It's fortunate that you have two charge controllers, which makes troubleshooting easier. If there is a solid ground fault, it should be easy to track down. Assuming that it is intermittent, you can start to do things like swap which PV input goes to which charge controller. Then see if the fault stays with the charge controller or if it switches to the other one, which will tell you if the issue is with the PV or with that charge controller itself. If its in the PV, then you can swap strings around until you can figure out which one has the fault. Also, as Mac mentioned, a visual inspection of the array may give a quick answer.
Cheers, Dave On Sun, Jan 19, 2025 at 3:29 PM jay via RE-wrenches < re-wrenches@lists.re-wrenches.org> wrote: > HI Kent, > > Thanks for that info. > Makes sense > > jay > > On Jan 19, 2025, at 12:47 PM, Kent via RE-wrenches < > re-wrenches@lists.re-wrenches.org> wrote: > > Jay, > > If there is a PV ground fault, putting a short across the fuse holder may > cause damage by drawing an arc. Use a multimeter to measure voltage across > the fuse holder (should be the same as measuring voltage between PV > negative and ground); if there is no voltage then there probably isn't a PV > ground fault or any ground fault at that time. If there is voltage, then > you need to track it down. It isn't necessarily in the PV array - it could > be a dc load or even in the battery. If the voltage exceeds the battery > voltage, the PV array is the culprit. If you compute the proportion of the > negative to ground voltage to open circuit voltage then apply that > proportion to the number of modules, it should tell you about where to > look. If you have multiple strings, isolate the problem: disconnect all of > the PV negative connections and see which one gives you a solid voltage to > ground. > > Kent Osterberg > Blue Mountain Solar > > > On 1/19/2025 6:57 AM, Jay via RE-wrenches wrote: > > Question about the fuses. > > For testing could you put a short test wire across the ends of the fuse > holder and use a clamp on to test for current? Would it cause any damage? > > Instead of potentially going through lots of fuses? > > Jay > > > > On Jan 19, 2025, at 7:48 AM, Mac Lewis via RE-wrenches > <re-wrenches@lists.re-wrenches.org> <re-wrenches@lists.re-wrenches.org> > wrote: > > > Hello Dana, > > Ground faults are tricky. Here is how I would tackle this on a sunny day: > 1. Visual inspection of array, looking for backsheet, wire damage, broken > glass, critter stuff (nests and bite marks). Look for water intrusion or > evidence that water has been somewhere that it shouldn't. > 2. Visual inspection of all splice boxes, checking for wire insulation > damage, evidence of water intrusion and critter entry. > 3. Probe voltage between +, - and Ground (do this at a string level > initially, and isolate strings and do this at open circuit). Any evidence > of bouncing voltage readings, loss of voltage, not rock solid voltage > suggests you may have a ground fault in that string. If its in the string > somewhere, you may see the voltage bounce and read in some fraction of the > string voltage. This can tell you where in the string it may be. FOr > example, if you have a 5 module string, you may get a 3/5 voltage reading > if the fault is near the 3rd module. > 4. Turn off array at combiner and run continuity tests between +, - and > Ground again (no gfp fuse). If you have continuity, this may suggest a > ground fault in conduit run between combiner and FM100. > > Good Luck, bring extra fuses! > > On Sun, Jan 19, 2025 at 7:07 AM Dana Orzel via RE-wrenches < > re-wrenches@lists.re-wrenches.org> wrote: > >> Yes I have 2 FM100s >> Dana Orzel >> C: 208.721.7003 >> E- d...@solarwork.com >> >> On Jan 18, 2025, at 7:08 PM, Kirpal Khalsa via RE-wrenches < >> re-wrenches@lists.re-wrenches.org> wrote: >> >> >> Dana... >> Do you have multiple FM 100s? If so only one should have the GFI fuse. >> Broken panel with water getting into glass? >> Turn it off and wait 5 min and turn it on. Usually clears it especially >> if it's a faulty nuisance trip. >> Have had numerous FM 100s give faulty afci errors. Removing the.afci >> boards always resolved this issue. But of course check all you connections >> leading to and from the cc. >> Keep a few extra 1A gfi fuses handy....you may need a couple to test it >> all out. >> Keep us posted. >> Good luck >> Kirpal >> >> >> On Sat, Jan 18, 2025, 2:40 PM Dana Orzel via RE-wrenches < >> re-wrenches@lists.re-wrenches.org> wrote: >> >>> Hey, all you wise ones, >>> 37 years in the business and I’ve never had a ground fault ever in any >>> installation I’ve done or my home systems. I went out to my system here an >>> hour ago and one FM 100 is completely turned off claiming ground fault on >>> the mate 3S. >>> I guess my first question is : >>> >>> Is this really a ground fault ? >>> >>> I had removed the ground fault breaker when I upgraded due to space >>> considerations >>> >>> In my entire time in this business, I’ve never had to deal with the >>> ground fault any suggestions on how I should be tracing this? >>> >>> Has anybody seen this in an FM 100 when it wasn’t a ground fault? >>> >>> I do own a megger& I’ve never had to use it. I only bought it about >>> three months ago cause it seemed like a good idea and I might need to use >>> one someday, Maybe I’m psychic ? >>> now if I could just figure out how to trace this out. >>> All suggestions welcome thanks all! >>> >>> Dana Orzel >>> C: 208.721.7003 >>> E- d...@solarwork.com >>> _______________________________________________ >>> >> >> _______________________________________________ > 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. 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