F.29 flame loss; burner lights briefly then goes out, unit locks out

Safety: Only a qualified gas engineer should work on combustion, gas, and flue components.

• Check gas supply: Confirm stable gas pressure and that other gas appliances are unaffected. Low pressure can cause flame loss.
• Inspect burner and injectors: Remove and clean the burner assembly. Check for rust, debris, or partial blockage of injectors. Clean or replace as necessary.
• Check ionisation electrode: Inspect the flame sensing electrode for cracks or deposits. Clean gently and ensure correct positioning in the flame. Replace if damaged.
• Verify earthing: Ensure the appliance has a solid earth connection; poor earthing can affect flame detection.
• Inspect flue system: Check for obstructions, incorrect slope, or water ingress in the flue. Rectify any installation issues.
• Test gas valve modulation: Confirm that the gas valve modulates correctly and does not shut prematurely. Replace if faulty.
• Reset and observe: After corrective actions, reset the heater and monitor several heating cycles to ensure stable flame.