Rockwell Automation Allen-Bradley ControlNet 1734-ACNR User Manual page 184

C-22 Determine Your ControlNet Media Requirements
Publication CNET-UM001C-EN-P - November 2005
Wire Inside Enclosures
Cable sections that run inside protective equipment enclosures are relatively
short. As with wiring external to enclosures, you should maintain maximum
separation between your ControlNet cable and Category-1 conductors.
When you are running cable inside an enclosure, route conductors external to
all raceways in the same enclosure, or in a raceway separate from Category-1
conductors.
Table C.5 Cable Routing Distances
Route your cable at least this distance:
0.08 m (3 in)
0.15 m (6 in)
0.6 m (24 in)
Surge Suppression
Transient electromagnetic interference (emi) can be generated whenever
inductive loads such as relays, solenoids, motor starters, or motors are operated
by "hard contacts" such as push-button or selector switches. These wiring
guidelines assume you guard your system against the effects of transient emi by
using surge-suppressors to suppress transient emi at its source.
Inductive loads switched by solid-state output devices alone do not require
surge suppression. However, inductive loads of ac output modules that are in
series or parallel with hard contacts require surge-suppression to protect the
module output circuits as well as to suppress transient emi.
Ferrite Beads
Ferrite beads can provide additional suppression of transient emi. Fair-Rite
Products Corporation manufactures a ferrite bead
(part number 2643626502) which can be slipped over category-2 and
category-3 (RG-6 type trunk cable) conductors. You can secure them with
heat-shrink tubing or tie-wraps. A cable transient emi induced onto the cable
can be suppressed by a ferrite bead located near the end of the cable. The
ferrite bead will suppress the emi before it enters the equipment connected to
the end of the cable.
From noise sources of this strength:
Category 1 conductors of less than 20 A
ac power lines of 20 A or more, up to 100
KVA
ac power lines greater than 100 KVA