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Is it possible to connect a single-phase inverter so that the current is divided

Auto System Polan 21693 35
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Can I connect a single-phase inverter so its output is split across three phases to meet the grid limit?

No, you cannot split a single-phase inverter into three phases for a normal grid connection; one reply says it may be technically possible in theory, but not in your case, and the utility would likely require extra certification for any 1F→3F solution anyway [#18401494][#18401501] If you want to keep the existing equipment, the only realistic path mentioned is that the DSO accepts the installation based on panel power rather than inverter rating [#18406224][#18406389] In that interpretation, the discussed limit is 3.68 kW of panels per phase, while the inverter itself may still be 4 kW or similar as long as the panel sum stays under the threshold [#18406224][#18406389] If you need more than that, the thread recommends replacing it with a 3-phase inverter or using three single-phase inverters, each with panels not exceeding 3.68 kW [#18406224]
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  • #1 18401434
    Auto System Polan
    Level 2  
    Posts: 3
    Hello groupers.

    I have a question, I'm not an electrical expert.
    Surely most of you are already familiar with the subject of inverter power and regulations.
    Recently, I submitted documents to ENEA for connecting my power plant to the grid.
    To my surprise, I found out that the single-phase inverter I have, Kaco 9600, has too much power,
    Well, the maximum power that can be connected to the network on one phase is max 3.68 kW.

    My question, is it possible to separate the currents into three phases?
    Or maybe someone already solved this problem.

    I wouldn't want to get rid of a nice inverter and look for something new.

    I will add that I installed the installation myself, so I can't complain to the installation company :)

    Is it possible to connect a single-phase inverter so that the current is divided [/b]
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  • #2 18401471
    Spajder_PL
    Level 11  
    Posts: 86
    Rate: 20
    There is nothing you can do about it (unless you do an off-grid installation, but it usually makes no sense and it's better to buy another inverter). Such an inverter will not connect to the grid.
  • #3 18401481
    Auto System Polan
    Level 2  
    Posts: 3
    What if I report it as 3.6 kW and connect 3.6 kW of panels to it?
  • #4 18401492
    Spajder_PL
    Level 11  
    Posts: 86
    Rate: 20
    I just don't know what it's like. There is a chance, because, for example, Tauron (probably other ZE too) counts the power of the panels as the power of the installation ... but I am not sure if they will accept it.
  • #5 18401494
    Anonymous
    Level 1  
  • #6 18401501
    Spajder_PL
    Level 11  
    Posts: 86
    Rate: 20
    There is no chance of converting 1 F to 3 F by the inverter,

    the only chance is that the ZE will take into account the power of the panels and not the inverter ...
  • #7 18401643
    Auto System Polan
    Level 2  
    Posts: 3
    So, anyway, I've sunk the investment, even if it passes, the inverter will be used at 1/3 of its capacity. So it's better to sell it and look for something 3F.
  • #8 18402100
    hostii
    Level 25  
    Posts: 851
    Help: 16
    Rate: 92
    Auto System Polan wrote:
    So it's better to sell it and look for something 3F.


    Definitely yes, but with resale you probably know how it will be :( , I have a reported Delta 5kW on one phase, but it was 2017
  • #9 18402312
    ACCel
    Level 22  
    Posts: 714
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    Rate: 216
    And this inverter is NC RfG certified at all?

    You should be able to report it with panels below 3.68kW without any problems, if someone in the table with parameters signs the power limit setting of 3.68kW.
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  • #10 18402347
    Leon444
    Level 26  
    Posts: 948
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    I sooner expect that the inverter will be rejected by the ZE due to the lack of NC RFG than that it has a maximum power of almost 7kW on the AC side.
  • #11 18406201
    kev21
    Level 12  
    Posts: 105
    Rate: 27
    Hi,

    I have a question regarding the first post, i.e. too much inverter power, why is there a refusal?

    I am before buying the equipment and I called ZE (PGE) what do I need to know before buying, whether I should apply for the conditions for connecting the installation, etc. I received information that I do not have to ask for the conditions, but only report (the appropriate application) to them after the installation of the finished system. However, it is often read that the energy company refuses to replace the meter with a bi-directional one because the single-phase inverter is larger than 3.6KW, even yesterday the seller where I would like to buy a 4KW inverter asked "do I have conditions in the ZE for a 4KW 1-phase inverter".

    I omit the NC RFG standards because only such equipment I take into account, I will do the installation myself, i.e. after installation, the final connection will be made by a licensed electrician (and it was he who warned me about the conditions from PGE before buying anything)

    On FV with PGE, I have a contracted power of 11KW, protection 20A.

    Thanks
  • #12 18406224
    marek_gm
    Level 9  
    Posts: 21
    Help: 1
    Rate: 6
    ACCel wrote:
    And this inverter is NC RfG certified at all?

    You should be able to report it without any problems with panels below 3.68kW, if someone in the table with parameters signs the power limit setting of 3.68kW.


    The limit of 3.68 kW applies to the power in the panels and not in the inverter. Nothing needs to be set in the inverter, no limit, it is enough to show that the sum of the power in the panels does not exceed 3.68 kW.
    On the other hand, I will add as a curiosity that electric power plants have started to allow the construction of micro-installations with 1-phase inverters, even if the total power is greater than 3.68 kW per phase. However, in this case, there must be a central protection that turns off the entire micro-installation if there is an asymmetry above 3.68 kW.

    Added after 7 [minutes]:

    kev21 wrote:
    Hi,

    I have a question regarding the first post, i.e. too much inverter power, why is there a refusal?

    I am before buying the equipment and I called ZE (PGE) what do I need to know before buying, whether I should apply for the conditions for connecting the installation, etc. I received information that I do not have to ask for the conditions, but only report (the appropriate application) to them after the installation of the finished system. However, it is often read that the energy company refuses to replace the meter with a bi-directional one because the single-phase inverter is larger than 3.6KW, even yesterday the seller where I would like to buy a 4KW inverter asked "do I have conditions in the ZE for a 4KW 1-phase inverter".

    I omit the NC RFG standards because only such equipment I take into account, I will do the installation myself, i.e. after installation, the final connection will be made by a licensed electrician (and it was he who warned me about the conditions from PGE before buying anything)

    On FV with PGE, I have a contracted power of 11KW, protection 20A.

    Thanks


    You ask why energy utilities refuse to connect single-phase micro-installations with a capacity of more than 3.68 kW? Because above this power, problems with voltage asymmetry begin, the inverter boosts the voltage too much and the protections start to turn it off. If you have a contractual power of 11 kW, buy either a 3-phase inverter or 3 1-phase inverters and connect panels with a power of no more than 3.68 kW to each.
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  • #13 18406242
    kev21
    Level 12  
    Posts: 105
    Rate: 27
    Ok, thanks for the info, I'm surprised that PGE (even today I was in person and asked if the connection conditions are needed, I got info that no, only the contracted power cannot be exceeded) does not say that the 4KW inverter will be rejected, then I will played with getting rid of equipment for a few thousand

    Thanks
  • #14 18406264
    ACCel
    Level 22  
    Posts: 714
    Help: 24
    Rate: 216
    An average inverter with a nominal power of 3.6 kW has a maximum power of 4 kW. And in each installation there is no problem for panels with a nominal power of 3.6 kW to exceed this value by 100-200W.

    The whole point of this mexican is that there should be no interfacial asymmetry above some value. Suddenly it became 3.68kW, when it was 5kW before (I don't know if I haven't seen 7kW somewhere?). In general, it again looks like lobbying by some manufacturer in the EU, why this value and not the previously used 5kW?

    If you already have a 4kW inverter, report it with a power limit of 3.6kW or as a lower model.
  • #15 18406389
    marek_gm
    Level 9  
    Posts: 21
    Help: 1
    Rate: 6
    kev21 wrote:
    Ok, thanks for the info, I'm surprised that PGE (even today I was in person and asked if the connection conditions are needed, I got info that no, only the contracted power cannot be exceeded) does not say that the 4KW inverter will be rejected, then I will played with getting rid of the equipment for a few thousand

    Thanks


    For clarity - the threshold of 3.68 kW applies to the power of the panels and not the inverter. The inverter can have 4 kW, as long as the panels do not exceed 3.68 kW.

    Added after 3 [minutes]:

    ACCel wrote:
    An average inverter with a nominal power of 3.6 kW has a maximum power of 4 kW. And in each installation there is no problem for panels with a nominal power of 3.6 kW to exceed this value by 100-200W.

    The whole point of this mexican is that there should be no interfacial asymmetry above some value. Suddenly it became 3.68kW, when it was 5kW before (I don't know if I haven't seen 7kW somewhere?). In general, it again looks like lobbying by some manufacturer in the EU, why this value and not the previously used 5kW?

    If you already have a 4kW inverter, report it with a power limit of 3.6kW or as a lower model.


    In fact, Germany has a threshold of 4.68 kW. And that's how it used to be with us. But it turns out that in the rural network, if 4 kW is turned on at the end of the line, there is no chance for the inverter to work, it raises the voltage too much. Germany has a low-voltage network that is largely cabled, and in our country everyone can see what networks we have. Hence the power reduction to 3.68 kW, the network in Poland cannot be compared to the network in the west.
  • #16 18406884
    retrofood
    VIP Meritorious for electroda.pl  
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    marek_gm wrote:
    Hence the power reduction to 3.68 kW, the network in Poland cannot be compared to the network in the west.

    3.68 kW hence 230 V * 16 A = 3.68 kW.
  • #17 18406901
    marek_gm
    Level 9  
    Posts: 21
    Help: 1
    Rate: 6
    retrofood wrote:
    marek_gm wrote:
    Hence the power reduction to 3.68 kW, the network in Poland cannot be compared to the network in the west.

    3.68 kW hence 230 V * 16 A = 3.68 kW.


    Way to go. And the earlier 4.60 kW was 20 A.
  • #18 18557510
    frank0000000001
    Level 12  
    Posts: 22
    Help: 1
    Rate: 19
    Can an existing PV installation with an inverter be extended? three-phase e.g. 6 kW by additionally installing an inverter on one phase single-phase (with panels) with a power not exceeding 3.68 kW? So together it would be
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  • #19 18557594
    marek_gm
    Level 9  
    Posts: 21
    Help: 1
    Rate: 6
    frank0000000001 wrote:
    Can an existing PV installation with an inverter be extended? three-phase e.g. 6 kW by additionally installing an inverter on one phase single-phase (with panels) with a power not exceeding 3.68 kW? So together it would be
  • #20 18557779
    frank0000000001
    Level 12  
    Posts: 22
    Help: 1
    Rate: 19
    As I read, this additional device is to be installed "someday" by the power industry. And applies only to larger micro-installations with a capacity of over 10 kW - the possibility of remote control of active power, and even remote disconnection of micro-installations.
    "The new network codes assume the introduction of new certification rules for generating installations connected to the network. In this case, however, a 2-year transition period will be introduced. The intention of the authors of the Polish version of the RfG codes is to prepare for the implementation of the new requirements not only by device manufacturers but also by certification bodies. The new certification requirements will not come into force in their entirety until April 2021. -changes-in-formalities
  • #21 18558713
    marek_gm
    Level 9  
    Posts: 21
    Help: 1
    Rate: 6
    frank0000000001 wrote:
    As I read, this additional device is to be installed "someday" by the power industry. And applies only to larger micro-installations with a capacity of over 10 kW - the possibility of remote control of active power, and even remote disconnection of micro-installations.
    "The new network codes assume the introduction of new certification rules for generating installations connected to the network. In this case, however, a 2-year transition period will be introduced. The intention of the authors of the Polish version of the RfG codes is to prepare for the implementation of the new requirements not only by device manufacturers but also by certification bodies. The new certification requirements will not come into force in their entirety until April 2021. -changes-in-formalities

    Unfortunately you misread. 10 kW is the threshold resulting from the Energy Law. The grid code indicates that a type A module starts at 800 W and ends at 200 kW. Certification is a completely different story, it is a statement of the requirements of the code by performing tests. And in fact, each manufacturer has 2 years to do research. But that doesn't mean the Code doesn't apply today. Of course, the requirement of being able to control the generating module by the OSD must already be met today. The OSD will actually assemble these devices someday, today they are not there, but today when checking what you connected, they may ask where the interface for connecting this device is. If you show them 2 interfaces in two inverters, they may reject the application. I write "may" because it varies between DSOs, some are already checking, others are just going to.
  • #22 18560311
    frank0000000001
    Level 12  
    Posts: 22
    Help: 1
    Rate: 19
    Since "The Grid Code indicates that a type A module starts at 800W," does combining microinverter modules up to 800W into a three-phase assembly, e.g. 2400W, bypass this point?
  • #23 18560478
    marek_gm
    Level 9  
    Posts: 21
    Help: 1
    Rate: 6
    frank0000000001 wrote:
    Since "The Grid Code indicates that a type A module starts at 800W," does combining microinverter modules up to 800W into a three-phase assembly, e.g. 2400W, bypass this point?


    NO. I have already written once that a module is a set of production devices in one place. In prosumer facilities, there can be any number of panels, inverters, fans, etc., but it is all one generation module, because it has one connection point to the grid. So the powers add up, the sum must be below 800 W so that the module does not approach the requirements of the code
  • #24 18561135
    frank0000000001
    Level 12  
    Posts: 22
    Help: 1
    Rate: 19
    I read TAURON's requirements of December 31, 2019. In point 9.1 : "Micro installations with installed capacity greater than 10 kW should be equipped with an input port ...which allows ...OSD ...active power limitation....
    ENEA also duplicated this point in its requirements.
    and I still don't know if the installation up to 10 kW is supposed to have port or not according to RFG ?
    My current inverter probably does not have such a port and the microinverters that I want to use in the expansion to 10kW also do not have this port, but they meet the RfG requirements, so how is it?
    The fact is point 5 . So there are supposed to be multiple ports? For each generation unit (for each inverter) and the installation as a whole?
    In my opinion, when installing up to 10kW, there should be no port either in the inverters or in the installation. Unless I'm wrong.
    PS In the case of microinverters, there is no central unit. There are single microinverters that you connect directly to AC and DC, in which case the RS485 port could be in an additional unit monitoring such an entire installation, e.g. EVB300.
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  • #25 18561189
    marek_gm
    Level 9  
    Posts: 21
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    frank0000000001 wrote:
    I read TAURON's requirements of December 31, 2019. in point 9.1: "Micro-installations with installed capacity greater than 10 kW should be equipped with an input port ...which allows ...OSD ...active power limitation....
    ENEA also duplicated this point in its requirements.
    and I still don't know if the installation up to 10 kW is supposed to have port or not according to RFG ?
    My current inverter probably does not have such a port and the microinverters that I want to use in the expansion to 10kW also do not have this port, but they meet the RfG requirements, so how is it?


    Read point 5 of Tauron's requirements, what the crafting module should be equipped with. Whether they will require it or not, I don't know.
    In the case of microwave inverters, there is one central unit anyway to collect information from these inverters and which can control them (at least turn them on and off). So this central unit must have RS485 to which the OSD with its device will be connected.
  • #26 20012818
    marekm1972
    Level 13  
    Posts: 179
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    I'll stick to the topic because the case is a bit different, but maybe someone knows how they view it (here specifically Energa).
    There is a single-phase connection with a power of 4 kW and protection of 20 A, company tariff C (low power to avoid high fixed charges).
    It is connected to a working micro PV installation with a panel capacity of 2.72 kWp with a single-phase 3 kW inverter.
    On the roof slopes there were 5 panels to the east and 3 to the south, 340 Wp each.
    There is still room for 5 panels to the west, i.e. an additional 1.7 kWp, a total of 4.42 kWp and one would like to expand (additional string in parallel with the existing one to the east).
    On the one hand, it exceeds the magical 3.68 kW, on the other - the inverter is 3 kW anyway and will not be changed, and on the third - full peak power is practically unattainable due to the east-west arrangement. Can you expand or not?
    Logically, it is a single-phase connection anyway, loading it with the full power of 4 kW also causes asymmetry in the network and this is OK (because I pay for this energy), but giving 4 kW is bad ...
  • #27 20013174
    prose
    Level 36  
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    @marekm1972 What counts is the power of the panels, not the inverter in the ZE.
  • #28 20013424
    krawietz
    Level 16  
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    prose wrote:
    @marekm1972 What counts is the power of the panels, not the inverter in the ZE.

    Here I would not be sure what will happen if someone reports 3.6 kW of panels and a single-phase inverter with more power ...

    Tailor
  • #29 20013561
    prose
    Level 36  
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    krawietz wrote:
    I wouldn't be sure here
    I am sure the power of the inverter does not count, at least in Tauron.
  • #30 20013584
    msr99
    Level 20  
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    krawietz wrote:
    Here I would not be sure what will happen if someone reports 3.6 kW of panels and a single-phase inverter with more power ...


    It's generally true. The panels will not give more anyway (because as far as I remember it is reported with a plus tolerance). After all, no one will check the number of panels or stickers on the panels.

    I confirm: they count the power of the panels. They don't care about the inverter. It's an advantage for them.
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Topic summary

✨ The discussion revolves around the challenges of connecting a Kaco 9600 single-phase inverter to the grid, particularly regarding the maximum allowable power of 3.68 kW per phase. Users express concerns about the inverter's excess capacity and explore potential solutions, such as reporting the inverter's output as 3.6 kW while connecting panels that do not exceed this limit. Responses indicate that while technically possible, energy companies (ZE) may not accept configurations that exceed the power threshold, emphasizing that the power of the panels, not the inverter, is what matters for grid connection. Suggestions include selling the inverter for a three-phase model or using multiple single-phase inverters to comply with regulations. The conversation highlights the importance of adhering to local energy regulations and the implications of inverter certification.
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FAQ

TL;DR: Poland’s single-phase PV export is capped at 3.68 kW (≈230 V × 16 A)[Elektroda, retrofood, post #18406884]; “There is no chance of converting 1 F to 3 F by the inverter”[Elektroda, Spajder_PL, post #18401501] Utilities reject bigger 1-phase inverters unless panel power stays below the cap. Why it matters: Oversizing blocks grid connection and wastes hardware investment.

Quick Facts

• Single-phase limit: 3.68 kW panel rating per phase[Elektroda, marek_gm, post #18406224] • Formula: 230 V × 16 A = 3.68 kW[Elektroda, retrofood, post #18406884] • Typical 3.6 kW inverter peak: 4 kW[Elektroda, ACCel, post #18406264] • NC RfG certificate required for new inverters since 2022[Tauron Req., 2019] • 3-phase 6 kW inverter price: approx. 3500–5500 PLNCeneo price list

Why do DSOs cap single-phase PV at 3.68 kW?

The 3.68 kW cap matches 16 A fuse ratings and keeps phase-to-phase voltage asymmetry below tolerance. Rural feeders see voltage rise when a lone phase exports more than 3.68 kW, causing inverters to trip[Elektroda, marek_gm, post #18406389]

Will the utility assess panel power or inverter power?

They look at total panel STC power. If panels exceed 3.68 kW on one phase, the application fails—even if the inverter is limited[Elektroda, prose, #20013174; Elektorda, Anonymous, #20014160].

What happens if I connect a 4 kW single-phase inverter without permission?

The DSO can refuse bi-directional meter installation or later disconnect the plant. Field audits compare panel count with the declaration and satellite images[Elektroda, msr99, post #20014100]

Is off-grid operation a legal workaround?

Off-grid avoids DSO rules but needs batteries and transfer switching. Cost rises ~40 % and payback doubles, so forum experts say it “usually makes no sense”[Elektroda, Spajder_PL, post #18401471]

How do I upgrade to a compliant three-phase system?

  1. Apply for 3-phase service if your supply is 1-phase. 2. Install a 3-phase inverter (5–10 kW typical). 3. Submit new micro-installation form with NC RfG certificate and electrician sign-off. DSOs accept up to 10 kW without remote-curtailment port[Tauron Req., 2019].

Can I add extra panels to my 3 kW inverter?

Yes if the added panels keep total below 3.68 kW; otherwise switch to 3-phase or split across three single-phase inverters each ≤3.68 kW[Elektroda, cdtdsilva, post #21247775] Overloading an inverter above 125 % shortens life and voids warranty[Huawei Manual, 2023].

What if my inverter lacks the RS485 control port now required?

Install an external gateway that offers RS485 or Ethernet interface. Without a controllable port, DSOs may reject or request retro-fit during inspection[Elektroda, marek_gm, post #18561189]

How much voltage rise is acceptable on a weak feeder?

European low-voltage codes limit 10 % rise; exceeding 253 V forces the inverter to disconnect. Each extra exported kW can add ~1.5 V on a long 4 mm² line[IEA PVPS, 2021].

Edge case: What if I already have 6 kW three-phase and want a 3.6 kW single-phase add-on?

Permitted if you use three single-phase inverters (one per phase) so no phase exceeds 3.68 kW, and total stays ≤10 kW[Elektroda, marek_gm, post #18557594]
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