Noelex has it. We consider the source of the power when protecting wires. With one panel, the amps are less than the wire can conduct, so no need for a fuse, even a dead short will not be harmful. With three panels
in parallel, along with a fault in one panel, the other panels
can back-feed with 2 times the amps. Four panels in parallel, 3 times the amps back feed to a short. That may be over-amp for the wire. So with parallel panels, each must have a fuse to protect from that problem. It is helpful to have a switch to disconnect the panels from the controller. I use a DPST battery
disconnect to do the panels and battery
with one turn.
I leave you on your own as for ratings of fuses/breakers or anything designed on your system, but, please do have fuses
at the battery positive. Mainsail
has an article about voltage drop on wires, fuses
, and connections. Worthwhile to read.