Cable Tray Systems

Tray is a support system, not a raceway, so only cables and conductors approved for tray go in it. It shines in plants where you are constantly adding and pulling circuits.

Fill and rung spacing matter for both heat and mechanical support. And the tray itself can serve as an equipment ground only when it is listed and bonded for that duty.

When it applies

Cable tray is the open support highway for wiring across plants and big commercial buildings. Article 392 tells you what cable types can ride in it, how to figure fill, how to support it, and how to ground the tray itself. The appeal is access: you can lay in new runs and pull old ones without fishing conduit.

Common mistakes

• Overfilling the tray, single-conductor and multiconductor fill are calculated differently and people mix the methods up.
• Forgetting that tray used as an equipment grounding conductor must be listed and marked for it, with proper bonding jumpers across expansion splices.
• Dropping cable off the side of a tray without a listed strain-relief fitting at the exit.

In the field

On a retrofit I always verify the existing tray's ground continuity across every splice plate before adding load. A painted-over splice bolt can quietly break the bond, and then the tray is no longer the safety path you assumed it was.