Cable tray jumper wires are used

Cable tray jumper wires, also called bonding jumpers, are used to ensure electrical continuity and grounding across cable tray sections, especially where standard splice plates may not provide reliable conductivity.Purpose of Cable Tray Jumper WiresBonding jumpers are installed to maintain electrical continuity and grounding between cable tray sections. They act as a safety measure to prevent electrical faults from causing hazards by ensuring that all metallic parts of the tray system are properly bonded to the equipment grounding conductor (EGC) and can carry fault currents safely .When Jumpers Are RequiredJumpers are not always required. Standard rigid metallic splice plates in aluminum or steel cable trays often provide sufficient electrical continuity if properly installed, clean, and tightly bolted . However, jumpers are necessary in certain conditions:Painted or powder-coated trays: Coatings can block electrical conductivity, so a copper bonding jumper ensures continuity .Expansion or adjustable splices: Flexible jumpers are needed to accommodate movement and maintain grounding .High-vibration environments: Jumpers prevent loosening of connections that could interrupt continuity .Resistance concerns: If the connection resistance exceeds 0.0003 ohms, a jumper is recommended to meet safety standards .Installation GuidelinesJumpers are typically made of flexible copper wire, often 2 AWG soft drawn, tin-plated, and insulated with flame-retardant PVC .They should be bolted to the tray channel, not to the splice plate bolts, to ensure a reliable connection .Standard lengths, such as 36 inches, are used to span expansion joints, with optional lengths available for specific applications .For aluminum trays, insulated conductors are preferred to prevent electrolytic corrosion .Best PracticesEnsure all metallic cable tray sections are bonded to the EGC for personnel and facility safety .Use serrated nuts or star washers when connecting to uncoated metal to improve electrical contact .Inspect connections regularly, especially in painted or moving sections, to maintain low resistance and compliance with NEC requirements . In summary, cable tray jumper wires are essential for maintaining grounding and electrical continuity in situations where standard splice plates may not suffice, particularly in coated, adjustable, or high-vibration installations. Proper selection, installation, and inspection of jumpers ensure safety and code compliance.