Ambient temperature corrections in regard to 310.15(A)

[TT.local7]

I am currently using Mike Holts exam prep. In the video Dialogue mike holt says that when adjusting for ambient temperature, the 90 degree Celsius list of conductors is to be used. However in the code book 310.15(A) second paragraph, it says that the "temperature and correction adjustment factors shall be permitted to be applied to the ampacity for the temperature rating of the conductor...So my question is, When derating a wire for ambient temperature do I use the temperature rating of the specific conductor I'm using or, do I use the 90 degrees Celsius column from 310.15(B)(1) like holt says in the video? I am using a 2020 codebook. Please do not post on this thread if you do not have a solid answer for me. I am not looking to spark a discussion I am looking for a concrete answer. Thank you

 

[TT.local7]

I was correct. adjustment is based on the specific insulation type used in the application. the video spells it out more clearly as it goes on

 

[texie]

I think you are misunderstanding Holt's text. If you are using 90 degree conductors, then you use the 90 degree column as the basis for your ampacity calcs. The final answer can not exceed the rating of any devices in the circuit such as breakers, etc. In this day and age almost everything is rated 75 degree.
But beware, in an exam it should be assumed that all items rated 100 amps or less are rated 60 degree per 110.14 unless marked otherwise. If a test question does not specify the temperature rating for any device 100 amps or less assume 60 degree when considering your answer.

 

[TT.local7]

He continues to comment much later in the video when discussing a water heater in a residential setting, that even though the wire is sized at 60 degrees Celsius because its equipment rated 100 amps or less, that if an adjustment is to be made, it would be made from the 90 degree C column. he says this in the journeyman exam prep video at 1:59:53 into the video lol. I would also like to note that this time when he references the correction at 90 degrees C there is no type of specific conductor (therefor no specific temperature rating on conductors) being mentioned. So again, is ambient temp based on the temp rating of the specific insulation type/temp rating being used or is it based on 90 C

 

[ToxiKing]

I would also like to note that this time when he references the correction at 90 degrees C there is no type of specific conductor (therefor no specific temperature rating on conductors) being mentioned

Just like texie said, you will only apply Ambient Temperature Corrections based on the insulation of your wire. On the video, maybe THHN or THWN-2 were mentioned. In that regards, you will select the multiplier on the 90 C column of Table 310.15(B)(1) or (B)(2).

 

[TT.local7]

Yea this is how I was taught originally, but he mentions it multiple times in the video and it throws you. He continues to use the 90c column for his ambient temp corrections without mentioning the wire type. weird.