2014 nec code to 250.122

[yankeeman411]

having trouble figuring out the wording to 250.122b. correct me if i'm wrong, if I have 6 circuits in a 3/4 pipe all 20 amps, i need to derate them to a 10awg. Can my ground remain the 12 awg or does that have to be upsized as well.

 

[iwire]

You will have to make the EGC #10 as well or just don't pull one and use the pipe as the EGC.

 

[infinity]

As Bob stated they need to be up-sized as well to the same size as the 20 amp circuit conductors so if you decided that you needed #8 circuit conductors the EGC would need to be a #8 also.

 

[yankeeman411]

Found this on another site, what do you guys think



Equipment grounding conductors are selected from Table 250.122 based on the size of the overcurrent device protecting the circuit. If the ungrounded conductors of the circuit are increased to allow for voltage drop, or because of manufacturer?s instructions, the equipment grounding conductor must be increased in size by the same proportion that the ungrounded conductors have been increased. For example, if the size of the ungrounded conductors is increased by 25%, the size of the equipment grounding conductor must be increased by 25%.
The language in the 2011 NEC was not clear about why the ungrounded conductors would be increased in size. Ungrounded conductors are often increased in size because when more than 3 current-carrying conductors are in conduit, or used in a hot ambient temperature, the conductor cannot perform at the same ampacity. The intent of this section was not to require an increase in the size of the equipment grounding conductor under these conditions of use for the ungrounded conductors.
The 2014 NEC clears this up by saying the equipment grounding conductor needs to be increased in size only if the ungrounded conductors are increased in size beyond what is needed for the ?sufficient ampacity for the intended installation.? In other words, if the ungrounded conductors are increased in size because there are more than 3 current-carrying conductors in conduit, or the ambient temperature is above 86?F, the equipment grounding conductor is not required to be increased in size.
In the 2011 NEC there was also confusion about what to do if the equipment grounding conductor was a metallic raceway. Was it necessary to increase the size of the raceway if the ungrounded conductors were increased in size? This was never intended, and the 2014 refers to ?wire-type? equipment grounding conductors as the only type of equipment grounding conductor that needs to be increased in size.

 

[infinity]

Found this on another site, what do you guys think



Equipment grounding conductors are selected from Table 250.122 based on the size of the overcurrent device protecting the circuit. If the ungrounded conductors of the circuit are increased to allow for voltage drop, or because of manufacturer?s instructions, the equipment grounding conductor must be increased in size by the same proportion that the ungrounded conductors have been increased. For example, if the size of the ungrounded conductors is increased by 25%, the size of the equipment grounding conductor must be increased by 25%.
The language in the 2011 NEC was not clear about why the ungrounded conductors would be increased in size. Ungrounded conductors are often increased in size because when more than 3 current-carrying conductors are in conduit, or used in a hot ambient temperature, the conductor cannot perform at the same ampacity. The intent of this section was not to require an increase in the size of the equipment grounding conductor under these conditions of use for the ungrounded conductors.
The 2014 NEC clears this up by saying the equipment grounding conductor needs to be increased in size only if the ungrounded conductors are increased in size beyond what is needed for the ?sufficient ampacity for the intended installation.? In other words, if the ungrounded conductors are increased in size because there are more than 3 current-carrying conductors in conduit, or the ambient temperature is above 86?F, the equipment grounding conductor is not required to be increased in size.
In the 2011 NEC there was also confusion about what to do if the equipment grounding conductor was a metallic raceway. Was it necessary to increase the size of the raceway if the ungrounded conductors were increased in size? This was never intended, and the 2014 refers to ?wire-type? equipment grounding conductors as the only type of equipment grounding conductor that needs to be increased in size.

I disagree with the bold section and any change from 2011 to 2014 had no bearing on the proportional increase requirement.

 

[Smart $]

I'll weigh in as disagreeing with Rob and Bob.

This is the exact reason the wording was changed in 2014...

If the #10's are "the minimum size [ungrounded conductor] that has sufficient ampacity for the intended installation", the EGC is not required to be upsized.

 

[don_resqcapt19]

So just because we had to upsize the ungrounded conductors because of high ambient temperature or more than 3 conductors, that upsized ungrounded conductor can't carry as much fault current than the same size conductor that was not upsized for high ambient or more than 3 conductors in a cable or raceway

 

[yankeeman411]

That code needs some work. What if i have 4 ccc and i use 10s for everything then 2 circuits dump off, so now i have no need to derate. I can go back to the 12s?? Now i have 10s spliced to 12s?

 

[iwire]

I'll weigh in as disagreeing with Rob and Bob.

Now that you made me cry I will have to agree with you based on the 2014 NEC.

 

[Smart $]

Now that you made me cry I will have to agree with you based on the 2014 NEC.

Whoever this is, whatever you did to Bob, I'll be waiting for him to check in again this morning. If I suspect it is not Bob himself, I'm calling the AHJ....

 

[iwire]

Twice in as many days I have had to change my opinion and agree with you.


I am concerned for the future. hmy:

 

[yankeeman411]

So is the verdict that i dont have to upsize the ground in that situation, is it ok to run a 10awg for derating purposes and a 12 awg ground on a 20 amp circuit??

 

[kwired]

I'll weigh in as disagreeing with Rob and Bob.

This is the exact reason the wording was changed in 2014...

If the #10's are "the minimum size [ungrounded conductor] that has sufficient ampacity for the intended installation", the EGC is not required to be upsized.

I have to agree that is what we have with 2014 NEC.

So just because we had to upsize the ungrounded conductors because of high ambient temperature or more than 3 conductors, that upsized ungrounded conductor can't carry as much fault current than the same size conductor that was not upsized for high ambient or more than 3 conductors in a cable or raceway

I also agree with that and I still think this application needs more rewording, but don't really have any suggestions to offer either.

 

[infinity]

So does anyone agree that this still would not apply to voltage drop compensation unless VD compensation was required somewhere in the NEC.

So is the verdict that i dont have to upsize the ground in that situation, is it ok to run a 10awg for derating purposes and a 12 awg ground on a 20 amp circuit??

Are you on the 2014 NEC?

 

[Smart $]

So does anyone agree that this still would not apply to voltage drop compensation unless VD compensation was required somewhere in the NEC.



Are you on the 2014 NEC?

Even under 2014 it would apply to voltage drop scenarios where the ungrounded conductors are larger than the minimum required under Code.

And if you look at the CMP comments, I believe the change in wording was just to clarify the intent of earlier edition wording.

 

[infinity]

Even under 2014 it would apply to voltage drop scenarios where the ungrounded conductors are larger than the minimum required under Code.

Yes that's what I'm saying, under the 2014 if you just decided to use larger conductors for VD or just because you had them on the truck then you would still need to proportionally increase the size of the EGC for example:

#10's on a 20 amp circuit would require a #10 EGC.

 

[iwire]

Even under 2014 it would apply to voltage drop scenarios where the ungrounded conductors are larger than the minimum required under Code.
.

But it won't apply to a fire pump where voltage drop compensation is NEC required

 

[Smart $]

But it won't apply to a fire pump where voltage drop compensation is NEC required

That is correct.

 

[Smart $]

Yes that's what I'm saying, under the 2014 if you just decided to use larger conductors for VD or just because you had them on the truck then you would still need to proportionally increase the size of the EGC for example:

#10's on a 20 amp circuit would require a #10 EGC.

Correct. A code forced upsizing of ungrounded conductors does not require the EGC to be upsized... but not limited to just under 2014... essentially all editions back to 1999 (or 2002 ?)

 

[iwire]

That is correct.

Well that strikes me as a screw up.