Refrigerants Used in Heat Pump Water Heaters
Refrigerant choice affects heat pump design, operating pressure, achievable outlet temperature, safety requirements, data plate information, and sometimes the most suitable test conditions.
For scheme registration, EnergyAE mainly needs the refrigerant type and charge to be consistent across the test report, data plate, manual, and technical specifications.
Common refrigerants
| Refrigerant | Typical features | Registration points to check |
|---|---|---|
| R744, carbon dioxide | Natural refrigerant, GWP 1, non-flammable, high pressure, can suit high outlet temperatures. | Data plate should state refrigerant and charge. Test conditions should cover the product’s intended operating range. |
| R290, propane | Natural refrigerant, low GWP, good efficiency, flammable A3 classification. | Safety design, charge, location, and manual instructions need to be clear. |
| R134a | Older HFC refrigerant, moderate pressure, historically common. | Check whether the product remains suitable for current and future market expectations. |
| R410A | HFC blend, higher pressure than R134a, common in older heat pump products. | Check data plate, charge, and any product transition plans. |
| R32 | Lower GWP than many older HFCs, mildly flammable A2L classification. | Safety classification and manual instructions should be clear. |
CO2, R744
CO2 systems use a transcritical cycle and operate at much higher pressure than many other HPWH refrigerants. They can perform well for high domestic hot water outlet temperatures and can be effective in cold conditions when the system is designed correctly.
Common points to check are rated outlet temperature, test conditions at low ambient temperature, pump or flow control method, refrigerant charge, and high-pressure component ratings.
CO2 system performance is sensitive to water inlet temperature and control design. This can affect how the product should be tested and modelled.
Propane, R290
R290 has low global warming potential and good thermodynamic performance. It is also classified as highly flammable, so the product design, charge, installation location, and service instructions need to address safety requirements.
Common points to check are refrigerant charge on the data plate, safety warnings in the manual, indoor or outdoor installation instructions, maximum outlet temperature, test report model name, and refrigerant details.
For many packaged outdoor HPWHs with low refrigerant charge, R290 can be a practical refrigerant choice. The evidence still needs to be clear and consistent.
How refrigerant choice affects testing
Refrigerant choice can affect maximum achievable water outlet temperature, performance at low ambient temperature, defrost behaviour, high ambient performance, EN 14511 air and water inlet test point selection, and safety information required in manuals and data plates.
For commercial HPWHs, test conditions should be selected before the laboratory program starts. This is especially relevant where the product uses CO2, variable flow control, or high outlet temperature operation.