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gyrex avatar image
gyrex asked

Help with Fronius Symo 15kW 3-phase and Victron MultiPlus II configuration

Hi,

I'm planning a new solar installation on a new house build and was hoping someone could please help me determine the best way to plan and configure it. I'm aware of the 1 factor rule but I'm not sure how it applies to 3-phase installations - if I plan to install a 3-phase Fronius Symo 15kW inverter, does that mean I could install 3x Victron MultiPlus II 5000VA units connected to each phase?

This is the configuration I thought would work best but I'd really appreciate help on whether this configuration is valid and if anyone has thoughts on this design?

Some questions:

  1. Can I use the Fronius smart meter to monitor consumption or would I be better using the Victron smart meter?
  2. Given the somewhat disparate use of inverter vendors, is it possible to view and monitor the system using one portal/monitoring system?
  3. Is there a bypass on the Victron MultiPlus units in the case where the batteries are charged so there's no 'processing' or loss as the electricity passes from the Fronius Inverter to the home's loads?

Many thanks in advance.

Multiplus-IIMPPT ControllersFronius3 phase
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2 Answers
daryl avatar image
daryl answered ·

Hi @gyrex


I'm just about to install a very similar system, although I have 2 x 8kW Solaredge 3 phase inverters (that I'll limit to 7.5kW each). So I'll answer based on the research I've done.

I'll take a stab at your questions:

1) I believe it's circa 72A for the 5000VA model Eg the incoming 50A + ~21.7A from Powerassist (5000VA/230V)

2)This thread seems to indicate you can (this is my intention as well) https://community.victronenergy.com/questions/3698/quattro-limit-charge-power-from-grid.html

3) The factor 1 documentation says: "This limit is called the factor 1.0 rule: 3.000 VA Multi = 3.000 Wp installed solar power. " So you should be fine.

Daryl

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gyrex avatar image gyrex commented ·

Thanks for your excellent response Daryl.

  1. Can you tell me where I can find this information about Powerassist for the 5kVA MP2? The manual only makes mention of an extra 13A for the 3000VA model. If this Powerassist figure is correct, does this mean that the 5kVA MP2 can draw a total of 71.7A from the grid? ie. if there's no battery capacity remaining for the inverter to invert. Also, is there some time limitation that Powerassist can operate?
  2. Thanks for the link! I'll have a good read of it
  3. Thank you so much for answering this question.

I actually didn't realise that the MP2 can pull up to 50A from the grid for each inverter. If this is the case, this should be plenty of power to run my entire load across AC-out in 3-phase. I thought it was limited to 5kVA but it makes sense now that this is only the capacity of the inverter operation.

To be clear, if I have 3 inverters in parallel, without Powerassist I can run a total load of 150A across all three phases (50A each phase)?

Thanks again for your help mate!

BTW, here's the excerpt of the manual that only mentions the 3kVA MP2

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daryl avatar image daryl gyrex commented ·

Hi @gyrex,


1. I made the assumption based on the the datasheet that says:

Cont. output power at 25°C: 3000VA for the 48/3000/35-32 and 5000 for the 48/5000/70-50

Power assist will only occur when there is battery capacity. The input into the 5000 is limited to 50A.

>To be clear, if I have 3 inverters in parallel, without Powerassist I can run a total load of 150A across all three phases (50A each phase)?

Yes, that is the situation, you just have to distribute your load across the phases equally. Note though that technically you won't have any inverters in parallel in Victron speak (they use that to say multiple inverters on the same phase). You'll have one per phase in a 3-phase system.

Daryl

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gyrex avatar image gyrex daryl commented ·

Thanks again for your response Daryl. The maths work out regarding Powerassist. If I'm honest, Victron could do a better job at describing the function of Powerassist on their website - it isn't really clear to me.

I think I'll have plenty of power for what I need. Initially, I was worried that the total load across AC-out was 5kVA but now I see I could potentially have:

50A from grid on each phase (150A total)

Potential of 65A shared across all three phases via Fronius PV

21A on each phase from batteries

This Victron solution is perfect - much more comprehensive than other AC coupled powerwall solutions which are typically limited to single phase operation and are locked into proprietary battery banks. Plus it means I can add as much battery onto the system as required.

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Daniël Boekel (Victron Energy Staff) avatar image
Daniël Boekel (Victron Energy Staff) answered ·

Hi @gyrex


1. No you need a supported grid meter like the EM24

2. No problem fronius is supported, the MPPT's also

3. That is not how ESS works, but when the batteries are empty (or: at the minimum configured SOC), the system can go into 'passthru' mode, where is draws less power.


  1. Can I use the Fronius smart meter to monitor consumption or would I be better using the Victron smart meter?
  2. Given the somewhat disparate use of inverter vendors, is it possible to view and monitor the system using one portal/monitoring system?
  3. Is there a bypass on the Victron MultiPlus units in the case where the batteries are charged so there's no 'processing' or loss as the electricity passes from the Fronius Inverter to the home's loads?
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gyrex avatar image gyrex commented ·

Thanks for your help Daniel, I really appreciate it! I've updated my proposed system design and I have a couple more questions relating to it if you don't mind?


  1. Given the diagram with all the loads connected to the AC-Out of the inverter, if there's a load on L1 (eg. 9kW) which exceeds the 4000W inverter capacity on that phase, can the inverter draw extra power from the grid connected to AC-in above and beyond its inverter capacity? If this is possible, what's the maximum continuous load which can be drawn on AC-Out?
  2. In Venus GX, is it possible to completely disable charging the batteries from grid power and only use excess solar power to charge the batteries?
  3. I just noticed that the maximum output power of the MultiPlus II 5000VA inverter is actually 4kW, if I'm using a Fronius 15kW inverter, will this break the 1:1 factor rule given that the maximum power from the 3 of the MP2's in parallel will be 12kW? This might throw my idea/plan into the bin :(
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