The Combiner Box is an electrical distribution box where the DC circuit breakers are placed. Note that the breakers are usually sold separately. The Combiner Box combines the multiple DC inputs coming from the panel terminations and converts these into one DC output. The output of the combiner box is connected to the charge controller or the inverter, depending on the type of system installed.
In order to choose the correct combiner box, it is necessary to determine the number of strings of solar panels, since a breaker is needed for each string. It is also required to determine the breaker's size that is needed based on the string's current (I) and voltage (V). For example, a system with 4, 100 volt, 10 amp strings requires 4, 125 volt, 20 amp breakers. Even though each string only generates 10 amps of current, a 20 amp breaker would suffice, as a 10 amp breaker may flip too often.
