fault current calculation

[vincedigital]

if i have a
utility transformer to utility electrical meter to service rated disconnect switch to main electrical panel to subpanel
where are the points where i calculate for the fault current?
is it from utility transformer to service rated transfer switch (1st point) then service rated transfer switch to the main panel (2nd point) or
utility transformer to main panel (1st point) to main panel to subpanel (2nd point)
thanks,

 

[jim dungar]

Each piece of equipment needs to be applied per its short circuit current rating, so you need to calculate at each point.

 

[don_resqcapt19]

Typically you would get the available fault current at the transformer terminals from the utility and then calculate the other points from there.