The 2050 Net Zero Target is driving the energy transition from gas to electricity, supported by the increasing use of heat pumps.
Removing natural gas from heating systems will have the desired effect of reducing overall greenhouse gas emissions, especially if low and lower GWP systems are then used to replace them.
That is why we are pushing a focus on heat pumps and offering advice on some of the considerations that are important when selecting the correct heat pump, for the correct application.
Heat pumps are widely acknowledged as a pivotal solution to future commercial heating and cooling challenges. However, choosing the right system often involves more than just selecting a product and installing it.
There is a lot to consider for what will still be a fairly new technology for some, even though heat pumps have been in use for decades, which is why we have highlighted the six key areas that can impact on the type and specification of heat pump required for each individual application.
These are: Flow temperatures; hot water and heating requirements; air flow; plant space; noise; and power availability.
We see it as our mission to help you keep up to speed on the latest legislative developments
Graham Temple Marketing Manager for Mitsubishi Electric
Flow Temperature
The most crucial consideration for any project is the flow temperature, which establishes the link between the Air Source Heat Pump and indoor equipment like fan coils, radiators, or hot water storage, amongst others. By flow temperatures, we are referring to the temperature of the water that is being supplied at (typically between 35-70°C), along with the difference in temperatures that the water is being returned at, commonly referred to as ‘Delta T’.
Being able to lower the supply water temperature that your system works at, for example reducing it from 65°C to 55°C, increases the number of options available to design your heating system. Air Source Heat Pumps will list their maximum leaving water temperature (typically at 7°C ambient), but nearly all will work at lower temperatures.
Thus, understanding the limitations of your design, particularly the requirements of your indoor equipment, is important in order to not compromise system performance. Once you recognise these requirements related to flow temperature, you will have a solid foundation for design that will clearly define what kind of products are available to you.
Hot Water & Heating Requirements
Heat pumps, like boilers, can provide both heating and hot water to a building. Each application demands a unique balance between the two and there are several technologies available to achieve this.
When it comes to hot water, the key considerations are: how much you are able to store, how quickly it could be used and what time will be available to recharge the thermal store.
Single stage heating from air source heat pumps to hot water is possible, however if they are being used for space heating, then it is important to understand group controls and logic to ensure any competing demand can both be satisfied.
Another scenario could be to consider a cascade heating system, where the air source heat pumps provide heating to a Low Temperature Hot Water (LTHW) circuit, that is suitable for space heating, and water source heat pumps then use that LTHW circuit as the source for the hot water circuit.
Air Flow
Whilst it can be easily overlooked, an Air Source Heat Pump (ASHP) is exactly that: the heat provided is sourced from the ambient air.
Heat Pumps can work to very low negative temperatures, such as -20°C, and air source heat pumps are popular in many regions that have a colder climate than the UK - such as in Nordic countries. However, failure to take care of the heat pump's airflow, for both the air drawn in by, and rejected by the fans, can lead to lower performance, increased maintenance and in the worst-case damage to the equipment.
When positioning an ASHP, take measures to prevent air recirculation - where the air that has been through the ASHP is reused, but at a lower temperature giving a less efficient performance and increasing the chance of the heat pump freezing.
Using structural fabrications such as a raised platforms or designing the height of walls or shelters to match the height of the ASHP helps to promote air to move away from the ASHP and dissipate into the ambient air.
Plant Space
In an ideal world, there would always be more than enough space to install a heat pump. However, the reality is that every site is unique, and plant space must be considered early in the design process.
The choice of heat pump technology in any project is influenced by the available area within your estate to ensure safe and effective operation. This involves ‘technology-specific’ factors dictated by the products and ‘project-specific’ factors imposed by the site.
When specifying a heat pump for a project, three key technology-specific factors must be considered: footprint, service area, and clearance (or exclusion zones).
Typically, footprint refers to the physical dimensions of the equipment, whereas service area is the space required on each side of a unit, which can be different, to ensure that an engineer can access and maintain the equipment throughout its life.
Clearance areas are related to operating or safety requirements, whether that is to ensure airflow, or to comply with safety standards when using certain refrigerants.
When dealing with plant space constraints, redundancy of the heating system may also be required, which can put additional pressure on plant space. Mitsubishi Electric can offer a range of heat pump solutions and designs to assist, some of which have “modular” capabilities.
These are typically smaller capacity (up to 750kW), compact heat pumps, which may allow you to utilise unusually shaped plant space or build a system with a physical separation. Modular heat pumps often share service areas between units, reducing the overall footprint required.
What does this mean for your projects? Designing within space constraints requires careful consideration, and each project should be reviewed on a case-by-case basis. Our engineers will collaborate with you and your team to ensure the right product is applied to your project.
Our award-winning Ecodan CAHV-R is a perfect example of a modular heat pump, making it suitable for a wide range of commercial applications, from office blocks, schools, universities and even heat networks. Find out more about the Ecodan CAHV-R Commercial Air Source Heat Pump.
Noise
With environmental noise pollution under intense scrutiny, particularly in modern cities, noise is a crucial consideration in the implementation of air source heat pumps (ASHPs).
Reducing the noise impact of an ASHP often requires installing larger equipment operating at lower capacities, or fabricating an acoustic enclosure around the heat pump. However, these solutions can conflict with the need to work within restricted plant space.
Fortunately, there are many alternatives to reduce noise emissions. Some ASHP models come with factory-installed options such as acoustic enclosures for compressors, anti-vibration mounts, or upgrades to EC fans to allow for variable speed control. Additionally, control functions like ‘night mode’ allow the unit’s operating limit to be reduced during times when noise tolerance is lower.
Mitsubishi Electric also offers Super Low Noise versions (-SL) on many heat pumps, specifically designed to minimise noise as much as possible. For example, the Climaveneta i-FX-N features a Low Noise configuration, while maintaining the same compact design footprint as its standard counterpart. No matter your noise constraints, we can help you find the right solution.
Power Availability
The UK is gradually transitioning its heating energy from the gas network to the electric grid, a process known as the “electrification” of heating. This energy transition poses challenges with generation, but more importantly with the network infrastructure, especially at the local or distributed level. This is a significant issue for residential estates or smaller commercial environments where the existing infrastructure may not support increased localised demand.
The Energy Networks Association (ENA) is collaborating with heat pump manufacturers to identify the technical information needed to evaluate the suitability of existing electrical infrastructure and determine where upgrades are necessary to support this transition.
For designers, two key questions need to be answered regarding the electrical infrastructure of an estate: Is the substation shared with other users? Is that substation a high voltage or low voltage resource? If the estate has a chiller system that could be replaced with a reversible heat pump or a simultaneous heating and cooling system, the impact on the electricity network will be less significant than replacing a gas boiler.
If available power supply is limited, a bivalent heating system, where a heat pump and boiler work together to provide heating, could be considered. While not providing a total electrical solution, a bivalent system is still a positive step towards decarbonisation.
Ongoing support
Designers and specifiers face a constantly changing legislative environment, so we see it as our mission to help you keep up to speed on the latest developments in the regulations affecting HVAC equipment and the buildings they are used in.
At Mitsubishi Electric, we have developed one of the most comprehensive ranges of free, CPD-Accredited guides which are all available in our document library.
One of the latest looks at BS EN 378 and offers advice on how to manage risk in HVAC systems using modern refrigerants, which many may not have used before.
The new, low-GWP generation of refrigerants offers many benefits, but it is vital to be aware of the regulations and standards around their use.
Graham Temple is a Marketing Manager for Mitsubishi Electric
