VRV/ VRF:
Variable refrigerant volume (VRV) or variable refrigerant flow (VRF) systems extract or deliver heat to individual zones as required using refrigerant to air heat exchangers. They have multiple indoor units with a refrigerant flow distributor control device. This device controls the refrigerant with a PID control loop with the inputs being sent and received on a communication system. These systems generally offer high efficiency through the effective use of speed-controlled compressor, heat exchangers and controls. Heat recovery regimes allow rejected heat to be transferred within a building or stored as hot water. Typically there are 20–40 units on one system, although some manufacturers can allow as many as 64 indoor units. Individual indoor units can provide heating or cooling as required using either a three or two pipe system. Specialised heat recovery systems employ refrigerant distribution units with vapour and fluid separation and flow control. Some systems can provide simultaneous heating and cooling. Heat recovered from units providing cooling is transferred to units providing heating. With an extensive choice of indoor units these systems are suitable for larger buildings and offer installation flexibility.
