GC9C80 Service Manual

SCHEDULED MAINTENANCE
22
Upflow Models Minimum Recommended Filter Size
*0403A* 1 - 16 X 25 Side or 1 - 14 X 24 Bottom Return
*0603A* 1 - 16 X 25 Side or 14 X 24 Bottom Return
*0603B* 1 - 16 X 25 Side or Bottom Return
*0803B* 1 - 16 X 25 Side or Bottom Return
*0804B* 1 - 16 X 25 Side or Bottom Return
*0804C* 1 - 16 X 25 Side or Bottom Return
*0805C* 1 - 16 X 25 Side or Bottom Return¹
*0805D* 2 - 16 X 25 Side or 1 - 20 X 25 Bottom Return¹
*1004C* 2 - 16 X 25 Side or 1 - 20 X 25 Bottom Return
*1005C* 2 - 16 X 25 Side or 1 - 20 X 25 Bottom Return
*1205D* 2 - 16 X 25 Side or 1 - 24 X 24 Bottom Return
Downflow Models
*0403A* 2 - 10 X 20 or 1 - 14 X 25 Top Return
*0603A* 2 - 10 X 20 or 1 - 14 X 25 Top Return
*0804B* 2 - 14 X 20 or 1 - 16 X 25 Top Return
*1005C* 2 - 14 X 20 or 1 - 20 X 25 Top Return
Larger filters may be used, filters may also be centrally located
¹ = Use 2 - 16 X 25 filters and two side returns or 20 X 25 filter on bottom
return if furnace is connected to a cooling unit over 4 tons nominal capacity
A combination of one side & bottom may be used instead of both sides
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Under some conditions, the fuel or air supply can create a
nearly invisible coating on the ame sensor. This coating acts
as an insulator, causing a drop in the ame sensing signal. If
this occurs, a qualied servicer must carefully clean the ame
sensor with steel wool.
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Periodically during the heating season make a visual check of
the burner ames. Turn the furnace on at the thermostat. Wait
a few minutes since any dislodged dust will alter the normal
ame appearance. Flames should be stable, quiet, soft and
blue with slightly orange tips. They should not be yellow. They
should extend directly outward from the burner ports without
curling downward, oating or lifting o󰀨 the ports.
Check the
Burner Flames for:
1. Stable, soft and blue.
2. Not curling, floating
or lifting off.
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Before attempting to diagnose an operating fault code, run
a Heating Performance Test to determine if the heating
system is performing within 5% of the BTU input found on
the rating plate of the unit being tested. To conduct a heating
performance test, the BTU input to the unit must be calculated
(see Clocking a Gas Meter). Before clocking a gas meter,
contact your local utility to provide the caloric value (BTU
content) of the natural gas in the area.
It is also important to conrm the airow (CFM) is within the
temperature rise range (see Airow Data in spec sheet) and
external static pressure range (approximately 0.5” water
column). How-to instructions can be found in the service
manual under Checking External Static Pressure and
Checking Temperature Rise.