Photovoltaic installation cable trays and low-voltage wiring

Yes, photovoltaic low-voltage wiring can be installed in cable trays, provided NEC requirements for support, marking, and outdoor use are met.

Use of Cable Trays in PV Systems

Cable trays are a recognized wiring method for PV source and output circuits, particularly for outdoor installations. They provide structural support, organized routing, and protection for both DC and AC cables in solar PV systems, including rooftop and ground-mounted arrays, as well as connections between inverters and combiner boxes .

NEC Requirements

According to NEC Section 690.31(C)(2), single-conductor PV wire may be installed in cable trays in outdoor locations, even if the wire is not specifically rated for tray use. The code specifies that:

• Cables must be supported at intervals not exceeding 12 inches (300 mm)
• Cables must be secured at intervals not exceeding 4.5 feet (1.4 m)
• All exposed raceways, cable trays, and other wiring methods containing PV conductors must be marked with “Photovoltaic Power Source” This applies to PV source circuits (between modules and combiner boxes) and PV output circuits (from combiner boxes to inverters). Cable trays are not typically used for AC output circuits from the inverter, which follow standard AC wiring methods.

Types of Cable Trays

PV systems may use various cable tray types depending on installation needs:

• Ladder trays: Open structure, excellent heat dissipation, ideal for high-current DC cables in large ground-mounted systems.
• Perforated trays: Partial protection with flexible cable routing, common in commercial rooftops.
• Wire mesh trays: Lightweight, flexible routing, suitable for complex paths but less mechanical protection.
• Solid bottom trays: Fully enclosed, maximum protection against debris, moisture, or chemical exposure .

Practical Considerations

Using cable trays in PV systems improves maintenance, safety, and system longevity. They help prevent mechanical damage, organize cables, and ensure compliance with NEC standards. PV wire installed in trays must also meet sunlight resistance and temperature ratings appropriate for outdoor exposure . In summary, photovoltaic low-voltage wiring can include cable trays, provided the installation follows NEC 690.31(C)(2) requirements for support, securing, marking, and outdoor suitability. This method is widely used in both residential and commercial PV systems.