Question about temporary electrical job boxes

You have 30A 120V outlets? The only time I've ever seen those are for plugging in RVs.

If you have a 30A circuit of the correct voltage, you can run a welder that requires 50A, you just can't use full output.

Many thanks for that information. Your last sentence, " you just can't use full output" does that mean the welder will not work at full capacity? I can't picture that in my head why it works that way. Can you explain it to me in a different way.....Peter

The electric welders I've used have adjustable welding amperage which is set depending on the material being welded, rod type/wire feed rate, etc. If the welder draws 50A from the line to put 150A into the weld, and you only have

30A available from the line, you won't be able to go up to 150A on the output, instead you'll top out at say 100A. These numbers I just pulled out of thin air, but it illustrates the point. A lower capacity circuit will limit the thickness of the material you can weld because there's simply less power (wattage) available before the breaker trips.

I got it this time. Here is one more example to see if I really got it. I have a 110 v mig welder, I seem to remember that it can go 70 or 90 AMP's. Does that mean I will not be able to weld on any of my outlets, because they only go as high as 30 or 50 AMPS?. Here comes the other dumb one. What I don't understand. If I have a wall outlet let's say that is protected by a

30 AMP fuse, how will a 50 AMP spider box protect me up to 50 AMP's that I don't get into my head either. English is not my native language, so I may really really sound stupid, but you are so nice to explain it to me.....Peter

The welder contains a transformer which converts voltage to amperage, for example if it draws 15A at 120V, that's 1800W of available power, which is converted to a much lower voltage, perhaps 20V across the arc which if you assume for simplicity 100% efficiency, that's 90A arc current at the output. Same 1800 Watts, but you've traded voltage for amperage. In reality, efficiency will be lower, 80% is a reasonable assumption, some of your power will be burned up as heat in the welder.

I'm not familiar with the term spider box, but a 50A box won't offer any additional protection. Your current is limited by the weakest link, which in this case is the 30A breaker upstream. Draw more than 30A, and that breaker will trip, doesn't matter if you have something down the line capable of carrying 50A.

Thanks again, it seems so simple now, when I read it, even though the answer partially entered my mind, but I wasn't sure, now I am. I appreciate you a lot for helping me......Peter