Sizing a ground wire.

[overamped]

Some of the guys at work are saying that you now need to size your ground wire the same as your ungrounded conductors and you can no longer derate them. I don't see that in the code book. Are they confusing the grounded wire (neutral) as they call it in the code book with the grounding wire (the green or bare wire).

Thanks in advance.

 

[hurk27]

Welcome to the Forum

Not true, see table 250.122 for sizing equipment grounding conductors, what you might be getting mixed up with is 250.122(B) requires us that any time we increase wire size in ungrounded conductors for voltage drop we have to increase the EGC in size proportionately according to the circular mil area of the ungrounded conductors, this many times will leave us with the same size EGC as the ungrounded.

Heres an example of this, lets say we have a long run for a 20 amp circuit ran in NM so to overcome the voltage drop we find that we need to use A #6 to over come the VD, well we can no longer use NM since 6/2 will only come with a # 10 EGC and would be a violation, so we would have to find another wiring method that can include a #6 EGC.

 

[Ponchik]

In addition to Hurk's post, depending on the type of circuit, you may reduce the size of the grounded conductor as well.

welcome to the forum. And keep coming back. You will learn good information.

 

[infinity]

Some of the guys at work are saying that you now need to size your ground wire the same as your ungrounded conductors and you can no longer derate them. I don't see that in the code book. Are they confusing the grounded wire (neutral) as they call it in the code book with the grounding wire (the green or bare wire).

Thanks in advance.

As Hurk said, according to 250.122 sometimes they're the same size and sometimes they're not. When you are using a smaller sized EGC I wouldn't call them derated, that has a different meaning altogether.

Welcome to the Forum.

 

[KentAT]

Related to this post, if I use 10AWG on 120vac 20A circuits due to derating because of 15 cccs, the minimum size equipment grounding conductor run in the single PVC conduit is a #12, per Table 250.122, correct?

 

[ActionDave]

Related to this post, if I use 10AWG on 120vac 20A circuits due to derating because of 15 cccs, the minimum size equipment grounding conductor run in the single PVC conduit is a #12, per Table 250.122, correct?

Incorrect. You have to use 10AWG. That is the problem with 250.122(B).

Check out this current thread http://forums.mikeholt.com/showthread.php?t=146941