NEC question

[Rei]

NEC 2008 article 110.14(1) states:

(a) Termination provisions of equipment for circuits rated 100A or less, or marked for 14 AWG through 1 AWG conductors, shall be used only for one of the following:

(1) conductors rated 60 deg

(2) conductors with higher temperature ratings, provided the ampacity of such conductors is determined baased on the 60 deg ampacity of the conductor sized used.

My understanding is that for ampacity less than 100A or wire size #14-1, we suppose to use the 60 deg column regardless the wire type. If need to adjust to different temperature, we will then use the temperature adjustment factor. I, however, have seen many questions that acutally used the 75 deg column for wires in the rage of #14-1. One example is EERM sample test #30. Any thought on this?

 

[nuclear bus]

NEC 2008 article 110.14(1) states:
(a) Termination provisions of equipment for circuits rated 100A or less, or marked for 14 AWG through 1 AWG conductors, shall be used only for one of the following:

(1) conductors rated 60 deg

(2) conductors with higher temperature ratings, provided the ampacity of such conductors is determined baased on the 60 deg ampacity of the conductor sized used.

My understanding is that for ampacity less than 100A or wire size #14-1, we suppose to use the 60 deg column regardless the wire type. If need to adjust to different temperature, we will then use the temperature adjustment factor. I, however, have seen many questions that acutally used the 75 deg column for wires in the rage of #14-1. One example is EERM sample test #30. Any thought on this?

You'll notice that not all the types of cables in table 3.16 are listed in every column. For instance, SIS type cable is only listed for 90 degree. There is no 60 degree rated THWN.

However, you can use the 90 degree SIS cable in a circuit with 60 degree rated terminals. Article 110.14 is telling you that is ok, but when you do that you can't use the 90 degree ampacity, you have to remember to derate it for the 60 degree terminals.

Another example. you might chose 75 degree rated THWN or XHHW type cable to use in an installation due to it's jacket properties (such as wet location, fire resistance...etc.), but the devices connected to it may only be rated for 60 degrees, so you can't use the 75 degree cable ampacity but you still can take advantage of the jacket property.

Article 110.14 says either use 60 degree cable in accordance with 110.14.1.a, or if you use a higher rated cable you better derate the cable ampacity in accordance with the 60 degree column.

I hope this helps.