Despite their versatility, cable trays are not suitable for every situation. They are strictly prohibited in hoistways or any location where they could face severe physical damage. This is a description of how to select, install, and support these metal or plastic frames, on which electrical wires are installed. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create. NEC Article 392 outlines the key rules for installing and maintaining industrial cable tray systems. Pallets of parts must be kept dry and stacking should be avoided. Large. All tray items whether stored outside or indoors, should be placed on sufficient support, to enable future mechanical lifting.