High Lockout
d2 on Viessmann Vitodens 222-W

Your boiler has switched itself off because it has reached an unsafe temperature and needs to cool down before it can be used again.

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 fault: Temperature limiter has responded

What causes this fault?

This fault occurs when the water inside the boiler gets too hot, causing a safety sensor to trip and shut the system down to prevent damage. The most common reasons are a pump failure that stops water from moving around the system or a build-up of debris and limescale that blocks the internal pipework.

This fault is more common in autumn and winter when the heating is first turned on after a long summer break, as internal pumps can sometimes seize up from lack of use.

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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