That document refers to 2008 NEC 690.9 code which has the exemption that is used for grounded inverters. Section 690.35 for ungrounded systems just refers back to 690.9 for over-current protection. So I do not see any indication that two strings on an ungrounded inverter could not have the same exemption applied to it, which I think is largely standard practice with a few AHJ's not accepting it. There was nothing that I saw in the document that would indicate otherwise.
Brad On Fri, Jan 29, 2016 at 11:34 PM, <d...@energysolarnow.com> wrote: > Hi Jay- > Here is a somewhat dated Engineering Bulletin from Solar World with nice > diagrams. > > Mark- > NEC requires transformerless inverters to be handled differently than the > ones with transformers. > Neither DC+ or DC- is grounded, so there no ground fault fuse inside the > inverter. > Both DC+ and DC- are fused external to the inverter. > Both DC+ and DC- are switched by the DC Disconnect. > PV wire is required to better ensure against ground faults since they > become so catastrophic. > > Don Barch > Energy Solar > > Jay <jay.pe...@gmail.com> wrote: > > > >Hi Dan > > > >Can you provide any documentation on this? > > > >Thanks Jay > >Peltz power. > > >"Mark Byington" <ma...@cobaltpower.com> wrote: > > > >"Transformerless inverters need fuses on both DC positive and DC negative > >legs to protect the inverter in case of ground fault." > > > > > >I could be wrong, but my understanding is that TL inverters are no > different > >than transformer type inverters in terms of DC fusing requirements - no > fuse > >required for one or two strings in parallel; fuses required on + and - > leads > >for 3 or more strings in parallel. > > > > > >Mark Byington > > > >Cobalt Power Systems, Inc > > _______________________________________________ > 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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