Every box must be closed with a securely fastened cover, faceplate, or fixture canopy. The National Electrical Code (NEC) governs electrical junction box rules. A junction box protects wire connections from physical damage, reduces shock and fire risks. NEC Article 314 establishes requirements for the installation and use of electrical boxes, conduit bodies, fittings, and handhole enclosures. Article 314 applies to: These. NEC Section 314. You must use approved materials, choose the right size box, and make sure you ground everything correctly. Many people miss these steps and face problems during. Boxes that enclose devices or utilization equipment supplied by 12 or 10 AWG conductors shall have an internal depth that is not less than 30. Where the equipment projects rearward from the mounting plane of the box by more than 25 mm (1 in. ), the box shall have a depth not less.