Medium
E321 on Baxi 400 Combi (range)

Your boiler has detected a problem with the sensor that monitors hot water temperature, which means your taps may only run cold or have inconsistent heat.

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

Hot water negative temperature coefficient (NTC) fault.

Engineer required

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

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