Which statement is incorrect?

Which statement is incorrect?

• A. After installation, there is no need to be concerned with an OCPD until the device opens.
• B. OCPDs should be reevaluated whenever system changes occur that might increase available fault currents.
• C. OCPDs must be reevaluated to determine whether they have a sufficient interrupting rating.
• D. Changes in utility fault currents require reevaluation of OCPDs.

Answer: (A)

The key idea here is that overcurrent protection devices (OCPDs) must be chosen and periodically re-verified to handle the actual fault currents the system could experience, not just rely on them to trip when a fault happens. Available fault current can change with wiring changes, added equipment, or upstream utility changes, so the protection must be checked regularly to ensure the device’s interrupting rating is still adequate. The statement about after installation there being no need to be concerned until the device opens is not correct. Protective devices must be sized and evaluated for the maximum fault current that could occur at their location. If the available fault current increases beyond the OCPD’s interrupting rating, it may fail to interrupt safely, or equipment could be damaged. That’s why reevaluation is needed whenever system changes occur or utility fault currents change. The other statements reflect proper practice: reevaluating OCPDs after changes that could raise fault currents, ensuring the interrupting rating is sufficient, and recognizing that changes in utility fault currents require reevaluation.

The key idea here is that overcurrent protection devices (OCPDs) must be chosen and periodically re-verified to handle the actual fault currents the system could experience, not just rely on them to trip when a fault happens. Available fault current can change with wiring changes, added equipment, or upstream utility changes, so the protection must be checked regularly to ensure the device’s interrupting rating is still adequate.

The statement about after installation there being no need to be concerned until the device opens is not correct. Protective devices must be sized and evaluated for the maximum fault current that could occur at their location. If the available fault current increases beyond the OCPD’s interrupting rating, it may fail to interrupt safely, or equipment could be damaged. That’s why reevaluation is needed whenever system changes occur or utility fault currents change.

The other statements reflect proper practice: reevaluating OCPDs after changes that could raise fault currents, ensuring the interrupting rating is sufficient, and recognizing that changes in utility fault currents require reevaluation.