Lots of recalls of solar panel DC disconnect switches

[Nauris]

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.

At 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.

[Siwastaja]

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.

[NiHaoMike]

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.

[bdunham7]

At 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.

Perhaps, 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. 

[Vell]

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 couple² of 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?

[soldar]

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.

Oh, 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.

[NiHaoMike]

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.

The 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.

[Vell]

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. 

[floobydust]

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.

[Vell]

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.

[floobydust]

Oh, please! Nets to protect pedestrians from the falling bodies of suicides? Really? You believe this? Can we have some corroboration?

OT It was Foxconn that installed suicide nets. They are also at various chinese factories.

[Vell]

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".

[soldar]

Oh, please! Nets to protect pedestrians from the falling bodies of suicides? Really? You believe this? Can we have some corroboration?

OT It was Foxconn that installed suicide nets. They are also at various chinese factories.

quote Wikipedia:

although the number of workplace suicides at Foxconn is large in absolute terms, the suicide rate is actually lower when compared to the overall suicide rate of China[33] or the United States.[34]

Reading 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.

[Vell]

Because 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.

Topic 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

There 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.

[schmitt trigger]

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.

[Siwastaja]

Wikipedia:

although the number of workplace suicides at Foxconn is large in absolute terms, the suicide rate is actually lower when compared to the overall suicide rate of China[33] or the United States.[34]

If 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 the worst year. This is a huge reduction!

Of course, it makes perfect sense - it's to be expected that having a workplace reduces 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 themselves less often 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.

[soldar]

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.

[floobydust]

‘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 

[Nauris]

Perhaps, 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.

Now 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.

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.

String 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.