Uses electronic enlargement valve to exactly control the flow of R290 refrigerant into the evaporator in addition to a four-way valve to divert the refrigerant flow for your defrost Procedure They established to work and at the end of the working day experienced eradicated almost most of the outdated equipment.From https://purethermal.co.uk/media-news/q4-launch-lithium-large-capacity-r290-ashp-from-pure-thermal-and-enerblue/