Service Manual

PRODUCT DESIGN
40
cally require less frequent replacement intervals. Avoid us-
ing highly restrictive 1" filters which produce static pres-
sure loss greater than .25" W.C. In some installations the
minimum filter size required (consult filter sizing chart ) will
not lend itself to a filter installation on the side of the fur-
nace. The installation of a centrally installed air cleaner
cabinet or a return duct filter installation may offer more
practicality.
Clean Comfort™ brand MERV 11 air cleaners have 5¼”
media filters and are available in the following configura-
tions. Consult your distributor for information on our com-
plete line of IAQ Clean Comfort™ products.
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 mini-
mum filter requirement charts for determination of the mini-
mum filter area to ensure proper unit performance. The fol-
lowing figures show possible filter locations.
NOTE: A ductwork access door must be used in counter-
flow 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 di-
mension 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 cabi-
net size:
"A"
Min
Return Air
Optional
Access
Door
Horizontal Installations
Filter(s) must be installed external to the furnace casing for
horizontal installations. For most installations it is prefer-
able to use a central return with filters installed in the duct
behind the return air grille. 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 perma-
nent 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.