The grounding wire diameter of the cable tray is

The typical grounding wire (equipment grounding conductor) for cable trays is sized according to NEC Table 250.122, often ranging from #10 AWG copper for small circuits to larger sizes for higher ampacity circuits, with upsizing required if phase conductors are upsized.Grounding Wire BasicsA grounding wire in a cable tray system provides a safe path for fault currents to flow to earth, protecting personnel and equipment from electrical hazards . The wire can either run continuously along the tray or the tray itself can serve as the grounding path if it meets conductivity and mechanical requirements . For non-metallic or wire mesh trays, a separate grounding conductor is recommended .Typical Sizing GuidelinesNEC Table 250.122 specifies minimum sizes for copper and aluminum equipment grounding conductors (EGCs) based on the overcurrent protection device rating .For example:A 15–20A circuit typically uses #14 or #12 AWG copper EGC.A 60A circuit typically requires #10 AWG copper, which may be upsized to #8 AWG if phase conductors are upsized for voltage drop or other considerations .Aluminum EGCs are generally one to two AWG sizes larger than copper equivalents .The grounding conductor must be electrically continuous, mechanically secured, and bonded to each tray section or alternate sections using grounding clamps .Practical ConsiderationsMaterial compatibility: Avoid bare copper in aluminum trays to prevent electrolytic corrosion; insulated conductors with tin or zinc-plated connectors are preferred .Tray as EGC: Steel trays can serve as EGC for circuits with ground-fault protection up to 600A, aluminum trays up to 2000A .Voltage drop and ampacity: For long runs, the EGC may need to be upsized proportionally to the phase conductors to maintain proper fault clearing .Inspection and maintenance: Ensure grounding connections remain tight and corrosion-free to maintain low resistance (ideally ≤4 ohms) for effective fault current diversion .SummaryThe typical grounding wire size for cable trays depends on the circuit breaker rating, conductor material, and installation specifics. Using NEC Table 250.122 as a reference, copper EGCs usually range from #10 AWG for moderate loads to larger sizes for higher ampacity circuits, with upsizing required for long runs or increased phase conductor sizes. Proper bonding, material selection, and adherence to NEC and local codes are essential for safety and system reliability .