Low
S.31 on Vaillant Home System

Your boiler is not broken; it is simply in 'Summer Mode' because the heating is switched off or your thermostat is set lower than the current room temperature.

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

No heating demand: Summer mode, eBUS controller, waiting period

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

Check if your thermostat is set higher than the current room temperature.Ensure the 'Summer Mode' setting on the boiler control panel is turned off.Check your external heating controls or apps to ensure a heating schedule is active.

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Related fault codes

S.0View →S.34View →

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