Limitation to AC coupling with EG4 18K, help required...

[1201]

So sorry for being dumb and asking many times things that may obvious to you but not to me. Everyone learn everyday...or should be.
The answer i have been given by SS, the company who is selling the product under its brand, has not really convinced me to the point i came here to ask if.... I have to pay 22 % on top of the all my SS order to import, custom release and transport the goods to Mexico and if something is wrong i will never be able to ship it back so yes i double and triple check and i think you would do the same in my position.

Being told the product you'll spend 30 k usd is NOT designed to do so by the exclusive distributor is kind of worrying at first thought. SS should know better their own product or the guy i exchanged with is wrong....

i came here to ask to people who know more than i do some information and many answered me : thanks to them !

You're welcome but it's annoying when someone gives you an answer and you say-well ss said something else.

I appreciate your position and with that large of a purchase you should 100% go with what ss says and don't second guess it or confuse yourself by asking what others think, because at that point you're wasting your time- and ours.

 

[Kim Scott]

Hi

I am in talk with EG4 to finc a way to AC couple my current 9.75 kwh array with Fronius Primo 11.4 with new 18 kwh array and the EG4 18K inverter.

Seems easy, plug the existant 9.75 kwh of the fronius on the Generator Input of the EG4 18K and voila (need to set the fronius into micro grid mode to be able to receive frequency shift from the 18K as well but that is a detail) BUT it finally CAN NOT WORK AS EASY AS IT SEEMS.....

EG4 just told me (and thanks for them for being honest) that in that case the system can not use the 200 amp pass through when ac coupled and then you are always limited to....12 kwh output of the 18K....and that you can not export to the grid as well because "The 18K has a 2 poles internal relay that switches back and forth btw GRID IN, GEN IN and LOAD OUT. It is able to utilize 2 of these simultaneously : GRID/GEN (well you can only charge up batteries then, not your load...), GRID/LOAD (ok but then the 9.75 kwh array power....is lost) or GEN/LOAD (Nice you enjoy the power of the grid tie system, the new system.....but are limited to 12 kwh of total output....)

So yes AC coupling looks nice with 18K......until you never exceed 12 kwh of loads...if you exceed that you are DONE.

Does any expert (that i am not....) has an idea of how to manage to enjoy the power of the 2 arrays powering up the loads first, charging then the battery pack and then export to the grid. I was thinking to put a second 18k but then the cost is exploding....

I can renounce to export to the grid because with near 28 kwh of array and 60 kwh of battery i could be good anyway and in this case 3 EG4 inverters 6000 XP....that would set the bar up to 18 kwh of output.....but how to join this system with my 9.75 kwh grid tie array in order to use the power from the grid tie system first....then the power of the new 18 kwh array and then charge the battery pack....and in case of grid down how to avoid that the grid tie inverter restart seeing the power from the 3 pcs of 6000 xp....

I am lost....

Thanks
Vince

Adding another inverter could be potential solution but need to consider the cost as well. It might be helpful to consult a professional.

 

[FilterGuy]

And if the loads are low enough all the AC coupled solar plus some of the 12kW from the inverter that doesn't have to cover remaining solar gets exported. Is that correct?

Yes.... depending on the configuration. For all of the AC coupled power and most of the 12KW inverter power to be pushed to the grid, the system would have to be configured to force the backfeed. (This could be done as part of peak shaving). However, in many configurations, the inverter would not produce any power from the battery and only backfeed the grid if the DC-coupled PV is producing power that is not needed by the loads or batteries.

As I said in an earlier post, the 18Kpv is highly configurable so there is often no unqualified answer to these scenarios.

 

[BKY2003]

You always have the option of wiring a critical loads panel. Since you can only export 10kw, the 70amp breaker should be plenty. (requirement 225 amp bus) This would allow you to balance the loads to the capacity of the 18Kpv.

The advantage of wiring the 18Kpv like Millsan1 rather than a critical loads panel, is you get to pick which loads get to stay on in a power outage. Example turning off the breakers on your panel that are not needed until you reach load balance with the 18Kpv.

 

[millsan1]

I will post here the answer of SS once i got it for sure. Meanwhile and in order to be understandable by the basic human being i am....here are the basic questions i still try to find a clear answer...if any expert could light my path...i would be happy !

Each time a 10 kwh array is AC coupled to the 18 k and a 18 kwh array is directly connected to the 18 k MPPT with 60 kwh of batteries.

Case 1 : Grid export is permitted.

Grid is ON, total load is 15 kwh, ac coupled array is giving 3 kwh, 18k array is giving 5 kwh and batteries are dead or at SOC that does not permit any power draw. What happen ? Does the 18k can draw power from the grid in grid assist kind of mode ?

Grid if DOWN,
total load is 15 kwh, ac coupled array is giving 3 kwh, 18k array is giving 5 kwh and batteries are at 90% SOC. What happen ?
Does the total power able to being draw is equal to 12 kwh inverted from the 18 K + the AC coupled array power given a the same time or does it can not be added to this ?

Case 2 : Grid export is NOT permitted.

Grid is ON, total load is 8 kwh, AC coupled array is giving 7 kwh, 18k array 15 kw what is happening ?

If load is 6 kwh, AC couple array is giving 1 kwh, 18 k array 3 kwh and batteries are dead, does the grid assist works ?

This is confusing because the system works in Millsan1 config as i was thinking it should be even if he did not tried bigger loads than 12 kw to see what happen and at the same time SS guys are telling me it can not work like this. I am lost

Be sure i will post SS answer here asap i get it....

Case 1 - On- Yes, you can draw from the grid, up to 200 Amps
Case 1 - Down- You are at max, since AC Couple is only giving 3. 3+12 from 18 = 15, so you are OK.

Case 2 - 8kw- Load is fed, excess goes to batteries. When batteries get to a set point you control, the AC Couple will be ramped down. In my case I have it set to 95% SOC. When batteries reach 95% SOC, AC Couple will be turned off via frequency shifting. When batteries reach 100%, solar will feed your loads, there is no excess, as loads pull power, solar does not push power.

Case 2 - 6KW - Yes, you can pull from the grid up to 200 amps.

Long story short, the only practical limitation is the 12 KW inverting from the 18K, in an grid down situation. But that is a lot of juice, and if it is during the day, you can still get more from the AC Coupled system.

On grid, there is really no meaningful limit. Same deal, 18 can only invert 12K, but AC Couple can provide up to an additional 21 and the grid can provide 200 Amps.

I understand your concerns, but please understand that the info given my the EG4 person was slightly inaccurate and needlessly confusing.

 

[Vince Mex]

Thank you for the answer ! All clear now.

Yes answer from SS is confusing, after 1 week still waiting for their last answer by the way.....

Thanks to all members who took time to answer and help, truly appreciated!

 

[SignatureSolarJess]

Thank you for the answer ! All clear now.

Yes answer from SS is confusing, after 1 week still waiting for their last answer by the way.....

Thanks to all members who took time to answer and help, truly appreciated!

Hi @Vince Mex I'm so sorry you've had to wait a week for a response! We are up to date with emails and there should not be a week's wait time! I'd love for you to DM me your email address so I can look into this.

 

[Vince Mex]

Hi @Vince Mex I'm so sorry you've had to wait a week for a response! We are up to date with emails and there should not be a week's wait time! I'd love for you to DM me your email address so I can look into this.

SS just answered me today and yes GRID, Inverted power from batteries and or directly connected solar array to the 18k AND AC coupled power are available all together when grid is ON. When grid is down the limit is 12 kw from the 18 k added to the AC coupled array.....like Milsan1 and many other explained here.

Thanks to them !