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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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  • #1531 20613106
    tomasz.ryszard
    Level 11  
    I think there is some other reason. Until June 1, if there were inverter shutdowns, they were sporadic (I didn't even notice them) and the inverter developed full power of 3300 W around noon. Now it's completely different - not only the inverter constantly restarts, it also cuts the power to 1 kW. I do not think that something has changed in the surrounding network that so suddenly from May 31 to June 1 there were such drastic changes in the operation of the inverter. Maybe it will show some graphs from before June 1st

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

    and some after June 01

    SOFAR 8kW PV Installation: Opinions, Durability, Failures & Experiences with Inverters SOFAR 8kW PV Installation: Opinions, Durability, Failures & Experiences with Inverters SOFAR 8kW PV Installation: Opinions, Durability, Failures & Experiences with Inverters
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  • #1532 20613127
    ja_pizgam
    Level 10  
    @tomasz.ryszard, however, it's the fault of the voltage in the network, in May you have ~ 244V and in June ~ 263V, which is too much, the inverter is supposed to turn off after exceeding 253V. You should have called the power company a long time ago to lower the voltage on the transformer. You should have 230V in the network, but the power industry reserves the right to 10% discrepancy (both ways), yours is much more. Check the AC voltage graph yourself, what is the lowest and at what times and when it exceeds 250V, if it happens in the morning (7-8) it is very bad for you.
  • #1533 20613183
    tomasz.ryszard
    Level 11  
    AT PRO wrote:
    If you have much lower in the socket at the same time, you may have poor connections somewhere or too small a cross-section of wires.


    I measured the AC voltage on the inverter connection cable (4x2.5 mm2 cable, cable length less than a meter) and the voltage is actually different than when I measured it in the socket. When the inverter is getting ready to start ("wait" message on the inverter), the voltage on this wire at the terminals in the AC junction box of the inverter is about 236V. 1 kW turns off. I don't understand something here. When the inverter is not working, the voltage comes to the AC box from the power grid and fluctuates between 236 - 237 V, which is correct and meets the standard (230 V +/- 10%) and I would expect it to come higher (over 253 V) and it, too high would cause the inverter to shut down. Meanwhile, it is the inverter, although the voltage in the network is close to the norm (237 V), it constantly increases the voltage along with the power it generates, until finally at about 260 V and reaching the power of about 1000 W, it turns off. The question is why it constantly raises the voltage if it is relatively low in the network and is it not a symptom of an inverter failure?
  • #1534 20613184
    ja_pizgam
    Level 10  
    If the inverter raises the voltage so much, there is something wrong with it, it usually only raises 2-3V.
  • #1535 20613207
    tomasz.ryszard
    Level 11  
    Exactly. It also seems to me that the inverter should increase the voltage coming from the power grid, but only by a few volts to cause the current to flow from the inverter to the grid at a higher potential than in the grid. So there are grounds to send the inverter for repair. Before I do this, I will check if the high voltage is affected by the VCX surge arrester located in the AC box of the inverter - I will just disconnect it and see if the voltage returns to normal while the inverter is running.
  • #1536 20613294
    Janusz_kk
    Level 39  
    ja_pizgam wrote:
    If the inverter raises the voltage so much, there is something wrong with it, it usually only raises 2-3V.

    Nonsense, it's the fault of the line and not the inverter, or there is no load on it or it has too high impedance, then the inverter gives power until the voltage is exceeded when it turns off, it's normal.
    You need to check the line, maybe the connections have come loose.
    Call an electrician to the Author, let him do a review and measure the impedance.
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  • #1537 20613411
    tomasz.ryszard
    Level 11  
    The devil is always in the details. In fact, it is even better to check the line before sending the inverter for repair.

    Do you mean to check the lines: the cable connecting the inverter to the AC box of the inverter, the connections in the AC box of the inverter itself and the cable between the AC box and the bi-directional meter?
    I excluded the AC box as the cause of the voltage drop (apparatus and connections in it) because I connected the inverter cable directly to the meter cable as a test.

    I understand that for a bidirectional meter to record the current flow from the inverter to the power grid, the voltage at the meter's terminals coming from the inverter must be higher than the voltage at its terminals coming from the grid. So you need to check if there is no too high voltage drop on the above-mentioned line.

    Before checking the line, I will try to check the correct operation of the inverter by connecting a load (2 - 3 kW heater) directly to its AC box, thus excluding the lack of load (internal in the building or external - mains) and possible faults on the inverter line, meter terminals.
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  • #1538 20613413
    Wawrzyniec
    Level 38  
    tomasz.ryszard wrote:
    When the inverter starts working, as the power increases, it raises the voltage from 236 V to 264 V and at exactly 1 kW it turns off.
    You have high line impedance. Turn off the inverter and load this line with a 1kW heater. The voltage will probably drop by the same amount as the inverter picks up when it shuts down. If so, you have loose wires somewhere in the connector.
  • #1539 20613437
    tomasz.ryszard
    Level 11  
    Perhaps on June 1, when the problems arose, the connection or the condition of the internal installation cable connected to the meter deteriorated. The DSO electrician who changed the ordinary meter to a bidirectional one said something about the poor condition of a single-phase cable (I have a three-phase connection but a single-phase inverter).
    But as I wrote earlier, I will load the inverter with a heater - I'm thinking about 2-3 kW and see if the inverter will stop raising the voltage so high, but it's tomorrow because at this time the photovoltaic installation is already reducing production
  • #1540 20613582
    Wawrzyniec
    Level 38  
    It's enough if you load this phase with turned off inverter. If there is a large voltage drop, the installation will be damaged. If the inverter will work, after loading this phase with a heater, you probably won't give anything to the grid anyway, because the inverter will work for the heater, and the interpretation with the inverter off is more obvious.
  • #1541 20613806
    gorajczanin
    Level 6  
    Hello
    I would like to change the country code to, for example, Germany to run on a higher voltage, but the code (password) 0001 does not enter in this case.
    I know the country code but I can't enter this menu to change it.
    Anyone help?
  • #1542 20613869
    Janusz_kk
    Level 39  
    gorajczanin wrote:
    I would like to change the country code to e.g. Germany to run on a higher voltage

    No, it's supposed to run according to our parameters. If you burn something and they put on a recorder, they'll get you. You want it?
  • #1543 20614212
    RobertB2
    Level 1  
    I have a question about increasing the power with jumpers. Since I switched from 5 to 6 kW (end of April) my maximum daily yield has not exceeded 38.9 kWh per day and the instantaneous power is 4800W.
    After returning to the old settings, the instantaneous power is even over 5kW. I have 6kWp panels on the roof. The voltage on the phases does not exceed 245V. Reactive power on 1.00 network.
  • #1544 20614217
    k_pec
    Level 34  
    gorajczanin wrote:
    I would like to change the country code to, for example, Germany to run on a higher voltage, but the code (password) 0001 does not enter in this case.

    Looks like an illegal inverter you'd like to make yourself. Have you read what penalties for such "fun" can hit and what costs you have to incur then to connect again, if your neighbor wires you?

    Instead of doing illegal, wouldn't it be better to look around for equipment to keep the inverter working on auto consumption at high voltages?
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  • #1545 20614219
    Rybus85
    Level 23  
    And from a different barrel. What are the highest temperatures you've seen on the inverter? My record today ^^ 80 degrees. I wonder how the manufacturer could give so d..yi not to mount some cooling, only the heatsink itself. I keep the distances as if according to the instructions ;)
  • #1546 20614224
    k_pec
    Level 34  
    Rybus85 wrote:
    I wonder how the manufacturer could give so d..yi not to mount some cooling, only the heatsink itself. I keep the distances as if according to the instructions

    Distances are not everything - the volume of the room and the efficiency of ventilation are also important. What's your room temperature near the inverter?

    And on the other hand - from the current equipment, you can expect anything due to the production savings associated with the planned life of the equipment. 80°C seems to be a bit too much, but maybe this guy has something like that. I wonder how it looks on others.
  • #1547 20614230
    Janusz_kk
    Level 39  
    Rybus85 wrote:
    I wonder how the manufacturer could give so d..yi not to mount some cooling, only the heatsink itself.

    Because the inverters are also intended for outdoor installation? And because of this, relying on a fan is hardly rational?
    That's why they are hermetic and have passive cooling so that you don't write what kind of stupid manufacturer it is that gives a fan to an external inverter and damn it hits it in a short time and overheats and turns off :)

    You can always screw additional fans from the bottom of the strip and blow into the heatsink, of course, unless the inverter is outside.
  • #1548 20614236
    Rybus85
    Level 23  
    NO. Inverter in the corridor, I don't know what the temperature is there. I'm curious how much it will pull ^^
  • #1550 20614286
    Rybus85
    Level 23  

    For now, I'm cooling it with a small battery (8-9 hours is fine), but I'm looking for something under USB and a permanent USB connection for the update.
  • #1551 20614837
    Baqo
    Level 16  
    tomasz.ryszard wrote:
    The DSO electrician who changed the ordinary meter to a bidirectional one said something about the poor condition of a single-phase cable (I have a three-phase connection but a single-phase inverter).
    Then swap the phases, connect it to another.

    Added after 3 [minutes]:

    Rybus85 wrote:
    And from a different barrel. What are the highest temperatures you've seen on the inverter? My record today ^^ 80 degrees. I wonder how the manufacturer could give so d..yi not to mount some cooling, only the heatsink itself. I keep the distances as if according to the instructions ;)

    Put the fan next to it and test it to see if it cuts you off.

    I have a special gravitational ventilation behind the inverter, which cools it without wasting electricity.
  • #1552 20615347
    tomasz.ryszard
    Level 11  

    Wawrzyniec wrote:
    It's enough if you load this phase with turned off inverter. If there is a large voltage drop, the installation will be damaged. As the inverter will work, after loading this phase with a heater, you probably won't give anything to the grid anyway, because the inverter will work for the heater, and the interpretation with the inverter off is more obvious.


    Today I measured the voltage in the AC box of the inverter on the terminals of the cable going from the box to the bidirectional meter in two variants
    1. Inverter disconnected from the box
    - voltage without load: 232 - 235 V
    - voltage with a load of 1000 W (farel set to 1000 W connected to the socket connected to the terminals of the box cable going to the meter): 230 - 233 V
    - voltage with a load of 2000 W (farel set to 2000 W connected as above): 229-231V
    2. 130 W inverter connected to the box (cloudy morning)
    - voltage without load: 232 - 235 V
    - voltage with a load of 1000 W (1000 W battery connected to the socket connected to the terminals of the box cable going to the meter): 234 - 235 V
    - voltage with a load of 2000 W (2000 W coil connected as above): 230 - 232 V

    As you can see, the load on the line - the cable connecting the AC connection box of the inverter with the bi-directional meter does not cause a large voltage drop:
    - max 5 V with the inverter disconnected
    - max 5 V with connected inverter

    These measurements would indicate that the inverter box - meter line does not cause too high a voltage drop (max 5 V). The length of this line is max. 6 m. On the other hand, the inverter, with the power of 1000 W generated on Sunday, boosted the voltage in the AC box of the inverter to 260-263 V from 237 V because this voltage was more or less in the box when the inverter restarted (it did not generate power). This would correspond to a voltage drop of 23 - 26 volts. It seems that it is not too high line impedance that is causing the AC box to be over-voltage, but inverter failure or something else.
  • #1553 20615484
    Janusz_kk
    Level 39  

    tomasz.ryszard wrote:
    On the other hand, the inverter, with the power of 1000 W generated on Sunday, boosted the voltage in the AC box of the inverter to 260-263 V from 237 V because this was more or less the voltage in the box when the inverter restarted (it did not generate power). This would correspond to a voltage drop of 23 - 26 volts.

    This means that the line has no load, nothing else, the inverter is good.

    tomasz.ryszard wrote:
    It seems that it is not too high line impedance that is causing too high voltage in the AC box, but inverter failure or something else.

    But what damage? to raise the higher voltage, it must either give more power, which I doubt very much, or the line is not loaded.
    Connect the farel on the same phase in full sun and then measure the voltage.
  • #1554 20615503
    civic9
    Level 12  

    If we exclude the line, I would still look at the inverter connector itself, the connection. There may also be some additional resistance at this point. Although I have no idea how to check it - it's best to disassemble and connect directly, but it's a problem (and by the way, you can measure it). Anyway, at least look carefully, check the tightening of the screws, maybe cut the end of the cable and make money again.

    I haven't read all the posts - but it seems to me that you checked the line from the meter to the AC box. And from the box to the inverter? There may also be a problem here, both with the cable itself and its connections on both sides. As well as connections within the box itself between individual devices, connectors, etc.
  • #1555 20615545
    Wawrzyniec
    Level 38  

    It looks as if the inverter emits harmonics or the generated sine wave strongly differs in shape from the sine wave, and thus the voltage measurement by the inverter and the meter is falsified. And if the inverter detects too high voltage, it turns off. The voltage increase when the inverter is operating with a power of 1 kW is certainly not greater than the voltage drop when the 1 kW inverter is turned on (with the inverter turned off). It may also be that this phase is very lightly loaded. If possible, connect the inverter to a different phase. This will rule out damage to the inverter, or choose other hours for measurements (higher network load).
  • #1556 20615580
    wddd
    Level 11  

    I, with the same inverter as they exchanged for a new one (described earlier), the guy from the service sent this new plug from AC - 3 pin. He said it's best to replace it with a new one when replacing because it often makes poor contact there."
  • #1557 20615591
    Janusz_kk
    Level 39  
    wddd wrote:
    He said it's best to replace it with a new one when replacing because it often makes poor contact there "

    But then on the AC box it would not have such a rise, only the inverter would signal it.
  • #1558 20615626
    tomasz.ryszard
    Level 11  
    Wawrzyniec wrote:
    It looks as if the inverter emits harmonics or the generated sine wave strongly differs in shape from the sine wave, and thus the voltage measurement by the inverter and the meter is falsified. And if the inverter detects too high voltage, it turns off. The voltage increase with the inverter operating at 1kW is certainly not greater than the voltage drop with the 1kW inverter switched on (with the inverter switched off). It may also be that this phase is very lightly loaded. If possible, connect the inverter to a different phase. This will rule out damage to the inverter, or choose other hours for measurements (higher network load)


    If we are talking about loading the inverter with an internal (household) load, the inverter is connected to the phase to which all loads are connected so as to maximize self-consumption and send as little electricity as possible to the power grid. In contrast, all 3 phases are connected to only one 3-phase socket, which is hardly used. Auto-consumption (home load) on Sunday during voltage measurements was about 200 W
    But in addition to the household load, there is an external (mains) load behind and before the medium voltage transformer. So I don't really understand why the inverter would not be loaded.

    I am waiting for a sunny day so that the photovoltaic panels generate a power of at least 2 - 3 kW, then I will clearly load the working inverter in the ACE box with a 2000 W heater and possibly an additional 1200 W heater and see if it will continue to raise the voltage as high as in during the measurements on Sunday. In this way, the suspicion of a lack or too little load will be excluded.
    If necessary, I will switch the inverter to another phase, although these other phases, as I wrote earlier, are unloaded (no sockets and lighting installations connected to these phases)
  • #1559 20615664
    Janusz_kk
    Level 39  
    tomasz.ryszard wrote:
    I am waiting for a sunny day so that the photovoltaic panels generate a power of at least 2 - 3 kW, then I will clearly load the working inverter in the ACE box with a 2000 W heater and possibly an additional 1200 W heater and see if it will continue to raise the voltage as high as in Sunday during the measurements.

    Exactly, measure it.

    tomasz.ryszard wrote:
    But in addition to the household load, there is an external (mains) load behind and before the medium voltage transformer. So I don't really understand why the inverter would not be loaded.

    The load may be so badly distributed that it is not present on Sundays, besides, someone else can also produce energy and boost your voltage.

    tomasz.ryszard wrote:
    If necessary, I will switch the inverter to another phase, although these other phases, as I wrote earlier, are unloaded (no sockets and lighting installations connected to these phases)

    First, find the best one, when the sun will be, turn off the inverter for a moment and measure the lowest voltage and then connect to it.
    The easiest way will then be to replace the phase cables in the main connection.
  • #1560 20615694
    gorajczanin
    Level 6  

    >>20615545
    Unfortunately, I can't change the phase because I only have one. 3.6kw inverter on the roof for now 3.2 next year I'm adding 2kw, it's interesting how it will be with this voltage then...
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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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