Low
d.8 on Vaillant Ecomax Condensing 600/800 series

Your boiler is operating normally and is simply confirming that it has received a signal from your thermostat or timer to start heating your home.

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

External controls heat demand

From this model's manual
Verified against the Vaillant Ecomax Condensing 600 800 Series installation & service manual, page 47.
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 your room thermostat or smart controller settingsEnsure your timer or programmer is set to 'On' or 'Auto'If you do not want the heating on, adjust the temperature down on your wall controller

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