Employs electronic expansion valve to precisely Regulate the flow of R290 refrigerant in the evaporator as well as a 4-way valve to divert the refrigerant move for the defrost Procedure Air source heat pumps use exactly the same kind of technologies that retains a fridge or freezer neat – but https://purethermal.co.uk/media-news/q4-launch-lithium-large-capacity-r290-ashp-from-pure-thermal-and-enerblue/