1gnoirents posted:

1gnoirents posted:

Thanks for the information. I did find a 30 amp cable if it could be used in some way with the existing outlet to the dryer.

I did not explain the use here, this is not a permanent installation. I am just trying to fix two dryers and test them and it will be supervised when on and once they're gone anything ive done would be reverted

FISHMANPET posted:

So help an amateur out here, it looks like currently, that's a 240V with a ground and no neutral, so it can't provide any 120V power. It looks like the "3 wire" diagram assumes 2 hots and a neutral to be able to provide both 240V and 120V. Electrically you could treat the current green ground wire like a neutral but that would be VERY BAD for safety. So from what I know, that's really gonna require pulling a fourth white wire through that conduit to get a neutral to that box to be able to do the 4 wire method.

Waiting for Motoronic to point out my mistake and how making it could kill somebody.

1gnoirents posted:

Thanks for the information. I did find a 30 amp cable if it could be used in some way with the existing outlet to the dryer.



I did not explain the use here, this is not a permanent installation. I am just trying to fix two dryers and test them and it will be supervised when on and once they're gone anything ive done would be reverted

1gnoirents posted:

movax posted:

Blackbeer posted:

Yeah, land the new white wire (#10 stranded THHN) to the circled bus bar. You can just put it in as there should be zero volts between neutral and ground.

The new white wire will replace the green wire on the outlet. The cord will be using it's green wire as a neutral, so it'll land on the neutral terminal (middle one) in the dryer.

1gnoirents posted:

Blackbeer posted:

No.

The new white wire will go to the outlet junction box, and be connected to the outlet in place of the green wire.

The green wire on the cord will go to the middle terminal of the dryer.

The cord will plug in to the outlet, which will connect the new white wire on the outlet to the green wire on the cord.

Don’t just have a loose wire from panel to dryer. When you’re done leave the white wire connected in the panel, swap the green back on the outlet, and cap the white wire off.

Arsenic Lupin posted:

Is there a standard book on home electricity you guys recommend? Like, not "You are a contractor, please know how not to gently caress this up", but "This is the difference between neutral and ground, this is what the wiring diagram looks like for two switches in the same room", that sort of thing? I don't expect to be doing any wiring myself, but I like knowing how things work.

Arsenic Lupin posted:

Is there a standard book on home electricity you guys recommend? Like, not "You are a contractor, please know how not to gently caress this up", but "This is the difference between neutral and ground, this is what the wiring diagram looks like for two switches in the same room", that sort of thing? I don't expect to be doing any wiring myself, but I like knowing how things work.

cruft posted:

I really like my copy of Wiring Complete, but if somebody else posts an answer to this, I would go with their recommendation instead.

1gnoirents posted:

For the sake of argument, could I use the three wires as they are from the outlet and run a four wire setup if I added the separate neutral wire where its supposed to go? So from the outlet I'd run the two hots and the ground wire to the dryer in the diagram then run the neutral wire directly in ?

Inner Light posted:

Is this the same guy doing commercial work without a license, isn't that literally illegal (not to mention could void your liability insurance)? Come on man this doesn't sound like it's going to end well. I say this as someone who has already screwed up an electrical job where I live.

Motronic posted:

No. You were already told this when you posted a diagram of exactly that.

cruft posted:

Please don't do this. What Blackbeer posted is the right way to wire it up if, like, zombies have taken over the town and you absolutely need a working dryer in order to keep your ragtag group of survivors alive long enough to be rescued by the helicopter coming in. But as soon as you have a working dryer, you are going to get a call that your dog got shot and your wife just discovered she's 9 months pregnant with non-identical quadruplets, and you are going to forget all about your "temporary" wiring job until somebody decides to take a power drill to the chassis of the dryer in order to mount a clothesline, and suddenly your business is faced with a lawsuit for having a dryer not wired up to code. When they bring the expert witness in, she'll testify that for some god damned reason you wired a L6-30 to have the ground plug connected to neutral, and then connected the wire of the cable to neutral on the back of the dryer, and she'll say "I can't imagine what this person was thinking, but no licensed electrician would ever do such a ridiculous thing" and you can kiss your cruise to Haiti good-bye.

Blackbeer posted:

Temporarily using the wrong outlet isn't great. There are literally millions of 3-wire dryer hookups (NEC legal) in the US if that's what you're concerned about. 4-wire is best and code on new home construction for a reason, but it's not exactly an end of world scenario.

Motronic posted:

Blackbeer posted:

Commercial is the same as residential with dryers. I'd still just hook it up 3-wire instead of buying a cord and plug for temporary testing if it were me. It's not to code, but little of this was; just like trying to solve stuff and it got away from me.

Blackbeer posted:

Temporarily using the wrong outlet isn't great. There are literally millions of 3-wire dryer hookups (NEC legal) in the US if that's what you're concerned about. 4-wire is best and code on new home construction for a reason, but it's not exactly an end of world scenario.

Motronic posted:

Depends on who's jurisdiction. And we're talking about modifying an outlet or cord, so my code official interpretation based on the 1996 NEC is that you're wrong.

cruft posted:

And I was also concerned about a green wire carrying neutral. I know there's nothing physically different about green insulation, but I've seen a lot of "temporary hacks" go for years and then get forgotten. It just struck me as something that would get posted in this thread with the question "what was the PO thinking here?"

Motronic posted:

There is a perfectly fine solution to "wrong colored wire", and that's marking both ends, usually with the "correct" color tape.

That still doesn't make that modification code compliant for use on a dryer.

cruft posted:

Is it code compliant to replace the ground terminal with neutral on an L6-30 outlet? I know very little about this standard.

smax posted:

Bought a house, PO did some interesting electrical stuff like non-GFCI external outlets with a water mister system supply hose routed through the electrical conduit powered by a suicide cord inside the house.

Next questionable item: they wired in a generator hookup to the main panel. This is (of course) a standard 4-prong 240V socket in the garage with another suicide cord to back feed the main panel.

I know this is a Bad Idea, but exactly how much of a Bad Idea is it? I know that if I ever think about using this thing to cut the mains power first, and to take care not to run around with a live suicide cord. I don’t even have a generator at this point, just looking for some input if I ever get hit by a hurricane and need to use it in a pinch.

I guess I can use the plug for an EV charger in the garage if I ever get one of those. I have an electrician coming for some other stuff, I will probably ask him for an estimate for how much a legit generator hookup would cost.

Edit: this plug has 30A breakers. What amperage does your typical EV charger need?

smax posted:

I know this is a Bad Idea, but exactly how much of a Bad Idea is it? I know that if I ever think about using this thing to cut the mains power first, and to take care not to run around with a live suicide cord. I don’t even have a generator at this point, just looking for some input if I ever get hit by a hurricane and need to use it in a pinch.

movax posted:

It might be helpful to think about why grounding exists / matters to understand how miswiring neutral/ground can be bad. The whole concept behind protective Earths (PE) / the overloaded term 'GND' is to create a separate, designated path for accidentally energized things to dump a fuckload of current through and trip the upstream protection (hopefully!). Metal devices that are AC powered have a convenient death mechanism where the fact they have metal cases means it is conductive and if the insulation on the line wire rubs to a point where it shorts against the chassis, congratulations, it's now at line potential.

So, what if we tie the case to neutral? That should do it, right? Line will short to neutral, a few kA will flow for hopefully some number of milliseconds and then the upstream breaker trips. But -- neutral is the nominal return path for current. Now, if you touch the dryer, you present a non-zero impedance / resistance for current to flow, and you could become the return path instead of the neutral wire in the wall.

Now -- what if we spend the money / update all the building codes / change EVERYTHING to add a designated third wire that in ideal circumstances, doesn't actually functionally do anything, but in the event voltage touches it, it creates a convenient shorting path for the above protection mechanism to kick in (namely, upstream device opening under load). We tie it at one point only to the neutral, so we are 100% sure of the path it takes -- no shortcuts. Call it 'ground', slap a third prong on the plug and try to use it wherever you can. Plastic devices / double-insulated devices / etc don't strictly need to do this if a person can't reasonably touch it -- that's why most wall-warts / USB chargers / etc are still two prongs -- ground is not useful. If you start slicing open the plastic brick to try and lick the transformer in the middle that's dropping line voltage.... that's not a reasonable fault scenario to protect against.

If you take a Fluke, and measure impedance between neutral and ground -- it should be shorted together / very low. That's the whole point, they want to be equipotential. The difference is in the routing and physical wiring -- that's what keeps people safe because through construction, you create that path in the way you wire outlets and stuff.

Maybe that helps in understanding it.

GFCIs are a special class that specifically watches for current flow being equivalent (to some limit, 5 mA IIRC?) on line and neutral. If the current on neutral (for example) is more than 5 mA (again IIRC) higher/lower, the assumption is that current is taking some other unintended path (i.e., meat popsicle) and that power should be cut off.

movax posted:

SouthShoreSamurai posted:

This is a Good Post™

movax posted:

It might be helpful to think about why grounding exists / matters to understand how miswiring neutral/ground can be bad. The whole concept behind protective Earths (PE) / the overloaded term 'GND' is to create a separate, designated path for accidentally energized things to dump a fuckload of current through and trip the upstream protection (hopefully!). Metal devices that are AC powered have a convenient death mechanism where the fact they have metal cases means it is conductive and if the insulation on the line wire rubs to a point where it shorts against the chassis, congratulations, it's now at line potential.

So, what if we tie the case to neutral? That should do it, right? Line will short to neutral, a few kA will flow for hopefully some number of milliseconds and then the upstream breaker trips. But -- neutral is the nominal return path for current. Now, if you touch the dryer, you present a non-zero impedance / resistance for current to flow, and you could become the return path instead of the neutral wire in the wall.

Now -- what if we spend the money / update all the building codes / change EVERYTHING to add a designated third wire that in ideal circumstances, doesn't actually functionally do anything, but in the event voltage touches it, it creates a convenient shorting path for the above protection mechanism to kick in (namely, upstream device opening under load). We tie it at one point only to the neutral, so we are 100% sure of the path it takes -- no shortcuts. Call it 'ground', slap a third prong on the plug and try to use it wherever you can. Plastic devices / double-insulated devices / etc don't strictly need to do this if a person can't reasonably touch it -- that's why most wall-warts / USB chargers / etc are still two prongs -- ground is not useful. If you start slicing open the plastic brick to try and lick the transformer in the middle that's dropping line voltage.... that's not a reasonable fault scenario to protect against.

If you take a Fluke, and measure impedance between neutral and ground -- it should be shorted together / very low. That's the whole point, they want to be equipotential. The difference is in the routing and physical wiring -- that's what keeps people safe because through construction, you create that path in the way you wire outlets and stuff.

Maybe that helps in understanding it.

GFCIs are a special class that specifically watches for current flow being equivalent (to some limit, 5 mA IIRC?) on line and neutral. If the current on neutral (for example) is more than 5 mA (again IIRC) higher/lower, the assumption is that current is taking some other unintended path (i.e., meat popsicle) and that power should be cut off.

B-Nasty posted:

Another reason why this is so dangerous especially near plumbing is that we specifically tie (bond) the plumbing system to ground/neutral near the service entrance. This means that if you have copper plumbing, all your metal faucets/pipes and things are low-resistance potential current paths. Electricity always takes ALL available paths, inversely related to the impedance (resistance, basically.) So, with neutral tied to the washing machine chassis, you could take a wire and connect it between the chassis and a metal faucet and observe that wire carrying some current. The current return path (ignoring that it's AC for convenience) is 'shared' between the actual neutral wire and your plumbing system.

Now, replace that wire with your body as you reach for the faucet while touching the dryer...the impedance of that part of the circuit (you+plumbing) is higher than the neutral wire, but it may be just low enough at 120V to get enough current flowing through you to stop your heart. Dangerous current levels start around 50mA, so we're not talking about much on a circuit that can deliver 100s of times that amount.

So why do older appliances tie G to N when an actual EGC isn't available? It's a tradeoff based on that impedance rule. Yes, there is the potential for some return current to flow from the chassis through you, but the actual neutral wire should get most of it. If the chassis was floating (not tied to neutral) and then got energized with the hot, like movax explained, that would be way worse. Most of the time, you touching a neutral on a circuit with current flowing will not result in a shock, because your path back to the transformer is such high impedance. The only path is the literal earth, which you probably aren't touching.

1gnoirents posted:

For the sake of argument, could I use the three wires as they are from the outlet and run a four wire setup if I added the separate neutral wire where its supposed to go? So from the outlet I'd run the two hots and the ground wire to the dryer in the diagram then run the neutral wire directly in ?

H110Hawk posted:

This is a good post indeed, we should link it from the OP so people can find it. Goes well with the "three prong upgrade" link. (Since OP still posts here I'll let them do it.)