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Thread: Do AHJs allow more than one Flexible Coupler/fitting in a Class I Div 1 area....

  1. #1
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    Do AHJs allow more than one Flexible Coupler/fitting in a Class I Div 1 area....

    The NEC handbook implies that the max length of a flexible coupling in a C1D1 area is limited to the 3 foot length (as restricted by UL1203)... but nothing in the NEC seems to clarify this.

    Has anyone ever had an installation that required someone to add a 12 or 24 foot flex coupler to a 36 inch coupler in the field ? Would an AHJ allow that in a C1D1 area ?

  2. #2
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    Quote Originally Posted by BrianPegg View Post
    The NEC handbook implies that the max length of a flexible coupling in a C1D1 area is limited to the 3 foot length (as restricted by UL1203)... but nothing in the NEC seems to clarify this.

    Has anyone ever had an installation that required someone to add a 12 or 24 foot flex coupler to a 36 inch coupler in the field ? Would an AHJ allow that in a C1D1 area ?
    The general restriction is Section 110.3(B).

    You can't get a manufacturer to make a listed explosionproof flexible coupling longer than 36".

    If you really need a flexible connection that long see Sections 501.10(2)(2) and 501.140.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  3. #3
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    I am guessing that the OP meant add 12 inch or 24 inch in line, not feet.
    With either a suitable coupling or an explosion proof box joining the two pieces would it comply with the letter of the Code?

  4. #4
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    Quote Originally Posted by GoldDigger View Post
    I am guessing that the OP meant add 12 inch or 24 inch in line, not feet.
    With either a suitable coupling or an explosion proof box joining the two pieces would it comply with the letter of the Code?
    The first thing to understand is explosionproof flexible couplings aren't all that "flexible" in the first place. They are primarily designed for vibration abatement.

    An intermediate explosionproof box would need to be supported. Don't know what a "suitable coupling" would be. Standard couplings would take a beating in a substantial vibration application.

    If he meant "inches" rather than "feet" - I'll let the OP clarify.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  5. #5
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    Quote Originally Posted by rbalex View Post
    The first thing to understand is explosionproof flexible couplings aren't all that "flexible" in the first place. They are primarily designed for vibration abatement.

    An intermediate explosionproof box would need to be supported. Don't know what a "suitable coupling" would be. Standard couplings would take a beating in a substantial vibration application.

    If he meant "inches" rather than "feet" - I'll let the OP clarify.
    I should add one positive benefit: explosionproof flexible couplings, installed within their listing, don't need auxiliary bonding as required by Section 501.30(B); i.e., they are NOT flexible metal conduits (FMC or LFMC), they are couplings.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  6. #6
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    It appears I've been in error. I checked with UL and certain manufacturers can fabricate listed explosionproof flexible couplings longer than 36"; possibly up to 144".

    Of course, they are incredibly expensive. It isn't called "golden rope" by the end-users for nothing.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  7. #7
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    Yes I meant 12 or 24 INCH extensions....

    Quote Originally Posted by rbalex View Post
    I should add one positive benefit: explosionproof flexible couplings, installed within their listing, don't need auxiliary bonding as required by Section 501.30(B); i.e., they are NOT flexible metal conduits (FMC or LFMC), they are couplings.
    Yes - feet was a mental typo...menat 12 or 24 INCH extension...

    THANK YOU rbalex... Very interesting info from the UL folks.. !!

    And it makes sense that if you tried to couple two couplers by attaching one male to one female , you would be concerned with them vibrating apart (due to the beating at the "movable" threaded joint)...

    I just could not find anything that specifically prohibits that in the code... (as my lawyer / uncle would say,, "it could be deemed allowable due to an absence of language to the contrary")..

    Thanks for all your comments folks !!
    BP

  8. #8
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    Quote Originally Posted by rbalex View Post
    The first thing to understand is explosionproof flexible couplings aren't all that "flexible" in the first place. They are primarily designed for vibration abatement.

    An intermediate explosionproof box would need to be supported. Don't know what a "suitable coupling" would be. Standard couplings would take a beating in a substantial vibration application.

    If he meant "inches" rather than "feet" - I'll let the OP clarify.
    You got that, brother. I thing they call them "flexible" because "barely deflects when stepped on by an elephant" takes to long to write.

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