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Industry insight
Modularity built into HIU design B
As different heating technologies battle it out for supremacy, HVAC consultant Martin Lowe discusses the benefits of a newly-designed modular heat interface unit (HIU)
ased on my experience in the heating and ventilating industry over the last 30 years, there is only one thing I can be certain about over the next few years, and that is there is nothing I can be certain about. The UK government has given the deadline of 2025 as the last year that gas boilers will be legal for installation in new projects. Considering this, manufacturers within the heating industry are seriously looking at different technologies to replace the traditional gas boiler as the primary method of heating water for commercial and domestic applications.
There are several existing contenders such as biofueled boilers, heat pumps, electrical and combined heat and power being considered. But revolutionary new technologies such as hydrogen and microwave boilers are also being considered. As with any deviation from the well-trodden path into the unknown, the potential capability of all of these technologies both new and established to step in as a suitable replacement for the traditional gas boiler whilst meeting our heat generation needs, is not yet fully understood. In fact, this may take many years even beyond the 2025 deadline before one of the technologies emerges as a firm favourite.
However, in order establish which technology will become the ‘preferred standard heating method of the future’, these alternative technologies will have to have been tried and tested in the crucible of the real-world over a significant time frame. It is crucial each technology is judged honestly and critically in the categories of price, safety, efficiency and maintainability. It should go without saying that although this process of technological natural selection is vitally necessary, it will leave many less than optimum systems installed in many locations.
Therefore, during this period it would be undoubtably beneficial to build in simple and innate interchangeability and maintainability into heating systems moving forward. Especially if that system provides heating and hot water to apartments on a central water distribution supply.
The current range of HIUs on the market are based around standard fixed design principles adapted from traditional gas boiler white boxes, they are not manufactured for either change or flexibility. It’s safe to say conventual HIUs are optimised for a particular application or system. There is no long-term flexibility or redundancy designed into them, to effectively future proof them against a requirement to work with varied heat sources. Be it direct or indirect heating, various sized water supply temperatures or design Delta Ts.
The schematic shows the standard design built to be modular – combining three modules to make a complete HIU
At the time of writing this article, I am not aware of a unit designed to be easily adapted to a change in these requirements.
For example, let’s imagine a situation where a residential apartment building decides to change its heating source from a 70°C traditional boiler system to a 55°C heat pump system. The existing HIU with its heat exchangers sized to the suit the initial design parameters of the traditional system, simply will not be able to accommodate the drop in supply temperature and maintain end user performance. As such the HIU will have to be removed and replaced along with the rest of the heating system. However, what if we took the time to develop a modular HIU system that had the capability to be easily retrofitted with different components to the requirements of a new heat source? Then we would reduce, if not eliminate, a large portion of the expense of switching a system from a less than optimal heat source to the preferred standard of that time. Then by extension, it also stands to reason that if the system can be retrofitted once why not a second or third time, if regulation or technology demanded so? This would save on cost in terms of material and money. An additional benefit is the bleed over
into the sphere of maintenance of a blocked or poor performing heat exchanger, as maintaining good flow through the heat exchanger is crucial to ensuring the efficiency of any HIU.
I think at this point we can agree that moving forward there are many advantages to adopting a modular philosophy for HIU design and for the last 12 months I and my colleague, Anthony Copson, have been working on developing a HIU that has been reimagined from the ground up.
Only by looking at the application, the various equipment to control flow, meeting the design criteria and the current recommended requirement of current guidance can progress be made. It is essential to ensure performance and efficiency not just at the start of the project but throughout the service and maintenance of the equipment used. This would be with the understanding that the future is uncertain and the system might be upgraded or adapted and you would be safe in the knowledge that the HIU has been designed not for automatic replacement but for whatever energy source prevails after 2025. Of course, no one can predict the future but at least building in some modularity with this simple compact solution gives some flexibility to a design.
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