EG4 new AIO rated 12K output and 18kPV aka "EG4-18Kpv-12LV"

Quattrohead said:

Would I trust it to do this more than half a dozen times, absolutely not.

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That was my first reaction as well. However, when I look closer at the data sheet, things seem more reasonable.

The spec sheet says




The 50A rating is at 830Vac. It is not specified, but at 240V it will be able to break higher currents and still meet the 30,000 electrical operations that are in the specification. However, since the sheet does not specify a 240V break current, we can't quantify an increase and we can only evaluate operation cycles at the 830V.

What is interesting is the Electrical Life chart. It gives operation count information for switching much higher currents.


At 50A the chart indicates almost 50,000 operations, but they only rate it for 30,000 operations for resistive loads. They gave themselves plenty of margin for variations from what they tested.

At 200A the unit has ~ 20000 operational cycles. However, the chance of it ever switching at 200A is pretty low. In most households, even the peak is closer to 100A or 30000+ operational cycles.


Even if we dived by 4 to cover inductive loads, it is 5k-7.5K operations. Since the switching event will normally only occur during a power outage, this seems reasonable.

fromport said:

I just made quote for a person with 600 amps main and a 200 amp essential load panel.
I wouldn't want to make a bet that with their new EV they might be able to pull 400 amps

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I’m in the same position right now, putting together a proposal for a business that requires 400 amp service at its main structure (lots and lots of walk-in freezers and refrigeration, heavy AC loads, etc). I don’t want to spec only two units instead of three, and then get a call on a hot July day telling me that the system tripped.

So, we’ve got one distributor (Fortress) telling us that two units might pass through only 300 amps; another distributor (Signature) saying they “believe” it might be 400. A definite answer from someone who has actually load-tested this issue would be nice.

FilterGuy said:

Since the switching event will normally only occur during a power outage

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No. Unless I’m missing something, switching will occur every single time the load calls for more than the inverter’s rated output of 12KV, which triggers the need for AC pass through.

FilterGuy said:

That was my first reaction as well. However, when I look closer at the data sheet, things seem more reasonable.

The spec sheet says
View attachment 149454

View attachment 149455

The 50A rating is at 830Vac. It is not specified, but at 240V it will be able to break higher currents and still meet the 30,000 electrical operations that are in the specification. However, since the sheet does not specify a 240V break current, we can't quantify an increase and we can only evaluate operation cycles at the 830V.

What is interesting is the Electrical Life chart. It gives operation count information for switching much higher currents.
View attachment 149442

At 50A the chart indicates almost 50,000 operations, but they only rate it for 30,000 operations for resistive loads. They gave themselves plenty of margin for variations from what they tested.

At 200A the unit has ~ 20000 operational cycles. However, the chance of it ever switching at 200A is pretty low. In most households, even the peak is closer to 100A or 30000+ operational cycles.

View attachment 149457
Even if we dived by 4 to cover inductive loads, it is 5k-7.5K operations. Since the switching event will normally only occur during a power outage, this seems reasonable.

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I would still feel much more comfortable with the German made Gruner Relay.
50A Make and Break without a 240V rating is kind of a bit of guess work as to how it will perform when 100A or more is being connected or disconnected. One can only hope that they tested it through a lot of cycles to make sure the Relay contacts remain intact.

GuyG said:

No. Unless I’m missing something, switching will occur every single time the load calls for more than the inverter’s rated output of 12KV, which triggers the need for AC pass through.

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The inverter can back-feed and it has current transformers on the input. In normal operation, the grid will remain connected and the inverter will operate however it has been programmed to behave.

• If it is programmed for zero back feed, it will ramp down output as the demand goes down....keeping backfeed at zero.
• If the output load is greater than the inverter can provide, current from the grid will start flowing into the system and the loads will be serviced by power from both the grid and the inverter.
• If the inverter is configured to allow back-feed and the load is less than the inverter can supply, the extra output will back-feed onto the grid.
• If the grid goes down, the relays must be opened in order to for the inverter to safely continue to supply power to the house.

Thanks @FilterGuy but I’m afraid I’ve wandered off the path. What I’m really wanting is a definitive answer to the question I asked way back: If the end user sometimes has peak loads of, say, 350 amps, will two of these inverters with AC pass through handle those loads without tripping.

GuyG said:

Question for @SignatureSolarJames or anyone else who knows: What is the AC pass through for these inverters in parallel? The spec sheet on Signature’s site doesn’t even mention parallel (although the manual does). Will two units provide 400 amps? Three units 600? I ask because the Fortress Power guy made a comment somewhere that we shouldn’t count on more than about a hundred amps of pass through added per unit paralleled.

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This was my original question, posed last Wednesday.

SignatureSolarJames said:

We can review this, but I believe thaat 400A is possible with 2 units

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A few days later, James posted this. But the answer is not very reassuring or definitive.

@DER Solar You're definitely thinking these relays need to do more than they actually need to. There's no operating situation where these relays need to make or break 200A.

When the grid goes down, current through the relays will go to near 0 as the on board inverter takes over, and these relays will open. Lets speculate you're actually passing through 200A at the time the grid goes down. Well then it also doesn't matter if the relay sticks because this inverter can't output 200A so everything is going to go down anyway.

Sure you can compare this unit to the tesla unit, but you shouldn't, because they have different use cases and different markets.

And yes, I realize that this is a question that involves power levels that don’t apply to 99% of residential users. Right now. But when people start having level 2 EV chargers for all their cars, or start using tankless electric water heaters, peak loads will be way higher than they are now.

BraydenFromEG4 said:

1. AC Coupling works just fine in off-grid mode. It'll utilize the GEN port and the hybrid inverter will work as the power source instead of having the grid-interactive inverter look at the GRID port.

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What PV inverters have been tested? At full AC coupling capacity? Without DC coupled panels?

Can someone at SignatureSolar tell us what the lugs are rated for? Are they rated for 200A?
No way that 400A pass-through is possible without 400A lugs and a 400A external transfer relay or external contactor!
Parallel relays will arc and get stuck, because all it takes is one relay to be faster than the others and this relay gets all the current!

The safe method for switching 400A is a 400A rated transfer switch, but they are expensive and very slow and they need to be driven from an auxiliary control output for an external contactor!

Schneider has excellent documentation how to stack XW Pro inverters and use either an external contactor or an external MID switch aka BCS 2200.
I would not even stack more than 2 inverters without an external contactor!

Franklin WH requires separate 200A backup systems each for 400A, 600A and more.

DER Solar said:

Can someone at SignatureSolar tell us what the lugs are rated for? Are they rated for 200A?
No way that 400A pass-through is possible without 400A lugs and a 400A external transfer relay or external contactor!
Parallel relays will arc and get stuck, because all it takes is one relay to be faster than the others and this relay gets all the current!

The safe method for switching 400A is a 400A rated transfer switch, but they are expensive and very slow and they need to be driven from an auxiliary control output for an external contactor!

Schneider has excellent documentation how to stack XW Pro inverters and use either an external contactor or an external MID switch aka BCS 2200.
I would not even stack more than 2 inverters without an external contactor!

Franklin WH requires separate 200A backup systems each for 400A, 600A and more.

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You clearly aren't looking for an all in one system. Why are you here?

If you want a system doing all the crazy edge cases you keep bringing up then piece together a system that has your precious 400a passthrough capability. This system isn't for you.

400a through some DIY equipment kind of gives me an uneasy feeling. What the hell are you powering?

Why am I here? I want stackable inverters capable of AC coupling hat can be stacked for a whole house 200A full backup system.
I would neither design nor build a single 400A backup system from stacked inverters that have 50A make/break rated relays, others on this thread were asking if it would be possible! And I won't rush to buy a newly released product from a company that does not have a track record for supporting such systems in a 200A stacked setup.

These are not the droids you are looking for.

DER Solar said:

Why am I here? I want stackable inverters capable of AC coupling hat can be stacked for a whole house 200A full backup system.
I would neither design nor build a single 400A backup system from stacked inverters that have 50A make/break rated relays, others on this thread were asking if it would be possible! And I won't rush to buy a newly released product from a company that does not have a track record for supporting such systems in a 200A stacked setup.

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There is no all in one in existence that meets your needs. Sorry.

All-in-one: EP Cube, QCELLS's QHome and soon Powerwall 3, Alpha-ESS stackable later this year
Whole house backup, AC coupling: stacked Schneider XW Pro, FranklinWH

DER Solar said:

Sure there are: Schneider XW Pro, FranklinWH, EP Cube, QCELLS's QHome and soon Powerwall 3.

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so, i suggest you go there then, and also be prepared to pay top dollar for them..

they are quite a different thing than these

Holy cow @DER Solar how many times are you going to edit your posts? Every time I've been on this thread your posts have changed.

DER Solar said:

All-in-one: EP Cube, QCELLS's QHome and soon Powerwall 3, Alpha-ESS stackable later this year
Whole house backup, AC coupling: stacked Schneider XW Pro, FranklinWH

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For at least the 3rd version of this post I've seen, I'll go ahead and quote so it doesn't change again.
I don't intimately know the details of all of these systems, but I know most of them are substantially different than the term "All-in-one" as used in this forum.

What's next, you're going to complain that these other all in ones have more built in battery capacity than the EG4 18Kpv all in one? (Hint, this all in one expects external batteries)

If you ever feel what you have to say is sensational enough to warrant an exclamation point, just assume everyone else (or at least me) will consider it absurd not sensational.

I've removed the meme I originally had posted here as perhaps it went too far

Please, folks, let's keep the discussion about the technical aspects. I am disappointed by the recent trend on the forum to make things personal. To me, it sucks all the fun out of participating in the forum.

Ok true a meme is too far so someone explain this to me:
What situations can possibly occur that would require the relay in a hybrid inverter, whose purpose is purely to disconnect the grid in the event of an outage, to pass current while it is disconnecting?

I can only imagine this with a system where it's severely underpowered. For example, 12kW AC backing up a 38.4kW load (using continuous numbers for both this inverter and a 200A breaker). In those scenarios, the inverter is going to shut down anyway so the problem solves itself. Any arc in the relay will be extinguished almost immediately, both due to the nature of 60hz AC crossing zero every 8.3 ms in addition to the fact the inverter will overcurrent in about the same amount of time (probably)

There is no scenario where >100A is passing through this inverter and it has a chance of seamlessly transferring.

GuyG said:

No. Unless I’m missing something, switching will occur every single time the load calls for more than the inverter’s rated output of 12KV, which triggers the need for AC pass through.

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Ehh... I don't think you are right there.
The relay will be on (pass through == connect the input of the inverter to the grid) all the time
The only reason it is there to isolate the inverter from the grid in case there is a power outage.

Rusty959 said:

What situations can possibly occur that would require the relay in a hybrid inverter, whose purpose is purely to disconnect the grid in the event of an outage, to pass current while it is disconnecting?

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The point about the relay not having to turn off 200A when the grid fails has some merit. By definition, the grid has gone down so it is no longer providing current. However, once you consider all possibilities such as back current from motor loads, I could imagine there could be a reasonable current. My reading of the relay spec sheet tells me that the relay can handle it so it seems like it is covered either way.

Rusty959 said:

There is no scenario where >100A is passing through this inverter and it has a chance of seamlessly transferring.

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That is an interesting point. If the load is beyond the capability of the inverter to service, the inverter will have to shut down.

This particular inverter has some impressive RunSurge capability. [14,000W (10 min.), 16,000W (5 min.)] For many households, 16KW is going to be an unusual and momentary event. Consequently, there is a good chance the inverter would ride out the transition. However, if the load is closer to 100A (24KW), it will probably shut down almost instantly.

Edit: Added paragraph space for clarity.
The appeal of this type of system is that there is no separate critical loads box so it is easier to wire up and you can choose what to power during a power outage.... you just can't choose to power everything. The trade-off is that at the time of a power failure, there is a possibility of the inverter shutting down before you can shed enough loads. For many (most?)households this will be a low probability.

I am investigating a similar system right now. I like this trade-off because I don't have to move a whole bunch of circuits to a separate box. Furthermore, my Sense system tells me I rarely have a total load above 16KW. However, I am wondering if I should move one or two circuits (like the oven) to a small grid-only breaker box. This would drastically reduce the possibility of the inverter being overloaded at the moment of grid failure and I would not be running the oven during a grid failure anyway. I hope to someday have an EV and I will almost certainly not run the charger through the inverter.