Grounding Bus: # of wires under lug

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BMacky

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Foster City, CA
Help! I recently had an inspector call me on "too many wires under the lugs" on a ground bus in a single-phase residential panel. I always thought and was trained that you could put up to 3 ground wires under one lug. Now, looking back I can say that that would depend on the wire size to some extent, but I am talking about 12 and 14-gauge Romex here. The inspector quoted "2 is the max" so to that I say with what size wire? Sound appropriate?

I've asked some colleagues and they've said they thought it was two but would have to check. Well, I did some checking on my own and found squat! The toughest thing about the NEC Code book is locating answers to questions like this. I took what I thought was a logical approach and searched through Article 250 Chapter 6, but found nothing there.

Can someone please cite where in the NEC I might locate the answer to this and any other associated data, like why look for it in another chapter if that is in fact where it may be?

Thanks!
 
Most newer panel lug listings will have one or two EGC's of certain sizes - usually say it right on the lug or bar if not the panel sticker inside - sorry.... If you find yours says more than that - KOOL!
 
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If the inspector try to raise the heck out of ya why not take a photo of that sticker in the box it will show the listing of the numbers of grounding conductor on either neutal or grounding busbar.

Majorty of resdentil breaker box bussbar useally take 1 or 2 #14 or #12 depending on the manufacter and model number


Merci,Marc
 
Thanks, guys. I did realize later it's a listing issue per mfrs specs. My "inspectress" was on the ball, as it was a Cutler Hammer and she knew their spec is 2-per.

Thanks for the feedback.

bob
 
One bit left out is they have to be all the same size and material, so you cant put a 12 & 14 AWG under the same screw or mix aluminum & copper conductors.
 
BMacky said:
Thanks, guys. I did realize later it's a listing issue per mfrs specs. My "inspectress" was on the ball, as it was a Cutler Hammer and she knew their spec is 2-per.

Thanks for the feedback.

bob
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Told you guys that "sometimes" we know what we're talking about.:grin:
 
Twoskinsoneman said:
Could someone ref the NEC code Ref for this?
Thanks.
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110.14(A) covers dissimilar metals. Also 110.12(C) hints at the corrosive action between dissimilar metals. As far as 2 conductors of different sizes under one terminal I'm thinking that's covered in 110.3(B), manufacturer's installation instructions.
 
The labels for the equipment are pretty specific and tell you that you can either use (for those that allow 2 per terminal) 1-2 #14 OR 1-2 #12 which does not give you the option to put 2 different sizes on one terminal. That makes sense because you can have uneven pressure.

I saw someone said that they were "trained" to put up to 3. This is a problem because training should follow the NEC and remind you to always check manufacturer specs. It is your responsibility as an electrician to know what you are doing.

Next item, why the heck would you want to put more than 1 on a terminal anyway? Just add another bar, simple. Why argue common sense?
 
ivsenroute said:
The labels for the equipment are pretty specific and tell you that you can either use (for those that allow 2 per terminal) 1-2 #14 OR 1-2 #12 which does not give you the option to put 2 different sizes on one terminal. That makes sense because you can have uneven pressure.

I saw someone said that they were "trained" to put up to 3. This is a problem because training should follow the NEC and remind you to always check manufacturer specs. It is your responsibility as an electrician to know what you are doing.

Next item, why the heck would you want to put more than 1 on a terminal anyway? Just add another bar, simple. Why argue common sense?
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Common sense would tell me to put 2 in each hole ( if allowed ) rather than

installing another grd. bar.
 
benaround said:
Common sense would tell me to put 2 in each hole ( if allowed ) rather than installing another grd. bar.
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I can't find "common sense" in the NEC.

Besides, common sense rarely is. ;)
 
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