Stranded #18 wire in conduit, re-purposed from low voltage to AC

[brycenesbitt]

I'm trying to solve a retrofit problem inexpensively. Would anything in the NEC prevent re-purposing #18 stranded wire in conduit for use with an 110V circuit, given a properly sized over-current device? This is two or four wires pulled through conduit, #18 copper stamped 300V, with runs of 150 feet or so. The wire was originally pulled for fire alarm sensors in 1977 and operated at 24 volts DC. Would any special requirements apply to the wire? How would you mark this to the 'next guy' is not confused/laugh too hard? Note that the proposed AC loads are well within the ampacity of the wire.

 

[ActionDave]

I'm trying to solve a retrofit problem inexpensively. Would anything in the NEC prevent re-purposing #18 stranded wire in conduit for use with an 110V circuit, given a properly sized over-current device?

Yes there is. Smallest conductor you can use is 14AWG. Don't have the section at my ffingertips, but there is someone here that does.

 

[jumper]

Yes there is. Smallest conductor you can use is 14AWG. Don't have the section at my ffingertips, but there is someone here that does.

2008, 310.5

2011, 310.106

 

[iwire]

What is the function of the new circuit?

There are exceptions to the 14 AWG limits.

 

[petersonra]

if it fits in article 725 you can reuse them. there may be other sections that allow it as well, but for the most part you can't use #18 for normal NEC wiring.

 

[brycenesbitt]

The end attachment would be a series of 120V consumer smoke detectors. Clearly current draw is
not an issue with the #18 wire. I can yank out the #18 wire and pull #14, but it would be for no reason other than code compliance and reduction in confusion. Finding the appropriate breaker might also be a problem ;-).