Equipment grounding conductors in parallel

[Steelhead]

Can anyone give me a reference in the 2008 NEC where it specifically states that the 1/0 rule doesn't apply when running EGCs in parallel. Is it assumed based on table 250.122? I know the rule but I can't find where it states the exception.

Thanks in advance!

 

[Dennis Alwon]

Can anyone give me a reference in the 2008 NEC where it specifically states that the 1/0 rule doesn't apply when running EGCs in parallel. Is it assumed based on table 250.122? I know the rule but I can't find where it states the exception.

Thanks in advance!

There is no exception for the equipment grounding conductor. Look at 310.4(A) & (B). 250.122(F) for conductors in parallel

 

[Steelhead]

There is no exception for the equipment grounding conductor. Look at 310.4(A) & (B). 250.122(F) for conductors in parallel

Really? I have read that the 1/0 rule doesn't apply to EGCs in quite a few books, even in one of Mike Holt's books. Are all these different authors of these books wrong?

 

[jusme123]

310.4(E) and 250.122 (F)

 

[Dennis Alwon]

Really? I have read that the 1/0 rule doesn't apply to EGCs in quite a few books, even in one of Mike Holt's books. Are all these different authors of these books wrong?

I will not say they are wrong but I do not read it that way. 310.4 states 1/0 with a few exceptions but the equipment grounding conductor in parallel is not one of them. 310.4(B) specifically includes the equipment grounding conductor

 

[iwire]

Can anyone give me a reference in the 2008 NEC where it specifically states that the 1/0 rule doesn't apply when running EGCs in parallel.

Lets start at the beginning, where is the '1/0 rule' found?

In the 2008 NEC it is found in 310.4(A)

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).

Notice it does not include 'equipment grounding conductor' therefore there is no '1/0 rule' for EGCs.

 

[iwire]

I will not say they are wrong but I do not read it that way. 310.4 states 1/0 with a few exceptions but the equipment grounding conductor in parallel is not one of them. 310.4(B) specifically includes the equipment grounding conductor

If EGCs smaller than 1/0 could not be run in parallel that would change almost everything we do. EGCs are almost always in parallel with other EGCs.

 

[jusme123]

There is no exception for the equipment grounding conductor. Look at 310.4(A) & (B). 250.122(F) for conductors in parallel

310.4(A) - has no mention of equipment grounding conductor

 

[Dennis Alwon]

If EGCs smaller than 1/0 could not be run in parallel that would change almost everything we do. EGCs are almost always in parallel with other EGCs.

I didn't mean to imply that EQUIPMENT GROUNDING CONDUCTOR could not be run in parallel. I was under the understanding that the equipment grounding conductor had to be 1/0 or greater.

The last thread we had about this the OP was given the wrong info. I bow to experience

 

[Smart $]

... I was under the understanding that the equipment grounding conductor had to be 1/0 or greater.

... I bow to experience

Well experience teaches us that experience and the Code do not always agree. So your statement amounts to meaningless :happyyes:


While iwire Bob quoted a section in defense of EGC's not required to be 1/0AWG and larger to be run in parallel, let me counter that with...

(5) Equipment Grounding Conductors. Where parallel
equipment grounding conductors are used, they shall be sized
in accordance with 250.122. Sectioned equipment grounding
conductors smaller than 1/0 AWG shall be permitted in multiconductor
cables in accordance with 310.104, provided the
combined circular mil area of the sectioned equipment
grounding conductors in each cable complies with 250.122.

This implies that unless specified as hereinabove, EGC's must be 1/0AWG and larger to be permitted in parallel.

PS: Compliance with 250.122 has no bearing on the matter, as it simply requires EGC's no smaller than listed in Table 250.122, and does not prohibit upsizing the smaller EGC sizes to 1/0AWG for compliance with other sections.

 

[steve66]

I'm not sure everyone is talking about the same thing.

If you are running parallel phase conductors in separate conduits, then you size the EGC in each conduit per table 250.122. That may mean you are putting a #1 ground in each conduit, and those #1 grounds do wind up being in parallel. Nothing wrong with that.

But if you are talking about using smaller conductors in parallel to get an "equivalent" larger conductor that is required by code, then I would say that Smart$ references would probably prohibit that.

Maybe the Steelhead can clarify exactly what situation he is asking about.

 

[Smart $]

...

If you are running parallel phase conductors in separate conduits, then you size the EGC in each conduit per table 250.122. That may mean you are putting a #1 ground in each conduit, and those #1 grounds do wind up being in parallel. Nothing wrong with that.

...

Are you certain of that remark?

 

[petersonra]

Well experience teaches us that experience and the Code do not always agree. So your statement amounts to meaningless :happyyes:


While iwire Bob quoted a section in defense of EGC's not required to be 1/0AWG and larger to be run in parallel, let me counter that with...


This implies that unless specified as hereinabove, EGC's must be 1/0AWG and larger to be permitted in parallel.

PS: Compliance with 250.122 has no bearing on the matter, as it simply requires EGC's no smaller than listed in Table 250.122, and does not prohibit upsizing the smaller EGC sizes to 1/0AWG for compliance with other sections.

in cables the manufacturer is allowed to use sectioned EGCs to make up the EGC as long as they are smaller than 1/0. That does not mean you can extend that to anything other than cables. all it does is prohibit sectioned egcs > 1/0 in cables.

 

[Smart $]

in cables the manufacturer is allowed to use sectioned EGCs to make up the EGC as long as they are smaller than 1/0. That does not mean you can extend that to anything other than cables. all it does is prohibit sectioned egcs > 1/0 in cables.

I would agree with you if that were in an article part titled "Construction".

I am not saying it extends to anything other than a multiconductor cables. What I am saying it is the only section that specifically permits parallel EGC's under 1/0AWG.

All sections regarding parallel conductors say it shall be permitted for 1/0AWG and larger. Simply because the section doesn't include EGC's by name does not mean you can run parallel EGC smaller than 1/0AWG. It actually implies any parallel conductor condition must be permitted.

 

[Dennis Alwon]

I see this is another section that needs clarity. When reading 310.10(H) (1) I believe it is saying that conductors for phase, polarity, neutral, or grounded circuit may be parallel in sizes 1/0 and larger. That could mean that the equipment grounding conductor cannot be paralleled. We know that is not true but if we use that section to determine that the equipment grounding conductor doesn't have to be 1/0 or larger then we must also say we cannot parallel it.

It may be that the equipment grounding conductor was omitted on purpose because 310.10(H)(5) allows smaller sizes with cables.

Now why would cables be allowed to be smaller sizes. It was my opinion that if the cable could not satisfy 250.122 then you couldn't run cable such as is the case with oversizing conductors and using cable such as NM.

 

[Smart $]

I see this is another section that needs clarity. When reading 310.10(H) (1) I believe it is saying that conductors for phase, polarity, neutral, or grounded circuit may be parallel in sizes 1/0 and larger. That could mean that the equipment grounding conductor cannot be paralleled. We know that is not true but if we use that section to determine that the equipment grounding conductor doesn't have to be 1/0 or larger then we must also say we cannot parallel it.

That's correct. 310.10(H)(5) and 250.122(F) are the only sections AFAIK which permit or require parallel EGC's.

It may be that the equipment grounding conductor was omitted on purpose because 310.10(H)(5) allows smaller sizes with cables.

Maybe... maybe not... ???

Now why would cables be allowed to be smaller sizes. It was my opinion that if the cable could not satisfy 250.122 then you couldn't run cable such as is the case with oversizing conductors and using cable such as NM.

The cable mentioned doesn't really have a smaller size EGC. They are just permitted to have sectioned EGC's, which amounts to being paralleled. The combined cmil area still has to be the equivalent size specified by 250.122.

 

[steve66]

Are you certain of that remark?

Yes, 250.122(F) and (F)(1).

And the icing on the cake is 310.4 - "Where equipment grounding conductors are used with conductors in parallel, they shall comply with the requirments of this section except that they shall be sized in accordance with 250.122.

A 600 amp feeder would require a #1 ground. If that feeder was ran as (2) sets of 350KCM in 2 separate conduits, you would need to run a #1 ground wire in each conduit. Nothing requires you to increase that to a 1/0 just because the ground conductors in each raceway wind up in parallel.

It wouldn't make much sense to have to upsize a #1 ground either - each #1 ground is already sized to carry the entire fault current of the 600 amp circuit. No need to worry about how the current will divide between the multiple grounds.

 

[Dennis Alwon]

Yes, 250.122(F) and (F)(1).

And the icing on the cake is 310.4 - "Where equipment grounding conductors are used with conductors in parallel, they shall comply with the requirments of this section except that they shall be sized in accordance with 250.122.

A 600 amp feeder would require a #1 ground. If that feeder was ran as (2) sets of 350KCM in 2 separate conduits, you would need to run a #1 ground wire in each conduit. Nothing requires you to increase that to a 1/0 just because the ground conductors in each raceway wind up in parallel.

It wouldn't make much sense to have to upsize a #1 ground either - each #1 ground is already sized to carry the entire fault current of the 600 amp circuit. No need to worry about how the current will divide between the multiple grounds.

This makes sense to me esp. since we, sort of, parallel equipment grounding conductor's often when running metal conduit and installing an equipment grounding conductor.

 

[qcroanoke]

Yes, 250.122(F) and (F)(1).

And the icing on the cake is 310.4 - "Where equipment grounding conductors are used with conductors in parallel, they shall comply with the requirments of this section except that they shall be sized in accordance with 250.122.

A 600 amp feeder would require a #1 ground. If that feeder was ran as (2) sets of 350KCM in 2 separate conduits, you would need to run a #1 ground wire in each conduit. Nothing requires you to increase that to a 1/0 just because the ground conductors in each raceway wind up in parallel.

It wouldn't make much sense to have to upsize a #1 ground either - each #1 ground is already sized to carry the entire fault current of the 600 amp circuit. No need to worry about how the current will divide between the multiple grounds.

That's the way I see it.

 

[petersonra]

There does not appear to be any requirement that EGCs not be run in parallel or that if run in parallel have to be at least 1/0.

JMNSHO.