Quote Originally Posted by kenwhite View Post
Well, if the welder is connected to a dedicated circuit, i.e. nothing else will ever be connected to it, then the branch can be sized with lower rated current carrying components than the welder actually draws. If the branch circuit has the possibility of having a higher current draw, non duty cycle load connected to it, then it will trip the breaker relatively soon which is why a larger sized branch is needed for multiple load branches.

It is possible to operate low duty cycle devices on lower current rated branches because circuit breakers, and fuses, are thermal devices that trip, or open, when over heated over a specified time period. Since low duty cycle devices draw power and create heat for a small finite period of time that is typically much less than 10 minutes over a defined 10 minute duty cycle period, the thermal devices will heat for a short period of time and then cool for a longer period of time and therefore not trip.

This is why Griz can use a lower rated current branch and not have excessive breaker tripping -> plus the welder/plasma cutter only draws maximum current when operating at their maximum thickness limits.
Thanks Ken you firmed up my understanding and dispelled a few misconceptions for me. This thread is taking on an interesting new character.