8
!
Maintenance
WARNING
FIRE OR EXPLOSION HAZARD CAN
CAUSE PROPERTY DAMAGE, SEVERE
INJURY, OR DEATH
Improper cleaning or reassembly may cause gas
leakage. When cleaning, assure that control is
reassembled properly and perform gas leak test.
Regular preventive maintenance is important in appli-
cations that place a heavy load on system controls, such as
in the commercial cooking and agricultural and industrial
industries because:
• In many such applications, particularly commercial
cooking, the equipment operates 100,000-200,000
cycles per year. Such heavy cycling can wear out the
gas control in one to two years.
• Exposure to water, dirt, chemicals and heat can
damage the gas control and shut down the control
system.
The maintenance program should include regular check-
out of the gas control as described in the Start-up and
Checkout section, and the control system as described in
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 during checkout or
troubleshooting.
• 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.
!
Service
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.
!
CAUTION
Do not apply a jumper across or short the valve
coil terminals. This may burn out the heat antici-
pator in the thermostat.
IMPORTANT: Allow 60 seconds after shutdown before
re-energizing step-opening model to assure lightoff
at step pressure.
IF THE PILOT BURNER FLAME WILL NOT LIGHT
1. Assure 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 6. If pilot
burner flame still will not light:
a. Check the pilot gas adjustment screw. If closed,
readjust the pilot flame.
b. Perform the Gas Leak Test at the compression fit-
ting. If a gas leak is detected, replace the old com-
pression fitting or tighten the newly installed one.
Refer to Fig. 4.
c. Assure 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. Assure 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 6.
3. Check the wiring between the thermocouple and the
gas control valve operator.
4. Assure thermocouple connection to the power unit is
tightened one-fourth 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 thermo-
couple if voltages are outside the acceptable range.
6. Check the power unit resistance. If above 11 ohms,
replace the gas control.
IF THE MAIN BURNER WILL NOT COME ON
WITH A CALL FOR HEAT
1. Assure 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 L1 and L2:
a. If no voltage is present, check the control circuit for
proper operation.
b. If voltage 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.
IF THE MAIN BURNER IS OVERFIRING
Adjust the gas control pressure regulator to the correct
pressure. If the regulator cannot be adjusted and supply
pressure is in the normal range, replace the gas control.