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