Equivalent GEC

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wrobotronic

wrobotronic

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Colorado
Hi all,
So I have just started my inspecting career and have already come by lots of interesting things. My question is this:

An underground service is using 4/0 Al. The EC is using 2 #6 Al conductors for the GEC. I am under the impression that a #2 Al or a #4 Cu or cross sectional equivalent is reqd.

2 #6s is 26.6 sq mm and a #2 is 33.63 sq mm. Is my analysis correct or am I missing something? Be gentle I'm new, lol. Thank you all very much.
 
What do you mean when you say that he's using two #6 Al GEC's are they in parallel?
 
wrobotronic said:
Hi all,
So I have just started my inspecting career and have already come by lots of interesting things. My question is this:

An underground service is using 4/0 Al. The EC is using 2 #6 Al conductors for the GEC. I am under the impression that a #2 Al or a #4 Cu or cross sectional equivalent is reqd.

2 #6s is 26.6 sq mm and a #2 is 33.63 sq mm. Is my analysis correct or am I missing something? Be gentle I'm new, lol. Thank you all very much.
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I have never heard of paralleling the grounding electrode conductor although I don't see anything in the NEC that says you can't. In terms of the mm. sq. That is not what you would use, IMO. When you parallel 2- 3/0 copper conductors it is good for 200 + 200 amps= 400 amps. You don't use cir. mills. If a number 2 al is required then I would think a parallel #6 aluminum would work but they would have to be the exact lengths etc. Also they would have to connect them together somehow where they connect to the electrode.
 
Where in 250.66 does it say that you can make a GEC with two smaller parallel conductors? I see only single conductor sizes in Table 250.66 and no mention of paralleling.
 
infinity said:
Where in 250.66 does it say that you can make a GEC with two smaller parallel conductors? I see only single conductor sizes in Table 250.66 and no mention of paralleling.
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It doesn't say but the code is permissive. I tend to agree with you but it is a bit iffy whether you can or not
 
infinity said:
Where in 250.66 does it say that you can make a GEC with two smaller parallel conductors? I see only single conductor sizes in Table 250.66 and no mention of paralleling.
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It doesn't.

If you use two conductors in parallel, they must both be of the size specified in 250.66.
 
infinity said:
Where in 250.66 does it say that you can make a GEC with two smaller parallel conductors? I see only single conductor sizes in Table 250.66 and no mention of paralleling.
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Hmmm a code change proposal for the 2020 NEC? Interesting this hasn't come up before on this forum
 
Dennis Alwon said:
It doesn't say but the code is permissive. I tend to agree with you but it is a bit iffy whether you can or not
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I don't see it as falling under the permissive nature of the code. 250.66 says "The size of the grounding electrode conductor.......shall not be less than given in Table 250.66." The table gives us the wire size to use.
 
ActionDave said:
I don't see it as falling under the permissive nature of the code. 250.66 says "The size of the grounding electrode conductor.......shall not be less than given in Table 250.66." The table gives us the wire size to use.
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I tend to agree and I would never do such an install however this is similar to the old table in 310.15(B)(7) where parallel install were not stated in the table but in general they would be accepted. That was cleared up, IMO in 2014
 
I would think if you allow it than 310.4 would come into play and I would not allow two # 6 AWG to make up a single conductor

310.4 Conductors in Parallel.
(A) General. Aluminum, copper-clad aluminum, or copper conductors of size 1/0 AWG and larger, comprising each phase, polarity, neutral, or grounded circuit conductor shall be permitted to be connected in parallel (electrically joined at both ends).
 
david said:
I would think if you allow it than 310.4 would come into play and I would not allow two # 6 AWG to make up a single conductor

310.4 Conductors in Parallel.
(A) General. Aluminum, copper-clad aluminum, or copper conductors of size 1/0 AWG and larger, comprising each phase, polarity, neutral, or grounded circuit conductor shall be permitted to be connected in parallel (electrically joined at both ends).
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Where does this state the grounding electrode conductor cannot be paralleled. It states grounded circuit conductor-- no equipment grounding conductor nor grounding electrode conductor
 
Dennis Alwon said:
Where does this state the grounding electrode conductor cannot be paralleled. It states grounded circuit conductor-- no equipment grounding conductor nor grounding electrode conductor
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I'm not taking issue with paralleling I would think if you cannot parallel smaller that 1/0 every where else why would you be allowed to parallel smaller than 1/0 grounding electrode conductors.
 
lacking guidance in the code on how( what size) allowed to be paralleled and you wanted to parallel two #6 I tell you to get an engineer to approve it first
 
wrobotronic said:
Hi all,
So I have just started my inspecting career and have already come by lots of interesting things. My question is this:

An underground service is using 4/0 Al. The EC is using 2 #6 Al conductors for the GEC. I am under the impression that a #2 Al or a #4 Cu or cross sectional equivalent is reqd.

2 #6s is 26.6 sq mm and a #2 is 33.63 sq mm. Is my analysis correct or am I missing something? Be gentle I'm new, lol. Thank you all very much.
Click to expand...

what are the two # 6 Al. Being connected to?
 
infinity said:
GEC's are not covered under 310.4(A).
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Every where the NEC allows conductors to be paralleled it also gives guidance on how to size the paralleled conductors. There is no guidance given in article 250 in sizing paralleled grounding electrode conductors.

Any time you step outside of the prescriptive nature of the code and compliance cannot be determined, an electrical inspector has every right to ask for a design by an electrical engineer.
 
Smart $ said:
They do have that right...

...but even electrical engineer designs cannot supercede Code.
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I know and I would suspect that an electrical engineer would call out a single conductor sized in accordance with 250.66 rather than paralleling two #6 Al.

I think we need to wait and see what these conductors are connected to before we debate paralleling GEC
 
wrobotronic said:
Hi all,
So I have just started my inspecting career and have already come by lots of interesting things. My question is this:

An underground service is using 4/0 Al. The EC is using 2 #6 Al conductors for the GEC. I am under the impression that a #2 Al or a #4 Cu or cross sectional equivalent is reqd.

2 #6s is 26.6 sq mm and a #2 is 33.63 sq mm. Is my analysis correct or am I missing something? Be gentle I'm new, lol. Thank you all very much.
Click to expand...

Parallel underground service conductors are joined together at each end of the lateral -- this creates a single circuit -- combined circular mills of each parallel run determine electrode conductor size -- parallel conductors specified in 310.15(H)(1) & (5) which include bonding jumpers -- 250.122(F) will mandate EGC to be a singlular sized conductor per OCPD which can be fed with parallel feeders that combine circuilar mills are adequate for the circuit -- table 250.66 ditinguishes the difference in largest service conductor and parallel conductors, in which the electrod size is referred as conductor(indicating singular) -- 250.64(D)(2) also indicates a singular conductor -- I tend to go with the electrode conductor is a singular type conductor & not to be paralleled.
 
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