Medium
E441 on Navien NCB H

Your boiler is having trouble sensing the temperature of your hot water supply, which will likely prevent it from heating your water 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

Domestic hot 2: thermistor open or short circuit

Engineer required

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

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