If you are using the inverter with nothing connected to the high-voltage DC (PV) bus, AC Coupling is not recommended.
The MNP AIO can operate as a standard string inverter, with or without a battery. Unlike most other AIOs, it can run with both a generator and AC-coupled inputs at the same time (personally tested). However, the AC-coupled input must be smaller (lower output) than the generator input; otherwise, the generator may drop offline. This limitation is in place to protect the generator’s control system. A side note: As with all inverters, firmware remains a major consideration. Fixes and adjustments can sometimes introduce new issues. As inverter technology advances—and with some states requiring utilities to control customer-owned equipment—firmware complexity will likely continue to grow, creating ongoing challenges for installers. We are all in for more challenges as we move forward. On Sat, Aug 9, 2025 at 5:27 PM Jay via RE-wrenches < [email protected]> wrote: > Thx William > > The instructions specifically say that AC coupling only is not > recommended. > To me I read that in terms of the inverter wanting DC solar as well > > Can you explain what’s going on. > Which is the correct way to install it and why does it say not recommended > > Thx > Jay > > On Aug 9, 2025, at 3:13 PM, William Bryce via RE-wrenches < > [email protected]> wrote: > > > With the MNP AIO You can use an AC couple array at the same time as the > Generator. But.... If the AC coupled input is larger than the > Generator input, the Gen set relay will open to protect the Generator. > > On Sat, Aug 9, 2025 at 3:12 PM Jay via RE-wrenches < > [email protected]> wrote: > >> Thx I looked it up. >> But according to midnite they don’t recommend a only ac coupled system. >> >> Jay >> >> On Aug 9, 2025, at 12:53 PM, Dave Tedeyan via RE-wrenches < >> [email protected]> wrote: >> >> >> The Midnite Power AIO has inputs for grid, generator, AC coupling and >> another smart load. I have not used both generator and AC coupling to see >> how it acts if both are active at the same time, but at least the inputs >> are there for them both. >> >> On Sat, Aug 9, 2025, 2:33 PM Jerry Shafer via RE-wrenches < >> [email protected]> wrote: >> >>> Jason, Wrenches, >>> Consensus well that may not be the correct word to use, personally l >>> have used Solark for retrofitting systems that already have GT type >>> inverters, if you go with AC Coupling then the gen set connection is a >>> little more complicated but very doable. >>> Funtimes >>> >>> On Sat, Aug 9, 2025, 11:26 AM Jason Szumlanski via RE-wrenches < >>> [email protected]> wrote: >>> >>>> I go with "Backup Loads" on my drawings. >>>> >>>> Tesla will not charge from a generator. But you can obviously have a >>>> generator power the loads via a transfer switch if the battery is >>>> completely depleted. It's not the best solution, for sure. >>>> >>>> >>>> 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 Sat, Aug 9, 2025 at 1:57 PM jay via RE-wrenches < >>>> [email protected]> wrote: >>>> >>>>> Yeah I’ve given up trying to correct people on that one. >>>>> >>>>> >>>>> >>>>> On Aug 9, 2025, at 11:26 AM, Foxfire Energy via RE-wrenches < >>>>> [email protected]> wrote: >>>>> >>>>> Umm, just an FYI, I actually got dinged for labeling the AC output >>>>> panel from a battery backup inverter as "Critical Loads".. Critical loads >>>>> (Critical Branch circuits) are defined in article 100 of the NEC as >>>>> circuits associated with Patient Care.. AC loads from battery backup >>>>> inverters are more appropriately defined as "Dedicated Loads".. >>>>> Maybe someone could correct me here, but I'm under the impression most >>>>> garden-variety inverters are not rated for Critical Load applications. >>>>> db >>>>> ------------------------------ >>>>> *From:* RE-wrenches <[email protected]> on >>>>> behalf of William Miller via RE-wrenches < >>>>> [email protected]> >>>>> *Sent:* Saturday, August 9, 2025 1:03 PM >>>>> *To:* RE-wrenches <[email protected]> >>>>> *Cc:* William Miller <[email protected]> >>>>> *Subject:* Re: [RE-wrenches] Adding battery to grid tie >>>>> >>>>> Correct me if I'm wrong: I believe AIOs can accept AC coupled power >>>>> through the load ‘output’ port. That leaves the Grid and Gen inputs free >>>>> for their roles as labelled. >>>>> >>>>> The AC coupled inverters connect via a breaker in the critical loads >>>>> panel. >>>>> >>>>> >>>>> William Miller >>>>> Miller Solar.com >>>>> 805-438-5600 >>>>> www.millersolar.com >>>>> >>>>> >>>>> On Sat, Aug 9, 2025 at 9:50 AM david quattro via RE-wrenches < >>>>> [email protected]> wrote: >>>>> >>>>> True. if you want to do grid, gen, and AC Couple then you need a >>>>> transfer switch or contactor. >>>>> Likewise I haven’t touched a Powerwall, nor an Enphase battery. >>>>> >>>>> >>>>> >>>>> On Sat, Aug 9, 2025 at 9:36 AM jay via RE-wrenches < >>>>> [email protected]> wrote: >>>>> >>>>> One big issue with the AIO’s is that you can’t do grid, generator and >>>>> ac coupling to the best of my understanding >>>>> >>>>> I do like the idea of just removing the old GT inverter and stuffing >>>>> that into the AIO, elegant >>>>> >>>>> yes its my understanding that Tesla won’t accept generator. While >>>>> many are pissed off at eg4, I won’t touch tesla. >>>>> >>>>> and FYI you can buy the same inverter at Fortress. >>>>> >>>>> thanks everyone. >>>>> >>>>> jay >>>>> >>>>> >>>>> >>>>> On Aug 9, 2025, at 10:28 AM, Tyrone Houck via RE-wrenches < >>>>> [email protected]> wrote: >>>>> >>>>> Midnite AIO and Sol-Ark both work great for AC coupling in my >>>>> experience. If anyone is new to "All In One" inverters I recommend having >>>>> tech support walk you through commissioning, check firmware, etc. the >>>>> first >>>>> time. >>>>> >>>>> >>>>> >>>>> >>>>> On Sat, Aug 9, 2025, 8:47 AM William Miller via RE-wrenches < >>>>> [email protected]> wrote: >>>>> >>>>> Two options: >>>>> >>>>> 1. AC couple existing inverter to a battery capable inverter. >>>>> >>>>> 2. Replace existing inverter. >>>>> >>>>> I favor option 2. >>>>> >>>>> Option 1 is only preferred if gaining access to the existing inverter >>>>> for replacement is difficult. An example would be a micro-inverter system. >>>>> >>>>> New AIO inverters allow true high voltage PV input so the existing >>>>> stringing will probably not need to be modified. >>>>> >>>>> I’m new to this so type of upgrade so I welcome any corrections to >>>>> these opinions. I did replace a Sunny Boy in my shop with a Soul Ark and >>>>> it’s working great! >>>>> >>>>> William Miller >>>>> Miller Solar.com >>>>> 805-438-5600 >>>>> www.millersolar.com >>>>> >>>>> >>>>> On Sat, Aug 9, 2025 at 8:26 AM Jay via RE-wrenches < >>>>> [email protected]> wrote: >>>>> >>>>> Is there a consensus as to what equipment to use for adding battery >>>>> backup to normal GT inverter? >>>>> >>>>> >>>>> >>>>> I’ve had a few people ask and I actually haven’t done it. >>>>> >>>>> Thx >>>>> Jay >>>>> >>>>> >>>>> _______________________________________________ >>>>> 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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