When it comes to basket-style cable trays, you'd think it would be a simple and a straightforward matter to get them to turn in different directions. They're made of heavy-gauge steel wire, so you should be able to just pull out your cable tray cutter, snip out a few strategic rungs and form your bend, right? Wrong – not if you want your installation to meet NEC and UL requirements (and believe us, you do).
Failed inspections not only equal downtime for the facilities that are unlucky enough to be saddled with them, but can also mean delayed payment for the installation contractor – any way you slice it, someone is going to lose out. If you have an upcoming cable tray installation, be sure to take our simple code-compliance advice, and set your project up for a passing grade from the get-go.
How Compliant Cable Trays Go Bad
It doesn't matter if your cable tray system was UL classified or NEC compliant when it left the factory – as soon as it's field modified, it automatically loses its code-compliant status. Why the sudden change? For starters, UL does not stand behind field modified parts, because they have no way of verifying or guaranteeing their safety post-modification. And because electrical inspectors (the people who inspect and give your installation the final thumbs-up) rely on UL to cover liability for the installed products, any modification that violates UL regulations can result in an automatic "fail" in your inspection.
Further, NEC article 392.5(E) specifies that proper fittings must be used whenever cable trays change direction or elevation. Just as with UL's requirements, this means that you can't change the path of a cable tray by removing parts (like rungs) and bending – instead, you need to add on fittings that not only allow for the directional change, but also maintain the cable tray's structural integrity and grounding path.
A Few Helpful Standards Basics You'll Need to Know:
Under NEC Article 392, metallic cable trays are required to:
- Be strong and rigid – they need to be able to support all of the wiring they're going to contain
- Have smooth edges – burrs, sharp edges, and other projections can damage cable jackets and insulation
- Be protected from corrosion – hot-dip galvanization or powder coating is must
- Have side rails – overall tray structure needs to be solid and able to contain cables
- Have fittings – changes in direction and elevation need to be accomplished with the proper fittings and hardware