Size of GEC 250.66

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sfav8r

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OK, I think I'm confused :confused:

I have always thought that the largest conductor I need for the EGC is #6 as per 250.66(A).

However, the table in 250.66 says that 2/0 service conductors require a #4 EGC.

I realize that 250.66(A) does qualify itself with the statment "the portion of the conductor that is the sole connection to the grounding electrode."

Well, isn't that the definition of an EGC?
 
Re: Size of GEC 250.66

Originally posted by sfav8r:
OK, I think I'm confused :confused:

I have always thought that the largest conductor I need for the EGC is #6 as per 250.66(A).

However, the table in 250.66 says that 2/0 service conductors require a #4 EGC.

I realize that 250.66(A) does qualify itself with the statment "the portion of the conductor that is the sole connection to the grounding electrode."

Well, isn't that the definition of an EGC?
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In other words, if you're not tapping off of the EGC to hit other grounding electrodes that require a larger conductor, then you can run a #6. Or if you're tapping off of a ring and going to a ground rod, you can tap off the ring with a #6.
 
Re: Size of GEC 250.66

I have always thought that the largest conductor I need for the EGC is #6 as per 250.66(A).
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If your hitting a rod, pipe or plate electrode than a #6 is the largest size required to that electrode. However, if the structure had a metal underground water pipe of 10' or more in length than you would be required to size the GEC according to table 250.66.

Using your example the #2/0 would require a #4 cu GEC to the water pipe and would also require one supplemental electrode. If a ground rod were used the conductor to the rod would not be required to be larger than #6 because of 250.66(A). Also a ground rod must have a resistance of 25 ohms or less or it would require one additional ground rod.
 
Re: Size of GEC 250.66

This topic has been licked around for a couple of years now.Some say #6 some say larger.But 250.66 note 2 says to meet the size in 250.66 if no service feeders are installed Roger if I am not mistaken that is what was used In that discussion about Tampa.It took place awhile ago and my mrmory isn`t what it used to be.Doctors have a way of helping that along :roll:
 
Re: Size of GEC 250.66

Originally posted by sfav8r:
I have always thought that the largest conductor I need for the EGC is #6 as per 250.66(A).
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Pickin' nits before bed:
EGC = Equipment Grounding Conductor (250.122)

GEC = Grounding Electrode Conductor (250.66)

Good night! :)
 
Re: Size of GEC 250.66

If your hitting a rod, pipe or plate electrode than a #6 is the largest size required to that electrode. However, if the structure had a metal underground water pipe of 10' or more in length than you would be required to size the GEC according to table 250.66.
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That makes sense, thanks.
 
Re: Size of GEC 250.66

Originally posted by sfav8r:
EGC = Equipment Grounding Conductor (250.122)

GEC = Grounding Electrode Conductor (250.66)
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Yeah, yeah, tell my keyboard that ;)

thanks
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I agrre. I want the computer to do what I want, not what I tell it.

(^perfect example^)

[ October 18, 2005, 07:20 PM: Message edited by: LarryFine ]
 
Re: Size of GEC 250.66

Infinity,
Also a ground rod must have a resistance of 25 ohms or less or it would require one additional ground rod.
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In 250.54 it referes to 250.56's "25 ohms or less" and states it applies to a "single electrode" only and does not apply to the "Supplementary Grounding Electrodes".
 
Re: Size of GEC 250.66

Dave,

Yes, but the ground rod being used to supplement the metal water line is not a 250.54 Supplementary Grounding Electrode. It is, rather, a 250.53(D)(2) Supplemental Electrode, which is required in that section, to comply with 250.56.
 
Re: Size of GEC 250.66

When looking at table 250.66 don?t forget to look under it at these:

(A) Connections to Rod, Pipe, or Plate shall not be required to be larger than 6 AWG copper wire or 4 AWG aluminum wire.

(B) Connections to Concrete-Encased Electrodes. shall not be required to be larger than 4 AWG copper wire.

(C) Connections to Ground Rings. shall not be required to be larger than the conductor used for the ground ring.

Anything else will need to be sized by the table
 
Re: Size of GEC 250.66

So if I understand correctly, a supplemental ground rod required in addition to a water pipe electrode is required to meet the 25 Ohm or 2nd supplemental rod rule.

But a supplementary ground rod is not required to meet the 25 Ohm or 2nd supplementary ground rod rule, and an example of this would be supplementing say building steel or concrete encased electrode?

How many times can one type the word supplement before losing one's mind? :D
 
Re: Size of GEC 250.66

Supplementary Grounding Electrodes are covered under Article 250.54 and nothing to do with Supplemental Grounding Electrodes used to supplement a metal underground water pipe. Look at 250.54.
 
Re: Size of GEC 250.66

Let's just read what it says!
250.54 Supplementary Grounding Electrodes. Supplementary grounding electrodes shall be permitted to be connected to the equipment grounding conductors specified in 250.118 and shall not be required to comply with the electrode bonding requirements of 250.50 or 250.53(C) or the resistance requirements of 250.56, but the earth shall not be used as an effective ground-fault current path as specified in 250.4(A)(5) and 250.4(B)(4).
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Re: Size of GEC 250.66

You're welcome Dave. I used to always confuse the two as well. I've finally beat it into my what the difference actually is.


Trevor
 
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