Stupid Reasons to Blow Circuit Breakers

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On 12/5/2010 3:42 PM, snipped-for-privacy@aol.com wrote:

In my experience, high frequency AC hurts worse than any other shock I've had. The horizontal output of old tube type TV sets can make you feel like you've been turned inside out. It goes to the bone. :-)
TDD
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While working on the LORAN transmitters I mentioned above, I witnessed a guy come as close to death from electrocution as you can get.
When you removed any of the 3' x 3' panels from the side of the transmitter, a spring loaded interlock grounded all high voltage. If you then removed any of the grounded bus bars from the big oil filled caps, you were required to attach a grounding strap across the terminals to prevent the caps from charging back up from the energy in the room. (There was always 1 live transmitter in operation while we worked on the standby)
A tech had moved a cap to the workbench, shorted it out, and then later put it back into the transmitter. He removed the grounding strap, then got distracted and didn't hook up the bus bars. After the cap had been sitting open for a few hours, he stuck his upper body into the transmitter and reached across the cap. His chest came in contact with the 2 terminals and it threw him upward into the bottom of the shelf above, which bounced him back down onto the cap, which - not having been fully discharged yet - threw him back up into the upper shelf one more time.
This time he came down on the cap and sort of slithered to the floor, almost unconscious and very bruised and battered.
We were 60 miles above Nome, AK, so we had to call in an air-taxi from a nearby village ("nearby" was 15 miles across the Port Clarence Bay) to come get him and take him to the hospital in Nome.
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On 12/5/2010 5:04 PM, The Daring Dufas wrote:

I was going to post the same thing. I've worked on a lot of video game monitors. They all have a hot chassis with about 130VDC to ground (always run them through an isolation transformer) but from that hot to the HOT (horizontal output transistor) is what gave me quite a few burns and the smell of burning flesh. I think it does hurt more than any other shock, and damn, it grabs you and doesn't want to let go. Most of the shocks I've encountered ran from one hand to the other... with my heart in between. Either I'm lucky as all hell or that thing about the one hand behind the back and the current going through your heart is just a story.
I think my worst ever shock was _only_ 120VAC from my pliers with sweaty hands, onto a hot wire, through me and to ground through my sweaty forehead. It went through my head, I did see a very bright flash, I suppose when it went through my eyes and the nerves for them. I had the machine unplugged and a good Samaritan plugged it in for me.
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On 12/5/2010 9:00 PM, Tony Miklos wrote:

One of my little brothers was very helpful by cutting off the little plastic nub made when my insulated pliers were dipped in plastic. I suppose he thought it should be more symmetrical. I got the crap zapped out of me when I grabbed a hot wire with them.
TDD
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I bet. I've had the 110 a/c tickles, but the worse was a 250VDC elevator control circuit. The elevator guy swore it was off and I stupidly believed him.
I too woke up about 8 feet across the room.
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re: "...and I stupidly believed him."
What was it that Ronald Reagan used to say?
Oh yeah...
Trust, but verify.
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On 12/6/2010 6:31 PM, DerbyDad03 wrote:

Always! I have testers for high, medium and low voltage, those devices will touch a circuit before me or the grounding strap. :-)
TDD
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wrote:

Yeah... Having done a lot of lighting work in commercial buildings, I always touch the hot wire in the fixture to a ground before I work on anything inside it (for other than re-lamping) -- this does two things: one, it either lets me verify that I was successful in locating the correct circuit and two, if I did not locate the correct circuit, I now have a tripped breaker to help me locate the means to re-energize the fixture after I finish working on it to know where to kill it the next time...
It is often difficult to locate the correct breaker for a light fixture that has either burn out lamps or a non functional ballast... You have no positive indication that the power is off as the light was not lit when you started...
~~ Evan
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On 12/6/2010 10:38 PM, Evan wrote:

Well, there is a new requirement for disconnects in light fixtures now. It's a little plug an socket set that you just unplug for service. It seems a lot of maintenance people were getting hurt or killed while servicing 277 volt lighting. Just about every electrician I run across on a job will cut the things off and use a wire nut. SOP for me has been the installation of a fuse holder and fuse. One on the hot wire for 120 volt ans two for 277 volt lighting. It serves a dual purpose of disconnect and keeping the magic smoke inside the ballast. I see from your post that you use the Jesus method to find circuit breakers. :-)
TDD
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On 12/4/2010 9:18 AM Roy spake thus:

Dunno. My last "tickle" was actually the worst jolt I've ever gotten, one I won't soon forget.
Was working on a friend's shop in a commercial space in San Francisco, installing lights. Somehow contacted two wires that I *thought* were disconnected but weren't. What I didn't know at the time was that these weren't 120 volts, but instead were 277 volts.
Big difference. Big buzz. I was on a stepladder at the time, and am *very* lucky I wasn't thrown clear off.
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On 12/5/2010 4:32 PM, David Nebenzahl wrote:

I heard of a bald electrician who was working on 277volt lighting when he raised up while making a connection and his bald head touched the fixture. R.I.P. A lot of guys are hurt or killed working on 277volt lighting circuits because they're not careful enough.
TDD
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wrote:

I've had more than I can count, and I become more careful with each one.
I've gotten them from electric fences. I've gotten them from automotive ignition systems (capable of over 60,000 volts) I've gotten them from electronics - including TV High voltage transformers I've gotten them from 115 and 230 volt AC mains
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re: "I did vaporize in half a pickup dipstick..."
As part of the Safety Training for new arrivals at the Loran transmitter sites I mentioned earlier, we came up with a way to keep the non-electronics personnel out of the transmitter building.
All we needed was a huge oil filled capacitor, a Hi-Pot power supply and a Dead Man stick - AKA a grounding rod: a long wooden handle with a metal hooked rod threaded into it and a braided grounding strap attached to the rod. It's main purpose was to tap around inside the transmitters once they were turned off to make sure there were no stray valotages hanging around. Their secondary purpose was to hook the clothing of anyone unlucky enough to get stuck inside a powered on piece of equipment and pull their dead, smoking carcass out so we could get back to work.
Anyway, as part of the newbie tour, we'd let the guys peek into the transmitter room and then close the door. We'd then explain to them that the machines on the other side of the door wanted to kill them and they they should never to go into that room without a journeyman transmitter tech.
Then we'd take a big oil filled cap, hook the grounding strap of a Dead Man stick to one terminal, use a Hi-Pot to charge the cap up to a couple of KV and, right after turning the lights off, we'd tap the rod to the other terminal, shorting out the cap. The resulting CRACK and sparks were enough to convince them that they didn't want to hang around inside the transmitter building.
Well, one time we got a little ballsy and charged the cap up a bit higher than we normally did. When I tapped the rod to the terminal, not only was there a CRACK that sent even the most seasoned of us running, it split the hardwood handle and shot the metal rod halfway across the room.
After we calmed down, someone realized that there was a good chance that the cap was not fully discharged, so he grabbed another Dead Man stick and shorted it out again. Good thing too. We got a decent CRACK out of the second try, but nothing like the first.
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On 12/6/2010 2:08 PM, DerbyDad03 wrote:

Me and the other broadcast engineers I know refer to them as "Jesus Sticks". When you ground something with it that has a high potential, you shout "JESUS!" when it explodes. The other explanation is that the safety device keeps you from going to Jesus but all the guys I know who work on electronic gear are all going to meet the other guy. :-)
TDD
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On Thu, 2 Dec 2010 13:14:42 -0800 (PST), " snipped-for-privacy@aol.com"

ground was much lower resistance than through your body. You MAY have been electrocuted 0 more likely you would have gotten a pretty serious shock - and quite possibly not even a "tickle"
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On Thu, 02 Dec 2010 19:09:17 -0500, snipped-for-privacy@snyder.on.ca wrote:

Ground itself has significant resistance -- that's why grounding rods require a lot of ground contact, a great deal more than the tiller blade. And it's not certain that the tiller blade would even have good ground contact. And unless the grounding is adequate to reduce the voltage potential, it does not affect the shock given. Since the poster hit an entrance cable, the breaker was at the transformer and was probably several hundred amps at least.
1 mA is enough to feel, and 100mA is enough to kill.
Human body resistance may vary from 1000 ohms (wet hands) to 100,000 ohms. (Numbers from a Wikipedia article, so take it for what you think it's worth.) Assuming a 100V shock (one leg), at the highest resistance the shock would be felt, and at the lowest resistance, electrocution is a distinct possibility.
Edward
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On 12/2/2010 12:48 PM, DerbyDad03 wrote:

My favorite method of popping a circuit breaker, I have seen this.
Wire the light switch and the light in parallel. Need to turn off the light, just throw the switch. Turning it back on is slightly more involved.
Jeff
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