Journeyman Electrician Practice Exam 2025 - Free Electrician Practice Questions and Study Guide

The correct answer highlights that installing an open circuit breaker is not permitted for closing an unused circuit breaker opening in panelboards. This is due to safety regulations and standards that require all circuit breakers to be functional and capable of interrupting the circuit they protect. An open circuit breaker does not serve this purpose and could lead to potential hazards, such as exposing the opening to unintended contact or creating a false sense of security about the state of the circuit.

In contrast, installing a closure plate or a listed spare circuit breaker is permitted because these options effectively seal off the unused space, preventing any accidental contact or entry into the panelboard. A closure plate securely covers the opening and ensures a clean and safe installation. Meanwhile, a listed spare circuit breaker can be utilized to fill the opening, allowing for easy future expansion if needed, and maintaining compliance with electrical safety codes.