Which NEC provisions govern the closure of unused knockouts in electrical boxes and cabinets?

• A. NEC 110.12A
• B. NEC 314.17A
• C. Both NEC 110.12A & NEC 314.17A
• D. NEC 300.5

Answer: (C)

Closing unused knockouts in boxes and cabinets is about keeping the enclosure safe and intact so there’s no path for moisture, dust, or contact with live parts. The rule that directly covers this is 314.17A, which requires closing any unused openings with listed closures or blank covers. This keeps the interior protected and maintains proper enclosure integrity.

Supporting that specific requirement, 110.12A provides the general safety framework for electrical equipment and enclosures. It emphasizes that equipment must be installed and maintained in a way that protects workers from shock and other hazards, which includes ensuring openings are properly closed so the enclosure remains a safe barrier.

The other option isn’t about closing unused knockouts. So, the combination of applying the specific closure requirement (314.17A) along with the general safety guidance (110.12A) explains why both provisions govern this situation.