No foreign objects allowed on cable trays

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). Grounding: Metallic trays can serve as equipment grounding conductors (EGC) if they meet NEC requirements. This is a description of how to select, install, and support these metal or plastic frames, on which electrical wires are installed. NEC section 300-8 does not permit any tube, pipe, or equal for water, air gas, drainage, steam, or any service other than electrical in raceways or cable trays containing. All rights, including translation...