Employs Digital expansion valve to exactly Manage the movement of R290 refrigerant in to the evaporator in addition to a 4-way valve to divert the refrigerant stream for your defrost operation Having a heat pump indicates you may be part of a heat pump tariff! Our heat pump tariffs are https://purethermal.co.uk/media-news/q4-launch-lithium-large-capacity-r290-ashp-from-pure-thermal-and-enerblue/