Rockwell Automation 1770 Industrial Automation Wiring and Grounding Guidelines - Manual (Page 3)

Industrial Automation Wiring and Grounding Guidelines 3
Publication 1770-4.1 – February 1998
Route Conductors
To guard against coupling noise from one conductor to another,
follow these general guidelines (Table B) when routing wires and
cables (both inside and outside of an enclosure). Use the spacing
given in these general guidelines with the following exceptions:
•
where connection points (for conductors of different categories)
on a device are closer together than the specified spacing
•
application-specific configurations for which the spacing is
described in a publication for that specific application
These guidelines are for noise immunity only. Follow all local
codes for safety requirements.
Table B
Follow these Guidelines for Routing Cables to Guard
Against Noise
Route this category
of conductor cables:
According to these guidelines:
Category 1 These conductors can be routed in the same cable tray or raceway with machine power conductors of up to 600V ac
(feeding up to 100 hp devices).
Category 2
•
If it must cross power feed lines, it should do so at right angles.
•
Route at least 5 ft from high-voltage enclosures, or sources of rf/microwave radiation.
•
If the conductor is in a metal wireway or conduit, each segment of that wireway or conduit must be bonded to each
adjacent segment so that it has electrical continuity along its entire length, and must be bonded to the enclosure at the
entry point.
•
Properly shield (where applicable) and route in a raceway separate from category-1 conductors.
•
If in a contiguous metallic wireway or conduit, route at least 0.08m (3 in) from category-1 conductors of less than
20A; 0.15m (6 in) from ac power lines of 20A or more, but only up to 100 kVA; 0.3m (1 ft) from ac power lines of greater
than 100 kVA.
•
If not in a contiguous metallic wireway or conduit, route at least 0.15m (6 in) from category-1 conductors of less
than 20A; 0.3m (1 ft) from ac power lines of 20A or more, but only up to 100 kVA; 0.6m (2 ft) from ac power lines of
greater than 100 kVA.
Category 3 Route conductors external to all raceways in the enclosure or in a raceway separate from any category-1 conductors with
the same spacing listed for category-2 conductors, where possible.
Important: These guidelines assume that you follow the
surge-suppression guidelines (page 15). While these guidelines
apply to the majority of installations, certain electrically harsh
environments may require additional precautions.
The use of the guidelines in Table B are illustrated in Figure 1.