FRA is a measuring unit with a measuring cross, which is used for measuring volume flow in rectangular ducts. FRA is equipped with Belimo VRD3, 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 unit. VRA is used for volume flow regulation in 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 actual volume flow is determined by a control signal from, for example, Regula Combi, BMS or another FRA/VRA.
VRA-0 consists of a regulator (Belimo VRD3) with a manual setting and motor. VRA-2 is equipped with a regulator and motor in one unit (Belimo NMV-D3-MP), which is programmable and has MP bus. VRA-3 consists of a regulator (Belimo VRD3) with a manual setting and motor with a spring return. Further documentation on the diffusers can be requested from Lindab.