Dave, No problem. I don't know much about Sonnen, but what I do know is that not all GT inverters do the same impedance test. Outback Power did a bunch of testing and they found one inverter larger than 6 kW that would be able to tell that it could impact the voltage coming from the Radian, and so it could tell that it was not truly the grid. So to be ultra safe, Outback decided to make a cap of 6 kW.
Now I don't know which brand/model inverter above 6 kW that they found that wouldn't work. I don't know if the impedance of the batteries might make a slight difference, and since the Sonnen will only have Lithium batteries with super short cables, perhaps it might be able to trick that one GT inverter, or perhaps, they are less cautious about making sure it will work with every inverter that falls within the rating, or maybe it is something in the software. I don't know. Perhaps, if Outback were doing all their testing with Lithium batteries and super short cables, perhaps they would have rated the Radian to handle larger GT inverters. Thanks, Kienan Maxfield Solar maxfieldso...@hotmail.com<mailto:maxfieldso...@hotmail.com> (801) 631-5584 (Cell) ________________________________ From: RE-wrenches <re-wrenches-boun...@lists.re-wrenches.org> on behalf of Dave Tedeyan <dtede...@taitem.com> Sent: Friday, May 3, 2019 3:05 PM To: RE-wrenches Subject: Re: [RE-wrenches] large(ish) AC coupled battery backup Kienan, Thanks for the info here. That is really interesting about the 6kw limitation. Outback clearly states that limit, but Sonnen has managed to surpass that with their programming of the Radian. The PV part of the system is already existing, so this will need to be AC coupled entirely. I may just aim to AC couple one of the two 11.4kw inverters though. Another slightly complicating factor is that the array is ground mounted and interconnects near the meter which is roughly 100' from the house. Fortunately there is that old service line that I may be able to use to bring power from the solar all the way back to the house. Cheers, Dave Dave Tedeyan, PE Senior Engineer | Taitem Engineering, PC [https://www.taitem.com/signatures/logo.png] 110 South Albany Street | Ithaca, NY 14850 o. 607.277.1118 x121 f. 607.277.2119 www.taitem.com<http://www.taitem.com> Solar • Sustainability • Energy • Design B-Corporation Best for the World 2018 Honoree On Fri, May 3, 2019 at 2:54 PM Kienan Maxfield <maxfieldso...@hotmail.com<mailto:maxfieldso...@hotmail.com>> wrote: Yes, two radians combined can handle one 12 kW grid tied inverter. The 6 kW limitation is not a limitation of how much power the radian can actually handle, it's that the grid tied inverters do an impedance/stability test, and some inverters larger than 6 kW will detect that the inverter is not actually the grid, and the GT inverter will shut down before it even fires up. If it weren't for that, the radian would be able to handle more PV in an AC coupled situation. Is this an all new system? Sometimes, doing a mixture of AC and DC coupling makes the most sense financially if you don't actually need 4 radians worth of backup power. The following setup I'm talking about assumes that you have an external transfer switch, and it's the extreme setup, not necessarily a recommended setup. I just want to demonstrate that you would really only need 2 radians if the required instantaneous backup power needs were low enough. If you do an AC/DC coupled mix, for each Radian, you can actually handle up to 6 kW AC of GT inverter(s), and it can export 7.2 kW AC from the DC coupled side. With a DC/AC ratio of 1.25, that would be 7.5 kW of AC coupled PV and 9 kW of DC coupled PV, so with the right design and external transfer switch, the radian could potentially handle up to 16.25 of PV per inverter. Now you have to tie the AC coupled PV into the load side of the transfer switch (or in the backed up loads panel). This way, if the grid is available, the AC coupled PV is not connected at all to the battery based inverter, but when the power fails, then the PV gets connected to the radian(s) through the transfer switch. Again, I want to stress that it is imperative that with this kind of system, it has to be tied through an automatic external transfer switch, and that you can't have the power flowing to the grid from both the AC and DC coupled PV simultaneously. Hope this is somewhat helpful. Thanks, Kienan Maxfield Solar maxfieldso...@hotmail.com<mailto:maxfieldso...@hotmail.com> (801) 631-5584 (Cell) ________________________________ From: RE-wrenches <re-wrenches-boun...@lists.re-wrenches.org<mailto:re-wrenches-boun...@lists.re-wrenches.org>> on behalf of Dave Tedeyan <dtede...@taitem.com<mailto:dtede...@taitem.com>> Sent: Friday, May 3, 2019 7:43 AM To: RE-wrenches Subject: Re: [RE-wrenches] large(ish) AC coupled battery backup Thanks Darryl, Yea, it used to be two separate 200A services. At some point, someone decided to turn one of those panels into a sub and run it all of a single service. Regarding paralleling Radians, I know that the max solar input when AC coupled is only 6kw for an 8kw inverter. When they are paralleled, does that jump up to a single 12kw input, or are you just limited to two 6kw inputs? Cheers, Dave Dave Tedeyan, PE Senior Engineer | Taitem Engineering, PC [https://www.taitem.com/signatures/logo.png] 110 South Albany Street | Ithaca, NY 14850 o. 607.277.1118 x121 f. 607.277.2119 www.taitem.com<http://www.taitem.com> Solar • Sustainability • Energy • Design B-Corporation Best for the World 2018 Honoree On Fri, May 3, 2019 at 9:27 AM Darryl Thayer <darylsol...@gmail.com<mailto:darylsol...@gmail.com>> wrote: the 2 each 200 Amp panels is to overcome the 42 circuit limit in one panel. must be a big house. This sounds like a whole house backup. you will need a transfer switch much like a whole house generator switch unless your customer needs TOU or some other grid service. For the AC coupled paralleled Radians or XW6848 and have a turn off for one or both of the SB inverters based on battery voltage (SOC). On Fri, May 3, 2019 at 7:58 AM Dave Tedeyan <dtede...@taitem.com<mailto:dtede...@taitem.com>> wrote: Hi All, Does anyone have a good recommendation for an AC coupled energy storage solution for someone who has a 27.6kw array with two SE11400A-US inverters? The output of one of those inverters is more than a Sonnen or Radian can handle (which is what I am most familiar with). I am not sure yet whether this will be a whole home backup or just a subset of their loads, but they have two 200A panels on a single 200A service. Thanks, Dave Dave Tedeyan, PE Senior Engineer | Taitem Engineering, PC [https://www.taitem.com/signatures/logo.png] 110 South Albany Street | Ithaca, NY 14850 o. 607.277.1118 x121 f. 607.277.2119 www.taitem.com<http://www.taitem.com> Solar • Sustainability • Energy • Design B-Corporation Best for the World 2018 Honoree _______________________________________________ List sponsored by Redwood Alliance List Address: RE-wrenches@lists.re-wrenches.org<mailto: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<http://www.re-wrenches.org/etiquette.htm> Check out or update participant bios: www.members.re-wrenches.org<http://www.members.re-wrenches.org> _______________________________________________ List sponsored by Redwood Alliance List Address: RE-wrenches@lists.re-wrenches.org<mailto: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<http://www.re-wrenches.org/etiquette.htm> Check out or update participant bios: www.members.re-wrenches.org<http://www.members.re-wrenches.org> _______________________________________________ List sponsored by Redwood Alliance List Address: RE-wrenches@lists.re-wrenches.org<mailto: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<http://www.re-wrenches.org/etiquette.htm> Check out or update participant bios: www.members.re-wrenches.org<http://www.members.re-wrenches.org>
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