Steve,
I don't want to say that it's impossible for there to be conditions that could possibly put 5000A into a #14 cable, but even if you hooked that #14 cable to an ideal 120V 0-impedance source, if the romex exceeded 4', resistance in that cable is too high to allow current levels to reach 5000'.
My numbers say that 8' (4' of NM) of 14 will permit 4777 amps to flow if the system can supply it. Yes that is less than 5000 amps, but the 1/2 cycle damage point for #14 is 2384 amps.
In reality, transformer and feeder impedance drop current levels WELL below that point.
So there is never a need for a small breaker with an AIC greater than 5,000 amps?
Don
[This message has been edited by resqcapt19 (edited 11-03-2006).]
