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SEQUENCE OF OPERATION
WHEN OPERATING CONTROL CLOSES, THE ELECTRIC SPARK AND PILOT VALVE ON EACH SIDE ARE
AUTOMATICALLY ENERGIZED. THE SENSING PROBE ON EACH OF THE PILOTS PROVES THE PRESENCE
OF THE PILOT FLAME. INTERNAL SWITCH ACTION IN EACH IGNITION MODULE DE-ENERGIZES THE SPARK
AND ENERGIZES THE MAIN GAS VALVES FOR ITS RESPECTIVE GAS TRAIN, STARTING MAIN BURNER
OPERATION. WHEN THE OPERATING CONTROL IS SATISFIED THE PILOT GAS VALVE AND MAIN GAS
VALVES FOR EACH GAS TRAIN ARE DE-ENERGIZED STOPPING BURNER OPERATION.
IN THE EVENT OF EXCESSIVE STEAM PRESSURE (STEAM BOILER) OR EXCESSIVE WATER TEMPERATURE
(WATER BOILER) THE HIGH LIMIT CONTROL WILL DE-ENERGIZE THE PILOT VALVES AND MAIN GAS VALVES
ON BOTH SIDES STOPPING BURNER OPERATION.
THE LOW WATER CUT-OFF WILL ALSO STOP BURNER OPERATION IF THE WATER LEVEL IN THE BOILER
SHOULD DROP BELOW THE LOWEST SAFE LEVEL.
SHOULD ONE OF THE PILOT FLAMES FAIL TO IGNITE OR BECOME EXTINGUISHED, THE MAIN GAS VALVES
CONTROLLED BY THAT PARTICULAR PILOT WOULD CLOSE STOPPING BURNER OPERATION ON THE
BURNERS SUPPLIED BY THAT GAS TRAIN. OPERATION OF THE BURNERS SUPPLIED BY THE SECOND GAS
TRAIN WOULD BE UNAFFECTED.
FIG. 45
LADDER WIRING DIAGRAM - 15 THRU 26 SECT. BOILERS
EI CONTROL SYSTEM