[caseymarquis]

After working on high voltage circuits as a lineman for a couple years, and currently writing software for industrial machinery and regularly working in industrial machining cabinets, I think that applying the same level of precaution used for mining to doing minor work on a 100V circuit is being a bit overzealous. To be fair, you're never going to get hurt by being superfluously safe, but at the same time I don't expect my dog is going to flip the circuit breaker on me, so I'm probably not going to resort to LO-TO when doing some minor electrical work when home alone.

[taneq]

Honestly if our mains was 110V rather than "240V" (read 250-260V thanks to all of the rooftop solar in our area) I'd probably be a bit more casual about it. I've been nipped by ~100V from poor earthing and it's not that bad. 240V hurts.

[roenxi]

I've no particular experience working with electricity so maybe you just know what you are doing - but at risk of being a know-it-all on the internet that is not a very safe approach. In an industrial setting any electricity related accident is cause for a trip to the hospital no matter how minor.

For starters you don't want to be casual about 110 volts [0] and for seconds the systems that control heart rhythm use electricity. An electric shock can cause a heart to just stop some hours later (happened to a family friend as far as we can tell).

It is invisible, can kill and humans don't have the right nerves for pain to be an indicator of how bad the damage is. Electricity is hazardous and work on it should leave no scope for surprises.

[0] https://www.asc.ohio-state.edu/physics/p616/safety/fatal_cur...

[kozak]

Can someone please point me to details of a biological mechanism that can cause someone to die hours after having seemingly survived an electric zap just fine? I never thought such things are possible.

[roenxi]

https://www.powerstudies.com/blog/what-does-severe-electrica... .

I'm guessing at the exact mechanism, but I assumed the shock knocks the heart rhythm regulators out of sequence and the body can cope for a while but eventually goes in to cardiac arrest. There is some argument about whether symptoms spontaneously show after 12 hours [www.journalagent.com/travma/pdfs/UTD_18_4_301_305.pdf - linked from said article].

Cells have a bunch of interesting electrical properties - https://en.wikipedia.org/wiki/Electrophysiology . I recall a somewhat humerous story when they discovered electricity. Galvani made a frogs leg twitch and hypothesised something like electricity in the leg. Volta said the idea was bunkum and it was caused by the different metals being used for the experiment. Volta redid the experiment without the frog and someone did Galvani's experiment without the metal so everyone got to be right.

[jfim]

Electrical shocks can cause blood clots (deep vein thrombosis) [1] and rhabdomyolysis [2] due to muscle damage, among other things.

[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3096834/

[2] https://www.merckmanuals.com/home/injuries-and-poisoning/ele...

[joncrane]

Would both of those conditions be asymptomatic between the precipitating event (electric shock) and sudden death hours later?

[aaron695]

Pretty much an urban legend.

Basically it's 'possible' to get cardiac arrhythmias that don't kill you immediately and might kill you later. But not proven, so you're better off learning about not getting zapped than this possibility. Or learning CPR.

https://link.springer.com/article/10.1007/s00392-019-01420-2

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3888927/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2658458/

[JoeAltmaier]

There's a term ambulance drivers use, "Walk, talk and die". For victims of car crashes that got a hard knock to the head. A brain bleed in the brain stem (if I'm remembering it right) will build up pressure until the stem suddenly disconnects.

Not electrical, but such syndromes seem to be real.

[tialaramex]

Walking Ghost phase is a phenomenon in severe exposure to radiation. The patient survives initial ill effects (probably with advanced medical treatment) and now feels fine. They have no nausea, they can walk and talk like anybody else. If you tell them they're actually dying they likely won't believe you. Inside cell reproduction has stopped, and as enough cells naturally die without replacement over the next few days their systems will cease functioning and they'll die of multiple organ failure.

Electricity definitely won't cause that, but yeah, humans can't sense all the terrible things that might have gone wrong with their bodies.

[dreamcompiler]

It's quite real. This is why we try very hard (everything short of kidnapping) to take people to the hospital after a bad car wreck ("high energy mechanism of injury" is the term we use) even if they're walking around saying they're fine.

[kube-system]

Adrenaline is a heck of a thing. I know someone who similarly said they were fine and wanted to go home after being hit by a car. They had fractured vertebrae and their spinal cord would have likely suffered permanent damage if it wasn’t immobilized as soon as it was.

[the-peter]

The EMTs didn't try very hard when I was flipped by a drunk driver. I crawled out of my window and told the EMTs I just wanted to go home and they said 'ok'.

[Cthulhu_]

Yup, definitely - this is why people will be asked if they blacked out, if only for a little while, after a fall. If they did the impact was severe enough to cause damage. And of course tight monitoring after head trauma.

[dreamcompiler]

You're right. When I was young and stupid I did wiring repairs on 110v circuits without bothering to switch them off. I got shocked a lot, but now that I'm older and smarter I know I just got lucky.

[lb1lf]

-During the annual EE safety refresher course I take at work, the instructor makes a point of the fact that during domestic work, the electric shock is often merely the trigger for the real injury; you get zapped, then fall from the ladder you were on or whatever.

(We have 240VAC mains, but I guess an unexpected jolt of 110VAC would be sufficient to make me jump...)

[Klathmon]

I was messing with some DIY generator wiring when I was younger and ended up getting a bite from 110.

My hand was in a shitty position kind of around a table leg, and the shock caused me to clamp down with my hand and kind of "chokehold" the table leg. It took me a lot longer than I thought it would to even register what was happening, and then to kind of throw myself away. I'd been shocked before, but this just kept going after I realized that it was happening and I just didn't know how to process it.

I ended up with some nasty burns on my hand, a really sore whole arm, and a scary realization of how it could have been a lot worse if just one or 2 things were slightly different.

[jjeaff]

110v or 240v will kill you dead where you stand. But it's not really about the voltage. The higher the voltage, the easier it is for the electricity to ground out through you. But it only takes a few milli-amps across the heart to kill you. A household line can deliver 10-20 amps.

Luckily, human skin is not highly conductive and neither are rubber soled shoes.

So if you are taking proper precautions and not kneeling on a wet floor while using all metal tools on bare wires when someone flips a breaker back on, then your risk is rather minimal.

[michaelt]

> 110v or 240v will kill you dead where you stand.

In my experience, when encouraging people to follow safety rules you get better results with true examples that justify the rules than with exaggeration like this. If you tell a person one thing they know isn't true, they're liable to start thinking the other things you tell them aren't true.

240v might kill you if you're up a ladder, elderly, have an undiagnosed health condition, or are just plain unlucky. But it's not the guaranteed instant death that, say a 25kV shock is.

[dsfyu404ed]

>In my experience, when encouraging people to follow safety rules you get better results with true examples that justify the rules than with exaggeration like this. If you tell a person one thing they know isn't true, they're liable to start thinking the other things you tell them aren't true.

As someone who comes from a compliance/human factors background I absolutely hate internet discussions of safety. They are chock full of people exaggerating everything for up-votes/likes/virtue points and while within a given community that may increase compliance it is the exact wrong way to increase compliance from people who are working under a different set of incentives.

[jjeaff]

>guaranteed instant death that, say a 25kV shock is

Also not true.

You can safely hold a metal rod into the air as a 20,000 volt tesla coil fires lightening bolts through the air and into your body then to the ground, because the coil is built in such a way to induce very little amperage across your body.

My point being, it's not just the voltage.

I was just imprecise with my language. What I should have said is "110v or 240v could kill you dead". And that is why the following sentences qualify what I was saying.

Household voltage is plenty to kill you, assuming the factors are aligned.

I have been shocked multiple times with household 110v and it was not pleasant at times and others it was barely a twinge. It all depends on how well you are grounded.

I had a very unpleasant shock once from a 12v car battery because I was sitting on the ground in shorts and fiddling with it somehow.

[ttsda]

It's impossible for a 240V outlet to deliver 10A through your body. Unless you're made of metal or something.

[jjeaff]

But you don't need 10Amps to kill you. Just a few hundred milli-amps is enough to kill a human.

[duckymcduckface]

Think the point is that the voltage won't collapse under the load.

[taneq]

Exactly, you can get zapped by tens of thousands of volts from a van de Graf generator and be fine, and you can die from 110V mains. The difference is the importance of the supply.

[LeifCarrotson]

I was working with a circular saw and extension cord on a ladder in light rain Monday night (gotta get that roof up before snow settles in!) and got a moderately bad hit of 110. I didn't drop dead where I stood nor was I thrown off the ladder. Don't exaggerate.

I did retire the extension cord, though.

[jjeaff]

You misunderstand my comment. And you misunderstand how electricity works. Had you been well grounded, you could have easily died. It only takes about 200 milliamps to kill a human.

110v/10amps is plenty to kill you. It's not the voltage that kills you, it's the amps. That is why you can touch a 20,000 volt tesla coil and barely feel a tingle.

[6nf]

> But it only takes a few milli-amps across the heart to kill you. A household line can deliver 10-20 amps.

10-20 amps? Not across your skin!

Usually a 220V zap at home won't cause instant death.

[wlesieutre]

That's the point made in the line after your quote

> Luckily, human skin is not highly conductive and neither are rubber soled shoes.

Could also note that depending on your circuit breakers, a short circuit will continue delivering higher than its 20A rated capacity for some time until the overcurrent protection goes off.

Thermal breakers won't react as quickly to overcurrent as thermal magnetic breakers, so it depends on what kind of protective equipment is installed.

EDIT: some reference on circuit breakers https://www.se.com/ww/resources/sites/SCHNEIDER_ELECTRIC/con...

> For example: based on the curve on page 3, an iC60 circuit breaker of curve C, 20 A rating, will interrupt a current of 100 A (5 times the rated current In) in: 0.45 seconds at least, 6 seconds at most.

6 seconds is a pretty good chunk of time for a 20A circuit to happily be delivering 100A of current.

[jjeaff]

You should read the whole comment before contradicting someone. It really wasn't that long of a post.

[unlinked_dll]

I've gotten burned by changing light bulbs without turning off the switch; garnering me the nickname "Uncle Fester" by my family (in my defense - the light bulb was out and I wasn't thinking) and that shit definitely hurts.

I've also been burned debugging a power supply for a GSM amplifier used in the test harnesses for a semiconductor fab (this time was carelessness, the power supply rails weren't taped off since I was probing it attempting to find a fault on the point-to-point wiring) that was powered at 240V and holy hell I do not recommend doing anything that stupid. If it doesn't have a safe way to repair, buy a new one.

[taneq]

Burned or zapped? Light bulbs get thermally hot but glass is non-conductive.

I haven't personally been bitten by 240V but from people I've talked to who have, I don't intend to chance it happening.

[Qwertystop]

I'd guess you could get zapped if you accidentally touch the metal part of the bulb (or the socket) while unscrewing the old one or screwing in the new one.

[grawprog]

I dunno, I got electrocuted repeatedly a few weeks ago, not sure the voltage, I was using a wet saw and didn't realize the rubber had worn out on my boots and the steel plate in the soles was touching the floor. Every time I turned the saw on or touched it when it was running I got electrocuted. It was kind of funny, nobody could figure out why i was the only one being electrocuted. All my coworkers came and touched it and were fine. But, it wasn't the pain that got to me, it was the weird feeling in my body after.

All the rest of that day I felt weird. My skin felt too sensitive, my arms would twitch randomly, and I just felt kind of weak and vaguely dizzy all day. I did end up figuring it out and putting a rubber mat down which immediately stopped the electrocution problem. But I really don't like being electrocuted at all. It just isn't pleasant.

On topic, all our machines get locked and tagged before opening the electrical cabinets or working on anything where you might be exposed to live wires. It's enforced by worker's comp also. We get randomly inspected fairly regularly and one thing they check is that we have lockout keys and locks on every machine breaker.

[tomatotomato37]

I find it interesting how you describe a job with a functional safety culture from the perspective of regulators, with lockouts and random inspections, that yet solves the issue of a power tool shocking workers at mains voltage by just tossing down a rubber mat and continuing to work with said malfunctioning tool.