![](/images/new-backgrounds/1308066/30806637x1.webp)
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",
Table 6. Recommended Filter Size
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
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.
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|
Figure 16. Bottom Filter Cabinet. |
| Figure 18. Floor Cutout Dimensions. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Installer’s Information Manual |
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| Page 19 |