All installations and services must be performed by qualified service personnel.
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Fig. 17: Location of the air filter and blower compartment access door on the typical lowboy furnace.
OH Series (Highboy)
The filter rack will be located between the return air plenum and the return air opening on the side of the
furnace, refer to figure 18. Slide the dirty filter out, clean it with a mild soap and water solution. Make sure filter is
thoroughly dry before replacing.
Fig. 18: Location of the air filter on the typical highboy furnace.
OC Series (Counterflow)
For removal of the filter, remove front door of furnace. Then, remove blower access panel for access to
filter, refer to figure 19. Clean filter by vacuuming, tap-water rinsing or washing in an ordinary detergent soloution.
After cleaning, replace the completely dry filter mesh side down.
Fig. 19: location of the air filters on a typical counterflow furnace.