Cable trays are a type of building material used to carry wires, cables and conduits safely through a building. Instead of allowing wires to be run throughout the walls and ceiling space unprotected, cable trays allow installers to run these wires in a controlled manner. These trays can carry electrical, telecommunications or security wires, along with any other type of electrical cables required within the building. Many local and national building codes require the use of cable trays in a variety of applications, though specific requirements can vary.
Depending on the application, cable trays may be made from steel, aluminum or fiberglass-reinforced plastic (FRP). The decision on which material to use largely depends on local building code requirements, though budget can also be a factor in this decision. The total volume or electrical load that each tray can carry is determined both by the manufacturer and by local inspectors.
Installers fasten these trays to wall and ceiling framing using trapeze bar hangers or J-hooks. Some center-hung supports are also available to allow installers to fill the trays from either side after they are hung. In raised-flooring applications, a cable tray system can also be installed below the floor to carry wires safely.
Buyers can choose from a number of different cable tray designs. Ladder-types trays are one of the most common, and can be used over a relatively long span without intermediate supports. They provide a high level of ventilation for the wires and cables from all sides, and also allow for easy access from either side of the tray.
Solid, or “trough,” cable trays are the best variety for protecting the cables and wires within, but offer little to no ventilation. They are most commonly found over relatively short spans because of their added weight. At the other end of the spectrum, the single rail cable tray leaves wires and cables almost completely exposed. A single support rail runs down the center of the tray, and curved “fingers” run perpendicular to the rail to support the weight of the cables. Single rail cable trays are the most flexible and economical, and are generally used for low-voltage wiring.
The main function of the cable tray is to protect the wires and cables within. These trays also keep wires organized, and make it easier for maintenance personal to locate and maintain wiring and related components. The tray makes it simple to trace a wire to its source in order to make repairs, and also allows for more effective fire-sealing between walls. By keeping the cables protected, a cable tray also lowers the risk of electrical shock to maintenance personnel and installers.