Chris, your service right now is set up as single-phase 110V. You'll need to pull a two-phase 220V service cable from your main box to this box. Hopefully, your main service can support this load. It not, you'll need to upgrade your main service box, too. You'll need a 220V breaker for your welder. You'll need a grounding block (see Thom's pic, upper right hand side). Your 110V service ties the neutral (white) wires and grounds together, but that will change with the 220V service. You'll split some of the original 110V loads onto one phase of the 220V service (e.g., black to white, plus a ground), and rest on the other phase (red to white, plus the ground). It's been quite a few years since I mucked with these things, so use my comments with a grain of salt.
Wow, you guys are fast typists!
