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ykdave avatar image
ykdave asked

Shipped wrong multiplus but may still work out?

So instead of a multiplus ii 2x120 I was shipped a single phase multiplus ii. Of course this was a last minute install last week, for use over the long weekend, I did not have time to ship it back and exchange for the one i wanted


So after reading a little bit and figuring these things can be stacked to run split phase, I just went ahead and installed the one I had to get me through the weekend. Wasn’t ideal but it worked (had L2 bypassing the multiplus for generator operation and disconnected it from distribution and used L1 to power up the whole panel while inverting)


So I guess my actual question, since the single 3000w is marginal if a guy wants to run the a/c and several other gizmos, is it just easiest and best to buy another identical multiplus and run the other phase from that? Is there anything special required to run them in split phase operation?



System info: 2014 forest river XLR 395amp (42’ toyhauler), onboard 5500w generator, 50a shore power, 50a transfer switch, multiplus ii 24/3000/70-50, 2x 280ah lifepo4, mppt 150/100, 4x 455w array, cerbo gx, smartshunt



Multiplus-IIsplit phase
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Alistair Warburton avatar image
Alistair Warburton answered ·

You should check the docs but as far as I am aware, connecting two, 'identical', units to the same bus, VE.Bus will initially cause them to work as a parallel pare.

From there split phase is a configuration option THIS explains the concepts.

You absolutely can not install a second unit on L2 unless the units are aware of each other and working in sync. I expect you know that, but plenty of folk reading this will not, and worse, will not even appreciate why it it matters.

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nickdb avatar image nickdb ♦♦ commented ·
This is incorrect, please check your info before providing advice.

Just "connecting" them will not result in them becoming a parallel pair.

The system needs to be configured with veconfigure as a parallel set and both need to be setup, one as master, the other slave.

Parallel systems are considered advanced installations as it is easy to get it wrong if someone lacks the technical skills.

In the top right is a related resources tab, this contains links to the relevant docs and training.

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ykdave avatar image
ykdave answered ·

Yes I read what little bit of info was on the victron site regarding this, but what I found wasn’t very detailed at all to say the least lol


Being that this isn’t truly a split phase 120/240 setup on the distribution side I think complications are going to be minimal here.


Units would be connected on the ve.bus, when I was configuring the one I’ve got I never noticed any options there for multi-unit configuration but I’d have to assume that wouldn’t show up until another unit is detected in the system

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kevgermany avatar image kevgermany ♦♦ commented ·
The details are in the Victron Professional site, which is a free sign up and has the training you need.
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Alistair Warburton avatar image Alistair Warburton kevgermany ♦♦ commented ·
I didn't know that... I will be looking, thanks.
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Alistair Warburton avatar image
Alistair Warburton answered ·

I am in no way qualified to talk about multiple units... I have 2 MP's but 1 is a 48 the other a 24, the former feeding the latter from an AC perspective.

I did initially try connecting them to the same GX, AC in and out disconnected, just to see what would happen and the GX just assumed they were a parallel pare, which wouldn't have been pretty had they actually tried to do anything, they have been separate ever since, each with a GX.
Anyway that is how I know just connecting the VE.Bus kicks the whole multiple process off.
They can be stacked parallel and multi phase, you can even do both so split or 3 phase with multiple inverters on a given phase is possible, but I couldn't tell you how to set it up. I doubt its too complex though. However as will many things Victron, you can get this stuff wrong, and potentially do damage, with an incorrect setting so switch it on and see what happens isn't a good plan without some understanding first.

On the electrical side if your inverters are 120V and you don't need 240V I guess you could just wire them as two separate systems, on the AC side at least.

You would run into issues with charging and battery management though as there would be two competing chargers connected to the same pack.

If you don't need 240 why not just use a simple parallel pare and call everything L1, ok well L

What is the genset? If its a standard 12 wire machine it is probably in double delta with the neutral at the mid point, if you reconfigure to low delta you would get 120 single phase.

in the UK we are on 230 single phase so double delta with the neutral at one end. interestingly the AVR is typically on a 120V winding, even then. Have a look at some Stamford docs...

Here you go... Page 5

I build Hydro sites, small ones, so if it spins and make power I have probably messed with it at some point. We DOL 100kW motors, three phase, onto UK split phase, which is 460V single phase effectively at the motor, and balance the windings up with capacitor banks in a configuration called C2C. then we chuck a load more water at them and watch them generate...

You don't get much further from the box than that... :-)

Please keep the thread updated I am interested to see where you go with it.


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nickdb avatar image nickdb ♦♦ commented ·
The GX will "see" the devices on the bus. That is all. It will take the first one it discovered and manage that. The other is ignored you can only see its stats, nothing more.

This is NOT a parallel config. It does not do anything at all and is unsupported to do so.

It certainly does not "kick off the process" - that is manual and requires proper setup.

Joining two systems on the same phase without configuring them is a bad idea.

Wanting to help is great, but please don't give advice if you do not understand how it works.

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Alistair Warburton avatar image Alistair Warburton nickdb ♦♦ commented ·

That comment is wildly unfair...

"This is NOT a parallel config" The only person here trying to suggest that is you!

How about playing nice and actually trying to help. I am always happy to be educated but berated, especially when it isn't called for... Seriously dood!

"The GX will "see" the devices on the bus. That is all. It will take the first one it discovered and manage that. The other is ignored you can only see its stats, nothing more."

You have physically tested this have you? I did, with sufficient caution and and clear understanding of what I could do wrong, electrically, to ensure nothing got damaged.

(I want trying to parallel the units then either, just get data)

Your statement is wrong, to be fair I don't know how wrong or even why, because I lack basic knowledge, let alone detail, which was literally the first thing I said.

I forget if it was the CCGX or VE Configure, but something stated prompting for parallel setup info that I had not seen before, with two MP's on the same VE.Bus, so I disconnected.
Interestingly you can use a GX to grab data from a MP that is not considered part of the 'system' if the interface is GX-USB-MK3-MP. I did for a while.

I started with "I am in no way qualified to talk about multiple units"
Qualified in the middle with "I couldn't tell you how to set it up"
And finished with "you can get this stuff wrong, and potentially do damage, with an incorrect setting so switch it on and see what happens isn't a good plan without some understanding first."

Which part of that sounds like me giving advice, other than don't ask me about the details.

181 words in total, 51 of which is me saying I don't now how to do this, and another 69 where I am just describing what I did, none of which was about trying to parallel anything.

The rest is me paraphrasing the Victron document giving an overview of what is possible and not saying anything specific. + a bit of fluff.

Out of order... I tempted to report your post but as we all have bad days I will let it slide.


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ykdave avatar image
ykdave answered ·

Sorry been having grief with the captcha for some reason it just keeps spinning and spinning and nothing happens. Clear cache, try different browser, curse at it and eventually it works again!


Anyways, as for the suggestion of running everything off of the single leg… no, that poses the issues I mentioned in my first post. Although the Rv doesn’t utilize both legs for 240v appliances I still have to be backwards compatible with the split phase shore power and generator. Converting everything to single phase is not really feasible


I missed the link about the pro site on the literature about split phase/3ph, I’ll check that out tonight


The units I guess, while wired like a split phase configuration are really just acting like 2 separate units as they are just feeding individual busses in the distribution with 240 not even an option in the panel


I guess I was just more worried about making sure I didn’t do anything dumb and fry the inverters because I had an oversight on some silly little aspect of the install/config!



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ykdave avatar image
ykdave answered ·

Well as luck would have it, I received the other multiplus yesterday. Low and behold when I opened the box they had now shipped me the 2x120v model this time! I just can’t win here LOL


Anyways, I think I’m going to go back to plan A and just utilize the 2x120 as i had originally intended and find another use for, or sell the single phase unit.

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