Allen-Bradley ControlLogix 1756-DH485, User Manual, Page: 29 / 110

Publication 1756-UM532A-EN-P - May 2006
Overview of the DH-485 Network 2-11
Plan 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 VA, 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 Grounding Guidelines, Publication Number 1770-4.1.