How do I properly connect 2 200amp breaker panels to a 320amp meter base?

Question

I am replacing all of the electrical in my house and am upgrading from a 200amp service to a 320amp service. We are in an unicorporated area of the county so there will not be an inspection but I still want to do things safely. Before I purchase thousands of dollars worth of equipment and wire I want to make sure that my plans are good. Any advice is much appriciated! Here is what I am planning.

There will be 2 200amp breaker panels in the house (one about 30ft from the meter base and another about 80ft). To safely power each panel, I would connect the two hots and neutral from the meterbase and run those a few feet through conduit to a 200amp disconect use 4/0 AL wire. Since each of the disconnect boxes are the first point of disconnect I would have the netrual and ground bonded in each of the boxes. From each of the disconnect boxes I plan to run 4/0-4/0-4/0-2/0 AL SER cable thorugh the attic (not in conduit) to each of my breaker panels. In the panels the netrual and ground would be disconnected.

One question I have is can I use the same two grounding rods to ground both of the disconnect panels or do I need two rods for each panel?

Answer 1

If EVs are the only reason for the service upgrade, don't. EVs don't need service upgrade because of energy management systems.

Now the first issue is that both of your service lines need to enter the house together at the same location, and have disconnects (optionally: main breakers) there. See 225.30 in NEC 2020.

It's perfectly fine to label these "Service Disconnect" and label the ones at the meter "Emergency Disconnect - Not A Service Disconnect". Then you won't need to run 4-wire between them and can do your master neutral-ground bonding here. The utility may still require neutral-ground bonding out at the meter.

NEC 310.15(B)(16) states clearly that 4/0 is only 180A wire. You would need 250 kcmil off a service that is larger than 200A, since 310.15(B)(7) does not apply.

Yes, disconnects at a given location can share ground rods.

It's valuable to think about future generator, PowerWall or V2X. In 2-panel 400A service, there is no easy way to feed those things to both panels. You would need a 3-pole 200A isolation switch or transfer switch on one of them (otherwise you create a dangerous neutral loop). Generally it's simpler to pick 1 panel and put all your critical loads on that.