How do heat pump systems work?
Instead of generating heat from scratch, heat pumps transfer heat from one place to another, using a small amount of electricity.
Here, we’ll answer all your questions about how heat pump systems work – from which emitters work with heat pumps, to how hot they can heat water.
How do heat pump systems work?
Air source heat pumps work by absorbing energy from the air and compressing it into high-grade heat, using a small amount of electricity.
They then deliver the heat through a heating distribution system such as radiators or underfloor heating in a way that feels similar to a traditional boiler.
In this way, they’re a reliable method for providing space heating and domestic hot water throughout the seasons – even when it doesn’t feel warm outside.
What emitters work best with air source heat pumps?
Your heat pump will work as a team with your heating system to deliver heat efficiently.
So, it’s super important that your heating system – including the emitters – is designed specifically for the heat pump selected.
But what emitters typically work best?
Underfloor heating
Underfloor heating often pairs well with heat pumps.
This is because heat pump systems tend to operate at lower flow temperatures than traditional boilers (although this doesn’t always have to be the case).
Meanwhile, underfloor heating also operates at low flow temperatures as it has a large surface area and so doesn’t need to operate at high temperatures to provide effective space heating.
With that in mind, underfloor heating and heat pumps are often a match made in heaven.
Radiators
Contrary to what you might think, radiators can also be effective when paired with a heat pump.
The only thing to be conscious of is the size of your radiators.
As we’ve already touched upon, many heat pumps operate at lower flow temperatures than traditional gas boilers.
So, if you’re switching your boiler for a heat pump, it’s often wise to upgrade to bigger radiators with a larger surface area. This way, they can heat a room just as effectively while operating at a lower temperature.
That said, it isn’t always necessary to switch to bigger radiators – it all depends on your building and what kind of heat pump you opt for. Which brings us onto…
Can I keep my radiators when I switch to a heat pump?
The simple answer is that it depends on lots of different factors, including:
- Your existing boiler
- Your existing radiators
- Your heat pump and refrigerant
Generally, if you choose to retrofit an R290 (propane) heat pump, you won’t need to make many changes to your existing infrastructure.
This is because R290 heat pumps tend to operate at a similar temperature differential (Delta T) to traditional gas boilers (Delta T means the difference between the flow and return temperatures).
However, you will still normally need to replace your radiators with bigger ones to achieve the same heat output.
Why?
Well, while most gas boilers are set up to operate at 80°C with a 60°C return temperature, R290 heat pumps normally operate at 60°C with a 40°C return temperature.
This means that a larger surface area is needed to provide the same level of space heating for a room.
But there are exceptions!
1. Oversized emitters
In the past, many radiators have been oversized.
If this applies to the radiators in your building, they may already be suitable for lower flow temperatures.
Establishing whether this is the case is your heat pump designer’s job. But there’s a simple test you can carry out yourself to get a good idea of whether you could keep your existing radiators.
Just turn your boiler down to 60°C on the flow temperature over winter. This way, you’ll be able to see in real time how your building would feel on a propane system with your existing emitters.
2. High temperature heat pumps
High temperature heat pumps are heat pumps that have been designed especially to operate at higher temperatures.
There are several ways to create a high temperature heat pump – for instance, your system designer might suggest creating a cascade heat pump system, or opting for a CO2 heat pump.
However, for buildings where making changes to your existing infrastructure simply isn’t possible, our new Elm R290 heat pump is ideal.
This high temperature heat pump is the UK’s first direct boiler replacement heat pump. It’s designed to provide 100% heat decarbonisation without requiring any changes to your building’s infrastructure – so, you can keep your existing radiators!
In this way, it puts heat pumps on the cards for all sorts of buildings where it would be difficult or even impossible to make changes to the existing infrastructure – such as listed buildings, healthcare facilities, residential care homes and multi-tenant properties.
Can I use a heat pump for domestic hot water?
Yes!
It’s a common misconception that heat pumps aren’t reliable at heating water above around 60°C.
But this simply isn’t true!
While many heat pumps haven’t been designed to heat water above this temperature, others are capable of heating water to significantly higher temperatures and have proved themselves as reliable providers of both space heating and hot water.
How do heat pumps produce hot water?
If you’re keen to use a heat pump for domestic hot water (DHW), you’ll have two main options:
- Install it as a standalone water heating system
- Install it as a combination water heating and space conditioning system
In other words, you can use a heat pump to provide just hot water. Or, to provide both hot water and space heating.
Either way, air source heat pumps work in much the same way for DHW as they do for space heating. They extract warmth from the air and convert it to a higher temperature using a compressor.
To heat water, the flow enters an indirect coil within a hot water cylinder, to increase the temperature of the water, which is then sent to taps and showers around the building.
How hot can heat pumps heat water?
While many standard heat pumps can only heat water to around 60°C, others are capable of heating water to significantly higher temperatures.
For instance, our groundbreaking Elm heat pump delivers flow temperatures up to 80°C.
Similarly, our CO2 heat pumps have proven repeatedly that they can consistently produce a hot water supply at 80°C – even with variable ambient conditions.
This is more than enough for most hot water requirements.
Can I combine a heat pump with a boiler?
If you want to, you can combine a heat pump with a boiler or another existing heating system.
This is known as bivalent heating.
Usually, a bivalent heating system is used when the heat pump isn’t sized for 100% of the peak heating load.
In this way, the boiler acts as a secondary heating system to supplement the heat pump when necessary.
That said, just because it’s possible to combine a boiler and a heat pump, that doesn’t mean it’s common – or necessary.
Normally, bivalent systems are only found in retrofit applications where the insulation levels of a building are insufficient and a heat pump can’t meet all of the heating load effectively.
But even then, a correctly sized heat pump should be more effective.
At Clade, we always aim to size heat pump systems to meet 100% of the heating demands.
In particular, our Elm high temperature heat pump can be a great option for buildings where insulation levels can’t easily be improved, as it provides a direct replacement for a boiler.
How can I maximise my heat pump’s efficiency?
Did you know that heat pumps are around three or four times more efficient than gas boilers?
It’s true! The most efficient boilers can reach around 98% efficiency, while air source heat pumps can reach a whopping 300% efficiency!
However, there are a few things that can help to maximise your heat pump’s efficiency.
Refrigerant choice
Your choice of refrigerant – also known as working fluid – can have a big impact on your heat pump’s efficiency.
Refrigerants are fluids that are compressed into liquids with very low boiling points. When they absorb heat, they boil and turn into gas. As they release this heat, they then condense back into fluids.
This process is known as the vapour compression cycle and is what allows heat pumps to heat buildings. However, not all refrigerants are equal.
When it comes to heat pumps, natural refrigerants tend to be particularly efficient. This is largely because these refrigerants have no glide – a thermodynamic behaviour found in some synthetic refrigerants, which suits cooling and refrigeration but not heating.
In fact, in heat pumps, natural refrigerants achieve higher coefficient of performance (COP) at low ambients and high flow temperatures than synthetic refrigerants.
At Clade, we only work with natural refrigerants as they’re both high-performing and environmentally friendly – making them the best option for both people and the planet.
System design, installation and commissioning
A heat pump system design must be finely tuned to take into account the unique needs of a building and its occupants.
That’s why our experienced system designers will create a bespoke system that takes into account your business’ exact requirements.
In this way, they can ensure your entire system is working with you to ensure the highest COPs possible – including the heating distribution system, which we’ll come to in a minute.
However, it doesn’t end there. After the installation phase, you’ll enter the commissioning phase, which is just as important.
During this phase, commissioning engineers spend time putting your new heating system through its paces and optimising the system performance.
No system is perfect at first. So, it’s vital that time is spent looking at the data and making adjustments to the system in order to achieve the best possible performance.
Heating distribution system
As we touched upon above, it’s really important that all the elements of your heating system are working together with your heat pump to deliver heat efficiently.
Heat pumps are different from gas boilers, and therefore need different distribution or heating systems to function at peak efficiency.
In particular, your heating distribution system must be designed specifically for the heat pump selected, as they need to be able to work as a team.
This includes elements such as the surface area of your emitters and flow control.
In order to marry all the elements together, your system designer will use a combination of VSD pumps, control valves and balancing valves to achieve optimal performance.
Can heat pumps cool as well as heat?
Yes, heat pumps can cool buildings as well as heat them.
Essentially, you just reverse the direction that the refrigerant goes around the system – and warm air is moved from inside to outside rather than vice versa.
However, not all heat pumps are capable of doing this. And even if they can, it’s not always a good idea.
Why?
Well, pumping cold refrigerant around your system on a hot day can lead to sweaty pipes and dripping radiators. Plus, cold air doesn’t rise like warm air does – so, if it’s hot, you’ll have to lie on the floor to benefit.
Not only this, but the cooling capacity of your heat pump probably won’t be powerful enough for your needs.
After all, your heating system is designed to warm your building in even the coldest weather. When your system designer carries out heat loss calculations, they’ll assume it’s cold and dark outside. And they won’t take into account other factors that can add warmth – such as people, pets and electrical appliances – as they’re just a bonus!
On the other hand, if you want your heat pump to provide cooling, you’d need to do a whole separate heat gain calculation that factors in all the unwanted heat coming into your building from the sun and all those other places.
Don’t get us wrong, cooling your building with a heat pump is doable. But it shouldn’t be an afterthought. Instead, it requires careful consideration, calculations and design – just sticking a standard heat pump in reverse won’t cut it!
How do I know if my building is suitable for an air source heat pump?
Lots of people wonder whether their building would be suitable for an air source heat pump. But guess what? Nearly all buildings are.
At Clade, we design and install heat pumps for all kinds of buildings and sectors – from swimming pools to schools, supermarkets to libraries and office blocks.
Our new Elm heat pump also puts heat pumps on the cards for thousands of buildings that wouldn’t previously have been able to retrofit a heat pump, such as listed buildings, healthcare facilities, residential care homes and multi-tenant properties.
So, the chances are your building is suitable for an air source heat pump. It’s just about selecting the right one, and teaming it with the right heating system for your needs. Which is what we’re here for!
Our team of expert engineers will be able to assess your premises and come up with a bespoke solution that ticks all your boxes. Which brings us onto…
Let’s talk about heat pump systems
At Clade, we have 35 years of experience manufacturing heat pumps and refrigeration equipment.
So, we know what we’re talking about when it comes to heat pump systems and how they work!
If you’re interested in finding out more about how a heat pump could benefit your business – or what exactly switching to a heat pump might look like – our dedicated team of experts are happy to help.
Just get in touch and ask away!