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Thread: Class 1 Div 2 Field Wiring and Boundary Seals

  1. #1
    Join Date
    Dec 2017
    Location
    Ohio
    Posts
    2

    Class 1 Div 2 Field Wiring and Boundary Seals

    I am working on a new project in a Class 1 Div 2 environment. I am trying to develop a field wiring strategy and I have some questions I was hoping I could get help with. I have been reading Article 501.10 and 501.15 of the 2017 NEC and my head is spinning...

    Background:
    We have an MCC room that is outside of the Class 1 Div 2 area. The MCC will contain the VFDs and a 24 VDC power bank. In the Class 1 Div 2 area we plan to have remote I/O panels that will be Class 1 Div 2 compliant and will be fed 24VDC power and Ethernet network communications from the MCC. We also plan to run VFD cable from the MCC to the motors/pumps in the classified area. We want to use cable tray as much as possible to reduce the amount of conduit.

    Questions:
    If I run vaportight (TC-ER) VFD cable and 24VDC cable from the MCC to the classified area, do I need to seal at the boundary? The NEC calls out different sealing requirements for multi-conductor cables that I don't 100% understand.

    If the 24VDC power bank is built using non-incendive power supplies, can I consider the field wiring to the remote panels non-incendive as well?

    Thanks!

  2. #2
    Join Date
    Apr 2004
    Location
    Mission Viejo, CA
    Posts
    5,191
    Quote Originally Posted by mtdog_99 View Post
    ...
    If I run vaportight (TC-ER) VFD cable and 24VDC cable from the MCC to the classified area, do I need to seal at the boundary? The NEC calls out different sealing requirements for multi-conductor cables that I don't 100% understand.
    ...
    As long as conduits are not used to cross the boundary, Sections 501.15(E)(1) and (3) are applicable. You're lucky you're using the 2017 NEC. If you used 2014 the answer is still the same but your head would have spun off. Basically, multiconductor cables with continuous vaportight outer sheaths only need to be sealed at enclosures that are required to be explosionproof. Boundary seals are not generally required unless the outer sheath is not vaportight.

    ...
    If the 24VDC power bank is built using non-incendive power supplies, can I consider the field wiring to the remote panels non-incendive as well?
    ...
    This is a bit trickier. The applicable Section would usually be is 501.10(B)(3); however, without a manufacturer's control drawing‚Äč in hand, it doesn't apply.

    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  3. #3
    Join Date
    Dec 2017
    Location
    Ohio
    Posts
    2
    Thanks!

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