High Lockout
1-b8 on Worcester Bosch Greenstar 8000 Life/Style

Your boiler is struggling to control its power level correctly, which may lead to it shutting down to prevent damage.

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

Actual burner modulation: Actual burner modulation.

What causes this fault?

This fault occurs when the boiler's internal computer is unable to accurately communicate with the gas valve to throttle the flame up or down. It typically happens because the electronic signals sent to regulate the fuel flow are being interrupted or misinterpreted by a failing control board. Without the ability to precisely control its power level, the boiler shuts down as a safety 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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