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sunshinepower avatar image
sunshinepower asked

Best setup for 2 quatros with 2 positive lines, one neutral line off grid


I have a 2 phase system on property which means I have 2 live wires and one neutral.
For an off grid system set up I was going to have 2 separate systems, an inverter connected to each line and share the neutral with

x2 inverters (Quattro's 10kva 48v)
x2 battery banks
x2 sets of mppts
and separate arrays of solar panels for each system

However I have since learned that there could be a better set up by combining the inverters together in parallel. Single battery bank, one set of mppt's and solar panels for single system.
This would mean I may have to connect the two positive lines together and power both phases as one with the two inverters paralleled as master/slave.
This would allow all the power of both inverters to go to both positive lines and power can be used by either line at different times or at the same time. Maybe this could work, not sure?


Or is it possible to set them up as you would do to parallel the two inverters together as master and slave using the same battery and mppt's and have the neutral common to both inverters but have separate positives where each inverter is connected to a different positive line.. They would be loaded very differently at different times would this be ok? I don't know.

quattro 10kva
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3 Answers
wkirby avatar image
wkirby answered ·

It's going to be difficult to provide good answer without first knowing for sure what those two line conductors are. Are they the same phase (0°) , are they two phase (120° / 240°) or split phase (180°)? If your two line conductors are different phases then you cannot configure the two Quattro's in parallel. You would need to configure them as two phase or split phase depending upon how the phases of the two incoming lines. An answer about the neutral conductors would follow on from here.
Better to have this information in hand before providing an answer otherwise will will go round and round in circles.

In any case, it's always better to have one system battery bank and all MPPT's feeding the one battery bank as one simple system.

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sunshinepower avatar image sunshinepower commented ·

Thank you wkirby, However Its not grid connected system . Its just the wiring in place that is to be used for an off grid system with 2 inverters as mentioned above. Can I please have help with the above questions, I did say it was off grid system even in the heading.

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wkirby avatar image wkirby ♦♦ sunshinepower commented ·
Sorry, I missed the off-grid part.

So if you have two line conductors to feed circuits downstream and you don't care about the phase relationship between the two then the best thing would be a parallel system.
Configure the two Quattros as a parallel system and wire them to one common distribution board, Take both line and neutral from each, don't share a neutral because the line and neutral current will be the same from each Quattro. The two Quattros will share the load equally.
Then from the distribution board the two line conductors that you have can be taken off from different circuits. Your electrician would offer you the best advice here in order to conform to your local wiring regulations.

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sunshinepower avatar image sunshinepower wkirby ♦♦ commented ·

So I get the paralleling of the inverters but are you saying to connect both positive outputs from the inverters together then the two lines would also be connected together they will be acting as two distribution lines from single two inverter source. I don't understand how the neutral from the inverters are not connected together. I have only one neutral wire for the whole property, how can it not be shared or connected to both inverters? What do I do with neutral? I just dont understand what you are saying here.


Or are you saying to separate the outputs from both inverters therfore positive from each inverter goes to separate lines they will have different loads, but still the neutral will have to be common to both though.


Basically what I need to understand is that when using the 2 inverters in parallel can I have different loading on separate inverters having the positive outputs going to different lines and different loads.
or

Connect both inverter positive outputs together thereby all loads on both lines will be connected to both inverters therefore all loads will draw from both inverters.

and what happens to the neutral

Which ever way the set up is I still only have one neutral line and surly it would have to be connected to both inverters which ever way chosen is best.

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wkirby avatar image wkirby ♦♦ sunshinepower commented ·
Take the line and the neutral from each Quattro and then combine them in a main distribution board. Now the two Quattros are providing a single source of power at that distribution board.

From there you can take power to you existing two line conductors off of two separate circuit breakers.

So now another twist, what is the CSA of your neutral conductor? Is it the same as one of the line conductors? If it is the same then parallel inverters would not be suitable because the neutral current would perhaps be too high, you would have to go with split phase or two phase to keep the average neutral current down. This depends upon you local wiring regulations - ask your electrician about that.
Even in split phase or two phase take line and neutral from each Quattro to combine the neutrals at a distribution board and then separate phases to each of your line conductors going out.

Sorry about the confusion, it is an unusual arrangement I am not there to see it. I have to build a picture in my head. I can tell you how to get from the Quattros to a main distribution board to combine those conductors - always both line and neutral from the Quattros to the board. From that point your electrician needs to offer you the proper advice.

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Kevin Windrem avatar image
Kevin Windrem answered ·

Whether you connect the Quatros in true parallel operation or two/split phase depends on your distribution system and the loads connected to it.

Are there any loads that connect to both hot legs through a dual breaker? If so, I would guess that these loads need double the voltage of loads that connect to one hot and the neutral. If this is the case, then you want to configure the Quatros as a two-phase system, then set the phase relationship, to match what your loads expect, probably 180 degrees. This makes a "split phase" system.

Paralleling Quatros (not multiphase) requires all cables in and out AC and DC to be of matched length. That is the positive battery cables must be equal length to some common point. Same for the battery negative, same for the AC hot and AC neutral connections. Any cable length differences will result in the Quatros not sharing the load equally. If you go this route, you would need a common point for your AC hot legs, then run separate hots from that point to each leg of your distribution panel.

There is a good tutorial on multiple inverter/charger design and setup on Victron Professional. This will answer most of your questions. The account is free.

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sunshinepower avatar image sunshinepower commented ·

Hi Kevin,

There aren't any shared loads on the two phases that I can see. However the loads seem quite shared throughout property through the 2 individual phases.

Paralleling the Quatros is something I was thinking of doing, I was also considering running two separate systems with shared neutral but after help from wkirby I am now looking at 2 phase set up. It seems to be the simplest set up. I have been trying to look at various options to choose something that will work best as I seem to have a bit of an unusual set up that I have to deal with. And its really quite confusing that victron has left the 2 phase set up out of its set ups, I cannot think why they would do this even if it is not that popular, just doesn't make sense. Thanks to wkirby he has shown that it looks quite easy to set up. Initially I was going to have it grid connected but brought with it its own problems, also as far as I am aware victron has lost its certification for the quatros in Victoria at the present time. Thanks for your advice.


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Kevin Windrem avatar image Kevin Windrem sunshinepower commented ·
There are two levels of "certification": the first is the ability to connect inverter/chargers to the grid; the second allows feeding back power to the grid (an Energy Storage System).


Since you appear to be struggling with this, I recommend you consult an electrical contractor familiar with off-grid or ESS systems or at least grid-connected inverter/chargers. There are simply too many opportunities for a DYI design to miss important issues and the consequences could be dangerous.

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sunshinepower avatar image sunshinepower commented ·
Hi Kevin

Thank you for all your help. I am thinking that your suggestion is by far the best set up option for me that I can see at this time with 2 phase set up of 2 Quattros with 180 degree phase shift.

I am finding that the loads on each phase are reasonable distributed throughout on my property, thus enabling a reasonable cancellation of load on the neutral conductor which is very important. The final positioning of solar system at this time is 220 meters from house loads and cross section area of a single conductor is 23.31 mm squared, and there are 3 separate conductors. So its important to keep the neutral as unloaded as possible.

May I ask that when 2 Quattros are set in 2 phase system with 180 degree phase shift. I am assuming that the transformers of the two quattros will be acting in a sense like a single transformer with a center tap, that center tap is the neutrals and the other end of each transformers from each quattro are the line 1 and line 2. Would this be correct?


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Kevin Windrem avatar image Kevin Windrem sunshinepower commented ·
The transformers and the two Quatros will be completely independent. While in concept it looks like one center tapped transformer, there is no magnetic coupling between the two like there would be in a single transformer with a center tapped secondary.
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Paul B avatar image
Paul B answered ·

lets get some clarity

1. the site is 220volt 50hz

2. there is a generator involved somewhere

3. really you are calling this two separate systems for no electrical reason except that they go off to different areas.

If this is the case

1. then make ONE battery bank

2. set the two Quattros up as a Paralleled system this will then give you 20VA in TOTAL available to both circuits. ( this way you share the load and any one circuit can use the FULL systems output)

3. the Quattro outputs are then combined into one main feed in and you connect this to the ONE main incoming breaker in your switch board - then from there you run the different circuits off to as many locations as you like through separate breakers in preference.

4. up to you but a RCD breaker or equivalent breaker should be installed at least at the remoter switch boards.


I maybe wrong with the above but from everyone's reply's and your reply's I think this is what you are after - SO just KEEP IT SIMPLE.


Again you should get electrical advise from a qualified electrician. killing yourself or someone else down the track is not a good option.


If the above is wrong then a diagram of what you are proposing would be helpfull




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sunshinepower avatar image sunshinepower commented ·

Thanks Paul,


This is off grid.

No generator.

1 battery bank

2 Quattros

What you are saying may be the way to go but was concerned about neutral having to carry the power of both lines at the same time, Phase shifting can help with this.

The main loads are at the end of 70meter (x3 cables, L1,L2,neutral) cable from where the solar set up is but the cable is very large because of the distance, I haven't measured the area however around 8 or 9mm core diameter so maybe its good enough anyway.


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kwame avatar image kwame commented ·
I found this very interesting and an area that really lack clear cut illustrations. Would you be kind to come up with an illustration diagram as how to go about making a proper connection for 240v output for 1 phase using 2 off grid inverters in parallel.
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kwame avatar image kwame commented ·
A diagram would be most desirable. I'm also very interested in understanding the process of wiring it correctly.
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Fideri avatar image Fideri kwame commented ·

@Kwame Have you looked at this?

https://www.victronenergy.com/upload/documents/3-Phase-Quattro-system-with-Cerbo-GX-Touch-50-BYD-LVL-Smart-solar-MPPT's.pdf

It's a 3 phase system but relevant to parallel setup. The physical connections are the same.

Fideri

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kwame avatar image kwame Fideri commented ·
That makes so much sense now that I have seen it. Thanks for you pointing me there. Cheers
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