Employs electronic expansion valve to precisely Manage the flow of R290 refrigerant in to the evaporator in addition to a 4-way valve to divert the refrigerant movement to the defrost operation The Haier Air to H2o Heat Pump assortment uses cost-free renewable Power from the skin air as a heat https://purethermal.co.uk/media-news/q4-launch-lithium-large-capacity-r290-ashp-from-pure-thermal-and-enerblue/