A direct exchange heating/cooling system includes a specially designed supplemental air-source heat exchanger (also referred to herein as a High Level Heat Dissipater (“HLHD”). The HLHD is coupled to the primary vapor/hot gas line exiting the system's compressor at a point between the compressor unit and the sub-surface geothermal heat exchange tubing, and is operable only in the cooling mode of system operation. The HLHD includes heat exchange tubing that is sheltered from rain/moisture and has supply and discharge refrigerant transport tubing with relatively equally sized interior diameters, designed solely for mostly vapor (as opposed to liquid) refrigerant transport. The HLHD incorporates at least two check valves, or the like, so as to force hot compressor discharge gas through the HLHD in the cooling mode, and so as to prohibit geothermally warmed refrigerant gas flow through the HLHD in the heating mode. The HLHD has specially designed heat exchangers and may optionally include a fan.