Solar PV system DC fuse keeps blowing

solarroxsolarrox Registered Users Posts: 1 ✭
in PV Installers Forum - NEC, Wiring, Installation #1

Hi!


I have a 6.5Kw system installed with a SMA Sunnyboy inverter. Works great normally. One DC fuse blew 2 years ago and I replaced. However, it blew again repeatedly every 6 months. There are four DC fuses and this particular one keeps blowing. Any idea why this is happening?


I am not a Pro.

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  • PhotowhitPhotowhit Solar Expert Posts: 5,567 ✭✭✭✭✭
    #2
    So, I'm guessing these are fuses for the incoming solar panels, perhaps someone with a dc clamp meter could check to see if the current coming in from each string is even...

    Perhaps they wired your panels incorrectly. Do you have panels in a multiple of 4? maybe 28 panels which would be strings of 7 panels...
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • PhotowhitPhotowhit Solar Expert Posts: 5,567 ✭✭✭✭✭
    #3
    Alternately, you might shut everything down and read the voltage coming in on each fused string one at a time. Or at least do the one that keeps blowing and another to get a comparison. The fuses are rated for amps, which shouldn't change regardless of how many panels are in a string. but they could be past the max voltage with additional panels.

    What mightbe happening is a bad connection internally, if the string is plugged into the inverter near the fuse and the connection is a bit loose or other connections are loose, the added heat will run along the line and may trip burn the fuse.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • BB.BB. Super Moderators, Administrators Posts: 31,647 admin
    #4
    What size or amp rating of fuse?

    Around 1 amp is s ground fault detection fuse.

    Most arrays, if you have any fuses, are around 15 amps or so.

    Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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