adjustment factors with voltage drop adjustments

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Electron_Sam78

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Palm Bay, FL
Ok I have a 3 phase, 4-wire, 208V, 440ft run with a 70 amp load and copper conductors. 2008 UGLY's voltage drop calculations (p. 50) say I need a #2 AWG copper conductor. Since there are 4 CCCs how/where do I fit in the 80% adjustment factor for 4-6 CCCs?:-?
 
Are you sure that the neutral is considered a current carrying conductor? Look at 310.15(B)(4)

Pete
 
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First of all, why do you think that there are four current-carrying conductors? In other words, why are you counting the neutral? Are there significant harmonics among the intended loads? If not, you only have three CCCs, and the derating factor of 80% does not apply.

But if you do have four CCCs, then you look up the ampacity of the #2 wire at its temperature rating (you didn't tell us what type of wire you are using). If for example you are using THHN, then at 90C the ampacity of a #2 is 130 amps. Multiply that by 80%, and you get 104. That is lower than the 75C rating of #2, so the ampacity limit is 104. Since your 70 amp load is below the ampacity of the conductor, you are good to go.
 
Actually in this particular case I don't think there are non-linear loads (just two 7.5 HP motors and some other minor loads) but the situation did get me thinking about applying the two aforementioned adjustment factors in the same instance and how it should be approached.

So Charlie, you're saying that if the CCC adjustment turns out to be a higher ampacity than the original load before voltage drop calculations then I'm good? Is there a source you can cite to confirm that information? Not that I don't believe you I just like to have verifiable sources for decisions about jobs I may be doing.
 
I am not sure I know which part it is for which you want to have a code citation. I infer this is a feeder you are discussing. 215.2(A)(1) says that a feeder conductor must have an ampacity greater than the calculated load. You have a calculated load of 70, and an ampacity of 104. That is all you need to be able to show.

Or are you asking for a citation related to the way I calculated the ampacity? That starts at table 310.16, factors in the derating rules of table 310.15(B)(2)(a), and uses 110.14(C) as the basis for starting the derating from the 90C value.
 
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