The furnace General Aire Gage media filter air pressure gauge shows when you need to replace the air filter in your forced air heating and cooling systems.
The gauge is placed between the blower and the filter and measures the small vacuum made by air flow resistance due to the air filter. As air flows into the unit, it creates negative pressure in the blower compartment and that increased vacuum indicates the filter needs to be changed.
It is installed by drilling a 3/8″ hole small hole in the blower compartment. Due care must be taken so no damage is done to the internal heating or cooling system components. Choose an installation point in the blower compartment between the blower and filter on a vertical surface. Mount the gauge so the pressure sensing tube projects into the blower compartment.
To calibrate, put in a clean filter and run the blower fan on high speed. Adjust the calibration screw on the gauge so the indicator points to the blue, clean range.
The indicator will point to the black range as the filter become dirtier.