Comments URL: https://news.ycombinator.com/item?id=50194686

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Obviously, there are also some people in cybersecurity who oversell not for the greater good, but only to further their careers... and even those who are honest and would prefer not to self-promote like that, are sort of forced to, because visibility can matter as much (if not more than) expertise when trying to find a job in cybersecurity, as you'll look like an underachiever if you don't oversell yourself like everybody else.

Ground does not protect against every shock hazard! Devices can fail in many ways where live parts are exposed without contacting the grounded casing. Also, imagine a little child poking a metal stick into the outlet. Now you'd better hope that outlet has GFCI. Modern code does not call for it in a child's bedroom, does it?

Edit: To be fair, modern receptacles should be tamper-resistant, but then imagine a child reaching into a lightbulb socket, or cutting through a wire, or the insulation on a wire becoming damaged, etc. pp.

> for all practical purposes you almost do have [GFCI] on every circuit

But there are still gaps! I got shocked by an old clothes iron once (and I'm glad it tripped the RCD at the panel). Bedrooms and living rooms can have electrical faults too!

Another advantage of RCD at the panel is that it protects all downstream parts of the panel and all circuit wiring too! A lot of fatalities come from people working on live wiring. (In fact, many electrocution deaths are electrical contractors.) Now sure, they almost certainly weren't following correct safety procedures, but still, a lot of them could have been saved by an RCD. Some people probably die changing their light bulbs. That's preventable by installing an RCD at the panel, so that the entire circuit is protected, not just everything plugged into a GFCI outlet.

> To me seems like people are hating on a pretty great system. [...] localized fault detection [...] would seem like an advancement

I agree that localized fault detection, all else being equal, is an advancement. But if it comes at the cost of no GFCI protection at all on other circuits, I'm not sure it's worth the tradeoff.

Hundreds of people in the US die every year from low voltage electrical shocks. This number used to be a lot higher before GFCI was common, but it likely could be lower still if GFCI was required everywhere.

Obviously it would be best to have broad coverage and localized tripping, but if I had to pick one, I'd choose broad coverage. Calling it "going backwards" misses the concern of how much is protected, rather than just how localized the impact is when there is a fault.

The difference between one three-phase feeder and three completely separate two-wire circuits is that the three phases, which are 120° apart, share a single neutral conductor. In fact, if the load is perfectly balanced across the phases and currents are sine waves, they will cancel each other out, so neutral will carry no current at all and can be omitted! But in practice, there still usually is a neutral conductor to carry the imbalance (except for specific loads like delta and star motors under certain conditions). In total, we only need 4 wires instead of 6 to carry the same amount of power. That's 1/3 less copper! (Excluding PE of course.)

Now, compared to using a single two-wire circuit rated for three times the current, three-phase also wins by a long shot. (We're again assuming a balanced load and equal power factors.) This is because resistive heat scales with the current squared, so 3 times the current produces 9 times the amount of heat at the same resistance. So, we need to use thicker conductors to lower the resistance. But the area of its cross-section grows quicker than the surface area to dissipate heat, so the maximum current a conductor can safely carry scales sublinearly with its cross-sectional area. For example, 1.5mm² will suffice under most conditions to carry 16A, but for 48A we'll typically need 10mm².

All in all, the rule of thumb is that three-phase AC gets you the same amount of power for roughly 25% less copper compared to single-phase AC!

Some loads also make use of the rotating magnetic field, like motors (see below).

Lastly, lower currents will reduce heating in case of loose connections, reducing the risk of fire. On the other hand, a 400V RMS phase-to-phase shock is a lot more severe than a 230V RMS phase-to-neutral (or phase-to-PE) shock.

Common use cases (load-side):

- Motors. Three phases produce a rotating magnetic field, perfect for simple self-starting motors. (Arguably, this is less relevant today with more modern motor designs, though three-phase induction motors are still widely used.)

- Electric cookers (usually split by cooking zones and oven, like one phase for two zones each, and the third phase for the oven)

- Water heaters (especially those that heat water instantaneously on demand)

- EV charging (even an ancient European three-phase installation is likely able to deliver 11kW of power and can therefore fully charge an EV overnight)

> Curious why you’d need/want whole home gfi

Because the danger they protect against is not confined to bathrooms and the outdoors!

An RCD (GFCI) trips quickly when there is an imbalance between outgoing and returning current exceeding a certain threshold, indicating that some current is likely leaking to earth. A little more than 30mA AC through the body sustained for a couple of seconds can kill someone, but is not enough to trip a regular circuit breaker!

Wetness increases conductivity and therefore the risk of a dangerous electric shock, but a faulty appliance or damaged cable elsewhere exposing you to mains voltage can be life-threatening too!

So, why shouldn't we protect the entire house?

> I'm assuming [...] if there’s a short on any circuit power to the entire house is cut

Small nitpick: a GFCI/RCD doesn't trip because of a line-to-neutral short circuit, it only trips if some current "escapes" to somewhere else. Though it is true that nowadays we often install RCBOs which combine residual-current, overload, and short-circuit protection.

But your concern about nuisance trips is somewhat justified. If there is really only one RCD serving the entire house, which is very common for older installations, a ground fault will cause a larger outage.

Newer installations, however, typically use multiple RCBOs to reduce the blast radius. And really old installations, where small current leaks are more common, might not have an RCD anyway.

Also, in my experience, it's just not a problem in practice. I can count the number of nuisance RCD trips I've had in my life on one hand. And genuine faults are similarly rare. Other kinds of power outages are far more common.

> GFI outlets provide a very localized layer of safety [...] can be extraordinarily sensitive

I fully agree that this is an advantage.

A standard 30mA RCD or RCBO, as would be installed in Europe, should disconnect within 40ms at 150mA, but might take longer at lower currents. That could still be quite a substantial electrical shock. (I'm not qualified to say exactly how dangerous it still is, but I can attest to the fact that it can still hurt pretty bad even if the RCD trips.) A 5mA GFCI, as is typical in the US, provides a much larger safety margin. I guess nuisance trips would be a much bigger problem if the detection threshold for RCDs was lowered to 5mA.

So maybe we can agree that the perfect solution would be to have GFCI outlets everywhere? Because as it stands, you either have crude protection everywhere, or good protection limited to a few outlets.

One last note: Whether you have GFCI outlets or RCDs in your electrical panel, make sure to test them regularly via the test button! A faulty protection is no protection, and it's better to be safe than sorry.

Edit: One more thing worth keeping in mind is that, all else being equal, 230V drives almost twice the current as 120V, making the shock more dangerous and residual-current protection even more important.

Would genuinely recommend this game to everybody!

Comments URL: https://news.ycombinator.com/item?id=50004220

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If you want more information: https://www.erc.edu/media/p5ymaeej/gl2025_layperson_book_ipd...

I agree, and that's why a city shouldn't look perfectly spotless. A little weathering here, some extra foliage there, a bit of dirt on the street, etc... These details send exactly the right signal: A real city that feels lived in. Not artificial, not abandoned either, but a lively middleground.

> Will I be able to tell the difference between ‘weathered’ and ‘abandoned’?

Artistic nuance is required to find the right balance, of course. But, imo, abandoned buildings in Cities Skylines already stand out enough, not just because of the icon, but also because they're much darker in color. That leaves enough room to make regular buildings look a little more worn without blurring the distinction.

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