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Intermittent DC String Fuses Blown

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APS Solar

Member
Location
Sonora CA
I have a number of older (and newer) string inverter based systems where I use an Outback or Midnite Fused Combiner box as well as string fuses inside inverters (like SMA or Fronius). I always make sure the fuses are sized properly per solar panel specs. I have noticed that over time I will have a blown fuse on one of the strings. I replace the fuse and the system works fine for many years (doesn't re-blow the fuse). I notice this especially on older systems where the customer reports lower system performance. What in your experience causes string fuses to intermittently blow over time?
 
G

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
It is possible that the contact between the fuse and the holder is deteriorating over time, especially if the contact pressure is insufficient. Resistive heating could contribute to the fuse blowing.
 
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