70M
80M / 90M
100M / 115M
120M
140M
DISPOSABLE NOMINAL 300 F.M. FACE VELOCIT Y
SIDE RETURN
Cabinet Nominal Approx.
Width Filter Flow Area
(In.) Size (In.) (In.)
All 16x25x1 400
Refer to Minimum Filter Area tables to determine filter area
requirement. NOTE: Filters can also be installed elsewhere
in the duct system such as a central return.
One inch throwaway filters should be sized for a face ve-
locity of 300 feet per minute or less (14x25x1 throwaway =
730 CFM maximum, 16x25x1 throwaway = 830 CFM maxi-
mum, 18x25x1 throwaway = 940 CFM maximum, 20x25x1
throwaway = 1040 CFM maximum) All other filters should
be sized according to their manufacturer's instructions.
To find the miminum filter requirement (in
manent or disposable filters divide the required airflow (CFM)
by the rated velocity of the filter, either 300ft/min for dis-
posable filter or 600ft/min for permanent filter. Multiply the
2
number by 144 in. to obtain the minimum filter requirement
(in 2 ).
EXAMPLE:
2
Filter Size (in ) =
2
Filter Size (in ) =
Filter Size
Filter Size
FILTER SIZE
2
320 in
2
483 in
2
640 in
2
800 in
2
738 in
2
738 in
BOTTOM RETURN
Cabinet Nominal Approx.
Width Filter Flow Area
(In.) Size (In.) (In.)
14" 14X25X1 350
17-1/2 14X25X1 350
21 16x25x1 400
24-1/2 20X25X1 500
2 ) for either per-
2
1400 CFM x 144 in
600 ft./min. (Permanent)
2
1400 CFM x 144 in
300 (Disposable) ft./min.
2
= 672in Disposable
2
= 336in Permanent
Upflow furnaces with air delivery of less than 1800 CFM:
Use one side return or one bottom return ductwork con-
nection.
Upflow furnaces with air delivery of 1800 CFM or higher:
Use two side returns or one side return and one bottom
return connection.
Guide dimples locate the side and bottom return cutout lo-
cations. Use a straight edge to scribe lines connecting the
dimples. Cut out the opening on these lines. An undersized
opening will cause reduced airflow. For bottom return con-
nection, remove the bottom of the cabinet before setting
the furnace on the raised platform or return air duct.
A closed return duct system must be used, with the return
duct connected to the furnace. NOTE: Ductwork must never
be attached to the back of the furnace. Supply and return
connections to the furnace may be made with flexible joints
to reduce noise transmission, if desired. If a central return
s used, a connecting duct must be installed between the
unit and the utility room wall so the blower will not interfere
with combustion air or draft. The room, closet, or alcove
must not be used as a return air chamber.
When the furnace is used in connection with a cooling
unit, the furnace should be installed in parallel with or on
the upstream side of the cooling unit to avoid condensation
in the heating element. With a parallel flow arrangement,
the dampers or other means used to control the flow of air
must be adequate to prevent chilled air from entering the
furnace and, if manually operated, must be equipped with
means to prevent operation of either unit unless the damper
is in the full heat or cool position.
When the furnace is heating, the temperature of the return
air entering the furnace must be between 55°F and 100°F.
UPRIGHT FILTER INSTALLATIONS
Depending on the installation and/or customer preference,
differing filter arrangements can be applied. Filters can be
installed in the central return register and a side panel ex-
ternal filter rack kit (upflow filter kit # EFR01). As an alter-
native a media air filter or electronic air cleaner can be
used as the requested filter. Refer to the following minimum
filter requirement charts for determination of the minimum
filter area to ensure proper unit performance. The following
figures show possible filter locations. NOTE: A ductwork
access door must be used in counterflow applications to
allow filter removal. If the filter rack is used, the side of the
plenum must be at least as tall as dimension "A" shown in
the following illustration. For dimension of "A" refer to the
following chart.
COUNTERFLOW FILTER INSTALLATION
This furnace has provisions for the installation of return air
filters at the counterflow top return. The furnace will
accommodate the following filter sizes depending on cabinet
size:
35