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Thread: what is MCM?

  1. #1
    Join Date
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    what is MCM?

    I'm looking at a set of plans where it is proposed to install 4-500 MCM THHN CU conductors in a 3 -1/2" conduit, which I presume will be RMC. I'm familiar with AWG and KCMIL, but MCM is new to me.

  2. #2
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    MCM is precisely the same as KCMIL. It is the older version. I believe the initial "M" comes from the Roman numeral that represents 1000. Some have said that it comes from the French word, "Mille," which also means 1000.

    Welcome to the forum.
    Charles E. Beck, P.E., Seattle
    Comments based on 2014 NEC unless otherwise noted.

  3. #3
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    Thanks Charlie B

    That's what I suspected, but thought I'd better be sure.

  4. #4
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    Thumbs down I am getting old!

    I can't believe kcmil has been around so long that some people do not know what MCM means. This is a mix of Roman Numerals and abbreviations, M = 1000, C = circular, and the second M = mils (0.001 diameter). I am getting old right before my eyes! :rolleyes:
    Charlie Eldridge, Indianapolis, Utility Power Guy
    Responses based on the 2011 NEC, unless stated otherwise.

  5. #5
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    Quote Originally Posted by charlie View Post
    I can't believe kcmil has been around so long that some people do not know what MCM means. This is a mix of Roman Numerals and abbreviations, M = 1000, C = circular, and the second M = mils (0.001 diameter). I am getting old right before my eyes! :rolleyes:

    If it makes you feel better, T310.16 used MCM up through the '87. In the '90, it was changed to KCMIL.

  6. #6
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    Quote Originally Posted by 480sparky View Post
    If it makes you feel better, T310.16 used MCM up through the '87. In the '90, it was changed to KCMIL.
    In '87 I was in the 2nd grade. By '90, I had made it all the way to 5th grade. If it didn't have to do with Legos or Transformers (the robots, not the electromagnetic devices) I didn't care about it. However, the wire manufacturer that I worked for up until mid-November used MCM even more than kcmil, so I don't have any problem with either of them.

  7. #7
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    It makes me feel old and I am only 29. It took me time to get MCM out of my head, and get use to Kcmills.
    Make something idiot proof and someone will make a better idiot.

  8. #8
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    Quote Originally Posted by mikeames View Post
    It makes me feel old and I am only 29. It took me time to get MCM out of my head, and get use to Kcmills.
    Now you need to let loose of 'fixture' and substitute 'luminaire'.

  9. #9
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    Quote Originally Posted by 480sparky View Post
    Now you need to let loose of 'fixture' and substitute 'luminaire'.
    Probably not going to happen but some one nailed me one time when I called a 8 foot t-12 lamp a "bulb" so now when I discuss lamps and bulbs I stop to think who I am talking to. If I am talking to a tradesman then I use the correct name. If it anyone else then I call everything (HID lamps, flourescent lamps, or an A19 bulb) light bulbs so I don't confuse them.

    I need to go re-lamp some 'luminaires'
    Make something idiot proof and someone will make a better idiot.

  10. #10
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    Some have said that it comes from the French word, "Mille," which also means 1000.
    That I had not heard INTERESTING.
    Brian John
    Leesburg, VA

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