Combiner Boxes are typically used to combine several strings of solar PV panels together at one connecting point allowing direct DC feed to the solar charge controller. The combiner box should be selected based on the amount of strings of solar panels (circuits) used in your project. Once the box is selected please choose the required protection device, either fuse or circuit breaker depending upon your needs. Please note whenever selecting the protection device be sure that it is grater than the maximum voltage rating of your PV circuit.