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I am connecting sets of three #8 wires for a 220 circuit, and have found large blue wire nuts from Ideal that are rated for this wire size. But they are very difficult to twist to the point that the wires themselves begin to twist together, and upon removal the nuts don't seem to have made much of a grab on the wires, or to twist them. The wires are a combination of 7 strand and 19 strand. I see that multipart "Polaris" type connectors might be better, though much more expensive. I also wonder whether the set screws on Polaris (or the Morris that seems to be the same but much less expensive) are subject to backing out unless locked in some fashion. Help greatly appreciated!

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If you mean these, they are not -- oh wait, if you dig into the data sheet, they are rated for three #8. Things the literature doesn't tell you that the data sheet does.

Now, you are pushing the limit of the wire nut's range, so it may be difficult to work with. They work better in the middle of their range. It also sounds like you are being timid with the wire nut, and you really need to show it who's boss.

You're worried about the wires twisting, they're supposed to twist. If even the insulated parts of the wires start to coil around each other, that's fine, that's an indicator that that you're tightening it enough.

Also, do not pre-twist the wires that will be going into the wire nut. That is just dumb, the wire nuts themselves are about to do a fine job of that. Make sure the wires are square/even going in, pretwisting makes that harder. Also you have a chance of twisting in the wrong direction.

Never tape wire nuts, except for a single wire on a nut (otherwise, those don't hold). Instead, firmly pull on each wire. They shouldn't even think about coming out of the nut. If they do, that indicates a bad job of wire nutting. They are also making bad contact, and will cause arcing and fire. Unwind it, straighten them out a bit, line them up properly, and do it again.

  • the Ideal Blue Twister (454) is rated for 2 or 3 #8 (stranded or solid) - images.homedepot-static.com/catalog/pdfImages/d1/… – batsplatsterson Feb 4 at 10:45
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    I tell my apprentices just because something fits and may be ok within its listing doesn't mean it is the right thing to do. I would prefer Polaris over wire nuts in this case. My number 2 choice would be to compression lug or split bolt with all the tape I use on these kind of terminations the cost ends up close to a polaris. Yes you can use nuts but should you? – Ed Beal Feb 4 at 23:53
  • @EdBeal i just did a soldered connection on a 110 year old piece of equipment, and insulated it with friction tape. This replaced a barrel crimp that was wholly non-period and not rated for the voltage. The tape usage wasn't so bad and the natural thickness was very nice. At the end, tore the tape down its length about 2", split them, wrapped them around and tied a knot. Keeps the friction tape from unraveling. I believe the Knob and Tube gang would have followed with a layer of vinyl tape, but this work is older than that and it would not have been appropriate. – Harper Feb 5 at 0:04
  • I do forget that because of the environment I work in mostly (heavy industrial) we use more to keep things from rubbing through. Cambric 2 layers, linerless until no sharp points usually 3-4 layers and finish up with a couple layers of super 88. I am certified in my state to do knob and tube repairs haven't done many lately but there were a few years I was one of the few in my area we had to use waxed cambric and tie the same as you did not much there but it worked for many decades. – Ed Beal Feb 5 at 0:40
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As an alternative, have you considered using a split-bolt connector (we used to call these wire gurneys)?

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    Split bolts require a big oodle of tape though.... – ThreePhaseEel Feb 3 at 21:00
  • With cambric and linerless being so expensive split bolts end up costing almost as much as Polaris. Polaris are the fastest and easiest to reuse when replacing a motor after a motor replacement the Polaris become much cheaper. – Ed Beal Feb 4 at 23:57
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Wire nuts make excellent splices but they do require some proficiency before you can make reliable connections. Even people that are proficient struggle with bigger stranded wires, and the combination you're splicing is near the limit of the connector. If you want to use wire nuts, get a few scraps of #8 stranded and practice with them.

(Regarding wire nut termination methods - I can take or leave pre-twisting with solid wire, but I never pre-twist stranded wire. Make sure your wires are even. Tug test each wire.)

In my opinion you did something very important: if something doesn't seem to work right for you, find an alternative.

The insulated lug connectors such as the Polaris are expensive and bulky but they are pretty straightforward, as long as you follow the instructions and strip the right length and torque the lugs as directed, there's really no learning curve to become fully proficient. Insulated lug connectors are not immune to failure, but nothing is.

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Twist the wires together with a pair of lineman's pliers before you put the wire nut over them. You can hold the insulated portion of the wires stable with a pair of needle-nosed pliers for stability. Typically, wires are meant to be twisted together first, before applying the wire nut. The large, blue marrettes are designed to handle a pair of #8 AWG conductors. Strip back enough of the insulation to allow for an easier twisting motion. You can always cut off any excess strands of wire before putting the wire nut on.

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    All the brands of wire nuts I use state no pre twisting required. Holding the insulation with pliers is going to damage the insulation- – Ed Beal Feb 4 at 23:46
  • I'd use a split bolt. But if I was trying to get three #8s into a wire nut, I'd sort of twist them first, to be able to start the nut, and to finish it without one popping out. You've got to get them to behave first, +1. – Mazura Feb 5 at 0:25
  • I think he is trying to connect two 8/3 cables together, not three. So, that's two pairs of three wires. I had to re-read the original post as it can be confusing. – Chris Taylor Feb 5 at 0:56

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