High Lockout
E20 on Potterton Promax Combi HE Plus

Your boiler's temperature sensor for the heating system has stopped communicating correctly, meaning your boiler doesn't know how hot the water is and will likely stop running 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

Central Heating NTC Fault

What causes this fault?

This fault occurs when the internal sensor responsible for measuring the temperature of the water in your radiators becomes damaged or develops an electrical glitch. The most common reason is that the sensor has physically degraded or developed a short circuit, preventing it from sending a reliable reading to the boiler’s control board.

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

E28View →E50View →E110View →

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