Due to their exposure to the open air because of the cable trays, the wires contained within need a very durable outer covering. The regulations dictate that the cables must either be Type TC (also known as Tray Rated) or must be metal-armored (Type MC). But can tray cables be used effectively in residential wiring? This inquiry is not without merit, as the electrical landscape continually adapts to meet modern demands for safety and efficiency. This is a description of how to select, install, and support these metal or plastic frames, on which electrical wires are installed. You should consider it as a series of instructions that make the buildings resistant to. When running wiring in areas prone to excessive moisture or direct contact with concrete, standard nonmetallic-sheathed (NM) cable is unsuitable as it is designed for dry locations. Cable installed in a concrete slab, or in a raceway within a slab in direct contact with the earth, is considered to. Where cable is run at angles with joists in unfinished basements and crawl spaces, it shall be permissible to secure cables not smaller than two 6 AWG or three 8 AWG conductors directly to the lower edges of the joists.