250.30 (a) (3)

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easymoney

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If I have a 3-phase 120/208Y transformer and I connect the GEC to the XO on ithe transformer. Then I run a grounded conductor from the XO on the transformer to the lug in the breaker panel, I also run a grounding conductor from the XO in the transformer to the grounding lug in the panel. First question is that correct of efficent? second do I need to bond them together in the breaker box?
 
easymoney said:
If I have a 3-phase 120/208Y transformer and I connect the GEC to the XO on ithe transformer. Then I run a grounded conductor from the XO on the transformer to the lug in the breaker panel, I also run a grounding conductor from the XO in the transformer to the grounding lug in the panel. First question is that correct of efficent? second do I need to bond them together in the breaker box?
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The grounding conductor that you mention would be the "equipment bonding jumper" mentioned in 250.30(A)(2). It must be sized per T250.66.

The grounded and grounding conductors should NOT be bonded together at the panel. The GEC must be connected where the system bonding jumper is installed. So the bonding in your example is at the transformer, not at the panel.
 
The method you prescribe is one of the acceptable means. (also the most common method I see)
 
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