BoilerFaultCodes Fb Emergency
Boiler Fault Code Fb
Also written as FB — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code Fb appears across 2 boiler brands and 16 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 itself down as a safety precaution because it detected a possible problem with the gas supply, so please don't try to reset it repeatedly and arrange for a Gas Safe registered engineer to check it promptly. (As reported on Worcester Bosch 533 Compact)
Pick your boiler brand for the Fb fix
Source
Information for the Fb 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