# Sizing the Grounded Conductor



## Roger123 (Sep 23, 2007)

After reading 250.24(C) & (C)(1) I am a little confused. The section seems to require the use of T250.66 for sizing the grounded conductor, (neutral). T250.66 only list "Grounding Electrode Conductor." Also, 250.28(D) requires using the same table, T250.66 for sizing the main bonding jumpers. Am I interpreting this right?


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## Joe Momma (Jan 23, 2007)

I don't have the energy to research this fully, but the picture in the handbook of .24(C) is talking about bonding before the service, or similar to a 3 wire system.
I may be wrong, and have never had to find this. I have always sized the neut based on the size of the ungrounded conductors.


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## 480sparky (Sep 20, 2007)

Joe Momma said:


> I may be wrong, and have never had to find this. I have always sized the neut based on the size of the ungrounded conductors.


See 220.61.


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## Roger123 (Sep 23, 2007)

480sparky said:


> See 220.61.


480,
Read over the section a couple of times and still a bit confused.

Can you give an example of an installation?


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## raider1 (Jan 22, 2007)

The size of the grounded conductor brought to the service can't be smaller then the size given in Table 250.66 based on the size of the largest ungrounded service entrance conductor. Also the main bonding jumper must be sized from Table 250.66.

This is due to the fact that the main bonding jumper and the grounded service conductor are required to provide a low impeadance path for ground fault current to return to the source (Utility). 

Chris


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## Roger123 (Sep 23, 2007)

raider1 said:


> The size of the grounded conductor brought to the service can't be smaller then the size given in Table 250.66 based on the size of the largest ungrounded service entrance conductor. Also the main bonding jumper must be sized from Table 250.66.
> 
> This is due to the fact that the main bonding jumper and the grounded service conductor are required to provide a low impeadance path for ground fault current to return to the source (Utility).
> 
> Chris


Thanks Chris,

So, an example would be: Phase Conductors are 2/0 copper/grounded conductor can be #4 copper?


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## raider1 (Jan 22, 2007)

Roger123 said:


> Thanks Chris,
> 
> So, an example would be: Phase Conductors are 2/0 copper/grounded conductor can be #4 copper?


Your welcome. 

Yes, the grounded service conductor must be sized no smaller that a #4 copper if the ungrounded service phase conductors are 2/0.

Chris


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## Roger123 (Sep 23, 2007)

Chris,

Thanks for the fast response!

Then, in conclusion T250.66 is used for the GEC/Bonding Conductor & Grounded Conductor? Yes?


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## gilbequick (Oct 6, 2007)

Roger123 said:


> Thanks Chris,
> 
> So, an example would be: Phase Conductors are 2/0 copper/grounded conductor can be #4 copper?


Maybe I read it wrong, but doesn't the grounded conductor have to be 1/0 cu if the service phase conductors are 2/0, cu and the grounding conductor have to be #4 cu?


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## raider1 (Jan 22, 2007)

Roger123 said:


> Chris,
> 
> Thanks for the fast response!
> 
> Then, in conclusion T250.66 is used for the GEC/Bonding Conductor & Grounded Conductor? Yes?


Yes Table 250.66 is used to size the GEC, the main bonding jumper and the minimum size for the grounded service conductor.



> Maybe I read it wrong, but doesn't the grounded conductor have to be 1/0 cu if the service phase conductors are 2/0, cu and the grounding conductor have to be #4 cu?


The grounded service conductor must be sized for the load service but must not be smaller than the required grounding electrode conductor specified in Table 250.66. Take a look at 250.24(C)(1)

Chris


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## kbsparky (Sep 20, 2007)

gilbequick said:


> Maybe I read it wrong, but doesn't the grounded conductor have to be 1/0 cu if the service phase conductors are 2/0, cu and the grounding conductor have to be #4 cu?


While you *can* use a #4 neutral if your load calculations allow it, you don't have to. The _Code_ is a minimum standard and as such using a #1/0 is acceptable, since it's larger than the #4.

The premise here is the neutral can't be smaller than the #4 even if your load calculations only require something like a #10. :blink:


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## Joe Momma (Jan 23, 2007)

Haven't seen you around in a while Raider. You been MIA in the bahamas? or just waiting for a good code question?

Anyhow, good to see you back :thumbup: 




Or perhaps I may even just be blind :whistling2:


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## raider1 (Jan 22, 2007)

Joe Momma said:


> Haven't seen you around in a while Raider. You been MIA in the bahamas? or just waiting for a good code question?
> 
> Anyhow, good to see you back :thumbup:
> 
> ...


I wish I could just disappear in the bahamas for a while. No, I have just been really busy and haven't had a lot of time lately.

Chris


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