EG4 6500EX with Auto Transformer

[Henderson]

Hi, I'm in the process of building out my 2x EG4 6500EX inverters in split phase mode. I think I'm going to have them fully off-grid as opposed to what I was looking at previously of having the grid as backup...seems to be simpler for the time being. One of the things that always concerned me was what happens if one of the inverters fail and how that sudden failure and losing one leg can impact any 240v loads. I had an idea which involves placing both inverters in 120V mode in parallel, so basically 120V AC with 13KW capacity and using the 120V paired out from the inverters with an auto transformer to give me 240V split phase, and then running that auto transformer to my main panel. With this method, if one inverter fails, I still can maintain 240V split phase albeit at 6500W instead of 13KW.

I'm interested to hearing your thoughts about this approach. I'm in the IT field so I'm always mentally occupied about failure scenarios and redundancy.

 

[Henderson]

Ahhh, never mind folks. Don't know what I was thinking (haven't had my coffee yet for the morning ). The inverters will only output 120V whereas the auto transformer needs 240V in so this approach wouldn't work. I guess this type of thing would work well for the growatts and similar single phase 240V inverters.

 

[Adam De Lay]

Hi, I'm in the process of building out my 2x EG4 6500EX inverters in split phase mode. I think I'm going to have them fully off-grid as opposed to what I was looking at previously of having the grid as backup...seems to be simpler for the time being. One of the things that always concerned me was what happens if one of the inverters fail and how that sudden failure and losing one leg can impact any 240v loads. I had an idea which involves placing both inverters in 120V mode in parallel, so basically 120V AC with 13KW capacity and using the 120V paired out from the inverters with an auto transformer to give me 240V split phase, and then running that auto transformer to my main panel. With this method, if one inverter fails, I still can maintain 240V split phase albeit at 6500W instead of 13KW.

I'm interested to hearing your thoughts about this approach. I'm in the IT field so I'm always mentally occupied about failure scenarios and redundancy.

If one inverter fails, the other should fault out as well. Similar to what happens when you update the firmware of one inverter, the other one goes into fault mode.

 

[Henderson]

Oh ho, thanks Adam. If that's the case then it means I'm looking for a solution where a problem doesn't exist . I would definitely want that if one inverter fails, the other one shuts down as well and no power is fed to the panel.

 

[Adam De Lay]

I would definitely want that if one inverter fails, the other one shuts down as well and no power is fed to the panel.

Exactly. That would be a HUGE problem for any 240v appliance connected.

Next time you update your firmware on one of your inverters (when you run the inverter update, not the display), you should see your other inverter fault to F80 something (I think) and your RGB bar should go red. You could probably also simulate the same thing by pulling the communication cables between the two inverters. If there's no communication, they should shut down to prevent any of these types of issues.

 

[dcg9381]

I'm interested to hearing your thoughts about this approach. I'm in the IT field so I'm always mentally occupied about failure scenarios and redundancy.

In the IT field we have lots of sensitive equipment. Most residential applications, I don't think that dropping one leg is really going to do much damage. What's going to happen is that 240V things just won't work on one leg.

And as mentioned if they go out of sync they both shut down, but certainly that can't happen to the MS.

I'm sure there are cases of residential power losing a leg that we just don't know about.

If I need 2 Inverters, the way we'd typically address it (in IT) is buy 4. I actually don't know if you're running 4 in split phase what happens if 1 fails. It would seem to be poor design to allow a single inverter failure to take down a whole series of these, but in the case of just having 2, I can see why you'd want to shut off.

One major downside of these in an "off grid" application is that they idle at about 120 watts each apparently...

 

[niktak11]

Ahhh, never mind folks. Don't know what I was thinking (haven't had my coffee yet for the morning ). The inverters will only output 120V whereas the auto transformer needs 240V in so this approach wouldn't work. I guess this type of thing would work well for the growatts and similar single phase 240V inverters.

The victron autotransformer can output 240V split phase from 120V input

 

[Henderson]

The victron autotransformer can output 240V split phase

The victron autotransformer can output 240V split phase from 120V input

thanks for that

 

[timselectric]

Any split-phase autotransformer can do it.
I wouldn't recommend it for large loads.

 

[Henderson]

Any split-phase autotransformer can do it.
I wouldn't recommend it for large loads.

not even the victron 100a AT?

 

[Henderson]

not even the victron 100a AT?

not even if using the victron 100a AT?

 

[timselectric]

not even if using the victron 100a AT?

I'm not a fan of doubling voltage, with an autotransformer. Just because of the doubled amperage on the input. They're great for boosting 10% or 20%.
I'm not saying that it won't work. There's just a lot of wasted energy transformed into heat.

 

[Henderson]

I'm not a fan of doubling voltage, with an autotransformer. Just because of the doubled amperage on the input. They're great for boosting 10% or 20%.
I'm not saying that it won't work. There's just a lot of wasted energy transformed into heat.

ok, i see where you're going...thks.

 

[gghawk]

Maybe this should be a new post, but it's the same configuration as this thread, just a different motive.
I have 2 EG4 6500s (+batteries+s.panels). They work fine with the following caveats: some flickering lights, and noise created through audio amp. Their excessive fan noise and idle consumption are not a problem for me. I suspect a true isolation transformer on the outputs would completely solve it, but they're ridiculously expensive. Maybe an Autotransformer (with the single, non-isolated coil would improve it enough?). Would also have the advantage of balancing the load, so I'd get the full 13KW, even when the two 120V load phases aren't balanced. I was looking at the Victron 100 amp version that you mentioned (only 730 bucks), but it says that's only in bypass? - the coil can only handle 32A, so it doesn't seem big enough (I need ~60A on each 120V leg). Waiting for SS to reply to my email... I guess I could parallel two of them, but that's getting close to the "not worth it" cost.
I wonder if anyone that's had electrical noise problems with the EG4s has tried an AT to resolve?
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[Batavian]

I don't know if the firmware has fixed this, but when I first installed my 2 6500s in January I came home to one inverter shut down (I can't remember if it showed a fault number) and the other one functioning running half of my circuits. So it is (or was) possible.