Electronics > Projects, Designs, and Technical Stuff

Lots of recalls of solar panel DC disconnect switches

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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  :palm: 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  :o

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”?

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