EG4 18kPV AC Couple Questions

[thepetersms]

Hello All,
I'm in the process of sending power to my 30x50 shop using the EG4 18kPv and the EG4 Powerpro (2) batteries.
My current setup is 48 panel array with 360w panels with 48 IQ7 microinverters. Those are ran back to a electric panel and then fed back to a meter and sold back to the grid.
With my shop power I'd like to run AC coupling and I wanted to run it by here to make sure I'm going in the right direction.
I want to run AC coupling to keep my existing setup the way it is so I can keep selling back power to the grid that isn't being stored on the batteries. I'm a bit confused where I would connect my existing setup into the generator lugs on the 18kPV.

I believe I would disconnect the 3 lines coming into my solar electric panel at the top (those lines come from a 100amp feeder breaker at my main panel)
Run 3 new lines back to my shop and into my 18kPV into the Generator lugs. Then run 3 more lines out of the 18kPV from the GRID lugs and tie them back into 3 lines that I previously disconnected.

I've included a few pics of my current setup to make things easier.

 

[CRenner]

I don't think I am understanding this!
The panel on the pole is the main disconnect. That feeds the house and the solar?
Where is the shop fed from?
Is the 18kPv for backup? Why use the generator lugs? Doesn't it have an AC in connection?

 

[Siamac]

 

[CRenner]

I think I figured it out.
The AC out would power the shop, the AC in from the main by way of the combiner box and the solar on the generator in.
Is that correct?
Does the 18kPv do frequency shifting to shut down the solar?

 

[thepetersms]

I don't think I am understanding this!
The panel on the pole is the main disconnect. That feeds the house and the solar?
Where is the shop fed from?
Is the 18kPv for backup? Why use the generator lugs? Doesn't it have an AC in connection?

The panel on the wooden pole is the main disconnect that goes to my house. It has a 100amp breaker in it that I believe is called a backfed breaker. It goes to my solar array meter and panel.
The shop is not fed from anywhere yet. I want to tie the solar into the shop 18kPV inverter the feed it back to the grid so I can sell excess solar I'm not using to charge the batteries.
The 18kPV will be the primary source of power for the shop with 2 PowerPro wall mount batteries. I can use the generator lugs to do AC coupling to keep my setup the way it is.

 

[Markus_EG4]

Yes it does its 1741sb compliant. And all you have to do is combine your ac couple system and bring back 1 set of wire to the gen port to have this function properly

 

[thepetersms]

I think I figured it out.
The AC out would power the shop, the AC in from the main by way of the combiner box and the solar on the generator in.
Is that correct?
Does the 18kPv do frequency shifting to shut down the solar?

Yes that's correct

 

[thepetersms]

Yes it does its 1741sb compliant. And all you have to do is combine your ac couple system and bring back 1 set of wire to the gen port to have this function properly

But then don't I have to run a set a wires from the 18k in the 'GRID' lugs back to that meter under my solar array. It has to send the power back to the grid somehow

 

[zanydroid]

I believe I would disconnect the 3 lines coming into my solar electric panel at the top (those lines come from a 100amp feeder breaker at my main panel)
Run 3 new lines back to my shop and into my 18kPV into the Generator lugs. Then run 3 more lines out of the 18kPV from the GRID lugs and tie them back into 3 lines that I previously disconnected.

This sounds more than needed.

1) the neutral in the combiner is just for the controls/monitoring in there. You may be able to run just hots back to your house. And have the controls/monitoring powered from grid. This of course has consequences that you have to tradeoff

2) you should have electrical already from your house to the meter. Unless something weird is going on with your wiring. Why not backfeed through this path?

Show us photos and SLD (IMO more polite to do this because it saves people trying to help you from mental strain) on the on-grid topology in the building with the 18kpv. Critical things are ampacity of conductors, breaker sizes, busbar ratings.

 

[zanydroid]

Ah is the shop off grid right now/no existing service? I don’t see breakers for it. Or it’s too small for your 5 enphase branches.

You can probably consolidate down to L/L, L/L/N, G to the shop. However pulling the extra neutral (L/L/N, L/L/N, G) will de-risk messing up the optimization of dropping a conductor/future proof, and the extra length of #1 Al THHN is probably not that much money, less than $1 per foot

You will need to make the solar panels go through the production meter on the way to your 18kpv.

 

[thepetersms]

This sounds more than needed.

1) the neutral in the combiner is just for the controls/monitoring in there. You may be able to run just hots back to your house. And have the controls/monitoring powered from grid. This of course has consequences that you have to tradeoff

2) you should have electrical already from your house to the meter. Unless something weird is going on with your wiring. Why not backfeed through this path?

Show us photos and SLD (IMO more polite to do this because it saves people trying to help you from mental strain) on the on-grid topology in the building with the 18kpv. Critical things are ampacity of conductors, breaker sizes, busbar ratings.

See attached drawing that I did. Hopefully this makes sense

 

[thepetersms]

Ah is the shop off grid right now/no existing service? I don’t see breakers for it. Or it’s too small for your 5 enphase branches.

You can probably consolidate down to L/L, L/L/N, G to the shop. However pulling the extra neutral (L/L/N, L/L/N, G) will de-risk messing up the optimization of dropping a conductor/future proof, and the extra length of #1 Al THHN is probably not that much money, less than $1 per foot

You will need to make the solar panels go through the production meter on the way to your 18kpv.

Correct, the shop is off grid with no service right now. Here's a photo of the 18kPV and PowerPros along with the breaker panel in the shop. Then an outside view to my array.

 

[zanydroid]

Thanks, these pictures help a lot. I'm jealous of your clean setup.

This picture lines up with my updated view in post #10.

So your solar meter might be on the wrong side. You should check with your POCO. If you put it between grid and 18kpv you will only see the production that is exported (maybe that's what your POCO wants) (**). If you put it between 18kpv and combiner panel you will see PV production minus whatever power your monitoring hardware inside combiner panel draws. If you put it between combiner panel and microinverters you are guaranteed to only see PV production (*). To me (*) makes the most sense if POCO cares about what you produce, regardless of how it is consumed. (Note that this is different from what I previously wrote). I believe your current setup has the conductors going through the meter AFTER combining. Which is probably fine, your 120V management stuff is probably only eating 10W, and you have a smart meter that will be smart enough to not overcount that at night.

(**) makes sense to do if you want to get credit for exporting battery power at specific times of the day. Otherwise with (*) you get credit for production during solar hours, which are usually lower export credit.

The production meter location is the basis of SREC and is also used for some net metering + storage schemes, where they want to make sure you do not export more than what you produce.

That said, if the production meter is there because you don't have a smart meter at the service to compute net production, then where you have it is probably the right place.

Regarding the 18kPV are those close enough for the standard parallel power cables to reach (assuming you need to bus together both batteries and do this by cross wiring)

 

[thepetersms]

Thanks, these pictures help a lot. I'm jealous of your clean setup.

This picture lines up with my updated view in post #10.

So your solar meter might be on the wrong side. You should check with your POCO. If you put it between grid and 18kpv you will only see the production that is exported (maybe that's what your POCO wants) (**). If you put it between 18kpv and combiner panel you will see PV production minus whatever power your monitoring hardware inside combiner panel draws. If you put it between combiner panel and microinverters you are guaranteed to only see PV production (*). To me (*) makes the most sense if POCO cares about what you produce, regardless of how it is consumed. (Note that this is different from what I previously wrote). I believe your current setup has the conductors going through the meter AFTER combining. Which is probably fine, your 120V management stuff is probably only eating 10W, and you have a smart meter that will be smart enough to not overcount that at night.

(**) makes sense to do if you want to get credit for exporting battery power at specific times of the day. Otherwise with (*) you get credit for production during solar hours, which are usually lower export credit.

The production meter location is the basis of SREC and is also used for some net metering + storage schemes, where they want to make sure you do not export more than what you produce.

That said, if the production meter is there because you don't have a smart meter at the service to compute net production, then where you have it is probably the right place.

Regarding the 18kPV are those close enough for the standard parallel power cables to reach (assuming you need to bus together both batteries and do this by cross wiring)

I'll keep the meter where it's at as that's the way the system was setup by the solar installer from previous owners.
in regards to the 18kPV, yes it's all on one wall in the shop and I got the batteries connected to the inverter today.
I'm a bit confused when you say "You can probably consolidate down to L/L, L/L/N, G to the shop."
Can you break that down barney style for me please. And where do I tie those lines into the combiner box outside under the solar? Do I bring it right to the lugs at the top of it where the current 100amp lines go into it from production meter?

 

[thepetersms]

Thanks, these pictures help a lot. I'm jealous of your clean setup.

This picture lines up with my updated view in post #10.

So your solar meter might be on the wrong side. You should check with your POCO. If you put it between grid and 18kpv you will only see the production that is exported (maybe that's what your POCO wants) (**). If you put it between 18kpv and combiner panel you will see PV production minus whatever power your monitoring hardware inside combiner panel draws. If you put it between combiner panel and microinverters you are guaranteed to only see PV production (*). To me (*) makes the most sense if POCO cares about what you produce, regardless of how it is consumed. (Note that this is different from what I previously wrote). I believe your current setup has the conductors going through the meter AFTER combining. Which is probably fine, your 120V management stuff is probably only eating 10W, and you have a smart meter that will be smart enough to not overcount that at night.

(**) makes sense to do if you want to get credit for exporting battery power at specific times of the day. Otherwise with (*) you get credit for production during solar hours, which are usually lower export credit.

The production meter location is the basis of SREC and is also used for some net metering + storage schemes, where they want to make sure you do not export more than what you produce.

That said, if the production meter is there because you don't have a smart meter at the service to compute net production, then where you have it is probably the right place.

Regarding the 18kPV are those close enough for the standard parallel power cables to reach (assuming you need to bus together both batteries and do this by cross wiring)

Here's the diagram from the EG4 18kPV manual. Follow the GRID and GEN ports from the inverter.
From that diagram it appears to me that I have everything I need in place already except the lines to and from the shop of course.
I'm just confused where and how I connect it

 

[zanydroid]

I'm going to have to draw this out on your pictures, and it takes longer for me to bust out and return a drawing program than to write, so it might be a while before I can get to it.

You are correct that you just two circuits running from shop to the array.

 

[zanydroid]

How big is that conduit coming out of the floor? It looks a little small for 2x 100A circuits, and those wires will need to be increased about 20% in size to compensate for having two circuits in there.

You will also need to check with EG4 how to configure the inverter to guarantee that it never pushes more than 80A (combined) between the AC coupled panels and the battery inverter. Since that is the max the 100A wiring to your grid connection can take.

 

[thepetersms]

How big is that conduit coming out of the floor? It looks a little small for 2x 100A circuits, and those wires will need to be increased about 20% in size to compensate for having two circuits in there.

You will also need to check with EG4 how to configure the inverter to guarantee that it never pushes more than 80A (combined) between the AC coupled panels and the battery inverter. Since that is the max the 100A wiring to your grid connection can take.

The conduit coming out of floor is 2 inch. When I planned the building I was going to use grid power and not my solar. If I have to run another conduit line into the side of the building, thas fine.

Yes I can limit the amount of power going back to the grid from the inverter

 

[thepetersms]

$459 for 240ft of 2-2-4-6 aluminum wire. It's a little over 100 feet one way.
whew... Maybe I'll just run new PV lines at the array and bring them back into the inverter. It would be cheaper and I already have all the 10awg cable and IP67 connectors to make new connections at the solar panels to string them together. But no matter what option I do, I still need to send back one set of lines to the production meter, from the GRID lugs on the inverter.

 

[zanydroid]

$459 for 240ft of 2-2-4-6 aluminum wire. It's a little over 100 feet one way.
whew... Maybe I'll just run new PV lines at the array and bring them back into the inverter. It would be cheaper and I already have all the 10awg cable and IP67 connectors to make new connections at the solar panels to string them together. But no matter what option I do, I still need to send back one set of lines to the production meter, from the GRID lugs on the inverter.

I see $325/500ft of #1 THHN. Wire is sort of a "pay once use it for decades" thing.

Going to 500VDC will save 1/2 size on the wire, however you will still need two circuits to hit 18k on the inverter. Maybe just send 12K to the 18kpv. You can also 1/2 the size of the AC back to the grid. It won't mean 1/2 the cost though.

You can also choose to send part of the array through 18kpv and the rest directly to grid. It depends on if you think you can use all that electricity in the shed, otherwise you're losing money b/c of not exporting it.

There's a couple ways to avoid a return line, although the return line gives you the most options. You can also choose to reconfigure it later (you should probably flag the direct bury or conduit nicely though, in case you need to dig again. Don't want to hit it).

For instance you can send solar to grid without going through the inverter. This effectively makes the 18kpv a backup battery for the shop. Sometimes people with batteries in outbuildings reduce the size of the feeder to those buildings. Since the inverters can provide the surge loads from the battery. And then overnight (or whenever the building isn't being used) the battery slowly charges to full again. What you lose here is the ability to form a grid when the power is out (You can still do this by rewiring in a power outage but I'm not sure there's a 100% safe way, you can start a thread though to see if someone can advise a safe way. The tough part is keeping grid vs solar array energy straight). Is that important to you?