BoilerFaultCodes 221 High
Boiler Fault Code 221
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 221 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 disconnected or faulty internal temperature sensor, so it has shut down as a precaution to prevent the system from overheating. (As reported on Worcester Bosch Greenstar CDi Compact)
Pick your boiler brand for the 221 fix
Source
Information for the 221 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