How far apart should cable trays be grounded

Cable trays should generally be grounded every 10 meters, though some guidelines allow up to 20 meters under less demanding conditions.Recommended Grounding SpacingFor metallic cable trays, grounding is essential to ensure electrical safety and provide a low-resistance path for fault currents. Experts recommend grounding every 10 meters to maintain reliable electrical continuity, especially in adverse environmental conditions . Some installations may use 20-meter intervals as a less stringent practice, but this is typically reserved for standard conditions where mechanical and electrical stresses are minimal .Best Practices for GroundingBonding Between Sections: Each cable tray section should be mechanically tight and electrically continuous. Grounding clamps or bonding jumpers are recommended at splice points to ensure continuity .Equipment Grounding Conductor (EGC): If a separate EGC is installed in or on the tray, it should be bonded to each or alternate tray section. This helps prevent the EGC from being displaced under fault current conditions .Material Considerations: Avoid bare copper in aluminum trays to prevent electrolytic corrosion; use insulated conductors with exposed ends at bonding points .NEC Compliance: All metallic trays must be grounded according to NEC Article 250.96, regardless of whether the tray itself serves as the EGC . Proper sizing of the grounding conductor should follow NEC tables to safely carry potential fault currents .SummaryTo ensure safety and compliance, ground metallic cable trays at intervals of approximately 10 meters, using proper bonding techniques and conductor sizing. In less demanding environments, intervals up to 20 meters may be acceptable, but closer spacing improves reliability and reduces the risk of electrical hazards .