Understanding Heat Pump Systems: Components Explained

Heat pumps seem to be in the news more and more, with the Government announcing several initiatives to encourage us to install them. They’re described as super efficient and environmentally friendly heating systems. Why is that and how do they actually work? This article dives into the various parts of a heat pump system, along with key considerations for design and operation. Let's get started!

Heat pumps are efficient and good for the planet

Your current boiler burns gas, makes fire and this heats up water. The hot water goes through your pipes and radiators and the heat transfers to all the rooms in your house. 

With heat pumps, there’s no combustion - we’re not burning fuel (e.g. gas) to create fire.  Ambient heat in the air in your garden is collected up, absorbed by some super-cold refrigerant, compressed (raising its temperature further) and then transferred into the water in those pipes and radiators. Sounds like magic? It’s literally the exact same technology that your fridge/freezer uses. 

It’s also a very energy efficient process, with the heat pump using about 1 unit of electricity to generate 3-4 units of heat (a very efficient boiler needs 1 unit of gas to create about 0.8 units of heat). So a heat pump uses less energy than a boiler. And because most of the UK’s electricity already comes from low carbon sources (with the grid set to be fully renewable in the years ahead) the energy it does use has far, far less carbon intensity. 

Boiler and heat pump central heating systems are different

You can heat your home in two ways. Carefully calibrate the size of radiators, pipework and heating source to deliver a flow of warm water and consistent temperature in the home. Or send super hot water round the system, ignoring the size of pipes and radiators, heating it up very, very hot, then let it cool down and repeat the process. 

When installing a heating system, the former is more expensive, takes longer and requires more skill. Heat pump technology can only actually work in this way. Boilers can be set up to work either way, but because the second approach is cheap, easy and requires less skill, installers almost invariably do it that way. And that’s why they turn off and on all day, your radiators are burning hot to touch, the temperature in your home fluctuates wildly and they burn a lot of gas. 

We could characterise the two systems like this: heat pumps are like taking a journey in a Tesla, riding at a smooth, constant 50mph; boilers are more like riding a massive, supercharged diesel tractor at 90mph, but stopping and starting every 20 metres down the road. 

Expert design and installation is essential

Aside from providing a different comfort experience, the technical distinction above highlights the critical importance of getting a skilled, experienced installer for a heat pump system. Well-designed and correctly installed systems guarantee comfort and improve efficiency and lifespan. Working with a qualified heating engineer experienced in heat pumps makes all the difference.

The design phase considers factors like your home's size, insulation levels, and climate to ensure the chosen system perfectly meets your needs. Proper installation guarantees all components connect correctly, allowing the system to operate optimally for reliable comfort.

Furthermore, a well-designed and installed heat pump system contributes to energy savings and a reduced environmental impact. By tailoring the system to your home, you avoid unnecessary energy consumption and lower your carbon footprint. This not only benefits your budget but also contributes to the global effort of reducing greenhouse gas emissions.

Regular maintenance and servicing are also essential for smooth operation and maintaining equipment warranties, and keeping the unit working up to a 12-15 year life. A qualified engineer can keep your system running efficiently, minimising energy bills and preventing minor issues from escalating into costly repairs.

The key components of a heat pump system

So what are the components of a carefully calibrated heat pump system?

1. Heat Pump Unit

The most expensive and crucial component, the heat pump uses electricity to extract heat from the air or ground, similar to a refrigerator. Here are the two most common types:

• Air-source heat pumps: These systems transfer heat between your home's interior and the outside air. They're the most common type, best suited for temperate climates like the UK. Typically located outdoors on rubber blocks to minimise noise and vibration (modern units are exceptionally quiet, no louder than the average boiler or fridge).
• Ground-source heat pumps (geothermal): These systems use pipes buried underground to transfer heat between the earth and your home. They are more suited to very cold environments and have higher upfront costs.

2. Hot Water Cylinder

This stores hot water for domestic use. It's extremely well-insulated and sized based on your home's needs. Striking a balance is key; too big, and you waste energy heating unused water. Too small, and you might need to top up with less efficient methods like immersion heaters. While similar to those used in gas-heated systems (“system boilers”), heat pump cylinders are optimised for heat pump use. Traditionally, they reside in airing cupboards where residual heat from pipework can help dry linens. If you have a combi boiler, you won’t currently have this in your home and will need to find a space for it. 

3. Radiators

These heat your home using the hot water generated by the heat pump. Commonly wall-mounted, they distribute heat through two mechanisms: direct radiation and convection. Larger radiators have a greater surface area, allowing the water inside them to be heated to a lower temperature to create the same heat output in the room (more efficient, less energy use by the heat pump). This is why radiators are often upgraded when installing a heat pump system. Underfloor heating, when available, is an even more efficient option, essentially turning your entire floor into a large radiator for gentle heat distribution.

4. Expansion Vessels

These spherical vessels, roughly the size of a football, maintain constant pressure within the system as the water expands and contracts. They're usually tucked away for easy access during servicing.

5. Control Units

Thermostats and electrical control units, increasingly wireless and featuring smart features like interaction with your smart meter and electricity provider for optimised energy use.

6. Consumer Unit (Fuse Box)

This critical safety element manages your home's electricity supply, ensuring appliances don't draw excessive power and create hazards. It should be easily accessible for safety reasons, often located in a dedicated cupboard.

There you have it! This whistle-stop tour of a heat pump system equips you with the basics. But of course, there's always more to learn – that's why we have a team of experts on hand to answer any further questions you may have.

FORNAX can help you make your home greener and more energy-efficient today.