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Tuesday, May 16, 2017

Question:

Re: CQD answer published Friday, May 5, 2017 -Ampacity 90 Degree Insulation

Thanks for the service that you provide for the industry. I believe that a clarification is needed for your answer to the Thursday May 4 question.  In your answer to the question regarding parallel service conductors you suggested using conductors rated at 90 degrees.  It is my understanding that the 90 degree rating may only be used if you know that the terminations are also rated 90 degrees per 210.14.  That is an important distinction that should be made.

Don Haskin

A

Answer:

Hey Don thanks for your comment and you are welcome. Terminal temperature values limit the ampacity of conductors but as stated in the first sentence of 110.14(C). But if conductors have a higher insulation temperature rating that can be used for ampacity adjustment and correction factors as stated in the second sentence of 110.14(C). If adjustment and correction factors apply the resulting value determined is the conductors ampacity but the value in the 60 degree C or 75 degree C columns (as applicable) of Table 310.15(B)(16) cannot be exceeded. Essentially whichever value is lower is what gets used.

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