PV-source circuits route from the array through combiners (on medium and large systems) and then on to the DC PV disconnect. Normally, two strings of modules can be connected in parallel without requiring a combiner containing overcurrent devices—see NEC Section 690.9(A)
EX. Batteryless grid-tied PV systems rated above 6 kW may be configured with more than two strings. Since rated voltages range widely and module power ratings can vary
from 40 to 300 W, there are no hard-and-fast rules relating
the need for a DC combiner to a specific number of modules in an array. If more than two strings are needed, then overcurrent protection on each string may be required and
these overcurrent devices are placed in a PV source-circuit combiner (see Code Corner in HP125).