The combiner box serves as the “nerve center” for the DC side of a solar system, ensuring stability, safety, and data visibility. Current Collection and Transmission A standard combiner box supports 6–24 PV string inputs, with typical current per string ranging from 10–20A. Key. PV arrays generate direct current. You will see how each device works, where it fits, and how to select ratings that align. Photovoltaic combiner boxes play a critical role in solar energy systems, acting as the nerve center for current management. The working principle of combiner. ABB offers a plug & play solution that accommodates overcurrent protection devices, disconnectors and surge protective devices (SPDs) in one solar combiner box.