Low
d.15 on Vaillant Home System

Your boiler is simply displaying the current operating speed of its internal pump as a percentage, which is a normal status message rather than an error.

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

Pump speed: Current value in %

From this model's manual
Verified against the Vaillant Home System installation & service manual.
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

No action is required as this is an information code.Press the 'Back' or 'Menu' button to return to the main temperature display.If the code persists and the boiler isn't heating, try a simple reset.

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