I presently have an outbuilding subpanel connected to a main service panel with #10 copper 2+G backfeeding a 30A breaker, w branch circuits - the G wire serves as neutral. The sub panel neutral buss is tied to a ground rod because there is no other metalic connector between the two buildings. This has worked well so far. Now I want to run a 100 Amp #2 aluminium wire to a new subpanel in the same outbuilding, from the same service panel. The aluminum wie is direct burial, 2-2-4, no ground. Here are my questions. Assuming the main service panel is properly grounded to two ground rods with #6 copper:
1) should I disconnect the present 30 Amp service and rewire the existing subpanel to a 30 Amp breaker in the New Panel?
2) should I connect the new panel to the existing ground rods on the existing 30 Amp subpanel , or would it be better to use the #10 wire to run the ground back to the main service panel?
3) presently the neutral and ground wires in the main service panel are on the same buss, this is also true in the existing 30 subpanel in the outbuilding. Should the subpanel neutrals and grounds be on separate busses or tied together?