If you're in Sebastopol you could ask Paul Hernday at Solmetric if the PVA would help.
Blessings, Kelly On Nov 26, 2012, at 4:55 PM, Robert Nuese wrote: > Dear Wrenches > > I've been experiencing a troubleshooting problem that you may be able to > help me with. Or, can anyone refer me to someone, maybe an electrical > engineer?, who I could hire to help. > > About 7 years ago I installed Unisolar modules on all the roofs of a complex > of 12 mixed use buildings and one commercial building. These fed the > grid through a variety of Fronius IG and SMA SunnyBoy inverters. > > Ever since, we have had occasional intermittent ground faults on a few of > the roofs, and more frequent ones on one roof. At least some of these I > suspect were caused by the roofer. Standard procedure on the Unisolar > modules is to put two screws through them that hold on the roof ridge > z-strip metal closure piece. These also keep the modules from sliding off > the roof in extreme hot weather. I found a number of screws placed > slightly outside the allowed screw zone. After I'd moved the screws > (and removed the raised metal edges the screws had made in the roof, > and put insulation between roof and module in those locations), this has > seemed to fix some problems. Similarly, putting tefzel patches, per Uni- > solar instructions, on some big dings and scratches may have fixed some > others. > > However, I still occasionally, rather rarely, get ground fault indications > on some inverters, and rather regularly get them on one specific IG 3000. > Some times the indication is just in the software, and the problem disappears > through resetting by disconnecting the inverter and reconnecting to reset the > software. However, on that worst Fronius, it has usually blown the 1 amp > ground fault fuse, indicating that there very likely has been a ground fault. > > I suspect that these ground faults are brought on by thermal expansion and > contraction, that may only occasionally, and briefly, bring hot and ground > elements of the system into close enough proximity. Dampness seems to > play a part, the ground faults almost always occur during the rainy season, > and usually during a rainy period. > > But whenever I get out to the site to test the system, the ground fault is > always gone. I test by disconnecting both wires of each string, measuring > the total voltage across, and then the voltage from each to ground. If there > is a clear voltage to ground, then there is a ground fault, and its location > in > the string can be easily determined. If the voltage steadily goes toward > zero, then a ground fault is not clearly present, and the location of where > one had been is totally obscure. > > I've done very thorough visual inspection of the roofs, and also of the > disconnects, junction boxes, and gutters that the wires pass through. > As mentioned, the modules have had some problems, and I've fixed them > all, as well as can be done. The wires all seem fine. Well connected, neat, > not close to raw metal edges, insulation ok, etc. > > I've asked Unisolar (before they went bankrupt, now they don't answer the > phones), and they've just recommended the testing I've done, and not had > any other ideas. Same with Fronius - they think it's outside of the inverter, > and the blown fuses support that position. > > I could go on with more details about what I've done and thought about, > for instance, is the Fronius too sensitive? But I'll catch my breath and see > if anyone else has some input before I go into more detail. > > SO what am I missing? What test should I do? How can I fix this problem? > > OR does anyone know of somebody with more expertise who I could hire > to help? I'm a fairly experienced solar installer, but I think this might be > something that requires an electrical (or electronic?) engineer with a deep > understanding of electrical theory, and with some advanced test equipment. > Any recommendations? Probably needs to be someone within 100 miles of > Sebastopol CA. > > Thanks, > Robert Nuese > > > > > > > _______________________________________________ > List sponsored by Home Power magazine > > List Address: [email protected] > > Options & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: > http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out participant bios: > www.members.re-wrenches.org >
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