Need Help: 240v in Garage?

12/2 wire I think is what i used for my compressor. A 5 hp 220v is going to need a 30a circuit. My IR compressor recommended to wire in a junction box box without a plug. It's pretty straight forward and plenty of wiring diagrams on the net to do a simple circuit like that. Welders tend to do better on a separate circuit also.

*edit, it is 10g