# 220V 3-Prong 4-Prong Receptacles



## erikmannie (Mar 7, 2022)

I have a 220V Miller Dynasty 210DX that is currently wired up with a 4-prong plug (first photo) & receptacle. My Dad helped me wire it up on a 45A circuit; he has wired up a lot of electric clothes dryers, but he had not wired up a welder up until that day.

My 2 other 220V Miller machines (Millermatic 252, Thunderbolt 210) came with a 3 prong plug (second photo) that is very common.

I would very much like to change the (4-prong, male) plug on my Dynasty to the same (3-prong, much more common) plug as my other 2 machines. I want to do this because now I am going to need an extension cord, and I want to have a single extension cord that I can use for all of my machines.


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## erikmannie (Mar 7, 2022)

I really don’t understand how it works, but I think that the Dynasty has a Line 1, Line 2, Ground & Neutral. I believe that the Dynasty can be run on 3 phase (which I have no interest in doing).

The Dynasty may have an autodetect functionality, but I don’t know if it’s autodetecting between 110V & 220 V, or between single & three phase.

Hopefully, I can remove the 4-prong from the Dynasty, & use the same 3-prong used on the other 2 machines.

I Googled this a little bit, and I found the following picture. Also, I am including a screenshot of a relevant comment.


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## ttabbal (Mar 7, 2022)

The question is, does the machine use the neutral? If not, you can switch to 3 prong. Just one person's experience, but most 220V stuff I have doesn't use neutral. Sometimes the cord doesn't even have the wire for it, it just comes with the 4-prong plug as it's more common on new construction. But sometimes the designers get "clever" and use it for 120V in the machine for some reason. 

Looking at the photos for that machine you found, it looks like you don't need neutral and can just swap over. Ignore red, wire per the photo. Which wire goes to L1/L2 doesn't matter, ground is the other one.


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## erikmannie (Mar 7, 2022)

I never understood why the Dynasty came with no plug. I imagine it is because some people would want to hardwire it, some people would want to run three phase, and somebody like myself would like to have a corded single phase plug.

Accustomed to hooking up dryers, my Dad probably wanted 4 prongs for 4 wires.

Hopefully, somebody here can point me in the direction of how to make the cord match the cords on my other two 220V machines.

The existing circuit is 220V, with a 45A circuit breaker.

I have a rotary phase converter with 20A & 30A receptacles. I am pretty sure those circuit breakers are too small to use with my 210A inverter welder (Dynasty 210DX).

I do have room on the RPC to add a larger receptacle, but it is only a 10 HP RPC, & I don’t know what benefit I would gain by running this welder on three phase.


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## erikmannie (Mar 7, 2022)

ttabbal said:


> The question is, does the machine use the neutral? If not, you can switch to 3 prong. Just one person's experience, but most 220V stuff I have doesn't use neutral. Sometimes the cord doesn't even have the wire for it, it just comes with the 4-prong plug as it's more common on new construction. But sometimes the designers get "clever" and use it for 120V in the machine for some reason.
> 
> Looking at the photos for that machine you found, it looks like you don't need neutral and can just swap over. Ignore red, wire per the photo. Which wire goes to L1/L2 doesn't matter, ground is the other one.


Is the reason that L1 and L2 don’t matter is because it is AC?

With my 3 phase, 220V lathe, L1 & L2 dictated which direction the chuck rotated with the operating lever in the up position. I hooked it up backwards the first time. I’m sure some people like to start their lathe by pushing the lever down for forward rotation.

I wanted to start my lathe by putting the lever in the up position. Switching L1 & L2 made this happen.

I have some DC ebike motors with three 10 gauge motor wires (aka phase wires) that go from the motor to the controller. One of the ways that you can connect these will result in the motor running backwards. The easy way to fix this is by switching these 2 wires, and then the motor runs forward.

Is there any risk at all that I could fry the circuit board on the Dynasty if I hooked up the wires wrong?


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## ttabbal (Mar 7, 2022)

Single phase 220 is actually just two 120V phases 180 degrees out of sync. Between the two hot wires, you get 220V. Either one to ground will get you 120V. Newer equipment gets angry if you do that, and wants a dedicated neutral for 120V. And it did create a shock hazard as "ground" could actually have some stray voltage on it. But in your panel, neutral and ground are connected. Just don't treat them as the same thing, or you create the possible safety hazard they added the separate line to fix. That was a bit long-winded to say what amounted to "because it's AC" I guess, but you seem the type that likes to get info.  

220V like this doesn't need a neutral and current flows basically between the two phase wires. It doesn't "need" ground either, but ground is included for safety. You connect the metal case of the equipment to ground, and any stray voltage flows there instead of into the unwary person touching it. 

It's a bit oversimplified, but you don't need all that just to connect a welder safely.  

3 phase is each phase 120 degrees off from the next. It works similarly between phases, but they way the motors work is that alternating poles are on different phases, so the magnetic field is almost rotating itself around the motor. Switching two wires changes the relationship, making the motor spin the other way. Again, simplified, and I'm not positive I totally understand it. Tesla, I am not.  "Brushless DC" motors are just 3 phase motors. The marketing folks got involved. The 3 phase wires are usually just L1/L2/L3, and your lathe likely just swapped two of them around when you did that. Same thing, just more complex switching setups. 

There is some risk to the welder, but it's quite low. In theory, running hot to the ground side could cause a problem. But if you follow the directions using the color codes, you'll be fine. And better manufacturers would design fail-safe setups to prevent it. I can't imagine Miller didn't. If it's rated for 220V/45A single phase, I wouldn't bother with setting it up for 3 phase input. That's a pretty commonly available setup. I would guess they included 3 phase input as an option for industrial users for convenience. I suspect inverter welders work like VFDs, converting it into a strong DC source, then using switching transistors to create the output. 

It's pretty common for multi-input devices like that to not include plugs. There is little standardization for plugs in this range, so they often just have the user source whatever they need for their shop. I might worry that an import machine would have incorrect colors, but Miller wouldn't do that. If for no other reason than the liability it would create would be shut down by the legal department. The lawyers cost a lot more than the right wire.


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## rabler (Mar 7, 2022)

Do you have the manual for the welder?  That probably has wiring options.

If not, one approach is to look at the welder end of the cord.  If it terminates in a jumper block that is labeled L1/L2/L3 and GND  then you can _probably_ assume that it is indeed single or three phase and that 4th wire is not really doing anything in your configuation.  If if is labeled as L1/L2/N and GND then you need the 4th wire as is.


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## mksj (Mar 7, 2022)

The manual explains the connections, it can either be run off of single phase or three phase. The 240VAC connection does not use the neutral. The plug is modular so you can remove the neutral prong which is the L shaped one and use as a 3 prong connector. The blades are for L1 and L2, the U shape is ground. The connections for the Miller cord (see below), L1 is BLACK, L2 is WHITE, L3 is RED which is not used in single phase operation. A bit confusing because typically white is used for neutral, which would be used for 120VAC operation when applicable.  There is also a YouTube showing how to make the connections. If the plug was wired with 4 prongs and neutral was used for your welder, it would appear to be incorrect for 240VAC single phase operation.

Unfortunately it seems like this forum no longer supports higher resolution documents.


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## WobblyHand (Mar 7, 2022)

mksj said:


> Unfortunately it seems like this forum no longer supports higher resolution documents.


A real downgrade, in my humble opinion.  Actually bothers my eyes, because they are trying to focus on the unfocusable (blurry images due to severe image compression).


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## erikmannie (Mar 7, 2022)

Thanks to everybody for the very helpful information. My excuse for not digging out the manual is because I am on the road.

It looks like this affordable male receptacle is acceptable:






						Leviton Plug Gnd Dual 30-50A Blk (00930-00E) | Zoro
					

Order Leviton Plug Gnd Dual 30-50A Blk, 00930-00E at Zoro.com. Great prices & free shipping on orders over $50 when you sign in or sign up for an account.




					www.zoro.com
				




Picture:


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## gunsmither (Mar 7, 2022)

I have the same Miller welder. I run it in 240 single phase on a 30 amp circuit. Perfect for the small work I do. I put a 30 amp 240 plug on it.
Very nice machine. I run an air torch, perfect for 90% of anything I do. Also have a water cooled set up with cooler, but seldom use it.


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## erikmannie (Mar 7, 2022)

gunsmither said:


> I have the same Miller welder. I run it in 240 single phase on a 30 amp circuit. Perfect for the small work I do. I put a 30 amp 240 plug on it.
> Very nice machine. I run an air torch, perfect for 90% of anything I do. Also have a water cooled set up with cooler, but seldom use it.


I wonder if you could upload a picture of your male receptacle. I am curious if it is that really common 3-prong configuration seen here:


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## gunsmither (Mar 7, 2022)

erikmannie said:


> I wonder if you could upload a picture of your male receptacle. I am curious if it is that really common 3-prong configuration seen here:
> 
> View attachment 399449


I'll take a pic of it and post it ASAP!


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## jmkasunich (Mar 8, 2022)

erikmannie said:


> I wonder if you could upload a picture of your male receptacle. I am curious if it is that really common 3-prong configuration seen here:
> 
> View attachment 399449


He said he put a 30 amp plug on it.  Your picture shows a 50 amp plug.

NEMA 6-50 can be read as follows: 
The 6 means 2 hots (single phase, 240V between hots), 1 ground, no neutral
The 50 means 50 amps.

The first number is rather arbitrary, you need a magic decoder ring.  Some other values are:

1: one hot, one neutral, no ground.  120V between hot and neutral.  1-15 is the old-fashioned 2-prong residential receptacle.
5: one hot, one neutral, one ground.  120V between hot and neutral.  5-15 is your vanilla 3-prong residential receptacle
6: two hots, no neutral, one ground.  240V between hots.
10: two hots, one neutral, no ground.  240V between hots, 120V between either hot and neutral.  No equipment grounding conductor, not very safe.  Deprecated by the national electric code since 1996, should be replaced by type 14.
14: two hots, one neutral, one ground.  240V between hots, 120V between either hot and neutral.  Pretty universal, can run any 120/240V device.
15: three hots, one ground.  Three phase, 240V between hots.  I use the twist-lock version of the 15-30 for all three-phase equipment in my shop.
16: three hots, one ground.  Three phase, 480V between hots.

Not all combinations of type and current rating exist.  Twist-locks exist in many of these types (identified by an L prefix, such as the L15-30 that I use for three-phase stuff).  Twist locks generally aren't available above 30A (except for "california plugs" which are another thing altogether that I won't go into...)


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## gunsmither (Mar 8, 2022)

Here are some pics of my *"30 amp plug" Not! My bad!* I actually have it hooked up to a 20 Amp/240 volt plug and receptacle. Been years
since I hooked it up, and relied upon my faulty memory thinking it was 30 amps. My old welder, a Miller 250 Synchro was hooked up to a 50 amp
circuit. I used that circuit, but changed the breaker to a 20, tapped on some #12 to the 20A receptacle, with a 20A plug for the newer, much quieter Dynasty. Mostly run very low amps, like "3" for some stainless wire loops I make. Most I ever ran it was at about 120A if I recall.


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## pontiac428 (Mar 8, 2022)

You should not use neutral, only two phases and ground.  While it is possible that there are welders out there that do use neutral, I've never seen it.  My big Miller TIG welder has a 110v power outlet in the back that I use for running coolant, but that circuit gets its 110v leg from a tap on the transformer.

I think you'd be in violation of NEC for connecting neutral, because the appliance can draw an unbalanced load using the neutral rail.  Your GFCI would trip (I am required to run GFCI on all circuits with receptacles in my locality, and I bet California is the same).

You can pull a lot more than 50A through a 3-prong 30A circuit.  Welders don't have startup current, and the code for rating receptacles and breakers was made for circuits with motors.  Welding loads are intermittent and low duty cycle.  My 70A plasma has a big 6ga whip and a factory molded 50A plug.  With the hours I've run the machine, it would have burnt to the ground by now if that 50A plug and receptacle weren't enough.

Caveats and warnings, lawyers and due diligence, blah blah YMMV, I'm not responsible for anything, just saying, it's the internet, have a nice day!


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## tq60 (Mar 9, 2022)

gunsmither said:


> Here are some pics of my *"30 amp plug" Not! My bad!* I actually have it hooked up to a 20 Amp/240 volt plug and receptacle. Been years
> since I hooked it up, and relied upon my faulty memory thinking it was 30 amps. My old welder, a Miller 250 Synchro was hooked up to a 50 amp
> circuit. I used that circuit, but changed the breaker to a 20, tapped on some #12 to the 20A receptacle, with a 20A plug for the newer, much quieter Dynasty. Mostly run very low amps, like "3" for some stainless wire loops I make. Most I ever ran it was at about 120A if I recall.


This looks like a 120 vac plug.

The 240 vac version has both blades horizontal if I recall correctly.

They were common for older windows ac units maybe.

Sent from my SM-G781V using Tapatalk


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## pontiac428 (Mar 9, 2022)

The 20A plug above is typical for electric ranges/ovens.  One vertical is more common nowadays than two horizontal.  There is a similar but not interchangeable 110v version for applications over 15A.  Pretty rare to encounter.

I started using twist-locks when I set up 3 phase.  I think they are probably the better option, since they are designed to be plugged and unplugged repeatedly compared to appliance receptacles, which are meant to be plugged in and left that way for use.  None of the plug and receptacle standards are that different in price, so it's best to pick one and stick with it.


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## keeena (Mar 9, 2022)

tq60 said:


> This looks like a 120 vac plug.
> 
> The 240 vac version has both blades horizontal if I recall correctly.



The plug in gunsmither's post is in-fact a 240v, 20a plug (NEMA 6-20P). It can be easily confused with a 5-20p (120v 20a). Only difference is that the horizontal and vertical blades are swapped as compared to the NEMA 6-20p.

The double-horizontal blades do exist as well: 240v-15a (approx same physical size as the 20a plugs) and 30a (larger and wouldn't be confused with the standard sized plugs most folks in the US are used to)


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## keeena (Mar 9, 2022)

erikmannie said:


> I wonder if you could upload a picture of your male receptacle. I am curious if it is that really common 3-prong configuration seen here:



@erikmannie  - are you thinking of trying to away with a 30a circuit (breaker, wire gauge, receptacle, plug)? Your photo is showing a 50a plug, so I'm a bit confused as to what/why you're asking...


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## erikmannie (Mar 9, 2022)

@keeena

The circuit breaker is 40A.

I plan to use a 50A male receptacle, specifically a NEMA 6-50P, for my Dynasty 210DX. I am pretty sure that is the same male receptacle that is on my other 2 Miller 220V welding machines.


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## gunsmither (Mar 9, 2022)

keeena said:


> The plug in gunsmither's post is in-fact a 240v, 20a plug (NEMA 6-20P). It can be easily confused with a 5-20p (120v 20a). Only difference is that the horizontal and vertical blades are swapped as compared to the NEMA 6-20p.
> 
> The double-horizontal blades do exist as well: 240v-15a (approx same physical size as the 20a plugs) and 30a (larger and wouldn't be confused with the standard sized plugs most folks in the US are used to)


It is indeed a 20amp 240 volt plug and receptacle. It just dawned on me why I used a 20 amp setup. I had 20 amp / 240 V outlets already installed
in several other locations in my shop / garage for a small compressor I used to own, and for a heat treating oven. I figured if I ever wanted to tig
something in some other location, I would be able to wheel it around to wherever I might want.


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## keeena (Mar 9, 2022)

erikmannie said:


> The circuit breaker is 40A.
> 
> I plan to use a 50A male receptacle, specifically a NEMA 6-50P, for my Dynasty 210DX. I am pretty sure that is the same male receptacle that is on my other 2 Miller 220V welding machines.



Gotcha. Yes: your other Miller machine should be a 6-50P (that's what my 220v single phase Millermatic 252 has on it  )

I personally wouldn't use receptacles which are higher amp rating than the circuit. Its mostly safe in the sense that the CB should trip if you exceed 40a...just not something I would do. At least make sure the wire itself can handle what you're doing; you don't want that to be the weak link.

Anyway - you know how you're using your equipment so I'll just echo Pontiac428's disclaimer.


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