Aic and short circuit ratings

[mitch cochrell]

I am kind of confused on which number to use from the poco to determine the aic rating for the ocp and the panel board of a service we are about to install. The poco has two options to choose from. One is the "ultimate fault current" and the other is "short circuit current". If I am using Mike Holts fault calculator which number would I enter in the utility available fault current box.

 

[skeshesh]

I think you would use the available fault current. I'm unsure of what the term "ultimate fault current" refers though... here's an old thread where it's been referenced - check out the comments towards the end by Charlie: http://forums.mikeholt.com/archive/index.php/t-93441.html

 

[mitch cochrell]

Thank you sir

 

[jim dungar]

They provide two different values because they serve two different purposes.

Most every utility i deal with says to use the 'ultimate' fault current for selecting equipment, and the available current as one possible value when determining arc flash incident energy.