How small can my service neutral be when most of the load is 240v?

Non-residential 120/240 single phase service. 320amp meter to (2) 200 amp panels. The distance from the meter on a pole to service panels are 50ft. I'm running 3/0 copper for the phase conductors. #6 for the grounds.

First panel will have 160 amp continuous load. Everything connected will be 240v. The second panel will have 40 amps of 120v and 120 amps of 240v.

Even though there is no 120v equipment on the first panel, I can't go lower than the GEC, right? #6?

can't go lower than the GEC

tkeoki said:

...Even though there is no 120v equipment on the first panel, I can't go lower than the GEC, right? #6?

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Or no neutral. There's no code forcing you to bring a neutral to a box. But, then you could never use that box for a 120v load.

I thought 3/0 copper service required #4 GEC. I'm probably reading the wrong table again, though...

bluebinky said:

I thought 3/0 copper service required #4 GEC. I'm probably reading the wrong table again, though...

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You are correct about a #4