51–60 of 64 posts
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So true. I just had two Meanwell PSUs from Amazon delivered and the package was indistinguishable from the usual AliExpress job.
Are you saying they were fake? I've started getting all power electronics from Digikey, Mouser, RS, Pollin etc. because of paranoia over a crap power supply or SSR.
There's a reason retailers have buyers who are experts in their domains and try to buy the best products optimizing for quality/reliability/price. I much prefer to buy things from stores like Target and Lowes now, because I can't rely on any reviews on Amazon anymore. The reviews are all fake.
But this is not true. Work through the screens to get to search mode "all critical reviews", ordered by time.
There's a reason retailers have buyers who are experts in their domains and try to buy the best products optimizing for quality/reliability/price. I much prefer to buy things from stores like Target and Lowes now, because I can't rely on any reviews on Amazon anymore. The reviews are all fake.
But this is not true. Work through the screens to get to search mode "all critical reviews", ordered by time.
Earlier quoted context omitted.
In addition to other things I am certified electrician in Germany. Your claims are wildly oversimplified. Every fuse has a type, rating and trip current. I pick them by planned application, installation type and cable length. Copper cables cost money, the safety margin is THE fuse. Otherwise cable insulation gets too hot and wears too fast.
Is English your native language? You might be confusing fuses with breakers. Fuses aren't typically used to protect copper runs; breakers are. Fuses are used inside of electronics. Breakers are rated as you describe, to protect copper runs. For fuses, this is a data sheet of a random fuse (first one on Digikey search; I didn't pick anything special): https://www.vishay.com/docs/28747/mfuserie.pdf
Earlier quoted context omitted.
Is English your native language? You might be confusing fuses with breakers. Fuses aren't typically used to protect copper runs; breakers are. Fuses are used inside of electronics. Breakers are rated as you describe, to protect copper runs. For fuses, this is a data sheet of a random fuse (first one on Digikey search; I didn't pick anything special): https://www.vishay.com/docs/28747/mfuserie.pdf
The fuses are used in older installations. 25 A 500 V rated fuses are absolutely normal parts. They are usually slower than breakers. Breakers came later. The “normal electrician’s” fuses: https://ep-us.mersen.com/sites/mersen_us/files/2018-11/TM-10...
* A 25A fuse will conduct 52A-110A for 5-10 seconds, which is about the 2x in my original post.
* For shorter time periods, this goes up a lot (150-260A for 100 milliseconds).
I'm getting down-voted, but no one is posting contradictory information. This discussion feels more like reddit than HN.
As a footnote, at least in the US, in the 21st century, I've never seen a house with fuses rather than breakers. As you point out, copper is expensive, and a breaker is $10-$15. It's not only more convenient, but saves more money elsewhere.
For the record: Some of these are a bit over-the-top, and Amazon is trash for anything safety-related, but for the record, virtually all fuses have a pretty significant margin before they blow. The risk here is very limited: - A 2A fuse needs to conduct 2A, no matter ambient temperature, manufacturing variation, age, etc. - 95+% of the time, what you're protecting from isn't a minor overload condition but a short. Th…
> 95+% of the time, what you're protecting from isn't a minor overload condition but a short. But these fuses aren’t labeled “fuses that will blow when there’s a sorry but not when there’s an overload condition”, they’re labeled simply as “fuses”, which should blow over their rated limit, full stop. It violates separation of concerns if I have to think not only about the fuse itself but also the rest of the system th…
It very much doesn't happen much when one is designing analog electronics, which is where fuses come up. If I'm designing a piece of medical equipment, it cannot kill a patient with any single point of failure. That's a systemic design issue, and any device, including a fuse, has to be seen in the context of the system it's plugging into.
It'd be possible to separate concerns, but it would result in grossly inefficient, over-engineered systems.
You do get a bit more of that in electrical (rather than electronics) work, since you need to count on idiot contractors who will screw everything up.
Reminds me how Amazon is fundamentally a logistics company. Their merchandising is basically non-existent. Pretty much indestinguishable from AliExpress + fast shipping.
Isn't Amazon more of a cloud hosting (AWS) company, with some logistics + retail front end on the side?
For the record: Some of these are a bit over-the-top, and Amazon is trash for anything safety-related, but for the record, virtually all fuses have a pretty significant margin before they blow. The risk here is very limited: - A 2A fuse needs to conduct 2A, no matter ambient temperature, manufacturing variation, age, etc. - 95+% of the time, what you're protecting from isn't a minor overload condition but a short. Th…
If your 15A breaker tripped instantly when the current exceeded 15A, you’d be resetting a breaker every time you turned on a stand mixer or something.
Instead they have two mechanisms of action—thermal and electromagnetic.
The thermal trip time varies depending on how much you’ve exceeded the rated current, but for a typical household breaker could be a couple of minutes.
The electromagnetic trip is the “hard cutoff” where as soon as you exceed that limit the breaker trips near instantly. Depending on the type of breaker this is usually 5-10x its rated current. So your 15A breaker may allow you to briefly pull 75-150A through it.
So while these fuses are mislabeled and should not be sold, it’s not as much of a death trap as it might appear on first glance from what it sounds like.
Several years ago I noticed that the motorcycle oil filters I was receiving from Amazon had changed- much lower construction quality, less filtration material, and didn't include a crush washer. I double checked that I was buying the same product on Amazon as previously, and then bought the same SKU from a different store to compare. Apparently, Amazon was mixing counterfeit items in the same stock as the real stuff.…
Why would you buy anything from Amazon after that experience? I personally stopped buying things on Amazon when they gave up on having a trustworthy supply chain.
I am an empathetic fellow. I understand that people are under cost and time pressure. But if you buy a fuse set on Amazon to save $10 off what a fuse assortment kit costs on Digikey, you are getting exactly what you paid for. The signs are obvious: a nonsensical name like HOODOOVOOKOO, sold by BLXXYUSA a seller specializing in children's socks and fuses, quantity listed in "pieces", an obviously cheap plastic box, a…
> You cannot be angry at them for giving you exactly what you want. What they want and were sold is a working fuse... which this is not. If I starting calling myself a medical doctor and advertising cheap surgery I would hope someone would try to stop me. You can't claim to be empathetic and expect everyone to be a domain expert in absolutely everything to avoid getting poisoned, burned or killed by sellers lying to…