A truly SHOCKING tale of electrified PCs Welcome back to On-Call, our soon-to-be-less-occasional look at the odd things Reg readers have experienced when being called out to client sites at odd times. This edition features a reader called Jon's adventures on a day trip to Belgium in the 1980s. The trip was the first time Jon had ever flown commercially, and he …
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Sounds like a similar situation with domestic PME (Protective Mutiple Earth) main systems where the earth and neutral are basically the same. Often found where mains is delivery directly by overhead wire.
All conductive surfaces have to be earth bonded, which means that they are connected to the neutral line.
Any failure of the neutral conductor into the house effectively makes all those surfaces live through any switched on device.
Makes a good case for a local ground spike.
@skelband;
Exactly the situation we have in most of Spain where little or no distinction is made between earth and neutral, it is very common to lean against the sink unit in a Spanish kitchen and then rest your hand on the cooker but not for long as invariably you will get a substantial belt!
To date I have worked on half a dozen places where there was no earth spike/ spike corrode away/spike driven less than 6" into the ground.
Whenever I help friends to move into a new apartment I usually go around with a multi meter before getting involved with metal fittings or plumbing.
@Chris G
It was a standard practice on the continent up to the 90-es to have _NO_ _EARTH_ in apartment blocks. If you dig an old socket from 80-es or earlier with the original packaging you can see that indicates that you are _SUPPOSED_ to cross connect earth and neutral. This is also the standard of wiring in old apartment blocks which have only 2 core cable. This funnily enough works - if everything is wired this way. The problem starts when someone upgrades the system and leaves the ground disconnected so it can float and end up being offset from neutral.
It was a standard practice on the continent up to the 90-es to have _NO_ _EARTH_ in apartment blocks.
Exactly. Not a single home I've been in has ever had any Earth wiring installed, ever, around here - some of the sockets may or may not be "3-pin" but sure as hell nothing has an actual third wire... On a totally unrelated note, I'm now fully trained on a subconscious level to NEVER touch the media box's chassis when I'm plugging / unplugging the cable TV coax or the RCA to the TV with my other hand - guess why...
Grounding to a water pipe -- used to be a common practice. My first house, built in 1939, bought by me in 1977, had been replumbed in the basement from the original steel pipe to copper, though only where it was easy to reach (in the walls the original pipe was left.) The electrical system had been grounded to a cold water pipe, and the original clamp, sized for the larger diameter steel pipe, was left hanging loosely on the smaller diameter copper.
It got better. The 60 amp mains panel, with no master shutoff, was right beside a metal shower enclosure that had been added in the basement, so if you worked in that panel (live of course) you were right beside a good ground. All the 3-pin outlets added in that basement were ungrounded. You could measure an induced voltage of about 30V between ground and neutral in the furthest outlet. One outlet had the hot and neutral reversed.
" Grounding to a water pipe -- used to be a common practice."
Same in Oz. Copper or steel pipe buried in the ground made perfect sense from an electric perspective. Then unplasticised PVC pipe was introduced. Naturally it got used for repairs by plumbers in existing installations with the unexpected result that the (electric) ground was now isolated from the (dirt) ground by the nonconducting section of uPVC. What I suppose we might call a domain problem. Plumbers and electricians are different trades.
I still remember almost a year's worth of quarterly water bills in the mid 80s begging consumers to get a sparky to check that any plumbing work hadn't compromised their dwelling's electrical safety.
It is enough to have one of those on a coax network for the life of the admin to become a bundle of fun as it leaks onto the coax. I nearly killed myself a couple of times during the couple of years when I had to maintain a coax based LAN in an educational institution in the mid-90-es.
The problem was not so much in the electrocution (as one would expect). The network repeaters were located in old no longer used "cubby" offices along the central core of the building - one on each floor, on a shelf near the risers. So far so good, right? Not if there is a window right behind your back. The kick which 90-200V leaking onto the ground of the coax gives you is just the right size to try to do a sommersault back through the window behind you. After a near miss and a couple of days of swearing and trying to find the culprit I just grounded the coax ground across a 10kOhm resistor on each strand and that was the end of it.
The alternative is that in many places someone will have used the earth as a neutral, laying next to the pool on my mates lawn I had the sensation of a slight tingle after the trickle irrigation had been running. With everything off the earth spike was getting 90v when we tested it.
Half the kitchen was wired to an earth neutral.
One house I bought had originally been wired up in Edwardian times & only had bits & pieces of wiring added after that, none of it with the benefit of any sort of earth connection. Some of the main bedroom fittings had wiring brought down from the roof space in metal conduit (the lighting wiring was in wooden conduit). The earth wires from the fittings were simply twisted round the top of the conduit. On lifting some floor boards in one of the children's bedrooms I discovered that the earth of the sockets there was a six inch nail driven into the mortar of one of the walls. It got worse - in the other child's bedroom the earth was a six inch nail driven into a joist.
A BA's lunch served to me over 30 years ago still stands out in my mind. The menu said "Omelette", but I think they actually meant Omelette boiled in brine. Impressively awful, I suspect that much of the derision heaped upon British cuisine may well be caused by BA's Omelettes being so bad that visitors to blightly can't remember anything else when they get home.
Having experienced the joys of electricity, I will definitely give a thumbs-up for synthetic carpets, non-conductive shoes etc which have meant I have only ever acted as a capacitor under charge/discharge rather than 'path to earth'. Numerous occasions but indoors, no lawnmowers.
For those who have not been enlightened in this way, mains (or more generally, AC) power has a very distinctive feel to it that is very much not the same as static. Plus as long as you are not 'the path' then it keeps going until you go 'ow fck' though this may not actually be the most advisable method for distinguishing between the two.
One night at my parent's country place, when I was much younger, we learned that the old electric blanket was missing some insulation on the wires inside the blanket.
This was discovered when my mother checked on me in the night and felt my skin tingling.
I woke up feeling full of energy. :)
I was changing a light to a ceiling fan light in my Aunt's kitchen. Dropped the MCBs one by one until the light went out. Marked the circuit breakers and "locked" off the circuit with duck tape. Went back upstairs to work on the light... felt the hairs on the back of my hand go up... checked it with my mains tester. Live.
Some moron had taken the lighting ring out of one MCB, round the loop and back into a DIFFERENT MCB, and on top of that, they'd switched on the Neutral! Cost of rewiring her 9 bedroom house... £7,000
A colleague was called out in the middle of the night. His manager said "Get down to **** quick - they're in the shit". This terminology was a little surprising as the man was normally polite in his language. On arrival the modem rack was covered with a foul liquid oozing from the ceiling.
The customer had had a blockage in the ladies' toilets. Caustic solution had failed to clear it - but a drainage rod had finally given a satisfactory reaction. Flushed water disappeared nicely. Unfortunately the 100mm plastic waste pipe had now become disconnected at a rubber-sealed junction - in the false ceiling above the comms room.
A customer in a new building in Africa complained that the mainframe computer room air conditioning wasn't fully effective - even though the design had seemed sufficient. The air conditioning units were big and tall - standing against the wall. They took in warm air at the top and blew out cold from the bottom - which was below the false floor level. An extra air conditioning unit was then fitted - which fixed the problem to the customer's satisfaction.
The mystery was finally solved when installing a software upgrade. The computer operators lifted a floor tile - and offered cold beer and watermelon. Their not inconsiderable stash was almost blocking the outlet vent of an air conditioning unit.
2 burn in ovens side by-side, voltage 320 AC or thereabouts. Felt a zap, not extreme shock, but noticeable, when leaning against one oven and touching another. Problem was a miswiring on the line AC inlet. Why only a small zap and not a major ZAP? The thick paint was a partial insulator.
One of the oldtimey weather machines--the kind that spooled wet paper across a drum; the transmitter was much like an old style slow scan TV with tubes. Problem was intermittent noise spikes. Tech found high voltage on the chassis (as in OUCH!, as in 40KV!) Equipment was about 50' from the antenna of a local radio/TV station with something like 50KW of power. No idea what the solution was.
The Systems Test area's 3 phase colours had been wired incorrectly. As it was a continuous production area no one had ever corrected the problem - which the local electricians merely accommodated when new equipment arrived.
Then one day a new set of replaceable disc drives arrived - and for some union reason had to be wired up by electricians from their factory over a weekend. It was several days before the new disk drives had a problem. They happily ran all the engineering tests - but refused to load the operating system that was generated on another machine. After much swapping of disks on a drive the penny dropped . They were rotating backwards - but the symmetrical read/write heads still flew ok. The off-site electricians had wired them up trusting the room's cables' colour coding.
That story has been repeated by people for many locations - so it was not an isolated problem.
A similar problem on another site had a card punch mechanism going backwards - with considerable damage to its innards.
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While managing a radio station at an unnamed Canadian University we decided to purchase a group of new PCs, and chose to do so through the university computer services - they're experts, right?
Imagine our surprise a couple of months later when they started to fail.
"Fail" meaning loud noises, smoke, and a great long blast of sparks out the back of the PSU that honestly looked like a roman candle!
Thankfully that was the PC sitting on the desk in front of me, and not one in an unoccupied studio!
I found some Italian built light boxes in a photo studio where the earth was terminated at a 6mm brass stud.
Sadly, the stud was mounted on hardboard, offering no protection for the rest of the metal light box!!
Also, (to save money) a G.U.S warehouse had its picking cranes wired up with single phase isolators, despite using 2 phases to provide the power to the crane controls.
A foreman found this out the hard way after isolating the cab and sticking his hand into a faulty heater. From then on, his nickname was Scorch.
I remember a lecture on electrical safety in the radar worksop when I was an RAF apprentice.
We were sat in a typical RAF wooden hut wearing our brown workshop coats and the lecturer was going on about capacitors and how they could hold a charge long after the power had been removed. So much so that in a radar set there was enough to kill.
He explained that in order to be safe you had to discharge any capacitors and then went about explaing the correct ways of doing so.
All the time he had been talking he was playing around with a 1 inch ring-spanner (probably AF, but could have been Whitworth in those days!).
Suddenly he 'accidently' dropped it. It fell into a wooden box that had been in front of him for the past half-hour or so.
The was a God-almighty flash and bang that woke everyone out of their afer-lunch doziness.
"That's what can happen if you don't pay attention" he said, donning a pair of thick rubber gloves and retreiving the spanner. He held it up to reveal that a sizeable piece of it was missing - vaporised he said, just like flesh would be - if you survived the incident!
In the 1960s there was an industrial control machine which contained a large Ni-Cd battery as a UPS. The very beefy connectors were held in place by large hexagonal nuts. The distance between the two terminals was small enough for a spanner to bridge. Apparently it was proved several times that it was possible to end up with a spanner welded to the terminals.
This is not my story, I read it in an electronics rag many years ago - but worth repeating.
Service guy was working on a radio transmitter, and part of the diagnostics was to check the HT line. All 10KV of it.
The transmitter had safety interlocks all over the place, so it was faster and easier to just place the meter within the cabinet and look at the reading through the closed glass door.
Barely a fraction of a second after he flipped the power switch, he realised the meter was set to low ohms (from the previous tests).
A big bang, a bright flash, and a very impressive black charred mess on the inside of the door glass was the result.
An elderly member of the radio club had several unnerving tricks. One was to test for live 240v mains by using the back of his hand - just close enough to tickle the hairs.
The club room's bench top was thick wood with a sheet steel covering. Just as you were fiddling with the insides of a live device he would hit the bench top with a large hammer - very hard. He would then invariably chortle "That made you jump".
On a HF competition day in a tent high on the moors there was a thunderstorm. Rather than close down the session he operated the transmitter with his feet off the floor. The static sparks off the transmitter case were quite impressive. The whip aerial was on top of an ex-WD telescopic column probably at least 10m tall - a perfect lightning conductor.
I was working Freelance Tech in my spare time, helping folks maintain, repair, troubleshoot, & purchase computers. Get a call from a rather nice young lady complaining that her computer isn't working right, asking if I can come take a look. I grab my tools & software, head on over, & knock on the door. The first thing I notice when she opens the door is that she looks like someone tried to stuff her head-first through an industrial shredder, the second thing is that her breasts aren't the only thing covered in scratches, and the third thing is that the place _reeks_ of cat.
We're talking "nobody's cleaned the litterbox in a year" plus "we microwave it every night to make it go all gooey" style stench.
I try to smile politely around the urge to hjorf up my guts, ask to see the computer, and she takes me through Cat Central to her computer desk. You know the proverbial "old woman with a thousand cats" image people like to paint? She only had two cats, but they were trying to make up for quantity by the quality of the stench they exuded.
I sit down at the desk, take one look at the mid-tower on the floor beneath her desk, & try very hard not to start laughing my nuts off. There's so much cat hair in it, on it, around it, on top of it, & packed in around the sides that it looks like it's wearing a damned fur coat. I check that it's not turned on, unplug it, and drag it out into the light. It took FOUR CANS of compressed air to finally remove all the cat hair from the vents, and when I opened up the case to give a go to the interior, we found out where the cats had been leaving all the dead mice.
I ended up taking the machine outside, turning it upside down over the trash can, & shaking out all the corpses.
Bring it to her garage, disassemble the machine, & used my various cleaning brushes, cotton swabs dipped in mineral oil, and about six Earth orbit's length of paper towels to clean it to the point where it no longer smelled like cat.
Make sure it's dry, put it back together, take it back inside, plug it back in, & fire it up.
Her first reaction was "WOW! I didn't know it ((the case)) was beige!" nearly made me wince, but her second "Holy Shit! It's already booted?!" made me chortle.
I had to explain to her why letting it get so full of cat hair (and mouse entrails) was a Very Bad Idea, and to keep it clean.
I ended up making $100(USD) on the call, and got a rather nice memory of mamories, but the smell will haunt me 'till my death.
I'd trade her cats for mere electrocution any day... =-}p
Power socket with live-neutral reversed. Everything plugged in works perfectly. Equipment with earth-neutral reversed. Works OK (apparently) when plugged into normal socket. Put the two together: stops working. Luckily - because the metal cased unit was touching another that was properly wired. Muggins called out at 2 am. By the time I arrived everyone else had gone home. I moved the unit to get to the mains plug (so then it wasn't touching the adjacent unit) and replaced the fuse.
A narrow escape I've never forgotten. I could so easily have had my hands across the mains, which since the substation was in the building would have been a good 250 volts.
Moral: don't ignore the possibility of two separate faults, not very dangerous individually, being lethally combined. In this case both errors were made by professionals who should have known a great deal better.
In the early 80's I had a house where live and neutral had been wired the wrong way round at the fuse board. Before removing, the expensive to run, electric hot air central heating unit I got a "sparky" friend round to check what I was about to do. He rectified the problem before I did any more work.
Despite building PCs for a couple of years, what I always forget is that when you slide a case out of it's box, and it's wrapped in plastic with polystyrene packaging it'll build up a nice static charge as it slides out of the box.
I managed an inch long spark and a lot of swearing just the other day forgetting that one.
In the early days mainframes had to be powered up with a significant delay between applying mains to each unit and peripheral. Power also needed to be removed in an orderly fashion. The mechanical sequencer was a small box on the wall - and its door was not locked. Opening the door triggered a safety interlock which disconnected everything it controlled - instantly.
On prototype machines it could take three days to get everything working again after one of those crash-down events. Can't remember what was done to prevent it - but it probably involved a piece of twisted wire to secure the sequencer door against wandering fingers.
On another occasion a development OS programmer was waiting for his dedicated test slot on the mainframe. Trying to keep out of the operators' way he leaned against a set of low level cupboards which held the card trays for the night's job runs. There were more card trays than could be accommodated - so the operators stacked them on top of the cupboards too. So he actually leaned against the loose trays - and that pushed the emergency off button behind them on the wall.
A few days later he was waiting again. This time he avoided the stacked surfaces - and snuggled into a convenient gap between them. The gap was a recent change to stop a repeat of the problem with the boxes - he leaned back onto the emergency off button. After that a papertape spool core was taped over the button so that only a finger could press it.
A UK customer had been waiting many months for their new mainframe. Eventually to solve the manufacturing delay a compatible, more powerful, machine was imported from the USA.
The manufacturer's engineers commissioned it satisfactorily. Then they left the customer's electricians to install the 240v-110v transformer permanently - it had been jury-rigged during the tests. Next morning the customer had to break the news that their electricians had wired it up back to front.
In the dim and distant past I was the sole retail/distribution technical support for a high-end audio manufacturer. It was amazing the number of times a disgruntled dealer or distie would ring up and complain that their customer, who had just spent £50k on a system, was having weird control issues and/or intemittent hums and pops in the audio, and occasionally dealing out the kind of shocks described in the article.
Over time it became standard to ask them to confirm how the location was earthed as inevitably it was something similar where there was no local earth in place.
As the systems we sold frequently involved multi-room audio distribution in mansion-type accommodation, you can imagine that the potential for potential was quite significant.
Regardless of the clear requirement in the manuals for all our powered components to be properly earthed, it seems that various bits of the US, Spain, much of Scandinavia etc. aren't fond of earthing their circuits.
Strange that there was reluctance to chuck £300 at a spark to fit a ground rod or two was an issue when the customer might just have spent £12k on a CD player.
Back in the eighties I worked in a Strowger telephone exchange in the UK. All the equipment was powered by 50V DC running in aluminium bus-bars across the top of the racks.
These bus-bars had blue plastic insulation in areas where they were considered close to other equipment, but the long straight runs were uninsulated.
The cable trays for the selector wiring ran above the bus bars, and we were carrying out some additions to the exchange which meant adding some more cable trays - which were bolted together.
You can see where this is going I'm sure, but one of my mates managed to drop his spanner square across a set of bus-bars...
The spanner glowed orange, then red, then white, and then melted slowly away, dripping down to the floor, whilst all the selectors on the rack juddered to a standstill, and then started up again.
The bus-bars were completely unmarked!!
I was commissioning a 3 phase industrial oil pump yonks ago whilst under instructions from upon high not to buzz out the wiring because of time constraints. My supervisor says "let her go" so I press the start button and the pump starts. The problem was that the cabling contractor had reversed two phases so the pump ran backwards, pressurised the low pressure piping and blew no end of gaskets whilst showering the pump enclosure in hydraulic fluid. Exit, whistling nonchalantly.
A friend of mine worked for a company that was installing a PC assembly facility in the late '80s, and there was this new guy, that 'thought' he knew everything about eletricity.
Long story short, the assembly line had ground wristwraps connected to the machinery in each station. So far, so good, except... that smartpants had used the same grounding wire to connect THE LIGHTNING RODS to the ground.
Yes, the first rainfall coupled with an electrical storm would immediatelly kill all laborers in the assembly. As soon it was figured out, that guy was promptly fired.
There were rumours of misterious deaths in the previous companies where that guy had worked, all by eletrocution. My friend dully informed all of them to check their grounding lines. 3 out 10 had that slight mistake on the grounding instalations.
Shudders.
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