Rockwell Automation 1770 Industrial Automation Wiring and Grounding Guidelines - Manual (Page 2)

Industrial Automation Wiring and Grounding Guidelines 2
Publication 1770-4.1 – February 1998
The raceway layout of a system is reflective of where the different
types of I/O modules are placed in I/O chassis. Therefore, you
should determine I/O-module placement prior to any layout and
routing of wires. However, when planning your I/O-module
placement, segregate the modules based upon the conductor
categories published for each I/O module so that you can follow
these guidelines. Also, all conductors (ac or dc) in the same raceway
must be insulated for the highest voltage applied to any one of the
conductors in the raceway. These guidelines coincide with the
guidelines for “the installation of electrical equipment to minimize
electrical noise inputs to controllers from external sources” in IEEE
standard 518-1982.
Categorize Conductors
Segregate all wires and cables into the following three categories
(Table A). Refer to the publication for each specific I/O module or
block for individual conductor-category classification of each I/O
line.
Table A
Follow these Guidelines for Grouping Conductors with
Respect to Noise
Group conductor cables fitting this description
Into this
category:
Examples:
Control & ac Power — high-power conductors that are
more tolerant of electrical noise than category 2
conductors and may also cause more noise to be picked
up by adjacent conductors
•
corresponds to IEEE levels 3 (low susceptibility) &
4 (power)
Category 1
•
ac power lines for power supplies and I/O circuits.
•
high-power digital ac I/O lines — to connect ac I/O modules rated for
high power and high noise immunity
•
high-power digital dc I/O lines — to connect dc I/O modules rated for
high power or with input circuits with long time-constant filters for high
noise rejection. They typically connect devices such as hard-contact
switches, relays, and solenoids.
Signal & Communication — low-power conductors that
are less tolerant of electrical noise than category-1
conductors and should also cause less noise to be
picked up by adjacent conductors (they connect to
sensors and actuators relatively close to the I/O
modules)
•
corresponds to IEEE levels 1 (high susceptibility) &
2 (medium susceptibility)
Category 2
•
analog I/O lines and dc power lines for analog circuits
•
low-power digital ac/dc I/O lines — to connect to I/O modules that are
rated for low power such as low-power contact-output modules
•
low-power digital dc I/O lines — to connect to dc I/O modules that are
rated for low power and have input circuits with short time-constant
filters to detect short pulses. They typically connect to devices such as
proximity switches, photo-electric sensors, TTL devices, and encoders
•
communication cables (ControlNet t , DeviceNet t , Universal remote
I/O, extended-local I/O, DH+

, DH-485, RS-232-C, RS-422, RS-423
cables) — to connect between processors or to I/O adapter modules,
programming terminals, computers, or data terminals
Intra-enclosure — interconnect the system components
within an enclosure
•
corresponds to IEEE levels 1 (high susceptibility) &
2 (medium susceptibility)
Category 3
•
low-voltage dc power cables — provide backplane power to the
system components
•
communication cables — to connect between system components
within the same enclosure
NOTE: Remote I/O and DH+ cables must be made of catalog number 1770-CD cable or a cable from the approved-vendor list (publication ICCG-2.2).
DH-485 cables must be made of a cable from the approved-vendor list in publication 1770-6.2.2.
Raceway Layout
Considerations