Requirements for photovoltaic cable tray installation

PV cable trays can be installed outdoors for both PV source and PV output circuits, provided cables are properly supported and secured according to NEC 690.31(C)(2).Key Installation Requirements

Outdoor Suitability: Cable trays for PV systems are permitted in outdoor locations for PV source circuits (between modules and combiner boxes) and PV output circuits (between combiner boxes and inverters) even if the cables are not specifically rated for cable tray use, as long as they are listed as PV wire . Support and Securing Intervals:

• Cables must be supported at intervals not exceeding 12 inches (300 mm) along the tray .
• Cables must be secured at intervals not exceeding 4.5 feet (1.4 m) to prevent movement and maintain proper alignment . Cable Tray Design Considerations:
• Ladder-style trays are commonly used, with rung spacing between 6 and 18 inches, typically 6–12 inches for PV applications .
• Ventilated or solid-bottom trays can be selected depending on environmental exposure and heat dissipation needs .
• Material selection (aluminum, steel, or coated finishes) should consider corrosion resistance and mechanical strength for outdoor conditions . Conductor Types and Sizes:
• Single-conductor PV wire of any size can be installed in cable trays outdoors .
• For ground-mounted PV systems, PV wire smaller than #1/0 AWG is permitted in trays, even if outside the scope of traditional TC ratings . Physical Protection:
• Cable trays provide superior protection against physical damage compared to direct burial or unsupported runs .
• Clips or fasteners should be installed within 12 inches of conductor entry points and spaced according to manufacturer instructions to prevent conductor lift . Compliance Notes:
• NEC 690.31(C)(2) governs the use of cable trays for PV source and output circuits.
• Ensure that all installations meet local AHJ interpretations and follow manufacturer guidelines for tray fill, support, and environmental exposure . By following these requirements, PV cable tray installations will be safe, code-compliant, and durable for outdoor photovoltaic systems.