The design relies on a relay relaxing upon *loss* of grid voltage. This is fail-safe.
Furthermore, Enphase can be configured to send an email if production is lost so if the system fails as it should, in the no-production state, someone gets notified. William Miller Miller Solar.com 805-438-5600 www.millersolar.com On Tue, Jan 27, 2026 at 9:17 AM Jason Szumlanski via RE-wrenches < [email protected]> wrote: > I don't like to install anything that isn't failsafe for this purpose, so > if it relies on a NC relay opening upon receiving generator voltage, I > usually won't consider it because the relay can fail. And if the > relay fails, there is no indication of that (other than the adverse effects > that might happen). > > That's just my opinion, but I can understand fringe scenarios where there > just isn't a way to get the solar connected on the line side. As long as > the customer signs off on the risks, I would do it, but cautiously. > > > 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 Mon, Jan 26, 2026 at 4:41 PM Howard Scot Arey via RE-wrenches < > [email protected]> wrote: > >> Interesting. Somebody else recommended a web-based version of what you >> did. You were ahead of the times. I might pursue this with the web >> option...not the radios. Same concept - different technology. >> >> Thank you. >> >> *Howard "Scot" Arey* >> *Owner, Solar CenTex* >> >> NABCEP PV Installation Professional >> TECL 29755 >> 254-300-1228 >> >> ------------------------------ >> *From:* William Miller <[email protected]> >> *Sent:* Monday, January 26, 2026 3:28:04 PM >> *To:* RE-wrenches <[email protected]> >> *Cc:* [email protected] <[email protected]> >> *Subject:* RE: [RE-wrenches] Will IQ8 microinverters backfeed a >> generator during grid interruptions >> >> Friends: >> >> >> >> I had the same problem: Enphase arrays on an outbuilding which was >> connected to the generator side of a transfer switch. I had no independent >> power path from the grid to the outbuilding so the Enphase had to be >> connected to the load side of the transfer switch. When the large >> generator was powering the facility and the sun was out the generator acted >> wonky (unstable voltage). >> >> >> >> My solution was to buy a transceiver set (National Control Devices >> MlrXR2x). I powered one radio from the grid side of the transfer switch >> and the other radio controlled a contactor on the remote Enphase feeders. >> When the grid goes down the contactor opens. >> >> >> >> The radios were inside of two buildings and the reception was >> borderline. I augmented the included 900 mHz rubber duckies by replacing >> them with panel antennas from Pasternak. So far the system is operating as >> intended. >> >> >> >> If anyone wants details let me know. >> >> >> >> William >> >> >> >> William Miller >> >> Miller Solar >> >> www.millersolar.com >> >> CA License C-10 77398 >> >> >> >> *From:* RE-wrenches [mailto:[email protected]] *On >> Behalf Of *scot.arey--- via RE-wrenches >> *Sent:* Wednesday, January 21, 2026 12:45 PM >> *To:* RE-wrenches >> *Cc:* [email protected] >> *Subject:* Re: [RE-wrenches] Will IQ8 microinverters backfeed a >> generator during grid interruptions >> >> >> >> Thanks but I'm just trying to grid-tie a small Enphase array without ESS >> where the point of interconnection is on the customer side of the >> generator/ATS. >> >> Trying to use existing wires in place to simplify and lower costs...but >> the generator is my constraint because I need the PoI to be on line side of >> the ATS. >> >> >> >> *Howard "Scot" Arey* >> >> *Owner, Solar CenTex* >> >> 254-300-1228 >> >> >> ------------------------------ >> >> *From:* RE-wrenches <[email protected]> on >> behalf of Jason Szumlanski via RE-wrenches < >> [email protected]> >> *Sent:* Wednesday, January 21, 2026 2:33 PM >> *To:* RE-wrenches <[email protected]> >> *Cc:* Jason Szumlanski <[email protected]> >> *Subject:* Re: [RE-wrenches] Will IQ8 microinverters backfeed a >> generator during grid interruptions >> >> >> >> I should have also noted that Enphase DOES allow use of a generator with >> its System Controller 3G, and supposedly the inverter, battery, and >> generator sources can all power loads simultaneously, so I could be wrong >> about how the IQ8s work. That said, Enphase has strict pairing >> specifications and an approved generator list. They seem confident in their >> ability to limit backfeed to the generator in this scenario. >> >> >> >> 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, Jan 21, 2026 at 3:16 PM William Bryce via RE-wrenches < >> [email protected]> wrote: >> >> If the AC coupled exported energy is more than the generator produced >> energy, it can destroy the generator controller. >> >> That is why most AIO inverters have a relay on the dedicated AC coupling >> input. It will open the relay if the inverter sees generator power. >> >> >> >> The MNP AIO will allow both inputs, but will open the relay if the AC >> coupled power increases to 20% of the Generator input (firmware dependent). >> >> >> >> >> >> On Wed, Jan 21, 2026 at 2:27 PM Jason Szumlanski via RE-wrenches < >> [email protected]> wrote: >> >> Enphase IQ8 microinverters will absolutely leak some power back to the >> grid when set to a no-export grid profile. How much, and if that is >> detrimental to the generator is another question. I suspect if the >> generator is large enough relative to the PV array, the impact will be nil, >> but I would not take the risk. >> >> >> >> I don't think the fast switching really does the trick in terms of not >> exporting. That function relies on the consumption CTs connected to the >> Gateway, which in turn communicates with the microinverters. Aside from the >> CTs not being totally accurate, I don't see how that communication loop >> could be fast enough. >> >> >> >> 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, Jan 21, 2026 at 12:09 PM scot.arey--- via RE-wrenches < >> [email protected]> wrote: >> >> Good day, >> >> >> >> I many years ago watched the fast-switching capabilities of the IQ-8 >> microinverters to produce only what demanded of the MI, and wondered if it >> might have application in a grid-tied system that is served by a >> whole-house generator. >> >> >> >> We have the opportunity to install grid-tied-only array of 24 IQ8 but all >> the MIs will be on the customer side of an auto-transfer switch and >> generator. We want to leverage using existing building wiring to carry the >> solar and all solar sizing meets the 120% rules. >> >> >> >> But I know that grid-tied solar on the customer load-side of the transfer >> switch means no place for full solar power production to flow to when the >> grid is not available...but then I thought back to that fast switching >> capability: is there a way to ensure the IQ8 don't backfeed a generator >> when it is operating for a grid anomaly? >> >> I suspect the answer is "are you nuts???" but that video of capability >> got me thinking, "why not?" and if not, how is it - what tells the MI to >> cease production? - when it is within a full and proper ISC/ESS system >> design? >> >> >> >> *Howard "Scot" Arey* >> >> *Owner, Solar CenTex* >> >> >> >> NABCEP PV Installation Professional >> >> TECL 29755 >> >> 254-300-1228 >> >> [image: cid:[email protected]] >> >> >> >> _______________________________________________ >> List sponsored by Redwood Alliance >> >> Pay optional member dues here: http://re-wrenches.org >> >> List Address: [email protected] >> >> Change listserver email address & settings: >> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org >> >> There are two list archives for searching. 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