Vulcan-Hart GRS25 Service Manual page 8

SECTION I
GRS SERIES (ONLY) SERVICE CHECKS
WARNING: UNPLUG FRYER BEFORE SERVICING.
WARNING: SHUT OFF GAS BEFORE SERVICING.
WARNING: CERTAIN PROCEDURES IN THIS SECTION REQUIRE ELECTRICAL TEST OR
MEASUREMENTS WHILE POWER IS APPLIED TO THE FRYER. EXERCISE EXTREME
CAUTION AT ALL TIMES. IF TEST POINTS ARE NOT EASILY ACCESSIBLE, DISCONNECT
POWER, ATTACH TEST EQUIPMENT AND REAPPLY POWER TO TEST.
CONTROL SYSTEM OVERVIEW:
1. The thermopile (T.P.) provides the total control voltage for this system.
A. One side of the T.P. is connected to the common (C) of the high limit (H.L.).
B. The other side of the T.P. is connected to the normal open (N.O.) of the H.L.
C. The "C" of a the H.L. (below the H.L. trip temperature.) is connected through the
normally closed (N.C.) contact of the H.L. through wire #3 to the combination valve
pilot connection (common).
D. The other side of the pilot valve is connected through wire #4 to wire #1 to H.L. N.O.
which holds the pilot valve voltage, closing the gas valve.
2. The thermostat controls heat to the fryer.
A. One side of the millivolt supply is connected through the H.L. system as described
above to the thermostat common (wire #2 ) of the combo valve.
B. The other side of the T.P. is connected from the "N.O." of the high limit to the
thermostat through wire #1.
C. When the thermostat calls for heat (closed circuit) power from the T.P. is then
connected to the other combination valve thermostat connection through wire #2.
D. If the H.L. trips, the T.P. is connected across the 0 OHMS, the output voltage of
the T.P. drops to 0.0 millivolts and the thermostat coil of the combination (combo)
valve drops out shutting the thermostat valve.
3. Total shutdown
A. High limit trip causes 0.0 millivolts to both coils of the combo valve, causing both
valves to close.
B. Pilot relight cannot be accomplished until oil cools sufficiently to allow H.L. to close.
C. Any wire in the system being cut or broken will cause shutdown of the system.
QUICK SYSTEMS CHECK:
1. Check MV at wire #'s1&3 and with pilot lighting procedure.
A. If good and pilot lights, then pilot combination combo and H.L. are good.
B. If 0 volts (pilot will not stay lit), check H.L. and open circuit T.P. If good (300MV)
check H.L. If the H.L. is good replace the combo valve.
C. Check for voltage at disconnected T.P. If 0 volts, replace T.P. If good (300MV)
check H.L. If H.L. good, replace combo valve.
2. Turn "On" thermostat-burners should light.
A. If no burner operation, check:
-Voltage at combo valve. If voltage is good replace valve.
- Pilot relight cannot be accomplished until oil cools sufficiently to allow H.L. to close.
B. If 0 volts, check voltage between wire #2 of combo valve and of the thermostat.
If good, check resistance of thermostat and wire #3. If no voltage, check
resistance of thermostat and wire #4. If no voltage, check resistance of wire #1 to "N.O."
of high limit.
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