I would like to add a subpanel in my detached garage and be able to run 240v also. Can I pop in a 40 A breaker using #8 AWG to maybe a 70A subpanel in the garage. I want to put another 40 A breaker to run 240V to a receptacle and a 15A breaker for my lights and a couple receptacles. Do I have to use a ground rod for that subpanel and if I do, do I bond the neutral bus and ground bus? Or can I run the ground back to the main panel?