High Lockout
E28 on Main Eco Compact

Your boiler has detected a problem with the sensor that monitors the temperature of the exhaust gases, causing the system to shut down for safety.

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

Flue negative thermistor coefficient (NTC) sensor error

What causes this fault?

This fault occurs when the sensor responsible for monitoring the temperature of the exhaust gases sends an incorrect or missing signal to the boiler's control center. The most common reason is that the sensor itself has developed an electrical fault, though damaged wiring or a buildup of extreme heat in the flue system can also trigger the safety shutdown.

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

E20View →E110View →

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