Let's be clear on one thing. I never said I run the minimum size wire required for a welder. In fact I've ran fullsized circuits every single time. What I don't agree with is telling someone they have to run fullsize circuits when we all know that is not the case most of the time. Now your mixing fact with opinion.
As for electricians only giving the bare minimum, you have no idea how I wire. Did you ever consider some folks might not want to pay for more than the bare minimum?
If a customer wants a welder recep but doesn't want to pay for anymore wire than he has too, he wants the bare minimum sized for his welder only. The code allows it, the customer isn't willing to pay for anymore than necessary, do you think I'm going to turn down installing a welder recep just because I think he would be better served with a fullsize circuit?
Fortunately, this hasn't been an issue yet as most of my welder installs have been commercial, industrial, and ag. They're willing to pay for larger wire and there are no guarantees on what they may plug in, in the future.
These hypothetical customers you reference who are willing to only pay for the bare minimum would not be not very smart. Would you explain to them that the increased wire cost to make a more flexible future design is negligible compared to the labor costs? Would they understand that they are stepping over dollars to pick up pennies. I have never met a homeowner that would cheap out on a wire, when the cost increase was rather insignificant compared to the labor. How about you?
This reminds me a buying cheap paint. Only a stupid *** buys cheap paint to save 100 bucks on a job that is 90 percent labor and the cheap paint will have to be redone quicker costing even more labor.
I would assume a continuous load and not even for one second think about the special low duty cycle welder section. It may make sense for commercial, (I doubt commercial would ever go bare minimum either) but not for residential where people see a 240 circuit and want to plug other things in and where people upgrade their welders.
This application calls for a 50 amp circuit. I would run the 8 individual wires in conduit or 6 romex. Total cost for materials about $30 including the breaker. If the poster insists on using what he has (the 8 romex rated at 40 amps continuous) then he should stick with a 40 amp breaker. It will undoubtedly be fine.
I stand by my comments. Electricians routinely undersize circuits, conductors, boxes, and conduit, to save nickles at the expense of future flexibility and headache. There is no reason for it. If you don't do these things, and I obviously have no way of knowing whether you do or you don't or whether you flat rate jobs or whether you treat every job as if it were your own, then you are to be commended and you are also - rare. For all I know you may square cut all your PVC with a miter saw, use a calibrated torque wrench on service entrance and main panel lugs, a torque screwdriver on every other connection, make sure you don't nick any wires when stipping insulation or insulation when stripping jackets, make sure all your screws go 3/4 around every device, calculate box fill and conduit fill on every occassion, drill your holes dead center and the proper size, never use shared neutrals, or if you do put them on a double pole breaker, make sure all your boxes are flush with the finish surface, make sure every box is properly grounded and not relying on conduit, make sure excess bare wire is not exposed with every connection, pretwist your solids and cut off the end where you have damaged the conductor with your pliers, etc.
The NEC is a bare minimum below which is not safe. It should not be the beginning and end of the calculation.
I mix fact with opinion everyday. In fact, most of what you think is fact is really opinion at its core.
