GC9S96 Service Manual
SCHEDULED MAINTENANCE
30
The unit being tested takes 40 seconds for the 1 cubic foot dial to make one complete revolution. Using the chart, this
translates to 90 cubic feet per hour. Based upon the assumption that one cubic foot of natural gas has 1,025 BTU’s (Check
with your local utility for actual BTU content), the
90,000 BTU/HR
92,250 BTU/HR
This example is within the 5% tolerance input and does not need adjustment.
A properly operating unit must have the BTU per hour input and CFM of air, within the limits shown to prevent short cycling
of the equipment. As the external static pressure goes up, the temperature rise will also increase. Consult the proper tables
for temperature rise limitation.
propane are calculated for 2500 BTU per cubic foot gas and with proper inlet pressures and correct piping size, full capacity
will be obtained.
With propane gas, no unit gas valve regulator is used; however, the second stage supply line pressure regulator should be
adjusted to give 10” water column with all other gas consuming appliances running.
The dissipation of the heat transferred to the heat exchanger is now controlled by the amount of air circulated over its sur-
face.
The amount (CFM) of air circulated is governed by the external static pressure in inches of water column of duct work,
cooling coil, registers, etc., applied externally to the unit versus the motor speed tap (direct drive) or pulley adjustments of
the motor and blower (belt drive).
A properly operating unit must have the BTU per hour input and CFM of air, within the limits shown to prevent short cycling
of the equipment. As the external static pressure goes up, the temperature rise will also increase. Consult the proper tables
for temperature rise limitation.