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Cable tray types

The cable tray is a rigid system made up of units or sections and fittings that allows safely securing and supporting insulated electrical cables for power distribution, control, and communications. It is used as an alternative to open wiring or conduit systems, especially when wiring modifications are anticipated, since conductors are placed without needing to be pulled through a closed tube.

Classification

Section titled “Classification”

Cable trays are divided into five main types according to the construction of the bottom and the cable support arrangement: ladder-type tray, solid-bottom tray, ventilated tray, wire mesh or basket tray, and channel-type tray. Each offers different characteristics of protection, ventilation, and capacity to adapt to specific applications.

Ladder-type tray

Section titled “Ladder-type tray”

In the ladder-type tray, the cables rest on horizontal rungs spaced at regular intervals, similar to the steps of a ladder. The rungs are made from metal profiles and are joined to two longitudinal side rails, forming an open structure that allows maximum ventilation and easy access for inspection.

This type of tray is ideal for large-size power cables in heavy industrial and commercial installations, as well as for trunk routes requiring high load support. It is typically manufactured in galvanized steel, stainless steel, or aluminum, in widths ranging from 150 mm to 900 mm (6 to 36 inches) and with a rung spacing of 100 to 300 mm (4 to 12 inches). The height of the side rails is usually 100 mm to 150 mm (4 to 6 inches) to provide the necessary rigidity. It can be supplied with solid covers to protect cables from falling objects, dust, and moisture, especially outdoors or in environments with airborne particles.

Solid-bottom tray

Section titled “Solid-bottom tray”

The solid-bottom tray has a completely closed base without perforations, providing maximum protection to the cables against falling objects, light liquid spills, dust, or debris that might settle from above. For entry or exit of conductors, it is necessary to cut the base or use special branching fittings.

This design is selected in applications where mechanical protection of the wiring is a priority, such as in process plants, laboratories, or areas where containment of electromagnetic interference is required. The most common materials are galvanized steel, stainless steel, and aluminum. Lacking openings, it offers no natural ventilation, so cable heating in high-current circuits must be monitored. The installation can be supplemented with solid or peaked covers to evacuate dust, ice, or snow.

Ventilated tray

Section titled “Ventilated tray”

The ventilated tray has perforations in the bottom that allow some air circulation around the cables, as well as drainage of water and the fall of small dust particles. The openings can be elongated slots or round holes punched into the sheet metal, and small-diameter cables can exit through them without additional fittings.

It is commonly used in commercial and industrial installations where an intermediate level of protection combined with some heat dissipation is desired. Materials include galvanized steel, stainless steel, and aluminum. Like the ladder-type tray, it accepts solid covers to turn it into a closed raceway when environmental conditions require.

Wire mesh or basket tray

Section titled “Wire mesh or basket tray”

The wire mesh tray, also called cable basket, is constructed from electrowelded steel wires forming a mesh that allows supporting a large number of small-diameter cables, such as those used in voice, data, and control networks. It is a very lightweight system, quick to install, and highly flexible for making direction and level changes through field cuts and bends.

It is typically manufactured in galvanized steel or stainless steel, with wire diameters from 4 mm to 6 mm (0.16 to 0.24 inches) and a mesh grid spacing from 50 mm × 50 mm to 100 mm × 100 mm (2 x 2 to 4 x 4 inches). Its load capacity is lower than that of rigid metal trays, making it suitable for secondary distribution runs in data centers, offices, and plants with high-density structured cabling.

Channel-type tray

Section titled “Channel-type tray”

The channel-type tray is an open “U”-shaped profile, generally of small dimensions, offering an economical support for short branch runs, drops, and equipment feeds. It is usually mounted against a wall or suspended from the ceiling, and is installed in place of conduit when conduit is inconvenient.

It is available in typical widths from 50 mm to 300 mm (2 to 12 inches) and heights from 25 mm to 100 mm (1 to 4 inches). The predominant materials are galvanized steel and aluminum. Due to its closed bottom, it provides high localized protection for a limited number of cables, although it does not allow ventilation. It is complemented with fittings such as elbows, tees, and reducers to form a complete distribution system.

Comparison table

Section titled “Comparison table”
Type Description Ventilation Common materials Typical applications
Ladder Horizontal rungs spaced apart that support the cables High, due to the open structure Galvanized steel, stainless steel, aluminum Trunk routes with power cables, heavy industry
Solid bottom Fully closed base without openings None Galvanized steel, stainless steel, aluminum Maximum protection against external agents, process plants
Ventilated Bottom with perforations (slots or holes) Medium, through the openings Galvanized steel, stainless steel, aluminum Commercial and industrial installations with intermediate needs of protection and heat dissipation
Wire mesh or basket Electrowelded wire mesh Very high, due to its open construction Galvanized steel, stainless steel Structured cabling, data, control; offices and data centers
Channel “U”-shaped profile with closed bottom None Galvanized steel, aluminum Short branch runs, drops, equipment feeds when conduit is not desired

Note: The spacing between rungs in the ladder-type tray is 100 to 300 mm (4 to 12 inches), the only dimensional numerical value that directly arises from standardized construction.

Frequently Asked Questions (FAQ)

Section titled “Frequently Asked Questions (FAQ)”

What is the typical spacing between rungs in a ladder-type tray?

Section titled “What is the typical spacing between rungs in a ladder-type tray?”

The spacing between rungs is normally between 100 mm and 300 mm (4 to 12 inches), depending on the support span and the expected load.

What is the standard width of a cable tray?

Section titled “What is the standard width of a cable tray?”

Commercial widths range from 50 mm to 900 mm (2 to 36 inches), with the most common in industrial installations being 150, 300, 450, and 600 mm.

What is the height of the side rails in a ladder-type tray?

Section titled “What is the height of the side rails in a ladder-type tray?”

The height of the side rails is usually 100 mm to 150 mm (4 to 6 inches), which ensures mechanical rigidity and allows enough cable layers to be contained.

What is the depth of a channel-type tray?

Section titled “What is the depth of a channel-type tray?”

Channel-type trays are manufactured with depths from 25 mm to 100 mm (1 to 4 inches), depending on the number and size of the cables to be housed.

What wire diameter is used in wire mesh tray?

Section titled “What wire diameter is used in wire mesh tray?”

The diameter of the electrowelded steel wire varies between 4 mm and 6 mm (0.16 to 0.24 inches), defining the mechanical strength of the system.

What is the maximum fill percentage in a cable tray according to the NEC?

Section titled “What is the maximum fill percentage in a cable tray according to the NEC?”

The National Electrical Code (NEC) allows a 50% fill of the cross-sectional area for power and control cables, although additional limitations may exist due to heating or grouping.

Consulted sources

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References

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