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Thread: Clearance 480 Volt ?

  1. #1
    Join Date
    Jul 2008
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    Clearance 480 Volt ?

    Installing a air compressor that is about 10 ft by 6 ft on a metal skid . The controller cabinet is 3 ft in front of a concrete block wall . I told my boss it needs 3 ft 6 " from the face of the panel to the block wall . He says no he wants it installed at 3 ft . I said I understand the code calls for 3' ft 6 " from the face of the cabinet . Its a 2 X 3 ft controller cabinet with 200 HP motor 480 volt feed . If you open the cabinet any live parts are 3 ft 7" from the block wall . Would you push the issue or leave it as it is ???

  2. #2
    Join Date
    Dec 2010
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    1,291
    Quote Originally Posted by Davebones View Post
    I said I understand the code calls for 3' ft 6 " from the face of the cabinet .
    That's correct. If it is 3'1" you could install insulating panels.
    The more they overthink the plumbing, the easier it is to stop up the drain

  3. #3
    Join Date
    Jul 2006
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    San Francisco, CA, USA
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    To that point:

    Table 110.26(A)(1)
    Condition 2:... Concrete, brick, or tile walls shall be considered as grounded.
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  4. #4
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    As mentioned you could cover that section of the wall with an insulating material. If indoors a glued up layer of drywall would do.
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

  5. #5
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    Quote Originally Posted by infinity View Post
    As mentioned you could cover that section of the wall with an insulating material. If indoors a glued up layer of drywall would do.
    I just ran into that on an MV project just last week. The contractor bidding the job was going to put up a corrugated steel wall at 6ft from the front of the gear, but it would interfere with an equipment access hatch. I told him he could put up a stick wall with sheetrock at 3' (it's 2400V). But they used some leftover concrete tile backer board over the stick frame because they already had it. Then the AJH called it concrete and the distance became a problem. So I had them put sheetrock on top of the tile backer with Liquid Nails, the AHJ was fine with it. Ultimately they paid MORE than if they had just stuck to the sheetrock to begin with of course...
    __________________________________________________ ____________________________
    Many people are shocked when they discover I am not a good electrician...

  6. #6
    Join Date
    May 2011
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    CA
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    Quote Originally Posted by Davebones View Post
    If you open the cabinet any live parts are 3 ft 7" from the block wall
    110.26(A)(1): "distances shall be measured from exposed live parts or from the enclosure or opening if the live parts are enclosed."

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