Sol-Ark 12k AC Coupling Side Load (into sub panel) vs into Gen breaker

[Benzimidazolone]

I currently have a grid tied 12k with a 32 kw of panels (south facing roof) into the two MPPT's and 25 kwh of LFP batteries. I want to add some additional panels (east and west roof) using micro inverters.

The current 12k manual shows (I think) two ways of doing this. The first (pg 9) is a 'side load' running the panels directly to sub/critical loads panel. the 2nd (pg 10) shows the micro inverted panels going into the generator breaker.

Other than not being able to us a generator if you use the gen input, are there any advantages/disadvantages of either way?

 

[DougfromdaUP]

You've already got almost three times as many PV panels connected as Sol-Ark says they allow. Is that working well? Have you had them connected during the summer?
In view of this, I think I'd be reluctant to add any more PV that the inverter would have to deal with, i.e. to the grid input, so maybe the load side coupling would be better.

 

[Benzimidazolone]

Sorry if I have caused confusion. The 32 panels (4 arrays combined into 2) are 400 watts each or 12.8 kw. They feed into the 2 MPPT's. The Sol Ark allows 13 kw on the MPPT side of the input (DC side). That part of the system is working very well. They have generated a max of 10 12 kw quite a few times over the last couple of weeks (I am located about 250 miles east of Miami).

My question is about what I can AC couple and what is the difference between what Sol Ark calls 'side loading' into the sub panel and AC coupling through the 'GEN' breakers.

 

[Think About It]

It's not "side-loading". It's called "Load Side AC Coupling" which requires the use of micro-inverters.

You could feed the AC output of the micro-inverters into your load center via a circuit breaker. Be aware that the bus bar in your load center has to be rated to handle the additional current.

Alternately you could feed the output of the micro-inverters into the Sol-Ark via the generator input. This may be the preferred method if you have batteries.

In either case, I would consult with an electrician that is experienced with PV and is familiar with all the electrical and fire code nuances.

 

[BentleyJ]

My question is about what I can AC couple and what is the difference between what Sol Ark calls 'side loading' into the sub panel and AC coupling through the 'GEN' breakers.

Check out this YT video regarding AC coupling with the Sol-Ark 12K

 

[Benzimidazolone]

Check out this YT video regarding AC coupling with the Sol-Ark 12K

link?

 

[BentleyJ]

Not sure what happened, here it is.

 

[Ampster]

@Benzimidazolone
With 12.8kW of solar going through your MPPT in the SolArk and 25kWh of batteries you have a lot of flexibility to AC couple to the SolArk,
As far as I can tell you can AC couple more kWs if you use the Gen port. (I will try to find the specifics) I think the reason is that the gen port allows SolArk to open the port to shut down the AC coupled inverters in the situation when the grid drops and there is very little load. If you use a sub panel connected to the load side of the SolArk, it has to use frequency Watts to control the AC coupled inverters and there is some latency so the SolArk algorithm needs some time to ramp down the GT inverters. This is pure speculation on my part based on previous experience with an Outback Skybox, much reading about AC coupling and my fairly recent experience with my new SolArk.
The pros and cons about using the Gen port or going through a sub panel are based on user preferences. I chose to go through the Gen port because I never intend to need a generator. One of the benefits may be that you get the internal shunts to measure your GT inverter(s) generation on your SolArk reporting. Other factors include how much capacity you want to couple and whether you want to use the Gen port for some other purpose. Remember this is only a factor when the grid is down and you want the SolArk to be the Grid Forming source to AC couple to GT inverter(s). When the grid is up the grid is a buffer and the SolArk can pass through as much as either of those ports will allow. As mentioned above, if you do use a subpanel, there is a NEC backfeed rule that must be followed. Hope that helps frame the issues for you. I love my SolArk.

 

[ImAnIdiotPleaseBePatient]

> (I am located about 250 miles east of Miami).

Are you on a ship?

 

[Danke]

I currently have a grid tied 12k with a 32 kw of panels (south facing roof) into the two MPPT's and 25 kwh of LFP batteries. I want to add some additional panels (east and west roof) using micro inverters.

The current 12k manual shows (I think) two ways of doing this. The first (pg 9) is a 'side load' running the panels directly to sub/critical loads panel. the 2nd (pg 10) shows the micro inverted panels going into the generator breaker.

Other than not being able to us a generator if you use the gen input, are there any advantages/disadvantages of either way?

Are you allowed to back feed grid?

 

[Ampster]

Are you on a ship?

He said grid tied, so I presume an island east of Nassau.

 

[Benzimidazolone]

> (I am located about 250 miles east of Miami).

Are you on a ship?

I am on one of the islands in the Bahamas

 

[Benzimidazolone]

Are you allowed to back feed grid?

My utility does not allow any feeding back to the grid

 

[Quattrohead]

Seems to me that you might be better off adding more battery not more panels as you seem well sorted in that department.
However if you go with more panels and micro inverters definitely use the generator input and micro inverters that will work with the solark during a power outage.
Grab yourself the latest manual from their website as they are continually updating it.

 

[Danke]

My utility does not allow any feeding back to the grid

In that case, unless you use all the power from AC coupling (consumption via loads/battery charging), any excess power will be sent back through to the grid.

 

[Ampster]

It's called "Load Side AC Coupling" which requires the use of micro-inverters.

I don't know any reason the SolArk would not AC couple with a string inverter? I previously AC coupled a string inverter to an Outback Skybox. Now I do have micros connected to the Gen port of a SolArk.

 

[629658]

IMO you should use the Gen port and if you ever decide to add a generator you could do that on the grid input and a ATS.

 

[jjhdtv]

Hello all. Ended up on this thread as I have a very similar question/issue (want to use AC coupling with my Solark 12k grid tied and have generator backup). The goal is to add capacity that I can sell and store in more batteries. I currently have my 8kw generator connected to the Gen Input on the Solark (not often used except for the recent storms here in Northern Ca.) Solark has told me that using micros or String Inverter would be ok on the Gen input and correct software settings (AC coupling).

I had a thought of using a relatively inexpensive Hybrid Inverter (240v 5kVA non grid-tie MPP or Growatt or similar) connected to a 3 to 4kw separate array, the generator and a new 48v battery. Essentially a small complete independent off-grid solar system that supplements and provides backup emergency power to the main Solark 12k system through the AC coupling/Gen input. I forgot to mention that in addition to the solark being grid-tied, I also have it powering my critical loads. During outages, my critical load circuits provide all the luxuries I need. My current battery will keep the lights on and beer cold for about 4 hours. Need to start the generator after that.

Looking for advice and fatal flaws with this concept. From the DIY perspective it seems the most economical and family friendly (as it can be messed with without affecting the main system) to accomplish adding capacity storage. Appreciate the input.

 

[629658]

On first glance I think the least expensive way to go would be install an ATS add your gen there put your AC couple on the gen port. This way everything goes in the Sol Ark and it will seemlessly manage all your power needs and you won’t have to mess with anything in the event of an outage. I would seriously consider adding more storage. If your gen is manual start you might add a gen pigtail to the Grid input of the Sol Ark. If grid goes down attach Gen to the pigtail, Start it, and the Sol Ark will see it as a Gen if you check the box gen attached to grid input. That might be the cheapest way to go.

 

[Benzimidazolone]

In that case, unless you use all the power from AC coupling (consumption via loads/battery charging), any excess power will be sent back through to the grid.

I don't think so because the side load would go into the critical loads panel and not the main panel

 

[Ampster]

I had a thought of using a relatively inexpensive Hybrid Inverter (240v 5kVA non grid-tie MPP or Growatt or similar) connected to a 3 to 4kw separate array, the generator and a new 48v battery. Essentially a small complete independent off-grid solar system that supplements and provides backup emergency power to the main Solark 12k system through the AC coupling/Gen input.

Are you using all the MPPT inputs to the SolArk? The simplest and easiest way to add more generation capacity is through DC coupled sola direct to the SolArk. The only issues with that depend on your jurisdiction rules. In my jurisdiction it would require EMT conduit from my solar to the SolArk and if mounted on the roof, it would requires rapid shutdown devices. Those are the reasons I will probably add more micros since I am ony adding four panels and for that size micros are the most cost effective way. A 3 or 4 kW separate array with 400 Watt panels would be an additional $1500-2000 in micros. You could get a GT inverter for less than that. I don't know much about MPP or Growatt but if they are in that range or better you would have to make sure they are UL1741SA compliant or they would not successfully AC couple with the SolArk or may not even be capable of safely selling to the grid.
Your situation is significantly different than the OP because he cannot export and you can. I think you would get better and more relevant comments if you started a new thread or posted a comment in the Residential Solar section which is typically grid tied.

 

[Ampster]

I don't think so because the side load would go into the critical loads panel and not the main panel

If the solar generation was greater than consumption anywhere behind your meter, the excess would definitely flow back to the grid. The path from your critical loads panel through the SolArk is bidirectional. There is no way for the SolArk to control that generation, except to open the relay and I do not know if it can be programmed for that. The best way to control GT generation would be with external CTs controlling the micros or a GT inverter. That assumes the GT inverter(s) can be configured for zero export. As you already probably know, the SolArk can control the DC coupled solar because that solar goes through the MPPT controllers. On reflection I am not sure there is any advantage to AC coupling in a zero export environment if you cannot limit the GT inverter(s) to zero export. I understand you are out of capacity on the DC side. You are not limited to micros and any GT inverter which can limit export should work.
A work around would would be to take the SolArk offline in which case it could use frequency Watts to control and modulate the AC coupled inverter(s) to match the loads. What you would lose is the extra support of the grid when you have extra load. It is a trade off which would depend on your circumstances, of which I know nothing about your loads and user preferences, Without additional information this is all speculation,

 

[jjhdtv]

Are you using all the MPPT inputs to the SolArk? The simplest and easiest way to add more generation capacity is through DC coupled sola direct to the SolArk. The only issues with that depend on your jurisdiction rules. In my jurisdiction it would require EMT conduit from my solar to the SolArk and if mounted on the roof, it would requires rapid shutdown devices. Those are the reasons I will probably add more micros since I am ony adding four panels and for that size micros are the most cost effective way. A 3 or 4 kW separate array with 400 Watt panels would be an additional $1500-2000 in micros. You could get a GT inverter for less than that. I don't know much about MPP or Growatt but if they are in that range or better you would have to make sure they are UL1741SA compliant or they would not successfully AC couple with the SolArk or may not even be capable of safely selling to the grid.
Your situation is significantly different than the OP because he cannot export and you can. I think you would get better and more relevant comments if you started a new thread or posted a comment in the Residential Solar section which is typically grid tied.

Thank you Ampster. Good information. Both MPPTs on my Solark are being used and cannot be added to. A new array with Micro-inverters for the AC couple may be the best method. I was getting greedy with the abundance of low cost hybrid Inverters that I did not know existed until recently. (Growatt, mpp, etc). Low cost hybrid inverters coupled with some diy lifepos, could be a fun hobby that could ultimately reduce my power bill. All of which could be tinkered with without disturbing the Solark day to day operation. However, now seeing that there could be issues using the AC power from the inexpensive inverters (non UL1741SA) and difficulties with attaching a split phase 240v generator to them, perhaps micros and an ATS on the solark grid input (for generator) ends up as top choice. Currently I can still export, but as we all know that won't be for ever.

 

[Ampster]

Low cost hybrid inverters coupled with some diy lifepos, could be a fun hobby

My SolArk and previously my Skybox have been a fun hobby indeed. My strategy is to incrementally add micros through AC coupling to my SolArk. After making the transition from the Skybox to the SolArk I have no interest in learning the details, and possibly the shortcomings of another hybrid. Not to mention the complexity of another battery pack. My suggestion is to add more batteries to the SolArk if you need more storage.

 

[jjhdtv]

Currently I running a 10kw 200ah Fortress battery. Would it be possible to add more similar batteries (I.e., 30 kw server rack) in parallel with the Fortress? Seems like this would work but not sure how to split the charging run from the Solark Perhaps a distribution block.