Low
d.22 on Vaillant Home System

This is actually a status indicator rather than a fault, showing whether your boiler 'thinks' your hot water tank is currently asking for heat.

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 hot water request: off=No current requirement, on=Current requirement

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 hot water cylinder thermostat and time clock to ensure they are set to 'on'.Open the hot water tap to see if the status changes from 'off' to 'on'.No action is required if your hot water is currently working as intended.

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Related fault codes

d.23View →d.25View →S.24View →

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