Is 14g stranded wire a bad choice for outdoor electrical outlets in the dry desert?

Question

I recently went to a big box store and asked for help to extend power to my front yard. I installed a total of three outdoor rated electrical outlets with the cover plate that covers the entire area. I used gray PVC 1/2" pipe and bought three individual spools of 14g wire in black, white and green. The rep handed me these items after I told him what I was doing. After getting home I cut the wires and installed and glued the PVC pipe with the wires in position (I left about 6" of wire I folded back into the electrical box in order to install the electrical outlets the next day. That's when I realized after using my stripping wire tool that the guy at the store sold me stranded wire instead of solid wire. I got rather upset at this thinking it was not the best option for outdoor underground wiring for outdoor electrical boxes. I called the company of the wire product and left a message to get some input from them and they haven't returned my call. But what gives me the impression that this is really bad is that upon closer inspection of the label in cellophane wrap the wire label says "machine wire."

Was this a bad idea? I basically installed these outlets to power outdoor water features that will run fourteen to sixteen hours a day. And then some LED holiday lights for Christmas. I'm reading that stranded wires can oxidize faster due to more strand surface and since this is outdoors that makes me concerned. Although I do live in the dry desert with almost no rain and very low humidity.

Should I redo my work and buy solid copper wire? I feel like a dummy that I didn't pay closer attention to what I was literally handed to buy. But I did tell the rep what I was trying to achieve.

Input, please?

Answer 1

Gray PVC pipe is right out. If you want PVC conduit, you have to use pipe labeled/marked as electrical conduit.

Assembling the conduit over the wires is a serious code violation. The wire insulation is now suspect or failed, because of the PVC cement attacking it. Also, "assembling the conduit over the wire" leads to a bigger mistake - building conduit routing that can't be pulled. That makes it impossible to service/maintain the wires.

All corners must be either broad sweeps (which they sell with the electrical conduit), or "conduit bodies" which are sharper 90 degree turns (or Tees) but they have a lid that can be removed for pulling access. Note that all conduit body lids must remain accessible forever. You cannot use an LB facing into a corner where the lid would be non-removable.

So pull the wires out if able, otherwise cut up the conduit as needed to correct any corner errors, destroying the wire as you do. If you manage to pull the wire out and go over it carefully and it looks tip-top, then you could reuse it.

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As far as the stranded wire, what makes it safe for AC electrical use is the markings on the wire. There is a long message written on the wire, repeating every 12 inches. Read it. If you see the letters "THWN" or "MHW" or "XHHW" then you are good to go.

When you are actually pulling wire, stranded is vastly superior, and a pleasure to work with. I own 12 spools of THHN wire, two #10 and the rest #12. Every single one is stranded. Good stuff!

I don't bother owning any #14 since I DO like color-coding and I DON'T want to buy 10 more spools of wire lol. #12 is allowed as a subsitute for #14.

As far as attaching terminals to stranded wire, that's rather tricky actually. Backstabs are forbidden - don't do it. Attaching to the side screws is also a royal pain in the keister to get right, it usually tangles into a rat's nest. What I recommend for novices is to buy the better $3 "Spec grade" receptacles and switches. These have a "Screw-and-clamp" feature where you back-wire the wires (sorta like a backstab) except you must tighten the screw to clamp the wire. Works great.

Those are much better made receptacles too... you'll see the difference.

As far as heat, THWN-2 wire has a 90C thermal rating, so it can bask in the sun all day. The normal house cable, NM-B, has a 60C thermal rating. Even outdoor cable, UF, is only 60C thermal.

Answer 2

You should be fine. Most likely you got something like this:

The reason they recommended stranded is because it is easier to pull through conduit. You didn't actually pull through conduit - you assembled conduit around the wires - but that is a separate issue.

Most of this wire will actually be dual-labeled as THHN/THWN. That is very important because you are using it outside, so the W for Water-resistant is critical. But assuming that's the case, it is perfectly fine. You do need to be a bit more careful making the terminations (wire nuts or screws - don't you dare try to use backstabs), but other than that, there is no problem at all. Perfectly safe and code-compliant if installed correctly.

FYI even though you're in the desert you still need wet rated wires. Condensation at night is enough to zap things if you use indoor wire outside.