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I recently replaced a single AC dimmer light switch that was one of two light switches in a larger box. The ground wire leading to the switch was raw copper without any insulation.

After replacing the switch, and turning on the circuit breaker, the breaker sparked and tripped. I'm thinking one of two things explain why:

  1. The new FEIT switch was defective (which would be my 4th defective switch from the big carton of FEIT switches I bought).
  2. The naked ground wire touched the contacts of the other switch in the box.

I turned off the breaker, put it a completely different switch, and did my best to get that naked ground wire as far away as possible from the other switch. Then I flipped the breaker on (shielding my eyes, and standing away from the breaker box), and everything worked.

So my question: Why are ground wires sometimes installed without any insulation? The cost of insulated wire is almost identical to that of non-insulated wire, so I tend to think cost is not the primary driver of this decision.

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  • Think so it is easier to cause short anywhere(or kill rats) on cable path and trip breaker/fuse. Insulated ground will only have certain short sections for short to happen. Might want your two cents back.
    – crip659
    Mar 16 at 23:42
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    I learned to wrap switches and outlets in electrical tape to help avoid a bare ground wire touching a live screw terminal in an electrical box. That doesn't answer your question but it can help avoiding this issue in the future.
    – MacGuffin
    Mar 17 at 7:47
  • @MacGuffin Great tip! Here is a question I just posted requesting further details: diy.stackexchange.com/questions/219053/… Mar 17 at 19:31
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Cost, mostly

Whether your grounding conductors are bare, insulated, or not even a wire to begin with depends on what wiring method you are working with. NM, because it's made in large quantities, uses a bare grounding wire to save cost (likewise with UF and most SE cables, as those pennies add up at industrial scales). On the other hand, if your house is wired using armored cable (AC), there are no ground wires, because the metal cable armor serves as the ground with the aid of a thin "bonding strip" to prevent "choking" of fault currents caused by stray inductive interactions. That lack of grounding wires is also a notable feature of many installs done in metal conduit, as the conduit itself then becomes the grounding conductor.

Furthermore, some wiring methods aren't uniform in how they handle this; it's legal (and occasionally required) to run a separate equipment grounding conductor in metal conduit, and in most (albeit not all!) cases, equipment grounding conductors inside conduits can be either bare or insulated. Likewise, metal-clad cable usually uses an insulated grounding conductor, but can sometimes be found with a bare grounding conductor, or in configurations where the armor is the grounding means.

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  • It also saves the ele from having to strip 12" of it so that they can curl the box screw and then have enough length for the device / branch pig tails. I was thinking it might also be a bit of a safety thing - if you drive a nail into NM and hit the hot or neutral through the insulation you have good chances of the nail hitting the ground and it tripping out the breaker. Mar 17 at 2:11
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You're supposed to resolve that with technique

First, if you're working in a metal box, there shouldn't be any ground wires flying around in a switch box. Code requires that you take the cable grounds to the metal box itself FIRST -- either via separate ground screws for each, or pigtail them to one ground screw. Switches can pick up ground via their mounting screws, so the next thing you do is push all the ground wires into the very back of the box, and never touch them again.

You should be installing grounds first anyway because it smooths troubleshooting. (some people install them last, and wind up with a puzzling problem when the circuit stops working when the grounds are connected. The problem wouldn't have been puzzling if they'd done grounds first).

Now, if it's a plastic box, then first, trim all your backstabs * and back-wires so they have no exposed shank of bare wire. (I cued up this video so you can see the exposed shank of copper on a neutral wire. That's terrible! The switch has a strip gage for a reason!) And that's a code requirement/violation by the way: 110.3(B) and 110.12.

Then second, run down all the screws you aren't using so they aren't sticking out. Finally, wrap the switch in electrical tape so all the screw heads are covered.

Now you know about Feit Electric, stop buying their stuff LOL. Also on the "expect junk" list are Utilitech, Lights of America and Commercial Electric. These are all UL-listed so they're safe, but UL doesn't test for reliability. Try brands like Leviton, Lutron, Legrand, GE, Eaton, etc. And in the "surprisingly good" category: IKEA. Crud sold mostly online/mail-order should be avoided at all costs; they're using a Customs loophole to sell stuff that isn't even UL-Listed and will burn your house down. Amazon is actually the worst of this.



* Backstabs, where you jab the wire in and it grabs, are bad news anyway - they're Code legal and judged safe by UL, but vast experience is that they are highly unreliable, and create frustrating "half my circuit went dead" problems. They are certainly uninspectable, which makes finding such a fault even harder. Also when using backstabs you're not using screws, and the tendency is to leave the screws in the factory-supplied position: sticking all the way out like Ross Perot's ears. That makes the screws more likely to snag a ground wire or metal-box side. **

** And don't get me wrong. Metal boxes are vastly superior at every job we need boxes to do. Their metalness and risk of hitting Ross Perot ears isn't a failing; run down the screws and they're fine. Actually metalness is a virtue, as they're far more likely to "clear" (trip) faults like a loose hot wire. And of course they are vastly superior at containing overheats and resisting burn-through. Their handling of grounds is also superior.

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    "first, trim all your backstabs"... I think you meant, "first, don't use backstabs". The consensus almost everywhere seems to be that backstabs are nasty, failure-prone shortcuts.
    – Matthew
    Mar 17 at 18:46
  • @Matthew Yeah, I was thinking of back-wires like in the video, but you're right, I should cover the general badness of back-stabs. Mar 17 at 20:02
  • Ah, yes... I hadn't watched the video, but I see now those aren't the much-derided backstabs... they look similar but they're still screw-down, which is much better.
    – Matthew
    Mar 17 at 20:13
  • Oh man, that Feit video... not only is the conductor exposed, the dimmer is screwed to the box with drywall screws. The sharp tip risks penetrating a cable behind it.
    – P2000
    Mar 18 at 4:16

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