Boiler Fault Code 346 / EC

Also written as 346EC — same fault.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026

Fault code 346 / EC 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 the temperature of the gases leaving the unit is rising too quickly, so it has safely shut itself down to prevent overheating. (As reported on Worcester Bosch Greenstar CDi Compact)