DVG smoke and heat extract fans are used in case of fire to extract smoke gases from rooms, and also during normal working conditions for standard ventilation. Smoke-free escape ways increase the chances to rescue people in case of fire. The casing is manufactured from seawater resistant aluminium. The base frame is made of pre-galvanised steel, zinc-magnesium (ZM) coated. Impeller with backward-curved blades is manufactured from pre-galvanized steel (sizes 355, 450), respectively from steel, welded and galvanised. Motor outside air stream is cooled with fresh air. Electric motor of IE1 standard efficiency, single or two speed, respectively IE2 high efficiency single speed motor at 4 and 6 pole fans from 0,75 kW output power. PTC serial built-in. For two speed fans (up to 4 kW) two speed switch is available as accessory (in this case thermal contact must be ordered; not suitable for PTC or without thermal contact). In case of fire eventual two speed switch and all motor protective devices must be bridged to guarantee functional capability (connection direct to the mains). For speed control use only frequency converter (please see instructions for details). Not suitable for voltage control. If frequency converter used in case of fire, PTC must be bridged and switching on max. speed even after eventual short supply cut off assured. Operating over 50 Hz is allowed at units on request only. At frequency controlled units additional EMC protection could be needed (on request). Please observe capability of service switch for cable connection. The data of input power and current may slightly vary due to different motor supllier.