High Lockout
E28 on Potterton Assure Combi / System

Your boiler has stopped working because a sensor that monitors the temperature of the exhaust gases has failed or is reporting an error.

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 temperature coefficient (NTC) fault

What causes this fault?

This fault occurs when the sensor responsible for monitoring the heat of the exhaust gases sends an incorrect or missing signal to the boiler's main control board. The most common reason is that the sensor itself has developed an electrical internal failure or the wiring connecting it to the system has become loose or damaged.

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 →E50View →E110View →

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