When you go down the path of investigating heat pumps you will also be faced with the need to understand what refrigerants are used with these heat pumps. Refrigerants are the ‘blood’ of heat pumps that allow heat to be transferred from one place to another. These refrigerants are specific to the design of these heat pumps and cannot be simply swapped out of a heat pump for another refrigerant. A useful analogy is the issue with using diesel in a petrol car. They are both fuels, however they are not at all compatible in both vehicles.
It is essential when discussing heat pumps that you have a basic understanding of refrigerants and their key characteristics.
Classes of Refrigerants
Refrigerants can be broadly divided into these classes-
- Hyrdoflourocarbons (HFCs) currently being phased out
- Hydrofluoroolefins (HFOs) potentially being phased out due to pollution risks
- Hydrocarbons (HCs) such as Isobutane and Propane
- Carbon Dioxide (CO2) which is used extensively in refrigeration
- Ammonia (NH3) which is used extensively in industrial refrigeration
To further complicate matters, some classes of refrigerants are being phased down as we now know that they are harmful to the atmosphere. You can read about these refrigerants and the how Australia is dealing with this in a comprehensive article that AIRAH produced here.
Global Warming Potential (GWP)
This is a rating that is applied to refrigerants that measures the effect on the atmosphere relative to the effect of CO2. For example NH3 has no effect on the atmosphere, so it has a GWP of 0. CO2 has a GWP of 1, and R32 has a GWP of 675. So for every 1 kg of R32 that escapes from your heat pump, this will produce an effect in the atmosphere of around 675kgs of CO2. This is a key issue with the phasedown of these refrigerants and needs to be considered carefully when selecting a heat pump for an application as we move further down the path of the effects of climate change.