Re: Circuit breaker AIC ratings
To: mgnh, I would recommend that you contact the Cooper Bussman Company to get their book on "SPD Selecting Protective Devices, Based on The 2002 NEC. Their phone number is 636-394-2877. They will send one to you free of charge. If you were close by I have several in my possession.
This book will explain all that you would ever want to know about AIC, and Selective Fuse Co-ordination.
Now to answer your question, "What does AIC mean?"
If you took a bar and shorted out the secondary of the transformer that feeds your facility, that would be determined to be the Available Fault Current. Suppose that this current would be 50,000 amperes. Any fuse down stream of that fault would have to have an interrupting rating of at least 50,000 amperes.
Today, if you would look on the barrel of the fuse, you would find a rating saying 200ka or 300ka. Meaning 200,000 or 300,000 amperes.
Now, as you go further downstream from the 50,000 amp fault, the fault current will decrease because of the resistance of the wiring in the circuit. For example, generally at a lighting panel, the circuit breakers are in the range of 5000 AIC or 10,000 AIC.
But bottom-line, get the book that I suggested, and it will answer all of your questions.