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Martyn Duerden avatar image
Martyn Duerden asked

Multiplus II behaviour if AC output is connected to AC input

What happens if the inverter output becomes connected to the AC input during failure of grid?

Multiplus-II
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2 Answers
Rob Duthie avatar image
Rob Duthie answered ·

It has anti islanding function so it cant connect to the grid when it goes down. if it did it would over load and shut down as it is powering the grid and your street.

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Martyn Duerden avatar image Martyn Duerden commented ·

Hi, thanks for that, if im honest I am still not sure what theat really means...


Scenario


Grid fails, victron provides UPS function from batteries transfer switch moves load to backup therby providing the multiplus with power on its input effectively from its own output, a circular circuit if you like...

Thoughts?

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sean avatar image sean Martyn Duerden commented ·

The MP has a critical load output which is maintained in the event of a grid failure.

Any manual transfer switching that you implement should be break before make.

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Guy Stewart (Victron Community Manager) avatar image Guy Stewart (Victron Community Manager) ♦♦ Martyn Duerden commented ·

If you want to use a manual transfer switch, you will need to put the 'normal' loads on a seperate circuit than the multi AC-input. The multi AC-input would not be switched by your manual transfer switch.

The transfer switch would also need to be the type where there is 3 way switch with full isolation : grid - off - inverter. So the inverter output is also not ever connected to the Grid (it will make a horrible noise and probably overload).

If you connect the AC-input to the AC-output of the Multi somehow, it will give an error and shut down.

Normally, you would wire the loads into the AC-output of the of the Multi, and then you don't need the manual transfer switch. The automatic transfer switch inside the multi takes over and disconnects the grid when it fails.


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Martyn Duerden avatar image Martyn Duerden Guy Stewart (Victron Community Manager) ♦♦ commented ·

Thanks for this.


The issue is an auto transfer switch swapping grid load to backed up load when grid fails.

It works perfectly at the moment but implement ESS and thats an issue as the supply panel for the multi is powered from the load side of the transfer switch.

The transfer switch is similar to a star delta setup, either one or the other contactor is energised never both - mechanically & electrically interlocked.


The solution might be the victron Anti Islanding device in the ATS...


https://zerohomebills.com/product/victron-anti-islanding-relay-ufr-1001-e/

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boekel avatar image
boekel answered ·

Here's a bit of information about LOM (Loss Of Mains) detection:

https://www.victronenergy.com/live/ve.bus:grid-codes-and-loss-of-mains-detection?

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Martyn Duerden avatar image Martyn Duerden commented ·

Thanks for this.

I have done a lot of reading on this lately! it’s all education!

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