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Hi all, 

I recently had my installation done. After lots of researching and many questions I settled on 4 x 2.4kWh US2000’s with vertical cabinets, 12 x JA solar 410w mono’s & a 5kW Deye hybrid. 
 

Off the bat I must say I’m incredibly pleased. Eskom reliability is no longer a concern and as all plugs and lights are now on my essential DB I don’t have to worry about damage to electronics etc. 

Batteries do a perfect handover to PV each morning at around 40 - 50% charge and are full again on surplus PV by around 11h45  

I shopped around and used solar advice for hardware and a recommended installer. All in saved me a packet vs turn-key quotes I had received. Install is incredibly neat and both solar advice and the installers were very professional and helpful etc. 

At present my concerns are:

1. I generate around 20 - 24kW per day (theoretical) and am only using around 14kW  Rest is going to waste which means no ROI for that. 
2. I have 3 phase and have serious load imbalance now having done PV for just the one phase and having moved all plugs and lights + pool pump to said phase (2 x geysers + oven left for the other two phases) 

My proposed solution:

1. Move pool pump to second phase. 
2. Install a 2nd Deye 5kW inverter in Parallel. 
3. put one geyser on a phase selector switch (in winter it will be on this phase to balance load but also use excess PV and in summer heat pump for the pool will run so I’ll move geyser to 3rd phase purely on grid) 

With timers I am able to plan my geysers and pool pump / heat pump draws. None of these will be on battery back-up. 
 

My questions:

1. Can one do a split phase parallel with just two phases? 3rd remains fully grid supplied? 
2. what does it actually mean to parallel? Do you share the PV array (thus better utilizing your generated PV and maintaining your peak PV array generation capacity which is really critical for running a heat pump or geyser and making full use of PV)? Do you share the battery bank (even though I don’t need to)? Do you also increase potential kW output even though on separate phases (5kW to 10kW maximum draw at any point)? 
 

Thanks, 

Michael

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2 hours ago, iMercury said:

1. Can one do a split phase parallel with just two phases? 3rd remains fully grid supplied? 

Can't say for this brand of inverter. With Victron inverters, two out of three is quite possible. In some countries (NZ for example) houses sometimes get two phases, so it's similar to the North American split-phase setup except the phase angle is different.

Why not just put a changeover switch that moves the pool pump between L1 and L2 (assuming L1 is the one with backup). Should you absolutely have to run the pool pump from the backup side, you can then just throw the switch...

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Thank you for the reply Plonkster! I think the second phase install and planned load split is still my best bet for a number of reasons but appreciate the knowledge that just 2-phase parallel split is possible depending on inverter. Any info on my second question I.e. what does a split phase parallel actually do / mean? 

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6 hours ago, iMercury said:

Any info on my second question I.e. what does a split phase parallel actually do / mean? 

Not sure. In Victron land, both inverters are just connected to the same batteries. In fact they have to be or it won't work properly. So on the DC side you could say the two inverters go in parallel. On the AC side they do not, for they are out of phase. But there is usually a procedure to set them up to generate power with the phase angle locked together (so that across the phases you get 400V).

So honestly, I'm not sure what that is about, perhaps someone is just confusing the fact that the two units have to work together with "parallel", which is also an example of working together.

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A couple of years back we had a Axpert Clone inverter setup that consisted of 4 x 5KVA inverters 3 of them were configured in 3 pase parallel mode and the 4th was connected to the same battery bank and provided power to a 4th dedicated circuit the 4th inverter had no solar power connected and had no parallel communications connected to the other three that was connected in parallel. The 3 parallel inverters had solar power connected the system is still running today with that setup without complications we just configured the 4th inverter identically to the parallel inverters without the parallel function. It provides the 4th circuit with power and battery backup it also had its own single phase input. So it can be done. However I am quite sure that the Axpert experts can come up with reasons why it should not be done. The point is it still works seamlessly with no serious adverse effects on the gel battery bank we configured it that solar power serves the loads in the daytime and battery is last priority so they only work during loadshedding. However I don't  know if this will work with Solis Luxpower Goodwe and Sunsynk.

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Hi Steve, 

thanks for the reply! So if I understand you correctly a parallel 3 phase system (3 x single phase inverter capable of parallel 3 phase) will share whatever PV strings are providing power and likewise the battery bank (for anything on the battery back-up circuit). 
 

how does the PV get distributed across the three phases? 

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21 hours ago, iMercury said:

how does the PV get distributed across the three phases? 

Through the shared battery. Each inverter uses whatever battery power it needs, and each inverter provides as much power as it can to the battery, if it can accept the power. So the inverter with most of the loads might be a different one to the one that has most of the available PV power, but the power flows from whichever PV to whichever load.

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Thanks Coulomb, I thought that might be the link and presumably this will require the batteries to work harder in shifting power to where it’s needed most (charge / discharge more often or even continuously) thereby reducing the lifespan of them? 
 

Are Pylontech batteries then able to charge and discharge at the same time (charge from inverter with excess PV & discharge to load with insufficient PV)? 

Still have to work out if split phase parallel on just two of the three phases will work (is inverter clever enough to know there is a third phase and thus provide correct phase angle instead of working as if just two phases in total) 

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6 hours ago, Coulomb said:

Through the shared battery. Each inverter uses whatever battery power it needs, and each inverter provides as much power as it can to the battery, if it can accept the power. So the inverter with most of the loads might be a different one to the one that has most of the available PV power, but the power flows from whichever PV to whichever load.

Thanks thats correct 👍🏻

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4 hours ago, iMercury said:

Thanks Coulomb, I thought that might be the link and presumably this will require the batteries to work harder in shifting power to where it’s needed most (charge / discharge more often or even continuously) thereby reducing the lifespan of them? 
 

Are Pylontech batteries then able to charge and discharge at the same time (charge from inverter with excess PV & discharge to load with insufficient PV)? 

Still have to work out if split phase parallel on just two of the three phases will work (is inverter clever enough to know there is a third phase and thus provide correct phase angle instead of working as if just two phases in total) 

Without getting to technical the MPPT Controllers of the inverters that have solar panels connected will service the loads on the battery bank without adverse effects on the battery bank if the array is large enough or larger than the load the array will keep the batteries charged and service the load on the inverter without solar power connected. Or something like that 😀

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