b8 High

Boiler Fault Code b8

Also written as B8 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code b8 appears across 2 boiler brands and 12 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 broken connection or a fault with the sensor that monitors the temperature of the exhaust gases, causing the system to stop working for safety. (As reported on Viessmann Vitodens 200)

Pick your boiler brand for the b8 fix

Remeha b8 3 models Viessmann b8 9 models

Source

Information for the b8 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