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Thread: Deflection couplings

  1. #1
    Join Date
    Oct 2007
    Location
    Massachusetts
    Posts
    113

    Deflection couplings

    I have a 250' run of 3" emt conduit outside on a wall of a building . The conduit runs over (10) 3/4" structure joint.
    I am having a hard time finding a listed deflection coupling listed for EMT. They are listed for PVC or RMC but none for EMT .
    Plus they are $350 + each
    Can i use short pieces of liquid tight for this application ?
    A 3/4" structural joint should only need a foot of liquid tight i would think.

  2. #2
    Join Date
    Apr 2006
    Location
    Springfield, MA, USA
    Posts
    2,968
    Listed schmisted.

    http://www.homedepot.com/p/Fernco-3-...0-33/203310961

    *grin*

    (Tongue firmly in cheek)

    Seriously, this has been discussed several times, google is your friend:
    http://forums.mikeholt.com/showthread.php?t=175409
    http://forums.mikeholt.com/showthread.php?t=140164

    Which pointed to this resource:
    http://www.cooperindustries.com/cont...resources.html

    Only $600 each (gaak)
    http://www.newark.com/crouse-hinds/x...eel/dp/38X5685

    It appears that most of the difficulty and expense with these fittings is to create something that provides proper ground bonding and also is internally smooth to permit cable pull, even as everything moves.

    -Jon

  3. #3
    Join Date
    Aug 2013
    Location
    New York, NY
    Posts
    396
    Quote Originally Posted by winnie View Post
    Listed schmisted.

    http://www.homedepot.com/p/Fernco-3-...0-33/203310961

    *grin*

    (Tongue firmly in cheek)

    Seriously, this has been discussed several times, google is your friend:
    http://forums.mikeholt.com/showthread.php?t=175409
    http://forums.mikeholt.com/showthread.php?t=140164

    Which pointed to this resource:
    http://www.cooperindustries.com/cont...resources.html

    Only $600 each (gaak)
    http://www.newark.com/crouse-hinds/x...eel/dp/38X5685

    It appears that most of the difficulty and expense with these fittings is to create something that provides proper ground bonding and also is internally smooth to permit cable pull, even as everything moves.

    -Jon
    A slightly less sucky price:

    http://www.galco.com/buy/Crouse-Hinds/XJG84-EMT



    SceneryDriver

  4. #4
    Join Date
    Sep 2016
    Location
    Longmont, CO
    Posts
    167
    Seems like you could run the conduit on Unistrut and avoid the issue.

  5. #5
    Join Date
    Dec 2007
    Location
    NE Nebraska
    Posts
    33,092
    Quote Originally Posted by Jim1959 View Post
    Seems like you could run the conduit on Unistrut and avoid the issue.
    If the strut is securely fastened to both sides of the building expansion joint and the conduit is securely clamped to the strut, what happens when there is movement between each side of the expansion joint?

  6. #6
    Join Date
    Jun 2003
    Location
    NE (9.1 miles @5.07 Degrees from Winged Horses)
    Posts
    8,756
    Use PVC expansion joints with external bonding jumpers?
    Tom
    TBLO

  7. #7
    Join Date
    Jun 2004
    Location
    Cherry Valley NY, Seattle, WA
    Posts
    3,178
    Is this truly an expansion joint that is likely to move? What type of construction is it? Sometimes I see "joints" that I think are just "sections" and not likely to move...
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

  8. #8
    Join Date
    Dec 2006
    Location
    Eastern Oregon
    Posts
    3,391
    Quote Originally Posted by pgordon View Post
    I have a 250' run of 3" emt conduit outside on a wall of a building . The conduit runs over (10) 3/4" structure joint.
    I am having a hard time finding a listed deflection coupling listed for EMT. They are listed for PVC or RMC but none for EMT .
    Plus they are $350 + each
    Can i use short pieces of liquid tight for this application ?
    A 3/4" structural joint should only need a foot of liquid tight i would think.
    You're going to spend more than $350 in LFMC 3" connectors, LFMC, rigid couplings, and raintight connectors just to make a LFMC transition. That's not counting all the labor to put it together either.

    I'm curious if you couldn't just use those B-Line strut straps made to allow for a slip fit?

  9. #9
    Join Date
    Jun 2006
    Location
    Ohio
    Posts
    21,259
    Quote Originally Posted by Cow View Post
    ...
    I'm curious if you couldn't just use those B-Line strut straps made to allow for a slip fit?
    The physics says you can with just one expansion joint if that is all that is needed... but Code implies you have to use a listed fitting for each joint [300.4(H)].

    Best to contact AHJ to get preapproval (in writing).
    Last edited by Smart $; 10-10-17 at 11:28 PM.
    I will have achieved my life's goal if I die with a smile on my face.

  10. #10
    Join Date
    Jul 2005
    Posts
    756
    Is this a tilt wall structure?

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