ECN Forum Forums Code Related Discussion NEC & other Code issues 400 A service entrance neutral wire size?

400 A single phase 240 volt service, outside building run in 3" PVC with weatherhead.

400 A copper from 2008 Table 310.16 calls for 500 MCM THHN, but what about the size of the neutral? I've been told I can use 250 MCM, but can't seem to find a code reference.

Anybody?

Thanks!

Grov