High
E278 on Navien NCB 35 HE

Your boiler is having trouble measuring its own internal temperature, so it has shut down to prevent it from getting too hot or cold.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

Abnormal operation: system supply thermistor

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

E279View →

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