What are the risks of an electrical setup like this.

[Jake M]

I know this against code and unsafe but can someone explain why I shouldn’t and what the potential scenario is that would lead to the unsafe situation?

There are a lot of possible scenarios, and the biggest reason it's hard to get a straight answer to that, is without an accurate and complete schematic diagram of your entire electrical installation from the meter onwards, it's hard to tell you which failure modes are likely, possible, or even conceivable.

The idea of the dedicated ground (the "equipment ground") is that no current whatsoever is flowing on it, ever. If you allow current to flow on it, there is always some voltage drop. (Wires themselves have resistance, and drop some voltage). You will end up with, somewhere, potential differences between exposed items, including any panels you have installed. All the bare wires bonding anything in the house are non longer waiting there to carry current for a millisecond, in order to trip a breaker, but they are conducting current. What could that do? Which house do you live in? There could be a different set of answers for every member of this forum.

It's not so much that some specific thing could or could not happen to you. The real world reason this should not be done, is that you do not know what might or might not be at risk, or how much risk. It could be nothing. It could be everything.

I have 4 wire single phase nearby but the lathe came with a 3 wire whip on it. I need to get an outlet for it, I could change the plug style and whip but that costs a little more.

There's your answer right there..... You need to get something..... Stew on this for a minute... It still cheats a bunch, but it doesn't affect the the rest of the house, only the lathe. You have four wire single phase available near the machine. Leave the building wire intact, with the correct four pole receptacle which is either already there, or you need to identify and source the correct one. Wire that receptacle absolutely correctly. Hot, Hot, Neutral, and Ground. Then, on the plug end of the whip, install the matching four pole plug. Depending on what cord the lathe came with, you might need white tape to reidentify the ground wire in that cord as neutral. Do that at both ends, even if it clearly just screws to an electrical box or motor housing or whatever else, reidentify it. That's the reminder that it's no longer a "ground", but a "neutral".. Attach that re identified, now neutral wire to the Neutral pin in the plug.

By solving the problem "outside" of the receptacle, instead of the building wire, you will not affect the design intent of the building's wiring, no current going through the things that are bonded to ground, not put current parts of your building that were designed to last ONLY long enough to trip a breaker, you will simply make your building as it should be (or at least how it is now), and the lathe as it would have been before enough people died that the dedicated equipment ground became mandatory. Prior to the equipment ground being separated and manditory, this is how it would have been factory wired if it were designed to have 120 volt accessories. (Or 117 volt, or 115 volt, or 110 volt....).

Still not as good as doing it right, but the compromise is well documented, well known, and very isolated to the lathe it's self. The rest of the house is exactly as it was, no new risk, no new compromise, nothing about this affects anything, anywhere, except the lathe it's self.

 

[rabler]

Really pretty simple why not. If your ground wire is somehow disconnected from the neutral bond and ground rod, by corrosion, mechanical damage, etc, it is still connected to the frame of every piece of grounded equipment. That 120v light, when turned on won't work because it is no longer a complete circuit. But it will connect EVERY one of those grounded frames to 120V. That is a very real and dangerous shock hazard.

Yes, that connection to 120V is through the light bulb. But the bulb will pass more than enough current to stop someones heart in the wrong circumstances. Depending on where that corrosion/damage happened, it could be the frame of your microwave or dishwasher or some other gadget in a completely different part of the house. Wife, kids, guests? The whole purpose of a ground is a safe, redundant path for the electricity to follow IF something goes wrong.

 

[Ischgl99]

You were given some good examples above, I'll give a real life example. When I was a kid, probably 12ish years old, I was at the supermarket with my mom. At the check out, I grabbed the conveyor frame and a metal railing on the other side of me at the same time and got the shock of my life. Not enough to kill me obviously, but enough that I remember it 40+ years later. I was a better neutral to the conveyor when I touched the grounded railing. They probably didn't intentionally wire it that way, but somehow it did happen. You on the other hand, would be intentionally creating that situation with everything connected to ground in your house if you wire it that way.

 

[D.sebens]

This question and other questions like it, typically get answered with some variation of "these rules are written in blood and you don't have the pedigree to question them, just do what you're told." Reason being, either the responder doesn't actually know the answer, or doesn't know how to articulate it to someone who lacks the electrical background necessary to understand the technical answer. In either case I guess they think the ominous warning tactic ("don't touch the stove, child") is the one most likely to result in no death or injury. I understand that tactic but I don't think it's the most effective. I will try to explain this the simplest way I can but if you are not convinced, please do it the right way anyway.

Scenario #1. Let's say you have an old corded hand drill, metal case, 120V, 2 prong (no ground). Inside the drill, the black wire breaks and contacts the metal case; now when you grab the drill, you are electrocuted before you ever touch the trigger. Or if the white wire breaks and touches the case; you pick up the drill, all is fine until you pull the trigger, then current flows through the trigger switch, through the motor, then through your hand, and the result is the same, electrocuted.

Scenario #2. Now you have a drill a few decades newer, still metal case, but now it has a 3-prong cord plug with a ground. When the black wire touches the inside, current prefers the path through the ground wire so you are saved from electrocution. Also the high current ground fault trips the breaker so the hazard is gone until you reset it. Same story for the white wire.

Scenario #3, same drill, metal case, 3 prong, but the white wire is broken somewhere in the cord and you don't know where. So you have the bright idea to open up the drill and connect the green wire in place of the white wire so that the drill can still run, because after all, they're both connected to the same place at the other end. Congrats! It works! Except now you've undone many years worth advancements in safety, and actually made the drill LESS safe than the one in Scenario #1.

Why LESS safe? Note the wording in Scenario #1: "if the white wire breaks and touches the case." This "and touches the case" caveat no longer applies. The wire break no longer even has to happen inside the drill. Since that green wire is bonded to the case, an open circuit anywhere between the drill and the breaker panel will cause the case to become energized and electrocute you as soon as you pull the trigger.

Now forget the drill, replace it with a lamp, same story. If you use the green wire for a return current path, then you have 120V-> bulb -> case -> green wire -> return. If that current path ever gets broken while the light is on, the case will be energized. That includes during the brief period of time while you're unplugging it, if the ground pin breaks contact a split second before the hot pin. How cool would it be to get zapped with 120V as a reminder to turn off the lamp before unplugging it?

I feel like this example makes the most sense. Seems like the most likely failure mode with stealing the ground for a neutral would be if the new neutral wire became open in the appliance and touched the frame it would end up energized when the circuit is switched on. So in a proper grounded setup if that happened the current has a path to ground. The redundancy and dedicated circuit is what makes it safe correct?

 

[D.sebens]

I would just find a 220v bulb for the lamp. I have seen some LED bulbs that will run on 110v/220v.

"I" would not hijack the ground and use it as a neutral. Being electrocuted is not fun!

https://www.amazon.com/OMTO-Frosted-Light-Equivalent-85-265V/dp/B07BZF71HG/ref=sr_1_4?keywords=220v%2Bled%2Bbulb&s=industrial&sr=1-4&th=1

The 220v to 110v transformer is also a good idea!

What about this idea? Say thr outlet is properly marked that it is 220v. This example actually takes place in real life. There are 12v bulbs that have the same base as their 110v counter parts. Does this seem like an okay situation? I will end up not stealing a ground so that will be intact and the light will be 220v. Assuming I can find a light, I feel like led bulbs might go up that high.

That being said, the side of me talking myself out of it is going to come out. I “think” the unsafe scenario there would be the same reason a travelers or Chicago 3 way is illegal. Since the appliance has a single pole switch when hooked to 220v it would still have 110 voltage potential in the socket from the other leg right?

Before polarized and grounded plugs was there just a chance you would get zappec when changing a bulb if you made a path to ground and touched the screw base? (In this scenario the lights plug was installed into the outlet with the bulb screw base circuit on the black wire or load side)

 

[D.sebens]

You were given some good examples above, I'll give a real life example. When I was a kid, probably 12ish years old, I was at the supermarket with my mom. At the check out, I grabbed the conveyor frame and a metal railing on the other side of me at the same time and got the shock of my life. Not enough to kill me obviously, but enough that I remember it 40+ years later. I was a better neutral to the conveyor when I touched the grounded railing. They probably didn't intentionally wire it that way, but somehow it did happen. You on the other hand, would be intentionally creating that situation with everything connected to ground in your house if you wire it that way.

I do believe it would jeopardize safety of the device but not of house. Inside my electrical box the ground and neutral are bonded so if the neutral failed inside the box all grounds would be energized and if the ground failed in the box it would no longer offer ground protection. Defeating the ground at the lathe makes the lathe unsafe but I don’t see how it compromises the rest of the house (in this case it’s an outbuilding with its own panel).

Keep in mind the is just an exercise of why I shouldn’t do it. My questions are curiosity’s and i am just looking for the why’s of why I can’t.

 

[markba633csi]

You are correct, it wouldn't compromise the rest of the house.
In the old days, clothes dryers used the neutral as ground so three wires- the timer was 110 volts. But that's not done anymore for new installs, a separate ground is always used making it 4 wires.
Be safe

 

[toprecyler]

Very informative thread. I’ve had a problem in my shop since I installed my bigger lathe and mills in last couple years. Somehow my mill has a voltage going to it. I get shocked sometimes when I touch it. I found this out when I was doing a better cleaning of the table. I must have had a metal splinter somewhere in my little finger, because that was what was tingling. Put the voltage meter on it, and I’m getting up to 50 volts to ground plug.

I am now starting to see where I may need to look for the problem. It may be in some wiring I did 30 years ago.


Sent from my iPhone using Tapatalk

 

[higgite]

You are correct, it wouldn't compromise the rest of the house.
In the old days, clothes dryers used the neutral as ground so three wires- the timer was 110 volts. But that's not done anymore for new installs, a separate ground is always used making it 4 wires.
Be safe

But (there's always a but), in the old days when the neutral was used for ground, the neutral wire was sized for the load. Dedicated ground wires used today aren't. The breaker or fuse that protects the hot wires of a 220v circuit from overloads/short circuits won't protect a smaller ground wire used as a neutral.

 

[D.sebens]

But (there's always a but), in the old days when the neutral was used for ground, the neutral wire was sized for the load. Dedicated ground wires used today aren't. The breaker or fuse that protects the hot wires of a 220v circuit from overloads/short circuits won't protect a smaller ground wire used as a neutral.

As far as I know the small ground wire isnt until you get to 8 gauge wire and smaller. Maybe 10 gauge. There’s a code about ground wire size. So either 30 or 40 amp circuits and above.