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10-10-2007, 06:20 PM
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#1
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Senior Member
Join Date: Sep 2007
Location: NE Ohio
Posts: 177
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Sizing the Grounded Conductor
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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10-10-2007, 09:11 PM
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#2
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Senior Member
Join Date: Jan 2007
Location: Salt Lake City
Posts: 617
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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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Joe Momma was here 
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10-10-2007, 09:15 PM
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#3
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Seen your member
Join Date: Sep 2007
Location: Cornpatch USA
Posts: 9,975
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Quote:
Originally Posted by Joe Momma
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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See 220.61.
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10-10-2007, 10:35 PM
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#4
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Senior Member
Join Date: Sep 2007
Location: NE Ohio
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Quote:
Originally Posted by 480sparky
See 220.61.
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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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10-11-2007, 11:01 AM
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#5
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Ax grinder
Join Date: Jan 2007
Location: North Logan, Utah
Posts: 679
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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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10-11-2007, 03:30 PM
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#6
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Senior Member
Join Date: Sep 2007
Location: NE Ohio
Posts: 177
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Quote:
Originally Posted by raider1
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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Thanks Chris,
So, an example would be: Phase Conductors are 2/0 copper/grounded conductor can be #4 copper?
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10-11-2007, 03:33 PM
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#7
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Ax grinder
Join Date: Jan 2007
Location: North Logan, Utah
Posts: 679
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Quote:
Originally Posted by Roger123
Thanks Chris,
So, an example would be: Phase Conductors are 2/0 copper/grounded conductor can be #4 copper?
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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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10-11-2007, 03:40 PM
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#8
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Senior Member
Join Date: Sep 2007
Location: NE Ohio
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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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10-11-2007, 05:07 PM
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#9
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Senior Member
Join Date: Oct 2007
Location: NC
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Quote:
Originally Posted by Roger123
Thanks Chris,
So, an example would be: Phase Conductors are 2/0 copper/grounded conductor can be #4 copper?
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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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10-11-2007, 06:34 PM
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#10
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Ax grinder
Join Date: Jan 2007
Location: North Logan, Utah
Posts: 679
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Quote:
Originally Posted by Roger123
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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Yes Table 250.66 is used to size the GEC, the main bonding jumper and the minimum size for the grounded service conductor.
Quote:
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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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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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10-11-2007, 09:10 PM
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#11
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Senior Member
Join Date: Sep 2007
Location: Delmarva, USA
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Quote:
Originally Posted by gilbequick
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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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. 
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10-12-2007, 01:30 AM
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#12
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Senior Member
Join Date: Jan 2007
Location: Salt Lake City
Posts: 617
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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 
Or perhaps I may even just be blind 
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Joe Momma was here
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10-12-2007, 10:08 AM
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#13
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Ax grinder
Join Date: Jan 2007
Location: North Logan, Utah
Posts: 679
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Quote:
Originally Posted by Joe Momma
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
Or perhaps I may even just be blind |
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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