C h a p t e r 4 : H a r d w a r e I n s t a l l a t i o n 5 1
Serial and Ethernet Cable Segregation and Placement
Serial and Ethernet Cable Segregation
The low power cabling used for PLC and PC-based control systems is very susceptible
to electrical noise generated by high power conductors. Even when protected by conduit,
noise can interfere with your communication lines and networks. Therefore it is important
to segregate conductors according to their type.
Category
Description
Examples
Category 1
High Power Conductors
These conductors can cause
electrical noise in Category 2
conductors when in close proximity.
Are more tolerant of electrical noise
than Category 2.
Reference: NEC article 725 class 1
Reference: IEEE level 3 and 4
•
AC power lines
•
High power digital AC and
DC lines
•
Typically these conductors
are used to connect hard-
contact switches, relays,
solenoids, motors,
generators and arc welders.
Category 2
Low Signal Level Conductors
These conductors are less tolerant
of electrical noise; however, they
cause less noise in adjacent
conductors.
Reference: NEC article 725 class
2, class 3
Reference: IEEE level 1 and level 2
•
Communication cables—
Ethernet, PLC networks, etc.
•
Low power digital AC and
DC I/O lines
•
Typically these conductors
are used to connect PLCs
and related modules with
PanelMate ePro PSs
Cable Placement
The following guidelines should be used when installing your communication cables:
•
All Category 2 cables should be shielded and routed in a separate conduit or
raceway from Category 1 cables.
•
Route Category 2 cables at least one foot from 120 VAC power lines.
•
Route Category 2 cables at least two feet from 240 VAC power lines.
•
Route Category 2 cables at least three feet from 480 VAC power lines.
•
Route Category 2 cables at least five feet from high voltage enclosures.
•
If a Category 2 cable must cross Category 1 cables, it should cross at a right angle
(No parallel runs).
•
If Category 2 cable is enclosed in metal conduit or a metal raceway, electrical
continuity must be maintained along the entire length of the conduit/raceway
installation, including entry into the enclosure.