Final answer:
Unused openings in cabinets and panelboards must be effectively closed or sealed to provide safety equivalent to the wall of the cabinet, preventing dust, water, or foreign objects from entering.
Step-by-step explanation:
The student's question pertains to compliance with safety standards for electrical installations, specifically within the context of National Electrical Code (NEC) requirements or similar regulations. The question asks: "Unused openings in cabinets and panelboards shall be effectively _____ to afford protection equivalent to that of the wall of the cabinet." The blank should be filled with the word closed or sealed.
Unused openings in electrical cabinets and panelboards must be closed or sealed to prevent the entry of dust, water, or any foreign objects that could cause a short circuit or electric shock. Therefore, these openings must be covered with a proper closure, such as a metal plate or sealant, that provides protection equivalent to that of the cabinet itself. Ensuring that these openings are properly sealed also minimizes the risk of electrical fires and enhances the overall safety of the electrical installation.