question

daza avatar image
daza asked

Multiplus2 48/5000 but more so 48/8000

Hi everyone, I want to try and design my system but what I need to know is can I back feed AC to the Grid through AC1 out for critical loads?

what I want to do is run the whole house off of 48/8000 and in the event of a power cut island the house from the grid and have my AC solar still running on AC1 out. Would power going back down AC1 out creat a problem?
The AC solar is only 3.3Kw. So am I right in thinking that I can have the flow back to the grid when the grid is up and solar is coming down the AC1 output to the grid and when Grid power goes that stops my PV power from going back to the grid but keeps it in my house? Just need to know so I can organise cables and that I’ve got it right in my head that the 48/8000 can do that as I need the 100amp switch relay so that it can run the house without overloading.

Multiplus-II
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gazza answered ·

Yes, as long as the grid is only ever connected to AC In.(as per the diagram I posted earlier). It is ok that the PV is not large in comparison to the inverter, so you are well within the 1:1 rule . When the essential loads are satisfied and the battery is full:- with "Grid feed-in" enabled in the ESS settings and sufficient "Input current limit" set In the Multiplus settings the excess will be fed back to grid via AC In.

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gazza avatar image
gazza answered ·

No you cannot connect AC1 OUT direct to Grid while the grid is available!! (I have seen other posts stating that this could damage a Multiplus)
You can however "isolate" yourself from the grid and connect AC1 OUT to your house wiring (3pole break before make changeover switch from AC IN to AC OUT in an ESS system??) with the correct cabling and protection. (There are other posts that I have read, using auto-changeover switches that monitor the incoming grid availability)

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gazza answered ·


ess.jpeg


You can do as above, with Grid tied solar inverter connected to AC OUT. But, you can't connect AC OUT directly to grid. The AC IN can be connected to grid and is essentially bi-directional, which is where your grid feed in comes from.


ess.jpeg (16.3 KiB)
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daza avatar image daza commented ·

Hi Gazza, right so it is a relay/switched relay I think what I said didn’t come across well. If I wire the PV to the AC out, and the Grid is running so the relay is closed ie essentially connected to AC in.

As it is AC current from the PV to the inverter will that feed back to the grid if the grid is working and the Batteries are full and the house isn’t pulling what the PV is producing? So in essences providing off Grid PV and Grid tie at given parameters are met? My PV size is only 3.3kW so an 48/8000 is over kill but would handle the 100Amp switching that I would need if I wanted to fully load 100Amps in future ie car charging and so on.

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