FRU is a measuring diffuser 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 diffuser and a DCT type damper put together to form a complete diffuser. VRU is used for volume flow regulation of 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 current volume flow is determined by a control signal from, for example, Regula Combi, CTS 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 an 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.