Low
d.17 on Vaillant ecoFIT Pure 425

Your boiler is currently set to manage its operation based on the temperature of the water returning from your radiators rather than the water leaving the boiler.

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

Heating control (off=Flow temperature, on=Return temperature)

From this model's manual
Verified against the Vaillant Ecofit Pure 830 installation & service manual, page 29.
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

Navigate to the 'd.17' setting in the installer level menu.Change the value from '1' (Return) back to '0' (Flow) if you prefer standard operation.Press the 'Menu' or 'Tick' button to save the setting.

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