HP 422690 I FILTER CABINETS, GAS, HIGH, MOTOR, HORSE, POWER, VELOCITY, (Btu/hr), WASHABLE, (inches), DISPOSABLE, AIR FILTER, AIR FILTER, - two required

Follow these instructions and the filter manufacturer's

instructions for minimum size and quantity recommendations. Air velocity must not exceed 300 feet per minute through low velocity disposable filters. Air velocity must not exceed 650 feet per minute through high velocity washable filters. Undersized filters reduce airflow and can adversely affect furnace and cooling system operation.

See Table 6 for recommended filter size for bottom return installations. Side return filters must be at least 16" X 25" X 1", high-velocity washable filters.

Table 6. Recommended Filter Size--Bottom Return.

GAS	MOTOR*	DISPOSABLE	HIGH-
INPUT*	HORSE-	AIR FILTER	VELOCITY
(Btu/hr)	POWER	- two required	WASHABLE
		(inches)	AIR FILTER
54,000	1/3	16 X 25 X 1	16 X 25 X 1
72,000	1/2	16 X 25 X 1	16 X 25 X 1
90,000
72,000	3/4	20 X 25 X 1	20 X 25 X 1
90,000
108,000
126,000

*GAS INPUT and MOTOR HP can be found on furnace rating plate.

FILTER CABINETS

Use a bottom filter cabinet, side filter cabinet, or return-air filter grille. Field fabricated filter cabinets should allow 1 inch spacing between filter and furnace. Placing a field supplied filter directly against furnace bottom or side will decrease airflow and adversely affect furnace operation. Filter cabinets that provide correct filter spacing to ensure designed airflow are available from the manufacturer.

Manufacturer's bottom filter cabinet and upflow side filter cabinets are shown in Figures 16 and 17 respectively. See Figure 18 for floor cutout dimensions for bottom filter cabinet.

Air delivery above 1,800 CFM requires returns on both sides, a combination of side and bottom returns, or bottom return only. Use appropriate filter cabinets with these combinations.

Figure 17. Side Filter Cabinet.

Figure 16. Bottom Filter Cabinet.	Figure 18. Floor Cutout Dimensions.
Installer’s Information Manual		Page 19