It is generally accepted that a 50 amp welder outlet can be supplied by whatever you choose. [/quote]
This should not be accepted. You are right to feel bad about an outlet rated more than the cable ampacity.
Article 210.21(B)(1)exception no 2 is very clear.
You select your ampacity requirements from article 630.11(A) for arc welders and use this for your receptacle. The breaker can be up to 200% of the I/eff. This way the breaker does not false trip.
The only time you see a bigger receptacle is if your cable ampacity is 40 amps. They don't make a 40amp outlet so you go up to a 50amp outlet.
If the I/eff is 27amps for a single arc welder the smallest wire would be 10awg. The receptacle can not be larger than a 30amp receptacle as per the table 210.21(B)(3)
Note: instead of using the circuit rating i.e. breaker size you use the cable ampacity as calculated using Ieff.
Of course you could run a larger cable than is required.
I have made a confusing mess!
Bottom line, if a piece of 12/2 or 10/2 was feeding a 50amp plug i would fail it.
I have a problem with my set up.
I have 6/2 with a 50amp circuit but miller recommends no more than 35amp time delay breaker.
The manufacturer gets to dictate whatever they have ul listed. So i should step my breaker size down for my dynasty 210dx.
Cheers
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