A perforated cable tray—also called a ventilated trough tray —features a solid bottom with regularly spaced ventilation holes and continuous side rails. For a few types of installations, the National Electrical Code (NEC) specifies the cable tray type to be used: Single conductor cables and Type MV cables must be installed in ladder or ventilated trough cable trays. most common and widely used, accounting for about 75% of all cable tray sold. Unlike ladder trays, the bottom surface provides continuous cable support, while the perforations. Determine the tray series using the NEMA load/ span designations page A14, and sizing cable tray page A21. It has three load carrying capabilities: Heavy Duty Return Flange, Medium Duty Return Flange and Light Duty.
