Inverters in parallel - is this possible???

[Anvilsbeme]

The following question relates to a grid tie solar system without battery storage. See attached simplified line diagram if this helps.

Is it possible to connect three 4000 watt inverters (SMA Sunny Boy 4000US) in parallel instead of using one 12kW inverter.

Thanks in advance for your replies. I'll check back in the evenings in case it takes awhile to answer any questions that gets generated.

 

[SolarRat]

AC doesn't work the same as DC. No, I don't think they'd have their phases in sinc...zapp zapp poof...

 

[SolarRat]

But, if the inverters are designed to be parallelled, and some are, it will work.

 

[DThames]

Look for the term "stackable" when shopping. Those of the same model that are stackable, can be put in parallel. They have a way to allow one to be the master and set the base AC waveform and then the others sync to the master.

 

[Anvilsbeme]

Look for the term "stackable" when shopping. Those of the same model that are stackable, can be put in parallel. They have a way to allow one to be the master and set the base AC waveform and then the others sync to the master.

Great to know that terminology. I will look into that. Meanwhile, I have an email into tech support at SMA and hope to get their answer soon!

 

[tictag]

In short, yes.

Grid-tie inverters are designed to be connected in parallel to provide, for example, 3-phase supplies. Be sure that your inverter supports such operation. In my experience, such units have a communications channel to ensure syncronisation of voltage/phase/frequency and display operating parameters etc (e.g. Victron MultiPlus).

 

[Anvilsbeme]

I did receive a short email reply from SMA in which they said the following "Yes, these can be wired in parallel. Each inverter requires its own breaker."

I replied back to them and asked if they have any documentation that can provide more specific info on this scenario. Waiting to hear back....

 

[Jeffery christy]

I did receive a short email reply from SMA in which they said the following "Yes, these can be wired in parallel. Each inverter requires its own breaker."

I replied back to them and asked if they have any documentation that can provide more specific info on this scenario. Waiting to hear back....

Is your box 3phase? I've never seen a 240 box with 3 bars.

 

[Anvilsbeme]

Is your box 3phase? I've never seen a 240 box with 3 bars.

No, everything is single phase.

 

[Anvilsbeme]

Ok, the verdict is in! I got through to a technical support person at SMA who understood my scenario and in whom I feel very comfortable with his explanation.

Using multiple grid-tie inverters is not a problem. As he explained, a grid-tie inverter is designed to sync to the grid; therefore, if I have three grid-tie inverters, all three of them are looking for the frequency of the grid power, and they have no visibility that any other inverter exists.

When it comes down to actually wiring things up, he said it's perfectly normal to take each of the AC outputs (from the inverters) and wire each of them to a breaker (in a dedicated subpanel), where they get combined to one conductor (actually two conductors since its 240v) headed to the main power panel.