Got shocked by 120VAC

[Calaverasgrande]

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. 

[Quarlo Klobrigney]

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, 21:34:22

120V is irrelevant. It's the current that kills. The voltage just breaks the skin resistance to help kill you.

I wouldn't expect to read this bullshit on the EEVBlog forum...

Perhaps an apology to Quarlo K would be appropriate at this point?

[GlennSprigg]

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, 21:34:22

120V is irrelevant. I

t's the current that kills. The voltage just breaks the skin resistance to help kill you.

I 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!!!

[PlainName]

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?

[GlennSprigg]

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?

Sorry 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 80-100v
or what ever, and the current approaches 20-30ma, then you can die!!  Now grab hold of a 50-100 thousand volt Van-De-Graph
generator 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 

[SteveyG]

Well... The 2nd sentence, above, that I put in Bold, IS true!!, though the rest is crap...
It IS the 'Current' that kills!!!

It'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.

Now grab hold of a 50-100 thousand volt Van-De-Graph
generator which has no ability to supply the 'current' necessary to be dangerous, then you can laugh at the sparks!!

Are 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?

[Zero999]

Well... The 2nd sentence, above, that I put in Bold, IS true!!, though the rest is crap...
It IS the 'Current' that kills!!!

It'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.

Now grab hold of a 50-100 thousand volt Van-De-Graph
generator which has no ability to supply the 'current' necessary to be dangerous, then you can laugh at the sparks!!

Are 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?

A  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.

[SteveyG]

A  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.

Exactly.

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.

[TheBay]

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.

[Siwastaja]

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 the time.

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 classic voltage divider with the body impedance, and the lower the body impedance, the lower the voltage over body. Think about all of this instead of playing social games.

[LECKO]

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.

[Zero999]

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 the time.

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 classic voltage divider with the body impedance, and the lower the body impedance, the lower the voltage over body. Think about all of this instead of playing social games.

It'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.

[GlennSprigg]

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 the time.

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 classic voltage divider with the body impedance, and the lower the body impedance, the lower the voltage over body. Think about all of this instead of playing social games.

It'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.

Yes... I was obviously 'remiss' not to 'understand' (which I did), but to 'Include' the obvious 'Time-Factor'.  Obviously I was not talking about
the 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 correct
my 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!!   

[Siwastaja]

It's also worth understanding

1) Ohm's law
2) The difference between a current source and a voltage source
3) The rarity of true current sources, and the abundance of voltage sources, around us

to 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.

[PlainName]

my statement... It is not 'X' number of Volts that is the problem

I 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.

[VK3DRB]

120V is irrelevant. It's the current that kills. The voltage just breaks the skin resistance to help kill you.

I 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. See https://en.wikipedia.org/wiki/Extra-low_voltage

Anyway, comment about delayed arrhythmia is a good one. It's always a good idea to get checked if in doubt.

He 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.

[GlennSprigg]

120V is irrelevant. It's the current that kills. The voltage just breaks the skin resistance to help kill you.

I 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. See https://en.wikipedia.org/wiki/Extra-low_voltage

Anyway, comment about delayed arrhythmia is a good one. It's always a good idea to get checked if in doubt.

He 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.

Thank 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...

[Quarlo Klobrigney]

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 was sweaty perspiring 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. Another person saw 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 said person did 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 on Today at 21:16:00

He is correct in that it is the current that kills. But it is related to voltage of course, so 120V is not irrelevant.

[Siwastaja]

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.

Nice 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't that easily kill someone unless they have existing heart condition, or are just very unlucky. But if the question is whether it can kill someone, yes, you are then absolutely right. At several hundred mA, it just becomes very likely. 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 was surprisingly benign 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 to completely understand the circuit, which is also why I stress the importance of understanding instead of learning rules and analogies by heart.

[Siwastaja]

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 the bare minimum for 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 practical circuit design viewpoint 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-impedance voltage sources, the mains supply networks, generators, batteries, solar panels being obvious examples, then the only sane thing is to base the safety rules on 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 an outsider's video, or a post by some of the lower-class members, 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.

[PlainName]

I'm also surprised people take calling "bullshit" "bullshit" so personally

That, 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. By making it personal and derogatory you lost all that before you even said what was wrong.

given that this B word is so prevalent on this forum and on Dave's videos

Just because someone safe behind a screen has no manners, you don't  have to emulate them.

[sandalcandal]

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 an outsider's video, or a post by some of the lower-class members, 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.

I 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"? 

[bjbb]

...
to 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.

Not 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.

[vk6zgo]

I'm also surprised people take calling "bullshit" "bullshit" so personally

That, 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. By making it personal and derogatory you lost all that before you even said what was wrong.

given that this B word is so prevalent on this forum and on Dave's videos

Just because someone safe behind a screen has no manners, you don't  have to emulate them.

Aarrr! 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.

[bdunham7]

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

We 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.