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Thread: reducing size of circuit conductors to fit breaker lugs

  1. #1
    Join Date
    Mar 2009
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    reducing size of circuit conductors to fit breaker lugs

    a customer asked if it would be possible( legal, nec code) to use a 1000 foot roll of 350mcm he has already on stock, to act as the branch ciruit conductors that are fed from breakers who's lugs are sized to receive a 4/0 conductor.,The breakers , ranging in size from 200-400 amps , will act as a temporary switch board while we replace , update his main switch panels with new units. This would amount to a great cost savings to him, not having to purchase 1,000 feet of 4/0 thhn,

    But we would have to remove the outer ring of copper wires ( conductors) from the 350 mcm to fit into the lugs on the temporary switchboard panel breakers we've set up in an adjoining room. Is this legal under nec, are there any safety concerns, are we maintaining the proper amperage, current carrying capacity of the cables after removing enough of the individual copper strands of the 350 mcm to fit the breaker lugs which are maximum sized for 4/0 cable. Sorry this first post is so long, but we just want to do what's proper and correct practice.

  2. #2
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    It would be legal to splice a short piece of 4/o to the ends . But IMO not to cut stands off the 350. Though I have probably done it.:wink: Esspecially if it is temporary.

  3. #3
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    Try macadapts. They are exactly for the purpose you describe. Some are offset to fit onto small breakers.

    They are not free like the 350 kcmil, but they will ensure code compliance. I try to install "temporary" like it 's going to be there awhile.
    Last edited by jeremysterling; 03-23-09 at 08:42 PM. Reason: clarity

  4. #4
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    Welcome to the Forum. Several companies make reducing connectors for this type of installation. One company is ILSCO. Take note of the CMP-350 line. Look them up on the web at:

    http://ebusiness.ilsco.com/webapp/wc...categoryId=104
    Kevin

    Certified Electrical Inspector/Former E.C.

  5. #5
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    No not legal to cut strands but you could splice or use a compress fitting. If by temp you mean a few days then i think i would risk cutting strands.

  6. #6
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    From the OP's post, it would seem the work on equipment is temorary, but the installation of the conductors is permanent.

    Cutting the strands is not permitted, even for temporary conditions.
    Instructor, Industry Advocate

  7. #7
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    I wouldnt cut the strands, I wouldnt want the liability in the event of a failure. The pins cant cost that much......

  8. #8
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    oldrediron

    thanks so much for the quick and informative posts, i will do as you have suggested, purchase either the ilsco cpm-350 adapter lugs or splice a piece of 4/0 via compression lugs with proper reducer bushings onto the 350 mcm.
    short cuts usually lead to shorts, as one of my apprenticeship instructors said often.

  9. #9
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    Quote Originally Posted by wireguru View Post
    I wouldnt cut the strands, I wouldnt want the liability in the event of a failure. The pins cant cost that much......
    Short of having pins on hand or obtainable within a day or two, depending on the necessity of getting the temp conneciton up and running, we (trying to cast balame on others rather than myself ) have cut off strands. Yet on occasions where we thought it may be a problem, we cut a compression barrel splice (or lug) in half, and compress one of the halves on each end, over the full complement of strands, cut off the required number of strands, then insulate the half barrel with rubber and vinyl tapes. IMO, the result is electrically better than both a pin reducer and a reducing splice.

    BTW, I just did a quick calculation on the number of strands that can be cut off and retain a cross section equal or better than 4/0. If the 350 is Class "B" stranding it will have 37 equal-size strands. 23 need to remain for the 4/0 equivalent.

  10. #10
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    If only temp why not polaris blocks and after the job is over you still have them just as good as new.

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