Am figuring a 400' underground run for a sub panel to be set in a camp area(RV use). I've got my conductors figured for the 100A load but not sure what to size the GEC to. 120/240V single phase, would a #6 AL be the proper size? These will be direct burial AL conductors. Thanks. BTW, 2/0 AL is my hot and neutral conductor size.
GEC
- Thread starter nizak
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- Chapel Hill, NC
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- Retired Electrical Contractor
GEC or EGC?
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- Chapel Hill, NC
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- Retired Electrical Contractor
250.122(B) will require you to upsize the egc proportionately to the ungrounded conductors.
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- Chapel Hill, NC
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- Retired Electrical Contractor
If you mean GEC then that is based on the wire size to the building
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- Chapel Hill, NC
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- Retired Electrical Contractor
Wow , I wonder how many posts I can get out of this thread. 
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- Chapel Hill, NC
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- Retired Electrical Contractor
IMO, you need a #4 aluminum for the egc.
#1 is what is needed for 100 amps using aluminum USE cable (75C). According to chapter 9 Table 8 that is 83690 cir. mils. You used 2/0 @ 133100 cir. mil. The 2/0 is 1.59 times larger so.....
The NEC require a #6 aluminum for 100 amps-- 26240 cir. mil Multiply that by 1.59 and you get 41722 which is equivalent to a #4 alum.
#1 is what is needed for 100 amps using aluminum USE cable (75C). According to chapter 9 Table 8 that is 83690 cir. mils. You used 2/0 @ 133100 cir. mil. The 2/0 is 1.59 times larger so.....
The NEC require a #6 aluminum for 100 amps-- 26240 cir. mil Multiply that by 1.59 and you get 41722 which is equivalent to a #4 alum.
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