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Mixing 3phase and 1 phase inverters


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HI Guys

I need a little advice and ideas from the forum members.

I attach hereto a drawing of my suggested installation and would like to know whether it will do the job, or am I missing on something here?

Would you kindly make any suggestions and feel free to ask questions, Please

Many thanks





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Sorry Guys

Just to explain what my concerns are:

1. 2 x 10kw would be used as MPPT controllers , no batteries connected. They will just generate PV and switch off when the grid fails.

2.The Sunsync single phase will have batteries and PV and will be connected to my essentials only

3. What will happen if the grid goes down, but the sunsync is still generating power

I am scared that the 2 10kw's will think the grid is still available and start pushing power back into the grid ( Dangerous !! )

Is there perhape anything else thet I should consider ?


Many thanks


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Good afternoon Oom Chris

In theory the 8kW single phase unit will not have an effect on the 10kW units, as when the grid fails the 8kW should in theory also drop all feedback on P1, and only supply the essentials DB from PV and/or Batteries as needed.

The 8kW unit output is isolated from the input phases of the 10kW units, and the only common share is P1 on all three inverters.

I believe that no one can say for certain exactly what will happen, as neither the users, nor the designers in my opinion catered for such a scenario of mixing 2 X 3 Phase units with a Single Phase.

The other theory is that the 10kW units will stop feedback the moment that any of the phases drop out. This can be tested while the 10kW units is feeding back by dropping one of the phases via the breaker for that phase if 3 separate breakers in place, and making sure the other two phases stop feedback with one phase down.

As a safety precaution if it was my install or plan to install, I would add a 3 phase contactor of proper rating in the line as well, ensuring that phase one is broken by the contactor between the 8kW and the 2 X 10kW inverters. Phase 2 and 3 also broken if needed, but for me rather break all.

Then the contactor to be energized from Phase 2 or 3 will ensure once either of Phase 2 or 3, or all phases fail on the grid side, there will be an isolation barrier between the 8 kW unit and the 10kW units. Then the 8kW will operate in normal grid loss mode and supply the loads.

Once grid restores, the contactor will energize from P2 or P3 as connected, and normal feedback can resume.

If one is concerned about grid fluctuation on restoration, one can add a delay timer to the contactor to ensure grid is available for xx seconds before the contactor is energized.

Hope this helps a bit.


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