Nor would I want you to. FWIW, I respect your sticking to your beliefs. :thumbsup:
Likewise
The point was that 110.14(C)(1) second sentence specifically says to base determination on Table 310.15(B)(16) as appropriately modified by 310.15(B)(6). It does not say to do so by way of 215.2(A)(1) [or 210.19(A)(1), but will continue to refer to both as 215.2 for this discussion].
110.14(C)(1) says the conductor ampacities used in the determination should be based no Table 310.15(B)(16). (As an aside, I will point out here, that Table 310.15(B)(16) is a Table for "Allowable Ampacities" - but you do not feel that 110.14(C) applies to "Allowable Ampacities".)
Of course it does not say to do so by way of 215.2(A)(1). As has been pointed out, and we have both been in agreement, 215.2 doesn't have anything to do with the ampacity of a conductor, only with determining what the minimum ampacity of a conductor needs to be for the given feeder, and what the minimum conductor size needs to be for the given feeder.
In other words I'm questioning where the code says to use noncontinuous load plus 125% continuous load for the purpose of 110.14(C) determination. You previously answered this question "Why would I not?" I do not recognize that as a legitimate answer.
Would you accept "Because the Code requires me to" as a legitimate answer? 110.14(C) says that the temperature rating associated with the ampacity of a conductor shall be selected an coordinated so as not to exceed the lowest temperature rating of any connected device. The second sentence of 215.2(A)(1) establishes a minimum conductor size based on an ampacity of a conductor which is not less than the non-continuous load plus 125% of the continuous load. The temperature rating associated with the required ampacity from second sentence of 215.2(A)(1) must be
75?C if the devices/terminations are rated for
75?C.
I see two parts to 215.2(A)(1):...and...The first part requires the ampacity (which I assume to be the final derated ampacity) to be not less than the calculated load. There is no extra 25% inclusion for continuous loads.
The second part requires the allowable ampacity, before the application of any adjustment or correction factors, to be not less than an extra 25% for continuous loads.
110.14(C) uses the term ampacity, which is used in the first part of 215.2(A)(1). 110.14(C) does not use the term allowable ampacity, which in 215.2(A)(1) is only used in the second part.
The Code only gives one definition for
ampacity. An "allowable ampacity" is undoubtedly an
ampacity.
If we are basing 110.14(C) determination on Table 310.15(B)(16) by way of 215.2(A)(1), what makes the second part predominant over the first part???
There is no predominance of one part of 215.2(A)(1) over another.
BOTH parts of 215.2(A)(1) must comply with 110.14(C) in the
same manner. Both parts of 215.2(A)(1) establish a minimum ampacity ("ampacity not less than".) The first part establishes an ampacity to ensure that the conductor can supply the load. The second part establishes an ampacity to provide for a minimum conductor size. 110.14(C) (which is a General Requirement of the Code) requires that the
temperature rating associated with the ampacity of a conductor shall be
75?C if the lowest rating of any connected device, conductor or termination is
75?C.
As I stated before, the step where I used 2 sets of 400kcmil at their 760A combined ampacity rating was for verifying compliance with 215.2(A)(1), which has no stipulation that 110.14(C) requirements must be combined in this verification. If you have any gripe whatsoever with my steps, based on what you are trying to point out, it would be with my first step verifying compliance with 110.14(C).
Yes, my gripe is with the way you are trying to seek compliance with 110.14(C). (I guess you could say that that makes my gripe with your first step, but it is also clearly with your second step.) You are applying 110.14(C) to determine a minimum conductor size. There is
NOTHING in 110.14(C) about determining a minimum conductor size. As we have seen, the second part of 215.2(A)(1) establishes a minimum conductor size, and the first part of 215.2(A)(1) establishes a minimum ampacity for a feeder (which may require a larger conductor than the established minimum conductor size.)
To comply with 110.14(C), you must establish the temperature rating that is to be associated with the ampacity of a conductor. And the temperature rating must not exceed the lowest rating of any connected device, termination or conductor. If I have terminations rated
75?C on my feeder, and I select an ampacity of a given conductor size associated with the
90?C rating of the conductor insulation, then I have just violated 110.14(C).
I'm agreeable to the result(s) you've established here, but I notice you use the calculated load of 650A as a basis of determination. Why use it here and not for 110.14(C)???
I
HAVE used the calculated load here together with 110.14(C). In fact, my determination of the need for either parallel 600mcm THWN or 500mcm THWN-2 is
DIRECTLY from 110.14(C). I have determined that parallel sets of 500mcm THWN-2 will have an ampacity that is too small for the load. I would either have to use a larger conductor (the parallel 600mcm is large enough to supply the load)
OR using
110.14(C)
Conductors with temperature ratings higher than specified for termination provisions shall be permitted to be used for ampacity adjustment, correction, or both.
I can use parallel 500mcm THWN-2.
FWIW, I've searched the internet for articles relating to this matter. The ones that deal with continuous loading do follow the method you are using. I've not found any that support my method conclusively. However, I found a bevy of articles that to my mind seem to completely avoid the issue...
Here are a couple of more....
http://www.iaei.org/magazine/2003/07/sizing-conductors-for-all-load-conditions/
http://ecmweb.com/content/sizing-continuously-loaded-conductors-made-simple
The one from EC&M is interesting because it was written at the time the the Code was changed to introduce this language. It gives much better explanations of the 125% of continuous load rule than I can.
