> >
>

Ampacity

Ampacity

#1
01-10-04, 07:38 AM
Member
Join Date: Jul 2003
Location: Montevallo, Alabama
Posts: 577
Ampacity

Could someone tell me the ampacity of #14 thru #6 NM wire.

#2
01-10-04, 07:50 AM
Member
Join Date: Sep 2002
Location: welland ontario
Posts: 8,041
Copied from another site. I think they are for copper wire. Aluminum is different.

THHN
14 = 15 amps 240.4.D
12 = 20 amps 240.4.D
10 = 30 amps 240.4.D
8 = 40 amps 110.14.C.1
6 = 60 amps 110.14.C.1 and 240.4.B
4 = 70 amps 110.14.C.1
3 = 90 amps 110.14.C.1 and 240.4.B
2 = 100 amps 110.14.C.1 and 240.4.B
1 = 150 amps 110.14.C.2 and 240.4.B
1/0 = 150 amps 110.14.C.2
2/0 = 175 amps 110.14.C.2
3/0 = 200 amps 110.14.C.2
4/0 = 250 amps 110.14.C.2 and 240.4.B

#3
01-10-04, 07:59 AM
Member
Join Date: Jul 2003
Location: Montevallo, Alabama
Posts: 577
Ampacity

Thanks for the rapid reply joed.

#4
01-10-04, 08:01 AM
Member
Join Date: Sep 2000
Location: United States
Posts: 17,733
Received 1 Upvote on 1 Post
Ampacity of #14, #12 and #10 is easy. Ampacities of larger wires, however, typically cannot be expressed by a simple table. Factors of the installation influence the ampacity. The entries in Joe's table labeled 110.14.C indicate where such factors are significant.

Technically, there is also a difference between the ampacity of a wire and the largest size breaker you are allowed to use. The entries in Joe's table labeled 240.4.B are ones for which there is a difference. Joe's table shows breaker size, not ampacity.

You did ask specifically about NM. I will note that the type of cable also influences ampacity. Entries in Joe's table above #2 do not apply to NM. It's a moot point however, because I don't think NM is made in those sizes.