F5 High

Boiler Fault Code F5

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code F5 appears across 10 boiler brands and 47 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler has got too hot and stopped working to protect itself, likely because the water isn't moving through the system properly. (As reported on Vaillant ecoMAX Pro 28E)

Pick your boiler brand for the F5 fix

British Gas F5 1 model Ferroli F5 5 models Glow-worm F5 10 models Heatline F5 6 models Ideal F5 12 models Keston F5 3 models Saunier Duval F5 4 models Vaillant F5 2 models Viessmann F5 3 models Zanussi F5 1 model

Source

Information for the F5 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 7 July 2026