High Lockout
28 on Potterton Promax Combi HE Plus

Your boiler has stopped working because its internal computer board is either the wrong version for this model or has been configured incorrectly.

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

Incorrect PCB fitted

What causes this fault?

This fault occurs when the boiler's main control board is unable to identify the specific model it is installed in. It most commonly happens after a repair where a new circuit board has been fitted but the specific software key has not been inserted, or if a technician has accidentally programmed the wrong settings into the system.

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 →

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