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  • Electricians threads vs Plumbing threads

    I think we (electricians) may have got the wrong threader from rigid. I was told there was a difference in plumbers threads and electricians threads for rigid pipe. What exactly is the right type of threads for electrical??

  • #2
    Re: Electricians threads vs Plumbing threads

    brother

    us plumbers use npt/ national pipe taper threads.

    you electricians typically use npsm/ national pipe straight mechanical threads.

    ours are tapered to allow for a joint that tightens and becomes water tight.

    your's are typically a straight thread that doesn't require a taper. more of a running thread.

    the larger 141 / 2.5''- 4'' and 161 / 4''- 6'' geared threaders have a setting that allows for straight or tapered threads.

    now that we got this straight

    can you please spend some time here and answer the few electrical questions that come to our site

    welcome to the ridgid forum.

    rick.
    phoebe it is

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    • #3
      Re: Electricians threads vs Plumbing threads

      If you go to the conduit sites, they seem to be posting that there threads are the tapered threads on the rigid conduits they sell, from what I have been able to figure, is the fittings are straight and the pipe is tapered, I do not know if it has always been this way or not, I know the general statement is electricians use straight threads and not tapered, but I do not find evidence of that, on the pipe,

      some quotes from the manufactures web sites,
      http://www.ridgidforum.com/forum/sho...onduit+threads

      this thread has some quotes from the NEC,
      http://www.ridgidforum.com/forum/sho...onduit+threads

      sections sited are 344.28 Threading and Reaming, and 344.42(B) Couplings and Connectors,

      IF all else fails, check with the inspector of the area, to see what they want,
      Push sticks/blocks Save Fingers
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      • #4
        Re: Electricians threads vs Plumbing threads

        I think (need to check to be sure) that IMT which is threaded but thinner wall than #40 galv iron pipe dues use straight rather than tapered threads. Connectors normally have straight threads on them.

        I'll try to research this and will post what I find out.

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        • #5
          Re: Electricians threads vs Plumbing threads

          If you go to the conduit sites, they seem to be posting that there threads are the tapered threads on the rigid conduits they sell, from what I have been able to figure, is the fittings are straight and the pipe is tapered,
          This is what I have always heard too. Tapered thread and straight thread fittings. This yields a connection where say in a coupling the 'pipe' * (AKA conduit by sparkys ) ends meet so that there is no gap on which wire can snag when pulled through the raceway. Least that what I had told to me again recently by an electrician, but it seems that even THEY (this thread starter and other threads) are not sure of how it all goes together.
          * It really is pipe so you should be having your local plumber run your pipe for you. You don't know how to make bends anyway with all this End to Back and Back to Back measurements.
          Last edited by Bob D.; 09-17-2008, 05:14 PM.
          ---------------
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          • #6
            Re: Electricians threads vs Plumbing threads

            Per the NEC 2005, rigid (RMT) and intermediate metallic tubing (IMT) shall have threads that taper 1:16 (3/4" per foot). Running threads shall not be used at couplings. (Ref: Art 344 & 342 respectively).

            IIIIC (If I interpret it correctly) when you join two conduits, you have to have a positive friction lock on the threads. If in concrete, etc, it has to be tight enough that there is not intrusion from water, concrete, etc. Even if the connector is straight, the threads in the conduit need to be tapered.

            Maybe one of the plumbers can say if this is the same as their pipe.

            Go

            PS. Radius of bends is covered in Chapter 9, Table 2, so make sure you show that to the plumber!!
            Last edited by Gofor; 09-17-2008, 08:29 PM.
            Practicing at practical wood working

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            • #7
              Re: Electricians threads vs Plumbing threads

              http://www.steelconduit.org/pdf/ConGuide.pdf

              See section 4.1

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              • #8
                Re: Electricians threads vs Plumbing threads

                Electricians use both, depending on the environment surrounding the conduit.

                Electricians use the straight thread when installing the conduit with lock nuts.

                Condulets are tapered, and electricians use a taped thread where required

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                • #9
                  Re: Electricians threads vs Plumbing threads

                  I know here in Ontario as I think the rest of Canada the threads are the same as we use the same dies & threading machine as the plumbers. They don't like us using the same dies/machines as they say our ridgid conduit tears their dies.

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