All installations and services must be performed by qualified service personnel.
Figure 20
3. USE OF NON-THERMO PRIDE FILTER RETENTION MEANS
If a method other than the Thermo Pride filter rack is selected for retention of the filter and/or use of a
different filter type is desired, see Table 3 for minimum size guidelines for selecting a filter system for the
CHX3 or CDX3 furnaces.
MINIMUM FILTER AREA REQUIRED (LENGTH X WIDTH, SQ. IN.)
TABLE 3
FILTER TYPE
MAXIMUM
RATE
AIR VELOCITY
Required CFM / (Filter Velocity Rating x 144) = min. filter
(in
2
)
FURNACE MODEL
CHX3,CDX3-75
CHX3,CDX3-100 CHX3,CDX3-125
*THERMO
PRODUCTS
SUPPLIED
PERMANENT FILTER
600 FT./MIN.
254 IN.
2*
328 IN.
2*
402 IN.
2*
STANDARD
PERMANENT FILTER
500 FT./MIN.
304 IN.
2
394 IN.
2
484 IN.
2
DISPOSABLE TYPE
FILTER
300 FT./MIN.
506 IN.
2
656 IN.
2
804 IN.
2
* 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.
NOTICE:
The filter areas in table 3 are the
minimum
areas required based on the CFM generated by
the furnace for standard heating speeds only. The following formula can be used to determine the
minimum filter area required for cooling if the unit is equipped with cooling. This value should then be
compared to the value shown in table 3 and the larger of the two should then be used for determining the
minimum filter area required for that installation.
31
