Variable refrigerant flow (VRF), also known as variable refrigerant volume, was a concept developed by Daikin Industries in the 1980s. The technology is based on transferring heat through refrigerant lines from an outdoor compressor to multiple indoor fan coil units. VRF systems vary the amount of refrigerant delivered to each indoor unit based on demand, typically through variable speed drives (VFDs) and electronic expansion valves (EEVs). This technology differs from conventional HVAC systems in which airflow is varied based on changes in the thermal load of the space.
The two main VRF systems are heat pump systems that deliver either heating or cooling, or heat recovery systems that can provide simultaneous heating and cooling. These two applications, plus the inverter-driven technology of the outdoor compressors, allow for greater design flexibility and energy savings. In applications where heating and cooling are simultaneously called for in different zones, VRF heat recovery systems allow heat rejected from spaces that are being cooled to be used in spaces where heating is desired. Read more