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Thread: Risers and Strain Relief

  1. #1
    Join Date
    Aug 2017
    Location
    Florida
    Posts
    10

    Risers and Strain Relief

    I'm running riser cables from the 1st floor distribution panels to the 3rd floor panels of a parking garage. The plan is two run two 4" RMC conduits into a 24"W x 32"H pull box on the third floor. I used the 8x rule for sizing straight run pull box per NEC 314.28. Each 4" conduit will contain 8#1/0 , 2#6 wires (two circuits with 4 conductors and a ground ea.). I was planning on using Kellems grips to support each circuit and as way to separate them. The ones that look like a Chinese finger trap... Is there pull box you can order that comes with hooks already installed to hang the eye of the kellems grip on? Is there a better means to support the cables other than kellems grips? I looked into the chalks it doesn't seem pratical for this application. Also looked into support cleats but not sure how this would work with some many conductors in the pull box. Also if I'm missing a detail please let me know. Thanks for the help!

  2. #2
    Join Date
    Jul 2003
    Location
    New Jersey
    Posts
    23,942
    Kellems work but in my experience you should make the box nearly twice as long as the code minimum because they require quite a bit of vertical room. We always use chocks and chock bushings but for 10 conductors that might be a problem. When using Kellem grips we install our own support (eyebolt) either in the top or the back of the box.
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

  3. #3
    Join Date
    Dec 2008
    Posts
    471
    I never used a common pull-box for cables in conduit. The last I designed -I hope it has been executed since no comment I received yet- was 10 RMC conduits of 3” from the ground to about 1000 ft-on a power-plant chimney.[all 100 ft. conduit pull box with Kellems strain relief grips].We used here conduits in order to avoid [fire] chimney effect.
    They are expensive [and including conduit oulet [pull boxes] also].
    For precipitator where there is an open air installation we used cable riser and Kellems cable support grips. The riser front is closed about 7 ft. from the floor and the floor is sealed with a kind of fire-stop. The front cover could be detached if necessary. All 100 ft[ about] a grips eye hanging device is fitted 4 ft. above the floor .

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