Service Procedures And Adjustments; Millivolt Controls Test; Thermostat Calibration; Calibration Steps - Vulcan-Hart GHF90G Service Manual

SERVICE PROCEDURES AND ADJUSTMENTS

MILLIVOLT CONTROLS TEST

1. Verify proper gas (natural or propane) is
present.
2. Check for correct wiring and secure
connections.
3. Verify the pilot flame is adjusted properly as
outlined in Pilot Adjustment.
4. If the pilot is not lit, light pilot as outlined
under Lighting Pilot. Allow the pilot to burn for
3 to 4 minutes to stabilize.
A. If the pilot remains lit, proceed to step 6.
B. If the pilot will not remain lit, proceed to
step 5.
5. Connect DC voltmeter to terminals TH TP
and TP of combination valve. Relight the
pilot, hold the combination valve knob in and
allow the pilot to burn for 3 to 4 minutes to
stabilize.
A. If the voltage measures 450 millivolts or
greater and the pilot will not stay lit,
replace the combination valve.
B. If the voltage is less than 450 millivolts,
measure the voltage at terminals NO and
C of high limit.
1) If the voltage is 500 millivolts or
more, replace the high limit.
2) If the voltage is less than
500 millivolts, disconnect the lead
wire from terminal TH TP of the
combination valve and remeasure
voltage at the high limit.
a. If the voltage is less than
500 millivolts, replace the
thermopile.
b. If the voltage is 500 millivolts or
more, replace the combination
valve.
6. Connect DC voltmeter to terminals TP and
TH of combination valve.
7. Turn combination valve to ON. Turn
thermostat to a setting higher than the
shortening temperature.
A. If the voltage measures 150 millivolts or
more but the burners do not ignite, replace
the combination valve.
B. If the voltage is less than 150 millivolts,
measure the voltage between terminals
NO of the high limit and TP of the
combination valve.
1) If the voltage is 200 millivolts or
greater, replace the thermostat.
2) If the voltage is less than 200
millivolts, replace the combination
valve.

THERMOSTAT CALIBRATION

1. Place temperature tester in the fry tank near
the thermostat bulb.
2. Set the thermostat to 300°F and allow the
temperature to stabilize.
3. Check the temperature tester reading against
the thermostat dial reading. If there is
a variance of more than ±20°F (280°F to
320°F), calibration is required.

Calibration Steps

1. Remove thermostat knob from shaft.
2. Using a small screwdriver, rotate the setscrew
inside the hollow shaft counterclockwise to
increase the temperature or clockwise to
decrease the temperature (
approximately 18°F).
3. Allow temperature to stabilize and recheck
temperature. Repeat until the temperature
falls within the limits as stated in step 3 under
Thermostat Calibration.
4. Install thermostat knob and set dial to 350°F.
– 9 –
1 / turn equals
4