A 200A primary c/b and a 400A secondary c/b is Code compliant.
David is correct - Obvious brain failure on my part. I don't know what I was thinking.
QUOTE="iceworm, post: 2554219, member: 114227"
Revised
Primary CB
Primary is 135A
2.5 x 135 = 338A
200A CB is okay
Secondary CB
FLA is 312A
1.25 x 312 = 390A
400A CB is okay
The transformer will have to be overloaded to 128% to get 400A. and it will get pretty hot.
400A on a 400A CB is inviting a trip, but it could take a few hours, however, it also might never trip.
Just need to make sure the conductors are suitable - ampacity is equal to the CB, or more
Yes, it may well smell hot. And it will burn if you touch it.
The life will be reduced - I don't know how much.
But it will work - possibly for several years.