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Thread: Conduit Sealing for IS or NI instruments

  1. #1
    Join Date
    Dec 2010
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    5

    Conduit Sealing for IS or NI instruments

    The subject installation involves IS rated instruments that are physically located in a Class 1 Div 2 area. These instruments will be wired to a PLC panel that is outfitted with a Z-Purge system. The proposed wiring installation method is to run wiring between the PLC panel and the IS rated instruments. Can you advise as to which of the following methods are acceptable? If the answer is that none of the below are acceptable, then please suggest a solution that preferably avoids the needs for barriers.

    1. EYS fittings will be installed at the location for each IS instrument and similarly for the conduit exiting the PLC panel. The fittings would be poured/sealed. Does the Z-Purge on the PLC panel eliminate the need for the sealed fittings?

    2. IS Barriers are installed within the PLC panel for each IS instrument. No seals are used for the conduit and wiring.

    3. Z-Purge on the PLC panel is sufficient. Seals or IS Barriers are not needed.

    Thank you,
    KCCA

  2. #2
    Join Date
    Dec 2011
    Location
    Ocala, Florida, USA
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    2,402
    Quote Originally Posted by kcca View Post
    The subject installation involves IS rated instruments that are physically located in a Class 1 Div 2 area. These instruments will be wired to a PLC panel that is outfitted with a Z-Purge system. The proposed wiring installation method is to run wiring between the PLC panel and the IS rated instruments. Can you advise as to which of the following methods are acceptable? If the answer is that none of the below are acceptable, then please suggest a solution that preferably avoids the needs for barriers.

    1. EYS fittings will be installed at the location for each IS instrument and similarly for the conduit exiting the PLC panel. The fittings would be poured/sealed. Does the Z-Purge on the PLC panel eliminate the need for the sealed fittings?

    2. IS Barriers are installed within the PLC panel for each IS instrument. No seals are used for the conduit and wiring.

    3. Z-Purge on the PLC panel is sufficient. Seals or IS Barriers are not needed.

    Thank you,
    KCCA
    I assume from your post that the PLC panel is in the Class 1 Div 2 area. If so, then no seals are going to be required and in fact the wiring can be in FMC even. They probably want a seal at the PLC panel to block the purge gasses though.


    I know what I don't know, and I know where to go to find it!

  3. #3
    Join Date
    Apr 2004
    Location
    Mission Viejo, CA
    Posts
    4,935
    Quote Originally Posted by kcca View Post
    The subject installation involves IS rated instruments that are physically located in a Class 1 Div 2 area. These instruments will be wired to a PLC panel that is outfitted with a Z-Purge system. The proposed wiring installation method is to run wiring between the PLC panel and the IS rated instruments. Can you advise as to which of the following methods are acceptable? If the answer is that none of the below are acceptable, then please suggest a solution that preferably avoids the needs for barriers.
    1. EYS fittings will be installed at the location for each IS instrument and similarly for the conduit exiting the PLC panel. The fittings would be poured/sealed. Does the Z-Purge on the PLC panel eliminate the need for the sealed fittings?

    2. IS Barriers are installed within the PLC panel for each IS instrument. No seals are used for the conduit and wiring.

    3. Z-Purge on the PLC panel is sufficient. Seals or IS Barriers are not needed.

    Thank you,
    KCCA
    I apologize for the late response, but the meds I’ve been on this last week could get me a AUI (Answering Under the Influence)

    I should make a few comments:

    1. Without a control drawing [Sections 501.10(B)(3) or 504.10(A)] you do not have an NI or IS System no matter how the instruments are rated.
    2. An EYS seal mandates it is an explosionproof seal under both Sections 110.3(B) and 501.15(C) since the compound is required under the EYS listing. An explosionproof seal for a non-explosionproof enclosure is worthless.
    3. Pressurizing the PLC does benefit the enclosure AND it does not require an explosionproof seal assuming the “boundary” is the PLC exterior. See the last sentence of Section 501.15(B) and its Exception No. 3. However, it does nothing for the instruments themselves.

    SO basically,
    · Pressurizing the PLC is fine
    · No seals are required for the PLC, but may be beneficial to maintain pressure.
    · The instruments will still need some recognized form of protection technique apart from pressurizing the PLC.
    · If you choose an NI or IS protection technique, you need a control drawing.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

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