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1ph inverter feeding into other 2 phases - done at curb/meter?


rinners
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Hi all, 

Just wondering if there is a way to do this in SA. I've seen a video of NZ/Aus explaining the setup with the Tesla PW2, but not sure if our grid/meters work that way.

The setup:

- 3ph municipal feed with a standard municipal smart meter (I've heard these aren't bi-directional so even dumping excess will just cost me?)

- each phase goes to a cottage or a house with a single phase Goodwe 4.6kW ES inverter on the house phase. There are no 3ph devices on the property, just 60A might trip with ovens/geysers all on simultaneously. It back feeds to non-essentials when on grid and has excess capacity.

- the inverter came with a 3ph smart meter and 3x CTs, which I'm a bit confused about. Initially when I set up the system the 3 CTs were all connected, but it seems that the usage is aggregated and I wan't to get a clear picture on the single phase. It was also evening when I finished and hence no PV and I subsequently disconnected the other 2 CTs the next morning.

 

The question is, if I connect the CTs again while my house (essential and non) is drawing less than the panels produce, will it feed into the other 2 phases or do I need some sort of phase correction device to do so and does such a thing exist and are they available in SA?

 

Here is the explanation of how it works in NZ/Aus:


Also curious if phase imbalance would ever be an issue if not running 3 phase devices
https://sunkalp.com/connecting-a-single-phase-solar-inverter-to-a-three-phase-connection/

Edited by D.J
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  • 2 weeks later...

The question is, if I connect the CTs again while my house (essential and non) is drawing less than the panels produce, will it feed into the other 2 phases or do I need some sort of phase correction device to do so and does such a thing exist and are they available in SA?

On 2021/08/03 at 9:51 AM, D.J said:

The question is, if I connect the CTs again while my house (essential and non) is drawing less than the panels produce, will it feed into the other 2 phases or do I need some sort of phase correction device to do so and does such a thing exist and are they available in SA?

No, you just get your single phase inverter connected to one of the phase of your 3-phase supply, will not imbalance the supply, you will just be limited to whatever the amperage limit is off one of the phases of the supply, usually 60A or 80A for residential I think.

If your house is wired up for 3 phase supply, it is pretty easy for the electrician to just bridge the 3 phases in the house so they all run of a single phase. 

 

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I am not 100% sure about what you are asking.

I think you are asking about your single phase system feeding into the net and drawing that power via the other two phases back into your house ?

Well yes, sort of. If you are setup as SSEG and can feed back you will be credited for the power you feed in on that one phase but charged for the power you draw from the other two phases unless your meter is setup for net metering (it most likely will not). If you happen to have one of those old ferris wheel meters then you are OK (but are feeding in illegally - those meters always do net metering).

If you have a prepaid meter it likely will trip if you feed in any power.

Can you do it after the meter ? Yes you can but you need a somewhat more complex system using for example three Victron multiplus charger/inverters and a battery bank. With these you can shuttle power between the phases via the DC bus all the while maintaining proper phase relationship.

Tying the three phases into one as suggested above is quite possible as long as the now single phase supply is big enough to handle your loads and of course you do not have any appliances that require three phase supply with the phase shift. Basically in most cases this is limited to three phase motors - aircons, lifts, pumps and the like.

 

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On 2021/08/12 at 3:59 PM, Sc00bs said:

No, you just get your single phase inverter connected to one of the phase of your 3-phase supply, will not imbalance the supply, you will just be limited to whatever the amperage limit is off one of the phases of the supply, usually 60A or 80A for residential I think.

If your house is wired up for 3 phase supply, it is pretty easy for the electrician to just bridge the 3 phases in the house so they all run of a single phase. 

I would, but there are 3 ovens and 3 gesyers to consider. It might very well happen that we exceed the 60A in the evenings.
 

On 2021/08/12 at 4:55 PM, The Bulldog said:

I am not 100% sure about what you are asking.

I think you are asking about your single phase system feeding into the net and drawing that power via the other two phases back into your house ?

Well yes, sort of. If you are setup as SSEG and can feed back you will be credited for the power you feed in on that one phase but charged for the power you draw from the other two phases unless your meter is setup for net metering (it most likely will not). If you happen to have one of those old ferris wheel meters then you are OK (but are feeding in illegally - those meters always do net metering).

If you have a prepaid meter it likely will trip if you feed in any power.

Can you do it after the meter ? Yes you can but you need a somewhat more complex system using for example three Victron multiplus charger/inverters and a battery bank. With these you can shuttle power between the phases via the DC bus all the while maintaining proper phase relationship.

Tying the three phases into one as suggested above is quite possible as long as the now single phase supply is big enough to handle your loads and of course you do not have any appliances that require three phase supply with the phase shift. Basically in most cases this is limited to three phase motors - aircons, lifts, pumps and the like.


Thanks. Let me try an re-phase.

Sometimes my panels are producing more than I'm using on the main house single phase. I would like that extra capacity to somehow be fed into the other 2 phases/cottages when that situation arises. 

If you look at the diagram on the black board on cover image for that youtube video you can see that in Aus/NZ the PW (powerwall) will supply only 1 phase and there's a GW (gateway) that comes with that I'm not sure what it does, but presumably at minimum it has a CT. In this example their heavy loads (the kitchen) are on the inverter phase and the rest of the house is on the other 2 phases. The way the inverter supplies the rest of the house is by feeding into the grid on the kitchen phase and then drawing it immediately back in the other 2 phases so I was wondering if that's just how their grid it set up or is it possible to get something that will allow me to do likewise?

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Sunsynk Inverters have essential and non-essential connections on the inverter. 

Power will get fed to the non-essential side when user programable requirements are met, battery SOC etc so you can power the non-essential circuit with excess solar power but won't run it with battery power in the event of power failure

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8 hours ago, Sc00bs said:

Sunsynk Inverters have essential and non-essential connections on the inverter. 

Power will get fed to the non-essential side when user programable requirements are met, battery SOC etc so you can power the non-essential circuit with excess solar power but won't run it with battery power in the event of power failure

As far as I've observed the Goodwe feeds back to non-essentials while the feed grid is present. But there are still times when I could be pushing a little more PV

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As far as I know you can't back feed into the other phases unless you have a 3-phase inverter. I suspect that the easiest would be just to convert your house to all run on one phase (is relatively simple to do as long as you don't have anything that needs 3-phase supply)  and then just back feed to the non-essential items. Just check that you are never going to need more than your 3-phase can supply on 1-phase, usually 60a or 80a.  

 

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