F8 High

Boiler Fault Code F8

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code F8 appears across 8 boiler brands and 41 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler has detected a problem with the gas valve not closing correctly, so it has shut down the burner for safety. (As reported on Viessmann Vitodens 050-W)

Pick your boiler brand for the F8 fix

Ferroli F8 1 model Glow-worm F8 1 model Heatline F8 3 models Ideal F8 15 models Keston F8 1 model Saunier Duval F8 1 model Viessmann F8 18 models Zanussi F8 1 model

Source

Information for the F8 fault code is sourced from the official service / installation manual for each model that displays it. Read more about how we source fault codes →

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026