Boiler Fault Code 344 ED

Also written as 344ED — same fault.

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

Fault code 344 ED 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 exhaust gases are heating up abnormally while the water inside the system remains cold, suggesting a blockage or a failure in how the boiler transfers heat. (As reported on Worcester Bosch Greenstar CDi Compact)