I’m planning to add a Multiplus II 48/3000 to my PV Enphase system as a battery backup.
The PV has 8 panels with 8 IQ7+ microinverters, output 220V phase-phase. The grid is three phase 220V/127V.
Essential loads are some 1kW peak and are connected to the same microinverters phase-phase 220V or phase-neutral 127V.
The third phase is used only for no-essential loads.
How could I connect the Multiplus on my system?
Thanks.
Mark Jordan
Maybe the same “Problem”
I guess the only solution will be using two Multiplus, one for each 127V phase.
Is there a 48V 1600W or 2000W máx that support grid injection?
The problem is not so much the voltage but the missing N conductor … as you have a 3-phase connection and NO N it will not work.
Read again my first post and you will see I have the neutral conductor. Voltage between neutral and any phase is 127V. Voltage between any two phases is 220V.
Sorry … Then take a look at the 2x120V (splitphase) Versions …
I found they are not compatible because “The inverter output is 120 V single phase. In invert mode, the MultiPlus connects both output lines (L1 and L2) together to provide 120 VAC to loads on either line.”
This way I’ll not have 220V. 
Then you need a “Autotransformer” like :
But you can only use one phase … You would need also an autotransformer for the second phase
Basically, you want your microinverters to continue to be supplied from the 220V mains after a failure.
What power will your PV side have?
The PV can go to 2700W max on 220V.
Essential loads, 1000W max on 220V.
If I use a autotransformer, the Neutral wire must be connected to the middle terminal.
But wait, the first diagram in that datasheet shows the 240Vac inverter without Neutral connection!
And ?
But you need a solution with 120V → 240V in the event of a power failure for your MP3000 and your MicroWR
The transformer is connected the other way round
If I could use the 220V inverter connected to L1 and L2 without Neutral connection, then problem solved.
I can use an autotransformer for any 127V load.
“If I could use the 220V inverter connected to L1 and L2 without Neutral connection, then problem solved.” … Problem not solved … Victron gives no guarantee of fault-free operation at 230 split phase without N with a 230V inverter that actually requires an N conductor.
Hence my link to the other post above.
“I can use an autotransformer for any 127V load” … Is this a Question ???
I don’t understand that autotransformer diagram showing “Neutral (not connected)” if the inverter needs N connection.
So I need to use two 127V inverters.
If I use only one 120V inverter with an autotransformer, how to connect the 220V PV?
Unfortunately the autotransformer cost here in Brazil is a little less than a Multiplus 48/2000 127V.
So it seems the solution is using two Multiplus 48/2000 127V.
Or one Multiplus 48/3000 without N connection 
.
The operation in Brazil is completely different to here in Europe where it is a matter of a feed-in and all kinds of guidelines have to be observed.
It may well be that a 230V Multi works wonderfully on a 127V split system.
But I don’t know that.
Is there someone at Victron that could possibly shed some light on this?
I like the idea of using only one inverter.
Edit:
After reading the docs available, it seems the solution in my case would be keeping the ground relay always open.
This way I could connect the MP input to L1 and L2 without N and the AC out would feed the loads with L1 and L2.
Maybe I’m missing something here, but I guess it should work.