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SOFAR 8kW PV Installation: Opinions, Durability, Failures & Experiences with Inverters

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  • #1231 19973420
    borgen
    Level 11  
    Hello
    Please check the correctness of the modification of the photovoltaic installation. I currently have 22 Suntech STP405S-C54 / Umhb panels connected to the Sofar Solar KTLX-G3 inverter. Panels connected in two lines (strings) connected to the inverter into two separate MPPT sockets. The inverter in the settings for an independent input. The voltage on each MPPT is approx. 345 V at 25 degrees C. Due to the fact that the rated input voltage for this inverter is 600V, I would like to change the connection of these panels to 22 pcs in series, connect to two shorted MPPT inputs and switch the inverter mode to parallel input. I used a calculator from one of the well-known companies and from these calculations it follows that such a configuration is possible (in the attachments there is a screenshot of the current and planned connection)
    One thing that worries me is that the maximum DC power for one MPPT of the inverter is exceeded, which is 6000W, but the connection here will be with shorted MPPT.
    Does such a change make sense and will it increase my energy gain and possibly by what order of magnitude? I asked the Sofar Solar service about the correctness of this modification, but there is no answer yet.
    The panels are mounted on the roof of a residential building, angle of 30 degrees, the roof tilted from the south towards the east by 4 degrees (azimuth 176 degrees).
    SOFAR 8kW PV Installation: Opinions, Durability, Failures & Experiences with Inverters

    SOFAR 8kW PV Installation: Opinions, Durability, Failures & Experiences with Inverters
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  • #1232 19973457
    Janusz_kk
    Level 39  
    borgen wrote:
    One thing that worries me is that the maximum DC power for one mppt of the inverter is exceeded, which is 6000W, but the connection here will be with shorted mppt.

    If you switch them to parallel connection it will be ok, nothing will be overloaded because both mppt will work together.
    You have good parameters, from the very beginning you had to combine into one string. It will be good and even better because the inverter efficiency will be higher.
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  • #1233 19978972
    pawelec5
    Level 17  
    Hello.
    Needs to activate reactive power as recommended by suppliers.
    I have the following parameters in 11KTL-X

    Under-excitation
    Network
    Overexcitation.

    Please explain what they are for.
    Regards.
  • #1234 19979777
    prose
    Level 35  
    @ pawelec5 You will reduce it to 0.9 from 1, you will reduce the production and thus the voltage drop, the button gives in total.
  • #1236 19983330
    dddmmm
    Level 9  
    Hello
    I would like to ask you to check the operation of my 9.9 kWh photovoltaic plant, which produces very little energy. Currently, I have 22 Jinko 450W Half Cut / Perc panels connected to the Inverter Sofar 11 KTL-X inverter, ground installation, south-facing, open area without shading. In April, the best production is 37.66 kWh. Panels connected in two strings connected to the inverter with two separate mppt sockets. On average, the voltage at each mppt is approximately 370-410V
    Maybe someone will tell you what I should check, one of the problems is probably too high voltage in the network, so I will try to involve Tauron, but I do not know if this is the only problem.

    Darek
  • #1237 19983564
    Janusz_kk
    Level 39  
    You have too weak an inverter for these panels, 450W have a max of 13A and an inverter 11A and here it cuts once, two too few panels per string, according to the table, the full power voltage is why the inverter is 480V and this is not what your panels will achieve, here it cuts a second time, hence such and no other results. This is how you buy items rather than pick them.
    dddmmm wrote:
    The best production in April is 37.66 KkWh

    And I have, despite the shading for 8960W of power, 45.6kWh in April on the best day, do you see the difference?

    Added after 1 [minutes]:

    I would like to add that the total amount was probably a few kWh more.
  • #1238 19983917
    Baqo
    Level 16  
    dddmmm wrote:
    Hello
    Sofar 11 KTL-X inverter
    Or maybe you have one?
    SOFAR 11KTLX-G3
    I would replace it with SOFAR 8.8KTLX-G3
  • #1239 19983979
    dddmmm
    Level 9  
    I have checked the invoice once again that I have a Sofar 11 KTL-X Inverter, nothing else is there. I bought the whole set at PVGroup from Chorzów, they had good opinions on the Internet and they were close, I live in Silesia. I contacted the Sofar service regarding the connection and they said that I should connect the panels on two strings. I wonder what to do now?

    Added after 8 [minutes]:

    Janusz_kk wrote:
    You have too weak an inverter for these panels, 450W have a max of 13A and an inverter 11A and here it cuts once, two too few panels per string, according to the table, the full power voltage is why the inverter is 480V and this is not what your panels will achieve, here it cuts a second time, hence such and no other results. This is how you buy items rather than pick them.
    dddmmm wrote:
    The best production in April is 37.66 KkWh

    And I have, despite the shading for 8960W of power, 45.6kWh in April on the best day, do you see the difference?

    Added after 1 [minutes]:

    I would like to add that the total amount was probably a few kWh more.

    I do not know about inverters, but the one I bought is oversized anyway because it is for 11 KW, I bought the entire set from the PV Group from Chorzów, so I assume that it was selected by professionals. The Sofar service advised that you need to connect the panel in two strings.
  • #1240 19983999
    Janusz_kk
    Level 39  
    dddmmm wrote:
    I contacted the Sofar service regarding the connection and they said that I should connect the panels on two strings.

    What is not surprising to me, they deal with inverters and not with the selection of equipment for the installation. Who did the installation for you?
  • #1241 19984041
    dddmmm
    Level 9  
    Janusz_kk wrote:
    dddmmm wrote:
    I contacted the Sofar service regarding the connection and they said that I should connect the panels on two strings.

    What is not surprising to me, they deal with inverters and not with the selection of equipment for the installation. Who did the installation for you?

    I bought the whole set, inverter, panels and other elements from them, only then I bought 6 mm cables and additional security. The installations were connected by an electrician from Tauron
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  • #1242 19984052
    Baqo
    Level 16  
    dddmmm wrote:
    I have checked the invoice once again for the Sofar 11 KTL-X Inverter,

    Check the nameplate of the inverter.
  • #1243 19984063
    Wiesiekkojot
    Level 11  
    hello I'm looking for a ktlm g2 software thank you
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  • #1245 19984125
    dddmmm
    Level 9  
    Janusz_kk wrote:
    You have too weak an inverter for these panels, 450W have a max of 13A and an inverter 11A and here it cuts once, two too few panels per string, according to the table, the full power voltage is why the inverter is 480V and this is not what your panels will achieve, here it cuts a second time, hence such and no other results. This is how you buy items rather than pick them.
    dddmmm wrote:
    The best production in April is 37.66 KkWh

    And I have, despite the shading for 8960W of power, 45.6kWh in April on the best day, do you see the difference?

    Added after 1 [minute]:

    I would like to add that the total amount was probably a few kWh more.

    Should he then attach the panels to one string? As I mentioned, the Sofar website advised to use two strings.
  • #1246 19984141
    lary504
    Level 12  
    The inverter has a 2X11A input, your panels max over 13A. I would combine the panels into one string and use a splitter from one string to two inputs. Then it will not cut your electricity. Oh, and changing the input type to parallel. But, in order not to be fun, you will have the voltage, like now, it is probably about 800V, which is a lot, but still within the range. The problem may be with frost in winter, I do not know if it will not exceed the permissible voltage. But I would check that later. The best solution would be to replace the inverter so that you have 14A at the input, but if it is not an option, I would do as above.
  • #1247 19984182
    dddmmm
    Level 9  
    lary504 wrote:
    The inverter has a 2X11A input, your panels max over 13A. I would combine the panels into one string and use a splitter from one string to two inputs. Then it will not cut your electricity. Oh, and changing the input type to parallel. But, in order not to be fun, you will have the voltage, like now, it is probably about 800V, which is a lot, but still within the range. The problem may be with frost in winter, I do not know if it will not exceed the permissible voltage. But I would check that later. The best solution would be to replace the inverter so that you have 14A at the input, but if it is not an option, I would do as above.


    Thank you very much for the hint, I wrote a complaint to the PV Group just now because they chose the inverter for the panels, we'll see what they will do. I will probably wait for an answer, min. a week and then will try to do what you say although I have to find some local expert to try to fix this as you suggest.
    Maybe you can recommend someone who is a specialist in this field and works in Silesia, specifically in Sosnowiec or its vicinity?
  • #1248 19984226
    Janusz_kk
    Level 39  
    dddmmm wrote:
    I bought the whole set, inverter, panels and other elements from them, only then I bought 6 mm cables and additional security. The installations were connected by an electrician from Tauron

    So what, the store sold you what you wanted, the electrician connected and there is no designer who will design and calculate all the components.

    dddmmm wrote:
    Should he then attach the panels to one string? As I mentioned, the Sofar website advised to use two strings.

    So connect them in series and set the parallel connection in the inverter settings for mppt. It is true that you have a bit too many panels and it is on the border of the inverter because I get 1034V, but hopefully there will be no frost after -25 degrees :)
  • #1249 19984297
    dddmmm
    Level 9  
    Janusz_kk wrote:
    dddmmm wrote:
    I bought the whole set, inverter, panels and other elements from them, only then I bought 6 mm cables and additional security. The installations were connected by an electrician from Tauron

    So what, the store sold you what you wanted, the electrician connected and there is no designer who will design and calculate all the components.

    dddmmm wrote:
    Should he then attach the panels to one string? As I mentioned, the Sofar website advised to use two strings.

    So connect them in series and set the parallel connection in the inverter settings for mppt. It is true that you have a bit too many panels and it is on the border of the inverter because I get 1034V, but hopefully there will be no frost after -25 degrees :)

    I will do as you say, but I did not buy what I wanted, only a ready set recommended by the seller, I know it completely and relied on the seller, as I wrote earlier, I chose one that had good opinions. And what will happen when there are big frosts, unfortunately such frosts happen several times a year?
  • #1250 19984322
    Janusz_kk
    Level 39  
    Frost -25 has been gone for a long time, and what will happen, the open circuit voltage will increase, i.e. in the morning when there is no sun yet and the panels already give the voltage, it will be higher than normal, the colder the higher, when the threshold is exceeded, the inverter will crash the overvoltage error, as it grows further it may damage the inverter. But when the sun shines, the inverter will start working (unless it is wrong) and then the voltage will drop under load. as I counted, your voltage will not exceed 1100V, which is the maximum for the inverter.
  • #1251 19984381
    dddmmm
    Level 9  
    Janusz_kk wrote:
    Frost -25 has been gone for a long time, and what will happen, the open circuit voltage will increase, i.e. in the morning when there is no sun yet and the panels already give the voltage, it will be higher than normal, the colder the higher, when the threshold is exceeded, the inverter will crash the overvoltage error, as it grows further it may damage the inverter. But when the sun shines, the inverter will start working (unless it is wrong) and then the voltage will drop under load. as I counted, your voltage will not exceed 1100V, which is the maximum for the inverter.

    so I don't have to worry about damaging the inverter?
  • #1252 19984429
    xury
    Automation specialist  
    Does anyone know what the files on the card named "." Are for (8 spaces, a period, 3 spaces) and how to read them?
  • #1253 19984451
    Janusz_kk
    Level 39  
    dddmmm wrote:
    so I don't have to worry about damaging the inverter?

    Nobody will give you a 100% guarantee, but according to these data, everything should be ok.
  • #1254 19984511
    Baqo
    Level 16  
    dddmmm wrote:
    I didn't buy what I wanted, only a ready-made set recommended by the seller.

    You were buying when there are hardware shortages and they gave you what they had in stock at an attractive price.
  • #1255 19984551
    msr99
    Level 20  
    dddmmm wrote:
    Thank you very much for the hint, I wrote a complaint to the PV Group just now because they chose the inverter for the panels, we'll see what they will do


    Oil
    It works? No. it works for you
    Follow the advice. You don't need an electrician for this
  • #1256 19984716
    Janusz_kk
    Level 39  
    msr99 wrote:
    Oil

    Exactly, do as I wrote you, it will be better than now.
  • #1257 19984815
    m2tk
    Level 13  
    dddmmm wrote:
    The best production in April is 37.66 KkWh

    I have a set of similar power (Jinko Tiger 460W + Sofar 12KTLX-G3) and the maximum production is over 70kWh (2x in April).

    But G3 is probably a different class of equipment (I max = 15 / 30A)
  • #1258 19985396
    jjj111222333
    Level 2  
    Are Safety parameter files available for the 11KTL-X (not G3) models??? My country settings set the voltage too high for the Low Voltage tripping.

    The manual talks about copying a TXT file into the SD card before changing SafetyVolt parameters. Does anyone have access to the TXT file??? Why is this file such a secret???

    SOFAR 8kW PV Installation: Opinions, Durability, Failures & Experiences with Inverters

    Jen!
  • #1259 19985428
    dddmmm
    Level 9  
    m2tk wrote:
    dddmmm wrote:
    The best production in April is 37.66 KkWh

    I have a set of similar power (Jinko Tiger 460W Sofar 12KTLX-G3) and the maximum production is over 70kWh (2x in April).

    But G3 is probably a different class of equipment (I max = 15 / 30A)

    Thanks for the information, I will use it in talks with PVGroup, the complaint is submitted, I will wait for their reaction, if necessary, I will go to court because I was beaten.

    Added after 6 [minutes]:

    Janusz_kk wrote:
    msr99 wrote:
    Oil

    Exactly, do as I wrote you, it will be better than now.

    I think I will not wait for PVGroup's response, but I will change the installation connection to begin with, and then we will see how the complaint ends. I asked to replace the inverter with one suitable for the panels. Attach all panels to one string seems simple and I think I can do it, but changing the inverter settings can be a problem, I don't want to spoil something. Maybe you can suggest how to do it?

    Added after 5 [minutes]:

    m2tk wrote:
    dddmmm wrote:
    The best production in April is 37.66 KkWh

    I have a set of similar power (Jinko Tiger 460W Sofar 12KTLX-G3) and the maximum production is over 70kWh (2x in April).

    But G3 is probably a different class of equipment (I max = 15 / 30A)

    Do you have panels attached to one or two thongs?
  • #1260 19985562
    Janusz_kk
    Level 39  
    dddmmm wrote:
    Maybe you can suggest how to do it?

    Open this file with the manual, preferably on a laptop, on page 41 you have buttons and a description, press 1 on the left (menu)
    and use the arrows to the 1st setting and right (ok) you enter, then the arrows to the 9th position set the mppt again ok and with the arrows you change from 'independent' to 'parallel', approve ok and exit 'menu', 'menu', ' menu 'I don't think he should ask for a password and as he says, select 0001 with the arrows and confirm with approx.
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Topic summary

The discussion centers on experiences with Sofar inverters in approximately 8kW photovoltaic (PV) installations, focusing on technical issues, durability, and configuration challenges. Users report generally stable operation with models like Sofar 6.6KTL-X and 5.5KTL-X over extended periods, though some face connectivity problems, especially with Wi-Fi and software availability. A recurring technical problem involves input voltage exceeding the maximum allowed 600V DC for single-phase Sofar inverters (notably the 4KTLM-G2), causing errors such as PVOVP and BusOPV and inverter shutdowns. This is often due to too many PV panels connected in series on a single string, with 15 Q.CELLS Q.PEAK G4.1 305W panels sometimes exceeding voltage limits, especially in cold conditions where voltage rises. Solutions include splitting panels into two strings (e.g., 8 and 7 panels) connected to separate MPPT inputs, though some users report this does not fully resolve the issue. The maximum recommended panels per MPPT input is around 9 to avoid surpassing power and voltage limits. Users also discuss the need for three-phase inverters for larger installations above 7kW on a single phase due to grid operator restrictions. Software and firmware updates are sought after but not easily accessible, with some users lacking Polish language support. Comparisons with other brands like SMA and Fronius highlight Sofar's cost advantage but raise concerns about long-term reliability and service support, which is still developing in some regions. Network-related errors such as Grid OFP (over-frequency) have been reported, with troubleshooting involving network frequency checks and inverter restarts. Overall, Sofar inverters are considered a cost-effective option with some technical caveats related to system design, installation quality, and support infrastructure.
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