BoilerFaultCodesWorcester Bosch EF349 Fault Code
The Worcester Bosch EF349 fault code means: your boiler is overheating because water isn't moving through the system quickly enough, forcing it to run at its lowest power to prevent damage.. It appears on 1 Worcester Bosch model in our database.
Technical description: Central heating boil detected – boiler operating at minimum burner load with temperature difference greater than 18°C between Flow & Return.
What causes the Worcester Bosch EF349 fault?
This fault occurs when the water inside your boiler heats up too quickly because it isn't circulating around your radiators fast enough. The most common reasons are a failing internal pump that can no longer push the water, or a buildup of sludge and debris that has created a partial blockage in the main heat exchanger.
This fault often appears during the first cold snap of autumn when the heating is turned on after being dormant all summer, which can cause internal pump components to seize.
DIY fix possible
Check that all radiator valves (TRVs) are fully openEnsure the central heating system pressure is between 1.0 and 1.5 barBleed all radiators to remove trapped air
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Gas Safe Register →Worcester Bosch models that show the EF349 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch EF349 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 27 April 2026