50 Amp Vs 30 Amp for 220 v Tig Welder

Did you specify the type of welder you planned on using and the specs. I don't know how they even know to install a 30 amp circuit if you did not give them any specs on what you wanted to use.

Me I would request specs on everything you plan to run before even quoting the project. There are many different sizes of all types of equipment used in a garage.

J-Madd said:

I just had a new building constructed where the electricians knew that I would need 220v receptacles for welders and electric over hydraulic vehicle lifts. The wiring is complete, but they used 30 amp breakers as well as wire that was not rated for 50 amps, so they've got to replace all wiring and breakers to make them 50 amp circuits.

So my question is: Should it be common knowledge by an electrician that these devices need 50 amp circuits? I'm afraid they're gonna try to stick me with the cost for their mess up.

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How do you know they require 50A circuits? Why didn't you tell the electrician that information? There's no way to guess it. If changes are required, it's on you. It seems odd that car lifts would require 50A circuits though. They are relatively low-power devices. I would have expected that a 20A 240V circuit would be adequate. Since they are motor loads, you only need to size the wire to the motor's horsepower rating, and the breaker can be up to 250% larger. So unless the operating current (as shown in the NEC horsepower tables, not on the motor) exceeds 30A, the #10 wire is fine and you could use a 50A breaker.

Some welders are fine on a 30A circuit, while others require 50A or even more - there's simply no way to tell without looking at the welder. The NEC also allows duty cycle rating of welder circuits, so that smaller wire can be used. If your welders actually require 50A breakers, you can probably keep the existing #10 wire and use a 50A breaker legally.

Thanks for the info. I guess that answered my question. They didn't request any specific information about what type of welder; nor did I know to supply any additional information. It never occurred to me that it would need any other breaker than what they would automatically install. The 220 v receptacles at my previous shop (that I bought already constructed) all have 50 amp breakers.

But why do you think you need 50A circuits? What are the actual ratings on the equipment?

You are both negligent. They never should have done work without knowing what you wanted, and you should not have assumed they would somehow guess correctly.

The best you could hope for is that they might give you a break on the rework, but if push came to shove, you would lose. They can rightfully claim that you wanted them to use their best judgement, and they did.

mpoulton said:

But why do you think you need 50A circuits? What are the actual ratings on the equipment?

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That is a good question. I will try to find that out. The bank and I are funding this construction (my first) and it's a learning experience. I am building this business for my brother who's been out of work for a year. The "other" shop I spoke of was for hobby, not a job. My brother has been the in between for all of the contractors, as I have another business to run.

Toller said:

You are both negligent. They never should have done work without knowing what you wanted, and you should not have assumed they would somehow guess correctly.

The best you could hope for is that they might give you a break on the rework, but if push came to shove, you would lose. They can rightfully claim that you wanted them to use their best judgement, and they did.

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I now agree 100 %.

A lot of welders need 50 amps, but certainly not all. Many only need 30. I even have a little inverter tig welder that runs on a 110v 20a circuit.
Like others have said you need to specify (and they should have asked).

I have never in my life met an electrical contractor that would install anything without knowing what the requirements were. What they were before I even started the job. How could he bid this job without knowing?
You use the term "Common knowledge".
There is nothing common about several 230 volt receptacles in a work shop.

What does the contract say? What did it specify? No contract? What did you tell the EC you wanted?

Tigs rarely use more than a 30 amp circuit.... MIGS are another story.