Part Number 550-141-807/0298
11
Flame Guardian WMBC-1A Electronic Pilot System – IRI
V
Sequence of operation
1. Operating control begins startup sequence:
a. Limit control contacts are closed.
b. Purge timer is energized.
2. Flame safeguard control pilot circuit energizes after 2.0 seconds.
a. Pilot gas valve opens.
b. Ignition transformer energizes.
c. Yellow “pilot on” lamp lights.
d. Pilot ignition spark begins.
e. Pilot ignites.
f.
Pilot flame proves.
3. Flame safeguard control energizes main flame circuit:
a. Blue “gas valve on” lamp lights.
b. Gas control train energizes.
c. Downstream gas valve opens to low-fire position.
d. Main burners ignite, operate at low fire.
4. Ignition transformer de-energizes after 10-second trial for ignition.
5. Pilot de-energizes after 10-second trial for main flame. Yellow “pilot on” lamp goes out.
6. Main flame sensor proves main burner operation at low fire.
7. Flame safeguard control energizes downstream gas valve to high-fire (through firing rate
control, when used):
a. Main burners operate at high fire.
b. Main burners operate at low fire when water temperature or pressure reaches setting of
firing rate control, when used.
8. Boiler shuts down when operating control satisfied.
9. Flame safeguard control lockout circuit energized if pilot is not proved during start-up or if
main flame is not proved during run sequence.
a. Flame safeguard control locks out on safety.
b. Red “alarm” lamp, alarm relay, and alarm bell energize. Silencing switch can shut off
alarm bell.
c. Alarm relay de-energizes purge timer.
d. Press reset button on flame safeguard control to permit normal start-up after correcting
lockout condition.
e. Normal start-up resumes after purge timer automatically resets (5 minute enforced
wait).
