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Solis 4G Single phase 4.6KW dual mppt


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Hi There 

New on the Forum and in the Solar world. Wanting some advise, some of which may be some silly questions to the boffins ....

I have 2x  Solis 4G Single phase 4.6KW dual mppt grid tied inverters and i want to know if they could be joined in parallel in order to provide 9.2 KW ? I do not see mention of that in the manual, unless i just misread.

If anyone could provide some insight on this, i would be grateful.

Many thanks

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5 hours ago, Jrsmit said:

grid tied inverters

By parallel you mean connect both of them to the grid? Yes, of course you can do that. It will work just fine.

You may run into other limitations though. Make sure any wiring is sized to handle the full power. And depending on where you live you may not be allowed to feed in that much. In Cape Town for example, you need at least a 3-phase installation before you can legally feed in that much (even if you use the power yourself, it is about the pickup when the inverter trips, not about the amount fed in). On single phase 9kW would not be allowed.

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Thanks for the help!

Yes i have 3 phase power. So my plan is as follows: (Please tell me your thoughts)  

I am planning on putting most of my load thirsty stuff onto one phase (the one with the 9.2kw - 2x grid tied inverters in parallel) and then critical stuff onto another phase which would have an off-grid inverter with batteries and then basically nothing on the third phase. My thinking was that it would be better to put all of the load thirsty stuff onto one phase and then have 9.2kw to work with, opposed to 4.6kw on 2 seperate phases. 

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3 hours ago, Jrsmit said:

the one with the 9.2kw - 2x grid tied inverters in parallel

That was sort of my point. Connecting 9kW to any single phase might not be allowed by regulations. Certainly not in Cape Town. We can do 3.5kW per phase, so if you have a three phase connection that allows you to go three times higher. If the inverter itself is a 3-phase unit (ie it feeds 3kW into each phase), then you can use it.

Your best bet in this case would be to put each PV-inverter on a different phase, and then move the loads around in the same manner.

I'm not an electrician (disclaimer), but I do know that for most houses 15kW-20kW is about the limit of what you can put on a single phase. Adding another 9kW (another 50%) to the existing capability seems like  bad idea. It is also better to balance the phases, so leaving purposefully moving things around so that one phase becomes unused is not a good idea. Well... let's say the supplier might not really like that sort of thing... if they even notice.

In a three phase supply, the neutral wire carries the difference between the phases. In a perfectly balanced setup, the neutral cable carries no current. When you unbalance your loads, you increase the current in the neutral conductor, which can result in rather interesting results should you ever lose that neutral. Also, in some installations the neutral cable is of a smaller gauge (because of this), or at least so I've read. All things to take into consideration...

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4 minutes ago, plonkster said:

That was sort of my point. Connecting 9kW to any single phase might not be allowed by regulations. Certainly not in Cape Town. We can do 3.5kW per phase, so if you have a three phase connection that allows you to go three times higher. If the inverter itself is a 3-phase unit (ie it feeds 3kW into each phase), then you can use it.

Your best bet in this case would be to put each PV-inverter on a different phase, and then move the loads around in the same manner.

I'm not an electrician (disclaimer), but I do know that for most houses 15kW-20kW is about the limit of what you can put on a single phase. Adding another 9kW (another 50%) to the existing capability seems like  bad idea. It is also better to balance the phases, so leaving purposefully moving things around so that one phase becomes unused is not a good idea. Well... let's say the supplier might not really like that sort of thing... if they even notice.

In a three phase supply, the neutral wire carries the difference between the phases. In a perfectly balanced setup, the neutral cable carries no current. When you unbalance your loads, you increase the current in the neutral conductor, which can result in rather interesting results should you ever lose that neutral. Also, in some installations the neutral cable is of a smaller gauge (because of this), or at least so I've read. All things to take into consideration...

Many thanks! - you gave me some interesting stuff to consider...

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