BoilerFaultCodes 1B High
Boiler Fault Code 1B
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 1B appears across 2 boiler brands and 2 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 down because it is struggling to discharge exhaust fumes safely or is detecting a significant lack of air flow. (As reported on Viessmann Vitodens 111-W)
Pick your boiler brand for the 1B fix
Source
Information for the 1B 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