multiple circuit/single equip. grnd./grounded

[jemsvcs]

250.122(C) states "where a single equipment grounding conductor is run with multiple circuits in the same raceway or cable, it shall be sized for the largest overcurrent device protecting conductors in the raceway or cable."

So, if there are five circuit run in EMT (four with 12 AWG and one with 10 AWG), then this section allows only one equipment ground for all circuits as long as it is also 10 AWG?

Also, how about sharing grounded conductors? What section of Code deals with this?

Thanks,

Jemsvcs

 

[ryan_618]

Re: multiple circuit/single equip. grnd./grounded

Yes, and 210.4, multiwire branch circuits.

 

[jemsvcs]

Re: multiple circuit/single equip. grnd./grounded

Thanks Ryan...So based on 210.4 there should be no more than three ungrounded conductors sharing the same grounded conductor? That is...since there has to be voltage between each ungrounded conductor.

 

[ryan_618]

Re: multiple circuit/single equip. grnd./grounded

If you are talking about a 3 phase, four wire wye system, yes you are correct. If you are talking about a single phase, 3 wire system, only the two legs can share.


Think of it this way...every service and every feeder you have ever installed was probably a multiwire circuit. 3 phases, one nuetral. or is a single phase, 2 legs, one neutral.

Does that help?

 

[roger]

Re: multiple circuit/single equip. grnd./grounded

Now look at 225.7(B)

Roger

 

[ryan_618]

Re: multiple circuit/single equip. grnd./grounded

Your a sick man, Roger.

[ May 27, 2004, 10:17 PM: Message edited by: ryan_618 ]

 

[jemsvcs]

Re: multiple circuit/single equip. grnd./grounded

Ryan...it all made perfect sense...then Roger had to pull that out of his hat!

Like your thoughts on 225.7(B)...does this apparent exception only apply to outside circuits per the article?

 

[ryan_618]

Re: multiple circuit/single equip. grnd./grounded

Originally posted by jemsvcs:
Ryan...it all made perfect sense...then Roger had to pull that out of his hat!

Like your thoughts on 225.7(B)...does this apparent exception only apply to outside circuits per the article?

I think it could apply to all, as long as the nuetrall was sized in accordance with 310.10

 

[roger]

Re: multiple circuit/single equip. grnd./grounded

Ryan,

Your a sick man, Roger.

Hello Jemsvcs, I appologize.

Roger

 

[jemsvcs]

Re: multiple circuit/single equip. grnd./grounded

I'm not sure....I interpret it to apply only to outdoor lighting branch circuits.

Roger...any more input...or did you just do that to make my brain cramp up?

 

[ryan_618]

Re: multiple circuit/single equip. grnd./grounded

210.4 doesn't place any restrictions on how many ungrounded conductors can be used on a common grounded conductor...it just says that you can share it. The definition also doesn't address how many.

 

[roger]

Re: multiple circuit/single equip. grnd./grounded

Jemsvcs, we have had some conversations on this issue here before. What I will say is that it is specifically allowed in 225.7(B) and not specifically prohibited anywhere.

Brain cramping may just be starting.

Roger

 

[ryan_618]

Re: multiple circuit/single equip. grnd./grounded

Roger...please, PLEASE don't ask how many recpetalces on a 125 volt circuit...deal?

 

[jemsvcs]

Re: multiple circuit/single equip. grnd./grounded

Ryan...210.4 by definition of a multiwire circuit would imply no more than 3 ungrounded sharing one grounded.

Roger...you've made it worse than brain freeze...and I don't even have any ice cream!

 

[ryan_618]

Re: multiple circuit/single equip. grnd./grounded

Originally posted by jemsvcs:
Ryan...210.4 by definition of a multiwire circuit would imply no more than 3 ungrounded sharing one grounded.

You sure about that? Don't read into the definition, just read the definition...

 

[roger]

Re: multiple circuit/single equip. grnd./grounded

Originally posted by ryan_618:
Roger...please, PLEASE don't ask how many recpetalces on a 125 volt circuit...deal?

Roger

 

[jemsvcs]

Re: multiple circuit/single equip. grnd./grounded

Ryan...I think so..."A branch circuit that consists of two or more ungrounded conductors that have a voltage between them...."...how could it be more than three since ungrounded conductors of the same phase would read no voltage between them?

 

[ryan_618]

Re: multiple circuit/single equip. grnd./grounded

Lets say you have 4 ungrounded conductors, phase A,B,C and one more of phase A. The definition says "two or more" that have a voltage between them, right? So, if you can read voltage between you can take either one of your phase a conductors and measure voltage between it and phase b or c. I agree that phase A to phase A will have no voltage, but I really don't see how the definition distinguishes which two conductors are being measured.

BTW: I'm not saying this is a neat thing to do...I'm just bringing up the discrepency.


D*mn you Roger!

 

[jemsvcs]

Re: multiple circuit/single equip. grnd./grounded

Ryan...You're right, it could be interpreted that way. I think I will suggest the Panel removes 225.7(B) from future Code under the premise that if it remains I will be in a perpetual state of confusion.

 

[hurk27]

Re: multiple circuit/single equip. grnd./grounded

At least he didn't ask which way the ground terminal go's