Lots of recalls of solar panel DC disconnect switches - Page 1
Forum section: electronics / projects

author: Vell
author_rank: Contributor
timestamp: May 30, 2019, 08:48:28 pm
content: Hi,Could it be that present-day switch designers don't realize that interrupting considerable DC power creates an arc, unless contacts part quickly? Maybe they even need a blowout magnet? I surely don't want to speak ill about Aussie designers, though!Lever-type wall light switches in the USA used to have an over-center toggle linkage and spring. Initial movement of the lever tensed the spring, and when it went "over-center", it opened the contacts quickly and far apart. You could hear the snap action in another room. Those switches were used in the earlier 20th century, being needed when lots of houses and offices early in the century (afaik!) had DC from the utility.Once AC became just about universal, zero current at 120 Hz (100 Hz elsewhere) let arcs extinguish, and made internal design simpler.

author: floobydust
author_rank: Super Contributor
timestamp: May 30, 2019, 09:55:31 pm
content: There's many different ways a disconnect can fail. Faulty contacts, faulty operator.Notice some have only CE stickers on themno decent regulatory testing and approval.I wish they had a simple indicator LED in there. Don't tell anyone, but I add one. Two resistors, LED and diode.From the Australian recalls for various models:"If the isolator switch overheats it may pose a risk of fire or electrocution.""There is a potential risk of fire from faulty contacts within the internal mechanism of this switch.""The internal switch plates can generate high temperatures, causing the contacts to spread and the polymer support plate to degrade.""The product features an internal fault, where a high resistant connection may form."https://www.productsafety.gov.au/system/files/recall/NHP%20Product%20Recall%20Advert.pdfthis switch mechanically fails and looks off but is on

author: wasyoungonce
author_rank: Frequent Contributor
timestamp: May 30, 2019, 11:41:15 pm
content: Pretty sure most isolators come from China....which explains everything.I’m going to check my isolators ...Sent using iPhone

author: floobydust
author_rank: Super Contributor
timestamp: May 31, 2019, 12:03:00 am
content: The NHP isolator usesKatkofrom Finland. Only CE approved, they took down their approvals listing page, and crappy polycarbonate enclosure. Better model is in cast aluminium box but still a plastic knob. Looks to be just an import from in china.I would not go near one without basic electrical safety certification. And mount it in the shade!

author: AndersJ
author_rank: Frequent Contributor
timestamp: May 31, 2019, 12:21:46 am
content: How do solar panel DC disconnect switches differ from other switches?Why is this a topic here, emphasizing ”solar panel DC disconnect”?

author: nctnico
author_rank: Super Contributor
timestamp: May 31, 2019, 12:51:20 am
content: Quote from: AndersJ on May 31, 2019, 12:21:46 amInterrupting DC at several ampere is not a walk in the park. You'll need the right contact design for that. If someone cut corners and used contacts intended for AC in these switches then that is a huge problem.

author: Siwastaja
author_rank: Super Contributor
timestamp: May 31, 2019, 06:08:10 am
content: Quote from: wasyoungonce on May 30, 2019, 11:41:15 pmUnnecessary, rasist, and plainly wrong.Most high-quality, safe things come from China as well as the dangerous crap.Some of the most dangerous electronic products I have seen were proudly designed and made in Germany (<0.2mm creepage distance between 230V live and user-accessible secondary, half of the capacitors tombstoned with no quality control at all, etc...), and they sure played the "German quality engineering" card. They were still arrogant after being busted.As floobydust showed above, here in Finland total shit gets designed and/or produced. It's the same, too much arrogance and marketing. We in the West seem to think that just by not being Chinese, even our crap smells good. Don't fall into this trap. Be good. Be humble in front of science and engineering, electrons don't understand prejudice or politics.

author: wasyoungonce
author_rank: Frequent Contributor
timestamp: May 31, 2019, 08:17:57 am
content: Quote from: Siwastaja on May 31, 2019, 06:08:10 amLook man not looking for a flame war so why look for "Racial issues" when none was intended. Stop reading between the lines and don't put words in my mouth!

author: soldar
author_rank: Super Contributor
timestamp: May 31, 2019, 08:34:32 am
content: Quote from: wasyoungonce on May 30, 2019, 11:41:15 pmWhat does it explain exactly? Or is it just one more stupid putdown of all things Chinese? In any case I will discuss the issue if you want.

author: soldar
author_rank: Super Contributor
timestamp: May 31, 2019, 08:38:26 am
content: Quote from: Vell on May 30, 2019, 08:48:28 pmI am pretty sure present-day switch designers do realize that interrupting considerable DC power creates an arc, unless contacts part quickly.Can you give us more specific information about what is the issue you are trying to discuss?

author: mikerj
author_rank: Super Contributor
timestamp: May 31, 2019, 11:29:27 am
content: Quote from: AndersJ on May 31, 2019, 12:21:46 amBecause Dave's solar installation has failed due to a bad isolation switch. I agree the topic is very random and assumes everyone has watched Dave's video.https://www.eevblog.com/forum/blog/eevblog-1217-my-home-solar-power-system-failed!/

author: ogden
author_rank: Super Contributor
timestamp: May 31, 2019, 11:59:12 am
content: Quote from: mikerj on May 31, 2019, 11:29:27 amTopic is educational. Many may not know dangers of mechanical DC switching. Demonstration of DC switch arcing which does not happen in case of AC:https://youtu.be/mQpzwR7wLeo?t=359

author: mikerj
author_rank: Super Contributor
timestamp: May 31, 2019, 01:02:13 pm
content: Quote from: ogden on May 31, 2019, 11:59:12 amFair point, I didn't state that very well! I don't know why I used the word "topic", I meant that the OP's post is completely without context and appears very random if you haven't watched Dave's video.

author: Circlotron
author_rank: Super Contributor
timestamp: May 31, 2019, 01:52:07 pm
content: Quote from: Siwastaja on May 31, 2019, 06:08:10 amI think the statement is nationalist, not racist.Condemning Asian people rather than the Chinese nation would be racist.

author: floobydust
author_rank: Super Contributor
timestamp: May 31, 2019, 06:37:19 pm
content: Quote from: Siwastaja on May 31, 2019, 06:08:10 amThis looks like a cowboy installation, from theKatkowebsite. 390 panels 100kW.The panels and PVM disconnects with just loose wires in a homemade sheet metal boxRain is sure to get in. At least there is a ground wire. I hope the panels aren't just sitting on the wood. Unless there is no wind in Finland?Solar electrical equipment somehow can ignore mains electrical safety standards.Approvals are required on components, wire, boxes etc. but this install looks hokey.

author: Siwastaja
author_rank: Super Contributor
timestamp: May 31, 2019, 08:12:23 pm
content: Well, to be fair, it's hard to judge from such photos. I don't see any issue in using polycarbonate plastic, if it's of proper quality. I'd like to see a teardown of the actual contacts, and/or a test report before making any judgement. Of course, for expensive not-from-Aliexpresssafety switches, I'd expect at least one or two independent test lab markings, but not having them doesn't prove them dangerous, and they haven't been required by law for... two decades now?Yes, we do have wind here, but we also have a new emerging trend of having more and more massive power outages whenever there is some wind, due to a political decision of maximizing the number of trees near the power lines. I can see that distributed power production, such as solar, poses a threat for thiswind-interrupted power distribution system, so it's completely logical to make sure the wind affects solar production directly, as well!

author: soldar
author_rank: Super Contributor
timestamp: May 31, 2019, 09:23:54 pm
content: Quote from: Circlotron on May 31, 2019, 01:52:07 pmIt is still unacceptable.

author: SparkyFX
author_rank: Frequent Contributor
timestamp: May 31, 2019, 11:00:04 pm
content: I am pretty sure physics work the same in China as it does everywhere else and that you can find properly built equipment in China, in use, time-tested and proofed. No one likes to live with these dangers.Btw. Benedict GmbH is located in Austria, the switch from Daves video was made in Austria,click.In Dave´s video it was quite obvious that weather and exposure to the elements made the enclosure fail, which then led to a failing electrical contact.Electricians are usually not mechanical engineers, roofers or plumbers, but you kind of need these skills to get longevity. If you´d told someone 30 years ago to install a switch in an enclosure on top of the roof... it´d better be a good one. Even if it is rated for the UV and IP65 as stated, there are still temperature swings, expansion, humidity changes and vibration from wind that chew on the plastics and create mechanical stresses, depending on how tight the (metal) screws are torqued down.IMHO the thing either needs a different place or some better mounting, like a piece of sheetmetal above it or be made out of stainless metal in itself with some thought given for the conductors going in and out. But different materials mean different problems.I´ve seen some articles on fires caused in solar installations over the years, which usually creates the pressure on regulators to raise/set minimum requirements. Maybe the switch is required at that place for firefighters to be able to disconnect it and not get additional dangers due to the energy generated by the panels, it would be bad when the safety device itself turns into the source of the hazard.

author: wraper
author_rank: Unknown
timestamp: May 31, 2019, 11:07:54 pm
content: Quote from: floobydust on May 31, 2019, 06:37:19 pmThey are obviously weatherproof. I don't say it's necessarily a good design but they should be fine staying outside.

author: soldar
author_rank: Super Contributor
timestamp: May 31, 2019, 11:20:58 pm
content: Quote from: SparkyFX on May 31, 2019, 11:00:04 pmI find it amazing how overbuilt things were in, say, 1950 when Europe had just come out of the war and there was shortages of everything. Now we mount a mains transformer on a pole outside, exposed to the weather, but I see plenty of brick buildings which were made to house transformers. They are tall, narrow buildings so the high voltage wires would go directly in at the top. There must be thousands of those buildings now abandoned. Probably transformers were made more weatherproof and the buildings are no longer necessary.

author: thm_w
author_rank: Super Contributor
timestamp: May 31, 2019, 11:47:40 pm
content: Quote from: floobydust on May 31, 2019, 06:37:19 pmIt does, compare to Daves system, conductors were properly enclosed in tubing just as would be required for mains.Its hard to tell what sort of voltage would be present though, there are a lot of wires going out but then again a ton of panels too. I think that would be good if it were 48V, but I assume its higher than that.

author: Someone
author_rank: Super Contributor
timestamp: June 01, 2019, 07:10:39 am
content: Quote from: SparkyFX on May 31, 2019, 11:00:04 pmYou guessed correctly, fire brigade like to have an isolation switch on energy supplies as close to the source as practical. But the safety feature is a common failure and can create a fire in the process. The service fuses on the feeds to the house have proven to be acceptable, but the solar installation standards required these switches instead.

author: bdunham7
author_rank: Super Contributor
timestamp: June 01, 2019, 06:31:55 pm
content: Are these high voltage string systems still commonly installed in grid-tied residential systems? I did ours a bit over 6 years ago with microinverters (and all-metal electrical enclosures on exposed parts) and they were beginning to become the preferred method at that time here in California. I would have thought they would be the most common method by now.

author: SparkyFX
author_rank: Frequent Contributor
timestamp: June 02, 2019, 12:46:28 am
content: Quote from: floobydust on May 31, 2019, 06:37:19 pmMaybe it could if it was low voltage, but the panels seem to be in series, which might mean if one breaks the energy generated by the others could end up being dissipated there at the fault? Most regulations refer to voltage, not overall power, and they refer to loads, not generators. There is practically a huge loophole in the regulations - maybe its already fixed or about to be fixed.Some protection features required in mains electrical systems are probably worked around by isolating the system from ground. That might be good that way because it avoids inadvertantly creating a lightning rod (installation on roof) and provides personnel protection from a single failure.Otherwise you´d need a type B/B+ RCD with DC detection, depending on country.QuoteI don´t outright see the problem, other than the durability of the plastics -> or the question if it exposed to direct sunlight.Quote from: soldar on May 31, 2019, 11:20:58 pmMostly because materials and mold making were not as they are today. The whole plastics industry developed later, based on the use of oil. Also you could not form such thin walled objects reliably and in such quantities back then, the whole injection molding process is a late development, requiring automation and a thorough R&D. What they had was a huge work force. Well... today things fail because they were driven too far with too little safety margin.

author: soldar
author_rank: Super Contributor
timestamp: June 02, 2019, 01:19:50 pm
content: Quote from: Circlotron on May 31, 2019, 01:52:07 pmNot to dwell on this but, if I may digress for just a moment, I believe many younger people are not aware that the word "race" has several meanings and does not only mean biological (white, black, etc) race but also, as the dictionary says:QuoteIn Spanish also the word "raza" has the ethnic and cultural connotation and is often used to denote courage or virtue or good qualities. Like in English and due to American influence the word is drifting away from this meaning.There are multitude of examples in English.

author: Nauris
author_rank: Regular Contributor
timestamp: June 02, 2019, 06:15:25 pm
content: Quote from: bdunham7 on June 01, 2019, 06:31:55 pmAt least here nearly everyone uses high voltage string system. Microinverters are just so expensive I think these days one chinese panel is cheaper than one microinverter. String inverters maybe one third the price even german made ones. But I think California is just so full of money it hardly matters there.

author: Siwastaja
author_rank: Super Contributor
timestamp: June 02, 2019, 06:47:48 pm
content: Would have thought that the microinverter price issue would have been solved already as it isn't a new fancy thing anymore, but apparently, no. I was actually thinking about getting into solar power conversion business years ago but decided not to, seeing there's a lot of design effort and a lot of competition to make a mainstream system.From system design viewpoint, it shouldn't be that much more expensive, or even cheaper, but it will take time until the "premium" tag wears off, designs are optimized for low cost, and volumes get there. But usually, in distributed systems, volumes are no problem since each system uses many.

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 02, 2019, 06:54:15 pm
content: There are quite a few Ebay special grid tie inverters, the main problem with them is that (from what I have read) they break all the time. Could probably take one of those designs and figure out how to make it more reliable without increasing the cost too much.

author: bdunham7
author_rank: Super Contributor
timestamp: June 02, 2019, 07:23:18 pm
content: Quote from: Nauris on June 02, 2019, 06:15:25 pmPerhaps, like many other things, they are simply cheaper here. I believe at the time, the specific microinverter I used cost me about $150 per unit, with the solar panels perhaps double that. Now, the exact same microinverter is still available, at $50 per unit. So for 30 panels, new inverters would cost me $1500 and some work. That seems pretty cheap to me, considering you don't need any high voltage wiring, disconnects, etc. And of course, the inherent reliability and self-diagnostics is a huge plus.

author: Vell
author_rank: Contributor
timestamp: June 02, 2019, 08:11:16 pm
content: Regarding anti-Chinese prejudice, I'm glad to see it shamed. The USA's Chinese Exclusion Act is a blot on our history. Perhaps the one thing that's unfortunate about China is its apparent willingness to make cheap, shoddy products if the customer insists on rock-bottom prices. Japan, before WW II, had a terrible reputation for shoddy products. Now, they're top-notch. They learned, and China will, too.I have a couple2of Nikon Coolpix cameras that were made in China, and their quality is superb. One still works fine after two or three drops from handheld height onto concrete and a fall onto it that forced the front section of the telescoping lens badly out of alignment. Its cam follower was forced out of its slot, and snapped back in when I tried. That camera has taken maybe 25,000 shots, roughly. S3100 and L610 for the curious, btw...Quite a few Chinese products I have with switches lead me to think that the Chinese are still learning how to make good switches.Switchcraft apparently had no IP theft!A related topic, which I might post more about later, is the horrible way that many (guessing) factory workers are mistreated.I never forgot about the safety nets between first (British: ground) and second (Brit.: first?) stories, around a multistory factory, perhaps in Taiwan, and iirc Foxconn. These nets protected pedestrians from workers who went out of higher-story windows to commit suicides.Over the past two decades or so, I've kept track of roughly 15 instances of (often hidden) factory sabotage of products made in China (& Taiwan?). I have little doubt that it's revenge by workers who had had it long ago, and just couldn't take it any more.But ... those who sabotaged were very likely to be decent people, simply treated quite badly."couple2"? Idea is that "couple", used to mean two, explicitly; now, it is often casually synonymous with "few". Gets humorous if the new usage refers to a married "couple". Polygamy, anyone? Polyandry?

author: soldar
author_rank: Super Contributor
timestamp: June 02, 2019, 08:20:45 pm
content: Quote from: Vell on June 02, 2019, 08:11:16 pmOh, please! Nets to protect pedestrians from the falling bodies of suicides? Really? You believe this? Can we have some corroboration?I see these nets in Spain all the time and I thought they were for protection from falling debris when they are working on the building and there is danger of falling debris.

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 02, 2019, 08:22:19 pm
content: Quote from: Vell on June 02, 2019, 08:11:16 pmThe rise of Chinese brands like Xiaomi, Oneplus, and Creality show that they are improving. And don't forget all the quality products that are made in China.

author: Vell
author_rank: Contributor
timestamp: June 02, 2019, 08:25:43 pm
content: I do wish I'd kept track of a link. When I read about that, I was rather more gullible; your question has me wondering. I do try hard to post responsibly. It would be generally good if I was suckered. Your skepticism is beneficial.

author: floobydust
author_rank: Super Contributor
timestamp: June 02, 2019, 08:35:42 pm
content: I doubt an isolator will protect a fireman, or this thread from flames. Water spray everywhere at a grounded aluminum frame, there is surely a ground fault from panel/wiring/isolator insulation failure to the water spray and thus the guy holding the nozzle or to the fire truck.Spray a garden hose at 200-400VDC and tell me how that goes. IP54 is a joke for that, COBALTBLACK claims IP66+, assuming the cable glands and panels also meet that.The DC disconnects seem to be mostly failing due to harsh outdoors conditions or shit manufacturing quality, or both. Having safety agency approvals insures they have been tested, instead of a fake claim to be wonderful.

author: Vell
author_rank: Contributor
timestamp: June 02, 2019, 08:42:28 pm
content: Regarding lousy products from Germany, which I hope are far from the norm, Dave Jones opened up a Gossen Metrawatt analog multimeter, and its insides were too makeshift, close to disgraceful. Sorry, but I don't recall how recent that was. He also opened up a Triplett 630 and one of the Simpson 260s. Btw, short-circuit current of the traditional 630 on its lowest resistance range is quite high, and can damage low-power semiconductors.While on the multimeter topic, I briefly owned an Avometer Model 8; decided to void the warranty, and its innards were astonishing. Will try to write it up, sometime. Fine quality, all sorts of different ways of doing things. Real gem was a 1/2 turn winding on the AC range autotransformer.

author: floobydust
author_rank: Super Contributor
timestamp: June 02, 2019, 08:44:18 pm
content: Quote from: soldar on June 02, 2019, 08:20:45 pmOT It wasFoxconnthat installed suicide nets. They are also at various chinese factories.

author: Vell
author_rank: Contributor
timestamp: June 02, 2019, 09:10:04 pm
content: Somewhat off-topic, but I want to thank a member who suggested that this topic should be iirc in General matters. However, it's now into multiple pages, and I'm too new to this Forum to try to move the whole thread. I surely wouldn't mind a tall if some experienced and responsible person did, though. I have yet to read most of the posts.Someone asked how DC has been switched; that has probably been answered, but I'll say what I know about it. A DC arc has a magnetic field, and one stratagem is to have a blowout magnet that forces the arc to lengthen. Long before Alnico, permanent magnets were weak, and demagnetized easily. An electromagnet, the "blowout coil", supplied the field. Pole pieces were on both sides of the arc, as I recall.As well, there were arc suppression chambers, with multiple insulating baffles to split up the arc. This is as I remember, but only from illustrations.The Boston T light-rail Green Line depot at Riverside, its western terminal, had a siding where 3400 series "hangar queens" were stored. Covers had sometimes been removed, and it was quite interesting sometimes to see the goodies, especially electricals. I distinctly recall that what must have been control-circuit relays had huge insulating chambers for their contacts.Off-topic, but also of interest was an air-core power inductor which occupied maybe an 8-inch/20 cm cube, maybe even 12-inch/30 cm. It might have been wound with litz wire, have forgotten.DC for the traction motors must have been modulated by pulse modulation, but quite likely pulse frequency, audio range, instead of width. I recall riding in 3400-series cars, and you could easily hear the "pulser".

author: soldar
author_rank: Super Contributor
timestamp: June 02, 2019, 09:25:01 pm
content: Quote from: floobydust on June 02, 2019, 08:44:18 pmquote Wikipedia:QuoteReading the article it seems to me like a copycat phenomenon where people copy the method they see being used.I don't understand it very well but it seems one guy or guys burn a car or a mailbox and next thing you know other people are doing it.In this case it seems someone jumped out the window and others, who might have committed suicide in other ways, decided to follow suit. But Wikipedia says the overall rate is no worse than in other places.It seems like management thought it prudent to install the nets than have to explain themselves which, in cases like this, is never successful. And the nets would be to save the "suiciders" not pedestrians. I guess once the nets are there you would go commit suicide off company property.At any rate, I have visited some pretty big factories in China and the conditions of the line workers would kill my soul, probably like any assembly line anywhere, but let us not forget that they go there willingly because the alternative is grueling work in the fields; much worse than the factory.Edit:Vell, I want to acknowledge your post had a good factual basis.

author: Vell
author_rank: Contributor
timestamp: June 02, 2019, 09:53:28 pm
content: Quote from: ogden on May 31, 2019, 11:59:12 amThere were lots of messages there; some groups of replies took too long to load, so I ignored them.One reply near the end pointed out that the arc continues because the air is ionized. (Comment didn't mention ionized metal vapor. : )This reminded me of vacuum switches; the contacts are in a vacuum. Afaik, they were (and maybe still are) used to switch high-power RF. Contact gaps are quite small.

author: schmitt trigger
author_rank: Super Contributor
timestamp: June 02, 2019, 11:01:54 pm
content: Vell;I once saw the inside of a control panel for a large DC motor driving a steel mill.I distinctly remember the "blowout coils" in the main contactor.What I don't remember is how these coils were excited, they might have been in series with the current being interrupted.

author: Siwastaja
author_rank: Super Contributor
timestamp: June 03, 2019, 07:34:52 am
content: Quote from: soldar on June 02, 2019, 09:25:01 pmIf this quote is true, it completely discredits the whole thing. Which is, of course, unsurprising.According to the Wikipedia numbers, Foxcon employees killed themselves over 10 times less often than average Chinese people, during theworstyear. This is a huge reduction!Of course, it makes perfect sense - it's to be expected thathaving a workplacereduces depression, stress, and suicide.People really suck in understanding statistical aspects. In a similar way, we totally freak out if 100 people die simultaneously in an airplane accident, but are really comfortable and fine if 10000 people die in car accidents. Similarly, if employees of a massive company kill themselveslessoften than the non-employees of said company, instead of giving them a prize due to reducing suicide, we totally freak out for completely irrational reasons. Again, no one gives a shit if people commit suicides at 100x the Foxconn rate (or 10x the general public rate) if they work in small sweatshops.

author: soldar
author_rank: Super Contributor
timestamp: June 05, 2019, 09:34:45 am
content: The suicide of a person who commits suicide in America would not be linked to the workplace unless they go back to the workplace with a gun and kill a few people first, which happens with appalling regularity.In China, it is customary for factories to provide housing to their workers. So a young girl from the country goes to Shenzhen and applies for a job and the moment she gets a job she has all the infrastructure of her life in place as she has dorm housing and company cafeteria for meals. This arrangement means great flexibility for workers because they don't have to be concerned with finding housing and living arrangements. It is a bit like enrolling in the army. They are ready to work and produce the day they arrive. And they can leave and go elsewhere with no notice and not have to worry about leases, etc.In China any suicide of a factory line worker is going to be on company property because that is where workers live 24/7. The cause of the suicide may have nothing to do with work. It may be depression, it may be family matters, it could be an amorous breakup. I do not think bad working conditions would be a cause for suicide because if a worker is unhappy with working conditions they always have the option of going elsewhere to work or going home. I think suicides are caused by more emotional things and by depression. This is already being discussed in another thread.China has an authoritarian culture everywhere which has a good side and a bad side. I have no doubt that some young girls may face abuse from their supervisors and not know how to deal with it. It is easy to see she can just leave or be firm but young people, especially women, can be easily manipulated and abused.Foxconn made the news because they are big and because they produce for big, well known American companies like Apple and HP which are targeted by Social Justice Warriors. It is not difficult for any group with a cause to spin statistics to support their cause.

author: floobydust
author_rank: Super Contributor
timestamp: June 05, 2019, 11:48:09 pm
content: ‘I personally think that being able to work 996 is a huge blessing ... How do you achieve the success you want without paying extra effort and time?’ Jack Ma

author: Nauris
author_rank: Regular Contributor
timestamp: June 06, 2019, 03:39:59 pm
content: Quote from: bdunham7 on June 02, 2019, 07:23:18 pmNow that is a very cheap price indeed! Here the enphase is like triple price and chinese dual panel inverters only marginally cheaper.But are you sure it is not an SolarEdge system with their per panel optimizers? I think they are quite widely used in USA and about that price.Quote from: Siwastaja on June 02, 2019, 07:23:18 pmString inverter cost is like from 70 to below 30 euros per 285W panel depending on size. It is tought price point for microinverters, especially the lower end. First take the vat off that price then consider it needs some watertight enclosure, some connectors and so on. There is not much money left for actual power electronics. And to the top off that it should last like 15 years at least in a very hot place beneath the panel but above the roof.