Quattro 48/3000/35-50/50 120V, connections to AC in 1, and AC out 1

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hmussman asked Oct 17, '18

Quattro 48/3000/35-50/50 120V, connections to AC in 1, and AC out 1

Harry asked: I am now installing my home power backup system, and using a Quattro 48/3000/35-50/50 120V, with a 10kWh AGM battery. In the configuration I am planning, the grid input will be on AC in 1, and the backup subpanel will be fed from AC out 1; a generator will be connected to AC in 2. With the current configuration, the Neutral of AC in 1 will be tied to the Neutral of AC out 1. Is this OK, or will it confuse the current measurement on AC in 1?

Johannes replied: No thats not ok, the neutral In/Out need to remain isolated

Harry asks: Can you please explain why they need to be isolated?

MultiPlus Quattro Inverter Charger

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Modifications Space

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Answer 1 · 2018-10-24T07:29:28Z

Johannes Boonstra (Victron Energy Staff) answered · Oct 24, 2018 at 07:29 AM

Hello Harry, The reason for this is indeed that the Quattro (and also Multi models) measure the current internally so bypassing the unit is not possible.

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colin commented · Oct 25, 2018 at 11:09 AM

Yikes! I have installed several back up systems with multipluses with common neutrals. Some have been running for several years without apparent problems - as far as I am aware at least! Something like this:

It simplifies the wiring, especially when introducing back up to a normal non-backed up site.

What consequences can be expected with common neutrals?

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common-neutral.png (62.2 KiB)

Answer 2 · 2018-10-25T12:51:19Z

hmussman answered · Oct 25, 2018 at 12:51 PM

Colin,

Thanks for your encouraging note. I am planning to do the same as your drawing, for the same reason: I don't have to transfer neutrals from loads to backup sub-panel, only need to transfer hot leads.

I understand that the quattro must carefully monitor currents on the inputs and the output, but if it only checks the current in the hot lead, there should be no problem with the above arrangement. I will verify with an experiment, and then hopefully be able to complete the installation.

Harry

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Johannes Boonstra (Victron Energy Staff) ♦♦ commented · Nov 08, 2018 at 07:39 AM

Hello, By wiring it as in the diagram the switching of the feedback relais is single pole and this should be double pole (according to regulations and safety of course). So have a common Neutral for input /output is NOT supported.

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