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This seems like a pretty straight forward question and hoping not a poor question but here we go.

If you have a pigtail for three wires (say # 14 AWG if that makes a difference) together in a wire nut but you want to add another wire to the mix. Is the proper method to undo the wire nut and untwist them and try to straighten out all three as best as possible? (In IT there was a tool to straighten ethernet wire but haven’t seen such a thing for Romex). Then line up all four wires (new one included) so they're parallel and retwist again from scratch and wire nut it with a fresh new wire nut? Seems like a commonsense answer but with all things in life you can never be too sure and curious if professional electricians had a technique of their own to share.

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  • The electrical connection is made by the pressure of the copper wires being squeezed together by the spring in the wirenut. It is like a switch contact, the contacts are shoved together with pressure by the spring. The twisting does very little for this other than holding the wires in position while being crushed together by the wirenut when it's threaded on. More important than twisting is using the proper size wirenut you may need a bigger one. This is a different contact scheme than ethernet connections which depend on microwelds being made during the punchdown operation. – Ted Mittelstaedt Jan 11 at 18:29
  • Yea I have been going by ideals chart plus the protwist connectors have a really large range sk I can use from 1 to 6 14 awg wires which is pretty slick. I think this is a good explanation but when it comes to adding to an existing pigtail. So you realign everything from scratch or by what it sounds you may even skip that step and just put this wire next to the existing cluster and just nut it directly to that using the clamping force of the wire nut. – Irish Redneck Jan 11 at 18:48
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    @IrishRedneck, keep in mind that those charts are the maximums allowed assuming everything is done perfectly (likely by a pro). For DIYing, using them more in the middle of their range tends to be a whole lot easier, and more forgiving of imperfect technique. – Nate S. Jan 11 at 19:17
  • Completely unrelated - I've never heard of a "tool to straighten ethernet wire" but some googling suggests youtube.com/watch?t=11s&v=CHQzQQYx3vU Thank you for that. – Criggie Jan 12 at 22:44
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It doesn't really matter how the wires were before. The wire nut is gonna reshape the wires when you crank down on it!

The #1 blunder with wire nuts is being too much of a softie and being afraid to use the nut to reshape the wires. You have to! If you don't, the wires won't mesh firmly, you won't have good contact, and the connection will overheat, arc and start a fire.

A properly done nut should pass a "pull test" -- hold the nut and yank on each wire, one at a time.

If a nut fails a "pull test" then it's either a problem with technique, not tightening enough, not lining up the wires evenly, or using the wrong nut - i.e. using a wire nut right near the extremes on its bell curve. Go up or down a size, please!

If somebody's going for "tape" to keep wirenuts from falling apart, they usually think they are doing a great job securing it, actually they have a bad connection to begin with that is likely to melt and burn up from arcing. The job isn't to physically hold the wires together, it's to electrically do that.

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    I agree with this answer in the sense that anything that passes the pull test is fine, but in my experience it's easier to get it to pass the test the first time if you untwist the old connection at least a little. If the last guy put enough force on it the first time, the end of those three solid #14s are squished together hard enough that they resemble something closer to a single #6 stranded, and the new #14 being added is more likely to just circle around the old stuff than properly twist with it. They don't need to be perfectly straightened, but IME unbundling the old stuff is good. – Nate S. Jan 11 at 18:37
  • I’ll be honest I’m paranoid about overnightening wire nuts as they are so easy to keep turning and turning even without the wire twisting it’s body any further. Read on a forum a guy twisted too much it came through the top haha. So it’s a matter of finding that in between from what I’m getting. Have you ever seen a wire nut fall off a wire while just sitting in an outlet box? I can’t imagine there might be that much static force in an outlet that to really loosen one that’s been twisted atleast four revolutions. – Irish Redneck Jan 11 at 18:53
  • @harper is the possibility of arcing occur between the strands of wire or is the arcing occurring between the wires and the nut spring? If the arcing can occur between the wire and the metal wire nut threads I guess that shows pretwistinf doesn’t always stop the risk of arc related fires. – Irish Redneck Jan 11 at 18:57
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    @IrishRedneck, twisting hard isn't just for the mechanical connection; it's for the electrical connection too. Think about it -- wires are cylindrical, so when you twist them loosely together, the point of contact is actually only a thin line where the cylinders meet, which isn't much. If you twist them together with force, the cylindrical copper starts to deform and the wires squish into each other, so that the thin line of contact expands and becomes a much wider strip, which conducts much better. – Nate S. Jan 11 at 19:02
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    @IrishRedneck, there's no number of turns that are always correct -- how many it'll need varies based on the size and brand of wire nut, and how many wires you're putting in it. In your example one that accepted 1-6 #14 wires, it'll need a whole lot more twisting to put proper force on two wires than it will 6, because you have to screw it farther into the narrower part of the cone inside the wire nut. – Nate S. Jan 11 at 21:41
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Harper has probably seen everything and has more experience but I come from a flipper who does things right point of view - try to speak in common terms.

The #1 issue I see is homeowners (or poor electricians) trying to wrap their connections then throw a nut on it. They are all flimsy and it drives me nuts because it is a bit of work to straighten out the connections and start over.

Given that you have a good wire nut that is properly sized (not overly big or little).

  • you match up your 2-4 wires and try to give them 3 inches or so of being "straight and even"
  • you squeeze them into nut, straight and even.
  • you twist the hell out of the nut while applying a little bit of force into the nut so each wire sticks to the end.
  • stop when the wires outside the nut start to become overtwisted - or you run out of physical length
  • you can check a good pigtail by unscrewing the nut 3-4 times and your nut comes of but your wires are locked stranded together.

If unscrewing nut unscrews your strand then you are probably getting to the limit on what that nut can handle. If you unscrew nut and wires are still loose there is a good chance the nut was too big or you did not have your wires straight and even. If a nut is for 2-6 #14 and you are pigtailing 2 #14, chances are the nut will not do a good job binding the wires.

OR the OMG maybe they will modularize electrical to make electricians obsolete pathway :)

Buy the appropriate wire connectors and skip the nut all together. (these are not my recommendations, just pictures for reference. Please read specs for any that you buy, and some do not work with stranded.

enter image description here

The next picture is an aluminum pigtail example. I have used this model. I have actually used this enough to where I should buy stock (these are EXPENSIVE). But they are very homeowner, DIY friendly. Also pigtailing existing aluminum is hard when you don't have a lot of slack in the line. Often times the ends are burnt a bit so risking twisting is possible breaking off 1.5" of a line that is already short.

enter image description here

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  • One the most beautiful things I've ever seen was a pre-twist on some wires that you could've hoisted a tank with. I think about it every time I don't, because I'm too lazy. – Mazura Jan 12 at 6:16
  • @Mazura - I didn't want to come across as saying pretwist is impossible. My personal electrician pretwists. Hes 65 and has the finger strength to twist #10 like it is a flimsy thread. So yea he's good at it and the connections are in stone (he also has these cool 90 degree pliers he uses doing it). But that is not how a person asking how to do it should learn. There is an art to it. I think about how much time I spent going through houses when I was young and now it is probably a third... I certainly haven't gained strength. – DMoore Jan 12 at 6:38
  • Step one: own a linesmen. Two: learn how to use it. (I'm still on step one :) – Mazura Jan 12 at 6:40
  • @Mazura - me like cave man with linesmen. Me too powerful and nick wires every time. Cave man made to go with using needle nose or wire nut to twist! – DMoore Jan 12 at 6:54
  • Yea I have some lineman’s too and I’ve notice the knurls can leave marks on the line. Wish they made a pair without knurls. – Irish Redneck Jan 12 at 13:14

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