Hi William - Check out the Solarpro Magazine archive May/June 2017 issue page 34: it addresses "functional grounded PV systems."
https://docs.wixstatic.com/ugd/d49ff9_ccc99efe7b344f6a945ca2e00f8a71d8.pdf And the definition found in 2017 NEC 690.2: [image: image.png] Yes, the normally grounded white conductor might be hot during a fault condition. Is it safe? Well, it's not that great of a setup but I think it's the lesser of all evils constrained by the relatively old school inverter technology. I'm a huge believer in the benefits in the new high voltage batteries such as the LG Chem product that can be wired up with #10s and have integrated safety features built in to the battery enclosure. Surely this must be the future. To answer your question, we do almost all grid tied systems up here in the San Francisco Bay Area. We've been installing the Tesla Powerwall 2 with about 50% of our PV systems - it's been a widely popular product. Historically, we installed a few Sunny Island AC coupled (and a few Outback and Schneider XW) systems annually. August Luminalt On Tue, Jul 23, 2019 at 10:22 AM William Miller <will...@millersolar.com> wrote: > August: > > I read the referenced report. It does not address the concern I raised— > that is the breaker specified unbonds a system that I believe is supposed > to be bonded. > > William > > On Jul 23, 2019, at 8:38 AM, August Goers <aug...@luminalt.com> wrote: > > Hi William - > > This article is a few years old, but I think describes ground fault > detection issues well: > http://www.solarabcs.org/about/publications/reports/blindspot/pdfs/inverter_groundfault-2013.pdf > > > I don't have experience (at least since the late 90s) with the type of GFD > breaker you describe on the DC-side PV circuit. We switched to AC coupled > systems with standard grid tied inverters (transformerless non-isolated) > years ago. What kind of setup are you referring to? > > Best, > > August > > Luminalt > > > > On Mon, Jul 22, 2019 at 1:42 PM William Miller <will...@millersolar.com> > wrote: > >> Wrenches: >> >> >> >> Here is a question that has bothered me for some time: If one is using a >> GFD (ground fault detection) breaker on a PV feeder(s) to a battery >> inverter system, the state of the industry is to use a breaker with an >> extra 0.5 or 1 amp pole. This section of the breaker connects, or bonds >> the DC negative, or grounded conductor, to the grounding system. >> >> >> >> In order for the GFD breaker to work one needs to isolate the grounded >> bus bar (negative). If there is a ground fault the breaker opens and >> breaks the bond. >> >> >> >> This goes very much against my conceptualization of how a bonding system >> should work. The bond should never be broken, particularly when there is a >> fault in the system. When this breaker opens, either manually or by an >> overcurrent condition on any pole, the DC bond is removed for all portions >> of the DC system. >> >> >> >> There is a prominent personality in the industry that often presents >> academic opinions on solar related electrical issues in articles and in >> seminars. This person claimed to have invented this GFD system, but when >> pressed to comment on the concerns mentioned above, changed the subject. >> >> >> >> I believe ground fault protection is important. I just don’t believe the >> method the industry has offered is really effective in solving the issues >> presented in a ground fault scenario. >> >> >> >> I believe similar issues present on non-battery PV systems with the >> simple fuse in the ground system found on many inverters. I know some >> troubleshooting guides warn of energized parts in ground fault conditions. >> >> >> >> Have any of you thought about these concerns? Are my concerns valid? >> What are your policies on this subject? >> >> >> >> Thanks in advance for any insight. >> >> >> >> William Miller >> >> >> >> Miller Solar >> >> 17395 Oak Road, Atascadero, CA 93422 >> >> 805-438-5600 >> >> www.millersolar.com >> >> CA Lic. 773985 >> >> >> >> Quote of the month: “As they age, batteries transition from energy >> >> storage devices to energy consuming devices.“ W. Miller >> >> >> _______________________________________________ >> List sponsored by Redwood Alliance >> >> 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 >> >> List-Archive: >> http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html >> >> List rules & etiquette: >> www.re-wrenches.org/etiquette.htm >> >> Check out or update participant bios: >> www.members.re-wrenches.org >> >>
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