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Please recommend inverter to AC couple with Sol-Ark 12K

SolarHead

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I'm considering getting an inverter that I can hook about 4k worth of solar panels to and bring that into my Sol-Ark 12K via AC coupling. I have not studied the AC coupling yet to see what requirements it would mean or place onto an inverter. I just got started in my research on which inverter to buy. I thought about asking Sol-Ark for a recommendation but I don't think they recommend products or brands.

I tend to think something like this might work, but I dont know enough yet to make an educated decision

or
SunnyBoy 5.0
 
It would seem drastically easier and cheaper to simply add 4kW of panels and another MPPT if it's beyond what the Sol-Ark can handle.

AC coupling is mostly useful for adding grid-down functionality to a grid tie system. Once you have the off grid inverter, it doesn't make a lot of sense to add AC coupled PV.
 
I agree with sunshine_eggo but if you really wish to AC Couple then any UL1741SA compliant grid-tie inverter will work. Fronius & SMA as you have already aware of. Outback & SolarEdge are solid products. I believe Generac has UL inverters and they will be competing with Enphase in the microinverter space.
 
Yep, I agree that AC coupling is mostly used for retro-fit applications where someone already has an inverter in place, and they want to bring in more power such as adding a new inverter like a Sol-Ark for example (or any inverter that can handle and do AC coupling). The idea is , that you keep your old inverter in place and working (no changes), then you bring that existing AC power its producing over to a new inverter and AC couple it so the new inverter uses that AC power from the old inverter, and more-or-less passes it through onto your loads and/or batteries. That way you don't have to remove your old inverter , and you get to utilize that power. More than likely the new inverter also brings in new power by way of new additional solar panels (a 2nd array for example).

But there's some people (like myself) that might have say extra 4,000 watts of solar panels in storage that they want to use. I could buy another MPPT SCC and bring that power over to help charge my batteries but my existing array and inverter are doing a nice job at topping my batteries off within 3 hours each morning. From my knowledge not all inverters can AC couple with another inverter (whether existing or new). I have a Sol-Ark 12K and I could utilize the 4kw of power from those panels by AC coupling it to my Sol-Ark. That's AC power so the Sol-Ark doesn't have to run it through its inverters because its already AC power coming in.

I talked with Sol-Ark since the user manual just touches on AC coupling. One phone call was worth it for sure. So basically I can bring in 9,000 watts max via AC coupling. It requires that my GEN breaker is used for the AC coupling, which is fine with me because I don't have my generator connected directly to my Sol-Ark. My generator is a stand-by and its connected to my main service panel via ATS. That way if the grid fails, the ATS fires the gen and covers my main service panel, and by way of the 60A breaker I feed the Sol-Ark it's grid power for pass-through. I realize that's not the generator configuration some would prefer but it's what I have because my stand-by generator was already in place when I decided to build a solar system, and the 22kw gen can produce ~92-96A so I didn't want to clip its capacity by connecting it to my Sol-Ark since it can handle 50A into its GEN breaker input.

The reason I want to bring the 4kw of panels power to my Sol-Ark is it can manage the power better than just getting another MPPT. It can use the power to cover my critical loads panel as well as assist my main service panel since I am using the "limited to home" mode which to me is maybe the best feature of the Sol-Ark. All that wiring is already in place so so AC couple another inverter is really easy.

Sol-Ark, as I guessed, would not recommend a brand or model of inverter but said as long as it will do 240V , and is UL1741SA , then it would work. They said if I were off-grid then I would want to use frequency shifting to wake the new inverter up. But , I am grid-connected so they said no worry about frequency shifting, that the inverter would just be either off or on, and it would not have its power adjusted (like it is when you have DC) when coming in, that it would just come in as pass-through AC power. Of course I would be limited to the 63A pass-through when on-grid which is fine because I'm currently no where near that with my existing config. I still wonder if the power coming in from the AC coupling will continue to power or cover my critical loads panel. I think it should but will confirm. I do realize that the Sol-Ark will stop sending any and all power to my main service panel in a grid down situation because by law they can't send power to the main service panel when grid is down due to safety reasons. But I'm 99% sure the power from the AC coupled inverter will continue to be fed to my critical loads panel only.

Verdict is ....my desire to bring in additional 4kw of solar panel power is well within my inverters capacity and current configuration. The Sunny Boy or Fronius seem to be a good fit, probably get a ~5kw model, and install it close to my Sol-Ark so the AC wiring doesn't have to be so long. I can bring PV wire the 180 feet from the array all the way to the new inverter easier than I can running AC wire I would think.
 
I'm considering getting an inverter that I can hook about 4k worth of solar panels to and bring that into my Sol-Ark 12K via AC coupling. I have not studied the AC coupling yet to see what requirements it would mean or place onto an inverter. I just got started in my research on which inverter to buy. I thought about asking Sol-Ark for a recommendation but I don't think they recommend products or brands.
I'm pretty sure they'll be recommending these before too much longer:

...and you'll have one fewer throat to choke.
 
I don't think they'll recommend brands other than their own, which makes sense to me. I don't know much about micro inverters, other than they are installed at the solar panel modules, and converts DC to AC right there at the array (I have a ground mount). I assume then I would take AC power from the microinverter and it would need to be a sized (by code) accordingly to run ~200 feet to my inverter. That's something I've never understood with microinverters, why do that and then bring AC wiring from the array to the house (to the inverter location)? I like the DC power on PV wire, 10 gauge for coming from a ground mount over to the house as it seems to make more sense. Anyway, that's maybe a different topic or thread (microinverters). I ended up going with a Fronius 5.0 that I plan to AC couple. I'll bring PV wire from my new (2nd) array to the house where I have the Fronius, then couple it to the Sol-Ark 12K via the GEN breaker. Sok-Ark recommends the coupled inverters array be less power than the main array that comes into the Sol-Arks MPPT, which makes sense. I think if you bring in equal power or more power from the AC coupled inverter, things can get confusing for the Sol-Ark somehow. I have 11.5kw on my main array, and plan to install 4kw on the AC Coupled inverter. Sorry to jump around, I feel like I'm discussing 3 different subjects in one post here ! I can type 130wpm and find it easier than writing or talking so I type a lot. And I figure others can learn from the discussion so I try to be clear as possible.
 
Can someone explain the benefits of microinverters that are installed right at the modules (array) ? Seems to me there's more CONS than PROS

The CONS I see;
  • you have more equipment outside in the elements
  • you have to run AC wiring (thicker gauge) from the array to the inverters location
  • the shading thing that is touted, doesn't resonate with me. I've seen tests on video where shading benefits of using microinverters doesn't help but like 3%
  • you're bringing AC power into the home and kind of by-passing an inverter that can centrally manage the power and what you want to do with it. You can AC couple the power to a wall-mount inverter and manage the power but you're still kind of bypassing.
  • more moving parts, more to diagnose, more to break/fix
The PROS I see;
  • you can monitor each solar panel separately (or in pairs) but don't see the big deal in that. I can tell you if all my panels are producing or not without the use of microinverters

Maybe there's some specific use or situation that calls for the use of microinverters? I don't see much value in them myself unless there's something I'm not seeing or thinking about. Someone care to chime in?
 
Re. string inverters vs. microinverters, on the Internet you'll find there's a LOT been written regarding PV system architecture, and discussed/argued more articulately than is worth rehashing here. There is no correct answer, certainly none that applies to every residential customer, but let's just say there are reasons Enphase has taken a very large chunk of the US solar market by storm over the last 5 years.

Here's a not-awful summary:
 
They said if I were off-grid then I would want to use frequency shifting to wake the new inverter up. But , I am grid-connected so they said no worry about frequency shifting, that the inverter would just be either off or on, and it would not have its power adjusted (like it is when you have DC) when coming in, that it would just come in as pass-through AC power.

If you were 100% on-grid, you wouldn't have bought a SolArk.

You will want the frequency-watts feature of UL-1741-SA, because when grid is down the Sol-Ark should be able to control power that way.
Also, having fewer watts of GT PV (on generator connection) that the DC coupled watts is recommended, I think. That is so regardless of how well and how fast AC coupled power gets adjusted, SolArk can always match load by adjusting its inverter output and disconnecting GT PV if necessary.
 
If you never operate off battery, only use PV to supply loads and backfeed the grid, a grid-tie PV inverter would be more economical.
For $2000 you can get 7.7kW Sunny Boy.

The reason to pay $5000 or $7000 for SolArk is to have battery backup (or maybe batteryless backup option?) in addition to backfeeding grid.
Extra features all in one box, more expensive than just GT PV.


I have had GT PV inverters for almost 20 years, and added AC coupled battery inverters to them two years ago.
SolArk, like some other hybrids, provides similar functions in one box. Lower cost, high frequency design being one reason and integrated package being another.
 
If you never operate off battery, only use PV to supply loads and backfeed the grid, a grid-tie PV inverter would be more economical.
For $2000 you can get 7.7kW Sunny Boy.

The reason to pay $5000 or $7000 for SolArk is to have battery backup (or maybe batteryless backup option?) in addition to backfeeding grid.
Extra features all in one box, more expensive than just GT PV.


I have had GT PV inverters for almost 20 years, and added AC coupled battery inverters to them two years ago.
SolArk, like some other hybrids, provides similar functions in one box. Lower cost, high frequency design being one reason and integrated package being another.
I understand all of that. I just don't understand the "If you were 100% on-grid, you wouldn't have bought a SolArk." . I bought a Sol-Ark and I was 100% on grid (and still am) when I bought it.
 
By 100% on grid I mean never have power when grid fails.
If SolArk provides backup during grid failure, I'm referring to that as < 100% on-grid. You are operating off-grid part of the time.
(I didn't mean some circuits entirely off-grid.)

Of course, another reason for a hybrid like SolArk could be to store part of PV production and later supply part of load from battery. Limiting export and shaving peak consumption, maybe due to time of use rates.

If SolArk support told you frequency-watts didn't matter on-grid, that meant never operating with battery backup when grid down. 100% on-grid.
(It is possible to operate off-grid without frequency-watts, but that switches between 100% of available PV and 0%. Either cycles battery, or makes use of DC coupled PV.)
 
I'm pretty sure they'll be recommending these before too much longer:

...and you'll have one fewer throat to choke.
Yep. They should hit distribution first week or two of September. I’m buying some to do AC coupling to my Solarc 12k. They are supposed to have communications of some sorts with the solarc inverters. Very excited for this. If you don’t want to wait, just grab some cheap NEP or Enphase micros and be done with it.
 
By 100% on grid I mean never have power when grid fails.
If SolArk provides backup during grid failure, I'm referring to that as < 100% on-grid. You are operating off-grid part of the time.
(I didn't mean some circuits entirely off-grid.)

Of course, another reason for a hybrid like SolArk could be to store part of PV production and later supply part of load from battery. Limiting export and shaving peak consumption, maybe due to time of use rates.

If SolArk support told you frequency-watts didn't matter on-grid, that meant never operating with battery backup when grid down. 100% on-grid.
(It is possible to operate off-grid without frequency-watts, but that switches between 100% of available PV and 0%. Either cycles battery, or makes use of DC coupled PV.)
For me, I use TOU (time of use) with my batteries between 3-7pm to lower my utility cost.

I also use for off grid backup.

As for AC coupling, Im about to add some AC coupling in addition to my DC coupling just so I can have a little more Solar without adding a second parallel Sol-Ark. I’m going to buy 3 or 4 of the new Sol-Ark micro inverters when they come out next month. Supposedly, they will have communications with the Sol-Ark 15k over WiFi in some way to work better when grid is down (or off grid). We will see. I’m excited to try it out.
 
I’m going to buy 3 or 4 of the new Sol-Ark micro inverters when they come out next month. Supposedly, they will have communications with the Sol-Ark 15k over WiFi in some way to work better when grid is down (or off grid).
Is there any information about that available online? I can imagine several ways that could be a good thing, but would be nice to know more specifically what Sol-Ark will be bringing to the table.
 
I saw Tom from Soll-Ark speaking on a Webex and he said something like "using our micro's in comparison to others will give us more control about how they interact with the Sol-Ark 12/15 K's". Not sure of what he meant by that, but it sounds like they will have some form of comms. It sounds like they are still supposed to hit the market 1st week of September.
 
Would be good if they can use powerline or data cable to command output power, so that can be done even while grid-connected (for limited or zero export), also faster response than frequency shift allows when off-grid.

There is some SunSpec or other method for GT PV inverter control. Used for grid support and selling to spot market. A de-facto standard like that would be useful for better multi-vendor integration.
 
If they are AC coupled to the AC couple/gen input breaker on the Solark, then the same limited to home or sell to grid would apply and be controlled by the inverter. Now without the solark 12k/15k main units and just going direct I don’t know if you can pair them with CT sensors to limit export etc. they do have built in WiFi in each micro inverter. They said if you don’t have WiFi signal at install area, there is a controller you can get that makes them work similar to Enphase Envoy controller. I agree it will be super cool if they end up having the features that they hinted at on the installer web meeting. I’m super pumped to check them out!!!!
 
I'm considering getting an inverter that I can hook about 4k worth of solar panels to and bring that into my Sol-Ark 12K via AC coupling. I have not studied the AC coupling yet to see what requirements it would mean or place onto an inverter. I just got started in my research on which inverter to buy. I thought about asking Sol-Ark for a recommendation but I don't think they recommend products or brands.

I tend to think something like this might work, but I dont know enough yet to make an educated decision

or
SunnyBoy 5.0
Why not just grab some Enphase iQ8plus or NEP BDM-600x or 800x micros and be done with it? I’ve done some AC Coupling with a 12k using Enphase and I’m about to do a new setup with my 15k using NEP BDM800’s. NEP is half price of Enphase, and since I wouldn’t care about any of the sunlight backup gimmick stuff from Enphase, the NEP makes a lot of since for me. Just a suggestion to research. ?
 
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