BoilerFaultCodesVaillant S.30 Fault Code
Also written as S30 — same fault.
The Vaillant S.30 fault code means: your boiler is working correctly but is currently in standby because your thermostat or programmer is not asking it to provide any heat.. It appears on 46 Vaillant models in our database.
Technical description: No heating demand from external controls (clamp 3-4 open)
What causes the Vaillant S.30 fault?
This status occurs when the boiler is waiting for a signal from your thermostat to tell it to turn on. It physically means the electrical circuit between your heating controls and the boiler is open, indicating that your home has already reached the desired temperature. The most common reasons are simply that the thermostat is turned down, the timer is set to 'off', or the thermostat batteries have run out.
This is more frequently queried in autumn when homeowners first turn their heating on and find the boiler doesn't respond because of a programmed schedule or depleted thermostat batteries.
DIY fix possible
Check if your room thermostat is turned up higher than the current room temperature.Ensure your heating programmer or timer is set to 'ON' or 'AUTO'.Replace the batteries in your wireless room thermostat if the screen is blank or showing a low battery symbol.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
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A cover plan would handle faults like S.30: no call-out fees, no surprise bills.
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Vaillant models that show the S.30 fault code
Click a model for the full fault code list and model-specific repair notes.
- Atmomax Repair: £0-120
- ecoFIT Pure 412
- ecoFIT Pure 418
- ecoFIT Pure 425
- ecoFIT Pure 435
- ecoFIT Pure 825
- ecoFIT Pure 830
- ecoFIT Pure 835
- ecoMAX
- ecoMAX 613 Repair: £0-120
- ecoMAX 618 Repair: £0-120
- ecoMAX 622 Repair: £0-120
- ecoMAX 635 Repair: £0-120
- ecoMAX 824E Repair: £0-120
- ecoMAX 828E Repair: £0-120
- Ecomax Condensing 600/800 series
- ecoMAX System 612 Repair: £0-120
- ecoTEC Repair: £0-120
- ecoTEC 65kW
- ecoTEC exclusive Repair: £0-120
- ecoTEC Plus 610
- ecoTEC Plus 615 Repair: £0-120
- ecoTEC Plus 620 Repair: £0-120
- ecoTEC Plus 625 Repair: £0-120
- ecoTEC Plus 630 Repair: £0-120
- ecoTEC Plus 635 Repair: £0-120
- ecoTEC Plus 826
- ecoTEC Plus 840 Repair: £0-120
- ecoTEC Plus 938 Repair: £0-120
- ecoTEC plus aquaPLUS Repair: £0-120
- ecoTEC Pro Repair: £0-120
- ecoTEC Pro / ecoTEC Plus Repair: £0-60
- ecoTEC Pro 24 Repair: £0-120
- ecoTEC Pro 28 Repair: £0-120
- ecoTEC Pro 30
- ecoTEC sustain Repair: £0-120
- Home Combi
- Home System Repair: £0-120
- Thermocompact
- Turbomax 824/828
- Turbomax Plus
- Turbomax Plus 824/828E
- Turbomax Plus 828 Repair: £0-120
- Turbomax Plus 828 E
- Turbomax Plus VUW 242E
- Turbomax Plus VUW 242EH
Source
Vaillant S.30 fault code information on this page is sourced and cross-checked against the official Vaillant service / installation manuals for each affected model.
- Vaillant ecoFIT Pure 412 manual (PDF)
- Vaillant ecoFIT Pure 835 manual (PDF)
- Vaillant ecoMAX manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026