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I moved into a new house and was working on making a three way switch work properly when I came across some creative wiring. The traveling wire between the switches was only two wires, and the ground from it had been electric taped over and used as a neutral wire for the lightbulb.

Obviously normally this would be very dangerous because you wouldn't have ground wire in case of short circuit, however, there is an outlet by one switch and another switch by the other. The grounds from the wires for those has been used as the ground for the switch. That outlet and light are on the same breaker. Here's a rough diagram of how things are wired:

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What are the risks as a setup like this? As far as I can tell, everything is grounded and should be okay but I'm no electrician.

Edit: I was using the word "drain" instead of "neutral" and fixed it.

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  • the ground from it had been electric taped over does this mean that it was a bare, copper (no insulation from the factory) wire covered at each end in electrical tape, or does it mean that it's got some other factory insulation color and has had some green tape applied to "make" it a ground? used as a drain wire what does that mean? Unless there's water in the box that the bulb is mounted to, I'm not sure what would be "draining".
    – FreeMan
    Oct 18 at 17:58
  • Ground wire never are to used except for ground. By "drain" you mean to say neutral?
    – crip659
    Oct 18 at 17:59
  • @crip659 Drain wire is the term for a ground in metallic-sheathed signal cabling/wiring to reduce signal noise, etc. OP's use of it here is a misnomer; they mean ground, probably, since both ground and drain wires are always bare. There's no need for a drain wire in non-signal wiring, like the kind that provides power throughout the house.
    – TylerH
    Oct 18 at 18:23
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    @TylerH Nice to know, thanks for info.
    – crip659
    Oct 18 at 18:32
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    Can you post photos of the insides of the boxes involved please? Oct 19 at 2:00
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What could possibly go wrong?

  • If the ground wire is bare copper, you massively increased the risk of a ground fault, which can kill somebody or burn the house down.
  • If the ground wire has a smaller cross-section, it will not be protected by the breaker from overheating and can burn the house down.
  • Somebody working on the system may falsely believe the ground wire is, in fact, ground. Neutral wires are just as dangerous as live wires (e.g., a loose neutral may unexpectedly become hot if any appliance on the circuit is switched on). This can kill somebody.
  • Somebody may 'fix' the ground by tying it to ground, creating a electrocution hazard long after the 'fix' has been made. This can kill somebody.

In my attic, I found a junction box where the owner had made sure their setup was 'safe': they connected an insulated 2.5mm² wire to another insulated 2.5mm² wire. Only, one was brown and one was green/yellow. Perhaps they decided to 'safely' ground an unused live wire? Or used a bit of leftover brown wire to ground the ceiling lamp? If I hadn't found this box and instead repurposed the other end of either cable, I may have killed somebody (or myself) or burnt the house down. I'm sure the previous owner did not realize that.

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You have ground being used as neutral. That is a serious code violation and can cause a number of dangerous problems.

In the old days, the only real solution would be to run a new cable. Fortunately, today we have smart switches to the rescue! Look for a smart switch that has 3-way operation but that only needs one traveler between the switches. That can be by using some sort of signaling over the power line or by one the switches being a wireless remote.

Make sure to get something that is properly UL or ETL listed - generally that means either knowing exactly what you want (specific manufacturer/model) or by shopping at a traditional bricks and mortar store such as Home Depot or Lowes (shopping online is OK, as long as the items are sold in the US stores they will be properly certified) and not an exclusively online retailer where the items may be provided by a 3rd-party and of dubious quality and safety.

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    The electrical is designed so that under normal circumstances, ground does not carry any current at all and neutral carries as much current as hot! This, combined with ground and neutral only being connected at one location (main panel), makes it so that metal parts (cases of major appliances, electrical boxes/conduit, etc.) function such that if a hot wire comes loose (or certain other problems) there is a short circuit and very quick breaker trip, but the rest of the time those metal things are totally safe - if ground and neutral are combined, those metal parts are not safe. Oct 18 at 20:13
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    In addition, while not directly relevant for your light circuit, in general because ground only carries current in emergencies, the ground wire is often (with larger circuits) a smaller wire that would not be able to handle the full circuit current for an extended period of time, saving money on wire while still providing a path for current for a short time when needed. Plus if the ground wire is bare (it can also be green or green/yellow) then even if it is treated as neutral in all its deliberate connections (switch, light fixture) it would contact other stuff (because it is bare). Oct 18 at 20:17
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    The problem is that one person can take one shortcut (using ground as neutral) and then another person takes another shortcut (perhaps wiring an MWBC incorrectly) and soon enough, the shortcuts kill somebody or burn the house down. Oct 18 at 21:24
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    "A wire's a wire". Code isn't there to be annoying. It's there for safety. There are reasons, you're just a novice and don't know them. So stop thinking you can outsmart the experts when a perfectly viable solution is on the table. Oct 18 at 23:42
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    OK, apologies. The problem is, we insulate neutral for a reason. It is perfectly common to have 120V on the neutral wire, the most trivial wire failure can cause it, even maintenance can, or removal of a device. The conductors in NM have THHN insulation on them, the ground does not. Oct 19 at 17:35
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I'm assuming by drain, you mean neutral. Ground wires can not be used as any other conductor, repurposed. If its green insulated or bare copper, then it must be used as a ground and only as a ground.

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