Combined DC GEC & AC EGC 690.47 (C) (3) termination requirements

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SunFish

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Trying to fully grasp 690.47 (C) (3) in 2011. If I'm landing an inverter output circuit with a backfed breaker in a sub panel am I required to bring the combined unspliced/irreversibly spliced GEC/EGC all the way to the ac grounding busbar in the main service panel where the AC GEC is located or can this terminate at the sub panels grounding busbar? If its is allowed to terminate the GEC/EGC at the busbar in the sub I would assume that the EGC protecting the sub panel must be now be properly bonded on both sides of the raceway between the main and the sub if it is ferrous to prevent inductive choking? I suppose if this is done the EGC between the sub and the main now becomes a continuation of the DC GEC/AC EGC and therefore must be irreversibly crimped together in the sub? Did I just answer my own question?
 

jaggedben

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Trying to fully grasp 690.47 (C) (3) in 2011. If I'm landing an inverter output circuit with a backfed breaker in a sub panel am I required to bring the combined unspliced/irreversibly spliced GEC/EGC all the way to the ac grounding busbar in the main service panel where the AC GEC is located

Yes.

or can this terminate at the sub panels grounding busbar?

No. If the EGC for the panel is adequately sized (usually #8 is required) you could irreversibly splice your solar GEC to the existing EGC, if it also meets the requirements that are the subject of your next question.

If its is allowed to [irreversibly splice] the GEC/EGC [to the EGC] in the sub I would assume that the EGC protecting the sub panel must be now be properly bonded on both sides of the raceway between the main and the sub if it is ferrous to prevent inductive choking?

Yes. I think the bonding is to ensure electrical continuity, not for reasons related to induction, but the answer is the same.

I suppose if this is done the EGC between the sub and the main now becomes a continuation of the DC GEC/AC EGC and therefore must be irreversibly crimped together in the sub? Did I just answer my own question?

Yes and Yes. Good job. :D
 
Yes.<br>
You generally take the GEC all the way back to the service panel busbar. The EGC running from the sub to the service panel may not be sized large enough. The rules for sizing EGC & GEC are quite different. Table 250.122 calls out the sizing requirements for an EGC. Table 250.66 calls out the sizing requirements for a GEC. Frequently an EGC in a solar installation is a #10 and a GEC is always a minimum of a #8 AWG and must be the same size as the AC conductors.
 

jaggedben

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The GEC for a solar system is actually a DC GEC and is sized according to 250.166. If it is a combined DC GEC and AC EGC, as in this thread, it is the larger of what is specified by 250.166 or 250.122. 250.66 isn't actually mentioned in Art 690. It is still usually a #8 because that's the minimum.
 
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