Wire resistance table for smaller than #18?

[SCRllc]

Can someone please point me to a table in the NEC that lists resistance of conductors smaller than those shown in Table 8? Thanks in advance!

 

[zbang]

I don't think you will, the NEC generally doesn't cover smaller sizes. However there are tons of resistance charts out there, a quick search will turn them up.

 

[SCRllc]

Thanks for the reply, I thought I saw one, maybe fixture wires?

 

[david luchini]

Thanks for the reply, I thought I saw one, maybe fixture wires?

I don't believe fixture wires are permitted to be smaller than #18...which is the smallest conductor listed in Table 8.

 

[GeorgeB]

Can someone please point me to a table in the NEC that lists resistance of conductors smaller than those shown in Table 8? Thanks in advance!

It is not a NEC issue or documented, but if you are looking for resistance for other reasons, you can find wire tables many places on the web. In my case, I use the knowledge that every 3 AWG number steps is a 2:1 change in resistance, then I interpolate.

For example, within 10% for sure, #10 is 1 ohm/1000 ft. From my "rule", #13 is 2 ohm/1000, #16 is 4 ohm/1000, #19 is 8 ohm/1000, #22 is 16 ohm/1000.

Since the relation is logarithmic, the interpolation is difficult, but with confidence I can say that #18 is about 7 ohms. #20 is about 10 or 11 ohms.

If you cannot find in on the web (I would use Google and search for "copper wire tables"), let me know and I'll dig a little myself.

 

[Strathead]

Or you can use the K factor to get close 12.9 per 1000 circular mils.

 

[hbiss]

Table of equivalent AWG Wire and Resistance per foot

AWG Chart of Approximate equivalent Cross-Sections of Wire, American Wire Gauge by Resistance per 1000 feet

www.interfacebus.com

-Hal

 

[SCRllc]

Thank you for the thoughtful replies. In the license prep class, John pointed out a table with information on smaller conductors.
I had a test question: “what is the resistance of 1000’ of #20 copper wire”. As it turns out, I guessed the correct answer 10.4 ohms. But if the question was on the test then it must be in the book somewhere?