Low
S.30 on Vaillant ecoFIT Pure 435

Your boiler is working perfectly, but it is currently being told to stay off by your room thermostat or smart home control system.

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

Room thermostat is blocking heating mode.

From this model's manual
Verified against the Vaillant/Vaillant Ecofit Pure 412 435 Open Vent 0020230535 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 room thermostat or smart heating app to ensure the target temperature is set higher than the current room temperature.Replace the batteries in your room thermostat if they are low.Check that your heating schedule is set to 'On' and not currently in an 'Off' or 'Away' period.

Find a Gas Safe engineer
Search the official register →
Boiler cover options

Avoid the next call-out bill

Monthly cover means no unexpected bills when your boiler breaks down.

Approved partner
Domestic Appliance Guard
Unlimited call-outs, 24/7 helpline, no price-hike promise
Get a quote →

Affiliate links. We may earn a commission at no extra cost to you.

Related fault codes

S.31View →S.32View →

All 71 fault codes on the ecoFIT Pure 435

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

conF.00F.01F.10F.11F.13F.22F.23F.24F.25F.27F.28F.29F.32F.49F.61F.62F.63F.64F.65F.67F.68F.70F.71F.72F.73F.74F.75F.76F.77F.83F.84F.85F.87F.88F.89F.97S.0S.01S.02S.03S.04S.05S.06S.07S.08S.20S.21S.22S.23S.24S.25S.26S.27S.28S.31S.32S.34S.39S.42S.46S.53S.54S.88S.91S.96S.98S.99S.108S.109

Related guides you might find useful

Thermostat not working

Change the batteries first, even if the screen still works.

Read →

Boiler won't turn on: 9-step checklist

Work through these before the call-out.

Read →

Is boiler cover worth it?

Break-even maths on monthly cover.

Read →