Wire sizing requirements are based on the ampacity (current carrying capacity) of conductors. The NEC includes Ampacity Tables which are used to determine the ampacity for a given wire size as indicated in NEC Section 310.15.
GenStar power terminals are rated for 75°C. When wires with a 90°C temperature rating are used with terminals that have a 75°C temperature rating, wire ampacity at 75°C must be used.
Wire ampacity requirements for the battery, PV array and load circuits are:
Controller battery wire ampacity must be greater than or equal to 125% of maximum continuous current (battery current rating of the controller)
PV array wire ampacity must meet both of the following requirements:
Must be greater than or equal to 156% of PV Array Isc without correction and adjustment factors.
Must be greater than or equal to 125% of PV Array Isc with correction and adjustment factors.
Load wire ampacity must be greater than or equal to the load breaker current rating.
NEC Section 240.4(D) requires a maximum breaker or fuse rating for smaller wire sizes as follows:
14 AWG Copper: 15 Amps OCPD and wire ampacity
12 AWG Copper: 20 Amps OCPD and wire ampacity
10 AWG Copper: 30 Amps OCPD and wire ampacity
Therefore, where load circuit-breakers or fuses are larger than indicated above, a larger wire must be used.
Correction and adjustment factors may also be required to account for the following:
Maximum ambient temperature
Temperatures at different parts of the circuit (rooftops or engine rooms for example)
Wire terminal temperature ratings
Multi-conductor cables
Conduit fill and other factors