Pro Tip: Leave at least 15 to 20 percent spare capacity in every tray run, even if NEC fill limits allow more. Future cable additions are inevitable in any industrial facility, and pulling new cables through a full tray risks damaging existing insulation. The mechanical and electrical characteristics, tests, certifications, overall quality management, recommendations mentioned in this technical guide only apply to our own cable management ranges and cannot under any circumstances be transposed to si osure, overheating or. 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. 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. Standard Widths: Side Rail Heights: Standard Lengths: Rung Spacing Options: Material Thickness:. tray installation for electrical systems should Not run under other types of canalisations such as water, vapour or gas canalisations. Select your tray type (ladder, ventilated trough, solid bottom, or channel), enter the tray width.