Plan Review, EGC Size

[infinity]

I was reviewing some engineered plans the other day and found numerous notations for conduit runs containing this information (3/4 EMT, 3-#10, 1-#12 ground). I first thought that I would just make a blanket statement that if the circuit conductors are #10 then the EGC must always be #10. Is there a scenario when this wouldn't be true?

 

[roger]

Rob, AFAIK your first thought is correct.

Roger

 

[augie47]

Likewise, I know of no valid reason.

 

[infinity]

Thanks, before I present this as an always scenario (3-#10, #10 EGC) I wanted a few other opinions. :happyyes:

 

[fmtjfw]

Depending on the conduit material EGCs may not be needed.

 

[Smart $]

Thanks, before I present this as an always scenario (3-#10, #10 EGC) I wanted a few other opinions. :happyyes:

Depends on your interpretation of "increased in size" under 250.122(B).

If the conditions of use for a circuit having a 20A ocpd warrant a minimum #10 conductor, is that "increased in size"? (And yes I realize it has been discussed here many times without conclusive resolution)

 

[infinity]

Depends on your interpretation of "increased in size" under 250.122(B).

If the conditions of use for a circuit having a 20A ocpd warrant a minimum #10 conductor, is that "increased in size"? (And yes I realize it has been discussed here many times without conclusive resolution)

Yes that would be another thread on it's own.

 

[taylorp]

Depends on your interpretation of "increased in size" under 250.122(B).

If the conditions of use for a circuit having a 20A ocpd warrant a minimum #10 conductor, is that "increased in size"? (And yes I realize it has been discussed here many times without conclusive resolution)

Please, please, no more discussions on 250.122(B).

Half of the discussors do not know what the Code means and the other half are sure they do!:lol:

 

[Smart $]

Please, please, no more discussions on 250.122(B).

I had to self-debate whether or not to even bring it up... but the proposition of an always statement demanded that someone bring it up :blink::roll:

Half of the discussors do not know what the Code means and the other half are sure they do!:lol:

And half of the half that are sure they do, do not.

 

[jusme123]

Likewise, I know of no valid reason.

.................

 

[infinity]

Please, please, no more discussions on 250.122(B).

Half of the discussors do not know what the Code means and the other half are sure they do!:lol:

Lets hope the 2014 NEC clears 250.122(B) all up. :roll:

 

[fmtjfw]

2014 **DRAFT** 250.122(B)

2014 **DRAFT** 250.122(B)

Lets hope the 2014 NEC clears 250.122(B) all up. :roll:

It currently reads (no pun intended):

2011:

250.122 Size of Equipment Grounding Conductors.
(B) Increased in Size. Where ungrounded conductors are increased in size, equipment grounding conductors, where installed, shall be increased in size proportionately according to the circular mil area of the ungrounded conductors.

2014:

250.122 Size of Equipment Grounding Conductors.
(B) Increased in Size. Where ungrounded conductors are increased in size from the minimum size that has sufficient ampacity for the intended installation, wire type equipment grounding conductors, where installed, shall be increased in size proportionately according to the circular mil area of the ungrounded conductors.[ROP 5?199]

I think the new version is almost impossible to read, but I haven't figured out how to fix it (yet).

This has ROP 5-199 attached to it, so you can try to fix it with a comment submission.

 

[Smart $]

It currently reads (no pun intended):

2011:

250.122 Size of Equipment Grounding Conductors.
(B) Increased in Size. Where ungrounded conductors are increased in size, equipment grounding conductors, where installed, shall be increased in size proportionately according to the circular mil area of the ungrounded conductors.

2014:

250.122 Size of Equipment Grounding Conductors.
(B) Increased in Size. Where ungrounded conductors are increased in size from the minimum size that has sufficient ampacity for the intended installation, wire type equipment grounding conductors, where installed, shall be increased in size proportionately according to the circular mil area of the ungrounded conductors.[ROP 5–199]

I think the new version is almost impossible to read, but I haven't figured out how to fix it (yet).

This has ROP 5-199 attached to it, so you can try to fix it with a comment submission.

Not up to making a comment submission myself. However, here's a rewording proposal (feel free to submit if you want)...

250.122 Size of Equipment Grounding Conductors.
(B) Increased in Size. Where ungrounded conductor size is greater than the minimum size permitted for the conditions of use, any associated wire-type equipment grounding conductor shall be increased in size proportionate to the increase in the ungrounded conductor.


Informational Note: Increase in size by the difference in AWG number meets this proportional requirement. For this purpose, sizes 1/0, 2/0, 3/0, and 4/0 AWG shall be considered 0, -1, -2, and -3, respectively. Where ungrounded conductor size is given only by circular mils, the calculated result for minimum equipment grounding conductor size may be rounded down to three significant figures.

The real question here is whether to add to the main requirement or add to the informational note regarding the increasing of size to compensate for voltage drop...???

 

[cowboyjwc]

Table 250.122 says you are correct. Assuming that the #10's are for a 30 amp circuit.

 

[steve66]

Lets hope the 2014 NEC clears 250.122(B) all up. :roll:

Not that I want to restart something, but I don't see the problem with the current wording.

#12 is allowed for a 20 amp circuit. Anything larger would be an increase in size, and would therefore require a larger ground.

 

[charlie b]

I first thought that I would just make a blanket statement that if the circuit conductors are #10 then the EGC must always be #10.

I also cannot think of a scenario in which #10 conductors can be matched with a #12 EGC. But I will add a minor quibble: They don't always have to be #10. They always have to be at least #10.

 

[infinity]

I also cannot think of a scenario in which #10 conductors can be matched with a #12 EGC. But I will add a minor quibble: They don't always have to be #10. They always have to be at least #10.

Yes, I should have thrown the word minimum in there.

 

[bob]

Not that I want to restart something, but I don't see the problem with the current wording.

#12 is allowed for a 20 amp circuit. Anything larger would be an increase in size, and would therefore require a larger ground.

That is what the code requires but the question is why. If the #12 gnd is good for the #12 ckt, why is it not good if the conductor is changed to #10? The gnd
is supposed to have low enough impedance to ensure the breaker trip when a fault occurs. That has not changed.

 

[bob]

changed my mind.

 

[CONDUIT]

You stated a # 12 ground. Are they for sure talking about the grounding conductor or is it a grounded conductor.
Just curious. As some have already stated that the emt could possibly be used for the equipment ground.
If it is a grounded conductor it is possible that it could be sized smaller based on the unbalanced load. Do not know what the circuit is being used for?