I need to replace a 350 amp I-line with a 225 but in searching online with the vast number of breakers out there and different price how do you which is what you need. All I can find is type LA and current rating no catalog # on it. It is for a new roof top unit.
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.
I did have the chose of cutting in a dis but that would have required putting in a 400 dis and it would have had to be a nema 3r and the existing wire was 250 mcm which wasn't correct to start with. So I don't know if something had changed since original wiring, but I would like to walk away know I did something correct.