The NEC permits power and signal cables in the same tray under specific conditions. Power cables rated 600V or less and Class 2 or Class 3 signal cables may share a tray if separated by a fixed barrier or if the power cables are separated from the signal cables . Cable tray types, fill rules for single-conductor and multiconductor cables, ampacity derating, separation requirements, and when to use tray vs conduit. Cable tray is the preferred wiring method for industrial facilities, data centers, and large commercial buildings where routing dozens or. Several factors determine the number of cables a cable tray can hold: Cable Tray Size: The width and depth of the tray determine its total area.