240V 50 amp outlet on 30 amp circuit

[Cruisinga]

I am wiring two 240v receptacles in my garage for plasma cutter and mig welder.
I have two spare 30amp double pole breakers and 10/2 romex.

Both tools have 50 amp plugs, but max input currents of 19-22 amps. The only device I expect to add (tig welder) has a similar draw.

I don't see an issue with 50 amp receptacles wired with 10/2 since the wire is protected by the 30 amp breaker.
I guess I don't see how this is different than the supposedly acceptable 50 amp receptacle on 40 amp circuit.

 

[wyliesdiesels]

By code, u cant put anything but a 30a receptacle on a 30a circuit. Same thing for 50a circuits. 40a circuits are an exception since there is no 40a receptacle...

 

[alfredeneuman]

Depending on the Duty Cycle of the welder it may perfectly OK by Code to use #10 but with a 50 amp breaker instead of the 30 amp.
The plasma cutter is a different story altogether.

 

[wyliesdiesels]

Depending on the Duty Cycle of the welder it may perfectly OK by Code to use #10 but with a 50 amp breaker instead of the 30 amp.
The plasma cutter is a different story altogether.

That only applies to circuits used exclusively for welders. He couldnt use anything else on that outlet and since he mentioned the plasma cutter, i didnt bother going down that route...

 

[pattenp]

By code, u cant put anything but a 30a receptacle on a 30a circuit. Same thing for 50a circuits. 40a circuits are an exception since there is no 40a receptacle...

I understand NEC to allow a 50A outlet on a 30A circuit if it's a single outlet circuit ( 210.21(B)(1) ). The only restriction is the outlet is not to have a amp rating less than the circuit. There is no restriction to the outlet being a higher rating than the circuit. But, on circuits with two or more outlets you need to use the values listed in table 210.21(B)(3) which would limit a 50A outlet to a 40A or 50A circuit.

 

[sberry]

This aint my first rodeo either. You can connect a 14 to a 50A outlet with a 30A breaker. You can connect the 10 to a 50 with a 50A and a plasma is considered a welder, same plug and service requirements.

 

[alfredeneuman]

pattenp and sberry,

Both of you are right and I'm wrong!

Sorry about that

 

[sberry]

Anyway,,,,,,,,,,,,,,,,,,,,,,,,, simple answer is,,, your plan for a 10/30 circuit is a good one. The wire is 2 sizes better than the machine you are connecting to it needs if these are compacts.
I point this out but don't mean I am a fan either of minimum wire size. I don't think every circuit needs upsize from code minimums but... a 10 wire lets this machine be all it can be especially at distance, the connections are better at recepts and terminations. I have never had a problem with a welder that comes with a 50A on a 10 wire including units 2x the size.
I have a bud that just pushed a buzzer out the door and got new 211 and a small plasma. He has an old fuse box, there are no more spaces. The air comp is wired to the feed thru and the welder to the range.
So he is going to get all complicated and I suggest splitting the 8 and putting 2. He figured it out, took a 12 and added a wire to the recept,,, for another one. I know, not sposed to use the device as a splice but it looked tight and it was on a block wall,,, wtf.

 

[Cruisinga]

Thanks for the help guys. It 'felt' ok but I don't know the code very well.

 

[sberry]

Feel free to elaborate and in general the ideal is a breaker that matches the recept as well as the wire, there are some exceptions for the wire on dedicated equipment and welders, most of the equipment is not recept connected but hard wired as are welders requiring circuits over 50A.

 

[sberry]

For example an AC 225 has a 12 cord and lists a 12 wire, single circuit in pipe and a 50. The notes add one may need to up size if cord or cable is used. How many sizes you figure it needs to be?
This is a place the code and machine,,nema are marginal. A couple of the small welders allow for some pretty small wire and I am not sure what skin off their azz it would be to eliminate a whole lot of confusion and list a wire 1 size bigger.
No one ever burned a house down with a 10 cable on a buzzer and why not dump the 14 wire on the compact migs and list 12 like the machine cord and simply allow circuits to 50A? The 211 and others like it run great at 100 ft of 12 cable or cord.

 

[sberry]

The little brother the 140 comes 14 cord, the cord is actually heavy enough to run a 210 but not legal to hook to common welder circuit with a 50A breaker.

 

[alfredeneuman]

For example an AC 225 has a 12 cord and lists a 12 wire, single circuit in pipe and a 50.

The AC225 manual says a #10 or larger, in conduit, with a 50

 

[wyliesdiesels]

I understand NEC to allow a 50A outlet on a 30A circuit if it's a single outlet circuit ( 210.21(B)(1) ). The only restriction is the outlet is not to have a amp rating less than the circuit. There is no restriction to the outlet being a higher rating than the circuit. But, on circuits with two or more outlets you need to use the values listed in table 210.21(B)(3) which would limit a 50A outlet to a 40A or 50A circuit.

Youre right. Im not sure how i flipped that code around.

I went back and reread the section...