Learn what the NEC requires for junction boxes, from box fill calculations and grounding to outdoor use and fire-rated wall installations. The National Electrical Code (NEC), published as NFPA 70, sets minimum safety standards for electrical junction boxes in residential and. Installation in external areas, outdoors, in damp and wet areas and rooms 1. Basic principles Depending on the local circumstances, the user may need to take additional or special measures as protec-tion, to guarantee the safe function of junction boxes. Always install your boxes where you can reach them later. A conduit body is a removable-cover section of a conduit system that provides access at junctions or termination points. Is it accessible when installed under.