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michaelvh asked

Fronius Symo 5.0-3-M DC power drop and voltage spike on one string

Not a Victron but a Fronius specific question, but I have started monitoring 4 separate strings of 2 Fronius inverters trough node-red in the GX. The system gives no errors and works but I started worrying about this.

I just observed that in the largest of 4 strings (very asymmetric layout), when the light gets low in the mornings or evenings, or on a very cloudy day, as soon as that string goes below 350Watts, it drops power intermittently and i see some voltage fluctuations as well, see image. Not sure which happens first.

This never happens at higher power levels, where is is most of the time. The DC voltages are within spec of the inverter but still... anyone knows why this happens? The other strings don't behave as such, and there are no local cast-over shadows.

I didn't troubleshoot by putting that particular string on another inverter yet but i will.



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klim8skeptic avatar image klim8skeptic ♦ commented ·
Is there some way that the colors of the charts could match each other?
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michaelvh avatar image michaelvh klim8skeptic ♦ commented ·
My bad, that was confusing indeed, i replaced the colors. The two images are the same event just a different timescale. The pink line is the problem. Thanks
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1 Answer
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michaelvh answered ·

An update on this... changed this string over to another identical inverter, but the same problem persists, low light gives fluctuating results.

It is a 7kWp string, this only happens below 350Watts of power, still have no idea why. The other strings do not behave as such.

Checked all cabling and it looks fine. When i have time to get on the roof i will split up the string to isolate maybe a bad MC4-connector or panel? Any advice welcome. Or am i worried about nothing here?screenshot-2022-11-28-at-123007.png

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