Uses Digital enlargement valve to precisely Manage the movement of R290 refrigerant in the evaporator in addition to a 4-way valve to divert the refrigerant flow for the defrost Procedure The refrigerant within an air-source heat pump absorbs heat with the outside air and turns into a gas via evaporation. https://ez-bookmarking.com/story20417228/5-simple-statements-about-r290-propane-heat-pump-explained