You always chose an AIC rating that is higher than your available fault current at the line side of the breaker. This means you must be able to perform short circuit current (fault) calculations.
Originally Posted by john37
In most situations the available bolted fault current at the service entrance is provided by the utility (they often provide their 'design' value). You must then determine the impedance of the circuit from one panelboard to the next. Use the circuit impedance and the beginning fault current to determine the fault current at the downstream panelboard. Unless you are very experienced, it is not worth trying to consider the current liming effect of any items except the conductors (as Augie pointed out series combinations of devices are not easy to determine).
Just because you can, doesn't mean you should.