In this presentation we discuss what Variable Refrigerant Flow (VRF) systems are with emphasis on 2-Pipe systems and the heat pump and heat recovery configurations. An overview of VRF Technology including indoor units, solenoid box, outdoor units and controllers is provided. Also covered are VRF system design concepts including compressor technology, oil management and piping and flow. In addition the presentation will cover VRF considerations of application, layout considerations and the need for selection software.