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rcure avatar image
rcure asked

Neutral ground bond, connecting ground from ac 1 and ac 2

I have a question pertaining to neutral ground bond.

I have a Victron multi plus II 24v 3000 watt 2x120.

My shore power is supplied by a generator with a neutral ground bond.

My understanding is the inverter bonds the neutral once Battery power takes over.

Ac out 1 is supplied by battery back up and shore power.

AC out 2 is a pass through when shore power is available.

I want to install a transfer switch between ac 1 and ac 2 to run my air conditioner.

The transfer switches I’m finding don’t switch the ground and only the hot and neutral.

So the only solution I see is to tie the grounds together from ac 1 and ac 2.

So the scenario I think I have is,

when ac 2 is supplying power the neutral bond relay in the inverter opens unbonding the neutral and power is supplied by the generator(generator has a bonded neutral).

When ac 1 is supplying power the inverter bonds the neutral.

When ac 1 is supplying power I assume the bonded neutral on ac 2 is still bonded at the generator.

In my mind this creates two bonded neutrals .

Could someone describe to me how this works?

Multiplus-II
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1 Answer
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chrigu answered ·

First of all, keep in mind that the 2x 120V units dont produce an actual split phase in inverting mode. See the powerflow diagrams at the end of the manual
https://www.victronenergy.com/media/pg/MultiPlus-II_12V-24V_3kVA_2x120V/en/UUID-1ff22c09-d3c7-a2e1-1f4e-4fd90f9a5e89.html
So if your Aircon needs 240V between phases, then it wont work on inverter. For a true split phase system you would need two regular Multis in split phase config, one supplying each phase.

As you can also see from the powerflow diagrams, the neutral and earth is never broken between both outputs

Appendix B is the block diagram, but it tells the same thing

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