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penbarker avatar image

No-break Grid Parallel ESS Possible with MultiPlus-II?

I have an RV and would like to use a MultiPlus-II + battery as a direct generator replacement. Is it possible to set up the MP-II with a single, bi-directional AC line that can perform PowerControl/PowerAssist and UPS / no-break function? Like this:

I prefer this configuration so as not to rewire the RV with a second AC line (for pass-thru) to the generator compartment. I want PowerAssist/PowerControl capabilities when connected to shore, and uninterrupted power as the shore line is removed.

Thanks!

Multiplus-IIESS
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2 Answers
David Ferguson avatar image
David Ferguson answered ·

Grid parallel rules out UPS -

At least for the loads on the input side.

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tilo avatar image
tilo answered ·

It is not clear on the picture if the AC cable to the MP is connected to AC Out or AC In. In any case - it does not work like that!

If your cable is connected to AC-OUT: Your battery backup (UPS) is working. BUT - You cannot connect power coming from the grid to the AC Out, that will destroy the inverter! A generator or the grid must always be connected to AC IN.

If your cable is connected to AC-IN: The battery backup (UPS) is NOT working. The no-break load must be connected to AC Out of the MP if it should run only from the battery. If there is no external power on AC In, the MP will disconnect from AC IN and thus cannot "inject" or supply power to a load through AC IN.

You must connect the no-break loads to AC-OUT, and the generator and grid to AC In.

That means you need an automatic or manual selector before your AC IN to switch between the generator and the grid.

If you want to have 2 AC Input sources (grid and generator), consider using a Quattro instead of a Multiplus, because the Quattro has 2 AC inputs, which allows you to wire your generator to one input and the grid to the other input, without the need for an external transfer switch. Only one AC Input is active at a time, never both. AC IN 1 has priority and would disconnect AC IN 2.

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"You cannot connect power coming from the grid to the AC Out,"

how to do grid parallel ?