Can you Parallel the ground on a single conduit???

[brother]

I was talking with another guy about the 'grounding being sized on the overcurrent device for the motors per NEC 250.122 (D)(1,2). The breaker is 70 amp. Instead of pulling a #8 copper based on table 250.122, it had an existing #10. He decided to pull in an ADDITIONAL #10 ground to help compensate for the size. This is one conduit, not parallel conduits.

Is it legal to do that?? It's my understanding it is not. You would have to size the single ground off of the overcurrent device, and not try to parallel them. Only thing I could find in the code was NEC 2008 250.122(F). But that even says that if you had parallel conduits then each ground pulled in each conduit would have to be sized to the over current device.

In theory I suppose if there is a fault, it would work. I know the NEC is suppose to be a permissive document, but I interpet this to not be permited.

 

[iwire]

How many forums do you ask the same question in? :grin:


Look at T250.122 do you see anything that allows what you describe?

Your reference to (F) is right on the money

 

[brother]

How many forums do you ask the same question in? :grin:


Look at T250.122 do you see anything that allows what you describe?

Your reference to (F) is right on the money

No, I did not see anything thats says its 'ok' to do that. But like I said, the NEC is a 'permissive' document, so in general, if it does not say you 'can not do this' then it can be allowed.

How many forums do you 'answer' the same question in?? You sound like a 2 timming forum surfer!!

 

[tom baker]

The NEC does not allow conductors smaller than 1/0 to be in parallel.

 

[Jim W in Tampa]

The NEC does not allow conductors smaller than 1/0 to be in parallel.

exactly and that is all conductors.

 

[Nium]

Except for 620.12(A)(1)

 

[charlie b]

. . . the NEC is a 'permissive' document, so in general, if it does not say you 'can not do this' then it can be allowed.

And where in the code does it say that? :grin:

I think we need to be careful in applying that commonly held belief. Specifically, if the code explicitly says, "it shall be permissible to do A, B, and C," then I think it is, at the same time, explicitly forbidding us to do "D." In this case, 310.4 explicitly says "it shall be permitted" to parallel each "phase, polarity, neutral, or grounded" conductor. I interpret the fact that the EGC is not included in this list as an explicit declaration that the EGC shall not be paralleled.

 

[Cold Fusion]

In this case, 310.4 explicitly says "it shall be permitted" to parallel each "phase, polarity, neutral, or grounded" conductor. I interpret the fact that the EGC is not included in this list as an explicit declaration that the EGC shall not be paralleled.

charlie -
You completely lost me on this reasoning. (2008) 310.4.E specifically discusses "parallel equipment grounding conductors"

As for 310.4.A, "I interpret the fact that the EGC is not included in this list as an explicit declaration that the EGC" is excluded fron the 1/0 parallel limitation imposed on the other types of conductors.

cf

 

[iwire]

We end up with parallel EGCs all the time of all sizes, there is no NEC violation there.

What we can not do is use two or more EGCs in parallel to make up for a single undersized EGC.

 

[charlie b]

You completely lost me on this reasoning. (2008) 310.4.E specifically discusses "parallel equipment grounding conductors"

And it says that they must be sized per 250.122. That means that each must be sized per 250.122. That echoes the statement in 300.3(B)(1) that requires each parallel EGC to be full sized. What I meant, and how I interpreted 310.4(A), is that you can?t use two smaller EGCs in parallel to equal the minimum required size of the EGC.

As for 310.4.A, "I interpret the fact that the EGC is not included in this list as an explicit declaration that the EGC" is excluded from the 1/0 parallel limitation imposed on the other types of conductors.

That article says you can parallel some wires that are 1/0 or larger. You can?t go from there to saying that you can parallel a smaller wire, if it is not on the list. In fact, it does have an exception that allows smaller than 1/0 to be in parallel, and the exception does not speak of EGCs.

 

[don_resqcapt19]

And where in the code does it say that? :grin:

I think we need to be careful in applying that commonly held belief. Specifically, if the code explicitly says, "it shall be permissible to do A, B, and C," then I think it is, at the same time, explicitly forbidding us to do "D." In this case, 310.4 explicitly says "it shall be permitted" to parallel each "phase, polarity, neutral, or grounded" conductor. I interpret the fact that the EGC is not included in this list as an explicit declaration that the EGC shall not be paralleled.

There is no way, using the English language, that you can come to the conclusion that the words "shall be permitted" can be read as prohibiting anything. The NEC style manual says that these words are to be used like an exception to permit an alternate installation method. The problem is that there is no rule in the current NEC that prohibits the paralleling of conductors and therefore no rule for the words "shall be permitted" to act as an exception to. This code section does not say what the CMP intends it to say. This should be corrected in the 2014 code with wording that will specifically prohibit the paralleling of conductors smaller than 1/0. (proposal 6-16)

 

[Cold Fusion]

We end up with parallel EGCs all the time of all sizes, there is no NEC violation there.

What we can not do is use two or more EGCs in parallel to make up for a single undersized EGC.

I agree with both statements.

...That article (310.4.A - cf) says you can parallel some wires that are 1/0 or larger. You can?t go from there to saying that you can parallel a smaller wire, if it is not on the list. In fact, it does have an exception that allows smaller than 1/0 to be in parallel, and the exception does not speak of EGCs.

Sure I can for EGCs anyway. Following what bob said:

310.4.A discusses paralleling current carrying conductors and limits the paralleling to 1/0 or larger.

310.4.E discusses paralleling EGCs. There is no mention of any 1/0 limitation on size.

Here is an example:

500A CB feeding paralleled 250kcmil in separate raceways. 250.122 requires a #2 in each raceway for the EGC. I'm pretty sure this is what bob was talking about in his first statement. No violation I can see.

cf

 

[infinity]

I agree with both statements.


Sure I can for EGCs anyway. Following what bob said:

310.4.A discusses paralleling current carrying conductors and limits the paralleling to 1/0 or larger.

310.4.E discusses paralleling EGCs. There is no mention of any 1/0 limitation on size.

Here is an example:

500A CB feeding paralleled 250kcmil in separate raceways. 250.122 requires a #2 in each raceway for the EGC. I'm pretty sure this is what bob was talking about in his first statement. No violation I can see.

cf

I agree, but would you be permitted to use parallel #4's in each raceway to equal a #2?

 

[Cold Fusion]

I agree, but would you be permitted to use parallel #4's in each raceway to equal a #2?

I'm thinking you read 250.122.F the same way I do. So, not that I can tell.

cf

 

[Cavie]

How many forums do you ask the same question in? :grin:

Some people don't know that you can click on "Today's Posts" and not have to go the all the forums. There should be a few reminders of that.

 

[charlie b]

Some people don't know that you can click on "Today's Posts" and not have to go the all the forums.

I think the question was discussing Internet sites other than Mike Holt's NEC Forum, not various topic areas within the Mike Holt NEC Forum. We do not allow discussing the same issue in more than one thread at a time. Duplicates get quickly closed here.

 

[iwire]

I think the question was discussing Internet sites other than Mike Holt's NEC Forum,

You are correct.

 

[iwire]

Back on topic.

Picture a typical wood framed home, I run a 12/2 and a 14/2 NM from the panel to a two gang box in the kitchen, the 12/2 supplies the SABC and the 14/2 supplies the lighting, all the EGCs in this box must be connected together (250.148) so that will put a 14 and 12 AWG copper EGC in parallel. This is common and not a violation.

 

[raider1]

Back on topic.

Picture a typical wood framed home, I run a 12/2 and a 14/2 NM from the panel to a two gang box in the kitchen, the 12/2 supplies the SABC and the 14/2 supplies the lighting, all the EGCs in this box must be connected together (250.148) so that will put a 14 and 12 AWG copper EGC in parallel. This is common and not a violation.

I agree.

Chris

 

[Cold Fusion]

Back on topic.

Picture a typical wood framed home, I run a 12/2 and a 14/2 NM from the panel to a two gang box in the kitchen, the 12/2 supplies the SABC and the 14/2 supplies the lighting, all the EGCs in this box must be connected together (250.148) so that will put a 14 and 12 AWG copper EGC in parallel. This is common and not a violation.

I can freely admit that scenerio would have eluded me.

cf