Quote Originally Posted by codequestion View Post
Just curious how so GEC size change if brining anothwr set of service conductors? Any article NEC 2014.

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See table 250.66 note 1. So say you have 250 MCM AL service entrance conductor. You have a #4 existing CU GEC (and bonding jumpers if applicable). If you add another set of service entrance conductors per one of the exceptions in 230.40, say the new set is 350 AL MCM, now your total area used to size the GEC (and bonding jumpers) is 600 MCM which requires a 1/0 Cu GEC. You can still use the GEC tap method in 250.60(D)(1) to size the tap for the 350 set, but the Common GEC would need to be sized for 600 effective area.

If you have a second SERVICE and not a second set of service entrance conductors, then I dont think 250.66 note 1 applies, so can a GEC or bonding jumper Serve BOTH services at the same time and only be sized for the largest service? I am not sure, maybe others will offer an opinion.