25 Seconds Ignition Control Gas Valve Module 100% Lock-out (Direct Factory Replacement Part) (Johnson Controls)
Sequence of Operation
G600 controls.When the G600 is used to replace an original control,
the system sequence of operation does not change.
Following is the sequence of operation for all G600s:
1. Call for Heat: The thermostat contacts close,
powering Terminal 2 on the G600.
2. Pilot Flame Checking: If the G600 detects the
presence of pilot flame (from the flame sensor)
when there should not be (i.e., before the call for
heat), the G600 will not operate.
3. Vent Damper Actuation: On models electrically
interlinked with a vent damper, the G600 powers
the vent damper motor. Once the vent damper
reaches its open position, the motor stops, and the
G600 is allowed to begin the prepurge (prepurge
models only) or trial for ignition.
4. Prepurge: The appliance prepurge fan or relay is
energized through the thermostat contacts. The
control delays for the 4-second prepurge before
simultaneously opening the pilot valve and
supplying a continual spark at the pilot burner
(models with prepurge only).
5. Trial for Ignition: During the trial for ignition, the
G600 energizes Terminal 1 and the spark
transformer, which opens the pilot valve and
activates the spark in an attempt to light the pilot
burner. If the G600 detects the presence of the
pilot flame within the trial-for-ignition time, it
proceeds to the run state. If the G600 does not
detect the presence of the pilot flame within the
trial-for-ignition time, it de-energizes all outputs
(locks out) and remains in this condition until the
thermostat is recycled. The G600AX and G600AY
have infinite trials for ignition and spark
6. Run: If pilot flame is detected within the trial for
ignition, Terminal 3 is energized and the spark
transformer is de-energized, which opens the main
valve and shuts off the spark. The pilot valve and
main valve are kept open throughout the run state.
The control remains in the run condition until the
call for heat ends or until a flameout occurs.
7. Flameout: If, during the run state, the control
detects the loss of pilot flame, it de-energizes the
main valve within 0.8 second (flame failure
response time). The pilot valve is kept open, the
spark is re-established, and another trial for
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