Sparky's the name, dead shorts are my game

[ohland]

I saw one of the clearest examples of a dead short that I have ever seen. The outdoor pop machine was daid to the world, so my Dad (of course) sicced me on it. Every time I threw the breaker for the exterior outlet when the machine was plugged in resulted in an immediate trip. Nothing plugged in, no trip. Fan plugged in worked just fine.

Went to Ace for a right angle plug, went back to the rifle club and started to dissect the original plug. Didn't take long, as soon as I pulled the outer sheath back, I saw where the hot, neutral, and ground conductors were bare. Hot n neutral conductors had welded about half their strands...

Opened the replacement plug and prepped it for attachment, and I found out that the insulation on ALL three wires was brittle. Couldn't strip the sheath back far enough to find good insulation, so after a foot, I gave up. As soon as the fiber packing material was stripped from the conductors, the insulation started to crack.

Told my Dad that the cord needed to be replaced.

[SciFiJim]

Ace should have replacement cords. Or you could use a power cord from a computer. It should be able to handle the current.

[MaryB]

Computer power cords won't handle compressor duty, most are 18 gauge. But heavy duty 3 wire cords can be found at any place carrying electrical stuff.

[Frank46]

I got a better one for you. Worked in an oil tank farm and we had just installed a new mechanical seal on a 300 hp motor 480 volts and starting amps would be close to 600 amps. We had some reps from different companies with us and they wanted to see how these seals worked. Well the monkey flipped the start switch. Unknown at the time vibration had finally worn down the insulation on one leg of the wires and grounded to the inside of the elbow. Huge bang and everyone except me and the foreman I was with. The other guys beet feet. Frank

[Catshooter]

Shorts are an interesting study. The amount of current (amps) that can actually flow during a short can be quite shocking ( ).

Ohland you could have been looking at 200 amps. It's brief, ah, we hope, but still can be very destructive.

Frank, the starting current on that 300 horse was probably much more like 1,800 amps or so. The current during the short with three phase 480 can easily be over 20,000 amps. It depends on a lot of factors. Deadly stuff.


Cat

[farmallcrew]

I used to be a Appliance delivery guy, and i knew my partner from going to auctions, he worked for an auctioneer, he was an auctioneer, and he has his old man's meat shop.

Every house was different. Sometime we had to make the receptacle correct, from the homeowner tinerking with it. Some places had just bare 220 solid copper wire going into the dryer- those were the SOB'S because per law were supposed to have a receptacle on there in case of fire. And i was the smaller of us 2, so i always got those kind of jobs, nasty basement floors.

Got thrown off a new dryer in a new house, i touched the hot and ground on the cord prong while jamming it into the receptacle, i was lay on top the dyer then next 'against the wall 6 feet back. All i hear from my partner was "*** was that" i said "i don't need to worry about irregular heart beat and i don't need the defibrillator, but i know when we are done here, i need a cig." he came up and we laughed.

Ive replaced several cord ends on the job and at home. Always hated, replacing an end, using the extension cord in the yard, then forget its out there and start to mow. URGH. lol

[Handloader109]

My favorite grounding, was helping replace powered roof vents for a contractor friend of mine. He didn't like to mess with electricity, so while I worked PT for him, this was one of my jobs. First mistake was to assume I could successfully work on it without cutting power. No easy way to determine breaker in older home, didn't want to cut entire house power. SOOOO, work hot. Never touch the black wire right? In this case, touching white was just as bad as black. Fan was burnt up, had been wired 220V, not std 120. Shocked myself three times before determining there was a problem. We did find breaker and rewired to 120. Never assume old wiring.

[Dale in Louisiana]

I've been working in the industrial and utility electrical power arena since 1977. I've seen a whole rainbow of short circuits, from little bitty ones blowing a two-amp control fuse to one at 230,000 volts that burned the twelve-foot moving contacts off its disconnect switch.

It all has the potential (Hah! I slay me!) to be lethal. That 120-volt light switch in your living room will put your butt in the dirt if things go wrong. The energy released by industrial power levels can roast you to a turn six feet away, even if you DON'T touch things. Compared to dying from burns, I'm thinking electrocution is a better way to go.

It's best that you KNOW what you're doing before you mess with electricity.

dale in Louisiana

[ohland]

It all has the potential (Hah! I slay me!) to be lethal. dale in Louisiana

I keel you!

Old man called another club member who also works for the local Pepsi distributor. He ordered new cabling for it. Darn thing weighs about 300 or so pounds, I could not budge it. That is when I let someone else fix it.

[MaryB]

I watched(from a safe distance) when a substation wasn't switched out properly, load was removed before they removed the input and the back emf lit up the sky.. arcs everywhere some 30-50 feet long.

[gew98]

I worked at a machine shop years ago where they had a home made inverter to 3 phase. They had to start three milling machines one after the other to start the old surplus 20 foot Navy Lathe as it's inrush current draw was big !. Wprked at a motor repair shop that had a similar dilemma and when we had to test 575 and 950 volt motors we had to step the voltage up just right or bang...knock out the power on the street !. I have often had to wire pony threaders direct to the temp panels as they trip GFCI's every time.... and hide it from the safety nazis.
Had a few times where 277 lights got me...those garbage stab on connectors do pop out !! and will let you know it.

[shooterbob]

Not a short but funny story...I worked at a granite quarry and I was back in a shop by myself cutting 20x12 slaps into rough headstones with a wet diamond saw. I sat it a little shack and on the outside of the shack was a coke machine. I was sitting there one day and all the sudden BOOM!! A loud explosion.goes.off close to me. I'm wearing hearing protection and it was still loud. I go outside and look around thinking the guys are playing some joke or something...nothing is out there. Another hour goes by and it happens again. And again nobody's there. After the third time I go get my supervisor and were looking around and we both turned the corner to the coke machine and we watched a ball of fire erupt around it and again the explosion. We finally found out there was a gas line running in the wall and it was leaking and pooling around the coke machine and when the compressor came on it was igniting the gas! Talk about people clearing buildings fast, I have ear damage now that I wonder if that caused...it couldn't have been all the guns over the last 20 year's

[Bullfrog]

There are plenty of pre moulded cords out there to choose from. A dryer cord will handle 30 amps and is 10 ga. A dishwasher cord will handle 20 amps and is 12 ga (typically, but check ).

Just had a dead short at work on a 200 amp bucket in a 480v switch gear and to quote my favorite movie "Big badaboom!"

Oh also what creates the "brittle" insulation is an increase in heat caused by resistance. It is probably either too small a wire to handle the current draw or the motor is struggling and sucking more juice than it should. I would check the compressor to be certain it is not staying on too long, such as when placed outside in the hot sun all day

[doc1876]

oh man, I had 277 get me one time, my elbows hurt for a week! that was a lesson learned. Bullfrog is right, and if you want to do it easy and safe, get a 10 ga extension cord, and cut off what you need, hook it up and go.

[dragon813gt]

This a tiny one that I work on.


I never take electricity lightly. I got lit up by 600v 3 phase, only one leg, once. It bites like a dog. But AC is child's play compared to DC. I work on a lot of VFDs and their power down time can be up to half an hour. If you reach into one and the capacitors are still charged you are on for the ride and you will be burnt up. AC will throw you while DC holds you on. Neither is fun to get hit with.

[popper]

My bro worked for Westinghouse, fault testing LARGE motor switch gear. They would fault the motor and it tossed the armature to the next building a couple times. Had a GM that switched 400 cycle 440v 3 phase alt & normal busses (motor ran 80 tons in a coke-bottle mag). Vaporized the buss bar all the way to the the boiler room. HVDC is bad, took a hit from ~ 900 when testing bleeder circuit, index to index finger. Got to play with some one farad supercaps a couple years ago. Used 1/2" ring lugs for a connection. Dad got to console a new widow when one of his highliners got fried. And mom thinks shooting boolits is dangerous. A lot of funny stories here, only if nobody gets hurt.

[Newtire]

This a tiny one that I work on.


AC will throw you while DC holds you on. Neither is fun to get hit with.

220 V A/C Electric Dryer...It holds on-trust me!

[Springfield]

I was helping the electrician(in name only!)at work once. He had stripped out the bolt installing a 440 volt breaker switch. He decided the best thing to do was drill it out and remove it with an easy out. Unfortunately he drilled through the broken bolt into the buss. HUGE sparks and half the building went dark, shut down a couple assembly lines. The security guy had been watching us on camera,and he came running over with a fire extinguisher. He was shocked to find out we were OK. Apparently the bright light from the sparks had caused the camera to flare, and it looked to him like were had been engulfed in a huge ball of flame! I saw the recording later, it was pretty impressive. I then refused to work with that electriciaon, turns out he had never had any formal training and was dangerous to be around.

[ohland]

Oh also what creates the "brittle" insulation is an increase in heat caused by resistance. It is probably either too small a wire to handle the current draw or the motor is struggling and sucking more juice than it should. I would check the compressor to be certain it is not staying on too long, such as when placed outside in the hot sun all day

The rifle club uses (FAIK) hand-me-down pop machines. That plus the outside one always froze over when it was very humid outside. That little "cube" coil at the bottom of the machine would be solid ice.

Not that I care enough to verify the cable size, but it appeared to be 12AWG. Not totally sure what the conductors are made of, they were pretty grungy from oxidation.

The outside machine is on the black powder hootch breezeway, and there is a couple good sized pines shading it. No idea where the machine came from before.

[Dale in Louisiana]

This a tiny one that I work on.


I never take electricity lightly. I got lit up by 600v 3 phase, only one leg, once. It bites like a dog. But AC is child's play compared to DC. I work on a lot of VFDs and their power down time can be up to half an hour. If you reach into one and the capacitors are still charged you are on for the ride and you will be burnt up. AC will throw you while DC holds you on. Neither is fun to get hit with.

Pfffft! biggest motor I worked on was 30,000 horsepower, the main air compressor at an air liquifaction plant. It ran on 13,800 volts.

We have a bunch of 22,500's in gas compressor service with my current employer.

In a previous employment, I had some part in the care and feeding of a 600-megawatt generator. That's roughly 800,000 horsepower, but it's going out instead of in.

Electrical power is fun stuff.

dale in Louisiana

dale in Louisiana