Good Afternoon All

I apologise in advance for the long essay but I find that I'm in need of unbiased information- both to use in my research work and to decide on a solar installation for my home.

We are currently wired for 3-phase and are direct customers with Eskom. We are looking for a hybrid solar solution that has us generating as much of our own power as possible. The main stumbling block at the moment is how best to deal with the 3 phase wiring. A number of solar installers have done an inspection of our DB configuration and I am getting conflicting opinions. 

Opinion A- Install a 3-phase hybrid inverter (This would be the 12KW Deye although I am interested in the 10KW Goodwe as an alternative as we are not a big household).

Opinion  B- Install a single phase hybrid inverter per phase at leisure until all three phases are connected to a solar inverter.

Solar installer pushing Option A discourages Option B by saying that the inverters are not meant to operate in parallel like this (this is my first point of skepticism because the Deye/Sunsynk specifications state they support parallel operation and I have seen multiple three phase solar installations in SA which have been done with an inverter per phase) and that they would be more prone to blowing as the voltage/current rises would be unbalanced between the inverters and because of the lower tolerances built into the single phase inverters. Solar installer pushing Option A also states that the minimum voltage running in a 3-phase house is around 380V with a higher amperage while single phase inverters max out at around 18A and 230-240V. Also presented by solar installer is that with an inverter per phase, one cannot run appliances such as microwave, kettle, geyser, stove etc. because of the higher kw/h usage (this is my second point of skepticism because if the house was single phase and installed with a single phase inverter, these appliances have been slated to be able to run no problem bar the stove as it has a heating element). Also, each inverter would need its own independent battery backup, solar panels etc. so it's like installing three separate solar installations

Solar installer pushing Option B discourages Option A by saying that by installing the single 3-phase inverter, there is no redundancy/backup built into the system. If that inverter blows, then the whole solar system is down (and the inverter is very difficult to get repaired/replaced even with a warranty) whereas if one inverter on the parallel install blows, then the other two inverters are able to continue providing solar supply while the dead one is either repaired or replaced. This also then gives us more options for inverters whereas the 3-phase hybrid inverter market in SA has very few options. It also allows the solar install to grow as budget becomes available or as we see our needs change. There is also the problem of the 3-phase Deye/Sunsynk inverters running hot and noisy- which then requires them to have a fair degree of ventilation to assist that fan in maintaining the cooling of the inverter. This option however will require the DB board to be rewired and split according (but a rewiring may need to happen anyway for other unrelated reasons).

I have a little bit of background in electrical engineering as part of my profession so I see the points that both installers are making but I don't have sufficient knowledge on (a) power engineering and (b) solar specifications to be able to say confidently one way or the other which opinion is the most correct and the one we should go with even with the research I've done and continue to do.

So I come to the court of public option to ask people who may have real world experience- what were your experiences with Option A or B, the pros and cons, and what you would recommend as the best way forward. This information will also inform the direction of some of the research work I am conducting. 

Thank you so much for your assistance in advanced

 

 

Hi, I have exactly the same issue!

I am however, leaning more towards using 3x 5kw single phase inverters purely because of redundancy. (Livoltek all in one Hybrid 5kw systems)

Also we are 3 phase at the moment, but there is nothing stopping the municipality deciding they need the other hot lines for elsewhere on the street. (slim chance but possible) You would then become a single phase house and stuck with a 3 phase inverter.....

Will be interesting to see the response from the people that have done this already.

Cheers

Also another thing to think of, A single 3 phase unit will be able calculate all your power uses and combine them to give you a " This is how much power you have used" Whereas individual inverters will give you results about their particular phase, you would then have to collate the data yourself.

Hi LehloPI,

I'm pretty-much in the same boat as you, as far as your supply is concerned.

Here are some random thoughts on the subject. 

I've been told that the 3-phase inverters are physically very large (and expensive) because they have three phase transformers in them.  Also, if 1 phase goes down, (as happens to us quite often) then the utility is seen as completely offline, so you're on solar only.  The final note is that you have anything in your house that requires 3 phase power(borehole pump maybe), then you have no option but to go three phase.

As far as running 3 separate inverters, I cannot see how they would interfere with each other as each phase should be completely separate.  Each inverter would not even know that there are others there.  Note that a broken neutral wire at the street will more-than-likely cook one or more of your inverters, they don't like 380V.  Ask me how I know.  I assume that a 3 phase unit would not notice.  So I share your points of skepticism.  I have a friend who is running a 5 times hybrid-inverter setup on a single battery bank, so I believe that the chargers can cooperate with each-other just fine.

 

 

So far the solutions seems to be how to retain the 3ph system. 

If 3ph is not essential I will convert to 1ph. It makes it easier. If a 8kW Deye/Sunk cannot cut your load then a 2nd one to be investigated 

If a borehole is used and it is only for self consumption water I will convert to 1ph to run on PV only during the day. 

Use the full 10kW of panels per 8kW Deye/Sunsynk. 

The essential information is what is the peak power requirement as well as the overall consumption per months. 

This is a good starting point. The 2nd will be can you or prepared to schedule loads for using the best out of PV when full sun days are on offer. 

I just want to add 18A @230V is not the limit for 1ph. A 8kW Deye/Sunsynk can provide 34A fro backup plus more from PV to the non backup essential side. 

Lastly get advice from one of our installers with experience of PV systems. 

Edited March 26, 20232 yr by Scorp007

I am currently using 6 single phase inverter 2 set for each phase . Besides using multiple household appliances which are 220v single phase,I also use 3 phase appliances like elevator for a year now no problem.i was wondering about the same thing why do we need a 3 phase inverter which is generally more expensive per kw.The only real advantage a three phase inverter have is in high voltage battery setup as  high power model use 600v DC voltage I guess.

The Deye/ Sunsynk 3 phase inverter has an advantage when your loads are not balanced.

With 3 single phase 5kW inverters, your cap is 5kW per phase, even if there is no load on another phase.

With the 12kW 3 phase, your cap is the total amount of power the inverter can provide, so if one phase has no load, that power is available for the remaining 2 phases.

 

1 minute ago, JHB73 said:

The Deye/ Sunsynk 3 phase inverter has an advantage when your loads are not balanced.

With 3 single phase 5kW inverters, your cap is 5kW per phase, even if there is no load on another phase.

With the 12kW 3 phase, your cap is the total amount of power the inverter can provide, so if one phase has no load, that power is available for the remaining 2 phases.

 

Not quite true , without grid available the 3 phase 12kw inverter will trip if one of the phases goes over about 5kw. 

1 hour ago, Nexuss said:

Not quite true , without grid available the 3 phase 12kw inverter will trip if one of the phases goes over about 5kw. 

Good to see we at least get to the right answer. 😀😀😀

I have to say that redundancy is a good thing to have in a 3 machine 3 phase architecture. However, a big however, the programming of such a system is not a straight forward thing to do. So it can be done but under a very controlled eye. The 3 phase initial setup is ok, but generally when a phase is down the other 2 machines will also not support an output because they are programmed as 3 phase with a missing machine or phase the output of the other 2 will be held back. So yes it's possible with 2 machines to power 2 independent phases but this is best done a machine operator who understands the dangers. You can damage an inverter if you don't pay attention to the switch on process. 

What I have seen is that 3 machine installation will cost more in terms of more equipment & more Installation labour & that usually requires an above average installer. The single machine unfortunately is a dead duck if something goes wrong with the incoming feed on one of the phases. Think of this way: if you don't have any 3 phase appliances to run & you install a single 12kW 3 phase machine, you now have a 3 phase appliance & that appliance is the inverter. It will not charge or do anything without true 3 phase power & that's a bit of a show stopper. 

In my books if you can go 1ph conversion then do so. If not Install 3 machines but then be prepared for the costs in labour & hardware. The last resort is a single unit. 

One more unexplored idea. Run a backup phase of Essentials. 2 other phases have stuff you can live without. Hey not everyone's idea of convenience but can save you a lot of money if the circuits are well prepared in terms of splitting. But once again quote a bit of extra electrical work for the sparky. This a case in point of pics below. 3 phase system but only single phase backup. 

Can one create a 3 machine 3 phase architecture with different size machines e.g. 2 x 8kw Sunsync's and 1 x 5kw  Sunsynk?

I would like to start with 1 machine and build up to the 3 machines over time.

@FarmerRic Before you even think of doing that, I think the first questions should be:

Do you need a 3-phase power supply i.e. you have 3-phase devices that need to be powered or is it that you currently have a 3-phase power supply?

If you don't have any 3-phase devices (and even if you do, there are options) and you are drawing less than 62A from Eskom, then my suggestion would be to just convert your DB board to single phase (is very easy to do) and it will make your life much easier as you don't have to worry about balancing phases etc. 

Get a 16kw Deye or Sunsynk and problem sorted 🙂  

 

The Deye/ Sunsynk 3 phase inverter has an advantage when your loads are not balanced.

With 3 single phase 5kW inverters, your cap is 5kW per phase, even if there is no load on another phase.

With the 12kW 3 phase, your cap is the total amount of power the inverter can provide, so if one phase has no load, that power is available for the remaining 2 phases.

 

Maximum total load is 12kw (sum off all three phases)

Maximum load on a single phase is 6kw

The inverter also needs to have all three phases being supplied by Eskom, if one phase is down for whatever reason it is unable to sync to the grid and pull power. 

@Sc00bs I have a 3-phase bore hole and two other 3-phase machines so 3-phase is a must for the final solution. I have a walk in fridge (heat pump and blower) on Phase1 which has a high startup load, as well as 2 x heat pumps for underfloor heating on Phase2 (same problem), and then most of the essential household requirements on Phase3.

The problem with a single 3-phase inverter as I understand it is when the underfloor heating if off in summer, I am not pulling any power from Phase2, intermittent power from the walk in fridge when it runs the heat pump on Phase1, and most of the time a reasonable load on Phase3 for household consumption. I have been told that there is a maximum differential that a 3-phase machine can handle between the loads on each of the phases, if so what is that %?

Coming back to my original question can one connect 3 single phase machines of different sizes together to create a 3-phase architecture? Thanks

 

 

@Sc00bsI have been told that there is a maximum differential that a 3-phase machine can handle between the loads on each of the phases, if so what is that %?

Coming back to my original question can one connect 3 single phase machines of different sizes together to create a 3-phase architecture? Thanks

 

Just a part answer. It seems like you can use up to 50% on 1 phase when nooad on the other. Never saw anything that gives the exact % for each phase if all are used but out of balance. 

With one phase at 6 kW you are at the 50% limit already. 

Using 3x single phase units they must be the same size and same firmware version. 

Thanks @Scorp007, so I assume then if I have a 3-phase 12kW machine and am drawing nothing on Phase 1, I can draw up to 6kW on Phase 2 and Phase 3 (total 12kW) at the same time, or for example max 6kW on say Phase 2 and less than 6kW on Phase 3 at the same time (total < 12kW).

 

Thanks @Scorp007, so I assume then if I have a 3-phase 12kW machine and am drawing nothing on Phase 1, I can draw up to 6kW on Phase 2 and Phase 3 (total 12kW) at the same time, or for example max 6kW on say Phase 2 and less than 6kW on Phase 3 at the same time (total < 12kW).

No i don't know how much if you use 2 phases. If only 1 phase then I belief you can go to 6kW.

 

The problem with a single 3-phase inverter as I understand it is when the underfloor heating if off in summer, I am not pulling any power from Phase2, intermittent power from the walk in fridge when it runs the heat pump on Phase1, and most of the time a reasonable load on Phase3 for household consumption. I have been told that there is a maximum differential that a 3-phase machine can handle between the loads on each of the phases, if so what is that %?

Coming back to my original question can one connect 3 single phase machines of different sizes together to create a 3-phase architecture? Thanks

 

So my understanding on the 12KW 3-phase loads is 

• Max power you can pull when off-grid is 12kw
• Max power per phase you can pull is 6kw (total still needs to be under 12kw) 

On the subject of linking single phase inverters together to provide 3-phase, my understanding is that the phases do not need to be balanced and to have an equal number of inverters on it. 

So you if you have 4 inverters, you could have 2 x 5kw inverters and one phase and 1 x 5kw on the other 2 phases for example. 

I am not sure if you can mix the 3-phase and single phases inverters or inverters with different sizes e.g. 5, 8 & 16kw 

I would suggest that you confirm everything in writing with Sunsynk/DEYE as all that I have said is based on what I remember having read somewhere at some stage, I have been looking for a reference for you. 🙂 

Thanks for the additional info @Sc00bs If you find that reference I would appreciate it.

On 2023/03/22 at 5:31 PM, LehloPI said:

Good Afternoon All

I apologise in advance for the long essay but I find that I'm in need of unbiased information- both to use in my research work and to decide on a solar installation for my home.

We are currently wired for 3-phase and are direct customers with Eskom. We are looking for a hybrid solar solution that has us generating as much of our own power as possible. The main stumbling block at the moment is how best to deal with the 3 phase wiring. A number of solar installers have done an inspection of our DB configuration and I am getting conflicting opinions. 

Opinion A- Install a 3-phase hybrid inverter (This would be the 12KW Deye although I am interested in the 10KW Goodwe as an alternative as we are not a big household).

Opinion  B- Install a single phase hybrid inverter per phase at leisure until all three phases are connected to a solar inverter.

Solar installer pushing Option A discourages Option B by saying that the inverters are not meant to operate in parallel like this (this is my first point of skepticism because the Deye/Sunsynk specifications state they support parallel operation and I have seen multiple three phase solar installations in SA which have been done with an inverter per phase) and that they would be more prone to blowing as the voltage/current rises would be unbalanced between the inverters and because of the lower tolerances built into the single phase inverters. Solar installer pushing Option A also states that the minimum voltage running in a 3-phase house is around 380V with a higher amperage while single phase inverters max out at around 18A and 230-240V. Also presented by solar installer is that with an inverter per phase, one cannot run appliances such as microwave, kettle, geyser, stove etc. because of the higher kw/h usage (this is my second point of skepticism because if the house was single phase and installed with a single phase inverter, these appliances have been slated to be able to run no problem bar the stove as it has a heating element). Also, each inverter would need its own independent battery backup, solar panels etc. so it's like installing three separate solar installations

Solar installer pushing Option B discourages Option A by saying that by installing the single 3-phase inverter, there is no redundancy/backup built into the system. If that inverter blows, then the whole solar system is down (and the inverter is very difficult to get repaired/replaced even with a warranty) whereas if one inverter on the parallel install blows, then the other two inverters are able to continue providing solar supply while the dead one is either repaired or replaced. This also then gives us more options for inverters whereas the 3-phase hybrid inverter market in SA has very few options. It also allows the solar install to grow as budget becomes available or as we see our needs change. There is also the problem of the 3-phase Deye/Sunsynk inverters running hot and noisy- which then requires them to have a fair degree of ventilation to assist that fan in maintaining the cooling of the inverter. This option however will require the DB board to be rewired and split according (but a rewiring may need to happen anyway for other unrelated reasons).

I have a little bit of background in electrical engineering as part of my profession so I see the points that both installers are making but I don't have sufficient knowledge on (a) power engineering and (b) solar specifications to be able to say confidently one way or the other which opinion is the most correct and the one we should go with even with the research I've done and continue to do.

So I come to the court of public option to ask people who may have real world experience- what were your experiences with Option A or B, the pros and cons, and what you would recommend as the best way forward. This information will also inform the direction of some of the research work I am conducting. 

Thank you so much for your assistance in advanced

 

 

lehlo

i went thru same issues - took a year to wait for right set up. go for a big 3phase unit. they can go unbalanced - eg a 12 can give you 6 in one phase and say 3 and 3 in others.

 

i went for a larger 20kw one- can at least get 10 on 1 phase then- differnet parts of house runs at different times..

 

the singles will limit you to that specific wattage.

one thing that is more important though is the strings balance- into mppts!

this is the most important yo get the panels to match- hard lessons here. (if uou have more than 2 roof sections/or roof arrays) - make sure you have enough mppts if you roof is complicated!

 

i had to oversize my panels and add optimisers to get panels all onto 2 strings- was inpossible to balance into 4 strings