Thanx. i just want to use the right conductor and i was throwing the ? out there because at Lowes they have the 2-2-2-4 AL listed as a 100A conductor.
No, #2 aluminum conductors is not big enough for a 100 Amp panel. :no: You will need to install #1 Aluminum for 100 Amps.
Now, if you are really bent on using that #2, then you could feed it from a 90 Amp breaker in your house, and that would be sufficient. You could still use a 100 Amp main breaker panel in the garage, as long as it was fed from a 90 Amp breaker in the house.
Of course, as long as your calculated load is 90 Amps or less. :whistling2:
As I recall, NEC also says if you can't match ampacity to breaker, then use the "next recognizable size breaker" (which assumes 5-10 amps difference), or words to that effect, which, in this case would be a 100 amp. So if the supplier of the panel you are using makes a 90 amp, then you can use that, if the manf. doesn't, you can either upsize the wire, which is a cost issue, or use a 100 amp breaker, both of which should pass inspection.
And unless you are doing something in your "garage" using monster motors or ??? that draw huge constant load current, then I don't see an issue. Even at 50 amps constant load (12KW or about 16 HP worth of motors), with 70-80 amp burst load, with a 100 foot run, you are going have less than a 2% voltage drop, which IMHO is a good cost/value relationship.