A split air conditioner comprises two separate units: a condensing unit and an evaporative coil. The condenser and coil are joined by a set of copper tubing known as a line-set, which transfers refrigerant from one unit to another. Ductless or split air conditioners are an excellent cooling option for homes or businesses without ductwork, as they operate solely on electricity and have a very high SEER rating for the best efficiency. If you just added a new room to your home, this may be an option for you.