What are the risks of an electrical setup like this.

D

D.sebens

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Let me preface that I “can” do it right I’m just being cheap and lazy. My new to me lathe is wired in 220 no neutral. It came with an articulating 110v lamp. The previous owner just had it plugged in to a wall outlet. The way I have it orientated that’s not really feasible.

The two easy options are an extension cord hanging around (not what I really want to do). And the real question here, how wrong will it be if I used the ground supplied to the lathe and added a 110 box for the lamp?

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?
 
It's not so much that it is against code, you're increasing your chances of electrocution, or hurting someone else. Ground wires are there for protecting human beings in case there is a short. You could essentially be electrifying every metal object that uses the same ground.

DO NOT DO THIS. If you want to plug the lamp in, replace the receptacle with a 4 prong outlet that is wired to both hot legs, the neutral bar and the ground. Replace the cord and plug with 4 wire cable. Wire the lamp with the hot and neutral. DO NOT USE A GROUND AS A NEUTRAL.
 
What’s the supply you have to the lathe?
 
MyLilMule said:
It's not so much that it is against code, you're increasing your chances of electrocution, or hurting someone else. Ground wires are there for protecting human beings in case there is a short. You could essentially be electrifying every metal object that uses the same ground.

DO NOT DO THIS. If you want to plug the lamp in, replace the receptacle with a 4 prong outlet that is wired to both hot legs, the neutral bar and the ground. Replace the cord and plug with 4 wire cable. Wire the lamp with the hot and neutral. DO NOT USE A GROUND AS A NEUTRAL.
Click to expand...
So I’m not arguing but why it’s neutral and ground bonded in the box. What is the scenario that leads to electrocution?
matthewsx said:
What’s the supply you have to the lathe?
Click to expand...
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. I’m really looking for an actual example of why this is unsafe. What’s the failure mode for this scenario?
 
So, wire in a 120v outlet and run the lamp from that.

And yes, change the lathe to being grounded too. Small price to pay for safety.

John
 
matthewsx said:
So, wire in a 120v outlet and run the lamp from that.

And yes, change the lathe to being grounded too. Small price to pay for safety.

John
Click to expand...
As wired the lathe is grounded just no neutral. And make sure nobody takes this as combative. I’m just looking for why it’s unsafe.
 
Two problems:

1. Shock hazard. A neutral is grounded at the source, not at the load. Due to voltage drop in the neutral wire, it is not at ground potential at the load. It is X volts above ground potential. If you touch the load end of the neutral, you will receive a shock. The magnitude of the shock will depend on how much load current is flowing, how much resistance is in the wire and how well grounded you are. It could be low enough to just be an uncomfortable tickle or it could be high enough to fry your eyeballs. That’s why ground wires don’t carry load current. If they did, the grounded equipment wouldn't be grounded.

2. Besides the shock hazard, there is also a fire hazard. Ground wires are usually smaller than the circuit conductors. Breakers and fuses are sized to protect the circuit conductors, not the ground wire. A ground wire used in place of a proper sized neutral could be overloaded and the breaker or fuse would not protect it from overheating and starting a fire.

The Code doesn’t have rules just for the sake of having rules. It’s a safety thing. :)

Tom
 
higgite said:
Two problems:

1. Shock hazard. A neutral is grounded at the source, not at the load. Due to voltage drop in the neutral wire, it is not at ground potential at the load. It is X volts above ground potential. If you touch the load end of the neutral, you will receive a shock. The magnitude of the shock will depend on how much load current is flowing, how much resistance is in the wire and how well grounded you are. It could be low enough to just be an uncomfortable tickle or it could be high enough to fry your eyeballs. That’s why ground wires don’t carry load current. If they did, the grounded equipment wouldn't be grounded.

2. Besides the shock hazard, there is also a fire hazard. Ground wires are usually smaller than the circuit conductors. Breakers and fuses are sized to protect the circuit conductors, not the ground wire. A ground wire used in place of a proper sized neutral could be overloaded and the breaker or fuse would not protect it from overheating and starting a fire.

The Code doesn’t have rules just for the sake of having rules. It’s a safety thing. :)

Tom
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D.sebens said:
Let me preface that I “can” do it right I’m just being cheap and lazy. My new to me lathe is wired in 220 no neutral. It came with an articulating 110v lamp. The previous owner just had it plugged in to a wall outlet. The way I have it orientated that’s not really feasible.

The two easy options are an extension cord hanging around (not what I really want to do). And the real question here, how wrong will it be if I used the ground supplied to the lathe and added a 110 box for the lamp?

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?
Click to expand...
I wanted to do similarly a couple of years ago on my bandsaw - have a 110 v water pump turn on/off with the main motor which was 220 3 phase. I was strongly advised Not to do it that way. They said to use a machine tool transformer which I did.
The link is to several used ones on ebay.
They are cheap enough that you can afford to do it properly and safely. I would buy the one that is already in the enclosure box a few items down.

www.ebay.com

machine tool transformer for sale | eBay

Get the best deals for machine tool transformer at eBay.com. We have a great online selection at the lowest prices with Fast & Free shipping on many items!
www.ebay.com
 
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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?
 
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