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

[Hedges]

Yes but, how does inverter shift frequency on Gen port but not on Load port?

(by the way, my Avatar shows my 4x Sunny Island system which is AC coupled to Sunny Boy for backup. And I was the one who tried to get it to work with SB 10000TL-US-12 then told SMA that inverter fails to ramp down power when in "backup" mode, only works in "island" mode. SMA confirmed my report by firmware review, and updated their compatibility document to say that model was not supported for backup.)

Maybe I should have said, "like I'm an EE who has implemented and debugged AC coupled systems with frequency-watts?"

 

[BKY2003]

Obviously you can't backfeed 200A PV breaker in 200A panel with 200A main breaker under 120% rule.
So line-side or load-side tap makes sense.

Unless you remove all other breakers from the panel, then use the rule "sum of all breakers not counting main breaker", just a 200A PV breaker, no loads on main panel.

I think that's what is colloquially known as "Hawaiian Tie-In."



Could you explain how that works to me, like I'm an EE?

Unfortunately, had to explain how I comprehend it.

 

[millsan1]

I understand the Gen Port is bidirectional and that the recommended connection configuration is to connect AC coupled solar to the Gen Port. Do you know if the load port is bidirectional?

I do not believe so, and I have read nothing that indicates it is.

 

[Hedges]

You comprehend it correctly, as do I.
There is only a relay between output and generator port. Not an entire inverter. They can't be different frequencies.

I'm the EE here who usually helps others with Sunny Island and Sunny Boy issues.
But I do learn from others here too.

Likely Generator port is recommended so it can be shed instantly. And may have a current limit smaller than some existing GT PV systems. Ought to work to put them on load rather than generator port, but there could be issues when load suddenly shuts off and inverter can't stuff current into battery fast enough. Or can't reverse bidirectional DC/DC converter.

SolArk recommends DC coupled PV greater than AC coupled, which lets them ramp DC up and down. But they also recommend using generator port.

 

[BKY2003]

Vince Max please let us know how it works out? I rudely interrupted hoping to get the thread back on topic. I am really interested how your system turns out. Thanks

 

[1201]

I do not believe so, and I have read nothing that indicates it is.

i would be shocked out of my mind if the load port is not bidirectional

 

[Vince Mex]

Vince Max please let us know how it works out? I rudely interrupted hoping to get the thread back on topic. I am really interested how your system turns out. Thanks

Well i was excepting the behavior i explained and understood for EG4 docs about the 18k but EG4 system design guy is telling me NO and Millsan1 is doing what i do plan to do with the 18k....so i guess i will disturb Millsan1 to be sure we are in the same configuration goals before buying for 25 k of goods to EG4....

 

[millsan1]

i would be shocked out of my mind if the load port is not bidirectional

Cool story bro.

 

[Ampster]

I believe it's because the gen side frequency shifts, And the load side does not.

How could one port have a different frequency than another port when there is only one inverter? I don't know the details of the EG4, but if it is like my SolArk, the Gen Port is used for AC coupling so that when the grid is down and the loads shift down signigficantly, the Gen Port relay can drop the AC coupled solar if it cannot ramp down the AC coupled solar fast enough.

 

[1201]

How could one port have a different frequency than another port when there is only one inverter? I don't know the details of the EG4, but if it is like my SolArk, the Gen Port is used for AC coupling so that when the grid is down and the loads shift down signigficantly, the Gen Port relay can drop the AC coupled solar if it cannot ramp down the AC coupled solar fast enough.

you know, Im confused why they advocate for the gen port, especially in the case of the 18kpv.

If it controlled pv inverter output while on grid, it would make sense to use the gen port, because it could just disconnect the relay since it would have no way of frequency shifting.

but, the 18kpv passes all ac coupled pv to the grid so why does it need to be able to disconnect the pv?

if there is no grid it should be able to quickly drop any grid tie inverter even on the load port, instantly. once a day my hybrid inverter intentionally drops the pv inverter that's ac coupled on the load port. it raises frequency to 63 hz for a second and the pv inverter is INSTANTLY dead.

surely any decent hybrid inverter can do this.


edit:
I may have answered my own question"

from the manual.
When On-Grid and Export to Grid enabled, the AC-coupled inverter will always be on, and it will sell any extrapower back to the grid. Ensure you are allowed to sell power to your utility provider. When export to Grid is disabled, the AC-coupled inverter will stay at off mode and could not work at on-gridmode to sell power.

 

[BKY2003]

How could one port have a different frequency than another port when there is only one inverter? I don't know the details of the EG4, but if it is like my SolArk, the Gen Port is used for AC coupling so that when the grid is down and the loads shift down signigficantly, the Gen Port relay can drop the AC coupled solar if it cannot ramp down the AC coupled solar fast enough.

Obviously, it can't. I was just hoping the thread would get back on topic with that comment. Unfortunately looks they are taking the conversation behind the Scenes. But thanks for the reply.

 

[CRenner]

If the AC Couple goes to the gen port, where does the gen go when you need it?

 

[solar8484]

My bet would be it would sense voltage and trip something and stop working.

Doubtful unless you have actually tried it.

 

[millsan1]

If the AC Couple goes to the gen port, where does the gen go when you need it?

Chargeverter

 

[millsan1]

Doubtful unless you have actually tried it.

I haven't, nor will I, since there are clear instructions on how to do it.

A critical point to my statement above is "my bet", I did not make a statement of fact nor an assertion of absolute truth. I put forth my thought. I am more than open to being wrong, but I will not be testing the theory, since I have my system upa nd running, as expected, as per manual, and it works very well.

 

[Ampster]

If you were to use an inverter that AC couples to the Load Output of the inverter (not the Gen input) via a breaker in the same main or subpanel.

This is the answer to the OP's question. He will get all the benefits of AC coupling when the grid is up and the generation of the AC coupled solar will pass through the EG4 and be exported after covering loads. When the grid is down he can alway disconnect the AC coupled solar if there is not enough load to absorb that generation.

 

[Ampster]

i would be shocked out of my mind if the load port is not bidirectional

I agree, and that is why the solution that @BentleyJ proposed could work when the grid is up.

 

[BKY2003]

OP, where I think the tread got off topic "AC coupling with EG4 18K" is the EG4 18Kpv is not described by EG4 for AC Coupling to the Load terminal. If that an option that you might consider I suggest looking at the SolArk. But if you wire the 18Kpv different than what EG4 presents, you are likely to get a response from SS. We did not advise against AC Coupling to the GEN PORT. Then the Warranty could be denied. They do rigorous investigation into what is going on. I know because I have experienced it. So if load side AC Coupling is what is needed, I don't think EG4 18Kpv is an option. Just wanted to clarify the difference so you could make a wise purchase.

​

 

[ksmithaz1]

i would be shocked out of my mind if the load port is not bidirectional

I don't think the load port on the 18Kpv is 'bi-directional' in normal operation. I'm under the impression it's output only. I would think it would cause issues if you unexpectedly put power on it. Been a while since I looked at the manual, but AC coupling (microinverters) was to be done on the gen port I thought, with a soft-switch to let it blend. Load port was only for critical/all loads which allows for normal output when there is no A/C on the grid port. Please correct me if I'm wrong.

 

[millsan1]

This is the answer to the OP's question. He will get all the benefits of AC coupling when the grid is up and the generation of the AC coupled solar will pass through the EG4 and be exported after covering loads. When the grid is down he can alway disconnect the AC coupled solar if there is not enough load to absorb that generation.

There is no reason to go through these machinations.

The 18, when AC Coupled via Gen port works like this:

Grid up, gen connected to grid.

Grid down, gen connected to load.

Then, based on your config, it will run loads, feed battery, and cut off as battery gets near full (user configurable), then when battery goes down to another user set level, AC couple comes back.

In my case, I have it set to 95 as top cutoff and 90 as cut on. Again, this only comes into play when grid is down. Hen grid is up, power just flows to where it is needed.

Once configured, there is nothing the end user needs to do to make this work.

 

[Ampster]

There is no reason to go through these machinations.

One reason would be to answer the OP's question. He said he cannot AC couple his existing GT inverter and also get the benefit of the proposed DC coupled array through his proposed 12kW inverter. It would be nice to hear from @Vince Mex if what was suggested is an alternative. It is not a machination to find an optimum solution. I understand the OP has gone offline to find a solution.

 

[Quattrohead]

Surely the 18K PV and solark 15K are basically the same configuration as far as inverter and switching of ins and outs. They can do the same thing with the same settings and configuration.

 

[1201]

There is no reason to go through these machinations.

The 18, when AC Coupled via Gen port works like this:

Grid up, gen connected to grid.

Grid down, gen connected to load.

Ac couple output via gen port is not connected to loads if the grid is up?

 

[millsan1]

Ac couple output via gen port is not connected to loads if the grid is up?

Not directly. It is connected to the grid, which ultimately can/is connected to the load. I think to be accurate, one would say it can feed the load, but is not directly connected.

 

[1201]

Not directly. It is connected to the grid, which ultimately can/is connected to the load. I think to be accurate, one would say it can feed the load, but is not directly connected.

Ok so when grid is up the gen is connected to grid which is connected to load?

So all three are connected together. Otherwise it would be impossible for load to get power from ac coupled pv while on grid