EGC--------Quiz

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I think th language is appropriate!

I think th language is appropriate!

don_resqcapt19 said:
I can see this being read either way. There is no solid code support for either interpretation of the interaction between 250.122(A) and .122(F). Without a code clarification, it is my reading that the sum of all of the conductors in parallel is the circuit conductor for the purposes of the application of 250.122(A).
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IMO it is perfectly clear now... it just requires some close reading.
(For the record-from the posts so far it seems that you and I agree that it has to be full size in accordance with Table 255.122:smile:)
250.122 Size of Equipment Grounding Conductors.
(A) General. Copper, aluminum, or copper-clad aluminum
equipment grounding conductors of the wire type shall not
be smaller than shown in Table 250.122, but in no case
shall they be required to be larger than the circuit conductors
supplying the equipment. Where a cable tray, a raceway,
or a cable armor or sheath is used as the equipment
grounding conductor, as provided in 250.118 and
250.134(A), it shall comply with 250.4(A)(5) or (B)(4).
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(F) Conductors in Parallel. Where conductors are run in
parallel in multiple raceways or cables as permitted in
310.4, the equipment grounding conductors, where used,
shall be run in parallel in each raceway or cable.
Each parallel equipment grounding conductor shall be
sized on the basis of the ampere rating of the overcurrent
device protecting the circuit conductors in the raceway or
cable in accordance with Table 250.122.
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If 250.122(F) was intending for one to comply with the rule in 250.122(A) it would have stated .......in accordance with 250.122(A).

It specifically states ...in accordance with Table 250.122, thus leading me to the conclusion that it is appropriately written.

Take for example 250.122(D) it shoots you back to 250.122(A)....
 
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Dan,
It is not clear because there is nothing that actually says the parallel conductors make up a single conductor. Without something that says that you can read it either way. You can also argue that if you use a 800 kcmil in each raceway, it is larger than the circuit conductors using the same logic that is used to require the 800 kcmil in each raceway. In the case of the 16 sets of 600s you have 6300 kcmil of circuit conductor and 12,000 kcmil of EGC.
 
don_resqcapt19 said:
Dan,
It is not clear because there is nothing that actually says the parallel conductors make up a single conductor. Without something that says that you can read it either way. You can also argue that if you use a 800 kcmil in each raceway, it is larger than the circuit conductors using the same logic that is used to require the 800 kcmil in each raceway. In the case of the 16 sets of 600s you have 6300 kcmil of circuit conductor and 12,000 kcmil of EGC.
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What about 310.4? I mean no disrespect to you,:smile:but you and I both know who the code is intended for:roll: (who is it intended for=Article 90 talks about it and the NEC has even included a definition in Article 100.)

250.122 Size of Equipment Grounding Conductors.
(F) Conductors in Parallel.
Where conductors are run in
parallel in multiple raceways or cables as permitted in
310.4, the equipment grounding conductors, where used,
shall be run in parallel in each raceway or cable.
Each parallel equipment grounding conductor shall be
sized on the basis of the ampere rating of the overcurrent
device protecting the circuit conductors in the raceway or
cable in accordance with Table 250.122.
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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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(E) 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 310.13,
provided the combined circular mil area in each cable complies
with 250.122.
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310.4(E) requires compliance with 250.122....IMO 250.122 accurately addresses this topic, and I think it is sub divided appropriately
 
This has been an interesting post. Just to add fuel to the fire up to now the equipment grounding conductors have been in raceways. Section 250.122 (F) also has cables included. Of note is section 310.4 (E). Sure looks like table 250.122 would limit you to the number of cables you could parallel. A 4/0al ser cable has a 2/0 ground wire. A 2/0 al equipment grounding wire is good for a 600 ampere overcurrent device.
 
Dan,
If I put an 800 kcmil in each of my raceways, then the paralleled EGC is larger than the circuit conductors.
I have going back an forth on this and am leaning on changing my answer. If we are counting all of the phase conductors as a single conductor for the purposes on 250.122(A), then should we not do the same for the EGCs? If that is the case we would only have to install an EGC in each raceway that matches the size of the phase conductors in that raceway.
 
Section 250.122(F) is specific on that the parallel equipment grounding conductor (singular) shall be sized on the basis of the ampere rating of the overcurrent device protecting the circuit conductors. IMO the concept is that if a grounding conductor failed in one set the ground protection would still be there thru the others. Example if you have two sets and one grounding conductor failed the other could provide the full protection for the overcurrent device. IMO the same concept would apply to multiple sets. If a person didn't want to install a grounding conductor larger than the circuit conductors for a 6000 ampere circuit parallel conductors larger than 800 kcm.
 
LarryFine said:
And, if that's the case, what would be the point of the specific paralleled-conductor EGC requirement?
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Larry,
You don't get to a case where the EGC in each raceway of a parallel set would have to be larger than the circuit conductors one of parallel raceways until you have at least 5 runs in parallel, so there is plenty of applications for the rule even if you never have to make the EGC larger than the phase conductors in that raceway.
 
don_resqcapt19 said:
Larry,
You don't get to a case where the EGC in each raceway of a parallel set would have to be larger than the circuit conductors one of parallel raceways until you have at least 5 runs in parallel, so there is plenty of applications for the rule even if you never have to make the EGC larger than the phase conductors in that raceway.
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I'm pretty sure I did it with two runs in parallel. See post #36
 
sandsnow said:
I'm pretty sure I did it with two runs in parallel. See post #36
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You're kind of jumping pages there...that was not because of the use of parallel conductors, it was really because of the combination of the facts that your paralleled conductors are also tap conductors.
 
I am not even sure that there was ever any real technical justification for the rule that requires a full sized EGC in each of the runs of a parallel system. As I recall it was part of the on going cable v conduit market share fights via code rules.
 
Soares Book on Grounding explains it this way:

In the event of a line-to-ground fault in the equipment suppolied by the circuit, the fault current should divide equally between the equipment grounding conductors. However, if a line-to ground fault occurs in the raceway or cable, current will be fed to the fault from both directions. The equipment grounding conductor will thus be called upon to carry the entire amount of fault current until the overcurrent protective device ahead of the fault opens.
 
good stuff!

good stuff!

lauraj said:
Soares Book on Grounding explains it this way:

In the event of a line-to-ground fault in the equipment suppolied by the circuit, the fault current should divide equally between the equipment grounding conductors. However, if a line-to ground fault occurs in the raceway or cable, current will be fed to the fault from both directions. The equipment grounding conductor will thus be called upon to carry the entire amount of fault current until the overcurrent protective device ahead of the fault opens.
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lauraj, if you want a prize you have to answer the quiz:wink::grin:
 
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