Grounding electrode conductor size

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J-R

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What size grounding electrode would be required for a 320a meter base 2 200 a panels?
Underground service lateral 400 kcmil copper to meter base 2 sets of 3/0 copper to 2 200a panels? I've always used 2 copper to water main and jumped unbroken from panel to panel.
Was told today 1/0 would be required don't agree due to 250.66 saying based on service enterance conductors not service lateral conductors which would be 2 x 167800 cir miils and 350 kcmils is 350000 cir mills am I missing something? Thanks for any help
 
IMO, the GEC would need to be a 1/0 if you connected to the grounded conductor in the meter base (the 1/0 would be based on the 400 kcmil laterals), If you elected to connect the GEC to the panels it could be a #4 from each panel to the electrode(s) based on the 3/0, or a #4's tapped to a common GEC, #2 based on the 167800 x 2 (335,600)

grounding2disconnects.jpg
 
The connection to the grounded conductor would be at the panels so the #2 copper should be sized right based on the 3/0 service enterance conductors. I usually will c crimp a piece of #4 in the middle to the #2 and run each end to each panel. Was always curious how others do this connection? Thanks for the help
 
Unless the run of 3/0 AWG is very long, the fault current will correspond to the 350-kcm main service conductors, so IMHO those, rather than the smaller conductors to each panel, would affect the GEC size.
If the GEC size were calculated based on the service disconnect OCPD instead, my answer would be different.
Sort of like Augie's answer, but not quite....

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I think the code is clear on this. The laterals are service conductors so you must size it based on the laterals which would be 1/0 as Gus stated. In our area the power company installs the laterals and they are never larger than the service conductors from the meter to the main disconnect. In that case the #2 would be required.

Interesting to note if you used a meter main panel/meter combo then you would need 1/0 as the grounding electrode conductor not #2.
 
Appreciate the help its been years since I've done an underground service like this where utility didn't supply lateral. was unsure because 250.66 says sized of largest service entrance conductor which in definitions are differenant from lateral or service conductor underground definition
 
J-R said:
Appreciate the help its been years since I've done an underground service like this where utility didn't supply lateral. was unsure because 250.66 says sized of largest service entrance conductor which in definitions are differenant from lateral or service conductor underground definition
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I did not check your math or circular mil accuracy, but I believe you are right in that the service entrance conductors is what it is sized on and in your case it is two 3/0 copper conductors.
 
kwired said:
I did not check your math or circular mil accuracy, but I believe you are right in that the service entrance conductors is what it is sized on and in your case it is two 3/0 copper conductors.
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The largest service conductor is used- service laterals are service conductors
Service Conductors, Underground. The underground conductors
between the service point and the first point of connection
to the service-entrance conductors in a terminal box,
meter, or other enclosure, inside or outside the building wall.
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Dennis Alwon said:
The largest service conductor is used- service laterals are service conductors
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Heading of table 250.66 states "Size of largest ungrounded service-entrance conductor or equivalent area for parallel conductors"

I sometimes question in a case like OP has if we only need to size per just one 3/0 conductor since they are not parallel conductors, to be parallel conductors they need connected together at both ends, though I have always gone with the parallel conductor equivalent anyway.
 
kwired said:
Heading of table 250.66 states "Size of largest ungrounded service-entrance conductor or equivalent area for parallel conductors"

I sometimes question in a case like OP has if we only need to size per just one 3/0 conductor since they are not parallel conductors, to be parallel conductors they need connected together at both ends, though I have always gone with the parallel conductor equivalent anyway.
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In some cases they may be parallel but note 1 is what we have here and there is no mention of parallel. Either way I was not sure what you were saying earlier. It seems like you were saying the service lateral did not have to be used.

1. If multiple sets of service-entrance conductors connect directly to a
service drop, set of overhead service conductors, set of underground
service conductors, or service lateral, the equivalent size of the largest
service-entrance conductor shall be determined by the largest sum of
the areas of the corresponding conductors of each set.
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Dennis Alwon said:
In some cases they may be parallel but note 1 is what we have here and there is no mention of parallel. Either way I was not sure what you were saying earlier. It seems like you were saying the service lateral did not have to be used.
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Ok, note 1 answers my question at the end of my previous post.

The heading on the table still says service entrance conductors, it doesn't mention service drop or lateral conductors or other types of "service conductors"

Note 2 does mention equivalent size of necessary conductor when in a situation where there is no service conductors.
 
Ummm.....yeah I probably came in late on this one and missed it but I gotta ask........What type of grounding electrode are you using?
 
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