Boiler ignites with a loud bang or pop, sometimes shaking the flue or casing.
Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
Possible Causes
How to Fix / Troubleshooting
Safety first: Delayed ignition can be dangerous. Turn off the boiler and gas supply at the appliance isolation valve and call a Gas Safe engineer.
Homeowner checks:
- Do not repeatedly reset or attempt to run the boiler if loud bangs occur.
- Ensure the gas meter emergency control valve is fully open, but leave further checks to an engineer.
Engineer actions:
- Inspect and clean the burner and ignition electrodes; set correct gap and position.
- Check gas inlet and burner pressures during ignition.
- Test gas valve opening characteristics and replace the Worcester gas valve if sluggish.
- Verify correct flue installation and combustion settings.
Do not use the boiler until delayed ignition has been fully resolved.
Repair Difficulty
Required Part
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