Abstract: This disclosure relates to a heat exchanger which includes an A-coil through which a heat-exchange medium (refrigerant) is circulated between an inlet and an outlet thereof, a compressor in fluid communication with the outlet for compressing a vapor phase of the heat-exchange medium, and means for generating heat beyond and as an augment to ambient temperature sufficient to transform the liquid phase of the heat-exchange medium to its vapor phase during the passage of the heat-exchange medium from the inlet to the outlet with substantially total absorption of the heat by the heat-exchange medium for subsequent extraction of the heat from the vapor phase to effect desired heating.