National Electrical Code Section 110.9 Interrupting Ratings states: Equipment intended to interrupt current at fault levels shall have an interrupting rating at nominal circuit voltage at least equal to the current that is available at the line terminals of the equipment.
Equipment intended to interrupt current at other than fault levels shall have an interrupting rating at nominal circuit voltage at least equal to the current that must be interrupted.
How would one know whether this requirement has been met? By conducing a short circuit study to predict the available fault current at each piece of equipment. This course takes you through the process of performing a short circuit study including the necessary data, study process and detailed short circuit calculations using Jim Phillips’ calculations worksheets which are part of this online course.