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    class 1, div 2 installation

    so after a lot of reading thanks to this forum i am seeking clarification/verification my understanding of things is correct.

    i am working on a petro chemical skid that is rated class1, div2, grp bcd. all instrumentation/devices on the skid are Ex-d ,Ex-d HOAs on a couple of motors, junction box is nema 4x, cable will be a dekron sutiable for cl1, div2, listed sealtite with appropriate fittings, and i think that covers the basics. so if i understand things properly i need conduit seals going into the JB, regular conduit fittings, and no seals going into the devices.

    so am i wrong or is there something i missed?

    Thank you

    #2
    Originally posted by cdcabrera View Post
    so after a lot of reading thanks to this forum i am seeking clarification/verification my understanding of things is correct.

    i am working on a petro chemical skid that is rated class1, div2, grp bcd. all instrumentation/devices on the skid are Ex-d ,Ex-d HOAs on a couple of motors, junction box is nema 4x, cable will be a dekron sutiable for cl1, div2, listed sealtite with appropriate fittings, and i think that covers the basics. so if i understand things properly i need conduit seals going into the JB, regular conduit fittings, and no seals going into the devices.

    so am i wrong or is there something i missed?

    Thank you
    From your description you are using Zone rated equipment in a Division classified location. This is permitted but with some very nontrivial restrictions. See Section 501.5 and its cross-reference to Section 505.9(C)(2). You must establish the Division equivalence of the "Ex" equipment. Hint: Unless it is AEx, there is no Division equivalence.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2017 NEC unless otherwise noted.

    Comment


      #3
      thank you for the insight on the mixing and matching terminology. still working on getting a better understanding of how all the pieces work together and navigating the code book since its constantly referring to something else instead of just an answer. i will be spending some time with the mike holt code books this weekend to further my understanding.

      all equipment/components have a class1, div2, group bcd rating. Spec from a pressure transmitter - Elec. Area: Class I, Div. 2, Gr. B, C, D Approval: FM, Explosion Proof and the option from the mfg website reads "FM Explosion-proof, Dust Ignition-Proof".

      if i understand 501.15(B)(1) correctly since the JB is not required to be Explosionproof then I dont need a seal, however I am struggling to understand how 501.15(B)(2) plays into the equation. Would the boundary be the classified area or each component of the 'system' (conduit/intruments/JB), based on the distance comment of 10ft I would assume that is leaving the overall area.

      Comment


        #4
        See the first sentence in Section 501.15(B)(2). The "boundary" is where the conduit leaves the class I, Division 2 location. It can be created by several conditions which is why Sections 500.4(A)&(B) and 500.5 are important. Also, check the last sentence of Section 501.15(B)(2) where it indicates the boundary seal may not always need to be explosionproof.

        Often a judiciously located seal can do double duty as both an equipment seal (but it must still be explosionproof in that case) and a boundary seal.

        Unless they are "factory sealed", the devices will still need a seal. Depending on what is in the junction box it may need to be sealed
        and explosionproof although it isn't likely.
        "Bob"
        Robert B. Alexander, P.E.
        Answers based on 2017 NEC unless otherwise noted.

        Comment


          #5
          The JB just be terminal blocks, so no switching or contacting devices. The customer will enter the box and hook up their multi-paired cable to be wired to the DCS for system monitoring and control. Thank you for your help and insight.

          Comment


            #6
            24 VDC Power to Nonincendive rated instrument

            I am installing an Ultrasonic Flowmeter in a Class I Div 2 area of the plant. The flowmeter states that it is C1/D2 rated NI. The power requirements are <15 Watts 20 to 32 VDC. The signal will be passive and powered by the DCS. My question is can I supply 24VDC power from our UPS power supply in the control room through the same junction box with the signal cable or do I need to run a separate power cable and provide seals at the instrument?

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