346 Emergency

Boiler Fault Code 346

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code 346 appears across 3 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 is overheating because the temperature of the gases escaping through the flue is rising much faster than it should, causing the system to shut down for safety. (As reported on Worcester Bosch Greenstar CDi Compact)

Pick your boiler brand for the 346 fix

ECA 346 1 model Viessmann 346 1 model Worcester Bosch 346 4 models

Source

Information for the 346 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