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I am intending to buy a Multiplus II 3000VA GX.
With my 10 kWp installed Solar power and a 9 kW inverter, I will not meet the factor 1.0 requirement for AC coupling.
Can I still use a Multiplus II for ESS , even if it is not AC coupled ?
Can I connect the Multiplus grid-parallel in this case ?
What happens in case of grid-failure if connected grid-parallel ?
Can the Multiplus power the connected house phase in case of grid failure from the batteries then ?
Thanks much for your help.
Daniel
Yes, it is absolutely fine to have any sized AC PV connected on the grid side (AC-Input) of the MultiPlus.
In the case of grid failure, your AC-PV will shut down. Your essential connected loads, connected through the Multi's AC-output, will continue to run as long as there is battery power.
Is there a scenario where the PV from the grid inverter can continue to provide energy to the Multiplus inverter?
Thank you Guy, very helpful answer.
Two last questions:
1. If I do not connect anything to the AC-OUTs, there will be no UPS function in case of grid failure, right ?
2. With grid being okay, ESS will still work when nothing connected to AC-OUTs ? So in Multiplus II inverter mode, the current from batteries will flow back trough AC-IN ?
Thanks again for your help.
as for 1)
UPS function (if active) does only work on AC OUT-1
So you can connect anything to AC OUT-2 and UPS will not be active in case of grid failure.
If you connect nothing to AC OUT-1 and there is grid failure, UPS still may be on - just draw only little power.
The determining factor if UPS goes on or off is whether you enable or disable it in the configuration - independent of what is connected to the OUT-1
as for 2)
I'm not sure I understand the question.
If ESS and grid ok, then Grid inverter ok, then power on AC IN (but really this is independent of grid inverter)
Therefore, if nothing is connected to AC OUT-1, inverter has nothing to do and charger may load batteries if needed.
Hi @daniel1976,
PetaJoule is right on point 1.
The UPS feature is only available on AC-output of the Multi. With nothing connected to ACoutput, it will do nothing in a grid failure, except slowly self-discharge the batteries.
On point 2;
It is possible to have the Multi quite functional with nothing connected to its AC-outputs. It will push to support all the loads on it's side of the energy meter, charging from the AC PV, and discharging from the DC battery, and attempting to keep the grid import/export at 0W (or whatever you have set it to be on the GX device).
However you are missing out on one of the best features of the product, it's high grade grid forming ability. I imagine most people will be quickly frustrated if their AC PV, battery and off grid capable inverter does not run any of their loads during a grid outage.
Consider at least rewiring the lights and the power points circuits so the fridge stays cold and the internet stays on.
Thank you Guy,
I will certainly find a way of using the grid forming ability in case of grid outage. However I can not just hard-wire my house AC loads that are connected to the PV inverter directly to the Multiplus AC-OUT 1. That would power the 9kW PV inverter in case of a grid outage and cause the issues due to not meeting factor 1.0.
I am thinking of a manual switch that can disconnect the PV inverter and connect my house AC loads to Multiplus AC-OUT 1 when needed.
Anyway, thank you for the quick, friendly and knowledgeable support, that indeed helps for a purchasing decision. The Multiplus II seems to fit my purpose very well.
It should be possible to isolate and seperate the loads and the AC PV inverter (unless they are very far away from the Multi, and only run down a single line?).
