What is An Air Source Heat Pump? 2023 Guide

Find out what an air source heat pump is, how to install one, and its benefits and drawbacks.

Your home can be efficiently heated and cooled with an air-source heat pump. An air-source heat pump can provide a home with up to three times as much heat as it uses in electrical energy when it is installed correctly. This is possible because, unlike combustion heating systems, a heat pump transfers heat rather than converting it from fuel.

What exactly is an air source heat pump, and would it be a good fit for your building? In this article, we’ll explain the fundamental operation and dispel a few myths.

What is An Air Source Heat Pump?

An air source heat pump (commonly referred to as a mini-split or multi-split system) is a complete heating and cooling system that doesn’t depend on fossil fuel combustion. Air-source heat pumps are the industry standard in many Asian and European nations. They have few drawbacks and provide excellent efficiency, precise temperature control, and greater seasonal comfort.

In essence, the technology—which is also found in air conditioners and refrigerators—uses ambient air from outside the building as a heat source or a heat sink. Basic heat pump system components include:

• Outdoor Condenser and Evaporator Unit – An exchange of heat occurs when the ambient air is gathered by a fan and moved over a coil.
• Indoor Air Handler Unit – Another coil is present in the indoor unit. After passing over the coil, the air is blown into the room by a fan (or through the ductwork of the building).
• Compressors – A compressor, similar to those found in conventional air conditioners, is present in a heat pump. This compressor pressurizes the refrigerant to enable it to flow throughout the system. For the duration of the pump’s life, the system recycles the refrigerant.
• Reversing and Expansion Valves – The reversing valve alters the refrigerant’s flow, enabling the pump to deliver both cooling and heating. The refrigerant’s pressure and temperature are reduced by an expansion valve, which also controls its flow to maintain the desired temperature.

The reversing valve determines whether the ASHP is heating or cooling the building, so these components all work in essentially the same ways whether the pump delivers cold or hot air.

How Does An Air Source Heat Pump Work?

Using a compressor, an air source heat pump extracts heat from the air and raises its temperature. It then transmits the heat to your home’s heating system. They operate somewhat like refrigerators that run backward.

1. The air source heat pump converts heat from the ambient air into low-temperature liquid refrigerant.
2. The liquid is compressed by the pump to raise its temperature using electricity. To release the heat it had been holding, it then condenses back into a liquid.
3. You can have underfloor heating or radiators. The remainder can be kept in your hot water cylinder.
4. For baths, showers, and faucet use, you can use the hot water that has been stored.

The electricity required to power the pump should be less than the heat it generates. As a result, they are an effective way to heat your house. Even in extremely low temperatures, air source heat pumps function.

Types of Air-Source Heat Pumps

Despite using similar technology, air source pumps come in a variety of configurations to suit the requirements of various building types. Often ductless air source systems are used in new installations. Installers can join the ductwork to the outdoor condenser if a building already has a ventilation system in place.

Although the efficiency of heat transfer is reduced when air is forced through the ductwork, ducted heat pump systems are still significantly more effective than combustion systems. Common heat pump options include:

• Mini-Split Heat Pumps – The indoor and outdoor units of a mini-split system are separate. Building managers can work around this restriction by installing separate mini-split systems for each room, which would allow them to operate at different temperatures in each zone covered by the mini-split system.
• Multi-Split Heat Pumps – Different temperatures can be set for different rooms using multi-split systems. One or more outdoor units are connected to numerous indoor units. However, the system can only control one type of temperature at once; it is either heating or cooling.
• Variable Refrigerant Flow (VRF) Heat Pumps – VRF systems, like multi-split systems, have an outdoor unit and numerous evaporators. They can provide heating or cooling to each indoor unit while they are operating by adjusting the refrigerant flow.

Mini-split or multi-split systems are used in the majority of residential, commercial, and mixed-use buildings. Larger commercial and residential buildings can benefit greatly from VRF systems, and when installed properly, VRF technology can offer a wide range of advantages to both building owners and tenants.

Advantages of Air-Source Heat Pumps

Utilizing heat pumps has a number of advantages. Compared to a gas or electric heating system, an air-source heat pump can help you save money on energy costs and lower your carbon footprint. One of the key advantages of air-source heat pumps is their versatility and affordability. An ASHP can work for either heating or cooling purposes and can be used for space heating or water heating.

The most important advantages of purchasing an air-source heat pump are the following:

Low Carbon Footprint

In order to heat or cool your home, air source heat pumps use outside air, which is a low-carbon heating method. Your carbon emissions can be greatly reduced if you switch from a heating system that runs on coal or electricity. A much better option for reducing emissions is an air source heat pump, which uses only 1 unit of electricity for every 3 to 4 units of energy produced.

Save Money on Energy Bills

By switching to air-source heat pumps, you can reduce your energy bills as you’ll be using the outside air for your heating and cooling needs. If you are switching from an electric or coal-based system, your savings will be greater.

Eligible for Boiler Upgrade Scheme

You could receive £5,000 towards the upfront costs of an air source heat pump through the Boiler Upgrade Program. Applicants will be given a voucher that they must use within three months. This means that the heat pump must be installed within this time frame. The government started this £3.9 billion project in April 2022 as a part of the Heat and Buildings Strategy. The program will last through April 2025.

The program seeks to promote the use of low-carbon heating systems in homes in England and Wales. The costs of biomass boilers, air-source heat pumps, and ground-source heat pumps—all of which are more environmentally friendly than natural gas boilers—are specifically covered by grants.

Can Be Used for Heating and Cooling

Air source heat pumps can be used for both heating and cooling purposes. They can provide heating in the winter and cool in the summer, depending on the model. The only thing you need to make sure of is that your air source heat pump’s cooling capacity factor (COP) should be greater than 0.7.

In addition, air-source heat pumps work very well with underfloor heating — so if you want to get the most out of your system, you should strongly consider installing underfloor heating.

Can Be Used for Space Heating and Hot Water

Depending on the air source heat pump, you can also use it to heat your water. This is based on the flow temperature or the temperature of the water in the heating system. The temperature of the flow must be around 55°C in order to heat water. If your system is only intended for space heating, the flow temperature will be 35°.

Choose an ASHP with a flow temperature of 55°C if you need both space heating and water heating.

High Seasonal Coefficient of Performance (SCOP)

Air source heat pumps are efficient both in the winter and summer, thanks to an outstanding SCOP (seasonal coefficient of performance). By comparing the power input required to produce heat to the amount of heat output, the COP of a heat pump is a way to assess its efficiency. A “seasonal COP” figure is changed to account for seasonality.

For instance, a typical air source heat pump operates at a COP of 3.2 when the outside temperature is higher than 7°C. For each kWh of electricity used by the fans and compressor, 3.2 kWh of heat is produced, making the heat pump a 320% efficient device. The better, the higher the COP.

Therefore, when considering an air source heat pump’s COP vs outside temperature, then you will find that despite some slight fluctuations, they can run efficiently year-round. The seasonal COP is used to compare heat pumps based on how much these efficiency changes impact them.

Easy Installation Process

Installing an air source heat pump can take as little as two days. Because you don’t need to dig, installing an air-source heat pump is simpler than installing a ground-source heat pump. Most of the time, planning permissions are not needed for a domestic air source heat pump, but it is always a good idea to check with the local authority before you start your project.

Both new construction and retrofits should consider this option. The price of installation can be reduced if you install your air source heat pump concurrently with other construction work.

Low Maintenance

Servicing and maintenance should be done by a technician once a year. As a result, air-source heat pumps require little maintenance. However, there are a few things you can do to ensure your heat pump operates at its best, such as cleaning the filters, checking for system leaks, determining the amount of refrigerant in the system, removing leaves and dust from the heat pump, and so on. Only an installer who is certified should perform any additional technical tasks.

Long Lifespan

Air source heat pumps have a long lifespan, and with proper maintenance, they can be operational for up to 20 years. What’s more, is that most air source heat pumps have 5-year warranties. Thanks to a number of technological advancements, modern heat pumps can now operate effectively for almost 25 years before they need to be replaced.

No Fuel Storage Needed

No fuel storage is needed with air source heat pumps because the fuel used is the outside air. For example, oil-fired boilers require storage space on your property because you need to keep the oil somewhere. Not relying on fuel, such as oil or wood pellets, also means you won’t have to pay additional fees for fuel deliveries.

Disadvantages of Air Source Heat Pumps

An important disadvantage to be aware of is that air-source heat pumps have a lower heat supply than other alternatives. This means to get the most out of your ASHP, you need to have a well-insulated home and, ideally, underfloor heating, too. Air source heat pumps can also be noisy, which is another frequent issue.

Thus, where you place them can have a significant impact. These are the main air source heat pumps disadvantages:

Lower Heat Supply Than Boilers

This type of heating has a lower heat supply compared to oil and gas boilers, so larger radiators might be needed. When radiators are connected to boilers, the water may circulate at a temperature higher than when they are connected to an ASHP system. Therefore, a larger heat-emitting surface is required to provide the same amount of space heating.

Extra Spending to Install Underfloor Heating

Air source heat pumps are most frequently used in conjunction with underfloor heating to maximize the system’s efficiency because of the lower heat supply. This is due to the fact that you won’t need as high of temperatures to operate this; you won’t want to stand on a floor that is 40 degrees Celsius.

This can mean that your installation costs may be higher if you do not already have an underfloor heating system installed.

Your Home Must Be Well-Insulated Already

In order to reap the full benefits of an air-source heat pump, you will need a well-insulated home, to begin with. This applies to all heating systems, though. You will require more energy to maintain a home’s temperature if heat can easily escape through walls, windows, or doors. Make sure your home is sufficiently insulated as a result.

Lower Efficiency below 0°C

Although air source heat pumps can work at temperatures as low as -20°C, they do lose efficiency below 0°C. This is due to the fact that they solely rely on outdoor air, and as the temperature drops, so does the maximum amount of heat the pump can produce.

On the other hand, ground source heat pumps are less impacted by cold climates, have pipes buried deep in the ground, and have a more constant temperature.

Lower Savings Compared to Low Price Mains Gas

If you have access to cheap mains gas, then the difference between the gas price and the electricity price (for powering an air source heat pump) won’t be significant. Still, many people still consider heat pumps to be a significant investment. However, the UK is planning to significantly increase the number of heat pump installations, so you can anticipate more low-carbon incentives to make the switch.

ASHPs Can Be Noisy

Air source heat pumps can be somewhat noisy when they are running, comparable to a regular air conditioner or light to heavy rain. To improve this and lessen their noise, however, businesses are constantly developing new technologies.

How to Select a Heat Pump?

Every residential heat pump sold in this country has an EnergyGuide label, which compares the heat pump’s heating and cooling efficiency performance rating to that of other makes and models.

The heating season performance factor (HSPF), which is a measurement over an average heating season of the total heat provided to the conditioned space, expressed in Btu, divided by the total electrical energy consumed by the heat pump system, expressed in watt-hours, provides an indication of the heating efficiency for air-source electric heat pumps.

The seasonal energy efficiency ratio (SEER), which measures cooling efficiency over an average cooling season, is calculated as the sum of all heat removed from the conditioned space, expressed in Btu, divided by the sum of all electrical energy consumed by the heat pump, expressed in watt-hours.

The cost of the unit typically increases with the HSPF and SEER. But over the course of the heat pump’s life, the energy savings can more than pay for the higher initial investment. The cost of heating and cooling will be significantly reduced when a new central heat pump replaces an old one because it will use a lot less energy.

These are some other factors to consider when choosing and installing air-source heat pumps:

• Make your choice of a heat pump with a demand-defrost control. Defrost cycles will be minimized as a result, which will cut down on the energy used by supplementary and heat pumps.
• The fan and compressor noise is annoying. Choose a heat pump with a lower outdoor sound rating (decibels), and position the outdoor unit away from windows and nearby structures. By mounting the device on a base that absorbs sound, you can also lessen this noise.
• The outdoor unit’s efficiency may be impacted by where it is placed. High winds should be kept at a minimum to avoid problems with defrosting outdoor units. To shield the coils from strong winds, you can carefully place a bush or a fence upwind of them.

How Much Does An Air Source Heat Pump Cost?

The price of an air source heat pump varies depending on the size of the heat pump, the size of the building, whether it is a newly constructed building or an existing building, and whether you need to modify the way heat is distributed throughout your building.

The typical price range is between £7,000 and £13,000, and to get the best idea of what your home will likely cost, we advise speaking with at least three installers to get a quote for your heat pump system.

Conclusion: a Complete Guide to Air Source Heat Pumps

Since air is a renewable, natural source of heat, an air source heat pump system can aid in reducing your carbon footprint. It depends on the fuel you are replacing and how much CO2 you will save. If you are replacing a coal or oil boiler instead of a natural gas boiler, the number, for instance, will be higher.

Air source systems must benefit from current technologies for maximum efficiency. When choosing systems, metrics like the heating seasonal performance factor (HSPF) and seasonal energy efficiency ratio (SEER) can offer helpful information. Increased efficiency may be achieved through expert right-sizing and installation. Up to 40% of energy bill savings are reported by our clients.

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