Low
S.27 on Vaillant ecoTEC Plus 620

Your boiler is briefly running the internal pump after providing hot water to help cool down the internal components.

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

DHWmode:Pumpoverrun

From this model's manual
Verified against the Vaillant Ecotec Plus 615 installation & service manual, page 38.
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 occurs when the boiler finishes heating your tap water and needs to dissipate the high heat remaining inside the heat exchanger. The internal pump continues to run for a short period to move this residual heat away from the sensitive internal components and out into the pipework. This is a normal safety function designed to protect the boiler's lifespan rather than a sign of a mechanical failure.

This status may appear more frequently during the summer months when the boiler is only used for hot water and the central heating system is cold.

DIY fix possible

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

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