220V 3-Prong 4-Prong Receptacles

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.
 
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.
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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:

EDEA97D8-84AC-4A07-B70D-8E6603A93FAA.jpeg
 
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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
Click to expand...
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...)
 
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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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!
 
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.
Click to expand...
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
 
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.
 
tq60 said:
This looks like a 120 vac plug.

The 240 vac version has both blades horizontal if I recall correctly.
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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)
 
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:
Click to expand...

@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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