⚡Shock⚡ through the heart,

[kommando]

My first of many 240AC shocks was as a teenager delivering milk in a tower block, pressed the lift button where the plastic cover was broken and guess what happened. At least the lift showed up . I had a few more over the intervening decades but never felt much more than a tingle, engine HT leads are worse. I always use leather or rubber soled shoes so the amps never amount to much and the house has a 30ma RCD as well. High voltage DC is very different and I take a lot more precaution and so far never got caught and intend it to stay that way. Only test voltage on single PV panels and isolate each string separately with DC MCB even if that doubles up on DC disconnects.

 

[Spunky]

Look at these meter sockets with bypass. I think it is a DPDT switch shorting out the meter, apparently so utility can yank and replace meter without impacting customer.


View attachment 164960

These usually release the jaws also and make for a better connection with easier removal (as opposed to the friction fit type).
Picking up the whole house when everything is resetting can arc up the jaw connections and be less than ideal in the longterm.
Customers aren't always home to open Mains. New business won't get energized without the Mains being open.

 

[JS43]

When I was a kid, someone had cut an extension cord with a hedge trimmer.
Free extension cord so we stripped the ends and decided to see who could hold on the longest.
All was fun until both wires touched together.

hahaha, when I was maybe 5 or 6 I took a piece of slot car track apart. I took the metal piece out and stuck it in an outlet ? My father was on the otherside of that wall in the bathroom shaving with his electric razor. There was a huge flash and a loud pop! Knocked me on my butt. I start laughing and then see the burn mark on the wall. Then my father came in and he wasn't happy ? . Since then I seem to barely notice it when I get zapped working on stuff. Even installed a new meter box without having the electric shut off to the house we were working on ? Some of us just seem to live dangerously. I just tell people I already died so nothing can kill me. I did actually die when I was 6 months old so....

 

[Supermo26]

And you're to blame,
You give solar a bad name!

Meant to be safer than a cheater cord, power cord with shrouded banana plugs

View attachment 142879 + View attachment 142880

Similar wire and banana connected to equipment under test. Now it's easy to stack banana plugs and plug in HV scope probe.

View attachment 142884

It's just as easy to mix up Line and Ground connections, resulting in hot chassis.
Use UPS to create 208 or 230V at 50 or 60 Hz for testing, then put one hand on DUT chassis, and touch test equipment with other hand.

View attachment 142866

before:
View attachment 142867

after:
View attachment 142868
(file photos)

Good thing I just completed my QEW (Qualified Electrical Worker) training (again) the day before.
So I knew that when current passes through the chest, you should get a medical checkup.
And that AC in particular is good at scrambling ion polarities in cells of heart muscle.

Lesson learned, best practices:

1) Use keyed connectors on cable providing power and ground to DUT.
With Y-cable, branch off to banana cables to test equipment.
This way, chassis is not accidentally electrified.

2) Use a separate ground cable, perhaps with large alligator clip, as redundant ground.

3) Consider GFCI (RCD) to power DUT. In this case, wall outlet likely not effective due to UPS, so use portable GFCI suitable for voltage range.

What did medical do for you? How did they treat your problem?

 

[Hedges]

Initially, looking at the EKG. It had been very ragged at the redi-care clinic, which said I needed to go to the emergency room where I could be monitored. ER reviewed the issue on my registration and immediately brought me in from the waiting room for another EKG, which wasn't nearly as bad at that point.

I spent the first night in ER bed. My heart rate was racing high e.g. 160 and dropping low. I was given medication to limit the effect on heart rate. That dropped it excessively low, like under 50, so dosage was reduced.

Main thing they did was hook me to a monitor, which would have alarmed if I arrested. It did alarm repeatedly for heart rate.

After a few days things had settled towards normal. They had been considering a "Life Vest" wearable defibrillator.

LifeVest for Sudden Cardiac Arrest

A LifeVest is a defibrillator that can protect you from dangerous heart rhythms that cause sudden cardiac arrest. This removable device fits under your clothes.

my.clevelandclinic.org

It took a few days for the Echocardiogram operator to get to me, do a sonoscan. Based on that, I was in the normal range for left ventricle ejection percentage (something like 55% and above?) If it had been in the 35% range, that is where the wearable defibrillator would be indicated.

I also had same medication to take after discharge, and periodically had blood pressure and heart rate tested. Our home wrist cuff sometimes gave normal readings, matching what was taken at same time with arm cuff in clinic. But other times it gave scary high numbers, like 200/120 or something. I later found an arm cuff, and it was giving healthier readings. I now think the wrist cuff readings were flaky.

So overall, monitoring, sonoscan evaluation, medication.

I understand timing of heart rhythm when shocked is key to how it upsets. Mine affected the heartbeat but didn't stop it, maybe because very short.

 

[Supermo26]

Thank you for sharing that info.

 

[robbob2112]

Back 30 years ago while in the Navy I was calibrating 5 O'scopes on the bench. While I was moving them so the test leads would reach all I get a little zap. Being 19 and indestructable I lick two fingers, touch one to a ground on the bench and use the other each scope with a lite tap, tap, tap, zap, tap... someone had rewired the ac plug socket wrong and flipped the hot and neutral. Note: just about all our test equipment floated the neutral and didn't bond to ground, something about being on a steel hulled ship.

Same duty station I was repairing a radiation king console TV from the 70s for my first class petty officer (my boss).. I was probing around the power supply section and got my index finger across the leads from the flyback transformer....30kv...zap...burned an entry wound at the tip of my finger and again at the first joint....made my whole arm tingle for hours.

Next duty station in Guam.. I was AT2 rating/rank

Last story... working on a ES3-A aircraft....(squadron was VQ-5).... problem was the hydraulic actuator to lower the FLIR turret had a twisted shaft... the internal over torque sensor was tripped so no power to it. Can't get to the bolts to release it while it is up, normal procedure was lower and use bomb hoist to lower turret into cradle. I was in the powered load center with stainless steel safety wire pushed into the back of a cannon plug to trick it into thinking things are ok....but I had to push a second wire to jumper power to the relay to lower it only after a green light on the cockpit center console. I hit power any my arm muscles contracted until my elbow hit the back of the breakers...contract again and bloody my knuckles on something over near the cannon plug.. back and forth about 10 times before I could blink...

FYI- aircraft power on those and most Navy planes is 440vac 400hz.... makes for smaller components but it BITES.

 

[Nobodybusiness]

Back 30 years ago while in the Navy I was calibrating 5 O'scopes on the bench. While I was moving them so the test leads would reach all I get a little zap. Being 19 and indestructable I lick two fingers, touch one to a ground on the bench and use the other each scope with a lite tap, tap, tap, zap, tap... someone had rewired the ac plug socket wrong and flipped the hot and neutral. Note: just about all our test equipment floated the neutral and didn't bond to ground, something about being on a steel hulled ship.

Same duty station I was repairing a radiation king console TV from the 70s for my first class.. I was probing around the power supply section and got my index finger across the leads from the flyback transformer....30kv...zap...burned an entry wound at the tip of my finger and again at the first joint....made my whole arm tingle for hours.

Next duty station in Guam.. I was AT2 rating/rank

Last story... working on a ES3-A aircraft....(squadron was VQ-5).... problem was the hydraulic actuator to lower the FLIR turret had a twisted shaft... the internal over torque sensor was tripped so no power to it. Can't get to the bolts to release it while it is up, normal procedure was lower and use bomb hoist to lower turret into cradle. I was in the powered load center with stainless steel safety wire pushed into the back of a cannon plug to trick it into thinking things are ok....but I had to push a second wire to jumper power to the relay to lower it only after a green light on the cockpit center console. I hit power any my arm muscles contracted until my elbow hit the back of the breakers...contract again and bloody my knuckles on something over near the cannon plug.. back and forth about 10 times before I could blink...

FYI- aircraft power on those and most Navy planes is 440vac 400hz.... makes for smaller components but it BITES.

Fly backs are evil.

I had a monitor open years ago working on it.

It was on my bench for a few day’s waiting on parts.

Phone rings and I’m talking and taping my screwdriver on the desk.
Tap the Top of the fly back because the wire was off and zap!!

I thought I had already shorted it but nope.

Bit a hole in my tongue and it actually shorted out the phone I was on.

I was like 24 so got stitches in my tongue and never told them about the shock.

Dumb but You think you’re pretty much invincible at that age.

 

[JS43]

Back 30 years ago while in the Navy I was calibrating 5 O'scopes on the bench. While I was moving them so the test leads would reach all I get a little zap. Being 19 and indestructable I lick two fingers, touch one to a ground on the bench and use the other each scope with a lite tap, tap, tap, zap, tap... someone had rewired the ac plug socket wrong and flipped the hot and neutral. Note: just about all our test equipment floated the neutral and didn't bond to ground, something about being on a steel hulled ship.

Same duty station I was repairing a radiation king console TV from the 70s for my first class petty officer (my boss).. I was probing around the power supply section and got my index finger across the leads from the flyback transformer....30kv...zap...burned an entry wound at the tip of my finger and again at the first joint....made my whole arm tingle for hours.

Next duty station in Guam.. I was AT2 rating/rank

Last story... working on a ES3-A aircraft....(squadron was VQ-5).... problem was the hydraulic actuator to lower the FLIR turret had a twisted shaft... the internal over torque sensor was tripped so no power to it. Can't get to the bolts to release it while it is up, normal procedure was lower and use bomb hoist to lower turret into cradle. I was in the powered load center with stainless steel safety wire pushed into the back of a cannon plug to trick it into thinking things are ok....but I had to push a second wire to jumper power to the relay to lower it only after a green light on the cockpit center console. I hit power any my arm muscles contracted until my elbow hit the back of the breakers...contract again and bloody my knuckles on something over near the cannon plug.. back and forth about 10 times before I could blink...

FYI- aircraft power on those and most Navy planes is 440vac 400hz.... makes for smaller components but it BITES.

A buddy kept getting shocked and hard zaps from a black box on a Prowler. He never did find out why but he ended up in sick bay for a couple days while they monitored his vitals.

 

[Hedges]

3rd time's a charm?

@Rednecktek let me add to your list:

if a 48V battery can be lethal, how about a 40V panel?

Batteries over 24V, start getting into the "dangerous" area and you should know what you are doing. How about a solar panel that has 40 volts (and about 10 amps)? If not, how many in series before it gets "very dangerous"?

diysolarforum.com

480VDC - squeals like a stuck pig.

I was rearranging wires in a combiner box to test an inverter, using MC3 connectors. I confirmed 480Voc, so wouldn't be interrupting current. My thumb touched an exposed conductor while I knelt on the ground. I felt a hard vibrating shock in my right arm. I squealed for a while before formulating words that could be censored.

Thumb hurt, seemed to have some numbness, seemed weak to use. Right arm was sore. I felt light headed a few minutes later, but probably adrenaline, not heart rhythm.

This time I wasn't under Worker's Compensation, didn't want a six-figure bill, so I toughed it out and treated myself. To a nice cup of French Press coffee. Lay down for a few minutes, then got up and went back to the project. Half a day has passed and I'm still kicking, so won that bet.

The culprit (my carelessness), a set-screw wire nut that I used to join a stripped wire to a too-long crimped terminal:



The entry wound (bloodless, nicely cauterized):

 

[Mattb4]

Mr H!

I do thank you for reminding people of the danger of working around voltages and especially high voltages. However it is not really necessary to serve as an example of what can go wrong. Leave that to the younger folks to do.

I hope your have a quick recovery.

 

[robbob2112]

3rd time's a charm?

@Rednecktek let me add to your list:

if a 48V battery can be lethal, how about a 40V panel?

Batteries over 24V, start getting into the "dangerous" area and you should know what you are doing. How about a solar panel that has 40 volts (and about 10 amps)? If not, how many in series before it gets "very dangerous"?

diysolarforum.com

480VDC - squeals like a stuck pig.

I was rearranging wires in a combiner box to test an inverter, using MC3 connectors. I confirmed 480Voc, so wouldn't be interrupting current. My thumb touched an exposed conductor while I knelt on the ground. I felt a hard vibrating shock in my right arm. I squealed for a while before formulating words that could be censored.

Thumb hurt, seemed to have some numbness, seemed weak to use. Right arm was sore. I felt light headed a few minutes later, but probably adrenaline, not heart rhythm.

This time I wasn't under Worker's Compensation, didn't want a six-figure bill, so I toughed it out and treated myself. To a nice cup of French Press coffee. Lay down for a few minutes, then got up and went back to the project. Half a day has passed and I'm still kicking, so won that bet.

The culprit (my carelessness), a set-screw wire nut that I used to join a stripped wire to a too-long crimped terminal:

View attachment 194964

The entry wound (bloodless, nicely cauterized):

View attachment 194966

I learned my new thing for the day, I haven't ever heard of 'set-screw wire nut'

 

[Hedges]

These things are "Ideal"

IDEAL Model 11 Set-Screw Wire Connector (100 per Box) 30-211 - The Home Depot

Ideals set screw wire connectors ensure a vibration-resistant splice, perfect for applications near motors or other vibration. The solid brass sleeve insert allows wire ranges 22 AWG - 10 AWG. Each package

www.homedepot.com

Unfortunately only a couple moderate sizes.
For larger wires I have to use blocks or Polaris.

I've used quite a few set-screw wire nuts now, permanent wiring, test setups, and at work. Easier to redo because they don't get the strands tangled together.

 

[robbob2112]

These things are "Ideal"

IDEAL Model 11 Set-Screw Wire Connector (100 per Box) 30-211 - The Home Depot

Ideals set screw wire connectors ensure a vibration-resistant splice, perfect for applications near motors or other vibration. The solid brass sleeve insert allows wire ranges 22 AWG - 10 AWG. Each package

www.homedepot.com

Unfortunately only a couple moderate sizes.
For larger wires I have to use blocks or Polaris.

I've used quite a few set-screw wire nuts now, permanent wiring, test setups, and at work. Easier to redo because they don't get the strands tangled together.

So many new toys... the last time I needed to join larger wires I used split bolts and friction tape.

 

[Nobodybusiness]

So many new toys... the last time I needed to join larger wires I used split bolts and friction tape.

Polaris lugs..

 

[OffGridForGood]

These things are "Ideal"

These things are Marrettes

I've used quite a few set-screw wire nuts now, permanent wiring, test setups, and at work. Easier to redo because they don't get the strands tangled together.

These things are Marrs

https://en.wikipedia.org/wiki/Twist...ade name for such,actual brand of the product.

William P Marr.
he didn't have the "shot through the heart" leading up to his invention, his accident was molten lead!

 

[Hedges]

"The process was time-consuming and potentially dangerous. Marr was injured when he spilled molten solder on himself. Seeking a safer, more efficient connection method, Marr, working in his home workshop, developed the first pressure-type wire connector. In 1914, he produced a set-screw version, the forerunner of the present-day twist-on connector used throughout North America."

Guess I like the older stuff better.

 

[robbob2112]

These things are "Ideal"

IDEAL Model 11 Set-Screw Wire Connector (100 per Box) 30-211 - The Home Depot

Ideals set screw wire connectors ensure a vibration-resistant splice, perfect for applications near motors or other vibration. The solid brass sleeve insert allows wire ranges 22 AWG - 10 AWG. Each package

www.homedepot.com

Unfortunately only a couple moderate sizes.
For larger wires I have to use blocks or Polaris.

I've used quite a few set-screw wire nuts now, permanent wiring, test setups, and at work. Easier to redo because they don't get the strands tangled together.

So, on the set screw type don't you still have a problem with thermal expansion and contraction causing the screw to loosen? I.e. do you have to come back later and retorque?

 

[Hedges]

I suppose you could.
But since I don't have a torque screwdriver yet I just mash the hell out of them.

Could it be wire nuts with spring inside are superior, because the spring gets unwound a bit during assembly, and maintains pressure?

But set screw lugs are used everywhere. I just torqued and retorqued the meter socket connections to 3/0 wire. I'll never have access to them again once PG&E connects the service. The wires exiting bottom side have a J shape, so by pulling on them I got some wiggle/rotation and was able to continue turning at 20.5 ft. lbs., but the wires coming straight down from above I can't. So I do worry about them.

 

[OffGridForGood]

So, on the set screw type don't you still have a problem with thermal expansion and contraction causing the screw to loosen? I.e. do you have to come back later and retorque?

"technically" you are supposed to twist the conductors together first, then install the Marr with the set screw, and thread on the cap. But like @Hedges said, the beauty of the Marr connectors is being able to easily disassemble them, so if I am expecting to un-do a connection I don't twist them together. I expect the twisting-together part is supposed to be the main conductive connection between the wires, and the set screw is just to secure the threaded ring sufficiently to hold the cap on.

 

[robbob2112]

"technically" you are supposed to twist the conductors together first, then install the Marr with the set screw, and thread on the cap. But like @Hedges said, the beauty of the Marr connectors is being able to easily disassemble them, so if I am expecting to un-do a connection I don't twist them together. I expect the twisting-together part is supposed to be the main conductive connection between the wires, and the set screw is just to secure the threaded ring sufficiently to hold the cap on.

I would expect the twist does the wire to wire contact and the ring squeezes them together and keeps them in good contact. Without the twist I wonder how good the contact is?