Equipment Grounding Conductor Sizing

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HoosierSparky

HoosierSparky

Senior Plans Examiner, MEP
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Scottsdale AZ
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Senior Plans Examiner
When running an EGC from the mounting rails of an array through a combiner panel and controller panel to the MSP can the size of the EGC be reduced? For example, you start with a #6 bare CU at the rails to the 1st J-box, land it there and change to a #8 insulated to the combiner. Can you reduce to a #10 from there to the MSP?
 
HoosierSparky said:
When running an EGC from the mounting rails of an array through a combiner panel and controller panel to the MSP can the size of the EGC be reduced? For example, you start with a #6 bare CU at the rails to the 1st J-box, land it there and change to a #8 insulated to the combiner. Can you reduce to a #10 from there to the MSP?
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The reason you run #6 Cu in the array, is that it is subject to physical damage, and external to a raceway. This is a mechanical size requirement, rather than an electrical size requirement.

Once you are inside of raceways and enclosure, it only needs to be sized to its electrical size requirements, usually following 250.122, if its sole purpose is working as an EGC.
 
This looks like a good place to follow-up with my question. Can that transition from say #6 bare copper to #10 insulated EGC running with the PV Conductors in conduit be made (inside a J-box) using a typical "wire connector" (wire nut)? I've looked in Art. 690 and 250, but can not find any specific requirements of restrictions.

thank you
 
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