7.7 Connecting the functional earth to the CFU
The CFU must be connected to the functional earth.
If the CFU is mounted on the mounting rail, there is a conductive connection to the DIN rail via
the clamp attachment.
Note
Alternative grounding
You can dispense with the additional grounding wire for the CFU described below, provided
that:
● The CFU is mounted on the recommended mounting rail.
● The mounting rail is permanently connected to the protective conductor system using an
equivalent installation that complies with standards (for example, by attachment to a
grounded control cabinet wall).
Recommendations for connecting the functional earth
Suitable terminals:
You can find information on this on the Internet under: LV 52 catalog (
https://
support.industry.siemens.com/cs/ww/en/view/109744423)
Requirements
● Perform wiring when the supply voltage is switched off.
● Observe the wiring rules.
● Attachment of the grounding cable:
Zone 2 or safer area: Terminal or cable lug
Cross-section of grounding cable
To prevent possible interference, the cross-section of the grounding cable for the mounting rail
must be greater than the cross-section of the grounding cable for the power supply of the CFU.
Note: The grounding cable must have a cross-section of at least 4 mm
2
.
Required tools
● Screwdriver for fastening the connection terminal onto the mounting rail (usually 3 mm)
● Screwdriver for fastening the grounding wire onto the mounting rail
● Wire stripping tool
● Possibly crimp tool
Connecting
7.7 Connecting the functional earth to the CFU
SIMATIC CFU
Commissioning Manual, 08/2019, A5E39252870-AD 65
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