Is My Boiler OpenTherm? How to Check, Brand by Brand

Your boiler is OpenTherm if it carries the OpenTherm logo or its maker lists your model as compatible. The brand alone does not tell you.

Checked on 31 October 2026. Everything below comes from boiler and thermostat makers' own documents, linked at the end. We have not tested these boilers ourselves. Have a qualified heating engineer make any connection inside the boiler.

How to check your own boiler

1. Find the model name. It is on the data badge, usually behind the boiler's front flap. Your installation paperwork shows it too.
2. Look for the OpenTherm logo on the boiler. Google says a missing logo does not mean the boiler is incompatible.
3. Check the manual's controls section for terminals marked OpenTherm or OT. Google's Heat Link guide names OpenTherm wires OT1 and OT2.
4. Ask the maker about your exact model. Google and Viessmann both give this advice.
5. Check the thermostat as well. Google says OpenTherm Nest thermostats carry the logo on the box.

Brand by brand

Ideal

Ideal says its Logic boilers have OpenTherm wiring connections. It calls the link "a standard 2-wire low voltage and polarity-free connection". The spec sheets for the current Logic Combi2 and Logic Max Combi2 list "other OpenTherm controls" as compatible. Our Ideal Logic guide covers Nest, Hive and tado on these boilers.

Baxi

Baxi's 2024 range guide calls these boilers "Fully compatible with OpenTherm":

• Baxi 400 Combi 2.1
• Baxi 600 Combi 2 and 600 System 2
• Baxi 800 Combi 2 and 800 System 2

The same guide does not mention OpenTherm for the 400, 600 and 800 Heat boilers. Baxi also sells its own OpenTherm thermostat. For an older Baxi, ask Baxi with your model name.

Worcester Bosch

Worcester Bosch's official account said in September 2020 that it does not use OpenTherm on any of its boilers. Its own controls talk to the boiler over a connection called EMS. Our Worcester guide lists which controls work with which Greenstar models.

Vaillant

Vaillant's own controls use eBUS, a Vaillant protocol. Vaillant makes the VR33 module to connect "an OpenTherm third-party control" to "a Vaillant eBUS heat generator". It fits inside the boiler's electronics box. Our Vaillant guide has the installation steps from Vaillant's manual.

Viessmann and older boilers

Viessmann says a boiler "will require a pre-installed OpenTherm interface". It adds that "most older boilers, therefore, won't work with OpenTherm". Google says many older boilers that lack OpenTherm "have simple on or off controls".

Is my combi boiler OpenTherm?

Being a combi does not decide it. The model does. Baxi lists both combi and system boilers as OpenTherm compatible. Worcester says none of its boilers use it, combis included. Check your model with the steps above.

If your boiler is not OpenTherm

A smart thermostat can still switch it on and off. The boiler then runs at its own set temperature until the thermostat turns it off. Some makers have their own way to let the boiler turn down its flame:

Which thermostats speak OpenTherm?

• Google Nest: Google says the Nest Thermostat E and the 3rd gen Nest Learning Thermostat support OpenTherm.
• tado: tado says tado X works with boilers that have a relay or OpenTherm connection.
• Hive: Hive sells V4 OpenTherm thermostats, listed by UK retailers.
• Ideal: Ideal's Halo Lite is a wired OpenTherm thermostat.
• Baxi: Baxi sells a single-channel OpenTherm thermostat.

Ask the thermostat maker about your boiler model before you buy. A logo on both boxes is the simplest sign they will work together.

Quick answers

How do I know if my boiler is OpenTherm?

• Look for the OpenTherm logo on the boiler and check its manual for OpenTherm terminals. If you are unsure, ask the maker about your exact model.

Which UK boilers have OpenTherm?

• Ideal says its Logic boilers do. Baxi says its 400 Combi 2.1, 600 and 800 Combi 2 and System 2 boilers do. Worcester Bosch says none of its boilers do.

Do Worcester boilers support OpenTherm?

• No. Worcester Bosch said in 2020 that it does not use OpenTherm on any of its boilers. Its own controls use EMS.

Is my Baxi boiler OpenTherm?

• Yes for current models. Baxi's 2024 range guide calls its Combi 2 and System 2 boilers fully compatible. That includes the 400 Combi 2.1 and the 600 and 800 models. Ask Baxi about older models.

Is my Vaillant boiler OpenTherm?

• Not natively. Vaillant boilers use eBUS. Vaillant's VR33 module lets an OpenTherm thermostat connect.

Is my Ideal boiler OpenTherm?

• Ideal says its Logic boilers have OpenTherm wiring connections. Its current Logic Combi2 and Logic Max Combi2 spec sheets list OpenTherm controls.

Is it worth using OpenTherm?

• Google says OpenTherm lets a thermostat tell the boiler when to adjust its water temperature. Ideal says this limits overshoot. Neither publishes a savings figure we can quote.

Sources, checked 31 October 2026:

• Google Nest Help: OpenTherm and Nest thermostats
• Google Nest Help: Nest Thermostat E Heat Link wiring
• Ideal: the benefits of OpenTherm connectivity
• Ideal: Logic Combi2 spec sheet
• Ideal: Logic Max Combi2 spec sheet
• Ideal: Logic2 controls guide
• Baxi: range guide 2024
• Baxi: heating controls and accessories
• Worcester Bosch on X: "we do not use open therm on any of our range of boilers" (14 September 2020)
• Vaillant: VR 33 installation instructions, document 8000020416_01 (ManualsLib)
• Viessmann: understanding OpenTherm systems (16 June 2022)
• tado: is tado compatible with my boiler? (4 August 2026)
• Screwfix: Hive V4 Wireless Heating OpenTherm Smart Thermostat