Where to connect the wires in the photovoltaic combiner box

Connect each DC string to its designated fuse holder or breaker, then to the main busbar, ensuring correct polarity, secure torque, and proper grounding for safety and efficiency.

Connecting DC Strings

Each solar string should be connected to the input terminals of the combiner box, typically through individual fuses or circuit breakers. Positive (+) and negative (-) conductors from each string must be connected to their respective terminals, following the wiring diagram provided by the manufacturer. This ensures overcurrent protection and allows isolation of faulty strings without affecting the rest of the system.

Main Busbar and Output

After fuses or breakers, the wires should be routed to the main busbar, which consolidates the current from all strings. From the busbar, a single pair of output wires connects to the inverter or charge controller. Ensure that the polarity is correct and that all terminals are tightened to the recommended torque to prevent overheating or arcing.

Surge Protection and Grounding

If the combiner box includes SPD (surge protection devices), connect them according to the manufacturer's instructions, keeping leads short and direct. The metallic enclosure and PE terminals must be bonded to the system grounding conductor to protect against lightning and fault currents.

Installation Tips

Strip insulation carefully and use ferrules on multi-strand conductors to prevent fraying. Install the combiner box in a well-ventilated, weather-protected area with IP65/66-rated enclosure. Leave sufficient space around the box for cable routing, inspection, and maintenance.

Label each string clearly to facilitate commissioning, testing, and troubleshooting. Verify all connections with a multimeter before powering the system. By following these steps, the combiner box will safely and efficiently combine multiple PV strings, protect against faults, and provide a reliable connection to downstream equipment.