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!
WARNING
FIRE OR EXPLOSION HAZARD CAN
CAUSE PROPERTY DAMAGE, SEVERE
INJURY, OR DEATH
Improper cleaning or reassembly may cause gas
leakage. When cleaning, ensure that control is
reassembled properly and perform gas leak test.
Regular preventive maintenance is important in applica-
tions that place a heavy load on system controls, such as in the
commercial cooking and agricultural and industrial indus-
tries because:
• The equipment operates 100,000-200,000 cycles per
year in many such applications, particularly commer-
cial cooking. Such heavy cycling can wear out the gas
control in one to two years.
• Exposure to water, dirt, chemicals and heat can dam-
age the gas control and shut down the control system.
The maintenance program should include regular
checkout of the gas control, see Start-Up and Checkout,
page 0, and the control system, see the appliance
manufacturer's literature.
Maintenance frequency must be determined individu-
ally for each application. Some considerations are:
• Cycling frequency. Appliances that may cycle 100,000
times annually should be checked monthly.
• Intermittent use. Appliances that are used seasonally
should be checked before shutdown and again before
the next use.
• Consequence of unexpected shutdown. Where the cost
of an unexpected shutdown would be high, the system
should be checked more often.
• Dusty, wet, or corrosive environment. Since these
environments can cause the gas control to deteriorate
more rapidly, the system should be checked more
often.
The gas control should be replaced if:
• It does not perform properly on checkout or trouble-
shooting.
• The gas control knob is hard to turn or push down, or
it fails to pop back up when released.
• The gas control is likely to have operated for more than
200,000 cycles.
!
WARNING
FIRE OR EXPLOSION HAZARD CAN
CAUSE PROPERTY DAMAGE, SEVERE
INJURY OR DEATH
Do not disassemble the gas control; it contains no
replaceable components. Attempted disassembly
or repair may damage the gas control.
Maintenance
Service
!
CAUTION
Do not apply a jumper across or short the valve coil
terminals. This may burn out the heat anticipator in
the thermostat.
IMPORTANT: Allow 60 seconds after shutdown before re-
energizing step-opening model to ensure lightoff at step
pressure.
IF THE PILOT BURNER FLAME WILL NOT LIGHT
1. Ensure the main gas supply valve is open and the pilot
gas supply line is purged of air.
2. Attempt to light pilot burner flame following proce-
dures in Light the Pilot Burner Flame, page 0. If pilot burner
flame still will not light:
a. Check the pilot gas adjustment screw. If closed,
readjust the pilot flame. Refer to Adjust the Pilot
Burner Flame, page 0.
b. Perform the Gas Leak Test at the compression
fitting. If a gas leak is detected, replace the old
compression fitting or tighten the newly installed
one. Refer to Fig. 1.
c. Ensure that the pilot burner tubing or pilot burner
orifice is not clogged.
IF THE PILOT BURNER FLAME GOES OUT WHEN
THE GAS CONTROL KNOB IS RELEASED
1. Ensure the gas control knob is held in at least one
minute to allow the thermocouple time to heat.
2. Check the pilot burner flame adjustment. Refer to
Adjust the Pilot Burner Flame, page 0.
3. Check the wiring between the thermocouple and the
gas control valve operator.
4. Ensure thermocouple connection to the power unit is
tightened 1/4 turn beyond finger tight.
5. If pilot burner flame still goes out, measure the open
and closed thermocouple output voltage. Compare it to the
acceptable range charts in the thermocouple specifications or
in the Gas Controls Handbook. Replace the thermocouple if
voltages are outside the acceptable range.
6. Check the power unit resistance. If higher than 11
ohms, replace the gas control.
IF THE MAIN BURNER WILL NOT COME ON WITH
A CALL FOR HEAT
1. Ensure the gas control knob is in the ON position.
2. Adjust the thermostat several degrees above room
temperature.
3. Use an ac voltmeter to measure the voltage across
terminals TH and TR. If:
a. no voltage is present, check the control circuit for
proper operation.
b. 24 Vac is present, but first operator did not click
open, check for excessive inlet gas pressure. If inlet
gas pressure is correct, replace the gas control.
4. Measure the open and closed thermocouple output
voltages and compare to the acceptable range charts in the
thermocouple specifications or in the Gas Controls Hand-
book. Replace the thermocouple if voltages are outside the
acceptable range.
5. Measure the open and closed thermocouple output
voltages and compare to the acceptable range charts in the
thermocouple specifications or in the Gas Controls Hand-
8
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