Filter
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15
E. Air Filters Mounted Internal to Furnace:
Fig. 10: Internal filter rack.
: Failure to comply with minimum filter installation requirements may affect the
performance and/or void the warranty on this unit.
If a method other than internal Thermo Pride filter rack is selected for retention of the filters and/or use of
a different filter type is desired, refer to Table 4 below for minimum sizing guidelines for selecting filter for
the unit.
Model Number
Filter Type
Maximum
Air Velocity
(ft/min)
OL6 Qty
*Thermo Products
Supplied Permanent
600 280 in² 2
Standard
Permanent
500 576 in² 2
Disposable 300 960 in² 2
Table 4: Minimum Required Filter Area (in square inches)
* The Thermo Products supplied filter can be cut to size to fit other filter retention systems as
long as the minimum size requirement is met.
NOTICE: Any internal stiffeners used in the filter must not be removed, although
they can be cut to size as needed.