Need to update main line through house.

[ytupnorth]

I have a new combo meter box and 200A main shut off installed outside professionally. It has 4/0 service line coming into it and I have confirmation from the electric company that I am good for 200A service supplied to the house. Previously, there had been no main shut off. The new meterbox/panel is bonded and the line from that through the attic of the house is only 2/0 2/0 1AWG SEU aluminum flat cable sheathed in gray. This original line is inadequate for 200A service and I want to change it out to the proper size and run it to a brand new bigger (now sub)panel to replace what used to be the main panel in the garage, now inadequate in size. The old one is still bonded and neutrals and grounds are mixed. There are 2 ground lines that run from the bonded bus in the old panel in the garage to both a ground rod outside and the water lines.
My question is this: what kind / size line do I buy and use to replace the one currently running from the (now)main panel outside, through the house to the new sub panel in the garage? I believe Ill need a 4/0 4/0 2/0 aluminum. The two 4/0 as the conductors and the 2/0 running from the bonded bus in the meter/main shut off panel outside to the separate neutral bus in the new sub panel in the garage. Then the ground lines from the separate ground bar in the new sub panel in the garage to the ground bar and water lines.
Can anyone tell me if I am correct? And if so, once the new line is inside the attic of the house, does it need to be in conduit?
I thank you for any input.

 

[Megawatt]

I have a new combo meter box and 200A main shut off installed outside professionally. It has 4/0 service line coming into it and I have confirmation from the electric company that I am good for 200A service supplied to the house. Previously, there had been no main shut off. The new meterbox/panel is bonded and the line from that through the attic of the house is only 2/0 2/0 1AWG SEU aluminum flat cable sheathed in gray. This original line is inadequate for 200A service and I want to change it out to the proper size and run it to a brand new bigger (now sub)panel to replace what used to be the main panel in the garage, now inadequate in size. The old one is still bonded and neutrals and grounds are mixed. There are 2 ground lines that run from the bonded bus in the old panel in the garage to both a ground rod outside and the water lines.
My question is this: what kind / size line do I buy and use to replace the one currently running from the (now)main panel outside, through the house to the new sub panel in the garage? I believe Ill need a 4/0 4/0 2/0 aluminum. The two 4/0 as the conductors and the 2/0 running from the bonded bus in the meter/main shut off panel outside to the separate neutral bus in the new sub panel in the garage. Then the ground lines from the separate ground bar in the new sub panel in the garage to the ground bar and water lines.
Can anyone tell me if I am correct? And if so, once the new line is inside the attic of the house, does it need to be in conduit?
I thank you for any input.

I have a new combo meter box and 200A main shut off installed outside professionally. It has 4/0 service line coming into it and I have confirmation from the electric company that I am good for 200A service supplied to the house. Previously, there had been no main shut off. The new meterbox/panel is bonded and the line from that through the attic of the house is only 2/0 2/0 1AWG SEU aluminum flat cable sheathed in gray. This original line is inadequate for 200A service and I want to change it out to the proper size and run it to a brand new bigger (now sub)panel to replace what used to be the main panel in the garage, now inadequate in size. The old one is still bonded and neutrals and grounds are mixed. There are 2 ground lines that run from the bonded bus in the old panel in the garage to both a ground rod outside and the water lines.
My question is this: what kind / size line do I buy and use to replace the one currently running from the (now)main panel outside, through the house to the new sub panel in the garage? I believe Ill need a 4/0 4/0 2/0 aluminum. The two 4/0 as the conductors and the 2/0 running from the bonded bus in the meter/main shut off panel outside to the separate neutral bus in the new sub panel in the garage. Then the ground lines from the separate ground bar in the new sub panel in the garage to the ground bar and water lines.
Can anyone tell me if I am correct? And if so, once the new line is inside the attic of the house, does it need to be in conduit?
I thank you for any input.

as far as the wire size for your new sub panel you will need the same size wire as your 200 amp main panel. The sub panel that you are wanting to upgrade is fine but the ground rods have to go and the neutrals and grounds need to be separated which means you will probably have to install a ground bar in your new panel for the grounds. If your water line is bonded by the sub panel then you have to take it loose and bond it to your new main panel