Which NEC article governs box enclosures and box-fill calculations?

• A. Article 314
• B. Article 320
• C. Article 680
• D. Article 400

Answer: (A)

Box enclosures and how much space they need for conductors are specified in Article 314. This section covers the types and sizes of boxes and the box‑fill calculations used to ensure there’s enough interior space for all conductors, devices, clamps, and internal fittings. The counting method provided by Article 314 requires counting every conductor that originates outside the box and terminates or is spliced inside, counting all equipment grounding conductors as a single conductor, counting internal clamps as one, and counting any device yokes as one each. Once you have that total, you compare it to the box’s cubic‑inch rating to confirm there’s adequate space. The other articles mentioned deal with different topics—Armored Cable (Type AC) for 320, swimming pools/spas for 680, and flexible cords for 400—so they’re not about box enclosures or box fill.