High Lockout
1F on Viessmann Vitodens 111-W

Your boiler has stopped working because the burner isn't lighting correctly, likely due to a problem with the internal airflow or the ignition system.

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

Burner blocked

What causes this fault?

This fault occurs when the boiler's control system detects that the burner cannot sustain a stable flame after several attempts. It is usually caused by a lack of proper airflow or an issue with the sensors that verify the flame is safe to stay on. The most common reasons are worn-out ignition components or a build-up of debris within the burner chamber that prevents a clean light-up.

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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