Throwback Thursday! (Monday)


Senior Member
Just a reminder that yes, there are still people that think two PV strings in parallel require fusing.

So, if you're one of the good ones that decided to research before digging your heels in you came to the right place! Enter 'string fusing' in the search box and see why this isn't needed.

Forum mods - if you know of a great thread on this consider making it a sticky:)


Watson, LA, USA
My responsibility is to maintain a 50mw solar plant. I assure from this experience evidence proves paralleled strings should be fused. Example, lightning struck a string then voc measured 875 volts positive to ground for a nominal 1150 volts voc. Putting an amp clamp on the positive string wire then installing a new 15 amp fuse the amp clamp meter would read 26 amps with a reverse polarity than expected for moments then blow the fuse even while combiner box was off. This single failed string is paralleled with another 17 strings. The fuse protects remaining good pv modules within this failed string from being further damaged effectively by role reversal from intended generating source to a load. Similar to a battery bank with weak batteries.