BoilerFaultCodes Fb8 High
Boiler Fault Code Fb8
Also written as FB8 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code Fb8 appears across 1 boiler brand and 1 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 signal failure from a safety sensor that monitors the temperature of exhaust gases, causing the system to shut down for protection. (As reported on Viessmann Vitodens 025-W)
Pick your boiler brand for the Fb8 fix
Source
Information for the Fb8 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