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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
        [COLOR=#333333]See the first sentence in Section 501.15(B)(2). The "boundary" is where the conduit [/COLOR]leaves [COLOR=#333333]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 [/COLOR][COLOR=#222222][COLOR=#222222]Section 501.15(B)(2) where it indicates the boundary seal may not always need to be explosionproof.
        [/COLOR][/COLOR]

        [COLOR=#333333] Often a judiciously located seal can do double duty as both an equipment seal (but it must still be [/COLOR]explosionproof in[COLOR=#333333] that case) and a boundary seal.[/COLOR][COLOR=#333333]

        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
        [/COLOR]and explosionproof [COLOR=#333333]although it isn't likely.[/COLOR]
        "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?

            Comment

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