Cable tray systems are structural components used to support insulated conductors and control, instrumentation, and communication cables. They are typically installed overhead, along walls, or under raised floors in electrical rooms, industrial plants, process areas, and. maintain spacing or to keep cables in place when the tray is ect the minimum bend ra-dius for cables as they exit the bottom of the cable tray. A rung spacing of 6 to 9 inches (150 to 230 mm) is preferable when the cable tray cont d for instrumentation and control applications that require. This publication is intended as a practical guide for the proper and safe* installation of cable ladder systems, cable tray systems, channel support systems and associated supports. Fittings can, on the one hand, be used for horizontal or vertical changing of the routing direction or, on the other, to change the height or width of the. Below are the key principles to guide the layout of E&I cable trays, focusing on practical, safety, and efficiency aspects. Separation of Electrical and Instrumentation Cables Electrical on Top, Instrumentation Below: Typically, electrical trays are positioned above instrumentation trays.