What say you? (EGC-----Quiz----Poll)

[ibew441dc]

Poll is based on the following thread.

http://forums.mikeholt.com/showthread.php?t=113880

 

[Dennis Alwon]

Poll is based on the following thread.

http://forums.mikeholt.com/showthread.php?t=113880

I think we need more input-- like the poll.

 

[ibew441dc]

I think we need more input-- like the poll.

What input do you need? Oh....maybe:wink:....answer based on the NEC:grin:

The poll is based on this thread http://forums.mikeholt.com/showthread.php?t=113880 but applies any parallel installation.

 

[nunu161]

Is this a branch circuit or service conductors?

 

[ibew441dc]

Is this a branch circuit or service conductors?

This is an EGC "Equipment Grounding Conductor", so it automatically rules out service conductors.

 

[iwire]

I turn my back on my opinions all the time

Obviously a single man.

 

[Dennis Alwon]

What input do you need?

There was no poll at the top when I first responded.

 

[ibew441dc]

There was no poll at the top when I first responded.

Oh:smile: I probably was editing it or something??

 

[ibew441dc]

Poll Status to Date.

Those who have answered correctly :smile: --------- 33%

Those who have answered incorrectly :roll:-------- 60%

Those who are wayyyyy off ------------------ 6%

 

[Pierre C Belarge]

Poll is based on the following thread.

http://forums.mikeholt.com/showthread.php?t=113880

Poll Status to Date.

Those who have answered correctly :smile: --------- 33%

Those who have answered incorrectly :roll:-------- 60%

Those who are wayyyyy off ------------------ 6%

Be loyal to truth and a reference, not an opinion.....I turn my back on my opinions all the time


The above results are base on your opinion, not necessarily the opinion of all.

It all depends on how to read 250.122(A) & (F), which without a ruling from the NFPA cannot be decided by a handful of people here on the site.






(have you read 250.122(G) - which is a good example of how EGC can be sized accordingly with the ungrounded conductor. And....feeder tap conductor sizing in ratio can be much smaller in size relative to the overcurrent device size)

 

[The Iceman]

Be loyal to truth and a reference, not an opinion.....I turn my back on my opinions all the time


The above results are base on your opinion, not necessarily the opinion of all.

It all depends on how to read 250.122(A) & (F), which without a ruling from the NFPA cannot be decided by a handful of people here on the site.






(have you read 250.122(G) - which is a good example of how EGC can be sized accordingly with the ungrounded conductor. And....feeder tap conductor sizing in ratio can be much smaller in size relative to the overcurrent device size)

Pierre Im not sure what you mean by based on your opinion. 250.122 (F) seems to sum it up. I believe it was charlie b who gave us the charlie b rules of NEC reading. When I went back and read it, and payed attention as though I was reading it for the first time, the NEC seems clear on the issue.

 

[don_resqcapt19]

Poll Status to Date.

Those who have answered correctly :smile: --------- 33%

Those who have answered incorrectly :roll:-------- 60%

Those who are wayyyyy off ------------------ 6%

Short of a Formal Interpretation or a statement from a code making panel published in the ROP or ROC, I don't see how you can say there is a correct answer. The code is not clear on this issue.
As I said in the other thread, if you are summing the total of all of the ungrounded conductors of one phase to say that the EGC in a single raceway is not larger than the circuit conductors, they why don't you use the same process and sum all of the EGCs to say that the EGC is in fact larger than the circuit conductors?

 

[ibew441dc]

True it is my opinion that the NEC is clear on this topic, but.....

True it is my opinion that the NEC is clear on this topic, but.....

Poll is based on the following thread.

http://forums.mikeholt.com/showthread.php?t=113880

Poll Status to Date.

Those who have answered correctly :smile: --------- 33%

Those who have answered incorrectly :roll:-------- 60%

Those who are wayyyyy off ------------------ 6%

Be loyal to truth and a reference, not an opinion.....I turn my back on my opinions all the time


The above results are base on your opinion, not necessarily the opinion of all.

It all depends on how to read 250.122(A) & (F), which without a ruling from the NFPA cannot be decided by a handful of people here on the site.

(have you read 250.122(G) - which is a good example of how EGC can be sized accordingly with the ungrounded conductor. And....feeder tap conductor sizing in ratio can be much smaller in size relative to the overcurrent device size)

The following Reference (not opinion) is copied from the 2005 NEC Handbook.

2005 NEC Handbook Commentary
Where wire-type equipment grounding conductors are installed in multiple raceways or cables used to enclose conductors in parallel, a full-sized equipment grounding conductor selected from Table 250.122 based on the size of the overcurrent device protecting the paralleled circuit is required in each raceway or cable.

The following Reference (not opinion) is copied from the 2008 NEC Handbook.

2008 NEC Handbook Commentary
Where wire-type equipment grounding conductors are installed in multiple raceways or cables used to enclose conductors in parallel, a full-sized equipment grounding conductor selected from Table 250.122 on the basis of the size of the overcurrent device protecting the paralleled circuit is required in each raceway or cable.

The following Reference (not opinion) is copied from NECPLUS.ORG

NECPLUS.org
Staff Note for 250.122(F)

Where conductors are run in parallel raceways or cables as permitted by 310.4, each parallel equipment grounding conductor shall be sized per Table 250.122 based on the size of the overcurrent device protecting the conductors. In other words, the equipment grounding conductor in each raceway or cable must be full-sized, even though the ungrounded (phase) conductors are reduced in size.

Although not formal interpretations all three of the above references are not an opinion from my point of view. Also an important note....All three of the above references were gathered from NFPA resources.

 

[ibew441dc]

Short of a Formal Interpretation or a statement from a code making panel published in the ROP or ROC, I don't see how you can say there is a correct answer. The code is not clear on this issue.
As I said in the other thread, if you are summing the total of all of the ungrounded conductors of one phase to say that the EGC in a single raceway is not larger than the circuit conductors, they why don't you use the same process and sum all of the EGCs to say that the EGC is in fact larger than the circuit conductors?

See commentary in the 2005, 2008, and NECPLUS.org........:roll: Although commentary is not formal interpretations, I would be willing to bet that the code making panel would agree with the commentary in the handbooks and the staff note in necplus.org.

 

[ibew441dc]

Obviously a single man.

Sometimes I wish:wink::grin:

 

[don_resqcapt19]

See commentary in the 2005, 2008, and NECPLUS.org........:roll: Although commentary is not formal interpretations, I would be willing to bet that the code making panel would agree with the commentary in the handbooks and the staff note in necplus.org.

I would no be willing to make that bet as none of the cases address the issue here...where the EGC in a raceway is bigger than the phase conductors in that same raceway. If you are using 500 kcmil, you have to get above 4000 amps for the OCPD before the EGC is larger than 500 kcmil. It is my opinion that it is poor design to parallel when you need to have more than ten sets of conductors.

I stand by my statement that in your example, if you use an EGC sized per T250.122 in each raceway, the EGC is larger than the circuit conductors.
At this point in time there is no right or wrong in this issue...the code is not clear and the handbook or other comments does nothing to change that and neither would a statement from NFPA staff. The only way to get this one correct is to request a FI.

Also the code making panels do not have any input into the handbook. The comments in the hand book or necplus are nothing more than the editor's opinion...no more valid than yours or mine.

 

[Twoskinsoneman]

I voted for the first answer based on the assumption that choice 2:

"according to TABLE 250.122 but not larger than the largest ungrounded conductor in each raceway"

meant not larger than any one conductor and not the equivalent size of the sum of the parallel conductors.

In a case where you are paralleling a large number of conductors (like paralleled 1/0 for a 5000a circuit) it certainly doesn't make sense that you could only use a 1/0 EGC.

250.122(A) says but in no case shall they be required to be larger than the circuit conductors supplying the equipment.

the term circuit conductors does not IMO make it clear enough that it is refering to a single, individual conductor size..... So I use my logic of what makes sense, to deduce it also means the sum of any paralleled conductors.

 

[don_resqcapt19]

...
In a case where you are paralleling a large number of conductors (like paralleled 1/0 for a 5000a circuit) it certainly doesn't make sense that you could only use a 1/0 EGC.

Why doesn't it? The only cable that can feed power into a fault in that raceway are the 1/0 phase conductors. Why can't a 1/0 EGC carry the fault current that is supplied by the 1/0 ungrounded conductor.

 

[ibew441dc]

How do we get a formal interpretation??

How do we get a formal interpretation??

The poll is pretty equal so far(but slightly favored to the first option).....

Regardless of which side of the fence one stands on in this debate.....I think one thing has been made clear, it would be very helpful to have a formal interpretation from the NFPA. I feel that the rule is clear enough now, but almost an equal amount think it is not.

I think most (90% or more) of us who have considered this topic, realize that an installation of this type is rare, but in the event of a correction due to improper sizing there is a lot of money to be lost.

For those who have requested a formal interpretation......How do we go about getting one for 250.122(F)? Also is the process long?

 

[don_resqcapt19]

I understand that a FI takes 6 months or so and the question must be worded so it can be answered with a "yes" or a "no".