Good 'ol 250.66

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inspector23

Senior Member
Location
Temecula, CA
Having a senior moment this morning, my brain has slipped a cog, and I am asking for your help.

I cannot wrap my head around 250.66 (2014).

First it states to use a GEC at the service using table 250.66.
Then 250.66(A) tells me so long as it is the sole connection to a single or multiple ground rods it is only required to be a # 6 copper.

I am thinking about a 3000-amp service. I interpret table 250.66 to mean a 3/0 copper, yet 250.66 seems to tell me I can use a #6 copper?
How can a #6 be sufficient? if it is, why would I need 3/0?

I remember it has read this way for many years, but for the life of me I am lost at the moment.
Do I need more coffee this morning? Send the grandkids home? This makes no sense to me. What am I (obviously) missing?

Thanks in advance for your help!
 

roger

Moderator
Staff member
Location
Fl
Occupation
Retired Electrician
When it comes to a rod, pipe, or plate there is no reason for a larger conductor since they won't do much anyways so 250.66(A) reflects as much. When you go to the other GE's they perform better and warrants a larger sized conductor.

Roger
 

mortimer

third party inspector
Location
New England
Occupation
retired
When it comes to a rod, pipe, or plate there is no reason for a larger conductor since they won't do much anyways so 250.66(A) reflects as much. When you go to the other GE's they perform better and warrants a larger sized conductor.

Roger
such as Water Main.
 
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