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logic28 avatar image
logic28 asked

Multiplus grounding when in charge mode only.

The Victron Multi inverter is supposed to lift the internal neutral to ground if connected to the grid however I see from the diagram that all the PE are still connected to the inverter chassis which in turn, being connected to the Grounding bus-bar, would still effectively bond the grid earth to the PV grounding electrode (underground rod)

I want to be able to potentially use the Multi’s charger but I do not want the grid grounding to be linked to my PV ground.


1) Is there a way to do so? Or should I simply lift the grid ground when charging? I expect that would be wrong if using the grid for loads but I would not be, subject to the next question:


2) Can the Multi II charge the battery bank without automatically switching or passing through the grid to my loads?

In other words, can the Multiplus charge and invert simultaneously?

From the instructions below it doesn't seem so but I'm just wondering

screenshot-2024-05-28-at-195817.png

Grounding
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2 Answers
Justin Cook avatar image
Justin Cook answered ·

No, in "charge only" mode the grid is passed through to loads and used to charge the batteries; the unit cannot invert and charge simultaneously.

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Alexandra avatar image
Alexandra answered ·
If you have grounded centrally and have a NE bond in the DB, then it will grounded anyway?

Why would you want to run an IT network?

https://www.victronenergy.com/media/pg/The_Wiring_Unlimited_book/en/ground,-earth-and-electrical-safety.html#UUID-a7fbe2a9-f339-7955-9305-4df3b1032efb

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flugs avatar image flugs commented ·

Salut, for the explanation of IT and TN networks, check page 50 of the Wiring unlimited document from Victron:

43562-Wiring_Unlimited-pdf-en.pdf (victronenergy.com)

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logic28 avatar image logic28 commented · 
If you have grounded centrally and have a NE bond in the DB, then it will grounded anyway?
Why would you want to run an IT network?

Hi Alexandra, thank you for your reply however I'm not sure I understand completely your wording.

NE for neutral earth ?

DB for distribution box at the building supply?

Not sure what IT network is referring to


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logic28 avatar image logic28 commented · 
Why would you want to run an IT network?

That is because I am not using the inverter AC input for any loads other than the charger itself so no safety device will be used in conjunction with that line at the installation point whereas the other building still connected to the grid would continue to work as per normal (TN -CS)

If you are familiar with grounding electrode rules you probably know that no two (or more) ground rods must exist in an installation (household) without them being directly bonded.

1) In the event of lightning striking the gradient in the earth could have a potential differential between two grounding electrodes can be as high as 20kV.

2) Furthermore, should the grid's neutral CNE (Combined Neutral & Earth) fail at any point somewhere in the vicinity, any other building in the area would use any copper or metal pipe as their return path to the transformer finding its way back by passing through my earthing cable resulting in a dangerous situation should I disconnect the PE which would now show 230v at that point if any load is active in the neighbourhood affected by the fault.

Basically, I want my off-grid system totally isolated from the grid with the only option of using the grid supply for charging purposes.

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