You've an option: modern breakers have adjustable ratings. (Limited to specific models, of course.)
I'd simply call up SqD and talk to their tech. What would take you hours is something he'll know off the top of his head... and he's free to you.
Embedded 'free' technical assistance is why you pay so much for such breakers.
You also have the option of dropping in a fuse set -- cut in a safety switch -- and are you CERTAIN that it's 225 A that you need? Will you have to set a safety switch/ disconnecting means ANYWAY? Can this be downsized to the next lower frame size?
[ Disconnecting switch frame sizes: 30, 60, 100, 200, 400, 800, 1200... BTW, they do get huge. ]
[ Disconnecting switch voltage thresholds: 240 VAC, 600 VAC ]
If the conductors are already pulled, and sized for 350 A, then you don't need a new breaker at all. Just downsize your safety switch fusing. 225A fuses are the same frame size as 350 A fuses -- in the same class.
( J type fuses require that you fiddle with the safety switch fuse mount screws. That should take no more than a few minutes to complete. )
Again, stay out of the engineering profession if at all possible. There's no upside -- it's all downside.
You don't ever get paid for your efforts -- but will entirely take the heat if you're wrong in any way.
Last edited by Tesla; 07/22/12 01:46 PM.