I am looking through manuals and multiple web forums and I think I have found a solution that will work but would like a little clarity.
I am in the US and have good grid power.
I would like to install some solar panels to offset power costs and I can net meter here so sending power back to the grid is allowed.
Due to trees, the location that makes the most sense for solar panels by an outbuilding about 30 yards from the home’s main service panel.
Is it possible to install a multiplus-ii (specifically the multiplus-ii 48/3000/35-50 which is UL1741 listed which I think matters in the US) in the outbuilding and connect a battery and solar panels via a Victron MPPT solar charge controller to the multiplus via its battery terminals and connect the homes main service panel via a single pole breaker to the multiplus on its AC in terminal allowing the multiplus/solar to send power back to the house for either use or to the grid under net metering agreement?
Can you let me know if the above would work and is this method of installation would:
allow for reducing power company bill since solar generated power would either be used in the home minimizing need for grid power or by sending power to the grid earning credits,
be safe because if there were an outage the multiplus would sense power loss on the AC in connection and immediately stop sending power out its AC in connection back to the house and therefore not backfeed the grid,
be effective even if only connected to the main service panel on a single pole breaker when the panel has split phase 240/120 in it.
It is pretty easy. You should look at the 48/5000 model it’s much better and more readily available and not much more expensive. Instead of using MPPT you could put an AC grid-tied inverter on the shed and put the multiplus in the house and have some backup power.
If you want to do net metering you will also need a GX device or RPI with Venus OS and cables to suit. Once it is setup you can install the ESS assistant and then configure it.
I was looking at the 48/5000 actually but it was listed as pending UL1741 so figured I’d play it safe since I think the power company will require that and the 48/3000 is UL listed. If the 48/5000 is approved I’ll use it.
If I’m trying to make the install as low impact as possible and require the least involvement, can the multiplus go in the shed and act as the grid-tied inverter?
I forgot to mention, there’s an existing line good for 30amps already running from the house main panel to the shed and I’d like to use it and not have to run anything else.
I figured if it gives me some extra solar on site I’m happy for now even without backup ability.
Edit to add: I guess what I’m trying to do is this - see attached image.
I took the screenshot from the Victron ESS webinar.
I am hoping to do what he described here without the PV on the AC out or the meter attached to the grid connection. Also I would swap the color control with a cerbo GX.
Since it is feedback only (no loads on the output) is is fairly simple.
You can add a meter to the grid input and set up ESS with the feedback set up. With the meter you will know what is being supplied to the house and the excess being sent back to grid.
Summary
graph TD;
subgraph House ["House"]
GridInput["Grid Input"] <--> Meter["Meter"];
Meter <--> Loads["House Loads"];
end
subgraph Garage ["Garage"]
Loads <--> Inverter["Multiplus"];
Inverter <-->|Charges / Discharges| Battery["Battery"];
MPPT["MPPT Charge Controller"] -->|Charges| Battery;
end
SolarPanels["Solar Panels"] --> MPPT;
The revision was helpful for visualizing it. Thanks!
I also didn’t add the meter in. That you for mentioning that.
I think it’s okay, but I was unsure since I saw somewhere online someone said it couldn’t be done because it would have to put power on both buses in the main panel in the house to keep it balanced.
I don’t believe that to be the case since 120v loads only use power off one bus anyway so it isn’t balanced in that regard.
100% you will need a grid meter. I can show you my setup but my batteries are completely flat and not setting the grid to 0 atm it’s been raining for days. I have a shelly 3em to monitor the grid. I have 2 phases and net metering so all I need to do is set the ESS to the sum of all phases and I can charge and discharge based on what is going on. I also have AC grid-tied PV on both phases. The Shelly 3em needs some configuration to get the data but it is so simple and you can use wifi to the GX device with minimal cost and cables.
There is some energy left in my 24V system I will run it down to 25% just incase we lose power. There is major flooding ATM in my area. The inverter is on L2, L1 has the airconditioers and a 5000W grid tie inverter currenlty doing 300-400W setting the gird to just below 0 ATM. The 24V is exporting trying to maintain a -100 grid setpoint and is servicing all the loads on L2 with AC in. It is pretty good to watch. I dont seem to have any issues with the 2 phases getting out of balance because L2 will only push back the grid to -100 or the airconditioner load which is about 2400W max so L2 at night will be -2500 and L1 will be +2400 for example.
I am in Australia but 240V 120V will not matter. The 24V is connected to the consumer unit coming off the 48/5000 multi then it goes into an anti islanding device and then to a 32AMP RCD in the switchboard on L2. I dont know what regulations you need but it was extremely difficult here to get permission and someone to do the work because your average sparky might not know. If you want to go down the super cheap and easy route of using the Shelly 3em it should be rated to 120V as well.
Just curious about the phasing since we have 240v to the property but it splits and we mostly work with 120 and I heard someone say (not sure if it was accurate though) that I couldn’t feed 120v from the inverter into my panel. Not sure if it’d be the same for you since my understanding is you only have 240v.
Totally makes sense. I was always under the impression you only had 240v. I just looked up a chart of voltage and phase by country and was surprised by a fair bit of what I found.
I did see in manuals and guides that multiple multiplus’s can be used in parallel and for split phase or three phase if you have multiple, but I think I’ve gotten to the point where I’m comfortable agreeing with you.
Thank you so much for sharing and educating me.
What balancing you need will depend on your supplier’s requirements. Technically, you can just feed in on a single phase up until the involved fuses blow, but whether that is permissible is another question.
E.g. in Austria, the limit is 16A per phase while in Germany (which has a very similiar energy system) it is 20A.
