Goodman GMES80 Series Service And Troubleshooting page 24

SYSTEM OPERATION
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.
COUNTERFLOW FILTER INSTALLATION
This furnace has provisions for the installation of return air
filters at the counterflow top return. 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.
Horizontal Installations
Filter(s) must be installed external to the furnace casing for
horizontal installations. For most installations it is preferable
to use a central return with filters installed in the duct behind
the return air grill. In this way filter replacement is relatively
simple by merely removing the grille, rather than going into
the attic or crawl space.
ADDITIONAL FILTERING ACCESSORIES
External Filter Rack Kit (EFR01)
The external filter rack kit is intended to provide a location
external to the furnace casing, for installation of a permanent
filter on upflow model furnaces. The rack is designed to mount
over the indoor blower compartment area of either side panel,
and provide filter retention as well as a location for attaching
return air ductwork.
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