Oklahoma Electrical Practice Exam

When are openings in boxes or raceways considered effectively closed?

1. If listed material that has equivalent thickness is utilized to close the opening

2. If the opening is painted to match the surrounding surface

3. If the opening is covered with duct tape

4. If a non-conductive material is used

The correct answer is: If listed material that has equivalent thickness is utilized to close the opening

An opening in electrical boxes or raceways is considered effectively closed when listed materials that have equivalent thickness to the original box or raceway structure are used. This ensures that the integrity and safety of the electrical box or raceway are maintained, as it prevents dust, moisture, or other contaminants from entering, while also ensuring that the fire and mechanical protection characteristics are not compromised. Using listed materials is crucial as they have been tested and verified for safety and performance under electrical code requirements. This approach helps to adhere to the National Electrical Code (NEC) guidelines, which promote safe practices in the installation and maintenance of electrical systems. The other options may suggest various methods to cover openings, but they do not meet the electrical code's requirements for effectively closing openings in boxes or raceways.