Page 257 - Electrician - TT (Volume 2)

ELECTRICIAN - CITS

12 Grounding Principle: Wire all grounds to the incoming ground lug either directly or with a wire to the other
ground bus bars. Add a main ground lug and/or a ground bus bar for each grounded power supply. A number
of busbars can be utilized but should all be wired together and then to the incoming ground lug to at least 1
point if not two (2). This is in addition to the ground established through the panel. Use 2 ground wires from
opposite ends of the bus or chain of ground bars if the ground is isolated. Wire the ground on all doors and
subpanels and the cabinet itself to a ground bar terminated at the main ground lug. Wire all equipment and
chassis grounds to the ground bar(s) which is terminated at the main ground lug. For additional details on
grounding and bonding see the Grounding and Bonding post dedicated to just this subject.

Panel layout considerations

Example of good spacing between the terminals and the wire way.

1 Optimize the Space: Place I/O racks in the “bay” created by the wiring duct to allow room for the high density
of wires going to them from the duct. Don’t leave space where there is no wiring, typically the top of the I/O
rack. Place similar sized devices in their own “bay” where possible. Consider the routing of all of the wires
and how the various voltages will be kept separated.
2 Spacing between wired devices and wire way or other obstructions: 2″ minimum; 2 1/2 – 3″ preferred for
120VAC and less. 4″ for 480 volts (enough to insert a closed fist between the device and the wire way, another
device, or obstruction.

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CITS : Power - Electrician & Wireman - Lesson 93-100