Do horizontal cable trays for low-voltage wiring need to be grounded with flat iron

Horizontal metallic cable trays for low-voltage wiring must be grounded, but using flat iron is not strictly required if proper bonding or an approved equipment grounding conductor is used.NEC RequirementsAccording to NEC Article 392, all metallic cable trays must be grounded and bonded to ensure electrical safety, even if they are not carrying power circuits . Grounding prevents electrical shock, reduces the risk of equipment damage, and ensures a continuous path for fault currents . For low-voltage or signal circuits, grounding is primarily for EMI protection, lightning, and noise mitigation, rather than carrying high fault currents .Methods of GroundingTray as Equipment Grounding Conductor (EGC)Metallic trays can serve as the EGC if they meet cross-sectional area and continuity requirements .All tray sections must be electrically continuous, bonded at joints, and connected back to the main grounding system .Separate Bonding ConductorA separate conductor (e.g., copper wire) can be installed along the tray to bond sections together and to the building ground .This is often used when the tray cannot reliably serve as the sole EGC or for long runs.Integrated EGC in CablesLow-voltage cables with built-in grounding conductors can provide additional grounding points .This method is common in telecommunications and signal circuits, where the tray itself may not carry significant fault current.Use of Flat IronFlat iron is not specifically required by the NEC for grounding cable trays. The key requirement is electrical continuity and proper bonding. Flat iron or other metallic strips may be used as bonding jumpers if needed to ensure continuity across tray sections or gaps .For low-voltage wiring, the focus is on shielding and EMI protection, so a properly bonded tray or EGC conductor is sufficient without necessarily using flat iron.Practical RecommendationsEnsure all metallic tray sections are bonded together and connected to the building grounding system.Use bonding jumpers where tray sections are separated or interrupted.For low-voltage or signal circuits, consider shielded trays or grounding at multiple points to reduce EMI.Verify compliance with NEC 250.96 and 392.60 for grounding conductor sizing and continuity . Conclusion: Horizontal metallic cable trays for low-voltage wiring must be grounded, but NEC does not mandate flat iron specifically. Proper bonding, either through the tray itself, a separate conductor, or integrated EGCs in cables, satisfies the grounding requirements and ensures safety and EMI protection.