BoilerFaultCodes 347 High
Boiler Fault Code 347
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 347 appears across 2 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 detected that the water returning from your radiators is hotter than the water leaving the boiler, which suggests a sensor error or a blockage preventing proper circulation. (As reported on Worcester Bosch Greenstar 12i System)
Pick your boiler brand for the 347 fix
Source
Information for the 347 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