Siemens CPU 313C Hardware And Installation Manual page 191

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When you install the automation equipment, make sure that surfaces of inactive
metal parts are well bonded to chassis ground (see the following sections).
• Bond all passive metal parts to chassis ground, ensuring large area and low-
impedance contact.
• When using screw connections on varnished or anodized metal parts, support
contact with special contact washers or remove the protective insulating finish
on the points of contact.
• Wherever possible, avoid the use of aluminum parts for ground bonding.
Aluminum oxidizes very easily and is therefore less suitable for ground bonding.
• Create a central connection between chassis ground and the equipotential
grounded/protective conductor system.
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Ensure proper cable routing when you wire your system (see the section below on
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• Sort your wiring system into groups (high-voltage/power supply/signal/data
cables).
• Always route high-voltage, signal or data cables through separated ducts or in
separate bundles.
• Install the signal and data cables as close as possible to grounded surfaces
(e.g. supporting beans, metal rails, steel cabinet walls ).
S7-300 Automation System, Hardware and Installation: CPU 31xC and CPU 31x
A5E00105492-03
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