The Estoc square duct fan is available in a range of sizes from 500mm to 1020mm square boxes and cover duties up to 5.2 cubic meters per second flow rate and 1150 pascals pressure and can operate in temperatures up to 55°C. All units are fitted with AC external rotor motors which run via a 230V single phase or 400V three phase feed, depending on unit size. The motor drives a backward curved centrifugal impeller. Impellers up to 450mm in diameter are of injection moulded plastic construction, whereas impellers of 500mm and larger are manufactured from aluminium. The Square duct fan casing is constructed using a Pentapost frame which supports pre-galvanised steel sandwich panels, each filled with 20mm thick mineral wool for acoustic insulation. Each unit comes with 4 panels, all of which can be removed and relocated to give multiple outlet orientations at either 90 degrees to the inlet or 180 degrees for straight through air movement.