Publication 1747-UM011G-EN-P - June 2008
62 System Installation Recommendations
• Use 2.54 cm (1 in.) copper braid or 5.2 mm
2
(#10 AWG) copper wire to
connect each chassis, the enclosure, and a central ground bus mounted
on the back-panel.
• Use a steel enclosure to guard against electromagnetic interference
(EMI).
• Make sure the enclosure door viewing window is a laminated screen or a
conductive optical substrate (to block EMI).
• Install a bonding wire for electrical contact between the door and the
enclosure; do not rely on the hinge.
Connect Ground Bus to Grounding-Electrode System
The grounding-electrode system is at earth-ground potential and is the central
ground for all electrical equipment and ac power within any facility. Use a
grounding-electrode conductor to connect the ground bus to the
grounding-electrode system. Use at minimum 8.3 mm
2
(#8 AWG) copper wire
for the grounding-electrode conductor to guard against EMI. The National
Electrical Code specifies safety requirements for the grounding-electrode
conductor.
Europe: Reference EN 60204 for safety information on grounding. Also, refer
to Allen-Bradley Programmable Controller Grounding and Wiring Guidelines,
IMPORTANT
Do not lay one ground lug directly on top of the other; this type
of connection can become loose due to compression of the
metal lugs. Place the first lug between a star washer and a nut
with a captive star washer. After tightening the nut, place the
second lug between the first nut and a second nut with a
captive star washer.
Equipment Grounding Conductors
Ground Lug
Grounding-Electrode
Conductor to
Grounding-Electrode
System
Tapped Hole
Ground Bus
Ground Bus
Mounting
Bolt - Size M5 or M6 (4.826
mm or 5.48 mm) hardware
Internal star washer - Size
M5 or M6 (#10 or #12)
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