FRA is a flow regulator with a measuring cross, which is used for measuring volume flow in rectangular ducts. FRA is equipped with Belimo VRD2, which provides an output signal that is proportional to the volume flow.
VRA consists of an FRA measuring unit and a DJP type damper put together to form a complete regulator. VRA is used for volume flow regulation of rectangular 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 FRA/VRA.
VRA-0 consists of a regulator (Belimo VRD2) with a manual setting and motor. VRA-2 is equipped with a regulator and motor in one unit (Belimo NMV-D2M), which is programmable and has an MP bus. VRA-3 consists of a regulator (Belimo VRD2) with a manual setting and motor with a spring return. Further documentation on the diffusers can be requested from Lindab.