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john-smith avatar image
john-smith asked

MultiPlus-II 2x 120V - Feed grid and use as ups.

1. Can this model feed solar energy back to the grid in the USA?

2. Assuming I already have Victron mppt controller and a 48v battery, do I need a separate grid tie inverter (for example Solaredge) to use this model with the grid?

3. Can this be wired up to the main breaker box? The following data seems to imply that it’s connected to a panel with major appliances. If my “critical loads” are just the 120v outlets, then I should not need a separate breaker box, correct?
The MultiPlus switches to inverter operation when no AC source is available. The inverter output is also 120V single phase. In inverter mode, the MultiPlus-II 2x120V internally connects both lines L1 and L2 together to provide 120VAC to loads on either output. Therefore, in all connection circumstances, both sides of a distribution panel will be supplied with 120V. However, 240VAC is only available when the MultiPlus is supplied by a split phase 120/240VAC source. This prevents heavy loads such as water heaters or 240V air conditioners from discharging the battery.

4. what are the advantages of ac coupling this model with a pv inverter like the solaredge vs using this model by itself?

5. will this model allow the Victron controller to provide solar power and charge batteries during an outage?

6. Are there any victron installers in the Dallas Texas area?


edit

If this can supply power to the grid, is it limited to 3,000 VA of power going back to the grid? let’s say I have 4,500 watts of solar panels, how much of that can be sent to the grid?

Multiplus-II
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1 Answer
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shaneyake answered ·

1. As far as I know it is NOT UL listed, only the Multiplus 12/3000/120 - 50 120V and 24/3000/70 - 50 120V is. If this isn't a problem for you then Yes the Multiplus-II 2x 120V can feed in.

2. No, the Multiplus-II is a hybrid inverter so it can grid-tie and take the power from the MPPT and put in on the grid connection, running your loads or feeding back to the grid.

3. You will probably want 2 panels, even if the Main panel is small. Main Panel fed by grid, Critical loads panel fed by inverter. You might add 240V appliances later, like hot water heater or AC and it would be best for those to be before the inverter.

4. SolarEdge or Enphase micro inverters do really well with shading or uniform panel install as they optimize the power from every panel. Helps with shading or if panels at diffrent angles. They are also more efficient at converting PV to AC. This can be huge amount on big systems, I personally like to do 50/50 as the MPPTs are more efficient at charging the batteries. Not possible on 120V system.

5. Correct, Victron MPPT and inverter will use PV power to run loads and anything extra will charge batteries. It is also possible to charge batteries via inverter if there is an outage with AC coupled PV.

6. I don't know.

7. The inverter can only make 3kva so if you have 4.5kw of PV it will only convert 3kva worth of power from DC to AC. MPPT will throttle array down once batteries are full. This power when then be used to run your loads and then anything that is left would be pushed back to the grid if your inverter is configured to do so.

My advice would be not to use a Multiplus-II 2x 120V. I would rather use a Multiplus-II 48/5000 240V with an auto transformer. This way you always have split phase and are able to push power back to the utility on both phases, it also simplifies things as you do Main panel -> Multi -> Autotransformer -> Sub panel and the sub panel is like any other normal sub panel, you have 240/120 available to run any appliance you want. You can then also add more 48/5000 in parallel if you need more power later for both Export but also running loads when there is an outage. You can also then run a 240V solaredge or Enphase inverters on the output of the Multiplus as both of these only come in 240V versions.

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john-smith avatar image john-smith commented ·
Thanks for the detailed response. I will probably just go with Solaredge for the grid tie. Then I’ll either have some extra panels for off grid use or I will consider ac coupling.


just curious- if ac coupling, am I limited to the watts the Victron multiplus gives me or will I also have the panels powering the house?

let’s say I have 5kw of panels and a 2.5kw multiplus. Then the grid goes down. During the daytime, will I be able to power the home off panels plus the inverter power?

I hope I can find an installer who understands ac coupling.

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shaneyake avatar image shaneyake john-smith commented ·
As I noted above, you can't AC couple Solaredge with Multiplus 2x 120V. As AC coupled inverters have to be on the output of the Multiplus.


You also never want a purely AC coupled system as if the batteries go flat you won't be able to reset system without grid. Best is to have some DC coupled and some AC coupled, even if DC coupled is just few panels.


Victron has a 1:1 rule with AC coupling so if you have a 2.5kw multiplus your AC-PV inverters can't be more than 2.5kw. Just something to keep in mind.

The answer is yes, kind of. Lets say you have no grid.
Your AC-PV system is producing 2.5kw and your multiplus is producing 1.5kw because you are running a total of 4kw load. Now a cloud blows over and your panels are shaded. The AC-PV production drops to 0.2kw, the multi is now providing 3.8kw which quickly overloads it and it shuts off.

There are ways to use this capacity, the 240V Multiplus-ii has an AC-OUT2 output, this can be used to run things like hot water heaters and have it automatically turn off if the multi goes into pre-overload. This way when a cloud rolls in the multi will go into pre-overload and turn off your big loads till the cloud is gone and the inverter load is reduced.

Yes, you can run your loads directly off the power from the panels, the battery is used as a buffer, when clouds or shading happen and then at night to run your loads. If there is enough PV power the system will even use that extra to charge the batteries. Doesn't matter if panels are DC or AC coupled.

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