Direct Expansion Units, DX Units
Direct-expansion air conditioning units, which are units that come with an integrated compressor. They cool the air (the indoor air of the air conditioner) by directly evaporating (expanding) the refrigerant in the evaporator coils, absorbing heat from the air outside the coils. Direct-expansion air conditioning units perform heat exchange directly with the air that needs to be treated, without passing through a secondary heat exchange.
