Low Information
S.27 on Vaillant ecoTEC Pro 24

Your boiler is briefly running the internal pump after you have finished using hot water to safely move heat away from the system.

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

DHW mode: Pump overrun. The pump overrun for domestic hot water mode is activated.

What causes this fault?

This occurs when you finish using a hot tap and the boiler needs to dissipate the high levels of residual heat left inside the heat exchanger. The internal pump continues to run for a short period to move this hot water away, preventing the internal components from overheating or becoming damaged by trapped heat. It is a normal safety function rather than a failure of any specific part.

DIY fix possible

This fault may be fixable without an engineer. Check your manual first.

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