sizing the grounding electrode conductor

[Dan67]

OK. The grounding electrode conductor must be sized based on the largest service-entrance conductor or equivalent area for parallel conductors in accordance with table 250.66.

What exactly does largest service-entrance conductor mean? Say for instance I had a small apartment house. It is getting two identical 100A panels installed in the basement side by side. #2 size ALU. SE cables for each panel. There is water pipe available for grounding electrode. The way I have been proceeding is to add the cir. mils. of two #2 ALU. The sum of these is the largest service-entrance conductor. So I would end up a #6 copper being barely big enough.

I have also heard the people argue that one #2 is the largest service-entrance conductor. In this instance a #6 cop would work either way you look at it.

 

[Dennis Alwon]

Dan are there 2 meters feeding these 2 100 amp panels on this building? If so each one would need electrode hookup based on the #2.

 

[Dan67]

Dan are there 2 meters feeding these 2 100 amp panels on this building? If so each one would need electrode hookup based on the #2.

Yes there are two meters.

 

[Dennis Alwon]

If you had multiply sets of service entrance cables coming from one meter to 2 panels , as in the case of a 400 amp service with 2- 200 amp panels, then you would sum the conductors to size the GEC. If you use an all in one meter panel combo where there are no service conductors then you must use t. 310.16 to find a conductor that would work for the service size. Then you would use T. 250.66

 

[Dan67]

What if there were only one meter? Then what would say?

 

[Dennis Alwon]

What if there were only one meter? Then what would say?

Did you read my post above yours? Read it and see if it helps.

 

[Dan67]

If you had multiply sets of service entrance cables coming from one meter to 2 panels , as in the case of a 400 amp service with 2- 200 amp panels, then you would sum the conductors to size the GEC. If you use an all in one meter panel combo where there are no service conductors then you must use t. 310.16 to find a conductor that would work for the service size. Then you would use T. 250.66

Staying with these two 100A panels with there own meters, what if I used an irreversable crimp splice somewhere close to the panels, then ran one #6 to the water pipe?

 

[Dennis Alwon]

Staying with these two 100A panels with there own meters, what if I used an irreversable crimp splice somewhere close to the panels, then ran one #6 to the water pipe?

I believe that is legal. I also think if you ran one #6 to one panel then you only need a split bolt to connect to the #6. You would not need an irreversible connection.

 

[Dan67]

I believe that is legal. I also think if you ran one #6 to one panel then you only need a split bolt to connect to the #6. You would not need an irreversible connection.

How about making the splice in one of the panel's terminal bars?

 

[Dennis Alwon]

How about making the splice in one of the panel's terminal bars?

I think you can tie the GEC right onto the other panels bar without a splice.

 

[Dan67]

Thanks for your input. Later.