Gas Flow
To check for proper gas flow to the combustion
chamber, determine the Btu input from the appliance
rating plate. Divide this input rating by the Btu per cubic
feet of available gas. Result is the required number of
cubic feet per hour. Determine the flow of gas through
the gas meter for two minutes and multiply by 30 to get
the hourly flow of gas.
Gas Pressure Adjustment
1 − Check gas line pressure with unit firing at maximum
rate. A minimum of 5" (127mm) w.c. for natural gas
should be maintained for proper unit operation.
2 − After line pressure has been checked and adjusted,
check regulator pressure. Adjust manifold pressure
to values specified on the unit rating plate. See
figure 8. If unit is installed at an altitude greater than
7500 feet (2286m), unit must be derated by four
percent for each additional 1000 feet (305m) above
7500 feet (2286m).
Limit Control Switch
The limit control switch(es) are factory-set and are not
field−adjustable.
Combustion Air Pressure Switch
This pressure switch checks for proper combustion air
inducer operation before allowing an ignition trial. The
switch is factory−set and no field adjustment is necessary.
Service
LUBRICATION
Combustion air inducer motor bearings are pre−lubricated
and sealed. No further lubrication is necessary.
BURNERS
1 − Periodically examine burner flames for proper
appearance during the heating season.
2 − Before each heating season examine the burners
for any deposits or blockage that may have
occurred.
3 − Clean burners as follows:
a − Turn off both electrical and gas supplies to unit.
b − Disconnect gas supply piping, high tension
and sensor leads. Remove gas manifold.
Remove burner tray.
c − Clean burners as necessary. Make sure that
burner heads line up properly to ensure flame
crossover. Check spark gap on electrode and
adjust if required. The gap should be
between 0.110" and 0.140" (2.8 mm to 3.6
mm). The gap may be checked with
appropriately sized twist drills or feeler
gauges.
d − Reinstall burner tray, gas manifold, high
tension and sensor leads. Reconnect gas
supply piping.
e − Restore electrical power and gas supply.
Follow lighting instructions to light unit. Check
burner flame.
Turn off gas and electrical power to unit before per-
forming any maintenance or service operations on
this unit. Remember to follow lighting instructions
when putting unit back into operation after service
or maintenance.
IMPORTANT
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