# Thread: Grounding electrode conductor size

1. Member
Join Date
Oct 2004
Posts
50

## Grounding electrode conductor size

I have been asked to check a ground electrode conductor size. From the utility, there are parallel 3/0 conductors to the MCC. (Two 3/0 per phase, Two parallel conduits, each with the 3 phases and a #4 ground)
The two #4 grounds from the utility terminate on the MCC ground buss. So far so good. Now, the grounding electrode conductor from the MCC to the ground electrode (the customers ground electrode) is one #2 conductor. From table 250.66 it appears that the grounding electrode conductor should be two #4's. Am I right?

Thanks for any help

2. You must look at Note 1

3. You do not parallel the grounding electrode conductor. Note 1 states to add the cir. mil of the 3/0 conductors. Table 8 Chapter 9 shows the cir mil for 3/0 at 167,800. Multiple by 2 for the parallel run and you get 335,600-- closest size to that is 350 kcm. Thus you need a 1/0 copper grounding electrode conductor

4. Member
Join Date
Oct 2004
Posts
50
Just read it again. ..if I understand it right, it means the ground electrode conductor is sized for the sum of the two 3/0 service conductors...but I'm not sure.

5. Originally Posted by ktm400sx
Just read it again. ..if I understand it right, it means the ground electrode conductor is sized for the sum of the two 3/0 service conductors...but I'm not sure.

6. Member
Join Date
Oct 2004
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50
Originally Posted by Dennis Alwon
Ah, just saw that...thank you Dennis

7. Originally Posted by ktm400sx
Ah, just saw that...thank you Dennis
You're welcome....

8. What type of customer electrode is it? A CEE would only require a #4 GEC.

9. Originally Posted by infinity
What type of customer electrode is it? A CEE would only require a #4 GEC.
Good point..Since the op mentioned #2 then perhaps it is connected to a ground ring.

10. Member
Join Date
Oct 2004
Posts
50
It is a driven steel electrode, I don't know how long..

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