Low
S.20 on Vaillant Home System

Your boiler is working normally and is simply indicating that it has received a request to heat your hot water cylinder.

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 handling mode: Requirement

From this model's manual
Verified against the Vaillant Home System installation & service manual, page 33.
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

No action is required as this is an operational status message, not a fault.Wait for the boiler to finish heating the water, after which the code will change.Check your external programmer or thermostat if you did not expect the water to be heating at this time.

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