4 G—G770BGJ 100% Lockout, Microprocessor-Based Intermittent Pilot Ignition Control
Figure 2 illustrates the sequence of operation of the G770BGJ control.
The G770BGJ Intermittent Pilot Ignition Control is energized on a call for
heat from the system thermostat. The control will wait 0.6 second and then
energize the LED and begin the trial for ignition. Prepurge will not occur
before the first trial.
The control will activate the spark and pilot valve for up to 30 seconds in
an attempt to light the pilot burner. When the pilot burner gas ignites, the
pilot flame sensor detects pilot flame and signals the control to energize
the main valve. The spark continues for 5 seconds after the main valve is
energized. The control remains in the “run” condition, with spark
de-energized and pilot and main valves energized, until the call for heat is
removed or the flame is lost.
If the control fails to detect pilot flame by the end of the 30-second trial,
the control will allow up to two more 30-second trials for ignition with a
15-second interpurge between trials. If the pilot burner flame is not
detected by the end of the third 30-second trial, the control will enter the
lockout state. The pilot valve, spark, and LED will de-energize. The
control will remain in the lockout state until the 24 VAC power to the
control is cycled.
If the pilot flame goes out (flame loss with thermostat calling for heat)
within 10 seconds of proving, the main valve will be de-energized and the
pilot valve will remain energized. The control will immediately begin a
30-second trial for ignition. During the first second of the trial, the spark
will remain energized regardless of the presence of flame. During the
remaining (up to) 29 seconds of the trial, the control will act in the normal
manner (energize the main valve when pilot burner flame is detected and
continue to spark for 5 seconds after pilot burner flame is detected).
If the pilot flame goes out (flame loss with thermostat calling for heat)
10 seconds or more after proving, the main valve and pilot valve will
immediately be de-energized and remain off for a 15-second interpurge
period. After 15 seconds, the control will energize the spark and pilot
valve and begin a normal 30-second trial for ignition.
A total of 15 flameouts may occur during any single heating cycle.
Whether the flameout occurs less than or greater than 10 seconds after
pilot flame is proven, the total number of re-ignitions after flameout
cannot exceed 15 during any one thermostat call for heat cycle. On the
sixteenth flameout, the control goes to lockout, the LED turns off, and the
control remains in lockout until 24 VAC power to the control is cycled.
If flame is detected when the thermostat calls for heat, it must extinguish
within 30 seconds for normal operation. If flame is still present after
30 seconds, the control goes into lockout state (gas valves and spark
de-energized) and the LED turns off.
Sequence of
Operation