Cable tray jumper specifications

Bonding jumpers are generally not required for standard rigid metallic splice plates unless the tray is painted, powder-coated, or includes expansion joints.Standard Splice Plates and Electrical ContinuityFor standard rigid aluminum or steel cable tray splice plates, the plates themselves typically provide sufficient electrical continuity between tray sections when properly bolted. UL-classified splice plates, when tightly secured, can carry fault currents safely without additional jumpers, meeting NEC grounding requirements and NEMA guidelines . Installing extra bonding jumpers in these cases does not improve safety and may unnecessarily increase labor and material costs .Situations Requiring Bonding JumpersBonding jumpers become necessary in specific conditions:Painted or powder-coated trays: Coatings can block electrical continuity, so a flexible copper bonding jumper ensures a reliable path .Expansion or adjustable splices: Movement in the tray system can interrupt continuity; jumpers bridge these discontinuities .High-vibration environments: To maintain low-resistance connections, jumpers may be required to prevent loosening or intermittent contact .When used, bonding jumpers are typically made of 2 AWG soft-drawn tin-plated copper stranded cable with flexible, flame-retardant insulation, and are bolted directly to the tray channel rather than the splice plate . Standard lengths, such as 36 inches, are designed to span expansion joints effectively .Electrical Resistance ConsiderationsA connection resistance above 0.0003 ohms usually indicates the need for a jumper to ensure safety and compliance . Properly installed standard splice plates generally maintain resistance below this threshold, making additional jumpers unnecessary in typical indoor installations with galvanized steel or aluminum trays .Compliance with StandardsCable tray systems must comply with NEC Article 250 and 392.60 for grounding and bonding. Standard metallic splice plates, when installed correctly, satisfy these requirements without additional jumpers . NEMA VE-2 guidelines provide further recommendations for tray design and installation, emphasizing that bonding jumpers are only required when continuity cannot be guaranteed by the splice plates alone .SummaryNo jumper needed: Standard rigid metallic splice plates, properly bolted, uncoated trays.Jumper required: Painted/powder-coated trays, expansion joints, adjustable splices, or high-vibration environments.Material: Flexible copper, 2 AWG, flame-retardant insulation.Compliance: NEC 250/392.60, NEMA VE-2, UL-classified splice plates.Following these guidelines ensures electrical safety, regulatory compliance, and reliable grounding in cable tray installations.