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

[ksmithaz1]

Not what the issue is.

Power is limited to 12Kw when AC coupled to the gen port.

The reason? A relay is present on the gen port to cut power from the AC coupled GT array as frequency shift isn't fast enough. The relay is limited to 12Kw.

That is how I see it. And Hedges explained it here.

I know from testing the gen ports can (will) bridge to load/grid/bus with relays. So, power to the load lugs should be limited to ~50A, but not to the grid side/backfeed. The inverter was engineered to deliver 50A to the load lugs (12klv). If you need more than that you would want to parallel units. More of an engineering issue. If your critical loads panel is > 50A, you'll neet to get more AIO's. That output is not designed to be shared with another power source unless it's another eg4 inverter. You might get it to work with something else, but you may run into phasing issues.

If you are just trying to save money you can dump all of the excess back to the grid side and whatever you have connected there.

 

[Zwy]

I know from testing the gen ports can (will) bridge to load/grid/bus with relays. So, power to the load lugs should be limited to ~50A, but not to the grid side/backfeed. The inverter was engineered to deliver 50A to the load lugs (12klv). If you need more than that you would want to parallel units. More of an engineering issue. If your critical loads panel is > 50A, you'll neet to get more AIO's. That output is not designed to be shared with another power source unless it's another eg4 inverter. You might get it to work with something else, but you may run into phasing issues.

Yes, that appears to be the limiting factor.

If you are just trying to save money you can dump all of the excess back to the grid side and whatever you have connected there.

 

[1201]

The inverter was engineered to deliver 50A to the load lugs (12klv). If you need more than that you would want to parallel units.

Ok so how would it physically limit ac coupled power to the load port?

 

[Zwy]

View attachment 204997

The 18Kpv shifts frequency to reduce power from the AC coupled inverters only when grid is off.

However, when grid is on, grid controls the frequency and thus the 18Kpv can only reduce power from AC coupling by turning off the relay in the generator port.

@FilterGuy explains it in this post.

 

[1201]

The 18Kpv shifts frequency to reduce power from the AC coupled inverters only when grid is off.

However, when grid is on, grid controls the frequency and thus the 18Kpv can only reduce power from AC coupling by turning off the relay in the generator port.

@FilterGuy explains it in this post.

Ok- the grid is on, export is enabled- and there is 18kw of ac coupled power at the gen port. There is 14kw of load at the load port - what happens?

 

[Zwy]

Ok- the grid is on, export is enabled- and there is 18kw of ac coupled power at the gen port. There is 14kw of load at the load port - what happens?

"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, which 2 relays will be switched on?

 

[1201]

"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, which 2 relays will be switched on?

What do you mean? I posed a scenario and asked a question. I'm waiting for your thoughts on what you believe would happen in that scenario.

 

[1201]

This is important





Per the manual,The gen port is 90a passthrough
Per the manual if an actual generator is connected it will pass through up to 21.6kw for loads, not 12kw.

Now assume ac coupled power is connected to the same port instead of a Generator. Same mechanism- it will also pass through up to 21.6kw to support loads.

 

[FilterGuy]

The Gen port behaves differently when configured for AC coupling than when configured for a generator. (I wish it was called something like the Auxillary Port. Calling it the Gen Port leads to confusion)

When configured for a generator, the inverter does not (is not allowed) connect both the grid and the generator to the output at the same time. It must be one or the other. (Generators are not grid interactive so they can not be tied to the grid).

When configured for AC coupling, the inverter can connect both the gen port and the grid port to the load at the same time. (The inverters on the AC coupled PV are grid interactive). Whether the inverter does connect them together at the same time depends on other settings.

Warning: I am going on memory for the following statement so take it with a bit of salt:

If the inverter is set to zero export the inverter disconnects the AC-coupled inverters while on grid because the inverter can not control the export of the AC-coupled inverter. In this configuration, the only time the AC-coupled inverters are used is when the inverter goes off-grid.

However, if zero export is not configured, the inverter will connect both the grid and the AC-coupled inverters to the load. In this case, any of the AC-coupled energy that does not go to the loads or battery will be exported to the grid.

Ok- the grid is on, export is enabled- and there is 18kw of ac coupled power at the gen port. There is 14kw of load at the load port - what happens?

I will assume the inverter is configured for AC coupling at the Gen port.

In this case, the 4K of 'extra' power from the AC coupling will be used for charging the battery and/or exporting to the grid....depending on other settings in the system. (The good news is that the 18Kpv is highly configurable. The bad news is that the answers to seemingly simple questions have to be qualified with the dependency on the configuration)

 

[1201]

I will assume the inverter is configured for AC coupling at the Gen port.

In this case, the 4K of 'extra' power from the AC coupling will be used for charging the battery and/or exporting to the grid....depending on other settings in the system. (The good news is that the 18Kpv is highly configurable. The bad news is that the answers to seemingly simple questions have to be qualified with the dependency on the configuration)

Thanks for clarifying a few important things
1. Gen, grid, and load can all be connected together when ac coupling
2. Gen port will pass through up to 21.6kw to loads, battery, or grid, as needed.

 

[Vince Mex]

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....

 

[1201]

While you wait for ss to respond, watch this excellent video which was just posted today

 

[FilterGuy]

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 ?

I assume the above is all about KW, not KWh.
Yes. The 18K will draw 7KW

from the grid.

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 you have zero Export on and the grid is up, the AC coupling will be turned completely off. 8KW will be going to the load and up to 7KW will go to charging the battery. If the battery can not take the whole 7KW, the MPPT will throttle the 18K array down to whatever is needed by the load and the battery.

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 ?

In this case, the 4KW from the arrays will go to the load and an additional 2KW will come from the Grid. The system will also be able to charge the batteries from the grid at the same time. (Assuming the system is configured to charge the batteries from the grid)

 

[Ampster]

then that power as available for loads in addition to the 12kw of the inverter

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?

 

[1201]

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?

That's correct. Assuming battery is full it will sell the ac couple power up to 21.6kw plus excess DC couple pv up to 12kw to the grid.

 

[Ampster]

That's correct

The the question at the beginning of the thread and in the title of the thread has been answered? There is no limitation other than the overall capacity of the main breaker.

 

[1201]

The the question at the beginning of the thread and in the title of the thread has been answered? There is no limitation other than the overall capacity of the main breaker.

The question has been answered many times. The op doesn't like the answer.

There is a 90a limitation on the gen port relay

 

[CRenner]

Or the OP just doesn't understand.

 

[1201]

Or the OP just doesn't understand.

Eg4 told him it wouldn't work so obviously he would believe them and not us, Even after repeated explanations, including from people who are using the hardware the way eg4 said wouldn't work.

 

[Vince Mex]

Eg4 told him it wouldn't work so obviously he would believe them and not us, Even after repeated explanations, including from people who are using the hardware the way eg4 said wouldn't work.

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 !