BoilerFaultCodes 347 / E3 High
Boiler Fault Code 347 / E3
Also written as 347E3 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 347 / E3 appears across 1 boiler brand 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 detected that hot water is flowing in the wrong direction or returning too hot, suggesting a blockage or a pump issue that is preventing the system from heating your home properly. (As reported on Worcester Bosch Greenstar CDi Compact)
Pick your boiler brand for the 347 / E3 fix
Source
Information for the 347 / E3 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