I recently got a Victron ESS system with 2x multiplus 48/3000. In a 3-fase-network.
Thanks to power assist and phase compensation, this is more than enough for our (heavy consuming) household. We sometimes have peaks of more than 6Kw, but it then takes from the grid and pumps the same amount back into the grid on the other phase, so that you actually use the grid as a buffer. The second inverter then helps the first.
However, if we go off-grid, the phase compensation disappears, and we only have 3000W per phase. The kettle on while the dishwasher is running, and… Whamm… the whole system goes down…
Just to mention: I have everything on AC-OUT-1, because in emergency cases I want to be able to do everything as we are used to. But that does not quite work…
My question now is:
isn’t it possible to imitate the phase compensation in off-grid mode?
Or would it be possible to connect the three phases together in off-grid mode, and connect the inverters in parallel, so that I have 9Kw of power?
Or do you know an other solution?
My power supply is not the problem: I have a battery that can continuously supply 150A at 50V and 6.5Wp solar panels, (that is together approx. 14Kw), so there is enough power on that side to absorb those peaks.
You have 2 3000 va multiplus, thats 2x 2400w cont @25 degrees
There is no ac in connection when off grid, so no metering and system can not monitor phase compensation
You also can not “flick a switch” to set them in parallal when off grid, that needs complete reprogramming, so also no phase combination is possible
You could connect heavy loads on ac out 2, then they will switch off when going off grid
If you want to run like normal, you will need a bigger system…
Dear Marc, thank you very much for your answer. You are probably right, that there is no solution…
Still, Victron is a system with unlimited possibilities. Is there no smart option?
Here is a video of Andy from Offgrid garage
He connects 1 of the 2 inverters as a generator, via the built-in relay this inverter steps in when the power demand increases. Very smart! In this way he solved my problem in a single phase setup.
But how to do in 2-fase setup ?
In ongrid mode you could keep everything on 2 phases, at 120 degrees, and then not use the third fase and the third inverter.
In offgrid mode a switch would have to connect the phases together. And an other switch should switch over from the grid to generator feed. Like it works in an RV or a boat. I don’t see that very clearly yet.
Then the third inverter can supply extra power as a generator on all phases.
Or am I missing something?
I see a big dis-advantage: the third inverter does nothing in ongrid mode…
Your solution is larger inverters.
Cascading (serial) inverters is not supported, though some people do this, but it requires knowledge and experience, it is not something to be tackled by beginners.
You also cannot just change configurations with a switch.
It would require major wiring changes and a full reconfigure.
Bottom line is your current system is too small. 3000VA inverters (2400W as stated above, less at higher temps), will not power loads of any significant size.
A 2000W kettle would use most of one system on its own.
Yes, Nick, I know, but in belgium only 10 Kw of inverter power is allowed in an home network. So, If i swich to 3x multiplus 5000, they wil count it as an industrial installation, with very much paperwork and costs extra.
The solution that i am going to use: Dividing equally over the 3 fases the devices that uses more power. And than tell al family members: just one device per fase.. I hope this will work…
Joost
When you install an installation of more than 10 kVA as a private individual, you must register as a self-employed person. In addition to administrative obligations, it also means that you will have to pay taxes on the income from the injection. For further questions about this, contact the FPS Finance.
