COMMERCIAL HEATING
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Guiding towards high-quality HIUs
Pete Mills, commercial technical operations manager for Bosch Commercial & Industrial discusses why the recent MEHNA installation guide on HIUs was developed
Left: Pete Mills, commercial technical operations manager for Bosch Commercial & Industrial
H
eat Interface Units (HIUs) play a vital part in the overall performance of heat networks, acting as the main aspect that end users
interact with. If one isn’t installed correctly or doesn’t match the latest regulations, it can inhibit a heat network’s efficiency, disrupt residents and - crucially- put people off the technology for future projects. Given this country’s lofty net-zero targets, the need for successful heat network projects is essential for decarbonising heat in all building types. Anything that can delay heat network adoption needs to be resolved. This is why DESNZ approached MEHNA asking
for a handy guide for installers fitting HIUs, giving step-by-step instructions, best practice and other educational information. With support from across the industry the ‘Installation, Commissioning and Maintenance of Heat Interface Units for the Heat Network Technical Assurance Scheme’ (HNTAS) guide was born. Overall, we see lots of problems happening in the field, fuelled by poor installations. The guide represents a lot of work that is going on to develop the British Standard for HIUs and to start aligning installers with the HNTAS’s practices and processes that are on the horizon. The Scheme will ensure heat networks are built correctly at the outset - and so the guide aims to ensure installers, commissioners and service engineers are prepared. But what can they expect to learn from the guide?
HIU help
The guide aims to be used as a reference for those in the field, as well as aid continued learning. To effectively do so, it covers the full lifecycle of an HIU installation.
14 June 2026
This includes an overview of the types of heat networks, how they function, where HIUs fit within that system and crucially, how they are supplied with energy for heating. Then it moves to best practice on how to install a HIU. All the information in the guide aligns to key national standards in relation to heat networks. From pressure relief valves and safety
discharge vessels, to heat meters and pre-payment connections, every part of the installation process is included. Meaning a seamless guide for any installer to fit HIUs to the highest quality. For commissioners, the guide also provides
step-by-step guides on how to undertake the multiple tests needed in the process. They can learn about the necessary water treatment checks, pipe installation and bypasses - nothing is left uncovered. For those maintaining HIUs, the guide gives a list
of all the checks needed to ensure the appliance is working efficiently. There is also a whole section for fault finding, meaning if there is an issue - say with the DHW or the temperature sensors - this can be easily spotted and resolved.
A guide for the future
The guide has been developed to paint the picture of what is needed to install, commission and maintain a HIU properly. By covering the typical stages and the potential faults that may occur whilst introducing installers to the types of testing that will come under HNTAS, we are hopeful that we’ll see an increase in correctly installed HIUs and more satisfied end users. But this is just the start. As regulations change or new innovative technology is introduced, the guide will be amended. To fully work as a resource,
it needs to hold the latest information so those who are working with HIUs keep informed. This is also translating into hands-on training.
For example, Bosch together with LCL Awards are launching a new certificated training course, so installers can learn how to use the guide in an educational setting - before putting it to use out in the field. All of this - alongside HNTAS, BESA and other
regulations - will contribute to higher quality HIUs in large residential and commercial projects, and therefore should see an uptick in HIU adoption too. We have lofty targets to hit when it comes to heating our homes in a low-carbon way. Heat networks will play a big part in achieving these goals, so anything we as an industry can do to support HIU growth is essential. This guide is just one small part of that. To view the ‘Installation, Commissioning and Maintenance of Heat Interface Units for the Heat Network Technical Assurance Scheme’ guide, visit:
https://www.mehna.org.uk/ media/7bcb8ad74dfaa5bcd396401f1a9f0d09/ MEHNA-Installation-Commissioning-and- Maintenance-of-Heat-Interface-Units-FINAL.pdf
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