Main Bonding Jumper
- Proper bonding - bond only at main panel, not subpanel. . This is because the breakers are activated by current that includes the neutral, and if current flows through ground, the neutral may not have the current to trip a breaker. Depends on internals of the breakers. You still want the equipment ground connected to ground wires at subpanels, though..
- The MBJ - . Must be at main panel. Not subpanels.
- Note that the Leviton PoN CSED is factory-bonded.  Thus, can't be used as a subpanel.