Dimensions and technical details Regulation of speed of fans with the principle of generalised phase control (During the lower speeds a buzzing sound might develop. For environments that need to be kept quiet a step transformer is recommended.) Setting the minimum rotation speed with potentiometer on switch (motor should still start smoothly) When connecting several fans to one controller, 10% reserve load should be calculated, attention has to be paid to the rated load / maximum load WS 1.5 and WS 2.5: for commercially available flushed mounted sockets, compatible with switch systems of other manufacturers (requirement: rotary knob for 6mm axis) WS 5.0 and WS 10.0: switch for surface mounted sockets, synthetic material (light grey / white) Model Volts A max. Dimensions (H x W x D in mm) Protection class WS 1.5 220- 240 1.5 A 86 x 86 x 65  IP55/ 44 WS 2.5 220- 240 2.5 A 86 x 86 x 65  IP55/ 44 WS 5.0 220- 240 5.0 A 83 x 160 x 71 IP54 WS 10.0 220- 240 10.0 A 115 x 195 x 95  IP54.