Which table 250.66 or 250.122 is used for feeder from main panel or disconnect at service entrance to a panel(with breakers) located some where in the building--example: 600 amp service entrance panel(six breakers) with 200 amp breaker(1 phase)with 3/0 cu thhn/thwn conductors to 200 amp panel? Use Table 250.122 is definately used for grounding conductor size from the final (200 amp) panel to the equipment(range or etc.). Table 250.66 is definately used for grounding conductor size for the main panel or disconnect at the service entrance. Thanks
Grounding Conductor size
- Thread starter eutaw42
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hurk27
Senior Member
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- Portage, Indiana NEC: 2008
Re: Grounding Conductor size
Look at the heading of the section the table is in. you will see that table 25.66 is for grounding electrode conductors and table 250.122 is for equipment grounding conductors ether of which can be the one in the same which at the service the grounding conductor is both. so it needs to be size the largest of the two tables. Each section of the NEC will direct you to use the applying table that you should size the grounding conductor on.
Feeders should use table 250.122 as there is OCPD that protect them.
Look at the heading of the section the table is in. you will see that table 25.66 is for grounding electrode conductors and table 250.122 is for equipment grounding conductors ether of which can be the one in the same which at the service the grounding conductor is both. so it needs to be size the largest of the two tables. Each section of the NEC will direct you to use the applying table that you should size the grounding conductor on.
Feeders should use table 250.122 as there is OCPD that protect them.
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