The G-99 Air Filter Gage provides a visual indication of the need to replace the air lters in forced
air heating and cooling systems. The gage is installed between the blower and the lter where
a slight vacuum exists due to the air ow resistance of the air lter. Air owing into the gage,
around the calibration screw, lifts a vane in proportion to the negative pressure in the blower
compartment. As the air lter loads, the vacuum increases, raising the vane to indicate a lter
change is necessary.
The gage may be calibrated in a negative pressure range from 0.1 to 0.4 inch w.c. When
properly calibrated in this range a vacuum increase of 0.10 to 0.15 inch w.c. will indicate a lter
change is necessary.
The installer should be an experienced service technician. When drilling the hole in the blower
compartment extreme care should be taken not to damage components within the heating or
cooling system.
The gage must be located where it can sense pressure conditions
in the blower compartment between the lter and the blower.
Select a location on a vertical surface enclosing the blower
compartment and drill a 3/8" hole. Remove the protective paper
from the foam adhesive strip on the back of the gage. Mount the
gage in a level position with the pressure sensing tube projecting
into the blower compartment.
The gage may be remote mounted with a maximum length
of 10 feet of 5/16 inch inside diameter vinyl tubing. Order
remote Kit part No. G99-14
Model G-99 Air Filter Gage
AIR
FILTER
BLOWER
RETURN
AIR
GAGE
®
Installation Manual
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PA T.
6190442
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General Filters, Inc. 43800 Grand River Ave., Novi, Michigan 48375 •
Toll Free (866) 476-5101
Phone: (248) 476-5100 • Fax (248) 349-2366 • www.generalaire.com
APPLICATION
PRECAUTIONS
INSTALLATION
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