Ampster
Renewable Energy Hobbyist
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.
Limitation to AC coupling with EG4 18K, help required...
- Thread starter Vince Mex
- Start date
1201
Solar Wizard
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
New Member
Or the OP just doesn't understand.
1201
Solar Wizard
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 !
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1201
Solar Wizard
You're welcome but it's annoying when someone gives you an answer and you say-well ss said something else.
I appreciate your position and with that large of a purchase you should 100% go with what ss says and don't second guess it or confuse yourself by asking what others think, because at that point you're wasting your time- and ours.
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Kim Scott
New Member
Adding another inverter could be potential solution but need to consider the cost as well. It might be helpful to consult a professional.
FilterGuy
Solar Engineering Consultant - EG4 and Consumers
Yes.... depending on the configuration. For all of the AC coupled power and most of the 12KW inverter power to be pushed to the grid, the system would have to be configured to force the backfeed. (This could be done as part of peak shaving). However, in many configurations, the inverter would not produce any power from the battery and only backfeed the grid if the DC-coupled PV is producing power that is not needed by the loads or batteries.
As I said in an earlier post, the 18Kpv is highly configurable so there is often no unqualified answer to these scenarios.
You always have the option of wiring a critical loads panel. Since you can only export 10kw, the 70amp breaker should be plenty. (requirement 225 amp bus) This would allow you to balance the loads to the capacity of the 18Kpv.
The advantage of wiring the 18Kpv like Millsan1 rather than a critical loads panel, is you get to pick which loads get to stay on in a power outage. Example turning off the breakers on your panel that are not needed until you reach load balance with the 18Kpv.
The advantage of wiring the 18Kpv like Millsan1 rather than a critical loads panel, is you get to pick which loads get to stay on in a power outage. Example turning off the breakers on your panel that are not needed until you reach load balance with the 18Kpv.
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Case 1 - On- Yes, you can draw from the grid, up to 200 Amps
Case 1 - Down- You are at max, since AC Couple is only giving 3. 3+12 from 18 = 15, so you are OK.
Case 2 - 8kw- Load is fed, excess goes to batteries. When batteries get to a set point you control, the AC Couple will be ramped down. In my case I have it set to 95% SOC. When batteries reach 95% SOC, AC Couple will be turned off via frequency shifting. When batteries reach 100%, solar will feed your loads, there is no excess, as loads pull power, solar does not push power.
Case 2 - 6KW - Yes, you can pull from the grid up to 200 amps.
Long story short, the only practical limitation is the 12 KW inverting from the 18K, in an grid down situation. But that is a lot of juice, and if it is during the day, you can still get more from the AC Coupled system.
On grid, there is really no meaningful limit. Same deal, 18 can only invert 12K, but AC Couple can provide up to an additional 21 and the grid can provide 200 Amps.
I understand your concerns, but please understand that the info given my the EG4 person was slightly inaccurate and needlessly confusing.
SignatureSolarJess
Customer Experience Excellence Ambassador
- Joined
- Nov 21, 2022
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Hi @Vince Mex I'm so sorry you've had to wait a week for a response! We are up to date with emails and there should not be a week's wait time! I'd love for you to DM me your email address so I can look into this.
SS just answered me today and yes GRID, Inverted power from batteries and or directly connected solar array to the 18k AND AC coupled power are available all together when grid is ON. When grid is down the limit is 12 kw from the 18 k added to the AC coupled array.....like Milsan1 and many other explained here.
Thanks to them !
SolarCzar
New Member
@SignatureSolarJess So what's the settings on the 18K's? I've been talking for days with EG4 and SS reps and they say my situation is "unique" and not making any progress. I also messaged @millsan1 to see if he would be so kind as to share his settings.
Here's my problem...I have 2x 5kW Fronius inverters on the GEN port of each of my 18K's. I have followed the book on AC Coupling setup, but it's not providing power to the GEN port whereby the grid-tie Fronius inverters would not believe they are in "islanding" mode and sync up. I have 10kW on 2x Fronius, and 30kW on my 2x 18K's. When sun is shining, I want to power house loads, charge batteries, and sell excess back to the grid (I have been net-metering for 15yrs). Sun goes down...run off batteries until discharge limit (what % is best?), then pull back from grid.
I've gone through 4x csr's at SS and EG4, and they say my ask is "unique". I know that can't be. Any help?
Luxpower_Gilbert
Luxpert @Luxpower USA Team
DM me your inverter sn.
SolarCzar
New Member
Hey guys, disregard as EG4 team worked behind the scenes and determine that I had a stuck relay that was not allowing the values to update. Working solid now.
wheisenburg
Owner Operator of Heisenberg Electric
You may be misunderstanding them. A two pole relay simply means that it switches two wires at the same time. Relays designed for 240 volts are 2 pole because there are two hot leads and you have to switch both of them. It has nothing to do with how many of the relays can be closed at the same time. When you are running AC coupled and on grid all three of these relays will be closed.
The 12KW is the inverter limit. So your MTTP limit is 18 KW. That is how much solar you can push into your DC bus / Batteries. The 12 KW is how much DC power can be converted to AC. When running on grid, I am not seeing any issues here. You can use all the power you like up to the 200 amp limit. Now there is an export limiter that allows you to limit how much power you export back to the grid. It seems like there was a recent update to increase that limit because it wasn't big enough for people that had AC coupled.
When off grid then you will be limited to 12KW plus what ever power is instantaneously available from your AC coupled array. In other words don't use much more than 12KW unless you want to overload your system every time a cloud goes by.
SolarCzar
New Member
Ok, so that put my mind in a bat slide. So I’ve got 15kW on the primary MPPT’s and 5kW on the AC-coupled side, times two inverters for a total of 40kW. So in a grid outage situation, I will only have 24kW of solar going to the batteries/consumption? Hmmm? I think I’ll still be ok, but definitely something to watch.
I have 2x Fronius 5kW inverters with each being on the AC-Coupled leg of the 2x 18kW inverters. So here’s the big question I posed to EG4…
Can I put both Fronius inverters on 1x 18kW EG4 (10kW, which would total 25kW and well within the 31kW limit) and attach my 12kW Generator on the other inverter? So in a prolonged outage, my batteries would equalize the load demand and the generator would drive recharging/load.
The problem is I run the EG4’s in parallel. So in a prolonged outage I would need to remember and have it posted to turn off AC-Coupling and turn on Generator functionality. I thought I may wire up a sub panel with an inter-lock and notes to make the changes in software.
Thoughts or a better way to do it?
SolarCzar
New Member
One more question. Here’s my month end…
I’m trying to discern how I’m reading these values for the month of May relative to my net metering aspect. Is it…
1) I’ve produced 2235 solar, of which 783 went to battery & 608 export to grid. So of the 2766 consumption, my net metering impact will be (2766 - 2235 - 608 = -77)
Or is it…
2) 2766 Consumption minus 2235 Solar minus 783 battery minus 608 export = -860 net?
I’m trying to discern how I’m reading these values for the month of May relative to my net metering aspect. Is it…
1) I’ve produced 2235 solar, of which 783 went to battery & 608 export to grid. So of the 2766 consumption, my net metering impact will be (2766 - 2235 - 608 = -77)
Or is it…
2) 2766 Consumption minus 2235 Solar minus 783 battery minus 608 export = -860 net?
jjww
Stuck in PG&E Land
How does the 200 amp passthru work into that 50 amp to load lugs limitation?
wheisenburg
Owner Operator of Heisenberg Electric
Note:
The Minimum Battery Power limit for this configuration should be 2 * Max PV output. This will allow excess AC coupled power to be managed without causing voltage spikes in the DC system. So your batteries should allow for 80KW. So if you are using batteries that allow 100 amps you should have 16 of them. The rest of your DC design should allow for 800 amps. So probably parallel 4/0 cables, 1 for each inverter. This would meet the cabinet rating for 4/0. Electrical code in USA would actually require 500 mil. And at least an 800 amp rated DC bus.
When we deal with electricity we deal with "Power" and "Power Limits". Power is the rate at which energy is produced. That will be either watts or KW (kilowatts). Energy is Power over time. If I use 1 KW for 1 hour I have used 1 KWH. So these system have limits on Power which is the maximum rate a which they can use energy. Batteries have limits on both power and energy. Maybe the max load on a battery is 100 amps or 5 KW. If the battery can support this load for 1 hour, then it can provide 5KWH of energy.
First you need to understand this. In DC coupled solar, the power first flows into the DC bus / Batteries. These 18K units allow up to 18KW each to flow into the batteries through the MPPT chargers. The MPPT charger is one component of the All-in-one unit that we often refer to as an Inverter. In your case the MPPT chargers allow up to 30KW of DC to be harvested. I don't know the exact figures for your area, but that should allow you to capture up to 30 * 5 = 150 KWH on a typical sunny summer day. Your 10 KW AC coupled would add another 50 KWH for a total of 200 KWH. These numbers are probable conservative. That is how much "Energy" your system will produce in a day. If you are on grid this excess energy can be exported. The 10 KW of AC coupled will supply you house first and then flow to the grid if not used.
Now before you can Export or Use energy from the DC system, it will need to be converted into AC. It is OK and in fact desirable that you can harvest power faster than you can use that power. Your system will only harvest power for 10-12 hours a day. Also your peak power production is only about 2-3 hours a day. The system will need to supply power to the loads for 24 hours a day. When on grid this is not problem, you export the excess and then draw it back again during the night. You can also do Self Consumption where you charge your batteries during the day, and then use that energy at night.
So this pretty much covers the way these system capture energy. So now lets look at the consumption side.
There is a component piece of hardware in your unit called an "Inverter / Charger". We have gotten used to referring to any All-In-One unit as an "Inverter", but really these devices have a bunch of hardware devices bundled into them. So when I say "Inverter / Charger" here I am not talking about the entire box, but only the portion that turns DC power into AC power or AC into DC. This Inverter / Charger is what converts the DC in the batteries or coming in from the MTTP chargers into useable AC power. With two Inverter / Chargers you will have 24KW plus what ever you get from your AC coupled power available to use. 24KW is a LOT of power. In my house my usage is typically less then 1 KW unless there is a major appliance of some sort turned on. Even my AC only draws around 2KW. This 24KW limit is going to be an issue only if you are off grid and trying to use battery power or if you are on grid and pulling power out of the batteries to export it. Since your system can only produce about 150 KWH in a day, you could export all that power to the grid in just 6 hours. When on grid you can still pull as much power as you need from the grid.
So lets say we are off grid. Our load is drawing 15 KW. Our AC coupled is producing 7 KW. The inverters will draw 8KW of power from the batteries to produce the gap between the loads and the 7 KW the AC coupled is producing. As long as your batteries are charged, the 24 KW will always be available from the inverters. The AC coupled power will vary throughout the day and depend on cloud cover. Now lets say our big AC units shut down and our load drops to 3 KW. The AC coupled is still producing 7KW. Now the Inverter / Charger switches to its charger mode. It will push 4 KW into the batteries. These devices either draw power from the battery or push power into it. They can't do both at the same time. The inverter can manage the output of the AC coupled array through frequency shifting, but this is a slower and less precise process than the one used by the MPPT chargers.
So when you are off grid and the batteries are full, the Unit may disconnect the AC coupled power since it is harder to manage and not needed to keep the batteries full. That is why they put this on the Gen input. They can use the relay to shed the excess power when there is no more room in the batteries. So the fact is when off grid you can only count on having the 24KW that is available from the inverter / charger. The unit will continue to harvest solar on the MTTP chargers at whatever rate it required to keep the batteries topped off. That will mean you have to manage large loads like air conditioners, electric driers, and water heaters so they do not exceed 24KW. If you think you will spend a lot of time off grid, then you really should be looking at gas or propane appliances. A gas water heater and drier costs a little more than an electric. A gas stove about the same. The inverters and batteries required to power these units off grid costs thousands. Load reduction is much cheaper than buying bigger inverters. Another thing you will want is a soft starter for any large motors such as air conditioner compressors. The starting surge for these motors is often 5-10 times the running amps. So if you have a large AC with 10 running amps. It can spike to 100 amps when starting. That would use up all the available power from your inverters. These soft starters might lower that number to 30-40 amps.
Generally, your system will work better off grid when your AC coupled < DC coupled. In your case the DC is much larger than the AC coupled, so you are in good shape there. Your total power output from solar is 40KW. 30KW goes through the MTTP chargers and 10KW goes through the Inverter/Charger device. The Total AC coupled must be less than the Inverter / Charger rating, so 10K < 24K. That should be fine.
The Minimum Battery Power limit for this configuration should be 2 * Max PV output. This will allow excess AC coupled power to be managed without causing voltage spikes in the DC system. So your batteries should allow for 80KW. So if you are using batteries that allow 100 amps you should have 16 of them. Your DC design should allow for 800 amps. In other words the batteries need a reserve that will not actually be used. So at least parallel 4/0 cables, 1 for each inverter. This would meet the cabinet rating for 4/0. Electrical code in USA would actually require 500 mil. And at least an 800 amp rated DC bus.
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wheisenburg
Owner Operator of Heisenberg Electric
I would be careful here. I am not certain about what things can be separately configured when the inverters are setup in parallel mode.
First there are two modes that an inverter can be in. Grid forming mode where the inverter generates a wave form and all other devices will lock onto that wave and follow it. Or it can be in grid following mode where it looks at an incoming signal and matches that.
So when a port is used as an actual generator port, the the inverter must go into grid following mode when the generator connects. When the grid is down however the inverter will be in grid forming mode. The gen port when it is configured to AC couple is supplying a signal to the port and expecting the devices on that port will be in grid following mode. When you are running inverters in parallel, I don't think it is possible to have one of them in grid following mode while the other is in grid forming mode. Normally you would configure these identically and connect the inverters in parallel to either a generator or an AC Coupled array, but not both at the same time.
I think a better way to do this is with the Eg4 chargeverter. They will handle 5000 watts so you could get 2 of them. Or you could just use 1 and run it longer. These go straight to the DC bus, so you can run it in parallel with your AC coupled.
If you use the Gen port, then in order to charge your generator needs to first supply all your loads. Then only the left over current can go to the batteries. The AC coupled won't be available. You don't want to run the generator flat out. So say you set it for 8KW. If your loads are more than that, you will be going backwards. With the chargeverter you just set it to supply a certain amount of watts say 4KW and run it as long as needed to charge. The rest of the system including the AC couple will continue supply your loads as normal.
This will work better and have less chance that a configuration error will cause damage to equipment.
paosin
New Member
Hello - how do you set grid assist up?
Hey guys, I know that this is an old topic but I've been working for the last 4 months (on very little spare time) with SS in order to get my 18K to work ON-GRID with my AC coupled arrays, so that I can still keep selling power back to my utility in a controlled way via the 18K.
I found a post earlier last year from @millsan1 with the very setup that I'm trying to accomplish. I can only get this to work in OFF-GRID mode. Is anyone else been able to set this up and can help with the correct settings. Picture attached
Thanks
I found a post earlier last year from @millsan1 with the very setup that I'm trying to accomplish. I can only get this to work in OFF-GRID mode. Is anyone else been able to set this up and can help with the correct settings. Picture attached
Thanks
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