Filter
Top Products
All installations and services must be performed by qualified service personnel.
30
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 CHB1 or CDB1
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)=
FILTER (IN
2
)
FURNACE MODEL
CHB1,CDB1-50
CHB1,CDB1-75
CHB1,CDB1-100
CHB1,CDB1-125
*THERMO PRODUCTS
SUPPLIED
PERMANENT FILTER
600 FT./MIN.
172 IN.
2 *
254 IN.
2*
328 IN.
2*
402 IN.
2*
STANDARD
PERMANENT FILTER
500 FT./MIN.
208 IN.
2
304 IN.
2
394 IN.
2
484 IN.
2
DISPOSABLE TYPE
FILTER
300 FT./MIN.
344 IN.
2
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.