Generalaire 4002 G99 Media Air Cleaner Gage 0.1 to 0.4 Inches W.C.
The Gauge may be calibrated in a negative pressure range from 0.1 to 0.4 inches of w.c. When Properly Calibrated in this range a vacuum increase of 0.10 to 0.15 inches w.c. will indicate a filter change is necessary.
The G-99 Air filter Gage provides a visual indication of the need to replace the air filters on forced air heating and cooling systems. The gage is installed between the blower and the filter where a slight vacuum exists due to the air flow resistance of the air filter. Air flowing into the gage, around the calibration screw, lifts a vane in proportion to the negative pressure in the blower compartment. As the air filter loads, the vacuum increases, raisng the vane to indicate a filter change is necessary.
