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larsthebear avatar image
larsthebear asked

Looking for an inverter that can be used in a permanent off-grid installation

Hi. I'm looking for a 12V inverter with modest (~500W) power output that can be used to power an off-grid cabin with an existing electrical installation. The installation has a distribution board powered by a generator; the earth-neutral bond is made at the board, and connected to a set of earth stakes. I want to replace the generator with a battery-powered inverter (or provide a way to choose between them using a transfer switch).

So I need an inverter that can operate with earth and neutral bonded, and which will not impress AC voltages on the battery side when operating. I understand that many modern, transformerless inverters have no galvanic isolation between the AC and DC sides, so grounding the neutral connection will cause AC voltages to appear on the battery wiring -- if it doesn't actually blow up the inverter.

The 'Phoenix' inverters seem to be suitable for my application, because the documentation states that there is complete isolation between the DC and AC circuits. But I thought I'd better check.

Thanks

Lars


Grounding
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2 Answers
JohnC avatar image
JohnC answered ·

Lars, Victron made the 800VA Multiplus just for you. Internal MEN switching to/from the genny, 16A ac transfer switch, seamless transfer of power from the genny.

It's an inverter/charger, so will absolutely minimize genny run time. Note all the genny's power will 'passthrough' the Multi, and your existing N-E link will need 'reworking'.

The beauty? All seamless. Just start/stop the genny when you need. No light flickers, no switches, nothing else to do..

https://www.victronenergy.com/upload/documents/Datasheet-MultiPlus-inverter-charger--800VA-5kVA-EN.pdf

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larsthebear avatar image larsthebear commented ·

Hi JohnC. Thanks. Are you able to explain in detail what "reworking" means here? I think the existing N-E link would have to be moved upstream to the generator, so the inverter could connect its own link when the generator is offline (?) Are there any detailed wiring schematics? The manuals seem to be pretty vague about the whole subject of grounding.

Lars.

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Pat Davitt answered ·

Lars,

John is correct the Multiplus 800 sounds perfect for your needs. And, you are correct that there should only be one neutral/ground bond active at any time. To answer your question about "reworking" the Neutral/Ground bond:

The Multiplus assumes that any AC source (Generator/Shore Power) will provide a Neutral/Ground bond. When an AC source is not present (Inverter Mode), the Multiplus provides a neutral/ground bond through means of an automatic transfer switch. So what you need to do is:

1. Remove the bond from your distribution board.

2. Install a bond at your generator.

3. Wire the Multiplus exactly as described in the Operating/Installation Manual which can be found here:

https://www.victronenergy.com/upload/documents/Manual-MultiPlus--500VA-1200VA-EN-NL-FR-DE-ES-IT.pdf

Hope this helps,

Pat

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