Got shocked by 120VAC - Page 1
Forum section: electronics / general

author: MathWizard
author_rank: Super Contributor
timestamp: June 04, 2021, 04:58:18 am
content: I was doing some drywall plastering for a friend, and there was a connection box for a light, with a 14/2 wire stuck out of it, not stripped, just cut-off even, and I thought it was off, or not even possible to touch so I never considered it a problemBut like a fool, I managed to brush the underside of my wrist right across the wires, and I got a slight tingle. So I think I made contact the live wire, and/or the N or G lead right next to it in the sheathing, as I only felt something in my lower arm, and not down and out through my feet.Last week I was worried about getting a shock of a 70V transformer and I was really careful. So it's my own fault for not checking the wire or taping it off.

author: BrokenYugo
author_rank: Super Contributor
timestamp: June 04, 2021, 05:18:55 am
content: Non contact probes are cheap, and even the cheap ones work, just saying. That said in my experience you more or less have to be standing in a puddle to get bit hard by 120 AC. I think my worst was working on a furnace, standing on a damp concrete floor in just socks or maybe barefoot, grabbed a stranded wire near a wire nut that some idiot decades ago had a left a loose strand sticking out of, quite the firm handshake but not as bad as the lawnmower ignition.I remember seeing some old electrician training book from the 50s that seriously suggested one just use the back of their hand to check for presence of AC power, reporting that most could tolerate up to 240V.

author: james_s
author_rank: Super Contributor
timestamp: June 04, 2021, 05:57:14 am
content: I've been zapped by 120V a bunch of times and it never gets any more pleasant. The older I get, the more careful I am with it, haven't been shocked by it in a while. Don't work with electricity while you're tired and make sure any live circuits are properly capped off. 120V is not usually lethal but it can and does kill people once in a while.

author: MarkF
author_rank: Super Contributor
timestamp: June 04, 2021, 08:13:45 am
content: I burnt a 1/4" off the end of my needle nose pilers once. I was replacing a switch in a box with two other switches. I had turned off the circuit I was working on. However, the switch next to it was still live. My mother didn't appreciate my welding in the living room.Non-insulated handles and didn't even get a shock. Lucky.When I was seven, I tried to pulled broken prongs from a wall socket with my bare fingers. Very stimulating! That's when I started my electrical career.Probably my worse shock was when I got my hand against 120VAC 400Hz. I'll take 60Hz any day. The 400Hz stuff carries quite a bite. I could still feel it the rest of the afternoon.

author: themadhippy
author_rank: Super Contributor
timestamp: June 04, 2021, 09:25:42 am
content: Bunch of wimps,come on over to 230v to earth land.

author: John B
author_rank: Frequent Contributor
timestamp: June 04, 2021, 09:40:22 am
content: Old homes are a joy. One thing I have learned to look out for is architrave wiring, where the lighting switch wires run through the thin strips of wood around the door frames. Many have nails straight through the live wires - this is 240V land too.

author: PartialDischarge
author_rank: Super Contributor
timestamp: June 04, 2021, 10:09:08 am
content: Quote from: themadhippy on June 04, 2021, 09:25:42 amYes, the difference between a 120V and a 240V shock is quite something.

author: Quarlo Klobrigney
author_rank: Super Contributor
timestamp: June 04, 2021, 12:34:22 pm
content: Not to scare anyone but someone who has had a bad electric shock can have cardiac arrhythmia long after the shock.I worked with a guy that had a power strip in a rack that he was removing.These metal 6 circuit strip (3 Edison Outlets), made of metal, had a habit of popping their back covers if moved.It shocked the hell out of him as he grabbed the metal backed now open strip with full contact. 120V is irrelevant. It's the current that kills. The voltage just breaks the skin resistance to help kill you.I would suggest looking at the following:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2658458/He went to the hospital and was found, when hooked to the EKG to have an arrhythmia, a 30 something year old guy in good health. I used to complain about the people who would whine getting a shock "just suck it up" I don't any more.A sample of the ubiquitous strips found everywhere:

author: Siwastaja
author_rank: Super Contributor
timestamp: June 05, 2021, 12:58:19 pm
content: Quote from: Quarlo Klobrigney on June 04, 2021, 12:34:22 pmI wouldn't expect to read this bullshit on the EEVBlog forum...Voltage is what defines the current that flows through the (complex and nonlinear) impedance of the human being. That's exactly why all the safety regulations are based on voltage. Safety voltage / extra low voltage limit for 50/60Hz AC being roughly around 40-60V depending on the jurisdiction. Seehttps://en.wikipedia.org/wiki/Extra-low_voltageAnyway, comment about delayed arrhythmia is a good one. It's always a good idea to get checked if in doubt.

author: LECKO
author_rank: Newbie
timestamp: June 05, 2021, 03:07:29 pm
content: I was a mining electrician, trained in the UK worked in several mines there, coal, gypsum and potash, then tin and coal in Australia. It was rare to hear of shocks as it was illegal to expose live conductors to the air, more so in hazardous mines like coal.I was a district electrician at a potash mine in north Yorks, UK, it was a "gassy" min so everything was either flameproof, (explosion proof) or Intrinsically safe. I got a call from an under cutting machine driver, who said he'd had a shock. Any reports like that are ALWAYS treated seriously. The machine was fed with 1100 volts via a trailing cable from what we called gate end boxes, switchgear, either a section switch or a contactor box, both with extensive safety circuits like monitoring of the earth continuity to the machine, earth fault protection, overload etc.My first thoughts said impossible, but I still had to investigate. I found nothing wrong, everything was working correctly, nothing loose or shorting, all tests proved OK. I called my Foreman, and we went through everything together, nothing found.So I asked the operator, a good friend of mine to show me exactly he was doing when he got the "shock"... Once he showed me the penny dropped. we used extension trailing cables joined with restrained flameproof couplers, the plugs were tightened in place by screw clevis pins, he lifted the coupler with both cable plugs, and dropped it. I reached down and tightened by clevis pins tight...What had happened was a 25 volt shock, hot conditions and very salty, combined with his sweat, made a good contact. The cutters were fed from a section switch, the earth continuity, (pilot circuit) was powered by 25 volts DC in what is called an intrinsically safe circuit, not enough energy to ignite methane. In ideal conditions he'd never have felt it. After tightening the plugs, he couldn't feel anything.At the same mine I was called to the shaft bottom, the gate safety interlocks had failed locking the winding engine brakes on. One of the snap lock switches had failed from salt water corrosion. So I signed a new switch out from the stores. These too operated at 25 volts DC, take it from me it hurts when your hands are wet from dripping salt water!!

author: BrokenYugo
author_rank: Super Contributor
timestamp: June 05, 2021, 04:24:04 pm
content: Yeah, wet and salty certainly calls for extra caution, reminds me of when I learned not to load rods in a buzz box welder bare handed while soaked in sweat and sitting on the thing connected to the group clamp. Those have killed people in extreme scenarios with an open circuit voltage around 70V.

author: Siwastaja
author_rank: Super Contributor
timestamp: June 05, 2021, 04:43:48 pm
content: Yes, extra low voltage regulations donothave much margin. If the target is below 1ppm mortality in a shock event, you really can't go much above the SELV limits, and may even prefer to add some extra margin.

author: YetAnotherTechie
author_rank: Regular Contributor
timestamp: June 05, 2021, 09:44:02 pm
content: For the unbelievers, here's a 9V battery death:https://darwinawards.com/darwin/darwin1999-50.html

author: PlainName
author_rank: Super Contributor
timestamp: June 06, 2021, 12:07:49 am
content: Quote from: Siwastaja on June 05, 2021, 12:58:19 pmPerhaps an apology to Quarlo K would be appropriate at this point?

author: vk6zgo
author_rank: Super Contributor
timestamp: June 06, 2021, 02:56:52 am
content: Quote from: John B on June 04, 2021, 09:40:22 amOr in Western Australia, till relatively recently---250v land!

author: GlennSprigg
author_rank: Super Contributor
timestamp: June 06, 2021, 10:34:05 am
content: OneimportantTIP for young players!....It's NOT uncommon to eitherleaveorfindpossiblylive old wires, inmanyscenarios.It seems obviously BAD to just cut a wire off!!, even if the Copper is not apparently visible...That's a given!...However, what's WORSE, is when someone THINKS they are making it safe, by putting a Blue-Point Connector on the end, like...BUT putting it OVER the plastic of the wire!! People may TEST the screw-head inside the connector, and think it is dead!!If you do this,ALWAYSstrip the insulation back, and screw the termination onto the copper!!

author: elekorsi
author_rank: Regular Contributor
timestamp: June 06, 2021, 12:10:06 pm
content: Quote from: BrokenYugo on June 04, 2021, 05:18:55 amI do this regulary,..After confirming it with multimeter that there is no lethal voltage present, i quickly touch with the back of my right hand, whil keeping the left one on my back. I can say that after multimeter measurment i am 99% sure and after hand check i am 100%

author: tkamiya
author_rank: Super Contributor
timestamp: June 06, 2021, 06:40:28 pm
content: When I was going through electrician's license education program, I was told time and time again, if you didn't turn the circuit breaker off yourself and measured it yourself, assume every line LIVE. I still follow this.Risk from 120V in DRY ENVIRONMENT is not really the electricity itself. You could yank your hand off and hit something else. You could fall off a rafter. You could fall off ladders. You could fling tools and hurt someone else.Common practice is to put a wire nut on unused but live wire. It was unprofessional of someone who did that years ago.

author: AlbertL
author_rank: Regular Contributor
timestamp: June 06, 2021, 06:57:19 pm
content: Quote from: YetAnotherTechie on June 05, 2021, 09:44:02 pmHe was trying to measurehisinternal resistance, but I guess what he ended up testing was the internal resistance of a 9-volt battery!

author: vk6zgo
author_rank: Super Contributor
timestamp: June 06, 2021, 11:40:17 pm
content: Quote from: GlennSprigg on June 06, 2021, 10:34:05 amThen wrap it with multiple layers of insulation tape.By the way, the latter gets a "bad rap".We tested two layers of "El Cheapo" tape with a Trimax Ionisation Tester, & it held out till around 10kV.It just shows how much overkill we use in normal work.If you ever see one of those Ionisation Testers up for sale cheap, grab it-- they are loads of fun!

author: ledtester
author_rank: Super Contributor
timestamp: June 07, 2021, 04:25:18 am
content: Two quick anecdotes...I watched as HVAC installer get shocked several times as he replaced a controller for a boiler. He couldn't find the fuse for the controller circuit but decided to proceed with the replacement anyway. He talked as if it wasn't the first time he had done this.An electrician was called in to add a ground wire to a circuit. When he turned the circuit back on a loud pop came from a VCR. Turned out he had wired the circuit for 240V instead of 120V. Fortunately the only casualty was the VCR.--- And you could say we were very lucky the VCR popped alerting us to the problem while the electrician was still around.

author: Mark
author_rank: Frequent Contributor
timestamp: June 07, 2021, 09:19:12 am
content: I have a reference book that tells me that anything up to 100V is fine to handle. Up to 200V should be handled with caution.400-500V should be regarded dangerous.You might get a shock from 100V if you were standing on a wet floor and had wet boots and wet skin.If the conditions were reversed, up to 300V might not do any harm.The above informationmight be a bit out of date, it comes from "POWER AND ITS TRANSMISSION, A practical handbook for the factory and works manager" by Thomas A. Smith, 1910.

author: Zero999
author_rank: Super Contributor
timestamp: June 07, 2021, 09:45:44 am
content: Quote from: Mark on June 07, 2021, 09:19:12 amIt's clearly out of date. They were much less bothered about safety 100 years ago, than today.Those voltage sound way too high. Are they mains frequency AC, or DC? DC is less hazardous, than mains frequency, given the same current/voltage. I'm generally more careful, when the voltage gets above 60VDC, or 25VAC, purely because that's what the safey standards say.

author: Siwastaja
author_rank: Super Contributor
timestamp: June 07, 2021, 11:13:49 am
content: It's all about probability distribution and how that compares with other risks around us.In 1910's, it was considered normal to just die out of unknown disease for no reason whatsoever.If you compare to that, if you receive one hundred 100VAC electric shocks during your career and each carries a risk of death of, say, 10-100 ppm, you are most likely still alive, and way more likely dead due to all the other safety issues in the society.The risk of death is still the same today, but we just expect higher level of safety. In most usual dry conditions, 100VAC is a very small risk, but a real risk nevertheless.People were not extremely stupid back then, still. Unnecessary and large risks were not routinely taken. That is why you won't find a citation saying 230VAC is safe to handle. It is so much more dangerous, even on yesterday's standards.

author: BradC
author_rank: Super Contributor
timestamp: June 07, 2021, 11:54:23 am
content: Quote from: LECKO on June 05, 2021, 03:07:29 pmI was working in a stinking hot bilge, dripping with sweat and kneeling on an earthed intake strainer that had just flooded with salt water. The 10mm spanner in my hand that I used to tighten the nut on the back of the 24V alternator let me know in no uncertain terms that with sufficient skin surface area and conductivity low voltage can hurt like hell.

author: Calaverasgrande
author_rank: Contributor
timestamp: June 07, 2021, 02:42:35 pm
content: My first AC shock was when I was 11. Helping out after science class to clean and store all the beakers and mantles. Reached for the faucet to turn the water off and...got full North American AC.Water had run down the counter and reached an outlet. This being the early 80's it was not GFCI!I couldn't let go of the faucet, as my hand was clenching from the current.Not sure how long I was hanging on to that faucet like a lizard on a cattle fence. But the teacher finally pulled me free. Man they were on eggshells around me and my mom for months.Most recent time was working on some networking equipment in Grand Central Station, Manhattan.There is this thing in New York City where they just don't give a damn about cable management. A lot of cable drops are a huge mess. There is also this annoying thing in NYC that many buildings are historic, so you can't create new cable drops, or cut, drill or screw into anything. So it's not uncommon to be trying to to tone out or pull cat 6 and get honked by some AC.Grand Central Station is of course an Historic building.I was in a closet, bent over an ice machine with my hand on a Middle Atlantic rack when I get buzzed. Thankfully my hand wasn't able to clench on anything so I just stumbled back. Otherwise, nobody would have seen me in there dancing on a wire.

author: Quarlo Klobrigney
author_rank: Super Contributor
timestamp: June 07, 2021, 03:46:21 pm
content: Some people will never get it.Quote from: dunkemhigh on 2021-06-05, 09:07:49>Quote from: Siwastaja on 2021-06-04, 21:58:19>Quote from: Quarlo Klobrigney on 2021-06-03, 21:34:22I wouldn't expect to read this bullshit on the EEVBlog forum...Perhaps an apology to Quarlo K would be appropriate at this point?

author: GlennSprigg
author_rank: Super Contributor
timestamp: June 11, 2021, 11:38:15 am
content: Quote from: Quarlo Klobrigney on June 07, 2021, 03:46:21 pmI wouldn't expect to read this bullshit on the EEVBlog forum...Perhaps an apology to Quarlo K would be appropriate at this point?Well... The 2nd sentence, above, that I put in Bold, IS true!!, though the rest is crap...It IS the 'Current' that kills!!!

author: PlainName
author_rank: Super Contributor
timestamp: June 11, 2021, 11:48:59 am
content: I = V/R, so given the major impediment to dying is skin resistance, does not a higher voltage mitigate that skin resistance? Or are you just quibbling about the way a non-native English speaker has phrased it?

author: GlennSprigg
author_rank: Super Contributor
timestamp: June 11, 2021, 12:51:17 pm
content: Quote from: dunkemhigh on June 11, 2021, 11:48:59 amSorry mate. I'm not sure who (to whom?) you were answering to. Be it myself, (prior answer), or someone else...And I certainly was not picking on or quibbling about any "non-native English" person/speaker...As you say, and everyone here knows, I=E/R, but it is not 'X' number of volts that's the problem. And of 'course' the 'resistance'then plays a critical part. Except where the voltage is high enough to 'physically JUMP' across such resistive barriers.If you are hot & sweaty, standing on a wet floor with bare feet, and have a good grip on a referenced conductor with even 80-100vor what ever, and the current approaches 20-30ma, then you can die!! Now grab hold of a 50-100 thousand volt Van-De-Graphgenerator which has no ability to supply the 'current' necessary to be dangerous, then you can laugh at the sparks!!P.S. The above 2 lines...I wouldn't expect to read this bullshit on the EEVBlog forum...Perhaps an apology to Quarlo K would be appropriate at this point?were NOT my quote. It was meant to be forwarded from someone elses

author: SteveyG
author_rank: Unknown
timestamp: June 11, 2021, 01:09:23 pm
content: Quote from: GlennSprigg on June 11, 2021, 11:38:15 amIt's not though, since it's not a single factor. It's most reliable to say that exceeding a specific amount of energy is what can stop the heart - There are factors in both power and time. The human body could survive kiloamperes of current if the duration is short enough.Quote from: GlennSprigg on June 11, 2021, 12:51:17 pmAre you saying that somehow a Van de Graaff generator is somehow able to alter the laws of physics by somehow conducting only a tiny amount of current through a person despite a high voltage being present across them?

author: Zero999
author_rank: Super Contributor
timestamp: June 11, 2021, 01:44:54 pm
content: Quote from: SteveyG on June 11, 2021, 01:09:23 pmA Van de Graaff generator is a constant current source of a few µA. It outputs the same current, regardless of the open circuit voltage, up to a point, when the voltage is so high, it arcs over. If you put one hand on the dome and the other on the earthed side and turn it on, the open circuit voltage will be tiny and the current too low to shock. If you allow the dome to charge, the voltage will increase. If you discharge the dome into your finger, you'll get a shock, but it won't be dangerous, because the dome has too little capacitance, to store enough energy to be hazardous. If you connect it to a large capacitor and leave it running, it can deliver a lethal shock.

author: SteveyG
author_rank: Unknown
timestamp: June 11, 2021, 02:17:41 pm
content: Quote from: Zero999 on June 11, 2021, 01:44:54 pmExactly.The other poster mentioned a "50-100 thousand volt Van-De-Graaf generator which has no ability to supply the 'current'". That's not how it works - as you say, if you present an impedance the voltage has to collapse. That being said, the dome holds a charge and will discharge a given amount of energy if touched without previously being discharged. In this case, the peak current can be many amperes.

author: TheBay
author_rank: Unknown
timestamp: June 12, 2021, 12:06:21 am
content: When I was an electronics engineer for LG one of workers that was stationed on the line reject repair bin had extraordinary stats for repairs or diagnosis and we couldn't figure out how.He was asked to go to Korea to train some staff there. On the first night there he was invited out with the staff that he was training and somehow manged to get them that drunk they were seriously ill and off work for 2-3 days with hangovers/alcohol poisoning.When that settled down he started training the staff. And promptly got reprimanded.It turns out he thought using a multimeter took too long to fault find, his method was pulling the PCB out of the CRT Monitor/TV and touching B+,G1, G2 and other voltages while it was powered up! That did not go down well at all in Korea or back in the UK.In the same factory a CRT monitor went down the production line and one of the line workers noticed the "Red cable" wasn't connected to the CRT, so they grabbed the EHT lead and tried to clip it in to the tube, while leaning over the production line. The shortest path to earth was through his genital area. He seriously felt that but was okay after a visit to the hospital.My late father was an industrial engineer, fabricator and welder.He always maintained the worst electric shocks he had by far ( Even getting shocked working with single 240V and 3 Phase) was from Arc welders, especially if he was sweaty or in a pool of water.

author: Siwastaja
author_rank: Super Contributor
timestamp: June 12, 2021, 07:21:49 am
content: If it's "current that kills", then you may want to try to explain yourself how RCDs are able to save lives. Note, they can't limit current, it is what it is; they only limit thetime.No need to reply to me; I'm not interested in social games. I prefer intellectual honesty so work it out in your own head. It's not all that complex if you choose to ignore rules developed 100 years ago for explaining things to laymen using bad analogies. Instead, work with the basic units available to us scientists and engineers. Voltage, current, resistance, impedance, power, time, energy... For example, a high-impedance high-voltage supply forms a classicvoltage dividerwith the body impedance, and the lower the body impedance, the lower thevoltageover body. Think about all of this instead of playing social games.

author: LECKO
author_rank: Newbie
timestamp: June 12, 2021, 01:58:42 pm
content: As a maintenance mining elec by trade, finished my apprenticeship in 1968 at the golden age of 21, with the UK National Coal Board, I won't quibble with voltage and current, we had both. 3.3Kv at that time underground, to later 6.6Kv and when I finished in NSW Australia 11Kv underground with 300amp CB's. I was also authorized to enter the main switchyard where 66Kv was around. My engineer said to me after being authorized as a Leading Hand Elec, "John, if you have to enter the switchyard, stay on the marked foot paths, DON'T stray from them, 66Kv can jump a fair distance, and we don't want to scrape your remains up off the floor".During my first year training at the area training center, we did week about in the first year, one week training center, one week Tech College, we covered this issue of voltage v current and AC v. DC shocks.TOO MANY VARIABLES to argue over, wet conditions, whether the person shocked was fit, tired, sick, etc, etc.Severe shock from one hand through the torso and out the other hand was the most dangerous way to have a shock, second was left hand through the body to ground, both are through the heart.I used to take some dangerous risks when the voltages were 440 and 550 three phase, once we installed 1.1Kv equipment the risks stopped, and it was to the letter of the law. "Isolate and ground" Which is still my present attitude on ALL voltages above 25 AC., and on the test bench, left hand behind the back when checking voltages with a multimeter.That one shock too many could be the one that makes your wife a widow. In my late teens I worked with an electrician who survived 3.3Kv in an illegal situation underground in a coal mine. It was covered up!When I was a leading hand elec, I got a phone call to get down to another district in the mine, one of my young elecs had got burned, cost be three hours in paperwork, report for the Elec Mines Inspector! The lad was lucky, burns to the arms and face, he broke the rules accidentally on a 1000 volt circuit.

author: Zero999
author_rank: Super Contributor
timestamp: June 12, 2021, 02:00:51 pm
content: Quote from: Siwastaja on June 12, 2021, 07:21:49 amIt's pretty obvious time is a factor, as well as current. As mentioned above, a Van de Graaff generator discharging into someone might give a peak current of 50A, but it's such a short duration, it doesn't cause any damage.

author: GlennSprigg
author_rank: Super Contributor
timestamp: June 13, 2021, 11:24:39 am
content: Quote from: Zero999 on June 12, 2021, 02:00:51 pmYes... I was obviously 'remiss' not to 'understand' (which I did), but to 'Include' the obvious 'Time-Factor'. Obviously I was not talking aboutthe likes of RCD's or ELCB's etc tripping in MilliSeconds, But someone getting hold of such an Earth referenced conductor, without such protection. So to correctmy statement... It is not 'X' number of Volts that is the problem, but 'X' number of milliamps for a specified time! I'm no-one's enemy here!!

author: Siwastaja
author_rank: Super Contributor
timestamp: June 13, 2021, 11:55:41 am
content: It's also worth understanding1) Ohm's law2) The difference between a current source and a voltage source3) The rarity of true current sources, and the abundance of voltage sources, around usto see why safety limits are primarily given in voltages, not currents.Ohm's law connect the two together so it's makes zero sense to argue "which is dangerous", they are different ways to look at the same thing, namely energy transfer. Current and voltage are just tied together, if there is dangerous voltage applied to a human body, there is dangerous current flowing, and vice versa. So you choose current or voltage viewpoint depending on which is the suitable tool for the task. Voltage limitation (of the voltage source), or current limitation (of the current source) ensures safety the easy way - i.e., use Safety Extra Low Voltage - but isn't always an option.

author: PlainName
author_rank: Super Contributor
timestamp: June 13, 2021, 12:00:40 pm
content: QuoteI don't believe anyone has suggested that's the case. Perhaps you could point out where you think they have, and then we will all have a common base to work from instead of making up our own straw men to then knock over.

author: VK3DRB
author_rank: Super Contributor
timestamp: June 13, 2021, 12:16:00 pm
content: Quote from: Siwastaja on June 05, 2021, 12:58:19 pmHe is correct in that it is the current that kills. But it is related to voltage of course, so 120V is not irrelevant.Your comment reminded me of an argument I had with another engineer at the workplace lunchroom who thought he knew it all. OK, he had a PhD in electronics engineering and I only had the degree. But I knew what I was talking about. IBM Australia years earlier placed every engineer on an electrical safety course. I learnt then that 20mA through the body can easily kill a person by electrocution. The PhD refused to believe me that so low current can kill a person, saying it would take several hundred milliamps. You could not argue with this guy who was a little arrogant, but I refused to backdown. Unbeknown to me, he decided to research it for himself.Two days later, in front of my peers at the lunchroom table, he apologised publicly, admitting he was wrong and I was right. It was a complete shock (no pun intended). From that day on, he was never argued or was arrogant with me again, and we ended up becoming good friends.

author: GlennSprigg
author_rank: Super Contributor
timestamp: June 13, 2021, 01:35:23 pm
content: Quote from: VK3DRB on June 13, 2021, 12:16:00 pmThank you. It's not rocket science, or bragging about 'knowledge/power', or deliberate 'put-downs' when us 'mere-mortals' dare to say something...Responses like... "I'm not interested in social games. I prefer intellectual honesty so work it out in your own head."... and "Think about all of this instead of playing social games.",and ... "...instead of making up our own straw men to then knock over."... W.T.F. ?? I wish these 'Tower-Climbers' would climb down the mountain a bit...

author: Quarlo Klobrigney
author_rank: Super Contributor
timestamp: June 13, 2021, 01:37:01 pm
content: The irrelevancy was to the fact of the 240V vs. 120V argument.My comment was taken out of context. I was also relating to low voltage death.I can put an idea forward and see who wold expand upon it.I got an a nasty shock, similar to 120V when working on my van battery in a tight place, and being a hot summer day, I wassweatyperspiring excessively and got in between the battery cable and the post, and who knows in that tight spot, the chassis. Whatever current being drawn was it was enough to knock me on my ass.Yes I am a native speaker having been born in the US and made it through the 12th grade and much more education than that.So to sum up, I say the higher the voltage is, the easier it is to break through the skin's resistance which lets more current through to do the dirty work.As another topic, RF burns being quite nasty as well having had a few myself.In the very early 80's having had ~ +/- 2KV across the chest from a defective HV measurement probe (open ground) in the right hand, then out the left knuckle to the cabinet, it propelled me off the stool vertically. Weighing in at 150 pounds, gravity took over and I landed on my back some 6' away. Anotherpersonsaw me "fly" through the air. It took a minute or so before all the white light, and the underwater sounds, for my senses and locomotion to return to normal.All saidpersondid was to watch and comment later after I got to my feet.My experiences and the way I have lived them and what I have learned to be true in my life.-30-Quote from: VK3DRB onTodayat 21:16:00

author: Siwastaja
author_rank: Super Contributor
timestamp: June 13, 2021, 03:19:05 pm
content: Quote from: VK3DRB on June 13, 2021, 12:16:00 pmNice story. This involves statistics and exact semantics; but of course, when it's about such serious matter as dying, you can't accept even 1% likelihood.20mA won'tthateasily kill someone unless they have existing heart condition, or are just very unlucky. But if the question is whether itcankill someone, yes, you are then absolutely right. At several hundred mA, it just becomes verylikely. So all he did wrong might have a slightly distorted mental image of the probability distribution, it doesn't need to be very far off.There is a reason why 30mA is a popular choice for RCDs, it gives very good (albeit not perfect, but nothing is) defence against death by electrocution and won't nuisance trip too easily, but you are right, some oddball resistive path limiting current (and voltage!) could result in a continuous 20mA fault current through body for prolonged time which could kill an unlucky individual. A 10mA RCD would protect against such case, but then again, we might find an even more unlucky individual at the tail of the distribution function who can't take even 10mA.Personally, I have received 230VAC (full-bridge rectified) hand-to-hand which would have had very high chances of being fatal, but a 30mA RCD really saved the day, and I can testify it's really efficient, the shock wassurprisinglybenign due to very limited time; for example, muscle pain in my arms that day was only slightly uncomfortable. No changes in heartbeat or nausea or anything like that. Glad it was a type A RCD, this wasn't obvious back then, type AC was still widely used and it wouldn't necessarily have tripped due to fault current going through a rectifier. Nevertheless, it was an extremely stupid thing to do, I had a mental image of a MOSFET bridge being isolated but the gate driver wasn't isolated, so there was a direct path from rectified mains, through lower leg MOSFET source, to the touchable control circuit side. Be very careful tocompletelyunderstand the circuit, which is also why I stress the importance of understanding instead of learning rules and analogies by heart.

author: Siwastaja
author_rank: Super Contributor
timestamp: June 13, 2021, 03:45:56 pm
content: Finally, to set the record straight, the problem with the simplistic claim "it's the current that kills" isn't just that it's not correct, it's that it provides "wrong" level of abstraction which isn't very useful, and which is highly confusing. To make matters worse, it's very widely taught as some kind of "truth" which it just isn't.Because if we take the viewpoint of the human body, then it's not right, you could say it's only half the truth but it's lacking so much I continue to call it "wrong". Using Van der Graaf generator or a cat, it's easy to demonstrate currents exceeding hundreds of mA go through body with absolutely no harm done. ESD currents are regularly in amperes, no biggie. So current clearly isn't what kills.Time, or the integral of the current, is equally important, these two variables are thebare minimumfor a model describing what happens to the body, but the model gets better the more we add to it.We can also take the more practicalcircuit designviewpoint of what circuits are safe, what circuits are not, and how to protect them, based on what criteria. This viewpoint is what legislation uses, and yes, because most circuits use low-impedancevoltage sources, the mains supply networks, generators, batteries, solar panels being obvious examples, then the only sane thing is to base the safety ruleson voltage, for example, consider <50VAC or <100VDC safe to touch, otherwise add reliable layers of insulation and/or earthing.I'm truly surprised I'm discussing this on the EEVblog forum, though, and not in the beginner's section. I thought all of this is obvious for many here. I remember Dave calling "voltage kills" claim bullshit in some of his videos but may remember wrong.I'm also surprised people take calling "bullshit" "bullshit" so personally given that this B word is so prevalent on this forum and on Dave's videos, but I may have missed some social factor I'm not too good in, maybe it's OK to call bullshit when it's about anoutsider'svideo, or a post by some of thelower-classmembers, but I'm not aware of Quarlo's social status because I have no idea who he is and what he contributes here, so clearly I hit the wrong button here. This is why I said I don't like these social games.

author: PlainName
author_rank: Super Contributor
timestamp: June 13, 2021, 04:05:39 pm
content: QuoteThat, there, is the problem. If you'd just pop up and say no, that's not correct because...", then you'd have an audience listening to your argument and being enlightened. Bymakingit personal and derogatory you lost all that before you even said what was wrong.QuoteJust because someone safe behind a screen has no manners, you don't have to emulate them.

author: sandalcandal
author_rank: Unknown
timestamp: June 13, 2021, 04:11:01 pm
content: Quote from: Siwastaja on June 13, 2021, 03:45:56 pmI think you hit the nail on the head there. I think hostility to "out-groups" and protection of "in-groups" rather than a more intellectual open minded and objective consideration of the information is a bit of a human nature thing but also one of the more negative elements of culture on this forum thanks of the circumstances which attract people to this forum [I should add this a generalisation only applicable to the attitudes of some members of the forum but it does feel like the "prevailing" attitude to me]. Though I guess the same attitudes are also what keep discussions on this forum somewhat higher quality than other places on the internet.In this case however, given the nuances and complexity of the topic which you are well aware of, the response came across a bit unexpectedly blunt (IMO)? Certainly not much wrong with your underlying premise though the point could have been communicated with more tact if you wanted to calmly convince people but then again I don't think it was particularly inflammatory (unlike what I sometimes do...). Certainly it seemed a bit unnecessarily personal from the way you worded it.Edit: Would we be happy to say "energetic flow of electrical charge through certain parts of the the human anatomy kills"?

author: bjbb
author_rank: Contributor
timestamp: June 13, 2021, 09:33:37 pm
content: Quote from: Siwastaja on June 13, 2021, 11:55:41 amNot necessarily. Standards based on IEC62368 and IEC60601 establish ground/contact/touch limits in current.Per IEC60601-1, SELV is not always considered safe.And IEC62368-1 (see clause 5) classifies hazard levels per voltage and current and power and energy. But I am being a bit misleading because what is being mitigated are not just shock hazards but also fire hazards.But your phrase 'energy hazard' is dead on (pun not intended), because that is a focus of both the ITE and medical equipment standards.

author: vk6zgo
author_rank: Super Contributor
timestamp: June 14, 2021, 04:10:51 am
content: Quote from: dunkemhigh on June 13, 2021, 04:05:39 pmAarrr! Bullshit!I have said before, & as I am an OF, will repeat interminably------on Internet forums, it is perilously easy to create deadly enemies, even if you don't know why, or never had that intent.

author: bdunham7
author_rank: Super Contributor
timestamp: June 14, 2021, 04:24:58 am
content: Quote from: Siwastaja on June 13, 2021, 03:19:05 pmWe must be wimps. American GFCI standards are 5mA with a 6mA test current. 30mA GFI breakers are for equipment and wiring protection and now have arc-fault detection as well.

author: james_s
author_rank: Super Contributor
timestamp: June 14, 2021, 05:07:19 am
content: American GFCIs are typically only used for branch circuits that are in damp locations, originally they were only required for outdoor and bathroom receptacles, now they are required in kitchens, garages and some basements too. In the UK the ones I saw were the main breaker in the entire panel, maybe they figure 5mA would make it too much of a nuisance.

author: Siwastaja
author_rank: Super Contributor
timestamp: June 14, 2021, 07:11:57 am
content: 30mA has the advantage that you can use a single unit to protect several groups of circuits.It's a tradeoff, RCDs/GFCIs were much more expensive in the past, and it's better to have a very good albeit not perfect protection than no protection at all. You can of course force new installations to use however expensive solutions, but voluntary retrofits really benefit from the fact you can just install one unit in one place.And I guess a 30mA RCD protecting the whole house is better safety-wise than 6mA units protecting only the bathrooms.

author: Zero999
author_rank: Super Contributor
timestamp: June 14, 2021, 12:35:55 pm
content: Another benifit of an RCD for the whole house is, it provides protection for cables inside the walls, in case somone hammers a nail through a cable, in the wall, when they're hanging a picture.

author: PlainName
author_rank: Super Contributor
timestamp: June 14, 2021, 01:21:14 pm
content: QuoteWhen installing network cable at a previous employer, I drilled through a wall to find the bit had gone clean through the middle of T&E, leaving scuffs but unbroken insulation on live & neutral and somehow missing earth completely.Mind, that wasn't nearly so annoying as feeding coax between floors down the shaft behind toilet cubicles, only to find the seat left up on the lower level so the cable had come out of the wall and continued its merry way down the u-bend.

author: james_s
author_rank: Super Contributor
timestamp: June 17, 2021, 06:37:04 am
content: Quote from: Zero999 on June 14, 2021, 12:35:55 pmWe're not allowed to run wires such at this can reasonably happen to them. Code requires a metal nail plate be installed over every stud where a wire passes through it.https://www.homedepot.com/p/MiTek-1-1-2-in-x-3-in-G90-16-Gauge-Protection-Plate-60-Pack-UKNS1BK/313491991

author: Zero999
author_rank: Super Contributor
timestamp: June 17, 2021, 02:26:24 pm
content: Quote from: james_s on June 17, 2021, 06:37:04 amThe same is true here, but there's always the outside chance someone will do something stupid, hence the requirement for an RCD.https://the-regs.co.uk/blog/?p=586

author: Siwastaja
author_rank: Super Contributor
timestamp: June 17, 2021, 05:12:29 pm
content: Obviously an RCD has no purpose if everything is done properly by the rules and maintained as such.It's exactly there to save lives in cases of human error, including wiring in the wrong place.

author: ejeffrey
author_rank: Super Contributor
timestamp: June 17, 2021, 06:00:43 pm
content: Quote from: YetAnotherTechie on June 05, 2021, 09:44:02 pmI am an unbeliever, I think that story is almost certainly a myth or widely distorted.There is an easy and completely safe demo of this.Go take a multimeter and a jar of saline solution at human body temperature and measure the resistance just dunking the probe tips in. You will find it is quite high. The reason for that is the probe tips are have low surface area and the spreading resistance around them is still quite high. Now if you attach some alligator clips and some copper braid and try again there will be a much lower resistance. At low voltages it is a much bigger problem if you grab onto a large metal pipe vs pierce the skin with a small probe.

author: PlainName
author_rank: Super Contributor
timestamp: June 17, 2021, 08:00:42 pm
content: Head to foot resistance of the body appears to be ~400R which would give 22mA from a 9V battery. Since it's not head to foot, a larger current and severed complications seems possible. Possibly mitigated by being DC, though.https://www.researchgate.net/publication/335250921_Electric_Shock_Drowning_Causes_and_Prevention

author: ejeffrey
author_rank: Super Contributor
timestamp: June 17, 2021, 09:13:26 pm
content: Quote from: dunkemhigh on June 17, 2021, 08:00:42 pmGo do the experiment I suggested. Getting hundreds of ohms through salt water requires a very large electrode area.

author: PlainName
author_rank: Super Contributor
timestamp: June 17, 2021, 11:33:33 pm
content: Probes pushed hard enough to pierce skin would, I think, be a different scenario to tips dipped into saline solution gently enough not to disrupt surface tension. Thus I have a better idea: you repeat the sailor's experiment and then come back to tell us it is rubbish.[Edit: typo]

author: Deimos
author_rank: Newbie
timestamp: June 18, 2021, 07:12:09 am
content: My first 120v shock was when I was a teen 20 years ago fiddling with a Technics 5 disc CD changer, I was testing some stuff and forgot I had it plugged in when I rested my arm on the 120v input.My worst shock however, was from a CRT television I was trying to see why it didn't work, again young teen and knew next to nothing, but had to start somewhere right?Anyway grabbed the flyback anode cap at the CRT and it zapped my entire right arm, horrible pain through my entire arm that lasted for several minutes (I didn't even know what that suction cup thingy was). The TV was unplugged mind you, but I didn't know the CRT held a charge. Live and learn I guess and still be a alive.Learned not to be so careless after that. I did a lot of reading / research on discharging CRT's, capacitors, high voltage, etc. and none of that happened again. That was a nasty shock though.

author: Siwastaja
author_rank: Super Contributor
timestamp: June 18, 2021, 12:18:20 pm
content: I have hard time believing that 9V battery story as well.And I'm not saying the incident itself didn't happen; no, I can believe that it happened, but I have hard time believing the analysis of 9VDC being so dangerous after you remove the skin from the equation.People just die. Recently there was this soccer incident all over the media, 0 volts was involved; people have hidden heart conditions and they may trigger due to physical stress, doing sports, having sex, piercing your skin with multimeter probes while applying 9V DC; or, for no apparent reason whatsoever!

author: G7PSK
author_rank: Super Contributor
timestamp: June 18, 2021, 02:15:40 pm
content: Surely it is neither the volts or amps that kill but the power, somewhere arround 35j/s would appear to be what is required.