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Victron in U.S with Autotranformer 120v->240v split phase

If you decide you want a Victron Autotransformer, I've got one for sale, the 100a version. I'm actually going the opposite route, Multiplus-II with autotransformer for my small 240v loads to twin Multiplus-II's.
 
With regards to lost neutral risk.

I was looking into Multiplus II 1741 models (3000VA), stepping up 120 to 240, or using two with autotransformer to balance.

For the former case (step up), the neutral I believe always has to be galvanically connected to the output.

For the latter case, victron actually provides a diagram where the common neutral on the two inverters is NOT connected to the AT neutral.

I wonder why they do this, better balance between legs?

Does this introduce additional lost neutral risk?
 
I’m also curious as to whether folks on this thread have AC coupled to a 120V victron through an autotransformer.

I don’t see why that would not work, but maybe I’m missing something or a caveat
 
I’m also curious as to whether folks on this thread have AC coupled to a 120V victron through an autotransformer.

I don’t see why that would not work, but maybe I’m missing something or a caveat
Im curious of step up only as the neutral and ground can be passed through from grid->inverter->auto transformer-> 120v loads according to the diagram from Victron. 240v split phase is derived from step up AT. There is one video I found on YouTube of a person doing this with 120v inverter and passing through grid current
 
There is one video I found on YouTube of a person doing this with 120v inverter and passing through grid current
Yeah, that should be pretty straight forward except maybe calculating and installing the OCPD to prevent overloading the AT may be tricky. Maybe you’re supposed to rely on the thermal protections inside the Victron for some of it.

I don’t think the 120v units can AC couple without either two stacked units or a transformer. Except to other 120v inverters.
 
@Muir Industries what was the driver for going to two Multiplus?
Two major contributing factors for me personally. On the one hand I love the idea of what an Autotransformer does, on the other it’s a bit of “black magic”. I understand the premise of how they work, but my experience with them is limited and I’ve seen them having quirks.

My use case is also rather specific, I’ve got a trailer I use for work, but also for camping, that also is a home power backup station. Combine all that and things like neutral bonding become interesting and less easy to understand when an Autotransformer is thrown into the mix.

Especially with me using Multiplus-II 48/3000’s, it just makes more sense from a flexibility, output, and financial perspective to simply have two. I can do a LOT more things than I could with a single inverter and an Autotransformer.

I made the switch and I enjoy the outcome. It’s great.
 
My actual use case here, again a pretty one off situation, certainly not something that should dissuade anyone from an Autotransformer.

 
Thanks for sharing that. Yeah a MultiPlus 3000 (which is actually 2400W, the rating assumes PF 0.8) is pretty tight. The AT sort of just gives you two legs of 120V for convenience if used with one MultiPlus, and can’t power a lot of 240V equipment for the residential case.

I think it can maybe power one burner on a stove or run a 240V only air handler. Maybe a heat pump water heater in HP mode.
 
Thanks for sharing that. Yeah a MultiPlus 3000 (which is actually 2400W, the rating assumes PF 0.8) is pretty tight. The AT sort of just gives you two legs of 120V for convenience if used with one MultiPlus, and can’t power a lot of 240V equipment for the residential case.

I think it can maybe power one burner on a stove or run a 240V only air handler. Maybe a heat pump water heater in HP mode.
My use case is mini splits I have at home. Each pulls 1,000w or less, so one can do at least two. But now having two multiplus units I’m in good shape.
 
My use case is mini splits I have at home. Each pulls 1,000w or less, so one can do at least two. But now having two multiplus units I’m in good shape.
@Muir Industries
My friends use case will be on a small wall in garage which is why I was going down the path of 5k Quattro and AT. Also a lot less wiring, basically daisy chain to sub panel and one feed from main panel. I think the wiring gets a bit messy with multiple inverters.

Outside if more power, any issues with voltage difference on the 120v legs that caused issues with 240v from AT?
 
@Muir Industries
My friends use case will be on a small wall in garage which is why I was going down the path of 5k Quattro and AT. Also a lot less wiring, basically daisy chain to sub panel and one feed from main panel. I think the wiring gets a bit messy with multiple inverters.

Outside if more power, any issues with voltage difference on the 120v legs that caused issues with 240v from AT?
Only 240v appliance I ran was a pioneer mini split and it worked as normal. I hear you on the wiring side, but to me, I think I’ll stay with twin inverters, unless I’m stepping up to something like a 15k
 
I've been analyzing this from a redundancy perspective.

If you have two units, you will have a hot spare. However, if one goes down and you are using AC coupling, then you would no longer be able to AC couple. Boo.

If you have two units plus an AT, you get leg balancing (to some extent). In the AC coupling case, a single component failure will not break AC coupling. If one inverter goes down, the remaining inverter + AT can still couple at 240V. If the AT goes down, then the AC coupling can go directly into the inverters, bypassing the AT.
 
I've been analyzing this from a redundancy perspective.

If you have two units, you will have a hot spare. However, if one goes down and you are using AC coupling, then you would no longer be able to AC couple. Boo.

If you have two units plus an AT, you get leg balancing (to some extent). In the AC coupling case, a single component failure will not break AC coupling. If one inverter goes down, the remaining inverter + AT can still couple at 240V. If the AT goes down, then the AC coupling can go directly into the inverters, bypassing the AT.
I don't disagree, however in my (again very specific) use case the only thing that matters to me is having reliable power. Making the choice to use Victron equipment is the first step in reliability. I've never once had a true "issue" with Victron, sure I've had little hiccups which generally were related to me not thinking things through or pulling too much power, but I've never been left stranded.
I also don't "need" any of this, I have probably the most overthought work trailer out there. I kid you not it's 12 feet long and has 15kWh of battery power, talk about overkill. Heck, it's got split phase 120/240 via the twin Victron 3000's and doesn't have an internal use for it. The only scenario where I use split phase power is when using the trailer as a "generator" for my house. You know how often I need to do that? Never. I sincerely can't think of a time in the last 10 years I've lost power for more than an hour, if that.

Doesn't mean I don't have a plan though lol.

I think the answer is very specific to the individual though, I don't think anyone will go wrong either way, after playing with both options I simply decided that a redundant inverter outweighed the autotransformer for me. I do think that going with a larger 10k+ Quattro can start to make sense with the autotransformer though.

Maybe Victron will eventually release a "split phase" line and we'll all just be happy. Or, if I was smart, I'd have just used all 120v mini-splits knowing my future self would want to power them via a solar powered trailer ;)
 
I've been analyzing this from a redundancy perspective.

If you have two units, you will have a hot spare. However, if one goes down and you are using AC coupling, then you would no longer be able to AC couple. Boo.

If you have two units plus an AT, you get leg balancing (to some extent). In the AC coupling case, a single component failure will not break AC coupling. If one inverter goes down, the remaining inverter + AT can still couple at 240V. If the AT goes down, then the AC coupling can go directly into the inverters, bypassing the AT.
Are you talking about AC coupling like enphase to a DC based inverter system like Victron or Schneider?
 
Are you talking about AC coupling like enphase to a DC based inverter system like Victron or Schneider?
Yes.

The idea of having the extra AT for redundancy against a single inverter failure is starting to sour on me… maybe I might as well just buy a better backup generator and use that when losing one inverter breaks AC coupling.
 
Yes.

The idea of having the extra AT for redundancy against a single inverter failure is starting to sour on me… maybe I might as well just buy a better backup generator and use that when losing one inverter breaks AC coupling.
I didn't even know that Victron can do AC Coupling/Frequency shifting/microgrid forming. Have to read more on that. I'm stuck in analysis/paralysis right now. The second install I want to do will be for a remote cabin where the inverter will be in passthrough/backup running fridge and deep freezer. I need reliability which is why I'm seriously looking at Victron. Only there a few days a month and want good remote monitoring to keep an eye on it. Reliability is key.
 
I didn't even know that Victron can do AC Coupling/Frequency shifting/microgrid forming. Have to read more on that. I'm stuck in analysis/paralysis right now. The second install I want to do will be for a remote cabin where the inverter will be in passthrough/backup running fridge and deep freezer. I need reliability which is why I'm seriously looking at Victron. Only there a few days a month and want good remote monitoring to keep an eye on it. Reliability is key.
AC coupling adds a fair chunk of complexity (and in the case of a 120V grid forming inverter talking to 240v grid tied inverters, good chunk of extra cost bc you need extra hardware. Arguably you could just spend that money on a SCC and DC couple. Victron’s design rules for AC couple is kWp <= storage inverter output and 1.5 kWp per 5kWh battery, IIRC). The main reason I’m learning about AC coupling is that I have an existing microinverter setup.

I guess another use case could be if you have a very small number of solar panels or unusual arrangement, such that microinverters are superior. And in that case the system is maybe small and more likely to fit in the design rules.
 
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