The breaker is only for short circuit protection of the feeder, NOT overload protection.

Arc welders provide their own overload protection.

The wire size is not as directly connected to eh circuit breaker rating as with general use receptacles.

And those who wire receptacles in residences according to Art. 630 (and some of 430) are complete fools IMO.
This is NOT like an A/C unit that is hard wired.

You are NOT wiring a welder. You are wiring a receptacle circuit. At this point in time it just so happens that a welder is what is being plugged in to that receptacle.

What happens when the new homeowner gets all excited when she finds the perfect 50A receptacle already installed so she can plug her kiln in? You know, a kiln that runs at max watts for hours upon hours.

I am seriously considering writing to the NEC CMP to propose a change that disallows the use of Art. 630 in residential dwellings.

How does this work in a commercial/industrial setting? Does the circuit need to be labeled? I can imagine opening a small welding shop and installing a circuit per Article 630. Because my business is wildly successfully I quickly outgrow the space and move on. What happens to the next guy who has a kiln, table saw, etc. and sees a convenient receptacle?

Thanks to you all for you thought / ideas / suggestions / concerns . . . .

Bob

Thanks again to all . ..

Bob

As suggested, run full-size conductors. What gauge you need depends on what kind of wire or cable you plan on using.

Of the "many qualifiers" you refer to, I see "and anticipating no present or future other use for the circuit," as pretty much the only one. HOW in the world can you predict or ensure this???

You cannot protect fools from their own errors.

The article is there and has no restrictions on commercial or residential use.

I have numerous large 240 V power tools, and even a couple of 3-phase tools.
They are all wired to the correct code articles.

If a subsequent fool tries to use them for an inappropriate use that is NOT my problem.

"The article is there and has no restrictions on commercial or residential use.

IMO there SHOULD be!

If a subsequent fool tries to use them for an inappropriate use that is NOT my problem. "

All well and good. But what if the fool has NO idea that the circuit is wired for a welder according to Art.630 of the NEC??? Then what you have is an unsafe installation, simply by changing occupants.

I can see if the receptacle is labeled for welder use only (although not required) and someone uses it for something like a kiln. That is their foolish problem.

If another person wants to install and use heavy equipment it is incumbent on THEM o make sure the installation is correct.

Special use circuits should be identified i the panel with their purpose as part of routine labeling, but restricting the use of dedicated circuits is not going to be very productive.
They are allowed and should be used when needed.

Every hermetic compressor for HVAC gets special permission also.
The motor is cooled by the returning gas and contains overload protection.

What if the next owner wants a larger condenser?

Do you honestly thing someone who needs a 50A circuit in a garage for a kiln (for instance) is going to open a box, or check the wire size, to make sure it is not on old welder circuit legally wired to Art.630 yet not sufficient for most any other use of a circuit that size???
I am all for not idiot proofing things, but your suggestion that someone would or should know something like this is absurd IMO. All they will see is a 50A receptacle on the wall and a 50A breaker in the panel. And IMO it would be a fair assumption that the circuit was properly wired, and NOT just for a welder.

Special use circuits should be identified i the panel with their purpose as part of routine labeling, but restricting the use of dedicated circuits is not going to be very productive.

I don't get what you are saying. The ONLY way to assure safe and compliant use of such a circuit would be to restrict it to a welder. A label would help, but it is not required and not permanent.

What if the next owner wants a larger condenser?
Apples and oranges. They cannot simply plug in an A/C condenser.
99.999% of the time something like this would be professionally installed, assuring a proper installation.

Why are you so convinced this is YOUR problem?

It is THERE problem.

I have no compunction about wiring what I need to the code.
It is NOT incumbent on me to guard latter fools who do not know what they are doing.

Any responsibility ends when you do the work to code as the present owner requests.

I have installed kiln circuits a number of times, and between the kiln manufacturers and the potters using them there is a great sensitivity to what it takes to run a kiln in a residence.

They tend to be far more paranoid than ANY code requires.
They are sleeping upstairs with a kiln in the basement at many thousand of degrees F that requires a 24-48 hours at temperature for the material, and in many cases multiples of that for cooling off before you dare open the kiln (the quick cooling would cause all the pottery to instantly shatter, so no peeking).

Three-five-seven day kiln cycles are not at all uncommon.

Some things I do according to code minimums, many I do not. This is one I do not.

Some things I do according to code minimums, many I do not. This is one I do not. "

Correctly wired special use circuits are pretty far from mimimum.

Do you oversize the branch circuits for HVAC work in case somone later needs a bigger unit?

You could make thins even safer by using #10 for ALL 20 amp circuits, and #12 for 15 amp circuits.

I have actually never met anyone stupid enough top just plag a kiln, large compressor, welder, or other large equipment into any handy spot.

The equipment contains all sorts of warnings and installation instructions.

My 3 hp table saw requires a 45 amp breaker for reliable repeated starts.
There is no reason to use wire larger than #10 since the motor cannot overload the circuit and the starting surge is what is driving the breaker larger (NOT the running load).

Plug something like a kiln into a "handy spot"??? Come on, it's not like there are 30 or 50A receptacles all over the place.

Sorry brick, I like you a lot, but I can tell we are not going to see eye-to-eye on this one.

Sound like a good, safe compromise that doesn't really violate anything ?

Thanks again for your suggestion(s) / ideas / concerns.

Bob

Yes.

Without knowing what they are designed to supply (and more than one 30 amp receptacle on a circuit is a BAD sign) you cannot just use them for a kiln, or any other load.

"I rest my case."

What is so darn hard about checking the circuit?

What's the duty cycle of the welder?

Not necessarily.

Breaker rating and things like wire size and device rating are not related on special use circuits in the same way as on general use circuits.

If the receptacle is also being used as a final disconnect (instead of an actual switch, allowed in some cases) it may need a larger rating than the operating rating.

Thanks, In fact, there are two inside and one outside. The outside one was probably for RV or boat use. I understand about more than one on a circuit being a bad design. I have to confess that I have not checked them out yet. I would say it is likely that they are on separate circuits due to the location of the panel (100 amp) and the outlets. (There is no economy to running them in a string.) Since I recently found some 240V open splices where baseboard heaters were removed, I guess I can't take anything for granted. The sad thing is that the former owner was an electrician.

Not at all unexpected. The best auto body repairman in town often drives a car covered in primer. And many a good carpenter lives in a half finished house.