Rockwell Automation 1747-L5xx SLC 500 Modular Hardware Style User Manual - Manual (Page 190)

Publication 1747-UM011G-EN-P - June 2008
190 Setting Up the DH-485 Network
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 20 A, 0.30 m (1 ft)
from lines greater than 20 A, but only up to 100 k VA, and
0.60 m (2 ft) from lines of 100 k 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 20 A, 0.15 m (6 in.) from lines
greater than 20 A, but only up to 100 k VA, and 0.30 m (1 ft)
from lines of 100 k 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 Grounding Guidelines, publication 1770-4.1.