Installation guide

Planning and Designing RIO Cable System

890 USE 101 00 October 2006

Grounding and Surge Suppression

Overview Choose a low impedance earth ground for your cable system, preferably factory

ground. Use 10 gauge wire or larger to ground the cable system. Use a common

single-point ground for the cable system and for all equipment associated with the

system. A separate ground—e.g., a computer ground—may actually cause more

noise because the RIO nodes will not be connected to it.

Earth Ground A low impedance earth ground is necessary on RIO cable systems to assure safety

for maintenance personnel and RIO users. The earth ground also provides a path to

dissipate noise on the cable system. If the ground is poor or nonexistent, a

hazardous shock problem may exist, the cable system will be susceptible to noise,

and data transmission errors will occur. The cable system should be single-point

grounded within 20 ft of the RIO processor—the central ground point may be a tap,

a splitter, or a ground block.

Lightning

Protection for

RIO Cable

Systems

Surge suppressors are recommended when a cable system is installed outdoors or

in any environment where lightning protection is required. The surge suppressor

must be grounded to work properly. An 8 gauge or larger diameter green or bare

grounding wire is recommended. Depending on the site, installation of the

suppressor can possibly introduce ground loops resulting in communication errors.

Drop communication status can be monitored through the use of the STAT block

mentioned in The S908 Status Table section of the Monitoring Remote I/O System

Status chapter of Modicon Ladder Logic Block Library User Guide, 840 USE 101 00.

Note: All nodes connected to the cable system must be grounded. Under no

circumstances should ungrounded equipment be connected to the cable system.

See Modicon Quantum Automation Series Hardware Reference Guide, Appendix

D: Power and Grounding Guidelines, 840 USE 100 00.

This document provided by Barr-Thorp Electric Co., Inc. 800-473-9123 www.barr-thorp.com