F1 High

Boiler Fault Code F1

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code F1 appears across 10 boiler brands and 96 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler has shut down because it detected that the exhaust gases have become too hot, which is a safety feature to prevent damage or dangerous operation. (As reported on Viessmann Vitodens 333)

Pick your boiler brand for the F1 fix

Atag F1 3 models Ferroli F1 8 models Glow-worm F1 21 models Heatline F1 10 models Ideal F1 16 models Keston F1 8 models Saunier Duval F1 11 models Vaillant F1 2 models Viessmann F1 9 models Worcester Bosch F1 8 models

Source

Information for the F1 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 27 April 2026