nec adjustment factors calculations

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he1029

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hi everyone just a little question over here about the 2 examples from nec table B.310.11
1)what is the difference between the 2 examples?
2)and clearly how do you calculate them maybe i didn't calculate them correctly?

Thank you so much with appreceation he
 
I'm going to start with two things:

(A) It's important to mention that you're refering to "ANNEX B".

(B) The difference between the two examples is this:

Example 1: refers to a raceway with 24 conductors, 12 of which are carrying current.

Example 2: refers to a raceway with 24 conductors, 18 of which are carrying current.

Let me know where you're at with this more specifically.
 
iwire said:
'Splain please?
Click to expand...
You got some splainin to do, Lucy! :roll:
  • They don't define or explain "load diversity," and it doesn't mesh with any standard term I can find in any of my textbooks.
  • I don't understand the difference between 9 conductors (without load diversity) and 10 conductors (with load diversity), and don't know why they both have a factor (in table B310.11) of 70%.
  • I don't know what factor to use, if I had 10 conductors, but didn't have load diversity.
  • If I had six wires in a conduit and only three can carry current at a time (there is a current thread with this situation), then do I have "load diversity" in the context of this Annex, and do I have to derate? If I used this Annex, and used the calculation method shown therein, my ampacity drops to 80%. But I don't think I have to derate, since I really only have 3 CCC's. So what does this Annex bring to the party?
  • Since it is in the Annex, I shouldn't be required to use it. But under what circumstances would I want to use it? None that I can name.
 
charlie b said:
You got some splainin to do, Lucy! :roll:
  • They don't define or explain "load diversity," and it doesn't mesh with any standard term I can find in any of my textbooks.
Click to expand...
That is why this information is in the Annex. It was in Article 310 for one code cycle, but with an effective date of 3 years in the future. It was moved to the Annex in the next code cycle, mostly because no on knew what "load diversity" is or how to apply it.
 
hi there thank you for replying, now i'm trying to see how to derate on a good and easy table how can you help me with that?
i work for an electrical co. in nyc area i'm working my way up started 21/2 years ago as a ruffer now i'm doing services (big ones 6000A ...) but the derating i'm not clear how to determin so i'm asking for help
 
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