I have this exact same question. This is critically important to understand the mechanism involved to prevent backfeed.
Jason Szumlanski Principal Solar Designer | Florida Solar Design Group NABCEP Certified Solar Professional (PVIP) Florida State Certified Solar Contractor CVC56956 Florida Certified Electrical Contractor EC13013208 On Thu, Jun 26, 2025, 8:44 AM Lou Russo <l...@spreesolarsystems.com> wrote: > Aloha All, > > Thank you Sue for the detailed explanation of the self-consumption and > off-grid operating modes of the AIO. > We have a follow-up question regarding the off-grid mode operation that > we'd like to clarify : > > In off-grid mode, what specific mechanical or electrical mechanisms > absolutely prevent any export to the grid side? Yet (if I understand your > email correctly), still allows for grid passthrough. > > This information will help us when speaking with AHJs and utility > engineers who need to understand the export prevention safeguards for > permitting and interconnection approval, plus I am just super interested in > how it works! > > Thank you! > > Aloha, > Lou Russo > Spree Solar Systems LLC > C-34322 > > > > > > > On Thu, Jun 26, 2025 at 1:47 AM Sue Stankevitz via RE-wrenches < > re-wrenches@lists.re-wrenches.org> wrote: > >> In a self-consumption style situation an inverter sells to drop the usage >> to close to 0 watts. It’s a controlled sell as not to export. The inverter >> “buys” power from the grid at a low rate to power the first 200w or so of >> the load. This is designed to prevent accidental selling during large load >> fluctuations but is not an absolute guarantee against very small very short >> duration sells. >> >> >> >> In Off Grid mode it does not sell it just makes power on the AC Out side. >> Similar to what you may be familiar with in the old Outback or Magnum >> inverters. If the AC in is present it passes through and runs the loads if >> its not present the inverter powers the loads. >> >> >> To complement this for a self use style system you run the grid into the >> Generator in not AC in and program the generator to start and stop at your >> desired levels and then the AIO will ignore the grid when the battery is >> above your programmed set points similar to the Rosie in VDC >> disconnect/connect >> >> >> >> Sue Stankevitz >> MidNite Solar, Inc. <https://www.midnitesolar.com/index.php> >> (360) 403-7207 (XT122) >> >> >> >> *From:* Jason Szumlanski <ja...@floridasolardesigngroup.com> >> *Sent:* Wednesday, June 25, 2025 12:12 PM >> *To:* Sue Stankevitz <s...@midnitesolar.com> >> *Cc:* RE-wrenches <re-wrenches@lists.re-wrenches.org> >> *Subject:* Re: [RE-wrenches] Truly Zero Export >> >> >> >> Thanks, Sue. Your response is greatly appreciated. >> >> >> >> Can I ask how the Midnite AIO accomplishes this in Off-Grid mode? Does >> the inverter turn off grid-passthrough to the loads altogether and just >> offer grid voltage to the charger while inverting power from the batteries >> and solar to cover the loads? How does the inverter definitively "catch" >> excess solar production when a large load is dropped? >> >> >> I believe what you are saying is true, but I am interested in the >> mechanics behind this. I would like to share it with our local electric >> co-op's chief engineer. They are raising red flags with the local AHJ for >> homes that install solar panels that don't net meter, even if there is no >> intention of net metering. >> >> >> >> >> Jason Szumlanski >> >> Principal Solar Designer | Florida Solar Design Group >> NABCEP Certified Solar Professional (PVIP) >> Florida State Certified Solar Contractor CVC56956 >> >> Florida Certified Electrical Contractor EC13013208 >> >> >> >> >> >> On Wed, Jun 25, 2025 at 11:48 AM Sue Stankevitz <s...@midnitesolar.com> >> wrote: >> >> For the MidNite MN15-12K-AIO it has 2 modes that pertain to this >> discussion >> >> >> >> Off Grid mode will never export out the input terminals at all no matter >> what >> >> Self Consumption will export out the input terminals to the Main Panel to >> try and zero the CT’s out. We have a setting you can adjust that will >> always draw this amount first from the grid to give the inverter some room >> to catch the over shoots when loads turn off. We find around 200 Watts is >> generally a good spot. >> >> >> >> For the MidNite MNROSIE7048RE it has 2 modes as well >> >> Grid Support- This allows Rosie to try and zero the incoming power from >> the grid any time the battery is above a set point you select. Rosie will >> always draw the first 150-200 watts from the grid to allow it to catch the >> over shoots when a load goes away >> >> VDC Connect / Disconnect- This mode allows Rosie to open its relay any >> time the battery is above a value you select eliminating ANY possibility of >> over shoot when loads go away. >> >> >> >> If you are working with a municipality where there is absolutely zero >> room for error it is best practice to use the more conservative approach of >> Off Grid Mode or VDC Connect/Disconnect to insure there will never be a >> chance of export however slim or minior. >> >> Sue Stankevitz >> MidNite Solar, Inc. <https://www.midnitesolar.com/index.php> >> (360) 403-7207 (XT122) >> >> >> >> *From:* RE-wrenches <re-wrenches-boun...@lists.re-wrenches.org> *On >> Behalf Of *Jason Szumlanski via RE-wrenches >> *Sent:* Wednesday, June 25, 2025 2:59 AM >> *To:* RE-wrenches <re-wrenches@lists.re-wrenches.org> >> *Cc:* Jason Szumlanski <ja...@floridasolardesigngroup.com> >> *Subject:* [RE-wrenches] Truly Zero Export >> >> >> >> We've had issues with Enphase systems "leaking" electricity back to the >> utility grid despite being in a no export grid profile. A local utility >> company gets all bent out of shape if there is even a watt-hour of reverse >> meter feed in detected. I understand why it isn't feasible to completely >> prevent this with Enphase's system architecture, even with a sizeable >> battery. >> >> >> >> Off-grid inverters that can't interact with the grid will obviously >> provide no export. >> >> >> >> My question is about hybrid inverters that are capable of grid sell, but >> programmed not to sell. Are they capable of truly Zero Export? >> >> >> >> The AIOs with grid pass-through don't seem likely to prevent reverse >> current flow, but I could be wrong. I'm not sure I would trust Sol-Ark to >> stop grid sell completely. Midnite AIO isn't well enough documented to >> understand how off grid mode works. The EG4 18Kpv has some cryptic settings >> that seem to imply it has truly a off grid mode, but I'm not sure how that >> works, either. >> >> >> >> If not AIOs, what about other system architectures? I find it hard to >> believe that a Powerwall 3 could operate in a non-grid-interactive manner. >> After all, it doesn't even support fully off-grid operation. An EG4 >> FlexBoss/GridBoss setup would naturally rely on current transformers to >> prevent grid export, which is a deal breaker I would think in any method to >> prevent grid selling. Other AC Coupled solutions like Franklin seemingly >> have no chance of preventing export entirely. >> >> >> >> It seems the only way for true no export to work is to invert battery >> power at all times, meaning no grid pass-through and no AC Coupling. The >> inverter/charger need to operate simply as a load from the grid >> perspective. Can any grid interactive inverter system programmatically >> change its mode entirely to prevent grid selling? >> >> >> >> >> >> Jason Szumlanski >> >> Florida Solar Design Group >> >> >> >> _______________________________________________ >> 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. When one doesn't work, try the >> other: >> https://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/ >> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org >> >> List rules & etiquette: >> http://www.re-wrenches.org/etiquette.htm >> >> Check out or update participant bios: >> http://www.members.re-wrenches.org >> >>
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