Sizing EGC's.

[chris kennedy]

Why are we sizing EGC's the same for a circuits with an available fault current of 65ka and 10ka? Worst case scenario figured into 250.122?

Thanks.

 

[skeshesh]

No. Note that the size indicated in the table is the minimum required. For typical installations the table works fine but there are cases where available fault current should be considered. Here's a good read: http://www.cooperbussmann.com/library/techspec/TechSpec19_sup.pdf

Also, we had a short discussion on this subject a couple of months ago:
http://forums.mikeholt.com/showthre...re-sizing-above-NEC-recommendation?highlight=

 

[chris kennedy]

Very interesting indeed, thanks.

 

[tom baker]

Take a look at this article about GEMI.
http://www.steelconduit.org/pdf/gemi_study.pdf
Gemi developed into a software program to calculate the size of the EGC for the type of raceway with or wo supplemential EGC, etc.
Its a free download but I can't find the link to it, it may be on Mikes site.