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Wire Cable Trays: Modification and Code Compliance

 

 

Cable Tray Layout - CM20When it comes to basket-style cable trays, you'd think it would be a simple and 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.

 

Keeping Your Cable Tray Installation on the Right Path
Sound complicated? It isn't, as long as you're using Cable-Mgr cable trays by Wiremaid. Because Wiremaid's CM10, CM20 and M.E.2 cable tray lines include an extensive selection of pre-fab turns, junctions, reducers and drops, you never need to worry about compliance-botching modifications. Whether you need to make a 90° turn or branch off into a T-shaped intersection or 4-way crossroad, the creators of Cable-Mgr trays have thought it all out ahead of time. Once you have your cable basket configuration mapped out, you just need to order the appropriate fittings, and drop them right into place.

It's pretty easy to see that this takes care of the structural requirements, but when used as specified, Cable-Mgr systems automatically fulfill grounding requirements as well. Under the UL Cable Tray Program (CYNW), Wiremaid cable trays and fittings are classified as equipment grounding conductors, and actually form an automatic and continuous ground path when connected to each other. Cable-Mgr cable tray designs incorporate patented ground/splice loops, which simplify grounding and reduce your overall bill of materials, thanks to the fact that they eliminate the need for additional ground splices. The only pieces of hardware required for proper Cable-Mgr tray assembly are carriage bolts and nuts, which just happen to be included.

 

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

 

For more information on cable tray code compliance, please visit the NEC standards website, or check out UL's CYNW cable tray guide.

 

 

©2014 CableOrganizer.com, LLC. This article may not be reproduced in part or in full without the written permission of CableOrganizer.com.
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