Low
S.17 on Vaillant ecoTEC Pro / ecoTEC Plus Regular

Your boiler is busy cooling itself down after providing hot water, but the water isn't moving through the system as quickly as it should.

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.

What the manual says

Manufacturer manual

DHW mode – pump overrun error

From this model's manual
Verified against the Vaillant Ecotec Pro Ecotec Plus Regular installation & service manual, page 59.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

What causes this fault?

This status occurs when the boiler is trying to move excess heat away from the internal heat exchanger after you have finished using hot water. It usually happens because the water isn't circulating quickly enough through the internal bypass or the pipes to cool the system down. The most common reasons are a pump that is starting to struggle or a slight internal blockage that restricts the flow of water.

DIY fix possible

Check that at least two radiator valves are fully open to allow water flowEnsure your boiler pressure is between 1.0 and 1.5 bar on the displayRestart the boiler to see if the status code clears

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