Lots of recalls of solar panel DC disconnect switches

[Vell]

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.

[floobydust]

There's many different ways a disconnect can fail.  Faulty contacts, faulty operator.
Notice some have only CE stickers on them  no 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.pdf
this switch mechanically fails and looks off but is on 

[wasyoungonce]

Pretty sure most isolators come from China....which explains everything.

I’m going to check my isolators ...


Sent using iPhone

[floobydust]

The NHP isolator uses Katko from 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!

[AndersJ]

How do solar panel DC disconnect switches differ from other switches?
Why is this a topic here, emphasizing ”solar panel DC disconnect”?

[nctnico]

How do solar panel DC disconnect switches differ from other switches?
Why is this a topic here, emphasizing ”solar panel DC disconnect”?

Interrupting 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.

[Siwastaja]

Pretty sure most isolators come from China....which explains everything.

Unnecessary, 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.

[wasyoungonce]

Pretty sure most isolators come from China....which explains everything.

Unnecessary, rasist, and plainly wrong.   ...Most high-quality, safe things come from China as well as the dangerous crap.

Look 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!   

[soldar]

Pretty sure most isolators come from China....which explains everything. 

What 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.

[soldar]

Could it be that present-day switch designers don't realize that interrupting considerable DC power creates an arc, unless contacts part quickly? 

I 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?

[mikerj]

How do solar panel DC disconnect switches differ from other switches?
Why is this a topic here, emphasizing ”solar panel DC disconnect”?

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.

https://www.eevblog.com/forum/blog/eevblog-1217-my-home-solar-power-system-failed!/

[ogden]

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

[mikerj]

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

Fair 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.

[Circlotron]

Pretty sure most isolators come from China....which explains everything.

Unnecessary, rasist, and plainly wrong.

I think the statement is nationalist, not racist.
Condemning Asian people rather than the Chinese nation would be racist.

[floobydust]

... here in Finland total shit gets designed and/or produced.

This looks like a cowboy installation, from the Katko website. 390 panels 100kW.
The panels and PVM disconnects with just loose wires in a homemade sheet metal box 
Rain 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.

[Siwastaja]

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-Aliexpress safety 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 this wind-interrupted power distribution system, so it's completely logical to make sure the wind affects solar production directly, as well! 

[soldar]

I think the statement is nationalist, not racist.
Condemning Asian people rather than the Chinese nation would be racist.

It is still unacceptable.

[SparkyFX]

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.

[wraper]

This looks like a cowboy installation, from the Katko website. 390 panels 100kW.
The panels and PVM disconnects with just loose wires in a homemade sheet metal box 
Rain 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?

They are obviously weatherproof. I don't say it's necessarily a good design but they should be fine staying outside.

[soldar]

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.

I 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.

[thm_w]

Solar electrical equipment somehow can ignore mains electrical safety standards.
Approvals are required on components, wire, boxes etc. but this install looks hokey.

It 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.

[Someone]

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.

You 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.

[bdunham7]

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. 

[SparkyFX]

Solar electrical equipment somehow can ignore mains electrical safety standards.

Maybe 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.

Approvals are required on components, wire, boxes etc. but this install looks hokey.

I don´t outright see the problem, other than the durability of the plastics -> or the question if it exposed to direct sunlight.

I 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.

Mostly 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.

[soldar]

I think the statement is nationalist, not racist.
Condemning Asian people rather than the Chinese nation would be racist.

Not 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:

a group of people sharing the same culture, history, language, etc.; an ethnic group.
"we Scots were a bloodthirsty race then"

In 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.