High Lockout
E20 on Potterton Promax System HE Plus

Your boiler has lost its connection to the sensor that monitors the temperature of the water in your heating system, causing the boiler to stop working.

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 boiler's control board can no longer read the temperature of the water leaving the unit. The most common cause is a failed internal sensor that has either burnt out or developed an electrical fault, though it can also be triggered by a loose or damaged connection in the internal wiring.

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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