Works by using Digital enlargement valve to exactly Handle the stream of R290 refrigerant in to the evaporator in addition to a 4-way valve to divert the refrigerant circulation for that defrost Procedure The ECOMOD 290HT number of monobloc air source heat pumps come in 3 chassis sizes and 5 https://purethermal.co.uk/media-news/q4-launch-lithium-large-capacity-r290-ashp-from-pure-thermal-and-enerblue/