Hydor Hanging Non-shuttered Belt Drive Fan. The Hydor Belt Drive Unit is specifically designed to ventilate larger buildings where substantial amounts of air are moved at low pressure with minimal energy consumption. The full range is available in 5 sizes 800, 1000, 1250,1500 and 2000mm each with single or three phase motors. The Belt Drive Range is available in three variations; wall mounting with shutters, suspension mounting from the roof space or floor mounting with wheels.