Low
D.25 on Vaillant Atmomax

Your boiler is currently heating your hot water because it has received a signal from your external thermostat or controller.

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

Hot water activation via ebus control

Shared across the range
This code is shared by the boilers in this range, which use the same control board. It may not be printed in this exact variant’s 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

Check your thermostat settings to see if hot water is scheduled to be onLower the hot water temperature on your external control to see if the code disappearsNo action is required if your hot water is working as intended

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