Cable tray types explained
Recognize four common structures: ladder, ventilated trough, solid-bottom and wire mesh. Start with the construction, then check the product’s capabilities.
Ladder tray
Two side rails joined by spaced rungs support the cables. The open spaces between rungs distinguish the ladder structure. Specify rung spacing as well as width; it is a different dimension from the distance between the supports carrying the tray.
Ventilated trough
A formed bottom with openings provides a different support surface from widely spaced ladder rungs. Opening size, usable width and cable support details depend on the product. Check its actual construction rather than assuming every perforated tray is identical.
Solid-bottom tray
A continuous bottom supports the cables. A cover is a separate feature, so “solid bottom” does not by itself mean the complete system is enclosed. Consider the installation’s heat and access requirements and the relevant cable rules.
Wire-mesh tray
Welded wire forms an open basket-like structure. Mesh size, wire details and the maker’s fittings affect how the route is assembled. Follow the product’s instructions for forming, connecting and supporting it; do not treat it as a ladder section with different artwork.
Type names do not determine load capacity
Two trays with the same width and general shape can have different load ratings, support spans, materials and connection details. Use the manufacturer’s load and span information for the exact product. A fill percentage cannot tell you how far apart the supports may be.
Write down inside width, useful reference height, cable outside diameters and route changes before comparing products. Keep a separate list of environmental, loading and electrical requirements. This makes the comparison more useful than selecting by appearance alone.
Compare cable space separately
The area fill calculator compares cable cross-sectional area with a rectangle you define. It does not choose a tray type or assign a universal allowed percentage. Read the terminology guide for the difference between width, span, fill and ampacity.
Structural terminology references: Cable Tray Institute FAQ and codes and standards overview. Drawings above are simplified original schematics, not product details or installation instructions.