Running 120v Mig Welder on 220v Outlet

[electromateria]

My mig welder requires 120v and pulls max 25 amps. I want to run it off my dryer outlet power source. My plan is to run a regular dryer plug in the outlet and wire it into my mig welder, using only 1 of the hot connections. I asked chatgpt about the plan and it said:

It is not recommended to wire a 120V mig welder into a 240V dryer outlet using only one hot connection. The reason is that the voltage is too high for the welder and can damage the machine or cause safety hazards.

A 240V dryer outlet provides two hot wires, each carrying 120V, that combine to provide the 240V power required for the dryer. If you only use one hot wire and the neutral wire to power the welder, you would be providing 120V to the welder, which is the correct voltage, but the neutral wire is not designed to handle the full 25A current draw of the welder. This can cause overheating, damage, or fire hazards.

If you want to use the dryer outlet to power your 120V mig welder, you will need to use a step-down transformer to reduce the voltage from 240V to 120V. This will allow you to safely power the welder using both hot wires and the neutral wire of the dryer outlet. Alternatively, you can have a licensed electrician install a dedicated 120V outlet for the welder, which would be a safer and more permanent solution.

To me it just sounds like it's talking a bunch of nonsense, so I figured to be safe I'd ask the real experts before moving forward

What you guys think?

[langwadt]

is the wire size for the neutral smaller than for the hots?

[electromateria]

is the wire size for the neutral smaller than for the hots?

It's standard 10/3 electrical wire. Pics attached.

The black 10/3 wire is from an old dryer. The orange is new 10/3 romex.

[paulca]

Given this is the beginners forum and we talking about fatal voltages...

If you have any doubts about your wiring >100V, you need a local professional.  Not nerds on the internet.

The best part is... if anyone is going to get electrocuted it will be them and not you.

If you feel studied enough that the above does not apply, then why are you asking?

[jonpaul]

try a professional electricians forum, Mike Holt forum.

Use of one side,of 240 V connection is poor practice.

A welder on any household circuit will induce,severe flicker and transients on the same line and breaker panel bus.

Jon

[jpanhalt]

To me it just sounds like it's talking a bunch of nonsense, so I figured to be safe I'd ask the real experts before moving forward

What you guys think?

It's not nonsense.  From a block diagram point of view, your welder will have the welder circuit, and a circuit for everything else.  Is the welder portion a heavy duty transformer?  Will it survive 2X the current, which equals roughly 4X the wattage (i.e., W = I^2R for purely resistive loads).  The everything else, includes controls and so forth.  If they are not designed for 220V, they will pop.  Do you have an electric clothes dryer or stove?  The heater part is 220V, everything else is probably 110V.  The light bulbs in each would burn brightly but not last the night if fed 220V (credit to Edna St. Vincent Millay, 1920).

Your error in buying a 110V welder based on sales videos won't be fixed by plugging it into 220V.  Remember, most Asian imports are stressed even at their published ratings.  Going beyond that present real risk.  At a minimum, you will destroy the unit.

[Jwillis]

The following instructions are based on the ability and competence of end user. If you feel you don't have the competence or knowledge then do not attempt procedures on your own. Please consult a professionally electrician for guidance.
Nothing personal.

Are you competent enough to add a 20Amp circuit to your breaker panel? I added one and run my MasterCraft wire feed MIG on that without any problems. My friend operates his Lincon Wire feed as well without any difficulties.
If you can't install a 20 amp circuit then there is no regulation that states that you can't draw 120V 30amps from a dryer plug. NEC regulations and recommendations End at the outlet. What you plug into that outlet is up to you and at your own risk.
With that being said all you need is the following information.   
The minimum requirement for dryer plug and wire is 30 Amps at 240V.Each 10 Awg wire is rated for 30 amps.

The dryer plug has 2 Lines(live) 120V each , One Neutral(common) and one Earth ground. Connecting line to line is 240V 30 amps. Common is not used. . Connecting  any One of the lines  to Neutral(common) is 120V 30 amps  .You cannot use both 120V lines at full load of 30 Amps each since you only have one Neutral(common) wire rated for 30 Amps.

It's unorthodox to used only one 120V line from a dryer plug but not restricted as long as the load does not exceed 30 amps.
In fact there are no regulations dictating that you cannot draw more amps on a circuit of a specific rating. It is recommended that you don't increase breaker amperage rating because of potential risk of fire.
But I your case you will be OK as long as you use Only One of the 120V Live Lines and the Neutral Common.
Consult the pinouts of the cord and plug and check continuity of each wire and label accordingly. 
If your using a ready made cord. the unused Live wire needs to be terminated and insulated from all other wires and chassis. A simple crimp termination or marette would be fine. You can tape the crimp or marette for added insulation.  Be sure to connect the earth ground  to the chassis of the welder.
 

Hope that helps. And be carefull. 

[jonpaul]

Please see NEC and local electrical codes, most mains connectors, and breakers are de rated eg à 20 A,circuit should not have over 17A loading.

Overloaded electrical are fire hazards.

Your insurance policy may be invalided if an incidents or loss occurs, due to modification of the systems that is not by a liscenced electrician, or that violates NEC or NFPA code.

Jon

[Jwillis]

Please see NEC and local electrical codes, most mains connectors, and breakers are de rated eg à 20 A,circuit should not have over 17A loading.

Overloaded electrical are fire hazards.

Your insurance policy may be invalided if an incidents or loss occurs, due to modification of the systems that is not by a liscenced electrician, or that violates NEC or NFPA code.

Jon

True that breakers are rated at 80% of listed value, but will not break instantly at that 80% value. You can operate a 30 amp breaker for limed time at over 80%
25 amps on a 30amp circuit is 83% . It will work fine without over heating the 30 amp circuit. I can weld just fine on a 20 amp circuit at 120V with no heating of circuit or breaker.
Since the plug is modified by only using 2 of the three lines and not the outlet then no regulations are broken. As said before the NEC recommendations stop at the outlet. NEC  regulations and recommendations do not apply to loads that are not permanently connected to a circuit. This includes appliances and welders.
In Canada  you do not need a licensed electrician to install a circuit. Only an inspection may be required if they show up.

[electromateria]

The following instructions are based on the ability and competence of end user. If you feel you don't have the competence or knowledge then do not attempt procedures on your own. Please consult a professionally electrician for guidance.
Nothing personal.

Are you competent enough to add a 20Amp circuit to your breaker panel? I added one and run my MasterCraft wire feed MIG on that without any problems. My friend operates his Lincon Wire feed as well without any difficulties.
If you can't install a 20 amp circuit then there is no regulation that states that you can't draw 120V 30amps from a dryer plug. NEC regulations and recommendations End at the outlet. What you plug into that outlet is up to you and at your own risk.
With that being said all you need is the following information.   
The minimum requirement for dryer plug and wire is 30 Amps at 240V.Each 10 Awg wire is rated for 30 amps.

The dryer plug has 2 Lines(live) 120V each , One Neutral(common) and one Earth ground. Connecting line to line is 240V 30 amps. Common is not used. . Connecting  any One of the lines  to Neutral(common) is 120V 30 amps  .You cannot use both 120V lines at full load of 30 Amps each since you only have one Neutral(common) wire rated for 30 Amps.

It's unorthodox to used only one 120V line from a dryer plug but not restricted as long as the load does not exceed 30 amps.
In fact there are no regulations dictating that you cannot draw more amps on a circuit of a specific rating. It is recommended that you don't increase breaker amperage rating because of potential risk of fire.
But I your case you will be OK as long as you use Only One of the 120V Live Lines and the Neutral Common.
Consult the pinouts of the cord and plug and check continuity of each wire and label accordingly. 
If your using a ready made cord. the unused Live wire needs to be terminated and insulated from all other wires and chassis. A simple crimp termination or marette would be fine. You can tape the crimp or marette for added insulation.  Be sure to connect the earth ground  to the chassis of the welder.

Hope that helps. And be careful. 

Huge help! Appreciate ya!! The chatbot threw me off with it's nonsense and I needed to make sure.

Don't worry, I'll be very careful and take my time.. plus it's a relatively simple job. I understand the risk involved.

Any time I don't feel confident, or understand at a level that will keep me safe, I won't move forward.

I'd love to install new breakers and circuits, I'm sure I could do a very clean job, but the forum already made me realize that's a bad idea because of insurance / liability issues.

[tychob]

The dryer plug has 2 Lines(live) 120V each , One Neutral(common) and one Earth ground. Connecting line to line is 240V 30 amps. Common is not used. . Connecting  any One of the lines  to Neutral(common) is 120V 30 amps  .You cannot use both 120V lines at full load of 30 Amps each since you only have one Neutral(common) wire rated for 30 Amps.

This is not necessarily true, there's a concept called a MultiWire Branch Circuit. See https://twielectric.com/national-electrical-code-multiwire-branch-circuit/ Because of the fact that the two 120V hots are 180 degrees opposed phases, the currents on the neutral from the two lines (mostly) cancel, so each hot can be used up to the full 30A rating, even though there is only a single neutral is only rated up to 30A. You still need a common trip breaker though like a 240v circuit. However its not useful for a single device, because you can't use two hots without a transformer anyway.

So long as the dryer outlet is a correctly wired 14-30, and not a 6 or 10 series or something else with a messed up ground, the neutral load shouldn't be a problem to wire up a plug with one hot just not connected.

[Jwillis]

This is not necessarily true, there's a concept called a MultiWire Branch Circuit. See https://twielectric.com/national-electrical-code-multiwire-branch-circuit/ Because of the fact that the two 120V hots are 180 degrees opposed phases, the currents on the neutral from the two lines (mostly) cancel, so each hot can be used up to the full 30A rating, even though there is only a single neutral is only rated up to 30A. You still need a common trip breaker though like a 240v circuit. However its not useful for a single device, because you can't use two hots without a transformer anyway.

So long as the dryer outlet is a correctly wired 14-30, and not a 6 or 10 series or something else with a messed up ground, the neutral load shouldn't be a problem to wire up a plug with one hot just not connected.

That configuration does not apply to a dryer nor a electric stove outlet on a split phase system. Regulations dictate that a dryer outlet can be no less than 30 Amps and  range outlets are no less than 40 Amps , The outlets described in the link you provided is for 120V 15 Amp outlets. Dryer and stove wiring is 10 AWG not 14AWG.

On a split phase system the transformer outside has a primary with Hot and Neutral . On the secondary has Three wires Hot neutral hot , exactly the same as a transformer with a single coil primary and a centre tapped secondary. Yes relative to neutral or  centre tap each 120V winding is 180^o.  But the  two taps from either end of the secondary coil is 0^o phase 240V.

[Jwillis]

Split phase to a residence is set up exactly like the diagram below.

[james_s]

try a professional electricians forum, Mike Holt forum.

Use of one side,of 240 V connection is poor practice.

A welder on any household circuit will induce,severe flicker and transients on the same line and breaker panel bus.

Jon

They won't help you. That forum is for professional electricians only, nobody else is welcome and giving advice to us ordinary serfs is strictly forbidden.

[langwadt]

.You cannot use both 120V lines at full load of 30 Amps each since you only have one Neutral(common) wire rated for 30 Amps.

two 30A 120V load are the same as a single 30A 240V load, no current in the neutral

[EPAIII]

I don't understand. You seem to be showing coils of wire on a workbench. The question is what is the wire IN THE WALLS between the breaker box and the dryer outlet. That is what counts, not some extra wire you have sitting around.

This is not a shock hazard situation. It is a FIRE hazard. If the neutral conductor is too small, it can heat up and start a FIRE inside the walls. You don't want that. There could be a delayed reaction. It may work OK for minutes, hours, days, weeks, months, even years and then, ONE DAY you are standing on the curb looking at the smoking ashes that the fire trucks are hosing down. And wondering if your insurance payments are up to date.

You obviously do not know the issues involved. If you want to do this, get a qualified electrician to inspect the wiring. But I would just have a new circuit installed for the welder. Money well spent!

is the wire size for the neutral smaller than for the hots?

It's standard 10/3 electrical wire. Pics attached.

The black 10/3 wire is from an old dryer. The orange is new 10/3 romex.

[sokoloff]

You cannot use both 120V lines at full load of 30 Amps each since you only have one Neutral(common) wire rated for 30 Amps.

You can use both simultaneously at the rated amperage. If you use both at once, there is current in both line wires and none on the neutral. If you use only one, there is current in one line wire and on the neutral and none on the other line. Pulling 25A @ 240V causes the same amount of heating in the supply wires as pulling 25A @ 120V or as pulling two different 25A @ 120V loads on opposite legs. (Imagine a massive 10 ohm resistor with a center tap. Connect the ends across the 240V supply. Everyone agrees that 24A will flow through the resistor and each of the supply lines. Now, connect the center tap of that resistor to the neutral. Nothing changes.)

But I your case you will be OK as long as you use Only One of the 120V Live Lines and the Neutral Common.

This is true but slightly misleading. As above, you would also be safe if you used both 120V lines with the full rated amperage at the same time.

there's a concept called a MultiWire Branch Circuit. See https://twielectric.com/national-electrical-code-multiwire-branch-circuit/ Because of the fact that the two 120V hots are 180 degrees opposed phases, the currents on the neutral from the two lines (mostly) cancel, so each hot can be used up to the full 30A rating, even though there is only a single neutral is only rated up to 30A. You still need a common trip breaker though like a 240v circuit.

This is overwhelmingly correct, except for a small detail in the part I added italics to. You only need a common-disconnect breaker, not a common-trip breaker. (Two single breakers connected with an accepted/recognized handle tie will suffice; those will be common disconnect but not common trip.)

I don't understand. You seem to be showing coils of wire on a workbench. The question is what is the wire IN THE WALLS between the breaker box and the dryer outlet. That is what counts, not some extra wire you have sitting around.

The dryer outlet is on a 30A breaker and fed with 10/3 wire in the walls (assuming the building was built to code). The duty cycle on a small mig welder is so low that there is no fire hazard here. I wouldn't be surprised if the welder's power cord had 14 or even 16 gauge wire.

[sokoloff]

If you've got a lot of shop type projects coming up, I'd recommend having a look at garagejournal.com. They have a lighting/electrical forum that is filled with the typical mix of people who know what they're talking about and people who distinguish themself as not being those people, but it's way more friendly to DIYers than Mike Holt's or HeatingHelp.

[jonpaul]

.... a 240V outlet is not designed for 120V unbalanced load. Neutrals may be same or smaller guage wire than the L1, L2.

James,
we have used Mike Holt and electricians forums for years with fine advice and research.
No requirement for professionals only.

https://www.mikeholt.com/      has seminars, courses, products and a forum.

Mike is a scion of electric safety and compliance.

Jon

[barshatriplee]

I think you have to use a 3000 Watts AC Voltage Converter Transformer 220v to 110v.

[tychob]

.... a 240V outlet is not designed for 120V unbalanced load. Neutrals may be same or smaller guage wire than the L1, L2.

For a feeder this is allowed to a certain extent, but this is a branch circuit. If the circuit is to code (which may be an unreasonable assumption) then by my understanding the neutral wire is required to be equal to the maximum branch ampacity, specifically in case the user plugs in an unbalanced load in future. See https://forums.mikeholt.com/threads/neutral-of-a-branch-circuit-be-reduced-in-size.149599/

[Jwillis]

.You cannot use both 120V lines at full load of 30 Amps each since you only have one Neutral(common) wire rated for 30 Amps.

two 30A 120V load are the same as a single 30A 240V load, no current in the neutral

Yes you are correct . My mistake.

[james_s]

This is not a shock hazard situation. It is a FIRE hazard. If the neutral conductor is too small, it can heat up and start a FIRE inside the walls. You don't want that. There could be a delayed reaction. It may work OK for minutes, hours, days, weeks, months, even years and then, ONE DAY you are standing on the curb looking at the smoking ashes that the fire trucks are hosing down. And wondering if your insurance payments are up to date.

This should never happen. You will never find a 240V outlet with neutral (in the USA at least) where the neutral conductor is smaller than the live conductors. The two hots are 180 degrees out of phase so they can't be used together to power a single 120V load and the load on the neutral wire can never be higher than that carried by one of the hot wires.

I have never seen a 120V-only welder that draws 25A though so I'm skeptical of this whole deal. The biggest standard 120V receptacle is 20A, there are 30A and larger sizes used for boat and RV shore power but that would be a strange choice for a welder. Are you sure the welder isn't dual voltage? I had one that could be set to 120 or 240V.

[Monkeh]

.... a 240V outlet is not designed for 120V unbalanced load. Neutrals may be same or smaller guage wire than the L1, L2.

The NEMA 14-30 is in fact designed to handle full load current on all contacts, and 10/3 wiring will provide the same gauge wire for both lines and neutral.

[Jwillis]

This is not a shock hazard situation. It is a FIRE hazard. If the neutral conductor is too small, it can heat up and start a FIRE inside the walls. You don't want that. There could be a delayed reaction. It may work OK for minutes, hours, days, weeks, months, even years and then, ONE DAY you are standing on the curb looking at the smoking ashes that the fire trucks are hosing down. And wondering if your insurance payments are up to date.

This should never happen. You will never find a 240V outlet with neutral (in the USA at least) where the neutral conductor is smaller than the live conductors. The two hots are 180 degrees out of phase so they can't be used together to power a single 120V load and the load on the neutral wire can never be higher than that carried by one of the hot wires.

I have never seen a 120V-only welder that draws 25A though so I'm skeptical of this whole deal. The biggest standard 120V receptacle is 20A, there are 30A and larger sizes used for boat and RV shore power but that would be a strange choice for a welder. Are you sure the welder isn't dual voltage? I had one that could be set to 120 or 240V.

They're light application welders with a 20 - 30% duty cycle. They can be either stick or wire feed . Wire feed come with flux core wire but can be outfit with regulator for CO² or Argon . Depends what your welding steel or aluminum.  https://ch-delivery.lincolnelectric.com/api/public/content/6962ab0875394b6983c4ee36019ec119?v=6827a082 or https://ch-delivery.lincolnelectric.com/api/public/content/607c8be3007042339a4707f1571b9907?v=303b9338

Some are convertible to 240V some are not. Not sure what brand the OP has but he should check to see if his is convertible to 240V. That would be the easiest most logical solution.