Low
S.28 on Vaillant Atmomax

Your boiler is temporarily pausing the burner to prevent it from switching on and off too frequently while heating your water.

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 burner anti-cycling time

Shared across the range
This code is shared by the boilers in this range, which use the same control board. It may not be printed in this exact variant’s 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

Wait up to 15 minutes for the countdown timer to end naturallyEnsure your hot water taps are fully closedCheck that the water pressure gauge is within the green zone (usually 1.0 to 1.5 bar)

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