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peternielsen asked

Multiplus II and AC Out 2


I am trying to get my head around installation of a Multiplus II. I am installing this in Denmark as there is grid support for this but as far as i understand. The inverter must shut down it's AC Out 1 when the grid fails inorder to protect the technicians on the street to not feed in electricity BUT is there a way i can get power out on AC Out 2 while not delivering to the grid on AC Out 1 in that way i can power some critical things while power is down ? If it is possible i was thinking to put a switch 1, 0, 2 on those critical things so when power drops i can go an d switch it to get power from the inverter AC Out 2 if that's doable and allowed which essentially makes it a off-grid system for that period wile power is down. In the current system i am designing i will have a energy meter and run with ESS since the Multiplus II is a one phase system and the house system is 3 phase so the inverter will start producing energy when it's told from the energy meter there is a usage inorder to get the consumption to 0 as much as possible.


Multiplus-IIESSac out 2
2 |3000

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harold avatar image harold commented ·

I don't get your question.

AC1OUT is meant for the critical loads and will ge on in inverting mode, when AC1IN is off

AC2OUT will be only on when AC1IN is ON

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peternielsen avatar image peternielsen harold commented ·

@Harold i can see why it is confusing what i am writing. So i didn't notice the AC IN. So let me start from scratch. In the happy case i guess a user like me with a grid code don't use AC OUT 1 / 2 since the inverter will pump out what it's producing on AC IN in sync with the grid and my loads are also connected on the AC IN not directly but in the panel. When LOM happens the inverter will stop to produce on AC IN but will continue to do so on AC. OUT 1 is that correct understood ? If that's the case then i think i pretty much answered my own question. Just connect the critical loads on AC OUT 1 but the problem is that these loads usually run on AC IN e.g grid so now i need to add the Switch i was mentioning so i can move them from Grid to the AC OUT 1 connection, do i understand this correct ? I hope i make more sense now :)

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harold avatar image harold peternielsen commented ·

I still don't know why you need a switch.

But it switches like this:

And if you enter no grid code, it will never deliver current to the grid!


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1605010856003.png (46.1 KiB)
peternielsen avatar image peternielsen harold commented ·

Interesting since i am not interested on delivering to the grid but the problem is then that i need to put all my loads on the AC OUT 1 and live with the restriction of 32A that the inverter can handle. It would not be well seen by the electricity company since i will be pulling in-balanced from the 3phases i get from the grid.

By using the AC IN and enabling grid code i would not need to move cables around but then the problem is that if i don't have grid i don't have power to anything unless i also use the AC OUT 1 on some critical things. I am not sure i understand it correctly but i understand than when there is AC IN then AC OUT 1 and AC OUT 2 are all coupled together.

So as far as i see it i have few options :

1. Use grid code

Few options :
- Connect all loads to AC IN and nothing to AC OUT 1 -> benefit no change in cabling but downside is no power on LOM
- Connect all loads to AC OUT 1 (assuming i can keep it under the inverter range) and no loads to AC IN -> benefit is power on LOM
- Connect non critical loads to AC IN and critical loads to AC OUT 1 -> benefit when AC IN is available AC OUT 1 will be powered of mixed power from battery and grid. When LOM AC OUT 1 will be disconnected from AC IN and AC OUT 1 will be powered from battery.

2. Don't use grid code

Options :
- Connect all loads to AC OUT 1 (assuming i can keep it under the inverter range) and no loads to AC IN -> benefit is power on LOM

But here is what i don't understand, if you don't use grid code how can it ensure it doesn't feedback to grid in the case where the inverter needs to mix power from grid and solar e.g not enough PV/Solar ? Looking at the drawing you attached the AC IN switch will open to feed in the power needed for AC OUT 1 which it needs to mix with the one coming from battery.

Also what happens to the loads on AC OUT 1 if the inverter turns off by some reason ? My guess is that all loads on AC OUT 1 would be shut down even though i have grid connection my point being, it seems better to leave the loads on AC IN but have a way to switch them AC OUT 1 if needed but the downside is that i need to do that manually eg. i need to flip a switch.

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harold avatar image harold peternielsen commented ·

I think you are on your way now!
But with your thoughts you need to contact and have a chat with a Victron specialist in Denmark ;-)

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