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Thread: terminal temperature rating

  1. #31
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    Quote Originally Posted by augie47 View Post
    Jumper,
    excuse my thickheadness... can you try to get it through that thick head again why 41.6 is incorrect under the '11 Code since we are only asking for conductor ampacity and there is no mention of terminations,.
    (I got lost in your earlier posts)
    Since the reference to 110.14(C) is no longer a FPN and is now a part of 310.15(B), the terminals are included in using the chart.

    You cannot use the multiplier to get 41.6 without agreeing to max out at possible highest terminal rating.

    It was an indirect route before, now explicitly mandated.

    Since a 75C termination was not mentioned, I do not have to limit the conductor to that rating, 90C is allowed. 40A. Same as conductor ampacity.
    "Electricity is really just organized lightning." George Carlin


    Derek

  2. #32
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    thickheadedness

    well, I do believe you've seen my photo, the one of the post office wall with a head so thick the oaks hang their limbs in shame.

    As to your getting lost above, might point is quite simple. if the henry's wish to utilize anything in addition to 310.15 B 16, then
    it's inconsistent to not consider 110.14 C just as much as an ambient adjustment table.

    As to your point about pre 2014 and 110.14 C, I stand corrected and thanks for steering me right. The 30+ years I contracted in several different states, each with several and some, many more AHJs. All the inspectors I ever worked with preferred we work conservatively when it came to loading wires run through pipe. I have made that approach my own. I taught it to my apprentices and I teach it now to my students.

  3. #33
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    Quote Originally Posted by ohmboyz View Post
    well, I do believe you've seen my photo, the one of the post office wall with a head so thick the oaks hang their limbs in shame.

    As to your getting lost above, might point is quite simple. if the henry's wish to utilize anything in addition to 310.15 B 16, then
    it's inconsistent to not consider 110.14 C just as much as an ambient adjustment table.

    As to your point about pre 2014 and 110.14 C, I stand corrected and thanks for steering me right. The 30+ years I contracted in several different states, each with several and some, many more AHJs. All the inspectors I ever worked with preferred we work conservatively when it came to loading wires run through pipe. I have made that approach my own. I taught it to my apprentices and I teach it now to my students.
    It is all really a matter of nitpicking the exact steps of what is exactly required at what stage.

    The end result will end up being the same number, so in the big picture as long as the correct conductor is chosen and protected properly it is not a big deal.
    "Electricity is really just organized lightning." George Carlin


    Derek

  4. #34
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    That's the trouble with exam questions; in an exam the scenario described can never be as detailed and consistent as what one would encounter in a real world situation. In this case, you have to consider CCC in conduit and ambient temperature derates because the pertinent conditions were explicitly called out. Terminal max temperatures were not, so do you consider them? I believe you could make a case either way, but it's a meaningless exercise because the point isn't to choose the best conductor but to get into the head of the author of the question and come up with the same answer he did in order to get the "correct" answer so that you pass the exam.

    Exam world: What is the minimum size conductor you may use in <insert description of conditions>?
    Real world: Can I use some of the buttload of #10 THWN-2 that I have in the truck?

  5. #35
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    Quote Originally Posted by ggunn View Post
    That's the trouble with exam questions; in an exam the scenario described can never be as detailed and consistent as what one would encounter in a real world situation. In this case, you have to consider CCC in conduit and ambient temperature derates because the pertinent conditions were explicitly called out. Terminal max temperatures were not, so do you consider them? I believe you could make a case either way, but it's a meaningless exercise because the point isn't to choose the best conductor but to get into the head of the author of the question and come up with the same answer he did in order to get the "correct" answer so that you pass the exam.

    Exam world: What is the minimum size conductor you may use in <insert description of conditions>?
    Real world: Can I use some of the buttload of #10 THWN-2 that I have in the truck?
    The worst thing about the question IMO was using the temperature factor of 70F to have an adjusted ampacity of 41.6, but then not derating because of only 3 CCCs.

    Somewhat of a pointless exercise IMO. The additional temperature allowances added after 1999, not sure when they were added, which do not decrease the ampacity-but increase it, were meant to offset the other derating/correction factors.

    It was never intended for one to think that a 40A conductor was going to increase to 41.6A and be done.

    When one leaves 310.15 and heads to 110.14 to factor in for terminal rating the ampacity is gonna be equal to or less than what was chosen from 310.15(B)(16) to start.
    "Electricity is really just organized lightning." George Carlin


    Derek

  6. #36
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    Quote Originally Posted by jumper View Post
    The worst thing about the question IMO was using the temperature factor of 70F to have an adjusted ampacity of 41.6, but then not derating because of only 3 CCCs.

    Somewhat of a pointless exercise IMO. The additional temperature allowances added after 1999, not sure when they were added, which do not decrease the ampacity-but increase it, were meant to offset the other derating/correction factors.

    It was never intended for one to think that a 40A conductor was going to increase to 41.6A and be done.

    When one leaves 310.15 and heads to 110.14 to factor in for terminal rating the ampacity is gonna be equal to or less than what was chosen from 310.15(B)(16) to start.
    I think that's making way too much of it. It seems to me that the point of the exercise was simply to show the two deratings and that one of them made a change to the conductor ampacity and the other didn't. There is no doubt in my mind that the majority of us are capable of doing the right thing in a real world situation, but this ain't it.

  7. #37
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    The question is only asking for the ampacity of the wire, not what is used for or going to. you need to remember to read the questions and answer them as asked.
    Quote Originally Posted by jumper View Post
    l just looked. The temperature correction factor for 70F is 1.04.

    40 x 1.04 = 41.6.

    This could be used for calculating when derating or other purposes but even using 90C terminals the ampacity is 40 IMO. I do not think you could be a 41A load on the conductor.

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