Low
d.25 on Vaillant Home System

This is a status indicator showing whether your boiler is currently set to pre-heat your hot water tank or maintain a warm start for your taps.

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

Status of the requirement to reheat the cylinder or for the hot water warm start from the eBUS thermostat: off=Function deactivated, on=Function activated

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

Check your external room thermostat or cylinder stat settingsAdjust the hot water schedule on your boiler controls if your water is not reaching the desired temperatureConsult your user manual to see if you have manually disabled the 'Warm Start' function

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d.22View →S.20View →S.24View →

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