Low Information
D.18 on Vaillant ecoTEC

Your boiler is currently set to run the pump continuously, which is usually a configuration setting rather than a breakdown.

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

Technical description

Pump operating mode

What causes this fault?

This occurs because the boiler’s internal software has been configured to keep the pump running all the time instead of only when heat is needed. It is typically caused by a specific setting being changed during a service or installation, rather than a mechanical failure of a part. While the boiler will still provide heat and hot water, the pump will continue to circulate water around the system indefinitely.

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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