GC9S96 Service Manual
SCHEDULED MAINTENANCE
28
accurate repairs resulting in fewer call backs.
Before attempting to diagnose an operating fault code, run
a Heating Performance Test to determine if the heating sys-
tem 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 calculat-
ed (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.
external static pressure range (approximately 0.5” water col-
umn). How-to instructions can be found in the service man-
ual under Checking External Static Pressure and Checking
Temperature Rise.
1.
2.
3. Once heating cycle is at a steady state (typically 15 minutes of operation), use a stopwatch to time how long it takes
the smallest unit of measure dial on the gas meter to make a full revolution. In Table 1, one cubic foot is selected. The
smallest unit of measure will vary depending on the gas meter.
CUBIC
FEET
1
1
One
In this example
we are using the
one cubic foot
dial on the gas
meter
TABLE 1