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10
S8701/S8702 DIRECT SPARK IGNITION CONTROLS
START
SPARK STOPS WHEN
BURNER IS LIT
SYSTEM RUNS UNTIL
CALL FOR HEAT ENDS
CALL FOR HEAT ENDS:
SYSTEM SHUTS OFF
TROUBLESHOOTING ENDS
TURN THERMOSTAT TO
CALL FOR HEAT
TURN GAS SUPPLY OFF.
POWER TO UNIT
(24 VAC NOMINAL)
SAFE START CHECK OK.
J, K, L, AND M MODELS
PREPURGE DELAY.
CHECK LINE VOLTAGE POWER, LOW VOLTAGE TRANSFORMER, LIMIT CONTROLLERS,
THERMOSTATS AND WIRING. ALSO, AIR PROVING SWITCH ON PREPURGE
SYSTEMS (SEE FIGS. 4 AND 5).
UNIT LOCKS OUT ON POWER UP. CHECK FOR FLAME AT EACH BURNER. IF FLAME
IS PRESENT, SHUT OFF GAS SUPPLY AND REPLACE GAS CONTROL. IF NOT, REPLACE
IGNITION CONTROL.
SPARK ACROSS IGNITER OR
IGNITER/SENSOR GAP.
NO PREPURGE DELAY. REPLACE J, K, L, OR M UNIT.
M18059
NOTE: BEFORE TROUBLESHOOTING, FAMILIARIZE YOURSELF
WITH THE START-UP AND CHECKOUT PROCEDURE.
• TURN OFF GAS SUPPLY.
• PULL IGNITION LEAD
AND CHECK SPARK AT
SPARK TERMINALS.
SPARK OKAY?
• CHECK IGNITION CABLE, BURNER GROUND WIRING, CERAMIC INSULATOR AND GAP,
AND CORRECT.
• CHECK BOOT OF THE IGNITION CABLE FOR SIGNS OF MELTING OR BUCKLING. TAKE
PROTECTIVE ACTION TO SHIELD CABLE AND BOOT FROM EXCESSIVE TEMPERATURES.
• CHECK FOR 24 VAC ACROSS VALVE AND VALVE TERMINALS DURING TRIAL FOR
IGNITION PERIOD. IF NO VOLTAGE, REPLACE UNIT.
• Q347, Q354 OR Q366 MAY BE OUT OF POSITION.
• CHECK ELECTRICAL CONNECTIONS BETWEEN UNIT AND GAS CONTROL. IF OKAY,
REPLACE GAS CONTROL.
NOTE: IF UNIT GOES INTO LOCKOUT, RESET SYSTEM.
• CHECK CONTINUITY OF SENSOR CABLE(S) AND GROUND WIRES.
NOTE: IF GROUND IS POOR OR ERRATIC, SHUTDOWNS MAY OCCUR OCCASIONALLY
EVEN THOUGH OPERATION IS NORMAL AT TIME OF CHECKOUT.
• CHECK FOR EXCESSIVE HEAT AT SENSOR INSULATOR(S)
(TEMPERATURE ABOVE 1000 °F (538 °C) CAUSES SHORT TO GROUND).
• IF CHECKS ARE OKAY, REPLACE UNIT.
NOTE: IF UNIT GOES INTO LOCKOUT, RESET SYSTEM.
• CHECK CONTINUITY OF SENSOR CABLE(S) AND BURNER GROUND WIRES.
• CHECK THAT BURNER FLAME COVERS ALL ELECTRODES (ON BOTH BURNERS IF S8702).
• CHECK 24V GROUND CONNECTION TO BURNER.
• IF CHECKS ARE OKAY, REPLACE UNIT.
• CHECK FOR PROPER TEMPERATURE CONTROLLER OPERATION.
• REMOVE VALVE LEAD AR UNIT; IF VALVE CLOSES, RECHECK TEMPERATURE
CONTROLLER AND WIRING; IF NOT, REPLACE GAS CONTROL.
REPLACE UNIT
REPEAT PROCEDURE UNTIL TROUBLE FREE OPERATION IS OBTAINED.
NOTES: B, D, J, AND K MODELS GO THROUGH ONE (1) TRIAL FOR IGNITION PERIOD BEFORE LOCKOUT.
E, F, L, AND M MODELS GO THROUGH THREE (3) TRIAL FOR IGNITION PERIODS WITH A 30 SECOND
INTERPURGE PERIOD BETWEEN TRIAL FOR IGNITION PERIODS BEFORE LOCKOUT AND THEN RETRY AUTOMATICALLY
AFTER ONE (1) HOUR.
LOCKOUT = VALVE CLOSED PLUS SPARK OFF PLUS ALARM ACTIVATED PLUS LED ON STEADY.
S8702 MODELS SPARK AND SENSE FLAME ON TWO SEPARATE BURNERS.
FLAME MUST BE SENSED ON BOTH BURNERS DURING TRIAL FOR IGNITION ON THE UNIT WILL LOCKOUT.
MAIN BURNER(S) LIGHTS
NO
YES YES
YES
YES
YES
YES
YES
YES
YES
YES
NO
NO
NO
NO
NO
NO
NO
NO
Fig. 9. S8701/S8702 Direct Spark Ignition System Troubleshooting Guide