Reference
Understanding the Communication Protocols
D–17
Planning Cable Routes
Follow these guidelines to help protect the communication cable from electrical
interference:
• Keep the communication cable at least 1.52 m (5 ft) from any electric motors,
transformers, rectifiers, generators, arc welders, induction furnaces, or sources
of microwave radiation.
• If you must run the cable across power feed lines, run the cable at right angles
to the lines.
• If you do not run the cable through a contiguous metallic wireway or conduit,
keep the communication cable at least 0.15 m (6 in.) from ac power lines of less
than 20A, 0.30 m (1 ft) from lines greater than 20A, but only up to 100k VA,
and 0.60 m (2 ft) from lines of 100k VA or more.
• If you run the cable through a contiguous metallic wireway or conduit, keep the
communication cable at least 0.08 m (3 in.) from ac power lines of less than
20A, 0.15 m (6 in.) from lines greater than 20A, but only up to 100k V
A, and
0.30 m (1 ft) from lines of 100k VA or more.
Running the communication cable through conduit provides extra protection
from physical damage and electrical interference. If you route the cable through
conduit, follow these additional recommendations:
– Use ferromagnetic conduit near critical sources of electrical interference.
You can use aluminum conduit in non-critical areas.
– Use plastic connectors to couple between aluminum and ferromagnetic
conduit. Make an electrical connection around the plastic connector (use
pipe clamps and the heavy gauge wire or wire braid) to hold both sections
at the same potential.
– Ground the entire length of conduit by attaching it to the building earth
ground.
– Do not let the conduit touch the plug on the cable.
– Arrange the cables loosely within the conduit. The conduit should contain
only serial communication cables.
–
Install the conduit so that it meets all applicable codes and environmental
specifications.
For more information on planning cable routes, see Industrial Automation Wiring
and Gr
ounding Guidelines
, Publication Number 1770-4.1.
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