400amp main pannel w/ 2x200amp circuits. What size/type of wire is required to run 200amps from main panel to another sub panel ~100ft away

Question

This is the scenario:

1. I have 400amp main service to my meter.
2. I have a 400amp main panel that has 2x200amp circuits. The panel is grounded with bare copper wire 6ft apart with appropriate gauge wire (this was installed by an electrician and permitted).
3. 1x200amp circuit is used as the main electrical supply for my house.
4. I want to use the remaining 200amp circuit to supply a 200amp exterior panel that is about ~100ft away on a barn.

Questions:

1. What type of wire should I use for this ~100ft run? Can it be 4/0 Aluminum?
2. Can I use 3 appropriately gauged aluminum service wire to connect 2 of the aluminum wire to the 200amp circuit on the main house panel and the 3rd aluminum wire to the ground bus on the 400amp panel? Basically, can aluminum wire be used as ground wire to run from one ground bus to another?
3. At the panel on the barn, do I need to "re-ground" the panel if the aluminum wire is connected to the main panel ground bus?
4. I would plan for an 160amp draw (80% load of 200amp) at the entrance panel on the barn, is this the correct assumption?

Answer 1

What type of wire should I use for this ~100ft run?

250 kcmil aluminum per NEC 310.15(B)(16).

There are no wins to be found in 310.15(B)(7) since that applies only to the whole service size (400A).

Can I use 3 appropriately gauged aluminum service wire to connect 2 of the aluminum wire to the 200amp circuit on the main house panel and the 3rd aluminum wire to the ground bus on the 400amp panel? Basically, can aluminum wire be used as ground wire to run from one ground bus to another?

If you want to power any 120V loads out of that panel, you are going to need a neutral. Neutral is not ground.

Neutral is generally the size of the hot conductors. Ground can be I believe #4Al.

At the panel on the barn, do I need to "re-ground" the panel if the aluminum wire is connected to the main panel ground bus?

Do you mean local ground rods? Yes, that too. You need all 3 things since they do 3 different jobs.

• Neutral - return service current
• Ground wire - return human generated fault current
• Ground rod - return natural current, spikes, lightning, and prevent hazardous voltage gradients from making a difference between grounding system voltage and actual earth voltage.

I would plan for an 160amp draw (80% load of 200amp) at the entrance panel on the barn, is this the correct assumption?

Yes.

But no need to limit yourself to two F150 Lightnings :) you can have up to sixteen EVs as long as the wall charge units are using Share2 technology to coordinate with each other to not exceed 160A amongst them.