Multiplus II: Parallel AND three-phase?

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matt-bowler asked Feb 21, '24

Multiplus II: Parallel AND three-phase?

Hi, we have three multiplus II 48/5000/70

is it possible to run parallel output (for more power on the single phase circuit) using AC out 1 and at the same time connect AC out 2 in tri-phase?

I am asking because the majority of our off-grid solar installation is mono-phase but our well pump and EV charger are tri-phase.

I understand the data sheet explains that AC 2 is only for loads that do not drain the battery but is it essential to have an AC input for that to work, or can it draw direct from the solar input?

Thanks,

Matt

Multiplus-II 3 phase

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Alexandra answered · Feb 21 at 08:48 AM

@Matt Bowler

Are you wanting to add another inverter in parallel on one phase? If you do you can't ESS.

AC2 out can be used supported by battery discharge (they are programmable). Both the 120v and the 230v models (not sure which one you have.)

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marekp commented · Feb 21 at 11:32 AM

@Alexandra

I have 3-phase system running ESS and have two MP-II in parallel on one phase.

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Alexandra ♦ marekp commented · Feb 21 at 11:40 AM

Interesting. Anyway documentation...

Not that is says it doesn't work...

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marekp Alexandra ♦ commented · Feb 21 at 12:56 PM

@Alexandra

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Alexandra ♦ marekp commented · Feb 21 at 03:26 PM

@MarekP

Not arguing whether you have a working assymetrical system. I am familiar with your posts about your system and answers.

It is just not a supported set up according to the documents. There are some things that are not guaranteed to work as expected.

If your system is doing what you need it to do, then that is great.

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marekp Alexandra ♦ commented · Feb 21 at 05:32 PM

@Alexandra

Only 2 years ago was suported because this "important" part read like this:

IMPORTANT:
Always update all units to the latest 400 firmware version (firmware update instructions).
Note that some parts of the description below apply only to 4xx firmwares.
All units in one system must be the same type and firmware version, this includes same size, system voltage, and feature set. The type is indicated by the first four digits of the firmware version number. For details, see the “VE.Bus Firmware Numbering System” section in the VE.Bus Firmware versions explained document.
Specify with your Victron distributor that you will be connecting units in parallel or multi-phase and identical units must be supplied.

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Alexandra ♦ marekp commented · Feb 21 at 05:36 PM

Correct hardware must be the same revisions and age for reliability.

The assymetrical set up being unsupported is not a new piece of information for ESS.

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Answer 1 · 2024-02-21T06:19:35Z

Matthias Lange - DE answered · Feb 21 at 06:19 AM

No that's not possible. AC Out 1 and 2 are coming from the same inverter.

Can't you just connect some of the PV power to the other phases?

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Answer 2 · 2024-02-21T09:55:39Z

ardje answered · Feb 21 at 09:55 AM

If you have a single phase PV on ac-out2 or straight to DC, it should charge the battery and through the DC it should feed the other 2 MP2.
Each MP2 will handle a phase in itself and nothing more than that.

However you are saying parallel and three phase...
Can you explain what you mean with parallel in your case.
Are your 3 MP3's configured independent, in parallel, or in 3 phase?

AC-OUT2 is intended for "non essential loads". You can turn it on and off depending on system status. The default is to turn it off if there is no AC-IN.
Your AC-IN is not needed to feed the PV power throught the DC network to the other inverters. However you will be limited by that one inverter: So max 70A @ 52V to the DC.
Using AC-OUT2 for those 3 phase loads on your MP2 should be wise, but you need to program the AC-OUT2 output to use other parameters to turn on/off, like battery almost full and still lots of PV.

The AC-OUT2 programming is referenced here:
https://community.victronenergy.com/questions/209073/multiplus-ii-ac-out-2-programming-w-veconfigure3-a.html

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Answer 3 · 2024-02-22T08:44:53Z

matt-bowler answered · Feb 22 at 08:44 AM

Thanks all for your answers.

I think that in the end, when the temperatures go up here, we are going to struggle to output enough constant load with just the three units... especially in mid summer at 40 plus... an air-conditioner in the room with them seems a simple solution but even then 4kW constant seems a little short of the requirement we currently have a 6k feed, and I think we need 5 - obviously I misunderstood the nomenclature!

I am going to try life with just the three and if need be I will order three more units and parallel connect them to double up the tri-phase power.

Regards,

Matt

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ardje commented · Feb 22 at 10:39 AM

Do you need 5kW over 3 phases or do you need 5kW in peak over 3 phases?

And do you have a 6kW feed over 1 phase or a 6kW feed over 3 phases?
And how are your MP2 connected right now? What is the max battery strain you can have?
To be clear: there is nothing wrong with feeding your AC through the MP2.
5kW over 3 phases can easily be handled with 3MP2.
But I would connect it to AC-OUT 2 and turn off AC-OUT2 if the total load exceeds 4kW on any of the MP2 or the battery voltage is below some setting. If you can have a real SoC, then use that.

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