The utility should be able to provide that information for the service entrance location. Needed transfomer impedance data to estimate that value is not generally available to the electrician working downstream of the meter.
Also, that relieves the electrician of having to do short-circuit estimates for service-entrance equipment.
Determine the full load current on the secondary, divide that number by the percent impedance of the transformer, and that gives you a conservative value at the secondary stabs of the xfmr. Depending on the length of the secondary conductors, that will further reduce the available fault current. For example, 150000/480/1.73/.02=9030A of fault current at the secondary stabs. You would be safe choosing the lowest AIC of the group.
Re: Selecting AIC#128913 03/24/0409:34 AM03/24/0409:34 AM
Warning - the Square D NF panelboard is not rated for use on 480V delta systems. The NF panel has a slash rating of 480Y/277, so it can not be used on circuits with more than 277V to ground. You need to switch to their I-Line panel instead.
Re: Selecting AIC#128914 03/28/0408:45 AM03/28/0408:45 AM