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Wire type to use inside

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  • Wire type to use inside

    Hi,

    I plan to add a sub-panel into my garage.
    I will use a 40 AMPS 220 Volts breaker in my house main panel up to my sub-panel in the garage. The garage is together with the house. No wire will be outside. I will pass the wire between the joist.

    The cable I have on hand is a 8/3 NMWU. NMWU is for underground. Can I use that cable inside even I don't have to run it underground?

    NMWU is rated 60 degree C while NMW is rated 90 degree C.
    I live in Canada.

  • #2
    Re: Wire type to use inside

    Originally posted by Boogatoo View Post
    Hi,

    I plan to add a sub-panel into my garage.
    I will use a 40 AMPS 220 Volts breaker in my house main panel up to my sub-panel in the garage. The garage is together with the house. No wire will be outside. I will pass the wire between the joist.

    The cable I have on hand is a 8/3 NMWU. NMWU is for underground. Can I use that cable inside even I don't have to run it underground?

    NMWU is rated 60 degree C while NMW is rated 90 degree C.
    I live in Canada.
    I'd be comfortable running the 8/3 you have. You already own it. The outdoor coatings are a bit more durable. I wouldn't worry about the difference in temperature ratings unless you plan on overloading it or running it on top of heating pipes.

    If you want to know if it will meet code calling your local inspector is the only way to go.

    Comment


    • #3
      Re: Wire type to use inside

      To Boytyperanma, actually, I plan this:

      From the main panel,
      Add a 40 AMPS breaker, Connect the 8/3 NMWU cable to it to make my run to the panel in my indoor garage.

      From the panel in the garage,
      Add a 220V 20 AMPS breaker for My dust collector.
      Add a 220V 15 AMPS breaker for my TS3650 Ridgid table saw
      Total 35 AMPS. I WILL NOT ADD MORE CIRCUITS TO THIS INSTALLATION

      The panel in the garage is a brand new Square D with a 100AMPS main breaker. I am using this panel as a Sub-panel considering that the 100 AMPS main will never trip. The 100AMPS main is only used as switch. I WILL NOT ADD MORE CIRCUITS TO THIS INSTALLATION because my 8/3 won't be protected by the sub main breaker. In short this is a "Sub-panel" installation and the tripping breaker will be the one in my main house panel.
      Therefore the total amps of all the breakers should remain under the ampacity of my 8/3 Cable that allow 40 AMPS.

      Would 35 AMPs bring the wire at a too high temperature considering that NMWU is rated 60 degrees C?

      Comment


      • #4
        Re: Wire type to use inside

        Considering your not actually going to be using 35 amps your well within the wires capacity I doubt you'd notice the wire even getting warm. If your one man workshop I wouldn't worry so much about putting a few more circuits in. Unless your in the habit of walking away from running table saws to work on something else.

        Comment


        • #5
          Re: Wire type to use inside

          Originally posted by Boogatoo View Post
          To Boytyperanma, actually, I plan this:

          From the main panel,
          Add a 40 AMPS breaker, Connect the 8/3 NMWU cable to it to make my run to the panel in my indoor garage.

          From the panel in the garage,
          Add a 220V 20 AMPS breaker for My dust collector.
          Add a 220V 15 AMPS breaker for my TS3650 Ridgid table saw
          Total 35 AMPS. I WILL NOT ADD MORE CIRCUITS TO THIS INSTALLATION

          The panel in the garage is a brand new Square D with a 100AMPS main breaker. I am using this panel as a Sub-panel considering that the 100 AMPS main will never trip. The 100AMPS main is only used as switch. I WILL NOT ADD MORE CIRCUITS TO THIS INSTALLATION because my 8/3 won't be protected by the sub main breaker. In short this is a "Sub-panel" installation and the tripping breaker will be the one in my main house panel.
          Therefore the total amps of all the breakers should remain under the ampacity of my 8/3 Cable that allow 40 AMPS.

          Would 35 AMPs bring the wire at a too high temperature considering that NMWU is rated 60 degrees C?

          Just make sure that you use a 40 amp double pole breaker at the main panel to feed this circuit. The 60 degrees C rating is for its intended purpose in Direct Burial. In open air it would have a higher rating. So, you're fine.

          Comment

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