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Thread: SER Romex same thing for ampacity? TW

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    SER Romex same thing for ampacity? TW

    I know we use the 60c column for romex and conductors TW or UF from table 310.15(B)(16) 2014 NEC and when equipment terminals are rated 100A or less 14 AWG through 1 AWG
    110.14 (C)(1)(a).
    My question is two parts what does TW stand for? And, can SER cable be sized using the 75c column the gray SER cable I believe is marked XHHW, or is SER sized using the 60c column? Thanks

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    Quote Originally Posted by zcanyonboltz View Post
    My question is two parts what does TW stand for? And, can SER cable be sized using the 75c column the gray SER cable I believe is marked XHHW, or is SER sized using the 60c column? Thanks

    TW-- thermoplastic and water resistant.

    As far as the ser being used at 60C or 75C depends on what code cycle you are using and what is the conditions of the install

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    TW is an insulation type and being a 60 degree C conductor is can only be used at
    its 60 degree ampacity regardless of size.
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

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    Quote Originally Posted by Dennis Alwon View Post
    TW-- thermoplastic and water resistant.

    As far as the ser being used at 60C or 75C depends on what code cycle you are using and what is the conditions of the install
    The NEC cycle is 2014 the terminations are rated over 100A. 4/0 Aluminum XHHW is rated to 150A in the 60c 180A in the 75c column and 205A in the 90c column.
    Every company I have ever worked for pulls 4/0 to a 200A panel.

    2/0 Aluminum is 115A 60c,135A 75c and 150A 90c. We always pull 2/0 to a 150 panel. This said we pulling wire based on the 90c column. The only reason I see that we do this legally is that the SER is XHHW-2 and all terminals are rated to 90c. What my hang up is that I was taught to always size romex to 60c.

    So I guess my question is SER is NOT Romex right?

  5. #5
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    Quote Originally Posted by zcanyonboltz View Post
    SER is NOT Romex right?
    Right, however:

    338.10(B)(4)(a)

    (4) Installation Methods for Branch Circuits and Feeders.

    (a) Interior Installations. In addition to the provisions of
    this article, Type SE service-entrance cable used for interior
    wiring shall comply with the installation requirements of Part II
    of Article 334
    , excluding 334.80.
    Where installed in thermal insulation the ampacity shall
    be in accordance with the 60C
    (140F) conductor temperature
    rating. The maximum conductor temperature rating shall be
    permitted to be used for ampacity adjustment and correction
    purposes, if the final derated ampacity does not exceed that for
    a 60C (140F) rated conductor.

    #PrudentPrePlannigPreventsPissPoorPerformance

  6. #6
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    Quote Originally Posted by zcanyonboltz View Post
    The NEC cycle is 2014 the terminations are rated over 100A. 4/0 Aluminum XHHW is rated to 150A in the 60c 180A in the 75c column and 205A in the 90c column.
    Every company I have ever worked for pulls 4/0 to a 200A panel.

    2/0 Aluminum is 115A 60c,135A 75c and 150A 90c. We always pull 2/0 to a 150 panel. This said we pulling wire based on the 90c column. The only reason I see that we do this legally is that the SER is XHHW-2 and all terminals are rated to 90c. What my hang up is that I was taught to always size romex to 60c.

    So I guess my question is SER is NOT Romex right?
    The "next size up rule" comes into play too which is why you see often see SER protected above its ampacity, or the "residential sizes" seemingly being used when it shouldnt. Under 2014, SER can be used at 75 degrees if not installed in thermal insulation.
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

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    Quote Originally Posted by zcanyonboltz View Post

    2/0 Aluminum is 115A 60c,135A 75c and 150A 90c. We always pull 2/0 to a 150 panel. This said we pulling wire based on the 90c column. The only reason I see that we do this legally is that the SER is XHHW-2 and all terminals are rated to 90c. What my hang up is that I was taught to always size romex to 60c.

    So I guess my question is SER is NOT Romex right?
    "Romex" is type NM cable, SER is type SE cable. You can use NM at its 60 degree C ampacity only. For SE cable the maximum is at its 75 degree C ampacity. Neither cable type can be used at 90 degrees C.
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

  8. #8
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    Quote Originally Posted by electrofelon View Post
    The "next size up rule" comes into play too which is why you see often see SER protected above its ampacity, or the "residential sizes" seemingly being used when it shouldnt. Under 2014, SER can be used at 75 degrees if not installed in thermal insulation.
    Thanks for the replies the next size up makes sense.

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