Boiler displays F29, flame goes out during operation, intermittent hot water or heating

Safety: If the boiler repeatedly loses flame, stop using it and arrange professional inspection. Isolate power and gas if you smell gas.

• Check gas supply stability: Note if other gas appliances also cut out. If so, contact your gas supplier.
• Inspect flue terminal: Ensure the external flue is clear and not exposed to strong wind recirculation (e.g., under a balcony) that could blow out the flame.
• Check condensate pipe: Ensure the condensate trap and external pipe are not blocked or frozen, which can affect combustion.
• Engineer tasks:
  • Test flame sensor and clean or replace as needed.
  • Check gas valve modulation and burner pressure.
  • Inspect combustion chamber for signs of water ingress from condensate.

Flame loss faults must be properly diagnosed to prevent unsafe operation.