Requirements for Cable Laying on Photovoltaic Cable Trays

Cable trays for PV systems must comply with NEC 690.31(C) for U.S. installations and IEC 61537 internationally, ensuring proper support, spacing, and electrical safety for PV conductors.NEC Standards for PV Cable TraysIn the United States, the National Electrical Code (NEC) 2023, specifically Article 690.31(C), governs the use of cable trays for photovoltaic systems. Key points include:Permitted Use: Cable trays can be used for PV source circuits (between modules and combiner boxes) and PV output circuits (from combiner boxes to inverters) in outdoor locations .Cable Types: Type PV wire, whether or not marked for cable tray use, is allowed in these trays .Support and Securing: Cables must be supported at intervals not exceeding 12 inches (300 mm) and secured at intervals not exceeding 4.5 feet (1.4 m) .Sizing and Ampacity: NEC 690.31(C) provides guidance on calculating ampacities, the number of conductors per tray, and tray width sizing, including considerations for layering or bundling of conductors .Outdoor Considerations: The code clarifies that these requirements apply to DC circuits on the PV side, not the AC output side of the inverter .IEC Standards for Cable TraysFor international applications, the IEC 61537 standard provides comprehensive guidelines for cable tray systems :Material and Construction: Covers trays made of steel, stainless steel, aluminum, or other metallic materials, ensuring durability and load-bearing capacity.Mechanical Performance: Trays are tested for deflection, yield strength, and working load over spans of 1 m, 1.5 m, and 2 m, with safety margins specified .Electrical Continuity: When used as part of an earthing or bonding system, trays must maintain a resistance below 0.1 ohms across joints to safely carry fault currents .Tray Selection: Depends on cable type, environment, span length, and fire rating, ensuring compatibility with PV system requirements .Best Practices for PV Cable Tray InstallationEnvironmental Protection: PV cables must withstand UV exposure, temperature extremes, moisture, and mechanical stress .Spacing and Layering: Avoid excessive bundling to prevent overheating; follow NEC and IEC guidelines for ampacity correction factors .Compliance Verification: Ensure trays and cables are certified (UL, CE, or equivalent) and meet local regulations .Maintenance Access: Design trays for easy inspection and replacement of PV cables without disrupting the system.SummaryFor safe and compliant PV installations, cable trays must adhere to NEC 690.31(C) in the U.S. and IEC 61537 internationally, covering mechanical strength, electrical safety, conductor support, and environmental resilience. Proper sizing, spacing, and certification are essential to prevent overheating, maintain system reliability, and ensure long-term performance of photovoltaic power systems .