Takes advantage of electronic enlargement valve to precisely Management the flow of R290 refrigerant to the evaporator in addition to a 4-way valve to divert the refrigerant movement for that defrost operation An air-to air technique could be made to transfer heat in either way, to heat the inside of https://purethermal.co.uk/media-news/q4-launch-lithium-large-capacity-r290-ashp-from-pure-thermal-and-enerblue/