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Connecting from NEMA L16-30P to NEMA 5-10R

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Mar 19, 2010
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I have a welding machine which runs off of 460 volt 3 phase power and has a cord with a NEMA L16-30P. The machine has a constant voltage concerter so I was told I could automatically plug into a different voltage as long as it was the same phase power and to change phase I just would isolate the L3 wire to convert to to single phase.

I have it wire to the NEMA L16-30P with L1 (X) being the black wire, L2 (Y) being the white wire, and L3 being the red wire (Z). The Ground is the green wire (G).

I need to connect to a NEMA 5-10R where the connection is one hot wire, a neutral and a ground.

My welding machine does not have a neutral so how to I go from a NEMA L16-30P to a NEMA 5-10R

 
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No offense, but I'd really suggest having an electrician take a look at this. 480 V equipment can really bite you.

You should be more concerned about the actual voltage and phasing connected to the receptacle and not the pin configuration.

You should make sure you have a copy of the welding machine installation manual and verify what you were told.



David Castor
 
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No disrespect intended, but you are way out of your realm here, please consult a professional. What you are trying to do is not only dangerous but illegal. There is a reason why plugs and receptacles of different voltages and current ratings are made so as to NOT connect together.

Just FYI, if your welder is going to take 30A at 480V 3 phase (by virtue of the L16-30P plug on it) and it is a "constant voltage concerter" (whatever that means), the CURRENT that is will draw at 120V single phase (the NEMA 15-20R) will be 4X the current at 480V AND 1.732X the current again because of it coming from a 1 phase source. So you would need 207A at 120V.

See why we say you need to talk to a professional?

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jraef,

You've hit on the the reason why professionals install fuses and circuit breakers: to protect the installation against users. [smile]


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What is a NEMA 5-10R?
I can't find a listing for it. If it follows the NEMA 5 nomenclature it would be 10 Amp 120 Volt receptacle. Unfortunately my references only cover devices rated 15 Amps and up.
Hire an expert.

Bill
--------------------
"Why not the best?"
Jimmy Carter
 
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This is entirely a function of the power supply in the welder. I would not expect this to work, but what do I know. You are basically connecting 120 V single-phase to equipment designed for (based on the plug) 480 V three-phase. And you will be grounding one of the connections that was at 277 V volts to ground when operating at 480 V.

I'd open the circuit breaker at the panelboard before plugging it in and turn your head when you close the breaker back in.




David Castor
 
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Make sure that you have the green wire connected to the ground terminal of the cord cap. (Plug end, NEMA 5-20R)
The other wires don't matter. connect them wherever they seem to fit the best. It won't make any difference and it won't work.
If your welder has a three phase fan you may be able to burn it out. The connections still don't matter that much.
About the only thing that is important is proper grounding. Green wire to ground screw. It may be colored green also. This is for safety. There is no "Right" way to feed a three phase 460 Volt machine with single phase 120 Volts so it really doesn't matter which wrong connection you use.
As was mentioned, turn the breaker off before plugging this in. Turn the breaker on with your left hand while standing to one side with your face turned away.

Bill
--------------------
"Why not the best?"
Jimmy Carter
 
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All I can add is that you should set up a video camera to record the whole sordid tale and then instruct your heirs to post it to Youtube in the Darwin Awards category.
 
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diverdileo,

What Miller have achieved there is interesting. From the datasheets these units seem to be able to do some work - albeit at limited output current - from a 115V supply, so I think the guys above have been more than a little unfair.

The Dynasty 200 DX model requires that you connect the white and black conductors to L1 and L2, and insulate the red conductor. I don't know what model you have, but see if you can find the owner's manual at The instructions are very clear.

Good luck. The rest of you.... are a disgrace. [poke]



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I understand connecting the four wires for three phase and leaving the red isolated for single phase

but a nema 5-10r receptacle has a hot, a neutral, and a ground and the machine did not have a neutral wire but miller tells me isolate the red and to hook up the green to the ground. And then black or white to the hot and the remaining hot to the neutral.


 
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RTFM
What part of
but a nema 5-10r receptacle has a hot, a neutral, and a ground and the machine did not have a neutral wire but miller tells me isolate the red and to hook up the green to the ground. And then black or white to the hot and the remaining hot to the neutral.
Click to expand...
do you not understand.

Why are you bothering us when you have clear instructions.
What does a NEMA 5-10R look like. I can't find a listing out of almost 80 NEMA configurations in my code book.

Bill
--------------------
"Why not the best?"
Jimmy Carter
 
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I did not understand connecting a hot to a neutral. I thought a hot had to be connected to a hot and a neutral to a neutral. But I did not get that from the user manual or this forum. It took me calling miller several times after my original post but the rep was very clear and I just wanted to share the final solution here.

Thanks for all those who provided feedback. I am a welder and inspector, not an electrician. Professions know what to do but experts understand why. The why is what I was looking for.

I use this forum to learn- mission accomplished?

 
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I own a plasma cutter that works in a similar way. The unit is capable of running on 240V or 120V single phase. However the plasma cutter can only be turned up to half amperage when fed with 120V single phase.
 
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