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  • Different voltages in same conduit/wireway

    What are the rules, if any, concerning running multiple voltages (480V & 240V) in the same wireway?

  • #2
    Re: Different voltages in same conduit/wireway

    Different voltages must be run in separate conduits. 110/220 separate from 277/440.

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    • #3
      Re: Different voltages in same conduit/wireway

      You are allowed to have conductors of different voltage classes in the same conduit, provided that all have an insulation rating at least as high as the highest voltage represented within the conduit. Reference 300.3(C)(1). Make sure the wires are marked at each end so one voltage cannot inadvertantly be mistaken for the other. Also - per Code - ALL junction boxes must be clearly marked to indicate panel source, circuit number and voltage of the circuits in it on the J-box cover with a permenant felt marker or other labeling means.
      Last edited by killavolt; 02-17-2009, 03:11 PM. Reason: Added information

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      • #4
        Re: Different voltages in same conduit/wireway

        I concur with killavolt; as long as you're using 600 volt rated insulation on the wires, you can mix the 120/240/480 voltages.

        I believe anything considered low voltage (less than 600 volts) can be placed in the same raceway without any problems. It was routine to put the 120 volt control wires in the same conduit as the 480 volt motor leads. It's been a while, but might be that electric motors over 150hp have to have separate conduits for motor leads and control wires.

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        • #5
          Re: Different voltages in same conduit/wireway

          I believe that was an exception, not a rule Randy, concerning motor circuits and motor controls. I'll have to look that one up. If I can't find it, I have Code class tuesday and thursday nights. I'll go ask.

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          • #6
            Re: Different voltages in same conduit/wireway

            Mix low level signal (24vdc, 0-10vdc, or communications) in the same conduit or wireway. This has caused all sorts of problems. Now VFD power wiring causes the most problems and these should be in seperate conduit from all other signals.
            Now I have seen where VFDs were run in the same conduit but I believe the reason this was ok was that all the equipment is basically running together. If you have different motors that run at different speeds and such running them seperate from each other is probably necessary.
            Builders South London

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            • #7
              Re: Different voltages in same conduit/wireway

              Originally posted by kaitlin View Post
              Mix low level signal (24vdc, 0-10vdc, or communications) in the same conduit or wireway. This has caused all sorts of problems. Now VFD power wiring causes the most problems and these should be in seperate conduit from all other signals.
              Now I have seen where VFDs were run in the same conduit but I believe the reason this was ok was that all the equipment is basically running together. If you have different motors that run at different speeds and such running them seperate from each other is probably necessary.
              Most control wire insulation is only rated for 300V. 600V rated control wire is hard to find. Control wire can be run in the same raceway but it must have a partition seperating it from the 600V rated wire. It can be inside flexible non metallic conduit inside the raceway with the 600V rated wiring.

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              • #8
                Re: Different voltages in same conduit/wireway

                Originally posted by killavolt View Post
                Most control wire insulation is only rated for 300V. 600V rated control wire is hard to find. Control wire can be run in the same raceway but it must have a partition seperating it from the 600V rated wire. It can be inside flexible non metallic conduit inside the raceway with the 600V rated wiring.
                I think you will find most control wiring is 600 volt rated, THHN, THWN, MTW. I am curious as to using non-metalic flex in a wireway, I didn't see a 600 volt insulation rating on it plus I don't see it as worthwhile use of available fill.
                This all assumes that the control voltage is 110VAC, for 24VDC controls, separate wireway, different colors but still 600V insulation on conductors.

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                • #9
                  Re: Different voltages in same conduit/wireway

                  Originally posted by AnHonestOpinion View Post
                  I think you will find most control wiring is 600 volt rated, THHN, THWN, MTW. I am curious as to using non-metalic flex in a wireway, I didn't see a 600 volt insulation rating on it plus I don't see it as worthwhile use of available fill.
                  This all assumes that the control voltage is 110VAC, for 24VDC controls, separate wireway, different colors but still 600V insulation on conductors.
                  I should have made it clearer when I quoted Kaitlin's post. I was referring to her remark about mixing low level signal 24vdc, 0-10vdc, or communications wire. I agree that conduit inside another raceway is not a prudent use of available fill, but NEC code requires a partition to keep wires of different voltage ratings seperate. If I were doing the job, I would just hang more pipe and keep those seperate.

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                  • #10
                    Re: Different voltages in same conduit/wireway

                    SO with all of this said....
                    Can I legally run 480VAC (shielded 14/4) to my VFD's in the same wireway as my 120VAC, 24VDC, and devicenet wiring AS LONG AS I have a wireway barrier between them? Noting that the 24VDC and Devicenet wiring will be rated for 300V.

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