BoilerFaultCodes H03 Low
Boiler Fault Code H03
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code H03 appears across 1 boiler brand and 3 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler is simply reminding you that it is time for its annual safety service to ensure it continues running efficiently and safely. (As reported on Worcester Bosch Greenstar i)
Pick your boiler brand for the H03 fix
Source
Information for the H03 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