High Lockout
E4 on Viessmann Vitodens 050-W

Your boiler has stopped working because it is not receiving the correct electrical power or an internal fuse has blown.

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. Supply voltage 230 V fault. Check the supply voltage and the internal fuses.

What causes this fault?

This fault occurs when the boiler's main control board detects an issue with the incoming electrical supply or its own internal power distribution. It is typically triggered by a sudden power surge that blows a safety fuse or an underlying hardware failure within the electronic circuitry. Without a stable 230V connection, the boiler cannot safely power the ignition process or the fan, leading to a complete shutdown.

This fault is frequently seen following heavy summer storms, as lightning strikes or local power grid fluctuations can cause the electrical surges that blow internal fuses.

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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