b5 High

Boiler Fault Code b5

Also written as B5 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code b5 appears across 3 boiler brands and 6 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler has experienced an internal communication error or processor glitch that is preventing it from running properly. (As reported on Viessmann Vitodens 222-F)

Pick your boiler brand for the b5 fix

Ideal b5 1 model Viessmann b5 4 models Worcester Bosch b5 1 model

Source

Information for the b5 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