START
APPLY24 VAC ITO APPLIANCE
I THERMOSTAT ICALLS FOR HEAT
TRIAL
FOR
IGNITION
MAIN
BURNER
OPERATION
I FLAME SIGNAL
DETECTED_ NO
I INTERNAL CHECK OKAY? I NO
_YES
I • PILOT VALVE OPENS I
• IGNITER POWERED
PILOTLIGHTSAND FLAME NO
IS SENSED DURING /_-_
TRIAL FOR IGNITION?
YES
[ " IGNITER OFF I• MAIN VALVE OPENS
• WAIT FOR FLAME SIGNAL
TO DISAPPEAR
• PILOT VALVE/IGNITER
REMAIN OFF
/
• PILOT VALVE CLOSES L
/
• IGNITER OFF
[ THREE-SECOND FLAME JFAILURE RECYCLE DELAY
I FLAME SIGNAL LOST?
I THERMOSTATCALL FOR IHEAT ENDS
I • MAIN AND PILOT VALVES CLOSE
END
L/_ IGNITER WILL TURN OFF ABOUT 30 SECONDS INTO THE TRIAL FOR IGNITION.
IF THE PILOT FLAME HAS NOT LIT, IT WILL TURN BACK ON FOR THE FINAL
30 SECONDS OF THE 90 SECOND TRIAL FOR IGNITION. THE PILOT VALVE
WILL BE ENERGIZED DURING THE ENTIRE TRIAL FOR IGNmON. THIS IS
NORMAL OPERATION FOR THIS GAS IGNITION SYSTEM.
I
• MAIN AND PILOT VALVES CLOSE I
I
FLAME LOST MORE THAN NI NO
FIVE TIMES IN ONE
CALL FOR HEAT?
I l
FIVE-MINUTEDELAYRETRY I
A
Figure 19: Intermittent Ignition System Operating Sequence
!8
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