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

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How reliable are Sofar inverters for an around-8 kW PV installation, and what problems or failures do users report?

Users report mostly acceptable results: one 6.6KTL-X had no problems for over a year, and another 8.8KTL-X owner said a firmware update to v2.20 removed the old clipping around 8 kW and let the inverter reach full peak power [#18112697] [#18662870] [#19158337] The most common problems in the thread were not outright inverter defects but installation/configuration mistakes: too many panels in one string or the wrong input mode caused DC overvoltage errors such as PvOVP, BusOPV or permanent fault, and the cure was to wire the strings correctly and keep each MPPT within its limits [#18322870] [#18323108] [#18359020] [#18360610] [#18699492] Another recurring issue was grid overvoltage: users saw ID01/Grid OVP shutdowns when mains voltage rose to about 253 V, and one case reached 280 V at the customer side; the inverter was behaving as designed in those cases [#18624602] [#18665849] A few users also mentioned Wi‑Fi/software quirks and awkward warranty handling, with the installer, seller, distributor and Sofar service bouncing responsibility between each other [#18306997] [#18322870] [#18323064] [#18331261] [#18772451] There was at least one real hardware failure report, where an 8.8KTL-X tripped AC overcurrent after about a month and then would not restart, so the unit had to go through warranty [#18771167]
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  • #31 18323557
    noja102
    Level 24  
    Well, you have exceeded the maximum voltage on frosty and sunny days http://solar-tech.pl/wp-content/uploads/2017/07/QCells-290W-305W.pdf, i.e. about 608 V and the inverter will not start http: / /www.sofarsolar.com/product-detail/459/SOFAR%204KTLM-G2 detach 2 panels or divide into 2 chains one 8 panels the second 7, try 1 option first, because the second is additional cables and protection must be installed. Give me more photos of what '' Miszcze '' has installed

    Added after 7 [minutes]:

    PS
    To disconnect the panels, you need to turn off the inverter from the AC mains and wait at least 5 minutes then the DC MC4 plug so that it does not kill you, or call an electrician because it is better not to bury yourself with this voltage, and you must advertise because in this option it may cause a fire (and are surprised that UDT will need to connect the installation)
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  • #32 18323613
    kosmos99
    Level 38  
    iwostar wrote:
    It does not look like there are too many panels, because in summer itself it worked normally on sunny days, and it can turn off on a cloudy day, although I think it may be affected by the sudden departure of strong sun from outside the clouds.


    It looks to me that the problem is with the network. 4kW goes to one phase in the absence of reception, the voltage increases in this phase and hence this BUSOpv error.
    There are no new installations at the neighbors?
  • #33 18323686
    noja102
    Level 24  
    DTR error description
    Attachments:
    • 2019-12-06_200639.pdf (1.57 MB) You must be logged in to download this attachment.
    • 2019-12-06_200544.pdf (1.65 MB) You must be logged in to download this attachment.
    • 2019-12-06_200423.pdf (1.86 MB) You must be logged in to download this attachment.
  • #34 18323898
    iwostar
    Level 10  
    What do you think about replacing the inverter with a more powerful one? I plan to put another 8-9 panels on the shelter in the spring, this one would come in handy then.

    I will try to connect an energy-consuming receiver at the time of the error. We'll see if it will change anything ...

    Nothing has changed with the neighbors lately.
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  • #35 18323951
    grzeziu
    Level 12  
    the receiver will not help, it was necessary to buy a larger inverter and connect 2 strings 15 and 9 panels, about 6000w-8000w
    so that the string supports about 4000 in
  • #36 18324236
    noja102
    Level 24  
    And one more question, how far from the main switchboard you have the inverter connected and what is the cross-section of the cable to it
  • #37 18324380
    3301
    Level 34  
    I think that it is unnecessary to consider replacing the inverter with a more powerful one, unless in terms of not the power but the input voltage, because the problem here is the DC input voltage, as indicated by the displayed errors
    This inverter has two inputs so why not split this 15 panel circuit
  • #38 18325013
    iwostar
    Level 10  
    I have to find a specialist in the area who will undertake such a modification.
    I think that the purchase of a more powerful inverter would also make sense when investing in a second set. It seems to me that two inverters are a safer and financially similar solution, as one powerful for two sets.
  • #39 18326299
    hupo
    Level 14  
    iwostar wrote:
    in the summer itself, on sunny days, it works normally, and it can turn off on a cloudy day, although I think it may be affected by the sudden exit of the strong sun from outside the clouds.

    A panel heated to 55C (for example RSM60H-156PE, others are similar) generates a voltage to almost 4V lower than a panel cooled to 25C at the same sunlight and operating current.
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  • #40 18330958
    wello
    Level 20  
    Do not call a specialist, but the company that installed it for you. Tell them you know what is causing it. Have them come and split the panels into two strings (8 + 7).
  • #41 18331240
    iwostar
    Level 10  
    I do not plan to cooperate with the company that installed the kit for me. They turned out to be bunglers. In addition, I have not received an invoice for the inverter, panels or warranty cards from them. Financially, the topic is also partially unregulated, but they prefer to leave it that way.
    In the spring I plan to install another 10 panels, and probably by the way a chapter of the current set will be made, as you suggest.
    The equipment is currently working. Inverter errors and stalling occur only under certain weather conditions.
    Thanks to everyone for the advice so far! :)
  • #42 18331243
    grzeziu
    Level 12  
    you didn't get the papers when you connect the meter

    Added after 1 [minutes]:

    you need to warn against this company as it was called
  • #43 18331261
    iwostar
    Level 10  
    I got the papers for PGE. I have a counter for a long time.
    The company's bungling consisted of:
    1. They could not count how many panels would fit on the roof slope intended for the panels and had to order and reassemble additional panels.
    2. During the first assembly they did not use a spirit level or any measure. The panels were at different heights (keyed) and above the top of the roof. They had to rearrange everything the next time they visited it to comply with the rules and levels.
    3. They couldn't count the right inverter and changed it in the meantime. As it turns out, it is still not suitable or properly connected.
    The company GlobalSun - Sanok.
  • #44 18331264
    grzeziu
    Level 12  
    If you want, write wgrzeziu(_at_)wp.pl

    Added after 3 [minutes]:

    DUAL MC4 connectors - PV parallel connections.
    Buy something like this on Allegro, connect 2 pluses in the inverter so that 1 end of the inverter comes out and do the same with the minus - you will bridge mp trackers and get full power and it should be git
  • #45 18331284
    iwostar
    Level 10  
    Thanks again! Wish you live closer :)
  • #47 18331312
    theo33
    Level 27  
    After all, the parallel bridging of the inverter inputs, which is proposed by the col.Grzeziu, will not reduce the voltage of the string which consists of 15 panels connected in series, the voltage at certain temperatures will still be too high
  • #48 18331317
    grzeziu
    Level 12  
    But 2600 W is provided for 1 string, then either separate the panels either like this, or 2 pages as it was written, e.g. 8 and 7 and it comes out the same
  • #49 18331332
    theo33
    Level 27  
    Separate the current panel string into two circuits and connect each to a separate MPP input
    And it is not the same as connecting the current string to the inputs connected in parallel
  • #50 18331338
    grzeziu
    Level 12  
    By dividing the wires into 2 strings and additional protection, it is best to make 1 string of 8 panels and see what will happen
  • #51 18359020
    iwostar
    Level 10  
    Buddy Grzeziu, you were not right, unfortunately. Separation did not work ...
    When the voltage reaches 600 V, the inverter is turned off. Question for experts: will the inverter actually "pull" 15 panels? Could there be any other problem?
    In the spring, my idea was to connect 10 more panels to the second circuit, and here it turns out that 15 of them are too many and they will have to be separated ...
  • #52 18359024
    grzeziu
    Level 12  
    I have 28 panels connected to one inverter, each 280 W panel, 18 and 10 panels on each string, on one approx. 630 V, nothing is happening,

    Added after 2 [minutes]:

    If you separate the panels or unplug a part, you will not reach 600 V on 1 string, there is no chance.
  • #53 18359561
    iwostar
    Level 10  
    I understand you have a more powerful inverter. The ones I found on the SOFAR have a limit of 600V.
    A question for professionals: can the SOFAR 4KTLM-G2 inverter "pull" 15 PV panels Q.CELLS Q.PEAK G4.1 305 MONO BLACK?
  • #54 18359577
    grzeziu
    Level 12  
    It is strange to write how you separated these panels, because if they would work at max, you would slightly exceed 600 V.
  • #55 18359582
    iwostar
    Level 10  
    grzeziu, no offense, the question is for professionals.
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  • #56 18360391
    BikeBarian
    Level 24  
    iwostar wrote:
    I understand you have a more powerful inverter. The ones I found on the SOFAR have a limit of 600V.
    A question for professionals: can the SOFAR 4KTLM-G2 inverter "pull" 15 PV panels Q.CELLS Q.PEAK G4.1 305 MONO BLACK?


    For this inverter, you have to meet a total of several conditions for each MPPT:
    1) min V DC: 120V
    2) Max V DC: 600V
    3) Optimal V DC: 360V
    4) MPPT V DC range: 90 -580V
    5) Recommended DC voltage range for one MPPT: 200V - 520V
    6) Max I on DC: 11A
    7) Max DC power for single MPPT: 2600W

    Your PV panels at STC May:
    9.35A and 32.6V

    If you connect them in series to one MPPT in the inverter then:
    15 * 32.6 = 490V and the same with the current, so here it is OK but you exceed the allowed power for one MPPT, so the maximum that you can connect to one MPPT is 9 panels (9 * 305W = 2750W> recommended 2600W but these are the conditions for STC, so practically impossible to achieve in real use)

    If you plan to add another 10 panels, then with this inverter you will not succeed ... you will exceed the power for single MPPTs, so the maximum what you can do with these panels are two chains with 9 panels per string.
  • #57 18360610
    iwostar
    Level 10  
    BikeBarian, thank you very much for your explanations!
    In the context of this, it is difficult for me to understand how the company that assembled the kit made a mistake and how this kit works in general, because errors and disconnection occur only under certain conditions.
    Which inverter from, say, SOFAR would be suitable for me, so that there would be no need to separate the existing panels into two systems, and in addition, you could think about adding another 10 pcs?
  • #58 18360623
    kosmos99
    Level 38  
    iwostar wrote:
    Which inverter, let's say, from SOFAR, would be suitable for me, so that there was no need to separate the existing panels into two systems, and additionally, to add another 10 pcs?


    If you want Sofar then: sofar-8-8ktl-x
  • #59 18360693
    3301
    Level 34  
    kosmos99 wrote:
    iwostar wrote:
    Which inverter, let's say, from SOFAR, would be suitable for me, so that there was no need to separate the existing panels into two systems, and additionally, to add another 10 pcs?


    If you want Sofar then: sofar-8-8ktl-x


    And 3-phase connection. 8kW and you wrote about 4.5 and 1-phase.
  • #60 18360851
    BikeBarian
    Level 24  
    On the stubborn with 24 panels, the 305W Sofar 6KTLM-G2 would pull two strings of 12 panels each, but you probably have a 1F inverter now, so such a change would probably not pass because the OSD more than 3600W per phase is no longer released. You would have to give a larger inverter but then 3 phases or stay with it (and change the number of panels in the string) and add another 1 phase inverter for the second phase.

    So with the current installation, changing the number of panels to a string and if you add another 10 panels, you will still have to switch to 3F because over 7Kw on one phase no OSD wants.
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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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FAQ

TL;DR: Field owners report 0–20 % daily energy loss when Sofar inverters trip on 253 V grid peaks; “set Country Code 12 for Poland and the problem goes away” [Elektroda, 3301, post #18624621] Why it matters: one menu setting often fixes most unexpected shutdowns without replacing hardware.

Quick Facts

• Max. DC input voltage 1000 V & MPPT window 240-850 V (Sofar 8.8KTL-X manual [Uri, #18921613]) • Recommended DC/AC oversize ratio ≤ 1.2 : 1 for KTL-X models [Elektroda, BikeBarian, post #18360391] • Country Code list: PL = 12, DE = 07, NL = 05 [Elektroda, Defence & 3301, post #18851696] • Typical firmware: V2.30 (increases AC limit from 4.0 kW to 4.4 kW on 4.4KTL-X) [Elektroda, prose, post #19034268] • Service e-mail: service.pl@sofarsolar.com; hotline +48 22 123 98 58 [Elektroda, AT PRO, post #18772451]

How reliable are Sofar inverters in everyday use?

Most 6–9 kW owners report trouble-free work for 1–3 years [Elektroda, iborkim, #18112697; Elekt...

Which menu code should I select for Polish grid parameters?

Use Country Code 12 (PL). It lifts the over-voltage trip to 253 V/10 min and 264 V/1 s, matching Polish NC-RFG limits [Elektroda, 3301, post #18851696] Selecting 07 (DE) raises the limit to 264 V but violates declaration of conformity.

My inverter shows ID01 ‘GridOFP’ and stops at noon—what now?

Measure L-N voltage; if it rises above 253 V, ask the DSO to lower tap settings or move PV to another phase. Until then, temporarily change Country Code to DE (07) or install a 230 → 220 V autotransformer [Elektroda, MariuszFEG, post #18623709]

What causes PvOVP / BusOPV errors on 4KTLM-G2 units?

Voc exceeds 600 V in cold sun. Split the 15-panel string into two of 8 + 7 or use a 3-phase inverter that accepts 1000 V DC [Elektroda, noja102, post #18323557]

Is the MPPT Scan function worth enabling?

Enable only when partial shading occurs; it rescans the IV curve at user-set intervals. Service says it "improves harvest under shade" but reduces output 1–2 % on clean arrays [Elektroda, 3301, post #18622124]

How do I update Sofar firmware myself?

  1. Copy the /firmware folder to the SD card.
  2. Insert card, choose Menu → 5.Software Update, enter password 0715.
  3. Wait until ‘Update DSP1 OK’, ‘DSP2 OK’, ‘FUSE OK’, then reboot [Elektroda, Grucha383, post #19029218]

The display boots for one second at dawn—is that harmful?

No. The capacitors charge when DC rises above 180 V, then discharge if current is < 20 mA; this soft-start repeats without affecting lifespan [Elektroda, rydzyk673, post #19035241]

Why does Solarman show 0.9 A per phase even at 0 W?

Firmware ≤ V2.30 reports reactive standby current as active. Real clamp-meter reading is ~0.2 A; ignore the dash-board figure until a patch arrives [Elektroda, wilk125, post #19038447]

Edge case: can the inverter fail after a breaker trip?

Yes—one 8.8KTL-X died after a 16 A AC breaker opened; display stayed dark despite correct DC voltage, requiring warranty swap [Elektroda, gotycki1, post #18771167]

How to auto-run a 1.5 kW boiler only on surplus PV?

Install a PR-energised relay with the inverter’s CT loop; set closure above 4.5 kW export so the heater engages only in excess production [Elektroda, 3301, post #19053070]
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