High Lockout
E15 on Potterton Powermax HE

Your boiler's computer brain has encountered a serious internal error and can no longer control the heating system safely.

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

Internal control fault

What causes this fault?

This fault occurs when the boiler's main control board suffers a hardware failure and loses the ability to process instructions or monitor safety sensors. It is typically caused by electrical degradation of the components on the circuit board or a loose connection in the internal wiring. Because the 'brain' can no longer guarantee the boiler is operating safely, it shuts the entire system down as a precaution.

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

E13View →

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