Medium
EF 349 on Worcester Bosch Heatslave

Your boiler is working harder than it should because water isn't circulating properly through the system, causing the pipes leading out of the boiler to be much hotter than those coming back.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

Technical description

Central heating boil detected – boiler operating at minimum burner load with temperature difference greater than 18°C between Flow & Return.

DIY fix possible

Check that all radiator valves are fully openBleed all radiators to remove trapped airEnsure the system pressure is between 1.0 and 1.5 bar

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