Medium
E761 on Navien NCB 28 HE

Your boiler is having trouble detecting the temperature of the water reserved for your hot water system, which may prevent it from heating your taps correctly.

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

Abnormal operation: Pre-Heat Aquastat

Engineer required

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

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