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Vaillant ecoTEC and Smart Thermostats: eBUS, OpenTherm and What Works
Vaillant boilers talk to their own controls over eBUS, a Vaillant protocol. A smart thermostat that does not speak eBUS can still switch an ecoTEC on and off. It cannot ask the boiler to modulate. Here is what each thermostat maker actually documents for Vaillant boilers.
Sumcraft Editorial Team7 min read
Checked on 20 October 2026. Updated 24 October 2026 with more answers to common questions. Everything below comes from the thermostat makers' and Vaillant's own documentation, linked at the end. We have not installed these thermostats ourselves. Have a qualified heating engineer wire any thermostat to your boiler.
Three ways a thermostat talks to a boiler
| Connection | What it does | Who documents it for Vaillant |
|---|---|---|
| On/off | Switches the boiler on and off. The boiler runs at the flow temperature set on the boiler | Any thermostat with a switching relay |
| OpenTherm | The thermostat tells the boiler what water temperature to run at, so the boiler can turn its flame down | Google, for Nest. Not Vaillant's own controls |
| eBUS | Vaillant's own protocol. The boiler and control share load and temperature data | Vaillant, for its controls. tado, for its wired Smart Thermostat |
Vaillant's vSMART technical sheet says the control "uses Vaillant's proprietary eBUS protocol to communicate with the boiler". Vaillant also says "eBUS connection allows the boiler to modulate". Modulating means running at lower output for longer instead of cycling on and off.
What each maker documents for Vaillant boilers
| Thermostat | What the maker documents | What to expect on an ecoTEC |
|---|---|---|
| Vaillant vSMART | eBUS connection; boiler modulates | Full modulation, by design |
| Vaillant sensoCOMFORT | eBUS connection; boiler modulates; outdoor sensor for weather compensation | Full modulation and weather compensation |
| tado Smart Thermostat (wired) | Installer manual lists Vaillant eBus settings: D07 (standard) and D05 (with a calorMATIC VRC430/470 and VR81) | eBUS control on supported set-ups. Hot water control only with D07 |
| tado on a system boiler | tado says it "is not compatible" with system boilers that have a digital interface such as eBUS | Ask tado before you buy |
| tado X | tado says tado X works with boilers that have a relay or OpenTherm connection. It does not mention eBUS | On/off. Ask tado before you buy |
| Google Nest Learning (3rd gen) and Nest Thermostat E | OpenTherm. Google does not mention Vaillant or eBUS and says to ask your boiler maker | On/off, unless an OpenTherm interface is fitted |
| Hive | Hive says its controls work with Vaillant boilers. Its compatibility page does not mention OpenTherm or eBUS | On/off. Ask Hive about its OpenTherm models |
We have left out Drayton Wiser and Netatmo. We could not find manufacturer documentation on how they work with Vaillant eBUS. Ask each maker for written confirmation for your boiler model.
What about an OpenTherm adapter?
Vaillant makes an OpenTherm module called the VR33. Dutch retailers list it as part 8000020151. They describe it as a way to connect OpenTherm thermostats to Vaillant boilers such as the ecoTEC pure and ecoFIT pro. It also replaces an older eBus-OpenTherm interface.
We could not find the VR33 in Vaillant UK's documentation. One retailer review says it cannot control hot water. Ask a Vaillant-trained installer whether it suits your boiler before you buy one, and ask Vaillant how it affects your warranty.
What you give up with on/off control
Google explains that OpenTherm lets a thermostat tell the boiler "when to adjust their heating water temperature". Vaillant says eBUS lets its boilers modulate "for optimal efficiency and peak performance". On/off control gives up that adjustment. The boiler fires at its set temperature until the thermostat switches it off. Neither maker publishes a savings figure we can quote, so treat any percentage you see in adverts with care.
Quick answers
- Does my Vaillant boiler have eBUS? Vaillant says its own controls, such as vSMART and sensoCOMFORT, use eBUS to talk to the boiler. If one of those is fitted, your boiler uses eBUS. For other set-ups, check your boiler's manual or ask Vaillant.
- Can I use a Hive thermostat with a Vaillant boiler? Yes, according to Hive. Its compatibility page says Hive works with Vaillant boilers. It does not mention eBUS or OpenTherm, so expect on/off switching.
- Is tado compatible with Vaillant? tado lists Vaillant among compatible boiler brands. It says tado works with almost all boilers that support relay connections. Its installer manual also has a Vaillant eBus setting for the wired Smart Thermostat.
- Does tado X work with Vaillant eBUS? tado says tado X works with boilers that have a relay or OpenTherm connection. It does not mention eBUS, so ask tado before you buy.
- Why is my Vaillant boiler not communicating with the thermostat? First check which connection you have. An on/off thermostat does not exchange data with the boiler. It only switches it. If you have tado on eBUS, tado's installer manual lists two Vaillant settings: D07 as standard and D05 with a calorMATIC VRC430/470 and VR81. Ask your installer to check the setting matches your set-up. If you fitted tado X expecting eBUS, tado does not document eBUS for tado X.
- Do I need a plumber to install tado? tado says you can install its devices yourself. It also sells installation by a certified engineer, listed at £140 including VAT on its UK shop. Wiring at the boiler involves mains voltage, so we recommend a qualified heating engineer.
Before you buy: a five-point check
- Find your boiler model. It is on the data badge, usually behind the front flap. Note whether it is a combi, system or regular boiler.
- Look for an existing Vaillant control. A vSMART, sensoCOMFORT or calorMATIC already uses eBUS. Replacing it with a non-eBUS thermostat means losing modulation.
- Check your system type. tado treats system boilers differently from combis. A cylinder or wiring centre adds complexity.
- Get written confirmation. Send your boiler model and system type to the thermostat maker. Keep the reply.
- Use a qualified heating engineer. Wiring changes inside or near the boiler are not a DIY job.
Sources, checked 20 October 2026. tado shop checked 24 October 2026:
- Vaillant: vSMART technical sheet
- Vaillant: sensoCOMFORT product page
- tado: Smart Thermostat installer manual, Vaillant eBus configuration (ManualsLib)
- tado support: is tado compatible with my system boiler? (7 October 2025)
- Google Nest Help: OpenTherm and Nest thermostats
- Hive: boiler compatibility (updated 14 May 2026)
- tado: is tado compatible with my boiler? (4 August 2026)
- tado: compatibility page
- Retailer listing: Vaillant VR33 OpenTherm module 8000020151 (Dutch)
- tado shop (UK): Wireless Smart Thermostat X starter kit, installation options
- Smart thermostat
- Vaillant
- Boilers
- Home heating
- eBUS