Question on NEC 110.14(C)(1) and 310.15(B)(3)(a)/310.15(B)(16) adjustments

[AH64ID]

Hello All,

I am working on a wiring project and have a quick question. I have been researching and come up with several different answers.

Little background. I am working off the 2014 NEC, using all 60°/75° or 75° terminals, and 90° THHN 10/12ga wire.

I have a 1" PVC conduit under my slab that I have ran 18 wires thru (17-12 ga and 1-10 ga common ground for 74% of my allowable fill ). All but 2 of the wires are for 3-way light switches and the last two are for a separate light circuit. The way I have it wired I have 11 CCC's (using the note about travelers in 310.15(B)(3)(a)) in the conduit which puts me to the 50% derate category of 310.15(B)(3)(a).

Now for the question. According to 110.14(C)(1)(a)(3) I am allowed to use the 75° column for my total ratings, but I am unclear on what to use for adjustment ratings.

In 110.14(C)(1) it states "Conductors with temperature ratings higher than specified for terminations shall be permitted to be used for ampacity adjustment, correction, or both."

Does this allow me to use the 90° column for the CCC derate, as long as I am not above the non-adjusted 75° ampacity rating?

What I want to do is use 15A breakers for each of the 4 light circuits that has wires in the conduit. Is that acceptable?

Thank you.

Apologize for a duplicate thread. It seemed that the NEC forum was the appropriate location to post a NEC question, but I gather that was wrong.

 

[augie47]

Unfortunately, the location of the earlier question was not the problem. The Forum rules do not permit "homeowner type questions".
I am closing this thread, in accordance with the Forum rules. This Forum is intended to assist professional electricians, inspectors, engineers, and other members of the electrical industry in the performance of their job-related tasks. However, if you are not an electrician or an electrical contractor, then we are not permitted to help you perform your own electrical installation work.


If I have misjudged the situation, if for example this project is related to your work, then send me a Private Message. If you can show me that I am wrong, and that you are a licensed electrician (or at least a licensed apprentice), then I will reopen your post, and offer an apology for the delay and inconvenience.

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[Dennis Alwon]

I am closing this thread, in accordance with the Forum Rules.

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