Low
S.31 on Vaillant ecoTEC plus 630 H system A VU GB 306/5-5 A

Your boiler is simply in summer mode or not receiving a demand for heating from your thermostat.

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 active or no heat requirement from eBUS controller

From this model's manual
Verified against the Vaillant/Vaillant Ecotec Plus 832 Lpg Vuw Gb 326 5 5 4704459 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

Check your thermostat or programmer to ensure the heating is turned on and set above the current room temperature.Verify that the boiler's operating mode is set to winter mode (radiator symbol) rather than summer mode.Turn the boiler off at the mains, wait 30 seconds, and turn it back on to reset the system.

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Related fault codes

S.30View →S.33View →S.34View →

All 94 fault codes on the ecoTEC plus 630 H system A VU GB 306/5-5 A

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

F.00F.01F.02F.03F.10F.11F.12F.13F.20F.22F.23F.24F.25F.26F.27F.28F.29F.32F.42F.49F.52F.53F.54F.56F.57F.61F.62F.63F.64F.65F.67F.68F.70F.71F.72F.73F.74F.75F.77F.78F.80F.81F.83F.84F.85F.90F.91F.92F.93S.00S.01S.02S.03S.04S.05S.06S.07S.08S.10S.11S.13S.14S.15S.16S.17S.20S.21S.22S.23S.24S.25S.26S.27S.28S.30S.32S.34S.39S.40S.41S.42S.46S.53S.54S.57S.58S.61S.62S.63S.76S.96S.97S.98

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