We use 240v.
Iâm guessing a GPO is a âgeneral purpose outletâ or something like that? Itâs not familiar to me. Wikipedia says an RCD is what we call a ground fault interuptor or GFCI.
A 30 amp breaker feeding outlets rated for 10 amps would be seriously illegal anywhere in the USA. The only similar situation allowed by the US NEC (National Electric Code, not actually national but nearly so) is a 20 amp breaker used with multiple 15 amp receptacles. The wiring still has to be rated at 20 amps.
Anyway, 240VAC at 30A is 7200 watts! Yikes!
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Holy crap, you should seriously stop that. If you have any path to ground and hit the hot line you will die. 120V is more than enough to kill a person from the hot. The main reason youâve been okay so far is youâve been lucky and not been grounded. All it takes is one accidental touch of a nail or doorknob or conduit, something you may not even see, and you can die.
Household mains in both Europe and the US are split-phase and grounded in the middle (240V in the US and 480V in Europe, the split halves the voltage to each side and gives you the two phases (this is why X10 can be a pain in the ass in some houses)). The grounded end is the neutral, so it effectively is at 0V (the path to ground is already established for neutral). The hot is where the danger is.
I see you looked up Wattâs law, but thatâs not important here; we want Ohmâs law, because as you may have heard: itâs not voltage that kills, itâs current. 0.1mA across the heart will cause your heart to stop and a few hundred mA through the skin will heat it to cause third degree burns. Ohmâs law solved for current is I = V/R, and thatâs what we want to use here.
This leads to the question, what is the resistance of skin and human tissue? Tissue is non-Ohmic, so we canât just assign one value to it and go from there (this is also why you never find one source out there saying that itâs x, all depends on how you measure), itâs resistance goes down as voltage goes up; but an approximation can be at voltages below 45V itâs about 1M Ohm, about 2k Ohms at 120V and probably about 1k Ohms at 240V. If youâre sweaty at all your resistance can then go down to a half of that all the way down to a tenth, depending on the salt content and quantities of moisture. Another factor is thickness of skin, if your skin is thin or the contact is over thin part of your skin, thatâll cause the resistance to go down.
Taking that 2k Ohm figure, we get that if you complete a circuit to ground with 120V youâll have 60mA. This can kill you if enough current goes across your heart.
Please, please stop touching the mains and invest in a live wire pen, they are cheap and you wonât have to do this silly and potentially deadly practice.
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Iâve got no problem blaming the USB charger here. From what it sounds like, she had a metal cased laptop and the earphones leading to an iPhone with one of these knockoff bargain bin chargers. If you watch this video: https://www.youtube.com/watch?v=wi-b9k-0KfE Dave will take you through one of these chargers and how many bad points they have. They can easily leak mains due to shoddy construction, tin whiskers, faulty design (Iâve seen some chargers out there that have a design that actually leaks mains into the circuit, YIKES) and that leaked mains can easily jump through a person to a well-grounded metal-framed laptop. By contrast if you look at the Apple design here http://www.righto.com/2012/05/apple-iphone-charger-teardown-quality.html itâs got a lot more protection, and a much more advanced circuit. I donât expect anyone to understand them, but the first design is a shoddy sub-standard switching design while the second is an advanced modern one.
Iâm with the consumer protection agencies here; if youâve bought cheap chargers, destroy them and dispose of them and replace them with a genuine Apple, Samsung, LG, HP (the old Touchpad ones are the best USB chargers Iâve ever had! (And this is coming from someone who was screwed out of a job from HP!)), or some other major name brand. I want to check one of these days, but I think the monoprice ones are okay too.
Donât give these assholes who design shoddy power equipment any of your money, and keep yourself safe.
I heard it is a combination of current and energy. Different sources say 10-30 milliamps, and 10-50 joules. (Probably current through body, which acts as a distributed resistor/impedance network, so the through-heart-itself current is âdilutedâ, not through the heart itself as of electrodes stuck right there?)
A short pulse of high current with insufficient total energy wonât do much else than being mildly to seriously unpleasant (camera flash caps, I am looking at YOU!, these bitches can stay charged for over a day with battery removed, and in some models start charging immediately after battery is inserted; talk about an antirepairman mine). Same for long exposition to below-the-limit current.
Not THAT deadly if you know what you are doing. The muscles under power will contract, and as the bending ones are stronger than the straightening ones the limb under current will bend. (Which also means if you hold the thing thatâs live, you will grip it strongly and could not let it go. Nasty.) Touching with a tip of a straightened finger will let the finger automatically push away. Not being connected to ground helps a lot safety-wise; you want to stack the saving roll bonuses here.
I use the neon bulb tester (even made one for my keychain, from a piece of transparent-plastic pen and some jewel-grade clear potting resin), but before touching the wiring with bare hands I always do the fingertip test in addition. Just to be sure; any instruments can fail. And if you are aware about the presence of live power, and know what you are doing (train on powered-down circuitry first!), you can fairly safely work on energized equipment. But be very aware of what you are doing, what you will do next, and take a break if things do not go as planned (e.g. if a wire does not want to go under a clamp). And be prepared for surprises, so you wonât jerk in a way to get you into further contact with mains or fall off a ladder. And donât be cocky; Murphy is always looking over your shoulder.
I appreciate your concern for my welfare, but if I wasnât purposely grounding myself, how would I know the line was hot? And donât worry, I understand about the sweat issue, thatâs why I use a dry fingertip. Iâve touched 120 VAC hots hundreds of times, and Iâm not dead yet, at least as far as I know.
#I DO NOT ADVOCATE OTHER PEOPLE DO THIS. YOU COULD DIE.
But personally I do it all the time, whenever Iâm feeling too lazy to fetch a meter. 120vac at 60Hz just doesnât bother me much (I do take pains to make sure it doesnât go directly through my heart or brain tissue, of course). 240 hurts like the very devil, though!
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I used to work construction in London. One day I watched a 6â3" man clip off a sconce wire after he had been assured the power was cut. It wasnât. The shock threw him across the room, where he hit the far wall and crumpled to the ground. He made it, but didnât work for a while after that.
220-240V DC is nothing to sneeze at. We in the U.S. are soft, soft I tell you.
I got a number of kicks from 230V, with various degrees of being grounded, and they werenât pleasant at all. Obviously I survived them all. But some were outright nasty.
The most unexpected one was at friendâs place in an old building. Oddly enough I was not working on mains power but doing manual editing of a crapped out bootsector of a computer. When I saw it will take more time, I rested with my feet on the warm (and grounded) radiator, took the keyboard to put it in my lap, and - ZZZAP!, and I had one. Took a cup of hot tea to recover. Turned out that the keyboard had metal bottom that was grounded to the computerâs chassis, the house had old wiring, the ground pin was (according to rules for old wiring) connected to the neutral terminal, and the neutral and live were swapped in the circuitbreaker box.
Another one was self-inflicted but in an insidious way. I was working on a simple circuit, connected on the front terminals of a current limiter device. Wiring exposed. And it did not want to work; part of the function was a capacitance coupling from the live wire. I was putzing around for long enough to touch the ground pin on the back socket with one hand (DUMB!) and the capacitance terminal on the other side (and it did not work), then brushing a finger over the N-connected wire - KER-ZAP!, that one was bad. Turned out that the L and N terminals were swapped. Later it turned out that they werenât swapped in the limiter device but in one of the power strips. Which had power cord from a remain of a computer power cord, with the IEC plug cut off. And the Chinaman swapped the brown and blue wire in the cable, and several years before when I was making the extension I foolishly trusted the colors. The next day the current limiter got a switch for L/N swap on the back, a ground clamp on the front, and two neon bulbs on the front L/N terminals to indicate which one is L.
The third story is not a real âkickerâ but illustrates what can happen and bring danger later. When installing computers in a new office, I felt the chassis a bit âroughâ despite being smooth metal. That feeling is a telltale for power leakage. I whipped out the neon tester and sure, it was glowing, albeit half-heartedly. A digital multimeter shown 60 volts between N and GND, with GND being active. In multiple sockets. Which is Wrong. We called the building manager. After making him believe by handing him the neon tester for a while, he called ârealâ electricians. Who had to borrow my multimeter as their own meter was low-impedance and did not show any voltage on GND (so leakage through capacitances was confirmed); after a while of clowning around they found a broken GND wire in one socket hidden behind a cabinet, which made the rest of the string ungrounded, and making all the chassis of the computers potentially lethal if there was a single L to GND short later.
Power wiring is fun!
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=8-O
Yikes!
Was not that bad. The guy from your example was likely clutching the wire cutters, and got a fairly low-resistance current path through him, and was unable to let go nor did the muscle contractions get him away (like it happened to me). I got just intense âBUZZ!â localized to one or both arms, and that was it. (Capacitors are somewhat similar but the buzz has a different quality/feel. Unpleasant as well. But they can also kill, sometimes with couple hours delay if you manage to get a blood clot that gets loose later and cause an embolia.) And my antics are more survivable by having annoyingly dry skin (so even those old skin-resistance âsensorâ switches ignore me until I lick my fingertip).
Trying to locate a link about delayed death after getting kicked by a capacitor (friendâs classmate succumbed to that decades ago) I found this high voltage safety manual that has some numbers about what human body can cope with, and tables of effects.
As capacitors are little bitches eager to bite you just when you get accustomed to them, my designs often involve of a pair of yellow-colored and easily accessible header pins in parallel to discharge them with a screwdriver before getting in. Higher voltage/energy stuff deserves those $3 or so for a relay and a bleed resistor that keeps the cap discharged and shorted when the equipment is opened, and optionally a neon bulb and a resistor to indicate presence of HV. (Or indicate the presence of AC, and can be located inside the enclosure; some motherboards have a LED on them to indicate the presence of standby power to alert the technicians that they can shortcircuit and burn stuff, this is the same for 230V AC designs. I love my indicator lights, even if others sometimes call it âChristmas Tree school of designâ.)
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I have heavy scarring on some of my fingertips (including the right index finger) and sometimes encounter the same problem. People are like âwhy are you using your ring finger on the touchscreen?â and I say âuh, habit I guessâ.
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