Low
S.17 on Vaillant Home System

Your boiler is briefly running its pump after heating your water to safely clear away excess heat, which is a normal part of its operation.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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

From this model's manual
Verified against the Vaillant Home System installation & service manual, page 33.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

DIY fix possible

Check that your room thermostat or programmer is set to the desired temperatureEnsure at least one radiator valve is open to allow heat to dissipateMonitor the display; this code should disappear automatically after a few minutes

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