Answer: The NEC does not have a specific installation clearance, but indicates in section 318-6 (b) that cable trays should be exposed and accessible. The primary rulebook used in the safe use of cable trays is NEC Article 392. This is a description of how to select, install, and support these metal or plastic frames, on which electrical wires are installed. For the installation of single conductor cables sized 1/0 AWG to 4/0 AWG in industrial establishments, the NEC specifies the maximum allowable rung spacing for the cable. Answer: No. 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. Some cable tray systems are appropriate for under floor use, despite the fact that they are normally suspended from ceilings (or) attached to walls.
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