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As the title puts it , why is stranded wire used for most light fixtures and dimmer switches. I have never dealt with stranded wire until recently doing a few upgrades in the house and i feel like stranded wire could increase the chance of a poor connection in wire nuts. Twisting the wire nut with the stranded wire without pretwisting worked best and I removed the nut just to check on each connection before putting it back on. But one time twisting it causes the stranded wire to break (twisted to hard I guess). I could see this happening to other people so that is what got me curious why manufacturers would even take this chance of electrical failure (arc from broken wire in nut, etc).

I assumed it might just be due to cost but Lutron dimmer switches are not cheap and more high end from what I read so maybe cost savings isn’t the reason?

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  • Consider using lever nuts to connect solid and stranded wire. See e.g. the WAGO 221 series.
    – danzel
    Jan 22 at 8:13
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That's only a problem if your wire-nut technique is bad.

Most people's technique is terrible when they start. Where people depart is that some refuse to learn, and do not test their work, or think, or refine their technique. They simply tape the wires onto the nuts to keep them from falling apart. This only hides the symptom; the root problem is a poor electrical connection, which results in overheating, arcing, and a meltdown or fire.

Just don't be that person and you'll be fine.

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Because it bends easier and even when bent to extremes it normally doesn't break or malfunction. Single strand gets nicks and kinks when bent and just a lot harder for your average person to deal with.

You have to think sometimes you are shoving wires where ever when installing a light fixture or fan. A home owner may not be comfortable pressing as hard as you can with single strand - or more importantly when they do press hard to get the wires into the box they could possibly make their connection faulty producing problems or dangers down the road.

I agree from an electrician point of view - I rather run the single strand in my house to a solid wire because I know how to twist it properly and I know the connection will be good. However the people on this site in the same boat are 2% of the population.

The Lutron dimmer switches are a good example - these are sold to home owners as upgrades. Sure electricians install these but Lutron isn't worried about the electricians - they will make do with whatever. These dimmers will fill up a small outlet box and with possibly 8 other wires in the box you are trying to make the homeowner swapping this thing out have an easier install. It does drive me nuts though when they only have like 1/2" of the stranded bare and you have to cut more insulation out to get it to catch right with solid - connecting stranded smaller wires to solid is an art.

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Because lights need comparatively low amperage, and are typically located in a protected (indoors) area.

Solid wire is stronger and more reliable in some ways (e.g. corrosion resistant) than stranded wire, but stranded wire is generally easier to work with.

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    Solid is stronger is some ways, but it's much more susceptible to breaking due to repeated bending than stranded is. As such, which is more reliable depends on what they're being used for.
    – Nate S.
    Jan 21 at 20:38
  • Good point, I've tried to tone down the statement and make it clear that it is not stronger in every way. I think it safely carries more amps than stranded also, but I'm not positive so I didn't put that.
    – izzy
    Jan 21 at 22:07
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    For a given wire diameter, stranded would have less copper due to the voids between strands, which would theoretically make them lower ampacity, but that's not how wires are sold. If you buy 12AWG stranded, it'll be a little bigger than 12AWG solid, such that the cross sectional area of the copper, and thus the ampacity, is identical between the two.
    – Nate S.
    Jan 21 at 22:14
  • @NateS. stranded wire can carry more current due to the skin effect.
    – dandavis
    Jan 24 at 10:45
  • @dandavis, that's not at all a concern at mains frequencies at this wire size. At 60 Hz, the skin effect doesn't start until 8.5mm depth, meaning you'd need a 17mm diameter wire to see it at all. They don't even make wires that size in solid, because that would just be a copper rod. For household wiring, the skin effect can be ignored entirely, and makes no difference in ampacity.
    – Nate S.
    Jan 25 at 17:13

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