question

As a UPS type system you need to take the loads out from AC-OUT, a series configuration with theMultiPlus between the smartmeter and the load.
Power goes in to AC-IN and is passed through to AC-OUT. When the network is unavailable at AC-IN then it will disconnect and AC-OUT will continue to provide power from the battery.

Victron inverter/chargers are set up to pass the grid power through them to the loads they supply: Grid to AC IN, AC OUT to distribution panel. That is the only way they will work.

The Multi has an AC input relay that connects the grid to the inverter/charger core when grid power is within usable values (voltage and frequency). The inverter/charger core is connected directly to the AC output(s).

In normal operation, the AC input relay is closed connecting the grid to the loads with the inverter/charger core charging the batteries or assisting the load when grid isn't sufficient.

When the grid falls out of acceptable values, the input relay opens and the inverter/charger core immediately begins supplying power to the loads from the batteries.

For redundancy, an inverter bypass transfer switch is recommended that would route the grid power directly to the loads. This allows the inverter to be shut down for maintenance.

While connected to the grid, the voltage and frequency of the grid appear at the Multi's AC output. In situations where the grid power isn't stable enough for the loads it feeds, separate battery charger and inverter should be used. In this case, the grid feeds the charger keeping the batteries topped up and the inverter powers the loads from the battery. In normal operation both the charger and inverter are subjected to the load power 100% of the time. The benefit of such a system is the voltage and frequency supplied by the inverter are independent of the grid. Boats somethimes use this system so they can accept 120 volt 60 Hz or 230 volt 50 Hz shore power and still run motors, etc the rely on a specific frequency of AC power..

Hi

You can run them in parallel mode with the grid, and have a AC1 feed the critical loads and the AC2 to other non critical loads, so you can still export surplus power as well with a AC coupled PV inverter.

You can also wire in a change over contactor as well, to supply all the loads if required.

This is what is have done with my test system.

@Rob Duthie

thanks for your repl(ies). we only have one Load, and that is 'the house' there are no significant loads in the garage, just a fat cable going out of the garage to the house, so AC-OUT-2 is redundant, for us.

have you got a granular and detailed circuit diagram?

if you look at the typical circuit1.png below - i keep seeing similar to this everywhere online.

ignoring the orange 'critical loads' - n/a.

this looks like the blue victron inverter is connected in parallel. that doesnt look like a multiplus to me, so is this possible with the multiplus II ? i'll assume it's a multiplus for this post.

this diagram isn't detailed enough for me.

the blue arrows going to and from the top of the multiplus: does this represent two Lives and two Neutrals? one going to the AC-IN-1, and one going from AC-OUT-1 to the BLUE Loads/the backbone (as i would call it).

so i connect AC-IN-1 from the henley blocks (there's some henley blocks between smart meter and CU, one Live, one Neutral) and connect back to the backbone by running from AC-OUT-1 back to the henley blocks?

would this represent the blue arrows notation above the victron multiplus? do you think

thanks your replies, everyone. the fog is lifting. which is awesome, because i have to understand it as i'm the one who has to debug it if it goes wrong some day in the future.

i'm thinking multiplus's are meant to be connected in series between the feed and the load. like you say @WKirby the design should simply move the connections to make it go in series.

this is just a thought in my mind. and i may be comparing apples and pears here wrongly. my friend has a LuxPower hybrid inverter - batteries and solars going directly to it. it's definitely connected in parallel, because if you press the RCD test button it powers down audibly and says 'Grid Disconnected' (presumably getting its power from the batteries to tell us this).. and the house lights stay on and everything else. tracing the tails cables back to the Henly Blocks, it's definitely connected in parallel. - but it does feed the house.

from what i've read that lux is a 'grid tie' ac coupled inverter?? would you agree. so is the multiplus a different class of device? is it because the multiplus creates a Micro Grid when the grid goes offline? keeping other pv ac solar inverters running?

thanks @Rob Duthie - really good presentation. lots of considerations for my design.

i'm thinking i'm going to have a multiplus in series with the house load. and then have a pv dc solar with MPPT, into the batteries distribution bar. which sounds really simple now, but it takes a lot for an amateur to get to that final design, eliminating unnecessary things. i may have micro managed this too much, but it's been interesting to learn about a new technology. haha.

i'll post my final wiring diagram, for others to read, when i've drawn it up. it might help someone some day.