How Do Air Source Heat Pumps work?

How do air source heat pumps work? What is the SCOP of an ASHP? Find out, along with lots of other air source heat pump terminology.
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The Basics…

Simply put, a heat pump is a device that transfers thermal energy from one point to another. A common example of this can be found in our refrigerators where the evaporation and cooling of a liquid is used to lower the temperature of the storage compartment. Nowadays, this technology can also be used to extract the potential thermal energy in the air outside, or even from the ground, feeding it directly into your home where it is compressed and the heat transferred using a series of coils. It sounds like magic but the science behind it is relatively simple…

Although they use a small amount of electricity to run, heat pumps are considered highly efficient and clean because they don’t depend on the burning of fuel to create the heat. They perform well in moderate climates such as the UK and can provide heating during the winter, even at temperatures of -20 degrees Celsius. There are different two main kinds of heat pump depending on the type of medium they extract heat from, namely air or ground/water, and they are now beginning to be incorporated into modern builds on a regular basis.

How The Magic Happens

So we’ve learnt that air source heat pumps don’t generate heat for themselves, but extract it from the atmosphere/air, but how?

1. Outside air is drawn into the unit and passed over the evaporator fins with the fan.

2. Electrical energy is provided by the grid, or a renewable source such as solar PV or batteries – this is what powers the fan and compressor.

3. As the name suggest, the evaporator is where the refrigerant gas boils and evaporates (heated by the energy in the outside air.

4. The gas passes into the condenser where is passes it heat to the heating system flow. As it releases its energy, it cools, condenses, and returns back to a liquid.

5. The heating flow is heated by the hot, compressed refrigerant gases and is pumped around your heating system.

6. The liquid refrigerant passes through an expansion valve, reducing it’s pressure and temperature, and the whole cycle starts over.

This cycle is continuous, with refrigerant at all different stages of state (gas, liquid etc) at any given moment. It it this cycle that enables a heat pump to provide more energy than it consumes.


What Is The SCOP And Why Is It Important?

SCOP stands for Seasonal Coefficient Of Performance and is the official figure assigned to all air source heat pupmps. It is the ratio beween the input/output energy. The higher the SCOP, the higher the RHI payments.


What Is The Minimum Tempterure ASHP's Work?

Most Air Source Heat Pumps operate down to around -15°C, however, are more efficient at temperature of 0°C and higher.


Are Air Source Heat Pumps Noisy?

This is a common misconception with air source heat pumps. Most air source heat pumps operate at between 40-60 decibels. We often compare the noise levels to that of a domestic microwave.

How Does It Pump Heat My Hot Water?

Heat pumps are more efficient, when commissioned at lower temperatures (the SCOP value is increased), and as such, this means the we want to design your air source heat pump system to operate at the lowest temperature possible. We generally design our systems to operate between 35°C – 45°C for underfloor heating systems, and 50°C – 55°C for radiator systems. This presents an issue when it comes to heating your hot water, which must be stored at 60°C, or greater, to avoid the risk of legionella. As such, the heat pump will rely on the electric immersion heater to top it cylinder up from it’s flow temperature, to that required by your hot water system

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Cinergi are based just inside the New Forest, around 10 minutes outside Southampton City Centre. We cover the surrounding towns and counties such as Portsmouth, Bournemouth, Salisbury, Winchester, Oxfordshire, Wiltshire, Dorset, Surrey and Berkshire. We are always on call for any questions or queries you may have. 

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