High Lockout
80:1 on Viessmann Vitodens 050-W

Your boiler has detected a communication error with its internal sensors or control unit that has lasted for more than five seconds.

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

With 5 seconds' time delay for fault message; message will be issued, if a fault persists for at least 5 seconds

What causes this fault?

This fault occurs when the boiler's central brain loses contact with the sensors that monitor water temperature. It is usually caused by a loose connection in the internal wiring or a physical failure within the temperature sensor itself, meaning the boiler can no longer safely verify how hot it is. In some cases, the control board may be unable to process the data it receives, leading to a total communication breakdown.

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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