Labeling: Mark polarity, string IDs, and maximum operating voltage at combiner and disconnect terminations. Bonding: Scrape paint or use dedicated bonding lugs on racking. Correctly sizing these components is a critical step in system design, as explored in How to size fuses and disconnects in PV combiner boxes. Bus Bars: These are conductive metal bars that aggregate the current from all the individual strings into a single output circuit. Typical system voltages are 600–1500 Vdc. Before any maintenance work on the inverter or DC wiring, the technician rotates the isolator to the OFF position, safely de-energising the DC circuit between the array. The clear layout helps to confirm the number of string groups, fuse or circuit breaker configuration, surge protector (SPD) location, rated parameters of disconnect switches, cable inlet design, and inverter connection logic before the procurement process is advanced. The output device is normally placed after the strings have been combined: In some designs, both positive and negative output conductors pass through a two-pole or four-pole DC.
