Solar

Solar Combiner Box Size Calculator

Estimate the required solar combiner box current rating from string current and the number of parallel PV strings.

Solar Array

Number of Parallel Strings

String Short-Circuit Current (Isc)

For a string made from identical panels in series, string Isc is approximately equal to the Isc of one panel.

Combiner Output

Main Output Cable Current Rating

Enter the allowable current rating of the cable leaving the combiner box.

Recommended Combiner Rating

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Total Array Isc —

Minimum Design Current —

Required String Inputs —

Main Cable Rating —

How it is calculated: Total array short-circuit current = string Isc × number of parallel strings. A 125% design factor is then applied to the combined short-circuit current to provide a practical minimum combiner output-current estimate. The result is rounded up to the next common combiner current rating. The output cable current rating should be equal to or greater than the calculated design current. Final PV protection, conductor sizing, fuse requirements, enclosure rating and equipment selection must follow the applicable electrical code and manufacturer requirements.