Boiler burner lockout during ignition
When a burner locks out during the ignition (pilot) trial, the control did not prove flame within its fixed trial time. Because the main fuel valves have not opened yet, the cause is almost always in the ignition system, the pilot fuel supply, the light-off air flow or the flame detector.
Diagnose this with AI
Try Free Boiler Diagnostic Upload a photo of the alarm screen, the fault history or a data export. InduQT compares the evidence and suggests the next useful checks.
Where it shows up
- A lockout naming the pilot or ignition trial stage (abbreviations such as PTFI are common).
- Repeated failed starts at the same point of the sequence.
Likely causes and how to tell them apart
1No or weak spark
- Points to it
- No ignition noise or visible spark during the trial.
- Check
- Inspect the electrode, insulator and gap; check the ignition transformer and its lead, following the burner manual.
2Pilot gas not reaching the burner
- Points to it
- Spark present but no pilot flame; pilot regulator or valve recently serviced.
- Check
- Check pilot gas pressure during the trial and confirm the pilot valve opens.
3Too much or too little light-off air
- Points to it
- Pilot lights briefly then blows out, or lights poorly after damper work.
- Check
- Check the low-fire damper position and linkage against the commissioning settings.
4Detector does not see the pilot
- Points to it
- Pilot is visible but the flame signal stays below the control’s minimum.
- Check
- Clean and re-sight the scanner, or check the flame rod position and grounding.
Diagnostic sequence
- Confirm the stageMake sure the lockout is during the ignition or pilot trial, not the main-flame trial.
- Watch one startWith a qualified technician, observe a start through the sight glass: spark, pilot flame and the flame signal reading.
- Split the problemNo spark: ignition. Spark but no flame: pilot fuel or air. Flame but no signal: detection.
- Record and compareNote pressures and the flame signal so the next attempt can be compared after each change.
Evidence to collect
- Photo of the lockout message
- Control and scanner model
- Pilot gas pressure reading
- Flame signal value during a trial
Work on fuel trains, burners, pressure vessels and electrical equipment must be done by qualified personnel following the manufacturer’s documentation and local codes. Never bypass a safety device or interlock.