Originally Posted by
Wendell Swedberg
Thanks, Jerry. I understand your approach. Let's try my question this way.
When do you apply E3605.4.1 Conductors rated at 60 degrees C ?
I intrepret 3605.4.1 to mean that where the temperature rating on the termination of the device is 60 degrees or less, you need to use the 60 degree (first column) of Table E3605.1 (allowable ampacities).
For the "maximum" allowable ampacity.
Sooooo....going back to my first post, because in the question it states that the terminals are rated for 60 degrees C, I used the first column (60 degrees C) of Table 3605.1. Because there is no rating for 15 Amps in the 60 degrees column, I went to the next highest rating which was 20amps. 20 amps corresponds with 14 AWG (answer A).
You are ignoring (from my previous post) "Table E3605.5.3 shows that the maximum overcurrent protection allowed for various conductors, with 14 AWG copper having a maximum overcurrent rating of 15 amps.", and you cannot ignore that.
You have several conditions which take precedence all at the same time: a) "maximum" allowable ampacity rating for the conductor with a given temperature insulation; b) "maximum allowable ampacity rating for a conductor in a given ambient temperature; c) "maximum" allowable ampacity rating for a conductor in a bundle or without maintaining spacing; d) "maximum" allowable overcurrent device rating for a given conductor size.
First, you need to look up what is the "maximum" allowable overcurrent device rating for that conductor size.
Then, you need to look up the "maximum" allowable ampacity rating of the conductor for its given insulation - a) above -, then you need to address - b) above -, then you need to address - c) above -, all of which confirm that a given conductor size with the given insulation temperature rating with the given bundling, will meet the "maximum allowable overcurrent device rating" - if they do, then you can go by the "maximum allowable overcurrent device rating" for the breaker size.
But, if they do not meet that (i.e., the maximum allowable rating are derated below the maximum overcurrent rating size), then the overcurrent rating would need to be reduced or the conductor size increased.
Sound complicated?
That's because it is.
But am I applying E3605.4.1 correctly?
No. See the above explanation.
Basically, you need to find the starting point (which is at the bottom of the list) then work through the list to see if the starting point still applies, and, if not, you need to change to a different starting point (conductor size and maximum allowable overcurrent protection rating).