AC coupled recommendation?

[Ampster]

That cuts the 'other' solar support almost in half. And 80 amps at 48v is only 4kW, so that becomes woefully insufficien

I did not say that the M215s would not work. They are either on or off. They cannot modulate like 1741SA devices. As long as you have load in the form of battery charging and house loads they will pump out power.
I don't know why 4kW charging is inadequate for a 20 kWh battery? You know your friends needs and budget better than I. I charge my 42kWh battery at 3kW and never had an issue. My batteries are usually charged by Noon and my overnight loads are about 5 kWhs. I am at a higher latitude than Texas so I have less insolation.

 

[TexasSun]

Ampster,

The issue is that the old panels are putting out about 8kW. The new unit needs to be able to absorb all of that and dump it into the batteries.

An example. Hurricane hits, next day is sunny but no grid power. I flip all the right switches, and the new inverter is putting out 240Vac. Everything turns on (fridges, some lights, etc), let's say I'm drawing 20 amps @ 240Vac. All the old enphase inverters start turning on, let's say they're putting out 30 amps @240Vac. Great, 20 amps go into my load, and the new inverter sucks back the last 10 amps & dumps them into the batteries. @48vdc batteries, that's about 2400 watts or 48 amps. The 4kW charging is fine. However, let's say everything in the house turns off, and the old panels are still putting out 30 amps @240Vac (or 7500 watts). And the new panels, let's say they're putting out 4kW. The new unit needs to be able to conver at least all of the 7500 watts into charging. Ideally it also can dump the 4kW from it's panels, but they're less critical. The 7500 watts translates into about 150 amps @ 48Vdc. THAT is the problem. The batteries might only be at 50% charge, so the unit isn't going to start modulating the frequency because it wants to keep charging the batteries. Does that make sense?

 

[Hedges]

A battery inverter will adjust frequency according to how much power it wants. In my case it is programmed for 80A battery charging regardless of SoC (considerably less than what is available from AC coupled PV), and that is further reduced once CV charge mode is reached.

If the GT PV inverters do frequency-watts, their output will be nicely modulated. If some do not, they will switch on/off line with frequency shift and wait 5 minutes to reconnect after frequency is back within range.

 

[TexasSun]

Hedges, that is good to know. So, if the enphase start putting out more power than the new inverter can take, they'll frequency shift the units off. So that will protect most equipment, but it effectively is the same as turning off half the existing array (8kW to 4kW), unless things are just left turned on to use power (fans,well pump, etc). Not ideal, but an option.

I need to start a running list of options to keep things straight, with key features:

$7k Sol-Ark 12k... full featured
$3k Outback Skybox... 5kW output, only 4kW charging capable
$5k Sunny Island used (2x units)... full featured but no warranty
$3.2k Sigineer M12040D . 12kW inverting, 120A solar charger plus 100A charger. (please verify, but I take that to mean it will charge off it's own panels at a 6kW rate, and additionally charge from the enphase inverters at a 5kW rate at the same time?)

So far, I think the Sigineer is the best compromise for him. Other systems anyone recommends?

BTW, a bit of humor. Keep in mind, my place is all electric, two water heaters in the house and out in my shop, and a friend was visiting and had their RV plugged in. We managed to pop the main 200 amp breaker at the meter. Yup. Had to turn a few things off. But my place can be a huge load if everything is running. Lots of breakers will be switched off if the grid is down & I'm running off the solar+batteries.

 

[Ampster]

$3k Outback Skybox... 5kW output, only 4kW charging capable

This is a shameless plug from a Skybox user so take it with a grain of salt. You never answered my question why you considered 4kW charging a limitation? There are probably several cost effective work arounds to that issue. Adding external charging capacity is not a difficult process. My decision was based on balancing features. All of the above have good reputations.

 

[robsals]

Hedges - So will the SMA 7.7 GT inverter freq shift properly if paired with the SMA SI 6048s, or will there be problems due to the 6048s being UL-1741 but not UL-1741SA?

Looking to add some AC-GT and would like to know if these will play nice together. If not are there other/better options are am I limited by the SI 6048s not being SA?

Cheers,
Rob

 

[Ampster]

The issue is that the old panels are putting out about 8kW. The new unit needs to be able to absorb all of that and dump it into the batteries.

If those old panels are the ones that you want to AC couple I know that the limit for AC coupling varies by inverter. For example, even though the Sol Ark is called a 12kW inverter it has less AC coupling capacity than the Skybox. Even then it may depend on whether the GT inverter(s) are 1741 or 1741SA compliant in terms of the AC coupling capacity. Furthermore it is the AC capacity that matters, not the DC capacity of the panels. My only point is that one needs to dive deep into the technical specs when choosing the optimum solution. AC coupling is sensitive to loads so for the scenerio you describe it may be more cost effective to use an AC charger to get the charging Amps you want. A consistent AC load like a Charger might allow you to AC couple a larger GT inverter rather trying to rely on the hybrid inverter capacity alone for charging.

The batteries might only be at 50% charge, so the unit isn't going to start modulating the frequency because it wants to keep charging the batteries. Does that make sense?

Of course the assumption about modulating the GT inverter assumes it is 1741SA compliant. Otherwise it can only be on full blast or off. That is what I was referring to above in terms of AC coupling capacity.

 

[Hedges]

Hedges - So will the SMA 7.7 GT inverter freq shift properly if paired with the SMA SI 6048s, or will there be problems due to the 6048s being UL-1741 but not UL-1741SA?

Looking to add some AC-GT and would like to know if these will play nice together. If not are there other/better options are am I limited by the SI 6048s not being SA?

Cheers,
Rob

The Sunny Boy 7.7 kW GT PV inverters, so long as they have "frequency-watts" enabled, should work nicely with SI 6048.
Possibly some earlier revisions of firmware didn't support that and would need updating, I'm not sure.
For a time, these inverters were listed as not compatible for grid-backup, only for on-grid or off-grid. That has changed in the latest list.

SI-6048 being UL-1741 not UL-1741SA just means that SI-6048 doesn't respond to frequency shift from the grid. It could probably be programmed to tolerate the wider frequency and voltage range, but it wouldn't then disconnect after 300 seconds according to UL-1741SA. Probably just a firmware limitation, but no indication firmware would be changed to add that feature. I assume the new 8.0H model in Europe will come to the U.S. with UL-1741SA.

Being UL listed, I would expect SI-6048 can still be installed. It just can't be the GT PV inverter (as it would if you had DC coupled panels and configured it to export that power.) But if you're getting a permit, better confirm with local authority before purchase.

https://files.sma.de/downloads/SB-OffGrid-TI-US-en-22.pdf

This says, "Compatible if country data set CA Rule 21 is set"
I haven't worked with it, but I would look for "frequency-watts" in the settings, which I think is an option under Rule 21 in California.

 

[robsals]

The Sunny Boy 7.7 kW GT PV inverters, so long as they have "frequency-watts" enabled, should work nicely with SI 6048.
Possibly some earlier revisions of firmware didn't support that and would need updating, I'm not sure.
For a time, these inverters were listed as not compatible for grid-backup, only for on-grid or off-grid. That has changed in the latest list.

SI-6048 being UL-1741 not UL-1741SA just means that SI-6048 doesn't respond to frequency shift from the grid. It could probably be programmed to tolerate the wider frequency and voltage range, but it wouldn't then disconnect after 300 seconds according to UL-1741SA. Probably just a firmware limitation, but no indication firmware would be changed to add that feature. I assume the new 8.0H model in Europe will come to the U.S. with UL-1741SA.

Being UL listed, I would expect SI-6048 can still be installed. It just can't be the GT PV inverter (as it would if you had DC coupled panels and configured it to export that power.) But if you're getting a permit, better confirm with local authority before purchase.

https://files.sma.de/downloads/SB-OffGrid-TI-US-en-22.pdf

This says, "Compatible if country data set CA Rule 21 is set"
I haven't worked with it, but I would look for "frequency-watts" in the settings, which I think is an option under Rule 21 in California.

Thanks sir. I don't want to hijack the discussion but thought since y'all were on the topic I would ask. In my case, by 6048's are used in off-grid (backup) fashion and only connected via transfer switch in the main breaker panel when the power goes out and not connected to the grid. The grid-tie arrangement I'm considering would be setup to add power via ac coupling to the 6048s when there's enough sun. I appreciate your time and insights.

Cheers,
Rob

 

[Hedges]

The GT PV can be connected to 6048's, but then the 6048's have to be connected to main panel when grid is up in order to backfeed the grid.

Not sure if you mean you would put the GT PV on main panel so it supports loads or backfeeds grid most of the time. If grid fails, you use a (manual or automatic) transfer switch to have 6048 feed main panel instead of grid? AC to GT PV should be down for 5 seconds before transferring to 6048, to ensure it isn't active and unsynchronized when they connect.

Or, maybe you mean you will have an off-grid SI-6048 & SB 7.7 system. If grid fails, instead of using a generator your transfer switch feeds main panel form SI-6048. In this case, you may miss out on available solar power, not using it for loads on main panel when grid is up. Maybe a zero-export configuration would help; I haven't used that.

I have GT PV, and protected loads on output of 6048. It's input comes from main panel, so GT PV feeds the grid (net metering.)
During a power failure, if I want I can turn off breaker feeding 6048, and flip interlocked breakers so it feeds main panel and the loads there.

 

[robsals]

The GT PV can be connected to 6048's, but then the 6048's have to be connected to main panel when grid is up in order to backfeed the grid.

Not sure if you mean you would put the GT PV on main panel so it supports loads or backfeeds grid most of the time. If grid fails, you use a (manual or automatic) transfer switch to have 6048 feed main panel instead of grid? AC to GT PV should be down for 5 seconds before transferring to 6048, to ensure it isn't active and unsynchronized when they connect.

Or, maybe you mean you will have an off-grid SI-6048 & SB 7.7 system. If grid fails, instead of using a generator your transfer switch feeds main panel form SI-6048. In this case, you may miss out on available solar power, not using it for loads on main panel when grid is up. Maybe a zero-export configuration would help; I haven't used that.

I have GT PV, and protected loads on output of 6048. It's input comes from main panel, so GT PV feeds the grid (net metering.)
During a power failure, if I want I can turn off breaker feeding 6048, and flip interlocked breakers so it feeds main panel and the loads there.

The current configuration is a DC Solar trailer with dual 6048s and 2.4kw solar as an off-grid config. This trailer uses a diesel generator as backup to the solar. The off-grid package connects to a transfer switch inside the house/garage. It is never connected to the grid. The main panel is either connected to the grid OR the 6048s.

The thought was to implement a 2nd solar array using the SMA GT 7.7 in parallel with the 6048s to provide additional AC when solar was active and not need the generator as much (or at all). The entire arrangement would be operated off-grid fashion. If needed, the AC-coupled SMA GT 7.7 could be started up separately. In truth the 6048s run full time with no load and can be switched simply by throwing the transfer inside the main panel.

Hopefully that helps clear things up.

If it all works as expected, it might even be possible to run the GT package through a transfer switch and have it able to truly be grid-tied - OR - paralleled with the off-grid 6048s, but that might be a stretch.

Rob

 

[TexasSun]

Ampster, I thought I did answer it. Basically, I don't want to waste power when in critical need. If I'm not using power, and the enphase inverters can produce it, I want all of that energy going into batteries. If it can take 4kW, and the enphase is capable of 8kW, then I will have to disconnect half the enphase units (or be certain that at least 4kW of load is always active). BTW, the Sol-Ark is rated for 185 amp charging capacity. It is the highest of any of the options I've seen. But, right now, the Sigineer model is looking like the choice for my buddy's setup. Not quite everything he wants, but life is full of tradeoffs.

And, just for everyone's entertainment.... do you know why a cow is so tired after having her baby?

She's.... decalfinated. Thank you, thank you, thank you very much. I'll be here all week, and please tip your wait staff well!

 

[Hedges]

The current configuration is a DC Solar trailer with dual 6048s and 2.4kw solar as an off-grid config. This trailer uses a diesel generator as backup to the solar. The off-grid package connects to a transfer switch inside the house/garage. It is never connected to the grid. The main panel is either connected to the grid OR the 6048s.

The thought was to implement a 2nd solar array using the SMA GT 7.7 in parallel with the 6048s to provide additional AC when solar was active and not need the generator as much (or at all). The entire arrangement would be operated off-grid fashion. If needed, the AC-coupled SMA GT 7.7 could be started up separately. In truth the 6048s run full time with no load and can be switched simply by throwing the transfer inside the main panel.

Hopefully that helps clear things up.

If it all works as expected, it might even be possible to run the GT package through a transfer switch and have it able to truly be grid-tied - OR - paralleled with the off-grid 6048s, but that might be a stretch.

Rob

Are you saying GT SB 7.7 would never feed the grid, only feed SI-6048 and help charge batteries?
That would miss out on either backfeeding grid for net metering or offsetting consumption by grid-connected loads.
SMA does have a zero-export solution with added hardware, if you don't want or can't have net metering, so SB 7.7 would adjust output to not exceed loads.

Did your trailer come with the generator? I've heard from people who have trailers without the generator. A battery shunt was installed but maybe not configured in SI-6048. Midnight Classic provides charging according to battery voltage, and nothing else is needed if no AC (generator) or GT PV. If GT PV added, shunt has to be configured so SI-6048 knows battery current and can track SoC.

With generator already integrated in trailer, I would expect SI-6048 to be configured to see current from Classic, and SI-6048 uses current from generator input to also charge. In that case, GT PV as another source should work without further configuration of SI-6048.

You could also add a transfer switch to feed SI-6048 from either generator or grid. A signaling contact would indicate which source. Transfer switch should be "off" for 5 seconds before connecting other source (not just a DPDT relay.) If SI-6048 can be fed from main panel and also can feed its output into main panel, then you need to disconnect its input from main panel so it doesn't feed itself. I do that manually because both connections are breakers. Since you have a transfer switch feeding main panel, just tap off from grid side of transfer switch to feed SI-6048.

If you have SB 7.7 on grid, you can have the trailer supplying critical loads, never on grid. If grid fails then a transfer switch moves main panel from grid to trailer. That can have been manual interlocked breakers, but you've got a transfer switch. Once on trailer and SI-6048, the SB 7.7 would feed SI-6048.

 

[SolarPrep]

I’m thinking, in a grid down gas lines down… winter weather situation… 100Ah isn’t unreasonable… the amount of energy electric resistive heaters use is STAGGERING…
Then again, the odds his will happen again is low. Likely whatever took down the gas mains has been corrected. I’m certain MANY homeowners in the area purchased standby generators after the fact…

It would be great to economize first, and then design your system, right? Maybe we could address some of the systemic problems we have, like infrastructure that is falling apart. I fear that this forum is becoming just another place for people to flaunt their wealth, and link to videos with people putting in 3 Sol Ark 12k units, so they can charge their Tesla.

 

[SolarPrep]

It would be great to economize first, and then design your system, right? Maybe we could address some of the systemic problems we have, like infrastructure that is falling apart. I fear that this forum is becoming just another place for people to flaunt their wealth, and link to videos with people putting in 3 Sol Ark 12k units, so they can charge their Tesla.

The second part of my post got cut off. There is a lot of great advice on this forum, and people who are trying to make more, with less. Promoting DIY skills and projects. Learning to adopt new strategies for energy conservation. But then there is the "more is better" that just seems to have taken over our culture. We got hit with a derecho last year, 140 mph winds. Wiped out most of our town. People learned a very tough lesson about what it is like to go for weeks with no power, no internet for 1-2 months, etc. To see lines 2 miles long at gas stations who couldn't pump gas anyway, even if they had it.

Our infrastructure here is crumbling and it depends on cheap prices, cheap transportation, etc. Those days are rapidly going away, and a new mentality will have to be adopted.

 

[TexasSun]

I can't argue with anything you wrote SolarPrep. Infrastructure across the US is crumbling as well.

But none of this is addressing my questions. Does anyone have a better option than the Sigineer unit? $3200. 60 amps dc charging. Considering an external additional DC charger.

 

[Ampster]

Does anyone have a better option than the Sigineer unit? $3200. 60 amps dc charging. Considering an external additional DC charger.

I continue to favor the Skybox which has an 100 Amp charging current.

 

[SolarPrep]

I was interested in the Skybox until I recently learned it is a discontinued product.

 

[Ampster]

I was interested in the Skybox until I recently learned it is a discontinued product

I did not know that. Where did you read that? There is no mention of that on the Outback site or forum.

 

[TexasSun]

Well fudge. In reading specs in more detail, I realized that the Sigineer model does NOT work with the grid. So it will not produce power onto the grid which is a problem. (I'm surprised nobody mentioned that!). OK, back to the list:

$7k Sol-Ark 12k... full featured
$3k Outback Skybox... 5kW output, only 4kW charging capable
$5k Sunny Island used (2x units)... full featured but no warranty
$3.2k Sigineer M12040D . 12kW inverting, 120A solar charger plus 100A charger. (please verify, but I take that to mean it will charge off it's own panels at a 6kW rate, and additionally charge from the enphase inverters at a 5kW rate at the same time?)

Well that takes out the Sigineer. Next options are the Outback Skybox (yes Ampster) and the Sunny Island (not in love with 'used' units, but new units aren't that much more). OK, first, SolarPrep, can you point to evidence that it is being discontinued? And Ampster, how can I get the Skybox to have more charging capacity? Can it support an external charger that it will control to run in AC coupled mode... or is my only option to get 2 units? And for the Sunny Island system, I've heard where they need a transformer. Can someone point to where I can read more about that?

BTW, again, reading specs more indepth, I read where the Sol-Ark 12k only actually supports 9 kW of continuous output in inverter mode! Gotta read the fine print.
Thanks