Author Topic: Got shocked by 120VAC  (Read 3314 times)

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Offline MathWizard

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Got shocked by 120VAC
« on: June 04, 2021, 04:58:18 am »
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 problem

But 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.
 

Offline BrokenYugo

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Re: Got shocked by 120VAC
« Reply #1 on: June 04, 2021, 05:18:55 am »
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.
« Last Edit: June 04, 2021, 05:22:01 am by BrokenYugo »
 

Online james_s

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Re: Got shocked by 120VAC
« Reply #2 on: June 04, 2021, 05:57:14 am »
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.
 

Online MarkF

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Re: Got shocked by 120VAC
« Reply #3 on: June 04, 2021, 08:13:45 am »
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.   :-DD
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.
 

Offline themadhippy

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Re: Got shocked by 120VAC
« Reply #4 on: June 04, 2021, 09:25:42 am »
Bunch of wimps,come on over to 230v to earth  land.
 
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Offline John B

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Re: Got shocked by 120VAC
« Reply #5 on: June 04, 2021, 09:40:22 am »
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.
 

Online MasterTech

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Re: Got shocked by 120VAC
« Reply #6 on: June 04, 2021, 10:09:08 am »
Bunch of wimps,come on over to 230v to earth  land.

Yes, the difference between a 120V and a 240V shock is quite something.
 

Offline Quarlo Klobrigney

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Re: Got shocked by 120VAC
« Reply #7 on: June 04, 2021, 12:34:22 pm »
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:
« Last Edit: June 04, 2021, 12:50:16 pm by Quarlo Klobrigney »
Voltage does not flow, nor does it go.
“I do 7 things at a time, I do them very well, and then I move on.”
 

Offline Siwastaja

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Re: Got shocked by 120VAC
« Reply #8 on: June 05, 2021, 12:58:19 pm »
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.
« Last Edit: June 05, 2021, 01:02:19 pm by Siwastaja »
 
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Offline LECKO

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Re: Got shocked by 120VAC
« Reply #9 on: June 05, 2021, 03:07:29 pm »
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!!
 

Offline BrokenYugo

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Re: Got shocked by 120VAC
« Reply #10 on: June 05, 2021, 04:24:04 pm »
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.
 

Offline Siwastaja

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Re: Got shocked by 120VAC
« Reply #11 on: June 05, 2021, 04:43:48 pm »
Yes, extra low voltage regulations do not have 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.
 

Offline YetAnotherTechie

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Re: Got shocked by 120VAC
« Reply #12 on: June 05, 2021, 09:44:02 pm »
For the unbelievers, here's a 9V battery death:

https://darwinawards.com/darwin/darwin1999-50.html :popcorn:
 
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Offline dunkemhigh

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Re: Got shocked by 120VAC
« Reply #13 on: June 06, 2021, 12:07:49 am »
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?
 
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Offline vk6zgo

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Re: Got shocked by 120VAC
« Reply #14 on: June 06, 2021, 02:56:52 am »
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.

Or in Western Australia, till relatively recently---250v land!
 

Offline GlennSprigg

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Re: Got shocked by 120VAC
« Reply #15 on: June 06, 2021, 10:34:05 am »
One important TIP for young players!....
It's NOT uncommon to either leave or find possibly live old wires, in many scenarios.
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!!   :palm:
If you do this, ALWAYS strip the insulation back, and screw the termination onto the copper!!   :-+
Diagonal of 1x1 square = Root-2. Ok.
Diagonal of 1x1x1 cube = Root-3 !!!  Beautiful !!
 
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Online elekorsi

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Re: Got shocked by 120VAC
« Reply #16 on: June 06, 2021, 12:10:06 pm »
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.
I 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%
 

Offline tkamiya

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Re: Got shocked by 120VAC
« Reply #17 on: June 06, 2021, 06:40:28 pm »
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.
 
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Offline AlbertL

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Re: Got shocked by 120VAC
« Reply #18 on: June 06, 2021, 06:57:19 pm »
For the unbelievers, here's a 9V battery death:

https://darwinawards.com/darwin/darwin1999-50.html :popcorn:

He was trying to measure his internal resistance, but I guess what he ended up testing was the internal resistance of a 9-volt battery!
 

Offline vk6zgo

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Re: Got shocked by 120VAC
« Reply #19 on: June 06, 2021, 11:40:17 pm »
One important TIP for young players!....
It's NOT uncommon to either leave or find possibly live old wires, in many scenarios.
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!!   :palm:
If you do this, ALWAYS strip the insulation back, and screw the termination onto the copper!!   :-+
Then 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!
 

Offline ledtester

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Re: Got shocked by 120VAC
« Reply #20 on: June 07, 2021, 04:25:18 am »
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.
 
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Online Mark

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Re: Got shocked by 120VAC
« Reply #21 on: June 07, 2021, 09:19:12 am »
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 information might 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.   ;)
 
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Online Zero999

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Re: Got shocked by 120VAC
« Reply #22 on: June 07, 2021, 09:45:44 am »
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 information might 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.   ;)
It'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.
 

Offline Siwastaja

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Re: Got shocked by 120VAC
« Reply #23 on: June 07, 2021, 11:13:49 am »
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.
 

Offline BradC

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Re: Got shocked by 120VAC
« Reply #24 on: June 07, 2021, 11:54:23 am »
These too operated at 25 volts DC, take it from me it hurts when your hands are wet from dripping salt water!!

I 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.

 
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