What is an Air-Source Heat Pump? A Complete Guide In 2024

What is an Air-Source Heat Pump?

You may know that there exist differing heat pump types. They are classed in line with their functioning and the source of heat absorption. The most renowned and prevalent heat pumps are air-source heat pumps (ASHPs).

These electrical devices take in heat from the external air. They then transfer the heat indoors to provide heating and hot water to your residence.

ASHPs can further deliver cooling. They do this by reversing this heat transfer process from one location to another. It implies they take in heat from the inside air and reject it outside.

Many modern (but not all) ASHPs can deliver cooling to your household. They eliminate heat from the indoor air to render the inside air cooler.

Essential Heat Pump System Components

An ASHP (sometimes called an air-to-water heat pump) comprises several principal components. These elements function together to give effectual heating and cooling. These are as follows:

1. Outdoor condenser and evaporator unit

Depending on the system type, ASHPs can have outdoor and indoor units. The outdoor unit’s primary function is capturing the heat in the air. It comprises the heat exchanger and the compressor. These play a fundamental role in the absorption and compression of ambient heat. By ambient heat, we mean the heat present in layers of air near the ground.

This implies that outdoor heat is brought into a heat exchanger, the so-called evaporator. It allows heat transfer between the outside air and the refrigerant.

There’s a second heat exchanger called a condenser. The condenser can also be found in the outside unit if you have a monobloc heat pump. The condenser aims to transport heat from a refrigerant to a water loop. It then delivers space heating and hot water.

The condenser is in the device’s indoor unit if you possess a split system. Continue reading to find out more about split and monobloc heat pumps.

2. Indoor unit

Inside your household, the indoor unit distributes the heat or cold that the system makes. Typically, it can be the following:

• Radiators
• Underfloor heating
• Ducted air distribution system

3. Refrigerant pipeline

The refrigerant pipeline is an insulated set of copper tubes. It aims to transport refrigerant between the heat pump’s outdoor and indoor units.

It plays an all-important role in the heat transfer process throughout the system.

4. Reversing valve

Reversing valve is also a critical component of ASHPs. It reverses the direction of the refrigerant flow to provide cooling in summer.

In other words, it permits the heat pump to vary between heating and cooling modes. In many ASHPs, you’ll find a 4-way reversing valve.

5. Expansion valve

The expansion valve regulates the refrigerant flow for smooth heat pump operation. It also contributes to maintaining the performance and efficiency of ASHPs.

How Does Air-Source Heat Pump Heating Work?

As you can see, heat moves from warmer to colder places naturally. To provide heating, ASHPs reverse this process using electricity. It does this via a refrigeration cycle, thus employing a refrigerant. It’s a medium through which heat travels from one stage to another throughout the system.

Heat energy from the external air is captured into the evaporator. It then transfers onto the refrigerant even when it’s colder outside. Even when the outside temperatures are low, it still contains adequate heat to extract from the air.

The compressor then compresses the refrigerant. As a result, the temperature of the refrigerant shifts up.

The compressed, high-temperature refrigerant alters to a gas and proceeds to the condenser. Here, heat from the gaseous refrigerant transfers to water.

The gas refrigerant cools as the heat is released in the condenser and the expansion valve. It then alters back to a liquid. This process repeats itself to deliver heating and hot water eventually.

How Does Air-Source Heat Pump Cooling Work?

Besides heating, ASHPs can also provide cooling generally via a 4-way reversing valve.

It alters the refrigerant flow direction. That allows the system to take in heat from the indoor space. It then rejects it outside. It eventually cools the water that circulates the system. It can then be utilized for space cooling.

When the reversing valve activates for cooling mode, the “condenser” acts as an evaporator. It absorbs heat from the connected water cycle, leading to evaporation of the refrigerant. In the “evaporator,” the refrigerant condenses and rejects heat to the outside.

Types of Air-Source Heat Pumps

ASHPs come in several types, which are as follows:

1. Air-to-air heat pumps

Air-to-air heat pumps are essentially categorized as a variant of air conditioners. They can both cool and heat your residential space. But they lack the provision of hot water. Air-to-air heat pumps are the most prevalent in differing countries and regions, such as the USA. They also include many European countries like France, Portugal, Spain and Italy.

2. Air-to-water heat pumps

There’s another air-source heat pump type that is available. i.e., air-to-water heat pumps. They absorb heat from the outside air (even when it’s cold) and transport it to water. The heat then distributes to differing emitters like:

• Radiators
• Underfloor heating
• Hot water tank
• Fan coil units

The purpose is to provide heating, hot water, and optional cooling functions. Such heat pump systems are more prevalent across Europe, including Poland, Germany, Finland, Norway, etc.

Essentially, there are two types of air-to-water heat pumps. These are:

Monobloc Heat Pump

This variant of air-to-water heat pump comprises a single heat pump unit. It’s located outside of your household. It comprises of a single outdoor unit containing the following:

• heat exchanger
• compressor
• the water section of the refrigeration cycle

Monobloc systems are cheaper than their split counterparts and quicker to install. They occupy less space in your household.

Split Heat Pump

A split heat pump is dissimilar to a monobloc heat pump.

A split system separates the components between outdoor and indoor units. Furthermore, two copper tubes transfer refrigerant between indoor and outdoor units.

Benefits of Using Air-Source Heat Pumps

Air-source heating and cooling provides some noteworthy benefits that are as follows:

1. All-in-One Package

ASHPs (particularly air-to-water heat pumps) are an all-in-one package. This means they can meet a household’s heating, hot water, and cooling requirements.

It’s also a markedly long-term solution for managing your living space’s temperature needs. That’s why they are preferred for residential and commercial use.

2. Eco-friendliness

ASHPs only need electricity to transport heat. They don’t require fuels like oil, gas, and wood. That means heat pumps emit much less CO2 than gas boilers. That can substantially help to reduce greenhouse gas emissions. That makes heat pumps sustainable and environmentally friendly.

According to the European Heat Pump Association, heat pumps can reduce more than 9 million tons of CO2 emissions in the European Union only. Furthermore, they can lessen CO2 emissions by 35-65% compared to gas boilers.

3. Future-Proof

By using an ASHP heat pump, you can free yourself from gas or oil deliveries. It can also save you from future increments in fuel prices. There’s no need to fear restriction and future bans on fuels. That makes such an HVAC system future-proof.

4. High energy-efficiency

In essence, ASHPs can provide 3-4 kilowatts of renewable heat from the air. It’s for every kilowatt of electricity used. They operate with a ratio of 30% electricity and 70% renewable sources, i.e. air. That makes them around 300-400% energy-efficient.

That’s a substantial improvement compared to conventional heating systems like gas boilers. Heat pumps also require less electricity than electric heaters, which helps lower energy bills.

5. Low maintenance

Heat pump technology is time-tested and reliable. Thus, ASHPs require low maintenance. There are only a few components to inspect. Furthermore, its costs are relatively low. In contrast, boilers typically need regular cleaning and require more maintenance costs.