344 Emergency

Worcester Bosch 344 Fault Code

The Worcester Bosch 344 fault code means: your boiler has detected that the exhaust gases are becoming dangerously hot while the water inside the unit remains cold, suggesting a blockage or a failure in the heat transfer process.. It appears on 4 Worcester Bosch models in our database.

Act immediately

Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now. This fault can be dangerous if ignored.

Technical description: ED HW: flue gas temperature rising but supply temperature not
Typical repair cost £180-350 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Worcester Bosch models that show the 344 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Worcester Bosch 344 fault code information on this page is sourced and cross-checked against the official Worcester Bosch service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026