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Wiring rules
Installation box wiring
Building wiring
Different types of cable
in one cable duct.
Cable types
Separate cables
Shielded cables
Screened cable
18 / 56
Siemens
Building Technologies
5.5
EMC compliant wiring
If heavy EMC disturbance is expected in an installation box or in the building, the
following wiring rules can better protect potential victims:
• In the installation box, separate unshielded lines from shielded lines at the
terminal connections and cable ducts.
• Avoid cable loops.
• Plan sufficient space to correctly connect the cable screens.
• Connect cable screens to the installation box directly at the inlet to the
installation box. Leave screen intact to the module.
• Integrate the installation box with the building's potential equalization.
When setting up cable ducts, separate strongly disruptive cables from victims.
• Disruptive cable:
• Possible victims: Control cables, low-voltage cables, interface cables,
• Both types of cables may be in the same cable duct, but should be place is
separate compartments.
• If not three-sided duct with separating wall is available, the disruptive cables
must be separated by at least 150 mm from the others or placed in separate
ducts.
• The crossing of strongly disruptive cables should be at a right angle to potential
victims.
• Comply with the manufacturer's installation recommendations for the selection of
shielded or unshielded cables. In general, unshielded twisted pair cables have
sufficient EMC properties for building-technical applications (including data
applications.
• Unshielded round wires can also be used for the island bus (wire CS, CD).
• Benefit: Unscreened cables do not need to be coupled to the surrounding
ground.
Screening improves EMC properties. Please note the following, however:
• The grounding (common reference point), is tasked with diverting and short
circuiting existing interference voltage.
• Special emphasis must be placed on the grounding concept to prevent
grounding loops or differences in potential○.
• Against low-frequency interference: Ground the screen on one side only.
• Screens must be connected on both sides with the ground against high
frequencies. Potential equalization must never take place via the cable screens.
A separate potential equalization must be installed when missing.
Alternative: hard wired earthing on one side, via a capacitor on the other side.
• The cable screens must be properly connected to the ground to achieve a solid
level of screening (see below).
• Island bus extension, see: TX-I/O engineering and installation, CM110562)
Mounting and installation
Installation box TRA
Motor cables, energy cables.
LAN cables, digital and analog signal cables.
CM111043en_03
2013-02-23
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