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Thomas avatar image
Thomas asked

2 Multiplus II in single phase in 3 phase system.

I have an electrision I don't believe is quite familiar with Victron. I have two Multplus II 48/5000/70

I just want to confirm so the installation will be correct.

The idea is to use two of the three phases in the house to power each Multiplus II, one for L1 and the other on L2, and then have separate AC output for each Multis with sub panels for different appliance in the house. The power from the Multis will not supply everything one will only supply Lights, stereo, refrigerator, etc and the other will supply Aircondition and water heater. The rest, like Owen, electrical heating will go thru the main breaker panel.

Is this a correct and possible connection?

Should the Multiplus be connected in parallel? As I recall reading the manual, splitphase is only for 120V Multis. This a European installation with 230V


Multiplus-II3 phasesplit phasemulti phase
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6 Answers
Michelle Konzack avatar image
Michelle Konzack answered ·

Do you use it as a pur "stand alone" or with a GX device on a singel battery bank?


With the GX device it is not possible to control two independant MultiPlus-2. I have the same situation and put them parallel using the VE.Bus cable.


Be sure, that the 230V cables support at least 44A, hence the recommended cabling shiuld be at least 6mm2 on each inverter.


And do not forget:


1) all PLUS wires must have the same lenght

2) all MINUS wires must have the same lenght

3) all AC cables must have the same lenght


And of course, the Inverters need ti ve on the same phase.


The setup of your electrician is working too, but you have no reliable control over the batteries SOC and if you use Lead-Acid cells, do not forget the BMV and the Balancer/s.

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Thomas avatar image Thomas commented ·

What do mean with the inverters need to be tied on the same phase? Is it not possible to use L1 for one inverter and L2 for the other as input to feed the Inverter. I have 3 phase 16A on each phase.

He connected and used 6mm2 AC, used for 25A cables he said, but I don't believe they are the same length, the left inverter is 80cm of the right and the cables run for 3 meters to two fuse boxes (subpanels), one for each inverter. The inverters are protected with a breaker switch and one 16A fuses each one for L1 and the other on L2 The inverters are connected to the same battery bank via lynx. Do I need a Clamp meter 112 in this setup?

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Thomas avatar image
Thomas answered ·

20230907-190112.jpg20230907-190058.jpgHi and thanks for your reply,

I have two Multplus II 48/5000/70 inverters, lynx and lynx shunt, 1 Cerbo Gx, 1 150/70 MPPT, 1 450/200 MPPT, 2 SOK LiFePo4 batteri20230907-190220.jpges (5Kwh each), 4x2 12v (105Ah)20230907-190140.jpg in series batteries are LiFePo4 with a separate shunt 500A. DC Cables to the batteries are 2,5m in length and 70mm2 in dimension.

Do you connect the inverters in paralell or as separate units? Do I need two Cerbo Gx?

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luphi avatar image
luphi answered ·

your setup requires the MPs to be independent, which is not support, if you want them to be managed by a GX device. Multiple GX devices are also not supported.

Options are:

  • group the MPs
    • parallel: requires both on same phase
    • 3-phase: require of course 3 MPs
  • Build two completely independent systems: 1 MP + 1 GX per system
  • run the MPs disconnected from the GX device and manage them manually


Maybe this is helpful:

https://professional.victronenergy.com/online-training/20/

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Thomas avatar image Thomas commented ·

Thanks! So phase shift is not usable? If I connect them on the same phase, I'am restricted to 16A on one phase. The idea was to use one of the inverter for aicondionening and water heater, when there is enough sun and during the Day. Is it posible to use assist function if the demand is more than 16A in paralell using the batteries? Is it possible to use the same batteries for both Inverters in a separate system?

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luphi avatar image
luphi answered ·

What do you mean with phase shift?

Yes, they can ( even more, they have to) be connected to the same battery.

(more preceise: they have to have the same DC voltage)

If you parallel them, they act as one with doubled power

if your grid supports 16A (~3,7kW) per phase you will end up with max. ~11,7kW on L1 and 3,7kW on L2 and L3.

3,7kW + 5000kVA + 5000kVA = ~11,7kW

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Thomas avatar image Thomas commented ·

One idea was to set up the inverters using L1 and the other using L2 for supply and configuration it for 120 dual phase, but this is not possible as I understand using the same Cebo GX, the Multis must be connected independently. Conversatio in another thread below, made me confused

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The other varian was to connect them in paralell

2 Multplus II connected in paralell on a 3 phase system using L1 only. Essential load on AC1 and non essential load on AC2 obove certain SOC of the batteries with help of the assistant. (Aircondition and Water boiler)

One phase is limited to 16A therefore the idea is to use the power assist to use batteries on peak obove 16A of AC1 and L1.

1. This setup will work I understand

2. Will AC1 run on Solar only when Power is enough, not taking power from the grid when using power assist?

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luphi avatar image
luphi answered ·

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Be careful! Never ever link ACin to ACout!

2. Will AC1 run on Solar only when Power is enough, not taking power from the grid when using power assist?

Do you mean AC1 = L1 ?

ESS tries to keep the grid to 0, but that requires an externel grid meter like the EM24 or the Multis can measure by themself, which requires them to be between grid and ALL loads



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Thomas avatar image Thomas commented ·

No, L1 will feed the inverters with power,

Critical load and its subpanel will be supplied from AC1 from the inverters


The idea is to feed one subpanel (water heater and Aircondion) on Ac2 from the the inverter depending on SOC of the batteries, but be able to via a transferswitch to chose, if necesary, the grid instead to that subpanel.


1. When using ESS, power assist will not work according to the manual. It is possible to set max feed in to 3680W (16A) and Grid set point to 0 in ESS and with the gridmeeter the Multi will only use the solarpanels and batteries to a set point and then start to charge the batteries to whatever i choose. Am I correct?

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luphi avatar image
luphi answered ·

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That is, how I did it. The switch has three ways: I-0-II and is used to have either the Multis inline or grid parallel.


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Thomas avatar image Thomas commented ·

Looks almost the same, but I want two loads devided, Critical loads on AC1 and non Critical on AC2. AC2 loads are only supplied above a certain SOC of the batteries, but with a switch to chose incoming supply from grid instead if nececery.

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flagunman avatar image flagunman Thomas commented ·
Did you end up finding an answer? I would like to do the same thing and supply 2 of 3 phases with the multiplus 2 (10kva) inverters. Did you bond the neutrals of the inverters and did it work? I'm a bit hesitant as the inverters are unsynchronized but can't figure out a good reason why not to connect them like this.
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larsea-dk avatar image larsea-dk flagunman commented ·
I do run a system with 2pcs MPII, one on L1 and one on L2. They are only connected to grid via AC-IN, which I understand is the only way due to I only have 2pcs MPII. I actually started with running 1pc MPII, but needed some extra power to supply enough to household and to use the large PV i have more beneficial. I runs with a Raspberry Pi instead of Cerbo running the VenusOS software and I have a smartmeter installed for the ESS system to have a grid near to 0watt

As I recall, I have used the Dual phase 120 due to the 120 angle phase shift to setup my MPII.

It has run fine for quite some time and I'm happy

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