Short Circuit Calculations

[steve66]

If a calculation shows the available fault current is 9K for a line-ground fault, and 11K for a line-line fault, what rating does the breaker need? 10K or 12K?

Steve

 

[charlie]

11 kAIC or better.

 

[zog]

Add some more for wiggle room, if you add a motor later you will exceed your AIC if you are just above your initial S/C value.

 

[charlie]

Add some more for wiggle room, if you add a motor later you will exceed your AIC if you are just above your initial S/C value.

I agree that it is just good design to plan for the future but the NEC doesn't require any more than for what is being installed. With that said, I wholeheartedly agree with your comment!