Centrifugal fan RD..A design Specification: Double inlet centrifugal fans in standard scroll housings with backward curved blades. Impeller diameters from 315 to 560 mm are available, resulting in air volumes up to 27,000 m³/h. Attributes and special features: Optimal motor cooling and a compact construction achieved through integrating the voltage controllable external rotor motor into the impeller. Applications: Close control units, exhaust plants, gate and door air-curtains, flat devices