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Is it ok (code compliant and not otherwise inadvisable) to twist two or more THHN conductors together (before running in conduit) ?

Issues I can imagine:

  1. EM fields cancel out. Not a bad thing.
  2. Twisting stresses the insulation jacket. Seems like you'd have to twist REAL tight.
  3. Causes excessive heat buildup - this one seems like it could actually be a concern.

I want to twist a couple of neutral-hot pairs together, to keep distinct within one conduit. Easy to do by chucking the two ends together in a drill. Should give a nice clean look.

  • 1
    A clean look... inside conduit? You'd be untwisting at any junction anyway, right? – isherwood Jul 19 '17 at 13:52
  • When I worked as an electrician, we put effort to have the wires as straight as possible. Because in many cases, twist made the wires lock up in a bend and the conduit had to be teared out and a new one laid. – Agent_L Jul 19 '17 at 16:16
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Electricians never purposely twist wires together before installing them. As a matter of fact, we attempt to keep large conductors separate as they are pulled into the conduit so they do not twist around each other.

First, it is completely unnecessary for identification we just number the neutrals or tag them with some colored tape to indicate which phase conductor they go with.

Second, by twisting the conductors you are filling up more of the conduit and you are shortening the conductor. Using more wire to accomplish your purpose without a clear advantage is wasteful.

Third, the EM fields cancel out anyway without twisting. The reason Cat 6 cable is twisted is to reduce external signal transfer to the wire pairs not for EM cancellation between the pair.

Focus your time on something more productive.

Good luck and stay safe!

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    Also if for any reason you need to re-pull or add a conductor it could make things very difficult. – Retired Master Electrician Jul 19 '17 at 12:17
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    Such additions being pretty much the point of conduit. – Harper Jul 19 '17 at 18:47
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Horrible idea. The worst part is that you're using it instead of a proper method of marking.

You will exceed your conduit fill in a heartbeat since instead of n wires of x diameter, you now have n/2 (effective wires) of 2x diameter.

Becuase it's irregular, your AHJ is likely to nix it and make you tear it out.

You may also have problems with thermal limits in NEC 310.15. That calculation assumes that 10 feet of conduit with 6 wires contains 60 feet of wires. Twisting adds length, so you might actually have 70 feet of wire in your 10 feet, counting as 7 conductors for 310.15 purposes.

Have you ever added a wire to existing conduit? This would make it a lot harder, because all those twists will create hundreds of snag points.

Unless you twist them so tight as to damage the wire, they're going to fray anyway once you get into the box. You won't tell them apart without other marking, which is really what you ought to be doing.

Mark individual wires to make them distinct. Allowing two identical, undistinguishable wires into the same conduit is planning to fail unless they are messengers or phases.**

That's why they make 11 colors of wire and 10 colors of tape. (11 if you count "no tape" as a tape color). 121 combos and you only need 8.


** But even that can be screwed up: One non-electrician ran 2 conduits to our machine shop, great, except he put all the 10AWG wires, 4 red and 4 black, in the same conduit. And then, he picked 1 red and 1 black to be circuit 1! shakes head If he had just put 2x2 in each conduit, and use both blacks in conduit 1 for circuit 1, he would have accomplished all his marking requirements with no tape. Not that hard if you use your thinking cap.

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