I have a subpanel that was installed probably back in the 80s. It has a ground wire running to a local ground rod, not back to the main panel. The ground bar in the panel is not bonded to the common (white) bar, it's just connected directly to the box and then the ground bar has a heavy gauge wire running to the grounding rod outside.
Should the common and the ground be bonded? Or is this correct, that the common goes back to the main panel, and the ground goes to the local ground? If they should be bonded, does the bonding screw bond the box to the common?