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What is the benefit / aim of "combining" 2 inverters


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6 minutes ago, Antony said:

combine

Combine in what sense?

I can think of three senses.

1. Put two in parallel. This is done mostly to increase power capability, but also redundancy, and for multi-phase systems.

2. Combine a PV-inverter (aka grid-tied) with a battery inverter. You would do this if you have a stable grid connection and you use most of your power during the day when the sun shines. It is much more efficient to bring the PV in on the AC side then.

3. Combine a smaller and a larger inverter. EG a 5KVA i nverter for some circuits and a 1kva for essentials/lights. You might do this to reduce no-load power draw at night, so you can turn the large one off.

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2 minutes ago, plonkster said:
5 minutes ago, plonkster said:

1. Put two in parallel. This is done mostly to increase power capability

so if I add 2 x 4kW inverters I get 8kW?

 

6 minutes ago, plonkster said:

3. Combine a smaller and a larger inverter. EG a 5KVA i nverter for some circuits and a 1kva for essentials/lights. You might do this to reduce no-load power draw at night, so you can turn the large one off.

Is the aim to "disconnect" the larger inverter at night to avoid it drawing from the batteries?

Do you have a "drawing" of this option, i.e. where do PV go, batteries on smaller inverter?

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9 minutes ago, Antony said:

so if I add 2 x 4kW inverters I get 8kW?

Yes, but only for inverters that support it of course.

10 minutes ago, Antony said:

Is the aim to "disconnect" the larger inverter at night to avoid it drawing from the batteries?

Yes.

10 minutes ago, Antony said:

Do you have a "drawing" of this option, i.e. where do PV go, batteries on smaller inverter?

No drawing. Pictures are on my head. Essentially you connect two inverters to the same battery bank. Doesn't matter where you connect the PV, whatever isn't used by one inverter is sent off to the battery where the other inverter can pick it up. There's some videos on youtube where someone did this with two Voltronics because he didn't like the high quiescent draw of the 5kva unit at night... and then he got upset because the smaller unit wasn't much better :-)

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There are many ways how to sync more inverters together. With on-grid, they do a simple AC coupling. Speaking of off-grid installation, the most common is having a unit that is capable of parallel output using a comm cables. For example Mecer, Axpert, InfiniSolar ... these can do off-grid parallel.

 

 

 

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34 minutes ago, Youda said:

For example Mecer, Axpert, InfiniSolar ... these can do off-grid parallel.

And Victron (off grid and grid tied) ... sorry, that door was just left wide open ... I had to. :-) 

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1 hour ago, GAVIN BÜRGER said:

I take it that it's arranged in a parallel configuration. Also, how are you syncing the outputs together, is there some type of comms cable between the two inverters?

I happened to come across a post relating to a parallel configuration and I wondered why. I may want to do this as describe by @plonkster to separate my daily main load from my nightly essential load. I use most of my grid during the daytime, hence if I could move it to PV, I should be one up on old Eishkom, new "Chingkom"

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1 hour ago, Youda said:

There are many ways how to sync more inverters together. With on-grid, they do a simple AC coupling. Speaking of off-grid installation, the most common is having a unit that is capable of parallel output using a comm cables. For example Mecer, Axpert, InfiniSolar ... these can do off-grid parallel.

 

 

 

Capture.JPG

Please give us an example of AC coupling.

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AC coupling is the way that every solar inverter works (aka grid-tie inverter).

Let's say you have 3 solar inverters. All of them are connected to the grid, so they work in sync with grid and therefore in sync with each other. If there's a load, you are not consuming the ESKOM power, but the power from solar first.

If there's a small or no load, the generated power goes to the grid and you get paid for it.

That's the simplest case of AC coupling. The AC coupling makes sense where you are allowed to sell power back to tje grid.

You can create a more sophisticated scenarios, even with batteries. For example having one grid-tie synced with grid and connected to a non-critical loads. Then, adding a second inverter, ie Victron multiplus with the batteries. Critical loads will be fed from Victron.

Clear?

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14 minutes ago, Youda said:

AC coupling is the way that every solar inverter works (aka grid-tie inverter).

Let's say you have 3 solar inverters. All of them are connected to the grid, so they work in sync with grid and therefore in sync with each other. If there's a load, you are not consuming the ESKOM power, but the power from solar first.

If there's a small or no load, the generated power goes to the grid and you get paid for it.

That's the simplest case of AC coupling. The AC coupling makes sense where you are allowed to sell power back to tje grid.

You can create a more sophisticated scenarios, even with batteries. For example having one grid-tie synced with grid and connected to a non-critical loads. Then, adding a second inverter, ie Victron multiplus with the batteries. Critical loads will be fed from Victron.

Clear?

Thanks

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17 minutes ago, Youda said:

... you get paid for it.
... critical loads ... non-critical loads.

To get paid, there are some fees involved and a very expensive meter ... not as easy as it should be.

Check out the Victron Multigrid / Multiplus II (new model). The have all that built in, non-critical goes off when grid goes down, rest not. And it is grid tied, so you can feed the entire house with the solar power if Chinkom is operational.

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