EG4 18kPV AC Couple Questions

[CRenner]

How many amp's are the IQ7's rated for?
I have IQ8+'s and they are rated for 1.21 amps each. Times 48 is 58 amp's.
That is close to 25%

 

[wheisenburg]

Thanks for the reply. I will look into that for sure regarding the excess power coming in from micro inverters.

Regarding the backfeed breaker, I was actually just researching that. It seems the current 100amp breaker that's in right now is not correct given my main panel is only rated for 200amp bus bars so it's far over the 125% rule. I'm royally confused how it's not melting anything given all 48 micro inverters are back feeding the grid.
The solar was installed by the local electric power company with the previous owners of the house 2 years ago.

Most houses have electric panels that are way over sized for the actual amount used. I almost never use more than 15,000 watts (62 amps). A two hundred amp service can supply 48,000 watts. The problem is that in theory with the 200 amp incoming breaker and 100 amps of back feed running you could draw 300 amps out of the panel before the main breaker opened. A big house in a hot area with 3*5 ton A/Cs running and a row of arc welders lined up might get you there.

One thing about having the micros running is that they actually reduce the power you pull in from the grid. So if you producing 60 amps, while consuming 100 amps, you are actually only importing 40 amps in off the grid. That means in the real world, your incoming wires are not stressed at all.

You do have two batteries, what is the amp rating per battery? It looks like sol arc 15 K can handle 19,500 watts of AC coupled.

 

[thepetersms]

How many amp's are the IQ7's rated for?
I have IQ8+'s and they are rated for 1.21 amps each. Times 48 is 58 amp's.
That is close to 25%

I have the IQ7+. They're rated at same amps

 

[thepetersms]

Most houses have electric panels that are way over sized for the actual amount used. I almost never use more than 15,000 watts (62 amps). A two hundred amp service can supply 48,000 watts. The problem is that in theory with the 200 amp incoming breaker and 100 amps of back feed running you could draw 300 amps out of the panel before the main breaker opened. A big house in a hot area with 3*5 ton A/Cs running and a row of arc welders lined up might get you there.

One thing about having the micros running is that they actually reduce the power you pull in from the grid. So if you producing 60 amps, while consuming 100 amps, you are actually only importing 40 amps in off the grid. That means in the real world, your incoming wires are not stressed at all.

You do have two batteries, what is the amp rating per battery? It looks like sol arc 15 K can handle 19,500 watts of AC coupled.

Yes I have 2 eg4 power pro wall mount batteries. They're 48v 280Ah each.
Here's what they say about AC Coupled mode straight out of the manual-
"After the AC couple function is enabled: When the grid is on, the GEN terminal is connected to the GRID terminal inside the inverter. In this case, the hybrid inverter will bypass the interactive inverter AC to the GRID and LOAD. Any remaining energy will be exported to the grid. When the grid is off, the GEN terminal is connected to the LOAD terminal inside the inverter. In this case, the hybrid inverter will work as a power source for the grid-interactive inverter to synchronize and feed power to the micro-grid. The loads will be supplied by solar power first. If solar panels are generating more power than load consumption, the excess solar power will be stored in the batteries. When solar power exceeds the sum of load power and max battery charging power (e.g., when the batteries are nearly full), the inverter will signal the grid interactive inverter to reduce power via the frequency shifting, power-reduction mechanism, thus maintaining the balance of generation and consumption of the micro-grid system."

I'm confirming with EG4 about this as well.
I guess my only confusion at this point is what I do with that 100amp back feed breaker. Do I leave it in there or downsize it to say a 60 or 70amp?
In my setup, my shop will be ran completely off the inverter and batteries. It's not going to pull anything from the grid. The only function the "grid" lugs will have is selling excess power back to the gride when the batteries are full, so I won't be pulling 60,70, or 100amps (whatever size backfeed breaker) So in theory I wouldn't be sending anymore power back to the grid than I currently am now through that 100amp breaker.

 

[wheisenburg]

They're 48v 280Ah each.

The important thing is not the capacity (KWHs), it is the ability to handle the charging AMPs. They are advertised as handling 200 amps of charge current. So you should be able to push 400 amps into the batteries. With the IQ7+ you will have 283 amps of charging current. On paper this should work, but it sounds like panels are ground mount, you are considering converting them to DC coupled. Both technologies will work well when grid tied. AC coupled can work OK as emergency backup power, but it does seem to have a reputation for being difficult. DC coupled can more precisely control current output. With AC coupled they are using both frequency shifting and cycling the gen relay on and off to control charging to the battery. This probably works better on the EG4 than on the Schneider that lacks this feature. For anyone that is truly running Off Grid, I would never recommend AC coupled.

I have been working on this for 1.5 years. Enphase finally released a firmware update that allows the inverters to produce power when AC coupled. I still want to increase my batteries from 3 to 6. They can handle 300 amps of charging current, but I would be more comfortable if I upped that to 600 amps. Right now my inverters can actually trip the batteries BMS when there is a surge such as an A/C compressor starting.

I might try adding some logic to control my PV contactor using relays and the control wiring ports built into the inverters. Because I have a generator input, I use a contactor which is basically a giant relay to switch the generator and PV in and out. You can't run PV and Gen in parallel.

 

[zanydroid]

I guess my only confusion at this point is what I do with that 100amp back feed breaker. Do I leave it in there or downsize it to say a 60 or 70amp?

Was the question around (1) existing conditions or stacking a hybrid in front of the microinverters and feeding both into the panel (2)

(2) Unless you can confirm with EG4 that it can reliably throttle on grid export from AC couple + its own inverter, you should add AC couple size + own inverter. That is the worst case if inverter and AC couple are both pushing 100%, and load under the AIO drops out.

Pretty sure there is language in the manual saying export control does not work when AC coupling.

(1) With regards to what you have right now. You can usually (depends on the governing code section from 705.12) size the busbar calculations based on the output current of the inverter, not the breaker size. I think 3 out of 5 cases are based on inverter output current and the rest are breaker size.

As long as the breaker is 125% of the current from inverter and the wire protected by the breaker is that ampacity or bigger it should be fine code wise.

Dropping the breaker size is probably less confusing if the only circuit on that breaker is the solar array. It guards against someone adding too much solar later, not doing the calculations, and exceeding the busbar.

If that breaker has both loads and array then you need to check whether there are loads that need the 100A capacity

 

[thepetersms]

Was the question around (1) existing conditions or stacking a hybrid in front of the microinverters and feeding both into the panel (2)

(2) Unless you can confirm with EG4 that it can reliably throttle on grid export from AC couple + its own inverter, you should add AC couple size + own inverter. That is the worst case if inverter and AC couple are both pushing 100%, and load under the AIO drops out.

Pretty sure there is language in the manual saying export control does not work when AC coupling.

(1) With regards to what you have right now. You can usually (depends on the governing code section from 705.12) size the busbar calculations based on the output current of the inverter, not the breaker size. I think 3 out of 5 cases are based on inverter output current and the rest are breaker size.

As long as the breaker is 125% of the current from inverter and the wire protected by the breaker is that ampacity or bigger it should be fine code wise.

Dropping the breaker size is probably less confusing if the only circuit on that breaker is the solar array. It guards against someone adding too much solar later, not doing the calculations, and exceeding the busbar.

If that breaker has both loads and array then you need to check whether there are loads that need the 100A capacity

I think I got that part figured out. If I go the AC Coupled route I'll be sending in 58 amps from the IQ7+ micros. Not sure why they put 100amp breaker in when they did the install, maybe that's all he had on the truck.
I've got an email out to Signature Solar and EG4 confirming the grid shut down feature in the event the grid goes out and the batteries are full. I'm also asking them about limiting/stopping grid input to eliminate any over consumption concerns on my main panel.
My setup is a bit different from others as my house is ran completely on grid. The inverter and batteries are in place to provide 100% to my shop and office so it's actually off grid. I only want to tie the grid back into it so I can sell excess solar back not being used to charge them batteries.
My future plans are to get another 18kPV and 2 more batteries, parallel them all together and then run it into my main panel for the house

 

[zanydroid]

I've got an email out to Signature Solar and EG4 confirming the grid shut down feature in the event the grid goes out and the batteries are full.

I don’t understand here (IE it’s not a question I would ask them)

If the grid goes out a hybrid inverter should disconnect internal grid relay to prevent backfeed into down grid from keeping its inverter and AC coupled solar. That’s a fundamental requirement of UL1741

The part that is an open question is what the AC rating counts as wrt busbar sizing when a subpanel can be fed on grid and from hybrid and AC couple. Theoretically they can cut the inverter quickly enough to get down to 58A of AC coupled within 10-20ms. The question which only they know would be how the firmware actually works in practice.

 

[thepetersms]

I don’t understand here (IE it’s not a question I would ask them)

If the grid goes out a hybrid inverter should disconnect internal grid relay to prevent backfeed into down grid from keeping its inverter and AC coupled solar. That’s a fundamental requirement of UL1741

The part that is an open question is what the AC rating counts as wrt busbar sizing when a subpanel can be fed on grid and from hybrid and AC couple. Theoretically they can cut the inverter quickly enough to get down to 58A of AC coupled within 10-20ms. The question which only they know would be how the firmware actually works in practice.

Well that seems to be a concern for many people so I figured I would ask to get a straight answer instead of 10 different answers on the interwebs

EDIT- I got a response from Signature solar. They said if grid export is turned off and the batteries are charged, the unit will clip the incoming power and it will just not be used as if it didn't exist.

 

[wheisenburg]

Yes I have 2 eg4 power pro wall mount batteries. They're 48v 280Ah each.
Here's what they say about AC Coupled mode straight out of the manual-
"After the AC couple function is enabled: When the grid is on, the GEN terminal is connected to the GRID terminal inside the inverter. In this case, the hybrid inverter will bypass the interactive inverter AC to the GRID and LOAD. Any remaining energy will be exported to the grid. When the grid is off, the GEN terminal is connected to the LOAD terminal inside the inverter. In this case, the hybrid inverter will work as a power source for the grid-interactive inverter to synchronize and feed power to the micro-grid. The loads will be supplied by solar power first. If solar panels are generating more power than load consumption, the excess solar power will be stored in the batteries. When solar power exceeds the sum of load power and max battery charging power (e.g., when the batteries are nearly full), the inverter will signal the grid interactive inverter to reduce power via the frequency shifting, power-reduction mechanism, thus maintaining the balance of generation and consumption of the micro-grid system."

I'm confirming with EG4 about this as well.
I guess my only confusion at this point is what I do with that 100amp back feed breaker. Do I leave it in there or downsize it to say a 60 or 70amp?
In my setup, my shop will be ran completely off the inverter and batteries. It's not going to pull anything from the grid. The only function the "grid" lugs will have is selling excess power back to the gride when the batteries are full, so I won't be pulling 60,70, or 100amps (whatever size backfeed breaker) So in theory I wouldn't be sending anymore power back to the grid than I currently am now through that 100amp breaker.

Three things:

1. While the statement that frequency shifting will be used to attempt to balance generation and consumption is true, it is not instantaneous and the PV inverters increment by 10% at a time. So you can vary a 14,000 array by 1400 watts at a time. It is also not instantaneous, depending on the hybrid setup and the inverter details, it could take 2 to 8 seconds to throttle down the micro inverters using frequency shifting. That is why for AC coupling, you always want your battery power rating (power is an instantaneous rating like watts, energy is power over time like KWHs) to be at least 100%. Your batteries power rating is 200 amps * 2 * 50 volts = 20,000 watts. You should be fine. In addition the EG4 controls the gen connection. They allow you to set this up for say 80% to 90% SCO. This means until the battery SOC drops to 80% they won't turn on the gen connection. Once the batteries have charged back to 90%, they will turn the gen connection back on. This prevents trying to send power to batteries that are nearly full. So I believe that should be fine so long as your IQ7+ inverters actually work when AC coupled. There are other people that have that working. The IQ8 series was having problems which now seem to be fixed.
2. On the panel issue, I have one question. Is the power for the home routed through this panel? It is possible to use the top of the bus as the supply for the panel and the bottom of the bus as a source for another panel. For example I have a "Grid" panel in my system that is tied to the grid. If I have loads that I don't want powered in an outage I can place them there. The bottom of the panel has lugs that are then routed on to Grid inputs on my inverters. So all the grid current for my inverters passes through the bus bars in the "Grid" panel. If that is the case then ideally you should make sure that the sum of the feeder breaker and the main breaker is < 240 amps. For the feeder you want the breaker and wires sized at 125% of your continuous load. So that would be 80 amps. You could replace the main breaker with a 150 amp breaker and you would be good.
3. If your house is not fed from the main breaker (does the house lose power if you turn that breaker off), you are good to go. If you look at the breakers in that panel other than the main and feeder breaker they total 120 amps. That means if the 100 amp feeder was maxed out supplying current, at most you could pull 120 amps from the other breakers. 100 amps would be supplied by the feeder and only 20 amps would be drawn in from the main breaker. So you have no way to overload your bus on this panel.