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3-6 Connecting commercial power
Procedure 3-1 (continued)
Connecting earth ground to the ac load box
Action
Step
1
2
3
AC grounding electrode installation
(typical for a main service entrance panel):
4
5
6
7
8
9
10
11
AccessNode 323-3001-210 Issue 1.0
Action
Unbolt and set aside the ac compartment lower panel.
Turn all circuit breakers in the ac load box to the OFF position.
Open the door and remove the distribution load center cover panel.
CAUTION 3
AC grounding electrode installation
For a main service panel entrance, an ac grounding
electrode system requires bonding to an ac main service
power neutral/ground bus. Consult the local power
company or telco for code restrictions or NEC variations.
Ensure that the ac ground rod or ring (electrode) has been installed per local,
telco, and NEC code requirements.
Measure the ground-to-earth resistance.
Note: The ground-to-earth resistance must be less than or equal to 25 Ω.
Attach a 6 AWG tinned copper wire to the exterior cabinet ground rod.
Route the wire into the cabinet through the 1.00-inch conduit entrance
located in the ac compartment.
Punch out a 1/2-inch NPT knockout on the left side of the load box using the
first available 1/2-inch position.
Use a T&B 3302M type 1/2-inch NPT knockout bushing or equivalent to
protect the ground wire from sharp edges.
Route the 6 AWG wire through the knockout bushing into the load center.
Attach the grounding electrode to the available grounding bus bar position in
the load box (per NEC 250-23/81/84/91/92).
—end—
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