The OpenTherm Association – a year on

The OpenTherm Association – a year on

12 months into its initial programme of awareness raising in the UK, the OpenTherm Association has taken its first successful steps into the UK marketplace. As it begins its second year of activity, the association is looking back over the first 12 months and sharing its plans for the second, assuming that the interruption of Covid-19 allows it to continue with its plans across the remainder of 2020. Already the virus has affected the opportunity to meet installers at exhibitions up and down the country that have been postponed or cancelled due to the lockdown issues across the UK.

OpenTherm is a non-manufacturer-dependent system of communication currently utilised predominantly between modulating HVAC heating appliances and room thermostats. It consists of a communication protocol and an interface specification. OpenTherm utilises an established technology combining simple installation procedure with high functionality and future expansion possibilities. OpenTherm has been available in the UK for around ten years and in mainland Europe for a little longer, but has only been promoted more widely over the past year or so.

The OpenTherm Association has introduced the OpenTherm protocol more widely in the UK and has launched an initial three-year communication process to raise awareness of the protocol, its benefits to the heating industry as a whole and to manufacturers and installers in particular. The OpenTherm protocol facilitates digital boiler modulation and as a result, load compensation requirements are met. The growth in the use of the OpenTherm protocol across the UK offers huge innovation potential. Looking ahead, a large installed base of OpenTherm compatible products could facilitate the implementation of a range of new solutions that could improve energy use, reduce the carbon footprint of a heating installation and reduce its total cost of ownership. Typical potential examples could see the increase in home automation and the availability of remote diagnostics for domestic installations.

The OpenTherm Association recognises that, in order to establish the OpenTherm protocol, it needs to effectively communicate and illustrate ‘what’s in it for me’ benefits to those manufacturing the equipment and those installing it in homes up and down the country.

“Over the past year we have seen wider communication via the trade media and social media stepped up,” says OpenTherm Director Frank Steggink. “We also mounted our first workshops for installers… It’s been a gradual process of introduction and we intend to broaden the message and share more information in the coming months.”

The OpenTherm Association already has a number of members signed up to work with it to introduce a wider acceptance of OpenTherm as a standard in the UK – manufacturers of boilers and controls that have already evaluated the OpenTherm protocol’s compatibility with their systems include well-known names in the sector such as Ideal Boilers, InterGas, Honeywell Resideo, Danfoss, SALUS, ESi and Schneider Electric. Many other familiar names in the UK sector – major companies in Europe with an influence in the UK marketplace – may well combine to see the acceptance of the OpenTherm protocol, speeding up acceptance in the UK marketplace. Recognising the common sense in developing a common use ‘Open’ system here in the UK, the protocol importantly, also has the support of industry bodies HHIC and BEAMA who continue to be committed to supporting OpenTherm’s wider introduction here.

The basic function that every OpenTherm controller must provide is the communication of the heat requirement – the control setpoint and modulation level – to the heating appliance. This heat requirement is calculated by the controller based on the difference between the set temperature and the desired one, or another form of control such as outside temperature control. The OpenTherm protocol also supports many other non-compulsory functions offering – even encouraging the manufacturer the opportunity to develop multiple product variants.

For manufacturers of heating boilers, heat pumps, controlling devices and associated products, who are interested in developing and producing OpenTherm compatible products, they can approach the OpenTherm Association secretariat to obtain a data sheet, free of charge, simply by completing the request form on the new OpenTherm website at

The OpenTherm Association is working on the introduction of an automated test tool that should be available for all member companies within the next few weeks, which will help address some of the incompatibility issues that some installers have experienced in trying to pair controls with boilers in the past few months: “This is a major plus for OpenTherm and will certainly smooth over some of the teething problems that have been experienced by some installers,” says the new chairman of OpenTherm’s Technical Committee, Huite Jan Hak, who has been responsible for the production of the test tool. “Whilst we accept that there have been some issues, it’s very easy to blame the OpenTherm protocol for these issues when it transpires that there have been reliability issues with the equipment being installed in some cases we have investigated so far. The arrival of the test tool should address many of these problems and highlight exactly where some of the challenges really lie. For the remainder of the issues we shall reach out to our members to help them improve their OpenTherm implementation where needed.”

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