NM/romex ground pigtails

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don_resqcapt19

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We can agree to disagree on that opinion.....;)

My belief is that the 6" is their for the ability to service the device and terminations....but then again that my opinion on it.

I am guessing you never had a switch or receptacle connected to a conductor that was too short...and struggled to get a screwdriver on it....you don't have babies bottom hands do you Don?

I have worked on many where the device was apparently terminated and then the NM pulled back up making it impossible to remove the device without cutting the wires.

That being said, it remains my opinion, that the code does not require the 6" to remain after the connection or termination is made...I know there is probably no one else that reads the words that way, and I know that is not the intent.
 

don_resqcapt19

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I would assume that the crimp or compression connector is required to maintain a gas-tight connection that will not corrode, not just to ensure low resistance at the time of installation. Am I wrong?
I would bet that in the typical dwelling unit, two or three inches of tightly twisted solid wire would have a lower resistance than a wire nut or crimped connection even after 20 or 30 years.
If I had a low ohm tester, I could test some in my house...they were done about 35 years ago.
 

GoldDigger

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IMHO it all comes down to how long a time the 6" needs to be "left". Since it does not say "left until the termination is done", I will stick with my interpretation. :)
 

dfmischler

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I would bet that in the typical dwelling unit, two or three inches of tightly twisted solid wire would have a lower resistance than a wire nut or crimped connection even after 20 or 30 years.

If you have twisted them tight enough that no oxygen or water has gotten to the surfaces in contact then there will be no copper oxides or salts, and you may well be right. But I think I am glad that the electrician who wired my house used wire nuts.

If I had a low ohm tester, I could test some in my house...they were done about 35 years ago.

I have a hand-held LCR meter like this that displays resistance to the milli-ohm (as well as a few other things). I don't think I believe it is that accurate, but I would trust it to compare two values at the same temperature and humidity. But it would be a long drive just to get a few readings...
 

GoldDigger

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If you have twisted them tight enough that no oxygen or water has gotten to the surfaces in contact then there will be no copper oxides or salts, and you may well be right. But I think I am glad that the electrician who wired my house used wire nuts.



I have a hand-held LCR meter like this that displays resistance to the milli-ohm (as well as a few other things). I don't think I believe it is that accurate, but I would trust it to compare two values at the same temperature and humidity. But it would be a long drive just to get a few readings...
The critical specification is that the pressure on the touching surfaces (pressure, not force) be high enough for the connection to be "gas tight".
 

PetrosA

Senior Member
Think about this......if you go with Don's theory....would you cut off the ungrounded conductors shorter than 6"....the EGC is no less of a conductor and must meet the same requirements of 300.14 as well.

I will note that Don's theory is flawed because of this statement in 300.14 " Shall be left at each outlet, junction, and switch point for splices or the connection of luminaires or devices".....if you cut it off to say 5"...how to you have 6" remaining to meet the 6" requirement. The pigtail is just that...not part of the "free conductor" requirement.

I'm wondering if maybe I or others are misunderstanding something. I'm talking about a bundle of grounds under a wirenut or crimp, not just twisted. I'm understanding from some of the posters that all of the grounds under the "greenie" or crimp have to be at least six inches long, then there has to be a tail through the hole or crimp to connect to the device OR you can use a regular wirenut and twist a lead in with the other grounds to connect to a device. I think this is what you're saying as well. I have never seen anyone do this in 30 years of work, nor have I seen it done in work performed before I started back in the 80s (going back to the early sixties?).

Don's comment as I understand it, is that clipping the grounds aside from the lead to the device is acceptable as long as they are in a greenie or crimp. This is how I do it and how it's been done around here for at least 50 years. I twist my grounds with the jaws of the pliers even with the front of the wallcase and twist back till they just start to pull on the romexes, then I trim all but one and put a green wire nut on it. I haven't met an inspector between Philly and Lancaster who would fail that termination, but who knows...?
 

James L

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However many devices are to be connected, I leave about 20" of that many cables so they're long enough after twisting.

I twist from the sheathing all the way to 3" or so beyond the front edge of the box. Clip the short ones back to the end of the twist, and put my crimp sleeve at the end of the twist.

Then I fold the twists all the way to the back of the box, and have a foot long tail to work with. Then I cut all wires the same length, the length of my strippers from the front edge of the box.

Then I roll-fold them twice back into the box. On the trim, one finger in the roll and they pull out all together.

No more cutting at that point. I believe all the cutting should be done when making up.
 

dfmischler

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The critical specification is that the pressure on the touching surfaces (pressure, not force) be high enough for the connection to be "gas tight".

I'm not sure that I'm completely grasping the distinction that you are making. Pressure is force per unit area, e.g. pounds per square inch. So are you simply saying that if you have big contact areas then the total force must be higher than with small contact areas? And that once you apply enough force to deform the conductors (i.e. increasing the contact area by flattening, or whatever) that it takes a lot more force? Or is there more to it than that?
 

GoldDigger

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I'm not sure that I'm completely grasping the distinction that you are making. Pressure is force per unit area, e.g. pounds per square inch. So are you simply saying that if you have big contact areas then the total force must be higher than with small contact areas? And that once you apply enough force to deform the conductors (i.e. increasing the contact area by flattening, or whatever) that it takes a lot more force? Or is there more to it than that?
That is pretty much it. It can be easier to get high contact pressure with sharp threads than with the overall large area contact of a crimp connector.
So you can apply less force and not use specialized tools with wire nut or Wago then with a crimp using expensive high leverage tools. The end result can be equally good either way, but what it takes to get there is different.
You also have to consider that a small area gas tight contact can have a higher resistance than a wide area contact.
 
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