[avi8torny]

You're going to have to run another service out to the garage if you need 80amps just for the GTAW. Just consider what other circuits you will need out there and your now your around 100 amps just satisfy the power requirements in the garage.

Let's say you have a 100 amp service in your basement fed by the meter. You cannot just add another 100 amp service off the existing box. You have to upgrade the wiring from the meter to a new box, presumably to a new 200 amp box. Then you can run an 80amp circuit from the new service box to your machine. You are responsible for the wiring upgrade from the meter to the new box, not the power company.

Hope that helps a little.