The National Electrical Code (NEC) mandates that every junction box, pull box, or conduit body must be installed so that the wiring within it can be accessed without removing any part of the building structure or finish. NEC junction box code covers box fill, access, covers, grounding, support, and location suitability for safer, inspection-ready box selection. What NEC Rules Apply to Junction Boxes? NEC 314. A junction box protects wire connections from physical damage, reduces shock and fire risks. How you use a junction box determines its clearance requirements. 26 working space requirements apply.