The UK’s first test standard for Heat Interface Units (HIUs), which is managed by the Building Engineering Services Association (BESA), has been revised and updated in response to growing demand from the district heating industry.

Two UK-based test houses have now been approved to carry out testing to the standard – BSRIA and Enertek International – in addition to the Research Institutes of Sweden (RISE), which was previously the only organisation able to test to the new UK standard.

HIUs extract heat from district heating networks to feed individual buildings and dwellings. How they perform is central to the overall efficiency of a district scheme. The Standard was developed, therefore, to help developers of UK heat networks procure HIUs based on comparative performance data.

The availability of a UK standard has prompted considerable response from manufacturers with a significant number of HIUs already tested at RISE with several more already going through the process at BSRIA and Enertek.

Testing to the standard is a two-stage process: The HIU has to achieve a UKAS or equivalent national accreditation through one of the three test houses and this result must then be verified by the Standard’s Steering Group before being published on the BESA website.

The BESA Standard originally emerged from a heat network efficiency research project supported by the Department for Business, Energy & Industrial Strategy. Testing to the Standard is helping to create a comprehensive product database and improve performance of UK heat networks.

It is modelled on a well-established Swedish methodology, which was adapted to suit typical UK operating conditions, and makes it possible to compare products and equipment types so that network designers can evaluate the performance of individual HIUs against their design parameters.

The test calculates the annual volume weighted return temperature (VWART) from the HIU and provides evidence of compliance with other performance and reliability metrics, such as domestic hot water response time.

As part of the revision process, the steering group overseeing the Standard has been expanded and a technical sub-committee – comprising industry experts and the three test houses – has been set up.  It will make recommendations to the steering group on developing the standard, including a planned expansion of the regime.  An HIU Manufacturers’ forum has already had its first meeting at BESA’s headquarters in London and provided valuable feedback to the steering group.

“One of the Standard’s great strengths is that it has been developed by users, for users,” said UK HIU Steering Group chair, Gareth Jones. “It provides users with a clear basis on which to evaluate HIU performance and is rapidly becoming the default point of reference for those making procurement decisions within the industry.

“As a result, HIU manufacturers must now ensure that their HIUs perform well and we are seeing a significant increase in R&D. Ultimately this raising of standards will help improve the health of the heat network industry as a whole.”


More information is available here.


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BDC 311 : Dec 2023