Requirements for jumpers of different cable tray specifications

Bonding jumpers are required only under specific conditions such as painted trays, expansion joints, or high-vibration environments; standard metallic splice plates often provide sufficient electrical continuity for properly installed cable trays.General GuidelinesFor metallic cable trays (aluminum, steel, or stainless steel), electrical continuity is critical to ensure proper grounding and safety. According to NEC standards, metallic trays must be electrically continuous and bonded to the building grounding system. In many cases, standard rigid bolted splice plates provide sufficient continuity without additional jumpers, as long as the plates are tightly bolted and free of coatings that impede conductivity .When Bonding Jumpers Are RequiredBonding jumpers are necessary in the following situations:Painted or powder-coated trays: Coatings block electrical contact, so a flexible copper jumper ensures continuity .Expansion joints: Trays that need to move or accommodate thermal expansion require jumpers to maintain grounding .High-vibration environments: Jumpers prevent loosening of connections and maintain electrical continuity .Connection resistance above 0.0003 ohms: If the splice plate connection exceeds this resistance, a jumper is recommended to ensure safety and compliance .Cable Tray Types and ConsiderationsDifferent tray types may influence jumper requirements:Ladder trays: Typically allow good electrical continuity through side rails; jumpers may not be needed if splice plates are UL-rated and properly bolted .Trough and solid-bottom trays: May require jumpers if coated or if mechanical connections are insufficient for continuity .Channel trays: Similar to ladder trays, but check for coatings or expansion joints that could necessitate jumpers .Installation Best PracticesUse serrated nuts or star washers to ensure metal-to-metal contact.Ensure tight bolting of splice plates to side rails.Verify UL classification of splice plates; UL-rated plates may eliminate the need for jumpers in standard conditions .Maintain proper tray fill capacity (generally 50% or less) to avoid overheating and ensure safe operation .Separate power and data cables to reduce EMI and maintain system performance .Compliance and SafetyAll metallic trays must comply with NEC Article 392 for grounding and bonding .Field verification of dimensions, routing, and connections is essential to ensure that the system meets both mechanical and electrical requirements .For painted or moving trays, always install flexible copper bonding jumpers to pass inspections and maintain safety . By following these guidelines, installers can ensure that cable tray systems are electrically continuous, code-compliant, and safe, while avoiding unnecessary use of bonding jumpers where standard splice plates suffice.