Inverter in sub sub panel on grid tied 18kpv will it work?

[millsan1]

Background:

I have an 18 KPV.

I also have a Growatt 11K, connected to the 18, as an AC Coupled connection. When grid up, gen port is connected to grid, when grid down, gen port is connected to load. 18 controls the output of the 11, in a grid down, via frequency shifting.

18 is feeder tap, and serves the whole house.

All above is fine and working.

I have a sub panel at my outbuilding, fed from a sub panel at the home.




My idea, and question, is this:

Can I put a grid tied inverter at the outbuilding? If I did, according to my mind, it would supply the outbuilding, and backfeed to home, and any excess back to grid.

In a grid down, it would supply outbuilding, backfeed to home, and if all power was met, the 18 would frequency shift, just like with the 11, right?

Since the 18 knows it is AC Coupled, it would do the frequency shifting, and really wouldn't know or care that there are 2 inverters connected to the load side.


Or am I wrong?

Drawing below

 

[BentleyJ]

As stated above, all you are doing is adding another AC coupled system on the Load side of the 18. As long as total AC coupled power doesn't exceed what the 18 can handle it should work although you would loose the ability for the 18 to completely disconnect the proposed new system since it would not be connected to the Gen Input. It would be frequency shifting only so as long as the 18 responds fast enough should be OK.

As long as all the inverters are UL1741 compliant they will work together. It has to be true since several houses in a neighborhood could all have solar and all be connected to the same utility transformer which means all the systems are technically tied together.

 

[DIYrich]

Not advised to put AC PV on the Load Port. In a worst case scenario, the 18k CANNOT disconnect the AC PV, and bad things could happen.

Consider putting the Sub-Panel on the Gen Port of the 18k, and then you can put the AC PV into the sub-panel.

 

[1201]

Background:

I have an 18 KPV.

I also have a Growatt 11K, connected to the 18, as an AC Coupled connection. When grid up, gen port is connected to grid, when grid down, gen port is connected to load. 18 controls the output of the 11, in a grid down, via frequency shifting.

18 is feeder tap, and serves the whole house.

All above is fine and working.

I have a sub panel at my outbuilding, fed from a sub panel at the home.






In a grid down, it would supply outbuilding, backfeed to home, and if all power was met, the 18 would frequency shift, just like with the 11, right?
.


View attachment 216833

Not quite. As drawn wouldn't work.

The grid line from the 18kpv to main panel is dead if the grid is down, which means the new grid tie inverter would also be dead. Only the growatt that's ac coupled would continue to supply loads and charge the battery

 

[millsan1]

Not quite. As drawn wouldn't work.

The grid line from the 18kpv to main panel is dead if the grid is down, which means the new grid tie inverter would also be dead. Only the growatt that's ac coupled would continue to supply loads and charge the battery

No, the second proposed inverter would be connected to the load lines on the 18, not the grid lines. The grid side of third inverter would be connected, through a few hops, the load side of 18.

Only thing connected to grid in my current and proposed config is grid side of 18.

 

[millsan1]

As stated above, all you are doing is adding another AC coupled system on the Load side of the 18. As long as total AC coupled power doesn't exceed what the 18 can handle it should work although you would loose the ability for the 18 to completely disconnect the proposed new system since it would not be connected to the Gen Input. It would be frequency shifting only so as long as the 18 responds fast enough should be OK.

As long as all the inverters are UL1741 compliant they will work together. It has to be true since several houses in a neighborhood could all have solar and all be connected to the same utility transformer which means all the systems are technically tied together.

Yeah, the proposed third inverter would be a small one. Just trying to use the extra 8 panels I have, only about 3k worth, so I was thinking a small Growatt, like my 11, but the 3800 version

 

[1201]

No, the second proposed inverter would be connected to the load lines on the 18, not the grid lines. The grid side of third inverter would be connected, through a few hops, the load side of 18.

Only thing connected to grid in my current and proposed config is grid side of 18.

Ok so your main panel is connected to the 18kpv via the load output?

What's the benefit of connecting the next inverter in the outbuilding instead of close to the 18kpv?

 

[millsan1]

Ok so your main panel is connected to the 18kpv via the load output?

What's the benefit of connecting the next inverter in the outbuilding instead of close to the 18kpv?

Best place to mount panels for me. I don't want penetrations in my new roof at home. Have panels on my garage, and everything else is ground mounted. I have all the mounting hardware for the outbuilding already, as that was my original plan, so all I'd have to buy is a $700 inverter.

 

[1201]

Best place to mount panels for me. I don't want penetrations in my new roof at home. Have panels on my garage, and everything else is ground mounted. I have all the mounting hardware for the outbuilding already, as that was my original plan, so all I'd have to buy is a $700 inverter.

What is your main panel connected to? 18kpv load output?

 

[millsan1]

What is your main panel connected to? 18kpv load output?

Yes. 18 is in whole home config

 

[1201]

Yes. 18 is in whole home config

Ok got it now. Seems like it would work the way you envision.

 

[BKY2003]

Can you add the extra panels to the Growatt 11? And run it as independent Mppt, since the 11 will take 22.8 kw of panels.

 

[millsan1]

Can you add the extra panels to the Growatt 11? And run it as independent Mppt, since the 11 will take 22.8 kw of panels.

Outbuilding is really last location, before I live in the middle of a solar field.