High Lockout
E5 on Viessmann Vitodens 100-W / 200-W

Your boiler has stopped working because it cannot confirm that a flame is burning safely, leading to a complete shutdown for your protection.

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 in fault position. Internal fault. Check the flame monitoring (ionisation electrode and lead).

What causes this fault?

This fault occurs when the boiler's control system cannot detect a steady flame after the ignition process has started. The most common reason is that the sensor responsible for 'seeing' the flame is either dirty, worn out, or damaged, causing the boiler to shut down as a safety precaution. In some cases, it can also be caused by an inconsistent gas supply or a failing electronic control board.

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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