Low
S.11 on Vaillant ecoMAX 635

Your boiler is currently working as it should to heat up your hot water tank.

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

Pump and fan running (hot water operation)

From this model's manual
Verified against the Vaillant Ecomax 613 installation & service manual, page 45.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

What causes this fault?

This is actually not a fault, but a status code informing you that the boiler is currently busy heating your hot water cylinder. It occurs when the system's sensors detect that the water in your tank has cooled down and the boiler has fired up specifically to replenish that heat.

DIY fix possible

This fault may be fixable without an engineer. Check your manual first.

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