One time I had similar, but different problem: 1 Amp ground fault fuse consistently blowing, sometimes after 1 day sometimes after weeks/months. I tried everything - replaced home runs, checked VOC, VMP, swapped DC input into a different inverter, etc. it kept coming back to this one string. I checked every module VOC, ISC, every connection, no pinched wires, no discernible problem, but fuse blowing. Luckily it was a medium size commercial job (on a fire station) so I was able to scatter all the modules of this suspect string all over the roof, and carefully track where I had put them. That’s when the problem went away and never came back..😂 Best I could figure was a slight manufacturing error that had a compounding/cumulative effect. So once I got those consecutive serial numbers away from each other no more problem. Either that or the fire chief was fucking with me and he was burning out the fuses, which I doubt
On Fri, Apr 11, 2025 at 8:05 AM Mac Lewis via RE-wrenches < re-wrenches@lists.re-wrenches.org> wrote: > Hello Amos, > > Have you checked for voltage imbalance for each string? If you have a bad > diode, that string may run low on voltage and be trying to send current > toward the weak string (this is the reason you have these breakers). I'd > run each string independently and see what Vmp is. If you are missing some > voltage that may be a clue. You can also independently clamp each string > during operation. > > I like IR cameras for this type of thing. It may just be a bad > connection, heat build up, fuse holder issue. > > Let us know what you find out > > On Fri, Apr 11, 2025 at 8:07 AM Amos Post via RE-wrenches < > re-wrenches@lists.re-wrenches.org> wrote: > >> Hi Wrenches, >> >> I have a bit of a puzzler that I’m trying to get sorted out. I’ve been >> servicing a Grid-Tied Battery Backup system that’s about 17-18 years old. >> The system comprises of 2-GVFX3648s in series, with 2-MX60(at least I think >> they are 60s) CC’s. Each CC has 3 strings of 3 tied to it, and each string >> has a 15A in-line 600V fuse. The modules are I believe are like >> 230/240Watt 60 cell modules (sorry I don’t have pictures/specifics). We >> replaced the flooded batteries with AGMs about a year and a half ago. >> >> The situation is one of the 15A string fuses keeps blowing. It’s now >> happened 3 times and its the same fuse every time. First we just replaced >> the fuse and under the surge/lightning assumption. Fuse blew again. Then >> I thought I found the culprit. The #6 PV output from the combiner to the >> PV input breaker for the CC was a bit darkened and very warm to the touch >> when I replaced the fuse the first time. So I though maybe it was a loose >> connection on that lug and that caused everything to heat up and eventually >> blow the fuse. I cut and stripped the wire back and cleaned the lug and >> re-seated the wire in the lug. Fuse blew again within a few months time. >> I then checked the Junction box on the roof where the USE-2 wire connects >> to THHN, and did a visual inspection of all the wiring on the roof. All of >> the Jbox connections and everything on the roof “looked” ok. I have also >> check all of the connections inside the Outback DC load center, and they >> look ok. Fuse replaced 3rd time and then it blew again. >> >> Before I take all of the panels off the rack, check panels, re-check >> string wiring on the roof, is there anything else I should be checking? >> Seems like that warm wire in the Combiner box is telling me something but I >> can’t figure out what...I believe this is a new problem in the last 2-3 >> years but we are not 100% sure when the problem first came up… >> >> As always, thanks for your help/ suggestions! >> Amos >> >> >> >> >> Amos Post >> Integrity Energy >> W 802.763.7023 >> C 802.291.2188 >> ienergyVT.com <http://www.ienergyvt.com> >> Facebook <https://www.facebook.com/integrityenergyllp?ref=hl> >> >> _______________________________________________ >> List sponsored by Redwood Alliance >> >> Pay optional member dues here: http://re-wrenches.org >> >> List Address: RE-wrenches@lists.re-wrenches.org >> >> Change listserver email address & settings: >> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org >> >> There are two list archives for searching. When one doesn't work, try the >> other: >> https://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/ >> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org >> >> List rules & etiquette: >> http://www.re-wrenches.org/etiquette.htm >> >> Check out or update participant bios: >> http://www.members.re-wrenches.org >> >> > > -- > > > > Mac Lewis > > *"Yo solo sé que no sé nada." -Sócrates* > _______________________________________________ > List sponsored by Redwood Alliance > > Pay optional member dues here: http://re-wrenches.org > > List Address: RE-wrenches@lists.re-wrenches.org > > Change listserver email address & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > There are two list archives for searching. When one doesn't work, try the > other: > https://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/ > http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org > > List rules & etiquette: > http://www.re-wrenches.org/etiquette.htm > > Check out or update participant bios: > http://www.members.re-wrenches.org > >
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