How does an air source heat pump work?

Air source heat pumps (ASHP) are becoming a more popular way of households heating their home and hot water.

It is a semi-renewable alternative to traditional heating systems. Which could help you lower your energy bills and carbon footprint whilst also giving you a step up onto the sustainability ladder.  

Although the initial expense of installing an air source heat pump may be off putting the benefits can far outweigh this whilst also looking after our planet for generations to come.

How does an air source heat pump work?

An Air to Water ASHP technically works like a refrigerator in reverse.

An external unit is placed outside your home. Normally in the back garden against a wall. It is connected to a small internal unit.

The system requires an evaporator, a compressor and a condenser. 

Your external unit draws air in from outside to heat a liquid refrigerant. The heat is absorbed as a fluid which is then turned into a gas. Using electricity the pump compresses the gas to increase its temperature even further. Once the desired temperature has been reached it is then transferred to the heating and hot water circuits within your home. It is then distributed via your wet central heating system. 

There is also another model called air-to-air, however this is not as popular within the UK and will not provide you with hot water and only space heat. Your home would require a warm air circulation system to move the heat around. This model is also not part of the Government’s Renewable Heat Incentive scheme.  

How does it work in winter? 

It is easy to imagine that your air source heat pump will not be able to provide you with adequate heating and hot water in the middle of winter. When the temperatures can drop to well below freezing.

Heat pumps are designed to be able to warm your homes with temperatures as low as minus fifteen degrees Celsius, but they do require more electricity to be able to do this.

Technically your system will be more efficient in the summer but the temperatures your system can produce will not be affected during the colder months of the year. 

Will a heat pump work with my existing radiators? 

Heat pumps are designed to produce a lower temperature over a longer period of time. Therefore they have a lower flow temperature.

For this reason an ASHP will work more efficiently with underfloor heating.

However, this isn’t always a feasible option for homeowners and radiators are the next best choice.

Radiators need to be sized for the flow temperatures. The standard sizes that are used with a traditional gas boiler are normally too small as gas heating has a much higher flow temperature. As the flow temperature decreases the heat emitting surface needs to be larger. So you may need to install larger radiators to get the most from your air source heat pump

It is also worth noting that a well insulated home is vital for your heat pump to work efficiently. Due to its lower emitting temperatures you will quickly notice the heat escaping from a poorly insulated home. 

Will switching to an air source heat pump lower my energy bills?

By switching to a more renewable source of energy you will see a reduction in your energy bills. However, the amount you will save depends on several factors. Including which type of heating system you are switching from.

Other factors that come into play are – 

  • The size of your home
  • The ambient temperature
  • How well insulated your home is

Although your ASHP will require electricity to work it is generally far more efficient. The efficiency is measured using the Coefficient of Performance (COP) and measures the input versus the output. A system with a COP of 3 will require one kwh of electricity to produce 3 kwh of heat. The higher the COP rating the more efficient your system is. 

What is the Renewable Heat Incentive scheme? 

The Renewable Heat Incentive scheme is part of the Government’s promise to reach net zero emissions by 2050 and is designed to help offset the initial installation and running costs.

Households that take part in the scheme will receive quarterly payments for seven years for every kilowatt hour of renewable heat that they produce. 

What are the main benefits of an air source heat pump?

  • Lower energy bills. 
  • You may be able to earn a passive income through the Renewable Heat Incentive scheme. 
  • Lowering your carbon emissions. 
  • Some models can also be used for cooling during the Summer months. 
  • Installation is easier than a ground source air pump. You will require adequate space around your external unit to ensure an uninterrupted flow of air. 
  • Low maintenance – Regular servicing is advised but the general day to day maintenance is very little. You should ensure that the air inlet grill is kept free from leaves and other debris and remove any plants or weeds that start to grow around the unit. 
  • Long life span – Providing your ASHP is looked after and regularly serviced it has a long life span of between 20-25 years. 

Although the initial expense of installing an air source heat pump may be off putting the benefits can far outweigh this whilst also looking after our planet for generations to come. 

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