How did I get shocked? - Page 1
Forum section: electronics / beginners

author: paulca
author_rank: Super Contributor
timestamp: October 24, 2024, 04:49:10 pm
content: I plugged my home brew pump into a 4 way socket and turned the switch for that socket to ON while holding the metal body pump in my hand.buzzzZAP.The thing I find odd is, these are UK plugs. The plug was fully in the socket before the switch was thrown. So my hand is resting on the insulated back of the plug and there are no metal exposed parts.My hands where slightly damp, but again, nothing exposed.Luckily it's not my first shock and while "shocking" boom-tis I managed not to throw the pump across the room.I need the pump, but not spooked a bit I turned it back on and tested the metal body against a known earth. 0V both low and high Z.The circuit is RCD protected at 30mA. It didn't trip.How did I get shocked?My very long shot was that on close inspection there are a couple of long car hairs on the socket. Did I just get really unlucky and one of those cat hairs conducted live to my hand while holding the earthed pump body? The "zap" itself was a little different than normal. Normally it would like your whole finger or hand "throbbing", this was a very small isolated spot on the back of one finger.Also given my reaction being very calm, it was lightly a very slight current flow and why no RCD trip. Plausible?

author: Wimberleytech
author_rank: Super Contributor
timestamp: October 24, 2024, 05:09:46 pm
content: My first thought was maybe you saw your grandmother naked"Home brew" raises suspicions.

author: Sorama
author_rank: Frequent Contributor
timestamp: October 24, 2024, 05:26:37 pm
content: static electricity?

author: iMo
author_rank: Super Contributor
timestamp: October 24, 2024, 05:37:18 pm
content: QuoteWhat cat shampoo and conditioner your cat is using? There are some with a pure silver in it, afaik..

author: nfmax
author_rank: Super Contributor
timestamp: October 24, 2024, 05:51:54 pm
content: This happened to me once, or something like it. I got a (minor) shock touching earthed metal. The guy standing next to me didn’t. Traced it down to an open-circuit PE connection, plus a wet floor providing a connection to the ‘real’ earth. But, ONLY when I stood on the cracks between the plastic floor tiles. The next to me was standing on the middle of a tile (scared of the bears, no doubt)

author: themadhippy
author_rank: Super Contributor
timestamp: October 24, 2024, 05:57:46 pm
content: Best to shut the power off and move out until youve had a full eicr done,of course it will fail the eicr on some minor technicality so a full rewire will be required.

author: Gyro
author_rank: Super Contributor
timestamp: October 24, 2024, 06:04:09 pm
content: Assuming the 4 way block and switch weren't actually wet, the only other thing that comes to mind is capacitive coupling. Are you sure the metal case of the pump is earthed, or are you just assuming that it is because itismetal. It's still possible for it to be class II double insulated - check the label for the relevant symbol and do a continuity test from the case to the earth pin on the plug rather than relying on a voltage test.Assuming the RCD is working (push the test button) the shock was either below the trip threshold or much shorter than its 10-20ms trip time - that's what makes me think capacitive. Damp hands would certainly make a shock more noticeable, also what were your other limbs doing, were you kneeling on the floor for instance.

author: Gyro
author_rank: Super Contributor
timestamp: October 24, 2024, 06:12:52 pm
content: Quote from: themadhippy on October 24, 2024, 05:57:46 pmThat's two reasons to go to the pub. Carefully turn the lights off on your way out.

author: paulca
author_rank: Super Contributor
timestamp: October 24, 2024, 06:49:50 pm
content: Quote from: Gyro on October 24, 2024, 06:04:09 pmI mean it's homebrew. You have no real choice but to mix boiling liquids and electricity. So I was standing in a puddle on the floor. In shoes though. I also had 2 silicon hoses round my neck while wearing a fluffy polyester jumper.... so static isn't out of the question.I will continuity test the related earths.I have been inside both units. The boiler is well up to scratch with everything using hightemp braided wires, everything mounted double insulated, except of course the elements. The pump however uses wire twists/nuts, I assume by the retailer when fitting the UK plug.The 4 way had the 2.4kW boiler in it running on full power.

author: paulca
author_rank: Super Contributor
timestamp: October 24, 2024, 06:56:26 pm
content: Well it has perfect continuity between the pump body, the boiler body and/or the earth pin in the plug.As to whether the earth in the 4 way is actually connected to the house earth.... is to be determined.I have now discovered that when the kitchen fitter put the sink in, "bright spark" he was, didn't think to earth the god damn sink or taps. He just cut out the old copper pipes, put in push fit plastic ones and called it a day. Another thing to fix.Note to self. Move all electricity away from the sink until that sink is bonded!

author: Gyro
author_rank: Super Contributor
timestamp: October 24, 2024, 07:03:47 pm
content: Quote from: paulca on October 24, 2024, 06:49:50 pmErr yes, well I think you're on your own with that one!Do try to avoid putting yourself directly across L-N with your feet and arse insulated.Quote from: paulca on October 24, 2024, 06:56:26 pmBonding of taps and sinks hasn't been a requirement since IEE Wiring regs 17th(?) Edition. It doesn't hurt if already in place, but is no longer required. This is even less relevant with plastic pipes.

author: paulca
author_rank: Super Contributor
timestamp: October 24, 2024, 07:34:06 pm
content: Quote from: Gyro on October 24, 2024, 07:03:47 pmInteresting. I assumed exposed metal work, particularly around water should be Earthed.In the case of a kitchen sink, there is a very high probability of electrical devices in close proximity to the sink. Such that they might even fall in.If said live device lands in the dish washer and its earthed it might at least invoke the trip. If the sink has no earth it will be good ole fun fishing the device back out!

author: Analog Kid
author_rank: Super Contributor
timestamp: October 24, 2024, 08:02:21 pm
content: Quote from: paulca on October 24, 2024, 07:34:06 pmThat's why, at least here in the US, the electrical code requires outlets to be GFCI protected if they're within a certain distance of a sink, lav or other water-bearing fixture. Code says nothing about bonding the sink itself to ground. I think that's pretty much old-school electrical practice that's no longer a thing.

author: Gyro
author_rank: Super Contributor
timestamp: October 24, 2024, 08:15:40 pm
content: Yes, it goes hand in hand with RCD (GFCI) protected circuits.

author: paulca
author_rank: Super Contributor
timestamp: October 24, 2024, 08:18:01 pm
content: A 2 wire device dropped into an unearthed sink, will NOT activate a trip. A 2 wire device dropped into an earthed sink "might".

author: themadhippy
author_rank: Super Contributor
timestamp: October 24, 2024, 08:40:10 pm
content: Quoteand the problem is? as soon as something completes the circuit to earth the supply should automatically disconnect

author: Old Printer
author_rank: Frequent Contributor
timestamp: October 24, 2024, 08:51:37 pm
content: Having lived in cold, dry climates with lots of static potential, and being a "self licensed" diy electrician, I have felt the effects of plenty of shocks. There is a distinct and noticeable difference in the feel between static and mains jolts. Static is a quick zap, often with an audible crack, where mains has a very noticeable buzz to it from either the 50 or 60 cycle generator pulse. Once you have had a mains shock there is no doubt what it is, you can feel it vibrate.

author: Analog Kid
author_rank: Super Contributor
timestamp: October 24, 2024, 08:55:05 pm
content: Tell me about it.Worst zap I ever got was a 277 volt one (commercial lighting circuit) that nearly knocked me off a stepladder.BZZZZZZZT!!!Admittedly due to stupidity ...

author: antenna
author_rank: Frequent Contributor
timestamp: October 25, 2024, 12:31:01 am
content: Drywall conducts enough to get a nice shock, maybe that finger touched the wall.. On multiple occasions, touching live 120v while my other hand was on the wall gave me a nice tickle. I learned to not touch sheetrock/drywall when touching a hot wire.

author: Poroit
author_rank: Frequent Contributor
timestamp: October 25, 2024, 05:45:25 am
content: What happened to the rest of the cat?

author: Andy Chee
author_rank: Super Contributor
timestamp: October 25, 2024, 07:08:31 am
content: Quote from: paulca on October 24, 2024, 08:18:01 pmIf the human holding onto the device completes a circuit to earth, the RCD will trip to prevent electrocution.If the human holding onto the device completes a circuit across active & neutral, the RCD will NOT trip.

author: CaptDon
author_rank: Super Contributor
timestamp: October 25, 2024, 12:39:55 pm
content: As for the guy zapped with 277, It is a well known fact among U.S. electricians that 277/480 is the real killer!! 120/0/120 is mostly survivable unless water or stupidity is involved. 90% of folks claiming to be shocked by 240 actually only were shocked by 120 even if it was a 240 circuit. Electricians working with much higher voltages in the common 1, 2 and 4KV range tend to be much more careful and wear lots of PPE gear. They may get arc flash burns but are seldom shocked. Different story with some of the still existing 220 D.C. on Iceland!!! 220 A.C. gives you a chance to get away, 220 D.C. will grab you and hold you and even with broken fingers the muscles will still hold on. De-energizing is the only way to stop the cooking flesh!!

author: bson
author_rank: Unknown
timestamp: October 25, 2024, 06:09:08 pm
content: Double check that the GFCI outlet didn't get polarity swapped. If polarity swapped E will be connected to L and energized. Needless to say this is bad.

author: themadhippy
author_rank: Super Contributor
timestamp: October 25, 2024, 06:25:53 pm
content: QuoteAs the op is showing a uk flag its a fair bet the socket dosnt have a built in rcd,instead its protected by an rcd at the consumer unit,also the minute you apply a load,which would be between neutral and earth the rcd should still operate

author: paulca
author_rank: Super Contributor
timestamp: October 26, 2024, 10:00:20 am
content: I opened the pump to check it's wiring and ... I have no idea what is going on.Earth -> Chassis. That much is fine.However, the motor itself has 3 wires. White, green and red.Live -> WhiteNeutral -> GreenLive -> Capacitor -> RedIt's a single phase induction motor. 220-250V, 50/60Hz, 20W. I'm assuming the capacitor is the "start" capacitor to offset the phase so the motor doesn't "cog"?Still, nothing to explain a shock. The actual wiring is a bit dodgy, using wire nuts, but everything is isolated well enough, assuming I don't pinch anything putting it back together.

author: paulca
author_rank: Super Contributor
timestamp: October 26, 2024, 10:04:44 am
content: I'm going with the wet hand theory. The individually switched 4 way extension is probably, to be honest, a bad idea in a kitchen. The switches are NOT water resistant, splash resistant or anything of the sort. They are small rocker switches. If you have ever witnessed the arc flash when you flip a switch, even some light switches, it does make you wonder, just how close is my finger to the contact when I put my big wet finger on it?I did not feel the shock on my finger though, I felt it on the back of my thumb. Electricity and nerves are weird though.I shall now search for a more suitable switchable extension.

author: Gyro
author_rank: Super Contributor
timestamp: October 26, 2024, 10:10:24 am
content: Quote from: paulca on October 26, 2024, 10:00:20 amSounds more like a standard run capacitor. I doubt the pump motor is big enough to need a start cap and centrifugal switch... but yes, the capacitor gives a phase shift on the second winding to give the rotating field. If you're chassis connection and earth continuity are fine then it wasn't the pump. More likely damp elsewhere in your lash up. Did you test the RCD (button)?Get rid of the wire nuts, they may be good enough for Americans but that's no excuse (). Use proper connectors that will withstand a bit of moisture.

author: Analog Kid
author_rank: Super Contributor
timestamp: October 26, 2024, 10:54:08 pm
content: Quote from: Gyro on October 26, 2024, 10:10:24 amI agree about the wire nuts (and am an American); much prefer soldered connections.However, there do exist special wire nuts that have an antioxidant and moisture-resistant gel inside. But I'd still opt for a less lazy connection. (Hey, at least wire nuts are better than "twist the wires together and wrap electrical tape around them". And I have seen that ...)

author: wobbly
author_rank: Regular Contributor
timestamp: October 27, 2024, 12:44:53 pm
content: Quote from: paulca on October 24, 2024, 04:49:10 pmI was not aware that the human body becomes more resilient to such things with repetition. Good to know.Hmm, where's my variac...

author: Gyro
author_rank: Super Contributor
timestamp: October 27, 2024, 01:18:41 pm
content: Quote from: Analog Kid on October 26, 2024, 10:54:08 pmI'm glad you took my tongue in cheek comment as intended! Yes, there seem to be all sorts of moisture resistant gel solutions coming along, including pre-filled jointing boxes that to can put Wago style lever connectors in, snap shut and then drop in a bucket of water or more practically, leave in the garden indefinitely. If I were the OP, I would replace the entire mains cable with a longer one though as it's carrying boiler level current.

author: paulca
author_rank: Super Contributor
timestamp: October 28, 2024, 10:27:34 am
content: Quote from: wobbly on October 27, 2024, 12:44:53 pmI don't think it's accumulative. However, and this may be BS, different people have different tolerances. NOTE. I do not see this as a "safety advantage". I have survived an RCD-less direct "GRAB" contact between E and L, 240VAC. It was so intense and lasted so long because I couldn't move. I had grabbed a plug to pull it out and the back plate came off, my finger and thumb closed behind the cover to contact the E with my finger and the side of the L pin with my thumb. My hand "clenched" uncontrollably, I shook. It went on long enough for me to actually "reason" how I got out of it. Luckily I was "hunched" down ass on my feet, balancing on the my soles of my feet. My solution was to just see if I could shift my balance back and ... thankfully it worked and I fell backwards away which pulled my hand free. I remember lying there for a while wait on the shaking to stop. Too a good day or two to feel right again.The next person to do that might be dead instantly.ME unfortunately encourntering it a second time could also result in my instant death.Its not a safety advantage, it's just that I have experience of it that is all.However my point wasn't about how much damage it did to me, it was regards my reaction. My brain identified what was happening and addressed things, rather than simply launch everything in my hands into the air, pump into the 20L water boiler etc.

author: paulca
author_rank: Super Contributor
timestamp: October 28, 2024, 10:38:11 am
content: As a slight asides...British plugs do indeed win out on safety. Right up until one seemingly insignificant point....I have had far, far too many, more than benign injuries resulting from British plugs. I feel if these were properly reported their safety rating would be lowered significantly.I had such an encounter last night and have the injury still sore today.I stood on the plug for my vacuum cleaner in the middle of the night in bare feet. AWWWWOOOWWW! You would NOT believe how sore that is. It's not even like they just stab you 3 times, no, they roll too. So your foot goes skating out from under you with your full weigh on the 3 prones, then side of the plug, then the back, then the 3 prong again.God that hurts! Hurt 10 times what the pump shock did!

author: themadhippy
author_rank: Super Contributor
timestamp: October 28, 2024, 11:19:07 am
content: But at least once you've extracted the plug from your foot and cleaned the blood off the pins you can carry on using it,unlike other country's plugs whose pins bend if you look at em wrong

author: Analog Kid
author_rank: Super Contributor
timestamp: October 28, 2024, 07:49:50 pm
content: Good old USAn plugs are actually pretty damn good. Decent ones anyhow are fairly bend-resistant.The one case to avoid is where a plug isn't full inserted in the socket, and something metal (say a fork or knife) falls down and hits the exposed prongs. Yowtch! Which is why places like hospitals typically install their sockets "upside down" so that if something does fall on a partially-pulled-out plug it'll just hit the ground prong*.*Which assumes the use of only grounded plugs, no 2-prongers, which is true in a hospital but not necessarily in a home.

author: paulca
author_rank: Super Contributor
timestamp: October 29, 2024, 09:41:17 am
content: Quote from: Analog Kid on October 28, 2024, 07:49:50 pmOr children's fingers. Or the things that children wish to poke, insert etc. When you have seen the results of feeding a biscuit to your CD player you will understand they have little boundaries in the things they will try.Over here some hand wringng nannies made a "socket cover" thinking it was safer to have that inserted into the sockets where children played. However, it turns out as this plastic fake plug is quite flexible, children were very quick to pull it out, turn it upside down and manage to insert on the earth pin, thus opening the L and N gate allowing for things to be inserted. Advisories went out to stop using them. The gated ports are safe enough, the fake plug makes it worse!

author: themadhippy
author_rank: Super Contributor
timestamp: October 29, 2024, 12:34:17 pm
content: Quoteor you go to pull the plug out and manage to grab the shiny bits instead.Thankfully our plugs have a couple of features built in that helps avoid thatQuoteweren't the same nannies responsible for the 4mm banana connectors ban on hifi,hence the silly plastic plug you have to lever out on many amps and speakers,all because a 4mm banana can be shoved into a schuko

author: CaptDon
author_rank: Super Contributor
timestamp: October 29, 2024, 01:09:35 pm
content: I agree on the hospital receptacles being installed 'upside down'. I worked as a BioMed Tech for a 450 bed hospital and we did safety audits daily. The N.U.E.C. however doesn't specify the orientation of vertical or horizontal duplex receptacles. Here in the U.S. General practice has created a 'preferred' method and certain municipalities have their own rules. Often it seems that getting your wiring to pass code depends on if you are a friend of the inspector, buy Girl Scout cookies from his daughter or give money to his son's softball team. I love the different methods and acceptance of 'grounds MUST use green wire nuts', or the other thing 'the closest ground to the home run back to the breaker panel MUST be the one protruding through the GREEN wire nut and MUST be the wire affixed to the metallic housing containing the devices'. I don't think the U.S. even had green wire nuts until the mid 70's?? One thing that should be a rule and isn't "No daisy chaining of receptacles using the backstabbing method"!! There are some local codes that do prohibit backstabbing. When I rewired our last house NO receptacle was on a daisy chain. If there were multiple receptacles on a branch each had its run coming back to a 4" square box with cover plate and the runs were twisted and wire nutted inside the steel box with the breaker number marked on the cover plate. In some places the fire department sets the electrical code 'modifiers'!!

author: Analog Kid
author_rank: Super Contributor
timestamp: October 29, 2024, 07:11:04 pm
content: Quote from: CaptDon on October 29, 2024, 01:09:35 pmHaving dealt with alotof really shady domestic wiring over the years here:Daisy-chaining OK. Nothing wrong with it if done properly.Backstabbing? Ought to be a severe penalty for any "electrician" who even thinks twice about this shitty method of connection.Better yet, just outlaw any devices capable of backstabbing.

author: coppice
author_rank: Super Contributor
timestamp: October 29, 2024, 07:28:47 pm
content: Quote from: paulca on October 24, 2024, 04:49:10 pmOne of the nastiest shocks I've had was from resting one hand against a wall while doing some work with the other hand. The hand on the wall sweated a lot, the sweat ran down into some electrics, and I was shocked, shocked I tell you, to find just how well the salt in sweat makes the water conduct.

author: Analog Kid
author_rank: Super Contributor
timestamp: October 29, 2024, 07:31:21 pm
content: Seems like those of us here in 120-volt land only get half the excitement of you 240-volters ... or maybe the square root of it ...