Cable Trays Versus Conduit

Conduit is still the most popular choice for many electrical 
installations. In industrial applications, conduit gives more choices 
for the many and various environments found in industrial setting.<br><br>For
 example, food and beverage processing facilities will have harsh 
environments that can damage conductors easily. Some are caused by the 
process itself, while other conductor hazards come from the sanitation 
chemicals and processes used to ensure food and beverage safety. AFC Cable Systems

Steve Maurer, IME

Conduit is still the most popular choice for many electrical installations. In industrial applications, conduit gives more choices for the many and various environments found in industrial setting.

For example, food and beverage processing facilities will have harsh environments that can damage conductors easily. Some are caused by the process itself, while other conductor hazards come from the sanitation chemicals and processes used to ensure food and beverage safety.

But cable trays are becoming increasing popular in commercial applications as well as in industrial settings.

Obviously, cable tray use has limitations in some environments. However, when cable trays are permitted, the cost of installation will often be a determining factor in choosing trays over conduit.

In many cases, the installation of cable trays requires less expertise than running conduit. Cutting, joining and hanging of trays arguably requires less skill than cutting, threading bending, joining and sealing of conduit assemblies.

Cable trays aren't considered raceways by the NEC. Article 100 of the NEC defines a raceway as "an enclosed channel of metal or nonmetallic materials designed expressly for holding wires, cable, or bus bars, with additional function as permitted in this Code."

Because of their open construction, cable trays are not classified as true raceways, even though they perform some of the functions. The NEC defines a cable tray system this way: a unit or assembly of units or sections and associated fittings forming a rigid structural system used to securely fasten or support cables and raceways.

It's important to note that you can't use every type of cable or conductor in a cable tray system. The cables used must be rated for use in cable tray applications. Of course, single conductors, such as THHN and THWN cannot be laid directly in a tray. They must be sheathed in an approved conduit or raceway, with flexible MC and AC the most commonly used.

Because cable tray is gaining traction, many armored cable manufacturers are color coding the flexible conduit for both phasing and usage, saving installers a lot of time in the field.

For datacomm and signaling applications, the use of trays is increasingly widespread. Not only does it speed up the installation of these low-voltage cables, but it also makes reconfiguring much easier when the layout changes. That's one reason you'll see cable trays in many new data centers.

Using conduit versus cable trays often comes down to application, and overall installations costs. In some cases, it's a tradeoff between the more expensive cables used in tray installs over the total cost of conduit and conductors.

A large discount retailer commissioned a study and found that, in their particular application, using cable trays in conjunction with MC cable actually reduced material and installation costs by 30 percent over installing EMT and pulling conductors.

Cable tray use has boomed in countries outside the United States. And it is gaining popularity in the US and Canada. You might want to consider it as well. Just make sure you factor in all the necessary considerations, including conductor protection from the environment it's installed in.


Photo courtesy of AFC Cable Systems