Switch cabinet Section 6  Wiring
86 M&I – AC 900F Controller
 
Switch cabinet
• Low-impedance connections between the switch cabinet, mounting plate, 
earthing bar (PE) and shield bar must be provided.
• Earth the switch cabinet doors on the sides using short and highly flexible 
conductors.
• To protect the control system against interferences, only bulbs or interference-
suppressed fluorescent/LED lamps should be used in the direct vicinity of the 
control system for switch cabinet lighting.
• If an interference immunity of 6 kV instead of 4 kV is required, the controller 
must be installed in a switch cabinet and operated exclusively with the door 
being closed.
Minimum distances
• Provide for adequate distances to the switch cabinet walls, cable conduits, 
adjacent devices, etc. There should be a distance of 20 mm around the 
controller to all sides in order to ensure proper ventilation and electrical 
insulation.
• Horizontal installation is highly recommended. Vertical mounting is also 
possible, but involves restrictions in terms of performance due to insufficient 
air circulation, which causes heating of the devices. 
• When mounting the system in vertical position, mechanical stops must be 
provided at the top and the bottom to protect the modules against vibrations. 
For applications with high levels of vibration, the installation of mechanical 
stops on the left and right sides is also recommended for horizontal mounting 
in order to efficiently protect the modules against vibrations.
Reference potential
• Ensure a uniform reference potential throughout the line and earth the complete 
electrical equipment, as far as possible.
• Install the earth conductors in star configuration to avoid the formation of 
ground loops.