Low
S.31 on Vaillant Turbomax 824/828

Your boiler is perfectly fine and is simply set to 'summer mode,' meaning it is currently turned off so that it only provides hot water rather than central heating.

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

Summer mode (heating control knob in off position)

From this model's manual
Verified against the Vaillant Turbomax 824 828 installation & service manual, page 38.
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

Locate the radiator/heating temperature dial on the front control panel.Turn the dial clockwise away from the off position to your desired heat setting.The boiler will automatically exit summer mode and S.31 will disappear from the display.

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