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Thread: what do the wire types mean

  1. #1
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    what do the wire types mean

    I am trying to find out what is different about the different types of wire. Example the difference between size 14 AWG Type TW and size 14 Type THHN. Where can I get this type of information?

  2. #2
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    Re: what do the wire types mean

    Table 310.13 Conductor Application and Insulations

    TW for example is Flame- retardant, moisture -resistant thermoplastic. For dry or wet locations, with a maximum operating temp of 60 C

    THHN is Flame- retardant, heat-resistant thermoplastic for dry or damp locations with a maximum operating temp of 90 C

  3. #3
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    Re: what do the wire types mean

    There is a pretty significant difference in size between TW and THHN as well. TW is pretty tough to pull and almost never seen anymore in new installations.

  4. #4
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    Re: what do the wire types mean

    The letters describe the type and rating of the insulation. The “T” stands for “thermoplastic.” It is good for a 60 degree C temperature rise, with an ambient temperature of 30C. The “H” stands for “add one measure of heat.” It means that you add 15 degrees C to the temperature rating. So a “T” is good for 60C, a “TH” is good for 75C, and a “THH” is good for 90C. The “W” stands for “wet,” and tells you the conductor can withstand a wet environment.

    The “AWG” stands for “American Wire Gauge.” The bigger the number, the smaller the wire. For example, most household circuits will use a #12. A #14 is smaller than this, and a #10 is bigger. The size of the wire is related to the amount of current it can safely carry. The larger the wire, the more current.
    Charles E. Beck, P.E., Seattle
    Comments based on 2014 NEC unless otherwise noted.

  5. #5
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    Re: what do the wire types mean

    To add to what Charlie said, R is for thermoset rubber, and -2 is another heat measure. For example a cable listed RHW-2 is ruber insulated, 90 degree, wet or dry locations.

    X is another designation for for cross-linked thermoset plastic for example XHHW-2 would be Cross-Linked synthetic polymer rated for 90 degrees is wet locations.

    It is a little confusing at times. But genneraly the first letter or two designate the insulation type followed by heat a water designation, but not always. For example FEP and FEPB is Fluorinated Ethylene Propylene (Teflon) 90 and 200 degree respectively, dry and damp locations.

  6. #6
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    Re: what do the wire types mean

    Oh, and the "N" in "THHN" stands for a neoprene jacket.
    Charles E. Beck, P.E., Seattle
    Comments based on 2014 NEC unless otherwise noted.

  7. #7
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    Re: what do the wire types mean

    Originally posted by charlie b:
    Oh, and the "N" in "THHN" stands for a neoprene jacket.
    Nylon?

  8. #8
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    Re: what do the wire types mean

    Oops! Yes, it is nylon. Should not have gone from memory, for tis the memory that is gone.
    Charles E. Beck, P.E., Seattle
    Comments based on 2014 NEC unless otherwise noted.

  9. #9
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    Re: what do the wire types mean

    Too much radiation, Charlie.
    (inside, joke Charlie and I both worked in the navy nuclear program)
    Moderator-Washington State
    Ancora Imparo

  10. #10
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    Re: what do the wire types mean

    I hope you both wore your dosimeter everyday. I had mine on all the time with the nuclear weapons.
    Charlie Eldridge, Indianapolis, Utility Power Guy
    Responses based on the 2011 NEC, unless stated otherwise.

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