I pulled 250-250-250-2/0-4 xhhw into 2" last spring. That wasn't real fun and I wouldn't recommend it but it's what got roughed in and it's kind of hard to change after the concrete gets poured.
With single phase you'll have one less wire. Also 2 1/2 is substantially larger than 2". Either 4/0 or 250 will fit fine
With single phase you'll have one less wire. Also 2 1/2 is substantially larger than 2". Either 4/0 or 250 will fit fine