Low
S.28 on Vaillant ecoTEC pro 30 H combi A VUW GB 306/5-3

Your boiler is temporarily delaying heating hot water to protect itself from turning on and off too frequently, which is a normal safety feature and usually resolves itself within a few minutes.

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

The anti-cycling time for domestic hot water mode is activated.

From this model's manual
Verified against the Vaillant/Vaillant Ecotec Pro Ecotec Plus Combi installation & service 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 5 to 10 minutes for the built-in delay timer to naturally expire.Check that your hot water taps are fully closed and not dripping.If the boiler remains stuck, try turning the hot water temperature down slightly on the control panel.

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Related fault codes

S.27View →S.30View →F.20View →

All 82 fault codes on the ecoTEC pro 30 H combi A VUW GB 306/5-3

Seeing a different code? Every code this model can display, in one place.

F.00F.01F.10F.11F.20F.22F.23F.24F.25F.26F.27F.28F.29F.32F.49F.61F.62F.63F.64F.65F.67F.68F.70F.71F.72F.73F.74F.75F.77F.78F.83F.84F.85S.00S.01S.02S.03S.04S.05S.06S.07S.08S.10S.11S.13S.14S.15S.16S.17S.20S.21S.22S.23S.24S.25S.26S.27S.30S.31S.32S.34S.39S.40S.41S.42S.46S.53S.54S.57S.58S.61S.62S.63S.76S.88S.92S.93S.96S.97S.98S.99

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