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NEMA 4X Motor disconnect switch, in a class I Division 2, 501.115 (B) (2)

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    NEMA 4X Motor disconnect switch, in a class I Division 2, 501.115 (B) (2)

    Hi all,

    in an industrial plant, I specified Eaton "DH367U" 800 A, Unused heavy duty switch, NEMA 4X enclosure, in a class I Division 2 area for maintenance of 400 HP motor. This switch is for is not intended to interrupt the current in normal condition. Over current and overload protection are being taken care at the upstream feeder.

    I received an RFI from t asking "what purging system you need to install for this NEMA 4X since it is located in a class I Division 2 area".
    I specified this safety switch based on my interpretation to the NEC 501.115 (B) (2): "Isolating Switches. Fused or un-fused disconnect and isolating switches for transformers orcapacitor banks that are not intended to interrupt current in the normal performance of the function forwhich they are installed shall be permitted to be installed in general-purpose enclosures."

    Please advise/confirm whether this installation conform with Code requirements or is a violation.

    Thanks.

    #2
    how is a motor a transformer or capacitor bank?
    Bob

    Comment


      #3
      Originally posted by petersonra View Post
      how is a motor a transformer or capacitor bank?
      Thanks for your response. I totally agree motor is not a listed equipment in this section. Although I would really like to know why this section pplies only to transformer or Capactor. Any guide is really appreciated.

      On the other hand,
      based on 501.115(B)(1), "Circuit breakers, motor controllers, and switches intended to interrupt current in the normal performance of the function for which they are installed shall be provided with enclosures identified for Class I, Division 1 locations in accordance with 501.105(A), unlessgeneral-purpose enclosures are provided and any of the following apply...."

      The switch I'm specifying is not intended to inturrupt the current in normal operation. It will be always Closed. teh only time it will be open while maintenance when the upstream deviceis de-energised. that's why I don't see why this enclosure should be purged orlisted for CLI, DiV 2.

      Comment


        #4
        Originally posted by wsbeih View Post
        ....

        The switch I'm specifying is not intended to inturrupt the current in normal operation. It will be always Closed. teh only time it will be open while maintenance when the upstream deviceis de-energised. that's why I don't see why this enclosure should be purged orlisted for CLI, DiV 2.
        The only way I would accept that is if you used a key interlock that made it physically impossible to open the switch unless the upstream switch is open.
        Don, Illinois
        (All code citations are 2017 unless otherwise noted)

        Comment


          #5
          One of the reasons, "This Code is not intended as a design specification or an instruction manual for untrained persons" [Section 90.1(A), NEC 2014] is the CMPs are not obligated to explain why a requirement is in place or reference all other relevant sections.
          [LIST][*]First, consider that transformers and capacitor banks do not have locked rotor conditions. See Section 500.8(B)(5) for some relevant material.[*]Second, are the fuses consistent with Section 501.115(B)(2)?[*]Third, is the switch consistent with Section 430.108 with its cross references to Sections 430.109 and 430.110?[/LIST]
          This isn't necessarily exhaustive but it's some of the reasons Section 501.115(B)(2) doesn't apply to motors.
          "Bob"
          Robert B. Alexander, P.E.
          Answers based on 2017 NEC unless otherwise noted.

          Comment


            #6
            A friend pointed out the second bullet should have referenced 501.115(B)(3‚Äč).
            "Bob"
            Robert B. Alexander, P.E.
            Answers based on 2017 NEC unless otherwise noted.

            Comment


              #7
              Thank y'all for your valuable input. I think I got good feedback to proceed.

              Comment

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