The Ultimate Glossary For Air Source Heat Pumps

Read our latest blog to help simplify your heat pump journey

When looking into installing a heat pump, there can be a lot of technical terms used to describe objects and processes. This can make it hard to understand what you want and need from an air source heat pump - especially if you don’t work in the industry.

That’s why we’ve created a keyword glossary to make researching an installation and your entire heat pump journey easier for you.


  • Air source heat pump -  A heat pump is a device that can provide heating (or cooling) to a building by transferring thermal energy from the outside ambient air using refrigerants . To learn more about how heat pumps work, watch our quick video.

  • Air to air - This is where heat pumps transfer thermal energy  from the outside air, to the air inside a room.

  • Air to water - This is where the heat pump transfers thermal energy  from the air outside and to water, in a radiant heating system. 

  • Ambient - The normal atmospheric conditions of temperature and pressure.

  • ACRIB - Air conditioning and refrigeration industry board.



  • COP - Coefficient Of Performance. This is the relationship between the power (kW) that is drawn out of the heat pump as heating or cooling and the power that’s supplied to the compressor. 

  • Carbon footprint -The total amount of greenhouse gases produced by our actions.

  • Carbon neutral - This is where carbon emissions have been balanced out through carbon savings.

  • Carbon emissions - This is when carbon compounds like carbon dioxide are released into the atmosphere due to human activity, for example through burning fossil fuels.

  • Compressor - The heart of a refrigeration system. A mechanical device that increases the pressure of a gas by reducing its volume and pumps it round the system.

  • Condenser - The heat pump condenser is where the heat is transferred from the heat pump cycle to the water system. It is a high temperature heat exchanger where refrigerant enters  as vapour and leaves a liquid.  

  • Co2 - Also known as carbon dioxide, which is produced by burning carbon, organic compounds or through respiration.


  • Emitters - A product that sends out heat (or sometimes cooling) . For example, radiators and underfloor heating can emit warmth and fan coils can both heat and cool. To learn more about heating emitters, read our blog.

  • EPC - Energy Performance certificate. These show potential home owners or tenants how energy efficient a building is.

  • Efficiency rating - efficiency ratings refer to how much power and appliance uses to reach maximum efficiency and how much energy is wasted. 

  • Evaporator - The evaporator is another heat exchanger and is part of the heat pump that transfers heat into the refrigerant, turning it into a gas . 


  • Fan coil units - Fan coil units use an electric fan to push out warm or cold air.

  • F-Gas Certification -  The F-Gas regulations place legal obligations on companies and the users of refrigeration & air conditioning equipment. The overall aim of F-Gas is to reduce and contain emissions by using responsible refrigeration. 


  • Ground source - A ground source heat pump transfers thermal energy from the ground outside your property to the air inside your property .

  • GWP -  This stands for Global warming Potential. It is a measure of how destructive a climate pollutant is in relation to CO2.

  • Greenhouse gases - Greenhouse gases are gases in the atmosphere that trap heat.


  • Heat output - The amount of energy a heat pump releases to heat a room.

  • High flow temperature - The 'flow temperature' is the temperature your heating system heats up the water to before sending it off to your emitters. High flow temperatures are typically between 60-80ºC.  .

  • High temperature heat pump - High temperature heat pumps can reach up to 80ºC (similar to boiler temperatures).

  • Heat pump grants - Heat pump grants are schemes that offer money to help you afford the cost of a heat pump; if you meet the eligibility criteria.

  • HVAC - Stands for heating,ventilation and air conditioning. 

  • Heat capacity - The heat capacity of a substance is the amount of heat required to raise the temperature of a defined amount of pure substances by one degree and is measured in Joules per Kelvin or Joules per degree Celsius.

  • Heat transfer - This is the exchange of thermal energy between two interacting media passing through a heat exchanger. 

  • Heat exchange - Is the process where a refrigerant moves heat from one set of coils to another, allowing a heat pump to heat your property. 


  • kW - Stands for kilowatt, which is how much power an appliance needs to run.

  • kWh - Stands for kilowatt per hour, which is how many kilowatts are produced per hour. 


  • Low flow temperature - This is when something operates between 40-50ºC.



  • Packaged unit - This is a self contained air handling unit specifically designed for outdoor installation. The unit includes all pre-assembled heating and cooling devices.


  • Radiant heating - This is a system where heat is produced and transferred through the underneath of your floors, so that the heat rises from the floor upwards.

  • Renewable energy - Energy derived from natural sources that are replenished quicker than they’re consumed.  

  • Refrigerant - A refrigerant is a chemical compound that uses a small amount of energy to change from liquid to gas and back to liquid again. 

  • Refrigerant cycle - The refrigerant cycle works on the laws of thermodynamics, and revolves around the refrigerant changing state between liquid and gas throughout the process, releasing energy into the system as it goes.

  • Refrigerant charge - The amount of refrigerant in kg in a closed system.

  • R290 - This is the technical name for the natural refrigerant also known as propane. R290 is used in commonly used appliances like fridges and air conditioners and has GWP of 3.

  • Retrofit - Retrofitting a building involves changing its systems or structure after its initial construction and occupation, like changing a gas boiler to a heat pump


  • SCOP - Stands for Seasonal Coefficient Of Performance, which refers to the average COP (Coefficient of performance) of a heating season.


  • The energy transition - The global energy sector plans to shift from fossil based energy production and consumption to renewable energy sources like wind turbines or solar panels.


Get in touch with Enula today to see how we can make an air source heat pump work for you!

Related Blog Posts

Sorted UK Logo

Driving Britain’s heat pump revolution
Go green. Think #zeroforgood.

Facebook IconTwitter IconFacebook IconInstagram Icon

Birmingham Rd, Henley-in-Arden, B95 5QR

0121 759 7590

Mon - Fri: 08.45 – 17.00

© 2024. All Rights Reserved.
Enula Logo