BoilerFaultCodes 1B High
Boiler Fault Code 1B
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 1B appears across 1 boiler brand and 7 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 200)
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 27 April 2026