Whenever system changes occur in a premise or changes by the utility that might increase the available fault currents, the existing OCPDs must be reevaluated to determine whether they have a sufficient interrupting rating.

• A. True
• B. False
• C. Only for new installations
• D. Never

Answer: (A)

Whenever system conditions change in a building or the utility alters supply that could raise available fault currents, you must reassess the protective devices to ensure they can still interrupt the fault. The interrupting rating is the maximum fault current the OCPD can safely interrupt without being damaged. If a change increases fault current and the OCPD’s interrupting rating isn’t high enough, the device could fail to trip or could be damaged, creating the risk of fire, arcing, or other hazards. So, re-evaluating existing OCPDs in light of new fault currents is necessary, not just for new installations. The statement is true.