FRU is a measuring unit with a measuring cross, which is used for measuring volume flow in circular ducts. FRU is equipped with Belimo VRD3, which provides an output signal that is proportional to the volume flow.
VRU consists of an FRU measuring unit and a DCT type damper put together to form a complete unit. VRU is used for volume flow regulation in circular ducts, either for constant volume flow with step control, e.g. controlled by a switch or clock, or for variable volume flow, where the volume flow varies between a defined minimum and maximum limit. The actual volume flow is determined by a control signal from, for example, Regula Combi, BMS or another FRU/VRU.
VRU-0 consists of a regulator (Belimo VRD3) with manual setting and a motor. VRU-2 is equipped with a regulator and motor in one unit (Belimo L/NMV-D3-MP-F), which is programmable and has MP bus. VRU-3 consists of a regulator (Belimo VRD3) with manual setting and a motor with a spring return. Further documentation on the regulator can be requested from Lindab.