Koen Braham is a software consultant at Alten.

28 April 2022

BDR Thermea is working together with partners like Alten in building a new cloud-based IoT platform for its portfolio of room thermostats and other comfort appliances. Key aspects are user interaction via apps, device security and migration.

BDR Thermea Group is a leading manufacturer of comfort appliances. The company researches and develops boiler systems that use natural gas or hydrogen, but it also invests in comfort devices such as heat pumps and air conditioners. These appliances are marketed worldwide under local brands such as Baxi, De Dietrich and Remeha. Alten collaborates with BDR Thermea on projects like a room thermostat, appliance control interfaces, embedded control algorithms and service apps by providing knowledge and continuous development.

Making comfort appliances connected opens the door to features that use services in the cloud. It creates more support possibilities for installers and field engineers and brings extra functions for reducing energy consumption. To achieve these objectives, BDR Thermea is working together with partners like Alten in building a new cloud-based IoT platform. Key aspects are user interaction via apps, device security and migration.

Since BDR Thermea introduced connected appliances back in 2016, they’ve built up an enormous portfolio, with hundreds of thousands of devices currently online. In an ever more digital world, this platform keeps expanding and it starts to show more and more growing pains, putting larger stresses on the components used. Every milestone of N thousand connected devices calls for caution on how far the boundaries can be pushed.

Remeha Etwist kitchen
Credit: BDR Thermea


An important requirement for a new online platform, with no compromises, is that all current customers can make the switch with their installed hardware. Not having to replace devices prematurely guarantees a longer life for devices and thus reduces e-waste. This is a challenging proposition as it requires a secure method to transfer a device to the new platform without manual intervention by installers. Customers should be unaware of the migration until they start using the new ecosystem app.

Microsoft’s Azure IoT Hub is an ideal candidate for BDR Thermea’s new online platform. The hub and supporting platform have proven their value in the market by delivering a modern and secure framework, while the Azure Sphere reference module demonstrates best practices for the implementation of IoT devices. Equally important is that most of the infrastructure is delivered as a service and ties closely into other Azure products already in use by BDR Thermea.

The novelty for BDR Thermea is that they’ll use IoT Hub for telemetry services as well as user interaction. This pushes the requirements for connectivity as customers expect fast responses. They’ll use the new app to adjust their indoor temperature and switch between scheduling or continuous comfort. Any user change applied in the app should be visible within seconds on the room thermostat.

This is a big contrast to telemetry, where information is collected and delivered to analytics platforms. Fast is great, but a delay of a couple of minutes isn’t business critical. For telemetry, it’s more important to have complete datasets and cost-effective transfers by queueing streaming data to bursts. This saves on data costs as the payload is effectively compressed and it reduces battery consumption on mobile devices as communication is intermittent.

Digital twin

An important part of the migration is hooking up Azure IoT Hub to the existing portfolio of devices. The software development kit (SDK) provided by Microsoft is very instrumental here. It gives handles to send and receive messages to the cloud. As all communication with the SDK is asynchronous, it’s possible to connect these inputs and outputs to the ecosystem running on the room thermostats.

For rich communication, the thermostat builds an abstract view of the connected system. This digital twin holds an online representation of the local device for use with Azure-based functions. The abstraction groups information by heating zones or, in a more practical sense, rooms of a home. Homes with multiroom comfort systems are controlled by a single app. Using this system, the Azure cloud is informed of current room setpoints and active schedules. This information is securely linked to a customer account for use in their app.

The digital twin follows changes on the device to update the app. Costs are reduced by using telemetry for updates with messages containing JSON payload and CBOR compression. JSON is an unstructured format that has shown itself to be a big help in agile development as the receiver doesn’t need to know the format upfront. This enables rapid prototyping as the cloud and the device have messaging flexibility.

Remeha Calenta Etwist
Credit: BDR Thermea


For BDR Thermea’s room thermostats to remain trusted devices, security is an important aspect of the transition to Azure IoT Hub. This is the linking pin between the old and the new platform for online connectivity. Accounts and user information will follow the migration as devices move based on their identification. For implementation, the IoT Hub SDK uses standardized certificate authentication and enables custom integration on this interface. Using the Azure Device Provisioning Service (DPS) on the devices, the old security is tied to the new platform.

After starting the new Azure-based software, devices reach out to the DPS to authenticate and redirect to dedicated IoT Hub instances in the cloud. A large benefit of using the service in this stage is load distribution for new connections. The DPS will learn about the available IoT Hub instances and can guide devices to them. This allows for sustainable growth over time for many devices to come.

As devices become Azure based, they should switch to current best security practices as recommended by Microsoft. These best practices aim to improve the encryption strength while reducing the required power to compute the encryption. All devices connecting to Azure will rev up their security with elliptic-curve cryptography, after which the security keys are monitored and renewed whenever they reach their due date. BDR Thermea is familiar with this process as it matches the strategy of the old platform.

Lessons learned

For BDR Thermea, the room thermostat is the first device to fully embrace Azure. Because it runs embedded Linux, it’s less restricted than other embedded systems. The IoT Hub C SDK is integrated as a separate process, with the communication to internal processes following the device architecture. Using these building blocks, a first proof of concept was up and running within one month.

In communicating, sending fewer but richer messages saves money and increases reliability. IoT Hub calculates costs based on the number of transferred messages, with a maximum message size of 4 KB. Lowering the frequency of communication significantly reduces the costs when deploying large quantities of devices. As only changes are relayed, it creates new possibilities for rich data exchanges using a digital twin in the cloud. An added benefit to this strategy is that smaller messages are sent over Wi-Fi, which reduces interference and improves reliability.

Given the challenge to support a growing online offering, IoT Hub has shown to be a good fit. The integration into the current portfolio enables all devices to migrate to the new ecosystem. The online load distribution results in a more balanced platform for sustainable growth. Extending the lifecycle of devices supports the goal of reducing carbon emissions.

Edited by Nieke Roos