ELECTRICAL OPERATION
CONTROL SYSTEM DESCRIPTION
1.The thermopile (TP) provides the total control voltage for this system.
A.One side of the thermopile is connected to the common (C) of the high limit (HL).
B.The other side of the thermopile is connected to the normally open (NO) contacts of the high limit.
C.The common of the high limit (below the high limit trip temp.) is connected through the normally closed (NC) contacts of the high limit, 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 the high limit normally open contacts which hold the pilot valve open.
1)If the high limit trips, connection is made from the common to the normally open contacts, turning off pilot valve voltage. The gas valve closes.
2.Thermostat Control.
A.One side of the millivolt supply is connected through the high limit system, as described above, to the thermostat common (wire 3) of the combination valve.
B.The other side of the thermopile is connected from the normally open contacts of the high limit to the thermostat through wire 1.
C.When the thermostat calls for heat (closed circuit) power from the thermopile is then connected to the other combination valve thermostat connection through wire 2.
D.If the high limit trips, the thermopile is connected across zero ohms, the output voltage of the thermopile drops to 0.0 millivolts, and the thermostat coil of the combination valve drops out, shutting the thermostat valve.
3.Total Shutdown.
A.When the high limit trips, 0.0 millivolts will read across both coils of the combination valve, causing both valves to close.
B.Pilot relight cannot be accomplished until oil cools sufficiently to allow high limit to close.
C.If any wire in the system is cut or broken, the system will shut down.
SYSTEM CONDITION QUICK CHECK
PROCEDURES
1.Use the Pilot Lighting procedure and check millivolts (mV) at wires 3 and 4.
A.If the pilot lights, then pilot combination and high limit are good.
B.If the pilot will not stay lit, check high limit and open the thermopile circuit. It should read 300 mV; if there are Ø volts, check high limit. If the high limit is good, replace combination valve.
C.Check for voltage at disconnected thermopile. It should read 300 mV; if there are Ø volts, replace thermopile. Check high limit. If the high limit is good, replace combination valve.
2.Turn on thermostat; burners should light.
A.If the burner does not light, check the following:
1)Voltage at combination valve at wires 2 and 4.
2)If correct voltage is present, then check combination valve.
3)If there are Ø volts, check voltage between wire 3 of combination valve and wire 1 of thermostat. If correct voltage is present, then check resistance of thermostat and wire 32. If there is no voltage, check resistance of wire 1 to normally open contacts of high limit.
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