If this is for compliance with 110.24, I would use the available fault current from the utility along with a simple calculation of the reduction from the service conductors to the service disconnect. There are a number of free online calculators that will do this.
Mike has a free available fault current calculator on his free stuff page.
HERE is a link, just click on the fault current calculator and download the excel spreadsheet.
Chris
I am always leary of accepting any free online calculator. I can't tell how they are doing the calculation. Here is an axample from the arc flash calculator listed on the same page as the one raider linked.
* NOTE: This is a demonstration tool only and is not meant to be used to calculate arc flash values for personnel protection.
My question would be: Are you using this calc to determing equipment specs?
mitch said:
... I have to design plans every now and then and now the City is requiring this calculation to be on all plans. ...
You used a majik word. So, some additional questions:
Does your state consider "design" as "engineering for hire"? If they do, are you considered the "the engineer of record"?
When you were designing plans before the city required available short circuit current, how did you select your equipment?
What don sugested is a good idea - but I sure would not use a free calculator.
ice