How to guarantee no backfeeding to the grid?

[Rational]

or send all your loads through the inverter, that is put everything on the "critical loads" port of a hybrid inverter.

Oh.... just put ALL loads on the critical loads port of a hybrid inverter? Well, that's easy enough. Seems like a clean answer then. Thank you.

The "zero export" in a grid-tied inverter will normally not have a fast enough control loop to actually have zero export. Some small amount of export will remain.

Okay. I'd heard about the first part and even asked Solis support and they confirmed some small amount can go back to the grid.

How much depends on the control loop parameters of the inverter and the salding/netting interval of your utility meter.

But the control loop parameters and "salding/netting interval" are new terms for me.

Okay, I'll study about those. Somehow I doubt my Okinawa power electric company shares that info publicly though to help determine.

 

[Rational]

got a info link on this?

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I just realized though that you may have taken your Tesla pack apart to make it 48v?

His battery emulator makes it so that you don't have to take it apart.

You can use car EV packs fully assembled. Less work! Safer. Faster. But they're HV, so need an HV inverter:

R

Thread 'Inverters that support high voltage (500v) storage batteries'

Jun 17, 2024

Hi guys,

Second post. I'm in Japan (100v 60hz) and am researching the best inverter brand and model to buy for a DIY solar build.

I intend to connect a Leaf 24kWh battery to it for home storage. I'm a member of Dala's EV discord group but have additional questions.

So far I've been able to determine that I need a single phase inverter (Edit: split phase) as that is what's used here in Japan. But very few brands support higher than 48v storage batteries as far as I can tell. Especially in single phase inverters.

Not sure if I will do grid tie right away but may want to later for net...

• Rational
• Replies: 221
• Forum: DIY Solar General Discussion

 

[stromy]

But the control loop parameters and "salding/netting interval" are new terms for me.

Okay, I'll study about those. Somehow I doubt my Okinawa power electric company shares that info publicly though to help determine.

Both the utility companies, and the inverter vendors, are pretty tight mouthed about these parameters.
For some inverters a german government financed study analysed the control loops:
See https://solar.htw-berlin.de/wp-content/uploads/HTW-Energy-Storage-Inspection-2024.pdf starting page 49.

 

[rogerheflin]

EG4 18kpv/12kpv have an off-grid mode. In that off-grid mode the system either runs all from the grid (can charge batteries from solar or grid, but no "boosting" from solar/batteries--inverter seems to stay off) OR it runs all from solar + batteries via the inverter. When it switches from use-grid to use-inverter I can hear the relays clicking so there appears to be a automatic transfer switch built in, and the power has a fast blip when this happens so from what I can tell in this mode there should be no back-feeding at all as it disconnects grid to use inverter and disconnects inverter when it uses grid. The model you are using MAY have a similar option.

 

[Solar Guppy]

Welcome to your journey.

Chargeverters are 48V, the Solis S6 is an HV battery inverter, so that isn't an option.
There is an "off grid mode" but it requires no grid be connected, so its kind of pointless

The S6 will only export if:

• Connected to a grid source the grid profile match and meets all parameters and timeout values
• Has a power source to export from, this could be a battery or solar
• Is configured to export

There is no danger to connect to your grid as its split-phase, you will need to modify the grid profile to meet your local grid, can be done in the Solis mobile App using Bluetooth

The S6 comes with external meter and CT's, place these on the lines that feed the main panel the inverter grid port is connected too.

At this point you just have a powered brick, backup port can only be enabled when it has battery that has active communications with a supported battery by Solis ( hint Seplos Hiten, there is no DYI option and I've communicated to the OP this is the fact many times ), putting loads on the backup port will have no power otherwise.

If solar is connected, it can do grid sell, it can be configure to zero export using the CT's meaning as long as the external meter/ct's see energy flow coming from the grid to your main panel it will export for loads down stream of the incoming connection, but there can be transients measured in seconds of export when home loads turn off.

 

[Zwy]

Also, reposting this question from another thread I'd asked this question in but didn't want to hijack the other member's thread so am posting here for input. Thank you guys.

"Hey @Zwy . Interesting post you have here. First I've heard of this 'sync phasing' topic. Is this what is set when you choose your grid-tie region code in the settings of an inverter to make sure it 'matches' correctly?

I ask, because I was perhaps mistakenly thinking I could connect any grid-tie hybrid inverter to the grid and just set it for zero export and it would still power up fine. I guess not? It has to have the correct grid code applied in the settings first or it can let the smoke out?

I went back and looked at the thread the post quoted came from.

In that thread, the member wanted to use an off grid inverter with a suicide cord plugged into a wall outlet with grid power live at the outlet. Basically attempting to backfeed power from an off grid inverter to grid power thru an outlet. The issue is phasing of the sine wave, one can not just plug in a power source that is not in parallel phase or can't adjust to be in parallel phase. Some off grid inverters will run in parallel to grid while others won't.

 

[Solar Guppy]

The S6 will work with any split phase grid, all that is done for local grids is adjusting in the voltage setting to meet what your local grid provider has for equivalent but lower voltage values and or frequency for Japan compared for example the USA. These inverters work all over the world, it's just different software profiles for each county or region.

You will need follow the instructions to install the Solis App on a mobile device an connect with the S6 which gives you full access to configuration of the inverter.

From the main app window "settings" -> Grid Code Settings -> Grid Code Parameters you can adjust the current profile or select on of about 50 others or make your own custom one by clicking on Grid Code and select User-define. As for values, one could start with using the US-240V-18 and adjust all voltage parameters proportional, for example if your split phase is 210 to the US 240, that would be a scale of ~87%.

Keep in mind, you are connecting an inverter that is not certified for Japan and you are the "engineer" when adjusting for your local region / power grid. Solis inverters are not country specific but phase types must match. For example many county's are single phase, the UK which is not compatible with split phase which from a quick search is what part of Japan residential is and your inverter is as well.

 

[dougbert]

ah, now I understand the Solis inverter, so no, chargeverter will not work in that application. thanks @Solar Guppy

 

[SeaGal]

Chargeverters are 48V, the Solis S6 is an HV battery inverter, so that isn't an option.

Just to clarify, for European viewers reading this... the "Solis S6 HV is an HV battery inverter". But there are also regular 48V Solis S6 hybrid inverters in Europe that work with 48V batteries.

 

[aonangj]

We lost power for 10 days due to Hurricane Helene, and I went down the rabbit hole of solar and batteries. I was planning on setting up a small battery backup to a transfer switch but then realized I might as well build a system that could power most of my home usage and be a battery backup in emergencies. SO I found this thread as I'm researching how to build a basic system that would be "off-grid" and yet still have my grid connected. My idea was to buy an off the shelf system, was looking at this 20KW system from sungoldsolar system would include 32 440W panels, 6 48v 5kw batteries and 2 10KW Inverters in parallel (20KW) (I realize that's not really DIY, but I'd rather just buy stuff off the shelf and set it up myself) and thinking to hook the system up to either a R510A Pro/Tran2 Outdoor 50-Amp 10-Circuit 2 Manual Transfer Switch or R310A Pro/Tran2 Outdoor 30-Amp 10-Circuit 2 Manual Transfer Switch and wire the inverter directly to the transfer switch.

For my usage I could hookup all my most important stuff in the house to 10 total circuits, is it a crazy idea to just wire the inverter up directly to the manual transfer switch? I see the subpanel idea, but that seems a bit overkill for my scenario. Would love any insights.

 

[ChrisG]

We lost power for 10 days due to Hurricane Helene, and I went down the rabbit hole of solar and batteries. I was planning on setting up a small battery backup to a transfer switch but then realized I might as well build a system that could power most of my home usage and be a battery backup in emergencies. SO I found this thread as I'm researching how to build a basic system that would be "off-grid" and yet still have my grid connected. My idea was to buy an off the shelf system, was looking at this 20KW system from sungoldsolar system would include 32 440W panels, 6 48v 5kw batteries and 2 10KW Inverters in parallel (20KW) (I realize that's not really DIY, but I'd rather just buy stuff off the shelf and set it up myself) and thinking to hook the system up to either a R510A Pro/Tran2 Outdoor 50-Amp 10-Circuit 2 Manual Transfer Switch or R310A Pro/Tran2 Outdoor 30-Amp 10-Circuit 2 Manual Transfer Switch and wire the inverter directly to the transfer switch.

For my usage I could hookup all my most important stuff in the house to 10 total circuits, is it a crazy idea to just wire the inverter up directly to the manual transfer switch? I see the subpanel idea, but that seems a bit overkill for my scenario. Would love any insights.

Still without power at my cabin from Helene, day 32. I have a EG4 6000xp system running critical loads and at first went down the R510 MTS path, then decided just to move all the circuits I want to power to a critical loads sub panel which is also fed via grid but using an interlock kit to separate grid from inverter power.

We evacuated cabin for home before Helene hit area and in the 'scramble' to get out, I forgot to turn one circuit off that was running our dehumidifiers (basement and inside cabin). After grid went out, the 6000xp/batteries keep up as long as they could but didn't last long and my ground array was destroyed from the storm, found a few panels down the mountain. I guess my point to this ramble is you really need to think about what are considered critical loads. I love the 510A Pro-Tran but I did have some issues with GFCI/AFCI circuits with it. Overall I'm re-thinking everything at my cabin and primary home after Helene.

 

[Zwy]

We lost power for 10 days due to Hurricane Helene, and I went down the rabbit hole of solar and batteries. I was planning on setting up a small battery backup to a transfer switch but then realized I might as well build a system that could power most of my home usage and be a battery backup in emergencies. SO I found this thread as I'm researching how to build a basic system that would be "off-grid" and yet still have my grid connected. My idea was to buy an off the shelf system, was looking at this 20KW system from sungoldsolar system would include 32 440W panels, 6 48v 5kw batteries and 2 10KW Inverters in parallel (20KW) (I realize that's not really DIY, but I'd rather just buy stuff off the shelf and set it up myself) and thinking to hook the system up to either a R510A Pro/Tran2 Outdoor 50-Amp 10-Circuit 2 Manual Transfer Switch or R310A Pro/Tran2 Outdoor 30-Amp 10-Circuit 2 Manual Transfer Switch and wire the inverter directly to the transfer switch.

For my usage I could hookup all my most important stuff in the house to 10 total circuits, is it a crazy idea to just wire the inverter up directly to the manual transfer switch? I see the subpanel idea, but that seems a bit overkill for my scenario. Would love any insights.

You should contact Current Connected. They will help you and provide some excellent support should you need it. For the price of the Sungold kit, you could have this full off grid setup. Cost as shown is $17.5K.

Something smaller, for $12.3K.

All kits listed here.

No need for the transfer switch if you went with the whole house kits. Just install a generator interlock on the main panel and switch to running your house entirely off solar.

 

[Glock24]

I'm a bit late to the answers but here I go.

In my country grid tie with grid export is a real PITA and if you manage to do it you won't get much benefit.

The Solis inverters are common here, they come with their own box to limit export but it doesn't work very well as it's very slow to respond and you inject for a time and then the solar energy production is cut for a long time.

I've managed to find a device that work very good and is very responsive. We installed 2 for a friend and I know of at least four of these devices working for over 4 years and they've been good so far.

ZERO EXPORT controller – elgris

 

[aonangj]

Still without power at my cabin from Helene, day 32. I have a EG4 6000xp system running critical loads and at first went down the R510 MTS path, then decided just to move all the circuits I want to power to a critical loads sub panel which is also fed via grid but using an interlock kit to separate grid from inverter power.

We evacuated cabin for home before Helene hit area and in the 'scramble' to get out, I forgot to turn one circuit off that was running our dehumidifiers (basement and inside cabin). After grid went out, the 6000xp/batteries keep up as long as they could but didn't last long and my ground array was destroyed from the storm, found a few panels down the mountain. I guess my point to this ramble is you really need to think about what are considered critical loads. I love the 510A Pro-Tran but I did have some issues with GFCI/AFCI circuits with it. Overall I'm re-thinking everything at my cabin and primary home after Helene.
View attachment 252614

Oh man, sorry to hear you were hit so hard. I didn't even really think about the fact that a ground mount could be destroyed by that level of wind. So what you are saying is that the 510A Pro-Tran did work though, so that's good that my concept isn't off.

 

[aonangj]

You should contact Current Connected. They will help you and provide some excellent support should you need it. For the price of the Sungold kit, you could have this full off grid setup. Cost as shown is $17.5K.

Something smaller, for $12.3K.

All kits listed here.

No need for the transfer switch if you went with the whole house kits. Just install a generator interlock on the main panel and switch to running your house entirely off solar.

Thanks @Zwy. I've taken a look and it looks like they have similar setups, but with more of the small components likely needed to complete the installation for around the same cost just made up of different brand components overall. Does that sound accurate? I appreciate the ability to get helpful support as well as I move down this journey.

The reason I was looking at a transfer switch for the majority, versus a full interlock is I didn't think Solar would quite run all of it during peak times. Looking at my utilization my average in low seasons (Fall/Spring) is around 20KWh/day, but peak in Summer is 50-60kWh/day. My idea was if my system was producing around 30kw/day most of the time I could run everything, but then when peak hits I could switch the HVAC back to the grid so as not to go down, but then keep all of the other primary circuits on the solar inverter. My understanding is that with a full interlock I'd either have to have all on one or the other. If I'm missing something though, let me know.

 

[OffGridInTheCity]

Per the original post - I fundamentally use ATSs to connect my 100% off-grid solar system to my home circuits with automatic grid assist. When solar power is available / inverter is producing AC the ATS will detect the available power and automatically switch so that the inverter is powering circuits. When the battery runs down / inverter turns off, the ATS detects this and automatically switches back to grid.

Here's a pic illustrating one of my ATSs at the main panel. In this case, I've also added an MTS to control individual circuits as being on the ATS or 100% grid.

The ATS and MTS shown here are both ETL listed. Here's the Progressive ATSs I use for 240v/120v split-phase - https://www.amazon.com/gp/product/B003VAWNVK/ref=ppx_yo_dt_b_search_asin_title The MTS is a standard 10circuit Pro/Tran2 that can find at Home Depot. A mechanical ATS is a pair of relays physically connected so that only 1 can close the circuit at a time - not physically possible for the Grid and Inverter circuits to cross-connect - e.g. no possibility of grid feedback.

Reasonably priced ATSs with ETL listing are limited to 240v @ 50a OR 120v @ 30a (Go-Power for example) but one install more than 1 to cover more circuits. In fact I have 4 around the house that cover ~80% of my home circuits. Generac makes a 100a ATS but it's very expensive and not sure it's ment for 1000(s) of switch-overs.

As far as Chargeverters - I have these as well but power them via generators. I have 2 of them - 1 for my 240v generator and 1 for my 120v generators. I could power them from the Grid and there would be no back feed (as they only connect to the battery) but I don't have any 240v wiring near to plug them into.

 

[Warpspeed]

Hi guys,

Is there a way to connect my new inverter to the grid but guarantee the power company will not see any back feeding so they won't know it exists?

Yes there is.

The way NOT to do it is to first buy a grid tie inverter, then try to figure out a way to prevent it from working.
That makes no sense at all.
Go completely off grid with an appropriate off grid inverter.
Then connect up a grid connected voltage regulated dc power supply to charge up the battery, but ONLY when the battery voltage becomes dangerously low, and then only by just enough to hold the battery at minimum acceptable voltage.

If you have sufficient solar, it should only draw minimal grid power, for very short periods during the worst of mid winter.
This works seamlessly, and back feeding is just not possible under any circumstances.

 

[Warpspeed]

Its not difficult.
Suppose you have a typical 48v system, and you decide that a minimum safe battery voltage is 40v.

An e-bay 500 watt switching power supply set at 41 volts output can be connected to the battery through a suitable diode.

The no load idling power of something like that will only be a few watts of constant grid power which can be ignored.
But even a little supply like that can still source 12 Kwh over 24 hours, and that might be enough for you ?
If not buy two !

Now 500 watts is still not a lot, but remember the battery is still there to supply peak surge loads, like starting up your refrigerator or running a microwave. The important thing is just to have enough dc grid power for your AVERAGED daily consumption.
The battery should still be able to supply peak demand even if its way down in voltage.

Even with zero sun for several days in a row, with care, a system like that can get you through the bad times.

If the few continuous grid watts of idling power irritates you, a battery voltage sensor could disconnect the dc supply from the grid until the the battery voltage starts to drop, say below 43 volts in this example.
That adds complexity, and the gains are just not worth the trouble IMHO.

I just leave my dc supply permanently switched off, except during sustained cloudy weather, and I can see the battery slowly dying.

 

[aonangj]

Here's a pic illustrating one of my ATSs at the main panel. In this case, I've also added an MTS to control individual circuits as being on the ATS or 100% grid.

Hey @OffGridInTheCity - This is super helpful. I appreciate you bearing with me trying to understand. What is the value of the ATS ahead of the MTS. Since the MTS is a manual transfer that requires physical intervention, wouldn't that render the ATS useless? In that case are you essentially using that MTS as a mini-subpanel since you are never changing the switch positioning so that you can use the ATS to power multiple circuits?

Also, if you used an ATS to a subpanel would the ATS be safe enough to keep any power backfeeding to the grid or is the MTS necessary?

This is super helpful as this is how I'm imagining my setup would work.

 

[Zwy]

Thanks @Zwy. I've taken a look and it looks like they have similar setups, but with more of the small components likely needed to complete the installation for around the same cost just made up of different brand components overall. Does that sound accurate? I appreciate the ability to get helpful support as well as I move down this journey.

The support from Current Connected will definitely help if you are new to solar. As for comparing the Victron system to the SG, there is no comparison. The pair of 10K Quattros would handle a surge of 20Kw. I almost went with Quattros for my shop but instead decided to use SRNE 10Kw units in parallel. The SRNE will give the 20Kw surge but only for about 1 or 2 seconds while the Victron Quattros will surge for a minute or more. But I am designing and building a system based upon past experience. Inexperienced and looking at various kits in that price range, I'd go with the Victron kit from Current Connected.

The reason I was looking at a transfer switch for the majority, versus a full interlock is I didn't think Solar would quite run all of it during peak times. Looking at my utilization my average in low seasons (Fall/Spring) is around 20KWh/day, but peak in Summer is 50-60kWh/day.

Very similar to my usage but you do need to know what the peak surge will be. I run a pair of LV6548's and those handle my well pump but I also have a 58 Kwh battery bank to draw from. Most systems will be short on battery to handle a high surge. The LV6548 is a HF inverter and thus can only power a surge for those few seconds before overload where something like the Victron Quattro could handle the surge longer.

We cool with inverter mini split heat pumps downstairs and a window unit upstairs but I think the window unit might be gone in a year or so. Inverter type heat pumps work very well with off grid solar, no need for HVAC soft starts or using an inverter that can surge for longer time frames.

So what I referring to is the need to know the highest surge loads you need to start. If HVAC is older, non inverter type, it will have a high surge. The well pump is also a huge surge load. If you already have an inverter well pump, then you won't have to worry about that surge. My well pump draws 54A for the first 3ms on each leg and I was concerned the system would not be able to start it. However, with the larger battery bank I have not had an issue. If the current well pump fails, I will then install an inverter well pump.

My idea was if my system was producing around 30kw/day most of the time I could run everything, but then when peak hits I could switch the HVAC back to the grid so as not to go down, but then keep all of the other primary circuits on the solar inverter.

I think with the Quattro's and enough battery it won't be an issue. On average, this time of year we use around 30 Kwh per day and that is heating the house with heat pumps.

My understanding is that with a full interlock I'd either have to have all on one or the other. If I'm missing something though, let me know.

It can be done several ways. The interlock on a loads panel will let you choose between power from a backfed breaker or from the grid but not at the same time. I'm installing one in my shop loads panel. I am installing another breaker panel on the outside of the wall where grid power will come in. This breaker panel has lugs at the bottom and those will be wired to the current 200A breaker in the breaker panel. I will have a 100A breaker in the breaker panel and that will feed power to the inverters if it is switched on to provide pass thru power or charge batteries from grid (which I won't be doing but might want pass thru power). All loads will be powered by the loads panel.

My house is wired somewhat similar but has a manual transfer switch instead of an interlock. I posted this photo sometime ago in this post.



On the right side, you will see the breaker panel with grid power. There are 3 breakers because this was right before I moved the well circuit to the loads panel on the left. One breaker is grid power to the transfer switch, the other breaker is to the inverters. All loads are powered by the left panel which is fed by the transfer switch. I have since added another loads panel below the upper loads panel, I needed some more breakers as I added mini splits and a heat pump water heater.

The concept is the same, all loads are powered thru the loads panel. Power is routed thru either a breaker or double throw transfer switch to feed the loads panel. The interlock would be installed on the loads panel with a backfed breaker coming from the inverters.

I normally keep the breaker to the inverters for grid power off. The reason is the inverters will draw some power from grid when grid power is present on the inverter AC input terminals. The only time I switch on the breaker would be if the battery bank SOC is getting extremely low in winter and I need the inverters to automatically switch to pass thru power. If I need to bypass the solar system entirely in order for repairs or maintenance, I flip the manual transfer switch.

I did consider using an ATS for the shop system but instead decided to just install a breaker panel outside the wall and an interlock on the loads panel. It is simple, easy and cheap.

Before you consider purchasing a system, you need to ensure you have your Kwh usage correct and what load surges there will be.

 

[OffGridInTheCity]

Hey @OffGridInTheCity - This is super helpful. I appreciate you bearing with me trying to understand. What is the value of the ATS ahead of the MTS.

The ATS feeds power to the MTS via the "Generator Input" of the MTS. Normally you'd just feed in generator power but by replacing the generator with an ATS you can feed grid (circuit from the main panel) or the inverter and the ATS will choose automatically. The MTS doesn't care.

I know it sounds complicated or circular but it's not. It's 3 steps....
1) You wire 240v/120v from the main panel -> grid relay of the ATS.
2) You wire 240v/120v from the solar inverter -> gen relay of the ATS.
3) You wire the output of the ATS -> MTS generator input.
All standard 6awg (50a) wiring, all ETL (or UL) parts.

If you only need 120v @ 30a, you can use a Go-Power ATS (also ETL) and it's even simpler and is only 120v. They make 120v only MTSs as well.

Since the MTS is a manual transfer that requires physical intervention, wouldn't that render the ATS useless? In that case are you essentially using that MTS as a mini-subpanel since you are never changing the switch positioning so that you can use the ATS to power multiple circuits?

Yes, the MTS serves the same function as a 'critical loads subpanel' except you can choose individual circuits instead of all or nothing. But this is different than routing power to the overall subpanel (or MTS). In a critical loads subpanel situation you have grid coming in AND generator/inverter coming in and you switch manually via a breaker interlock. The ATS replaces the 'manual interlocked breakers' and is automatic.

The MTS give you 3 choices for each circuit via a toggle switch for Line (grid), Gen (ATS in this case) or Off (nothing).

With the MTS I can switch each individual circuit between grid all the time or the ATS (grid or inverter). One circuit can be grid, the next ATS and so on. This let's me choose 1 thru 10 circuits and I can vary the total load on the inverter. They make MTSs for 120v only or 240v/120v with 4 thru 10 circuits - you don't have to do 10 circuits.

Also, if you used an ATS to a subpanel would the ATS be safe enough to keep any power backfeeding to the grid or is the MTS necessary?

The MTS wiring keeps all this separate - it's not possible to backfeed anything and it's not to bad to wire into you're main panel. The wires are all numbered and colored and there are several good youtubes on hooking up a Pro/Tran2 (or Reliance) MTS - these might help you understand better. Search "Protran2 Installation".

This is super helpful as this is how I'm imagining my setup would work.

It works really well for me but... there are 2 downsides......
1) The switch from grid to inverter (and back in particular) is not quite fast enough for computers and sensitive circuits. So I use an APC UPS on my computers and Tivo/TVs to take care of this. Refrigerator, cooktop, dryer, washer, microwave, etc etc are OK/remebber their settings even with a quick loss of power during switch-overs. And no, modern refrigerator motors etc don't have a problem with mis-matched sine-waves during switch over.

2) I have 4 x Progressive ATSs and have had to replace the relays on 2 of them after 5 yrs. After ~3,000 switch-overs (twice a day for 5 yrs) I've had the mechanical relays 'stick' in position on grid every now and then and it got progressively worse. I've adjusted my PV -> Load now so that I only do 100 switch-overs / year instead of 700 so it will take a really long time to get to 3,000 switch-overs. But it wasn't hard to buy a new unit and switch the internal relays within the existing metal box - just unscrew some wire and re-screw on new relays. This avoids the whole metal box / conduit removal / replace.

--------------------
Final comment - when I did my system 7 yrs ago we didn't have such a nice selection of off-grid AIOs such as MPP Solar off-grid. These days there are off-grid specific AIOs have the ATS and UPS built-in + PV inputs + battery all in one box. MPP Solar LVX6048, EG4 6000XP, Growatt, and others. Not pushing any brand, just want you to realize that you don't have to do individual components to get the exact same functionality we're discussion.

For example, if you did an off-grid MPP Solar 6000w unit, you wire grid to it (just like the ATS above), + battery + PV and wire the output to an MTS (just above) or a critical loads sub-panel and the single unit does the ATS + UPS + PV + Battery + Inverter - no chance for grid back feed!. You can parallel these for 240v/120v split-phase and A LOT of power - usually up to 24,000w range (e.g. 240v @ 100a)

 

[aonangj]

Before you consider purchasing a system, you need to ensure you have your Kwh usage correct and what load surges there will be.

This was all super helpful, thank you @Zwy. I can easily find the Kwh usage on my energy bill, but how do people generally determine their surge load prior to designing the system? Is there a reasonably priced device that can tell me that?

I bought two EcoFlow Delta Max battery backups during the storm because a small gas generator wouldn't start up my well pump but with the Delta Max it shows the surge in W and it was hitting 1875W at startup for 2-3s and then dropping to 1325W while running, but the generator wouldn't handle the initial surge, but how do I determine that on my whole system?

Between your and @OffGridInTheCity helpful advice, I'm looking at the Kits with EG4 18kPV paired with 2 G4 PowerPro 48V/280Ah LiFePO4 Battery - UL9540, Heated for 28.6kW Battery backup, but I still need to know the surge as you mentioned.

The reason the EG4's are more appealing to me than the Victron kit is due to our space and layout. We have a detached garage which is a couple hundred feet away and no great indoor space to put it (all technically living area), so I like the idea of the outdoor weatherproof inverter and batteries (pictures below). What are your thoughts on these EG4's? Ironically when I go to their site, they are announcing a new product soon the FlexBOSS21, which seems really appealing as it could maybe give me a slightly larger input as I'm planning on 20 x 405W Bifacial panels on a groundmount about 150' run from the battery and inverters. So maybe I wait and see if that launches before end of year.

Would love your feedback on my proposed layout and system, but I understand that knowing the surge load seems like a key item.

 

[aonangj]

MPP Solar LVX6048, EG4 6000XP, Growatt, and others. Not pushing any brand, just want you to realize that you don't have to do individual components to get the
exact same functionality we're discussion.

Awesome. Thanks. All of this was SUPER helpful!

Please see my above reply with my layout and the EG4's, I'd love your thoughts on this. Are you saying with the Eg4 you may not need a separate UPS for sensitive devices? Not a big deal just curious. We only have laptops, but I might want to get a UPS on the TV in the event of a switch if needed (but that's a long ways away at this point :D)

With the MTS I can switch each individual circuit between grid all the time or the ATS (grid or inverter).

Thanks, I see that it gives you more fine grained control, that's helpful.

If you only need 120v @ 30a, you can use a Go-Power ATS (also ETL)

I will need 240v for my HVAC so I think the one you shared is what I would need.

 

[OffGridInTheCity]

Awesome. Thanks. All of this was SUPER helpful!

Please see my above reply with my layout and the EG4's, I'd love your thoughts on this. Are you saying with the Eg4 you may not need a separate UPS for sensitive devices? Not a big deal just curious. We only have laptops, but I might want to get a UPS on the TV in the event of a switch if needed (but that's a long ways away at this point :D)

Yes - the ATS + UPS is built in to the proper AIO. I use an MPP Solar 3048LV in my camp trailer so I know this to be true - takes in AC, Battery, PV and outputs AC but there's no connection (grid-tie) between the output AC and incoming 'grid-assist' AC - e.g. cannot feed back to grid.

I don't have experience with EG4 but pretty sure they have an off-grid model that works the same way as MPP Solar off-grid models. The forum can clarify this. However, for 240v, you'll typically need 2 x Units (each do 120v) that work together for 240v - so leave room for this.

Thanks, I see that it gives you more fine grained control, that's helpful.


I will need 240v for my HVAC so I think the one you shared is what I would need.

The ProTran2, 10circuit model has a 30a breaker-pair (240v), a 20a breaker-pair (240v) and 6 x 120v breakers. You can separate the breaker-pairs into individual circuits by physically removing the tab on the breakers.

My HVAC is a 4-ton whole house heat-pump and the outside/compressor says 240v @ 18a max so the 30a breaker is fine. If you have a traditional (old) 3 - 5 ton AC compressor it's likely >30a, so you'll need to check for that - e.g. look for a label attached to the unit showing basic info if you can't find it otherwise.

Don't want to get too deep in the woods but you mentioned HVAC.......
These ProTran/Reliance - common MTSs - top out at 30a @ 240v breaker pairs. If you have equipment that's 40a or 50a @ 240v then they just don't make 'common' (affordable) MTSs at that level. In my case, this is where I wired in a dedicated 50a @ 240v ATS just for that load.

 

[Banjoman]

I put all my house circuits in a sub panel. Subpanel is fed from a transfer switch. Either solar OR grid feeds that subpanel, never both. Grid connection to inverter could allow momentary backfeed, so I don't have grid connected to inverter. If needed, I can flip a grid side breaker and feed power into my batteries using a chargeverter (no backfeed possible).

Exactly how I have my system wired in.