Using Dryer Receptacles or Not...Revisited

[jh225]

I have read tons of previous posts about using a dryer receptacle for a Mig, and there are so many differing opinions.

Here is my intended use....

Millermatic 175 machine.

My dryer circuit is wired for the old style dryer with 3 prongs. The wire is a dedicated 30 amp (2 breakers with tie bar) line ran with 10/3 romex, into the dryer receptacle. (Black & Red hots, White neutral, and bare ground)

Here is where the confusion sets in.

If I was to take a heavy duty extension cord , change the male end to a dryer style 3 prong plug and female end to a welding receptacle, would I be in business? If this is all that is needed, do I use a 10/3 or 10/2 extension cord? What really confuses me is the fact that into the dryer is 10/3, but a 230v welder only uses 3 wires

OR

Do I just run a seperate dedicated line of 10/2 Romex (using the Black & White for hot & plug the bare to ground bar), from a 30 amp tied breaker to a welding receptacle. And run a 10/2 extension cord off the new receptace?

Also, is using Romex for the box to outlet run OK or do I need stranded wire?

I plan on just using a 25ft extension, as the dryer outlet is approx 25 ft from the 200 amp box, giving a 50ft total.

[MoonRise]

Yes. 10/2.

Not needed. Unless you want to. You can use a 50A breaker for the 10/2 for a dedicated welder circuit for that MM175, all code legal and OK because of the duty-cycle exemptions in the NEC for welders and other machinery with duty-cycles.

For a residence, using Romex for the feed from the breaker panel to the receptacle is OK. If the Romex is OK for other circuits, that is. And if the Romex is installed properly.

[jh225]

Yes. 10/2.
OK, So all I would need to do is get a heavy duty extension cord, chop off the ends, male to dryer type, female to welder, correct? (thinking it will be less costly than buying 10/2 by the ft)

Not needed. Unless you want to. You can use a 50A breaker for the 10/2 for a dedicated welder circuit for that MM175, all code legal and OK because of the duty-cycle exemptions in the NEC for welders and other machinery with duty-cycles.But a MM175 only requires a 30amp circuit, correct?

For a residence, using Romex for the feed from the breaker panel to the receptacle is OK. If the Romex is OK for other circuits, that is. And if the Romex is installed properly.Romex is used in residential housing where I am

[MAC702]

12/2 would also be plenty for that machine for your extension cord; and would go a long way. It's up to you how much you want to spend and how heavy a cord you want to roll up. But you also might want the bigger cord anyway for other machines or uses.

The dryer needs a neutral in addition to the ground because it also has some 120V loads inside. Not so with the welding machine. So you will not need the middle neutral prong on the male end of the extension cord, when you change it out to the proper NEMA 14-30 set-up, from the existing NEMA 6-30, see my last paragraph below.

Since the welding machine will work just fine with the 30A breaker, I don't recommend swapping breakers here. Sounds like the dryer is still also going to be used from that receptacle?

But I see another issue here. How is it that your dryer is wired with 10/3 (two hots, neutral, and ground) yet has only a 3-wire receptacle? This is illegal. The cord on the dryer is very easily replaceable, and this is mandatory if you have the 4-wires in the wall.

[jh225]

The dryer needs a neutral in addition to the ground because it also has some 120V loads inside. Not so with the welding machine. So you will not need the middle neutral prong on the male end of the extension cord, when you change it out to the proper NEMA 14-30 set-up, from the existing NEMA 6-30, see my last paragraph below.Not need the neutral? Now I am really confused. If the welder cord has 3 wires (I would assume 2 hots and either ground or neutral), what do I do with the 3rd wire from the extension? AND, could you please explain exactly which plugs you describe as NEMA 14-30 & NEMA 6-30? I am clueless as to electrical terms

But I see another issue here. How is it that your dryer is wired with 10/3 (two hots, neutral, and ground) yet has only a 3-wire receptacle? This is illegal. The cord on the dryer is very easily replaceable, and this is mandatory if you have the 4-wires in the wall.
The dryer circuit was wired from the panel 30 years ago that way. If I change out the outlet, my current dryer which is only 3 wires will not plug in

[MAC702]

...If I change out the outlet, my current dryer which is only 3 wires will not plug in
It cost about $8 to buy a new dryer cord, and it's the legal way to install a dryer in a location that has 4-wire service.

I'm just giving you the Code. Even with the 3-wire receptacle, it's still as safe as all those hundreds of thousands of older installations that still have only a 3-wire service.

Either way, it'll run your MM175 just fine with that extension cord.

[MAC702]

Not need the neutral? Now I am really confused. If the welder cord has 3 wires (I would assume 2 hots and either ground or neutral), what do I do with the 3rd wire from the extension? AND, could you please explain exactly which plugs you describe as NEMA 14-30 & NEMA 6-30? I am clueless as to electrical terms

The welder uses two hots and a ground. It does not use a neutral. A modern dryer uses all four. A NEMA 14-30 is the modern dryer receptacle/plus and has all four. A NEMA 6-30 is the old-style dryer receptacle/plug and only has two hots with a neutral. The ground of older dryers was bonded to the neutral. This is no longer permitted, but older installations are allowed to remain. But if you have all four wires, you should upgrade the receptacle and dryer cord. That's the easy part anyway.

[jh225]

It cost about $8 to buy a new dryer cord, and it's the legal way to install a dryer in a location that has 4-wire service.

I'm just giving you the Code. Even with the 3-wire receptacle, it's still as safe as all those hundreds of thousands of older installations that still have only a 3-wire service.

Either way, it'll run your MM175 just fine with that extension cord.


No, I perfectly understand about the code. Problem is that this dryer does not have a spot for the 4th wire from what I remember, which is why I never changed the old outlet.

Sooooooooo. What do I do with the neutral/ground wire of the cord?

[MoonRise]

A 240V welder only needs 240V (or 220V or 230V, they are all nominally the same voltage). So it needs two hots from a typical breaker panel, and a ground.

An electric clothes dryer often uses 240V for the heater elements and 120V for the little lightbulb and maybe the electric motor as well. The 'new' way to meet those needs is with 4-wire plugs and receptacles, two hots and a neutral and a ground. New dryers will have four connection points under the wiring access panel for those four wires.

If you have an old(er) dryer that only has three lugs under the wiring access panel for the cord to connect to, then just continue using your 3-wire cord and your 3-wire plug and receptacle.

When you replace the dryer with a new unit that has all four lugs and needs a 4 wire cord/plug/receptacle, then update/replace the pieces to all be 4-wire NEMA 14-30 'stuff'. You are lucky that the wire in the wall is 10/3, you won't have to redo that when you get a new dryer. Just replace the outlet with a NEMA 14-30 4-wire dryer outlet and the wall is good to go.

What to do for now with the 'extra' wire? Cap it off with a wire nut or a piece of electrical tape. If you are asking about what to do if the dryer only has three lugs for the cord to connect to, then use a NEMA 6-30 3-wire cord.



The NEMA 6-50, 5-15, 14-30, etc specs are a standard and set of specs (size, arraingement of contacts, etc, etc) for electrical stuff. So if a part says it has a NEMA 5-15 plug on it, you know that you can just plug it into a NEMA 5-15 outlet. btw, NEMA 5-15 is a 'standard' 115V 15 A rated wall outlet in the US (and Canada).

Your Millermatic 175 has a NEMA 6-50 plug on it. Per the manual, you are correct that Miller says to use a 240V 30A breaker to feed the machine. If you were wiring up a dedicated circuit to feed a welder or other duty-cycle limited machine, you -could- use a 50A breaker and 10-AWG wiring in the wall -IF- you label and use that circuit just for the duty-cycle limited machine(s). So no running a 50A heater/wall-oven/motor/etc on that 50A 10-AWG circuit. But because the welder does not run 100% of the time, especially at high output settings, the NEC recognizes and allows things like a 50A 10-AWG circuit for a duty-cycle limited machine like a welder.

So, being less cryptic than my original response, yes you can use your existing 240V 30A dryer wiring to feed your welder. And as you asked, yes just get the desired length of heavy-duty extension cord (or buy the raw cord) and replace the plug/outlet with the desired pieces. In this case you would need a NEMA 6-50R (R for receptacle, or 'female' end) for the welder to plug into and a NEMA 6-30P (P for plug, or 'male' end) to plug into the existing dryer NEMA 6-30R in the wall.

[jh225]

Your Millermatic 175 has a NEMA 6-50 plug on it.
Well, actually, my MM175 has no end, because the fool I bought it from cut it off:nono:

Are you sure it is a 6-50 and not a 6-30? A 50 amp rated plug seems too high for this welder.

I went to the welding store because HD didn't have a plug that will plug into my dryer. It is a NEMA 10-30P and it came with an "L" blade that will work with my dryer. Obviously it is 30 amp rated, just as my circuit is.

What shocked the hell out of me is when I went back to HD to get the plug for the welder and the receptacle for the cord. A 6-30p is like $20 and a 6-30R is $32. I REALLY was not looking to spend $100 (with 25ft of 10 awg wire).

Is that how much a stupid old plug cost in todays world?

Wouldn't the 6 in 6-30 represent the thickness? It seems to me that the 10-30 plug I need for the dryer is way more robust than the 6-30 one.

Please school me on the reason for this.

And also, would I be better off getting 10/3 wire and using the 2 hots plus neutral (which all are stranded) and leaving off the bare copper ground, instead of using 10/2? This being for the extension cord.

I don't really need to use 6AWG wire, do I? That seems like a HUGE overkill

[MoonRise]

Actually the "6" in a NEMA 6-50 or 6-30 is part of the NEMA code that means "straight bladed 240V device". The 30 or 50 means 30A or 50A rating. The "5" in a NEMA 5-15 means "straight bladed 120V device", the 15 means 15A rating. The 10-xxx and 14-xxx mean different things as well. Then there are the Lzz-xx ones, that refer to twist-lock devices. And there are others as well.

If the previous owner cut off the factory Miller plug from the welder (yes, it was a NEMA 6-50 straight-bladed 240V plug), then within reason you can put whatever plug to match that you want to.

If you want to use the existing dryer outlet to power the welder via an extension cord (yes you can, yes it will be just fine and safe and code legal to do so), then get a plug the same as the plug on the dryer cord to go onto the male end of the extension cord and thus plug into the existing dryer outlet.

Next, get an extension cord of the desired length and 'thickness'. I'd go with a 12 AWG 25 feet long or 10 AWG cord 50 feet long. You're just going to get either 'raw' extension-cord stock or you can just cut off the factory molded-on plug and receptacle on a factory cord of the desired length and gauge.

Next, you will need a plug and a receptacle of appropriate amp and voltage ratings for the male end of the welder cord and for the female end of your extension cord. NEMA 6-50 is standard and usually not all that expensive. If you want to use 6-30, or 30+ amp rated 240V twist-locks, you certainly can.

Or you can get fancier and remove the existing now stubbier Miller cord, and wire in a desired length and gauge of cord and just put the plug that matches your existing dryer outlet onto the new cord. That saves the expense of one plug and one receptacle from your bill. You may have to get a new grommet/strain-relief thingy for where the new cord goes into the welder.

And, yeah, the bigger devices are kind of pricey. It's a bit of supply and demand. There are gobs and gobs of 5-15 devices, but 6-30 and 6-50 and other 'big' ones aren't used as much so they cost more. That and they are usually beefier all around than your typical household wall outlet.

[jh225]

OK, Now that I understand about the definition of the plugs, I have a problem.

As stated before, my dryer outlet is run with 10/3 wire and inside the outlet I have 2 hots, a NEUTRAL and a ground.

HERE LIES THE PROBLEM...

The neutral in the outlet IS on the center post of the outlet (because this is just a 3 prong dryer plug)with the ground running to the screw. Therefore, if I was to take my welder which requires a ground, and wire it as normal, the center post in the welder (ground) will now be running to the center post of the dryer outlet (neutral) effectively giving me NO GROUND. Am I correct in my assumption?

If so, won't this be putting me and my house at a huge risk?

I can not rewire the dryer as it is only wired inside the terminal for 3 wire application ( I think, and I will have to check) and I am not buying a new dryer anytime soon.

At this point, it looks to me as my best process would be to run a 10/2 line from the breaker panel, throw on a welding receptacle (2 hots & a ground), and not take the risk.

**** YUP, just checked, the dryer itself has 3 wires (2 hots & a Neutral) in the terminal block, The actual ground wire is attached to the machine itself by means of a screw.****

[Sandy]

Therefore, if I was to take my welder which requires a ground, and wire it as normal, the center post in the welder (ground) will now be running to the center post of the dryer outlet (neutral) effectively giving me NO GROUND. Am I correct in my assumption?

The so-called neutral is now called a "grounded conductor" and is or should be tied with all the grounds back at the service entrance panel. It is in effect grounded and the only time it is a conductor is when used as the neutral on 120 volt circuits, then it is a current carrying conductor. So electrically it works fine when used as the ground with a 240 only type circuit such as your welder which is not a dual function appliance. The green ground from your welder plug would connect to the white (neutral) of the dryer receptacle.

[jh225]

It is in effect grounded and the only time it is a conductor is when used as the neutral on 120 volt circuits, then it is a current carrying conductor.

"In effect" is what worries me.

If I was to take a meter and put it on the "neutral" White wire from the dryer circuit, would it not show current? And if so, wouldn't this current flow to the welder?

Obviously, I would prefer to use the dryer outlet because it is there already, but not at the risk of my house acting like a Zippo.

If I have to run a new line, I will. Just want to be sure it is safe to run it this way. (I know it will work, but is it safe?)

[Sandy]

If I was to take a meter and put it on the "neutral" White wire from the dryer circuit, would it not show current? And if so, wouldn't this current flow to the welder?

From the neutral white wire to what :),,, ground or to something else?? First you are at this time measuring for voltage, not current. If you were to measure from an idle and stand alone neutral, like your dryer circuit, to that ground wire you see there you should read zero or close to zero on the voltage scale and a solid short on the resistance scale. There are rare occassions where you may read some meaningfull voltage. If so that's a different topic. If you measure from a hot wire to 'a' or any neutral or ground or ground potential you should read voltage.

[MAC702]

Okay, don't let us confuse you with an overload of info. I've made a ton of money with a MM175 plugged into a 3-wire dryer outlet. It is as safe as using your dryer.

The dryer receptacle almost assuredly goes directly to the main electrical panel for the house, yes? In this case, the ground bus and neutral bus are already bonded there anyway.

There is no electrical difference in using the dryer's neutral as a ground for your welder. There will be no electrical potential (voltage) present in a properly connected neutral, same as a ground.

[phila.renewal]

Just to stir the pot a little bit, you really should not use the neutral as a ground in ANY circumstance EXCEPT where the circuit serves only a single device (it's technically a code violation to do it anywhere for a new installation, but I'm guessing you won't be calling an electrical inspector ;) ).

If your dryer outlet is fed directly by the panel and does not feed any other circuits, for purposes of your welder, the neutral is equivalent to ground -- it's bonded to ground at the panel and your welder won't know that the insulation is white instead of green.

If instead that dryer outlet feeds other circuits, especially high current circuits, the neutral will actually have a measurable potential to ground equal to the voltage drop in the circuit. All wire has some small resistance and when you flow current through a resistance, it will have a potential across it equal to the voltage drop (E=IR -- voltage equals current times resistance -- pull 50 amps through 1 ohm and you got 50 volts of potential (and likely a wire on fire :p ) from one end of the wire to the other. If you were to touch the neutral (which is bonded to the outside of your dryer when it's plugged in) and something that was actually at ground (a faucet) you would quickly learn why electricians care about that sort of thing.

The voltage usually won't be much, but it is something. If you were to really pull a lot of current downstream of that outlet, it could get high enough to be relevant.

So in the net and back to reality -- if the dryer outlet is dedicated and is not part of another circuit, use it and forget about it -- the welder won't care that the color of the wire insulation on its "ground" wire is white.

[jh225]

So in the net and back to reality -- if the dryer outlet is dedicated and is not part of another circuit, use it and forget about it -- the welder won't care that the color of the wire insulation on its "ground" wire is white.

Yup, and did.

Works just fine. Thanks for all the info. At some point I will probably run a dedicated 10/2 for the welder, but for now, it works just fine.