Quotes of the week: Theo de Raadt
Quotes of the week: Theo de Raadt
Posted Feb 10, 2024 20:08 UTC (Sat) by pizza (subscriber, #46)In reply to: Quotes of the week: Theo de Raadt by Wol
Parent article: Quotes of the week
There's more than one way to skin the proverbial cat.
In the US, what you described would be a violation of the National Electric Code. The circuit breaker must be sized for the lowest-rated portion of the circuit. Even if the wiring can handle 50A, if the socket(s) can only handle 15A, the breaker for that circuit must be no greater than 15A.
(This means that if two loads on the same circuit try to suck down 10A each, while that's fine from each socket's perspective, it's going to to pop your 15A breaker.)
Additionally, high-amperage circuits (water heater, HVAC, etc) are usually required to be dedicated to a single load.
> Which is cheaper, a couple of fuses at a couple of pennies each, or a hundred quid for another drum of cable (or more)?
At my local hardware store, 10/2 (30A) wire is nearly 3x the price of 14/2 (15A) wire ($0.92/ft vs $0.32/ft). So it's considerably cheaper to run two 15A circuits instead of one 30A.
Posted Feb 10, 2024 20:21 UTC (Sat)
by pizza (subscriber, #46)
[Link]
I should also point out that in the US, higher-amperage/voltage (>20A, >120V) plugs and sockets are physically incompatible with lower-amperage/voltage (<= 15A, 120V) ones. So you are physically prevented from plugging something only capable of safely handling 10A into a socket capable of delivering 30A.
Of course, nothing prevents you from buying a 240V 30A plug, using 26AWG (<2A) to connect a 120V electric kettle and setting your house on fire, but at that point it's darwinism.
Posted Feb 10, 2024 21:17 UTC (Sat)
by Wol (subscriber, #4433)
[Link] (8 responses)
Different code, same purpose. Don't forget we have a ring, so we're delivering 30Amps over two (I think it's) 20Amp wires. So the socket will be designed to cope with 15Amps coming in either side, and delivering 13Amps to the socket. In fact, I think single sockets are designed to the same standard as doubles, so the socket has to be capable of delivering 26Amps.
Although I get your point - what happens if the ring gets broken? I don't actually know.
> At my local hardware store, 10/2 (30A) wire is nearly 3x the price of 14/2 (15A) wire ($0.92/ft vs $0.32/ft). So it's considerably cheaper to run two 15A circuits instead of one 30A.
So a 30Amp ring will cost roughly one third the price of a 30Amp spur. And I can have 2 x 3KW heaters in my room compared to your one if you have a 15Amp spur :-) At a cost almost identical to yours. Why I would want two 3KW heaters I have no idea :-)
Cheers,
Posted Feb 11, 2024 8:59 UTC (Sun)
by khim (subscriber, #9252)
[Link] (7 responses)
Sorry, but no. Different code, different purposes. Yes. That allows you to save some metal. And allows you to make things cheaper. But, in turn, that mean more points of failure. Which means less reliable protection and more chances of fatal failure. That means that UK have cheap and convenient yet dangerous setup. That's simple logic. And then you start preaching safety and when I become surprised you explode and, again, explain how you have convenient yet more dangerous setup. Because I'm not even sure what we are discussing here. Just what people are trying to tell me when they say you should really really educate yourself about how energy distribution works? I know how energy distribution works, but I also know how it fails. Fires happen not when protectors work but when they fail. Fuse doesn't blow up when it should (often because someone become tired of replacing it all the time and user piece of wire instead of fuse) or protector doesn't disconnect what it supposed to disconnect. And wire designed for 5A received 16A or wire designed for 16A received 60A. Then it overheats and burns. Now, there are, basically, two ways of designing things: “UK” and “everyone else”. UK way is to use thin wires and then put fuses everywhere to proctect them. That's convenient, cheap, complicated and dangerous design. Because these fuses are very much needed there and if any if them will not work and wouldn't break connection in danger you risk damage, including, but not limited to fire damage. “Everyone else” uses approach that's less convenient, more expensive, but simple and safe. Thick wires everywhere means there are less points of failure and less points of failure means more safety overral. Now, you may argue your preference for convenience or your preference for safety, but it's just stupid to praise safety if you have cheap and convenient, but dangerous setup, don't you think? Now, about practicality: “everyone else” approach doesn't preclude you to add more fuses if you wish. E.g. you may have connector to your garage which includes fuse and thus prevents your house from being powered-off after raid. But, and that's critical difference, that't convenience fuse, if it fails you are still safe. You house would be disconnected yet it wouldn't burn, because the main fuse would protect you.
Posted Feb 11, 2024 9:25 UTC (Sun)
by mgb (guest, #3226)
[Link] (5 responses)
¯\_(ツ)_/¯
P.S. Unlike US breakers, UK fuses do not sometimes fail to blow when overloaded - too much current through a thin wire vaporizes it reliably, quickly, and safely. However replacing a blown fuse takes a couple of minutes longer than flipping a tripped breaker.
Posted Feb 11, 2024 10:09 UTC (Sun)
by khim (subscriber, #9252)
[Link] (1 responses)
If no one ever mixes them up, no one puts some piece of wire “to make the damn thing work, because I need it now” and so on. Well, maybe UK citizens are living in a different universe and they never make any mistakes, but then why do they need these fuses in the first place? I don't even use ani-virus (except what Microsoft shoves down my throat) and I don't see the point of it (that abomination Microsoft calls protector only ever acts on me when I compile programs with non-standard settings and I've never seen it acting upon real threat). But it's like “convenience fuse” on the extender in non-UK setup: it may help you if you are not careful enough, but if you built your whole security system on the assumption that anti-virus never fails and always protects you… then you are doing it wrong.
Posted Feb 11, 2024 12:24 UTC (Sun)
by mgb (guest, #3226)
[Link]
Oddly enough, since this is LWN, I don't have Microsoft pushing anything on me - none of our laptops, servers, or virtual servers run Windows.
Posted Feb 11, 2024 14:57 UTC (Sun)
by pizza (subscriber, #46)
[Link] (1 responses)
...Have look at some of Loius Rossman's rants on fuses that aren't what they claim to be. If you think UK plugs aren't full of similarly dodgy fuses then I have a bridge in London to sell you...
FWIW I grew up in a place that used UK-style fused plugs (on radial, not ring circuits), and have personally witnessed plenty of fuses/plugs/sockets that *melted* but didn't blow, only "failing" when something melted to the point where the contacts no longer contacted, or causing a short that tripped the upstream breaker/fuse.
So personally, I place far more trust in dual-action circuit breakers [1] than fuses.
[1] A thermal component that trips if the sustained current is too high for too long, and a magnetic component that trips if the current suddenly spikes. Then there are the Ground Fault and Arc Fault breakers that add additional protections.
Posted Feb 11, 2024 16:47 UTC (Sun)
by Wol (subscriber, #4433)
[Link]
You'd be surprised then ...
Okay, from what you've said about dodgy Chinese suppliers, you could be right, but your typical UK plug nowadays is a sealed unit where if the fuse blows you just replace the cable. Your typical UK consumer today wouldn't have a clue how to cut off and replace a moulded plug. Even where you can replace the fuse, they wouldn't have a clue how to do that!
(And we did have a bridge in London we sold to you :-)
Cheers,
Posted Feb 11, 2024 17:11 UTC (Sun)
by farnz (subscriber, #17727)
[Link]
UK fuses also fail to blow when overload - too much current through a thin wire heats it, yes, but it does not always vaporise; and even when it does vaporise, it can do so by coating "non-conductive" parts of the fuse in metal, resulting in the fuse carrying more current than it was designed to do (since the new coating is shorter and thus thicker than the wire was).
Both of these are rare failure modes, but they exist; there's a reason why BS 7671 now recommends breakers over fuses, because breakers (when well-constructed) are more reliable than fuses.
Posted Feb 11, 2024 10:27 UTC (Sun)
by mb (subscriber, #50428)
[Link]
No.
Quotes of the week: Theo de Raadt
Quotes of the week: Theo de Raadt
Wol
> Different code, same purpose.
Quotes of the week: Theo de Raadt
Quotes of the week: Theo de Raadt
> Unlike US breakers, UK fuses do not sometimes fail to blow when overloaded - too much current through a thin wire vaporizes it reliably, quickly, and safely.
Quotes of the week: Theo de Raadt
Quotes of the week: Theo de Raadt
Quotes of the week: Theo de Raadt
Quotes of the week: Theo de Raadt
Wol
Quotes of the week: Theo de Raadt
Quotes of the week: Theo de Raadt
Can you please stop it? Thanks.