Deadly problem with house wiring - Page 1
Forum section: electronics / general

author: MarcusFunt
author_rank: Contributor
timestamp: April 06, 2022, 02:58:44 pm
content: I made a quick video about the problem.https://youtu.be/5d6zy09IbGwPlease dont hesitate asking questions if i missede a piece of information

author: tom66
author_rank: Super Contributor
timestamp: April 06, 2022, 03:33:55 pm
content: Is this not just an effect of class-Y double-isolated appliances? Since you measure no difference between house ground and outside ground, you do not have something like a PEN fault.To test your theory you should check voltage between N and E and L and E. In Denmark, almost every property is 'TT', which makes a PEN fault impossible. You could have a TN-C-S property which would allow for PEN fault but these are (according to Wiki) quite rare in Denmark.

author: BrokenYugo
author_rank: Super Contributor
timestamp: April 06, 2022, 03:47:13 pm
content: The case with sparking is probably a real problem that should be handled carefully. I'd assume in whatever powers the mic.Everything else, you're probably just measuring expected leakage current through Y caps and whatnot, in certain scenarios (e.g. barefoot on earth or a bare concrete floor) that little current can be felt. Remember that it does not take much current to generate a voltage across the 10 megaohm input impedence of a typical DMM, in fact you can use that resistance as a current shunt in a pinch, 1 volt=100 nano amps (0.1 uA). Takes a "low impedence" meter, or a light bulb, to see if there's any hazardous current available, this is why electrician oriented enters usually have such a mode, or outright make all voltage measurements low z.

author: Monkeh
author_rank: Super Contributor
timestamp: April 06, 2022, 05:44:23 pm
content: Call an electrician.

author: MarcusFunt
author_rank: Contributor
timestamp: April 06, 2022, 05:53:15 pm
content: I did the same tests again with a 820kohm to simulate a human body. I got 7 volt om the solderimg iron(enough to feel on my leg with a antistatic strap on ). On the Charger i got 1 volt with my body as gnd ref. I got 115 volt (yes. not a mistake) through the resistor on the mic.i got the same 115 across a 410kohm with a 4nf cap on.I suspect that the same problem is happening in out Kitchen because we can feel a small elektrick shock when we touch the body of the microwave(gnd is Stone tiles)

author: wraper
author_rank: Unknown
timestamp: April 06, 2022, 06:02:45 pm
content: Quote from: Monkeh on April 06, 2022, 05:44:23 pmThere is no reason to call an electrician. He will fix nothing as there is no wiring fault. Actually most likely there is no fault at all. I did not see anything that would indicate anything beyond PSU which was not grounded (either internally or no ground in the socket) and current leakage through Y type noise suppression/safety capacitor. Or smaller leakage through capacitance between the windings in transformer.

author: wraper
author_rank: Unknown
timestamp: April 06, 2022, 06:04:45 pm
content: Quote from: BrokenYugo on April 06, 2022, 03:47:13 pmA few nF of capacitance from Y caps is more than enough to cause visible sparks.

author: Monkeh
author_rank: Super Contributor
timestamp: April 06, 2022, 06:10:13 pm
content: Quote from: wraper on April 06, 2022, 06:02:45 pmCalling an electrician will get you someone who is directly familiar with the local wiring methods and can accurately determine if there is a fault or not.

author: MarcusFunt
author_rank: Contributor
timestamp: April 06, 2022, 06:14:32 pm
content: I can drage 1.12 ma from every piece of metal om my pc. Is that a PSU fault? Or just the caps?

author: MarcusFunt
author_rank: Contributor
timestamp: April 06, 2022, 06:15:48 pm
content: I ment draw and not drage. Danm danish autocorrect

author: wraper
author_rank: Unknown
timestamp: April 06, 2022, 06:16:53 pm
content: Quote from: Monkeh on April 06, 2022, 06:10:13 pmAnd will give you a hefty bill for doing nothing other than uselessly checking things. As he measured 0V between mains earth and the earth rod, the issue was not caused by any problems in mains wiring. I suggest also measuring resistance, just to be sure.

author: wraper
author_rank: Unknown
timestamp: April 06, 2022, 06:24:49 pm
content: Quote from: MarcusFunt on April 06, 2022, 06:14:32 pmThis is an OK leakage current thru Y caps (on a high side though). If PSU has no earth connection as many laptop power bricks, it acts as intended. Desktop PCs are always grounded. Double insulated devices which do not have an earth connection normally should have lower leakage current, like < 0.4mA.

author: Monkeh
author_rank: Super Contributor
timestamp: April 06, 2022, 06:26:31 pm
content: Quote from: wraper on April 06, 2022, 06:16:53 pmYou're concluding an entire installation is safe and correct from two data points collected in different locations by (and no offence intended here) an unskilled person in a shaky video. If anyone, including you, has doubts as to the safety of an electrical installation anywhere,call someone qualified, not a random person on a forum.It does appear that the equipment in the first portion of the video is connected via an ungrounded socket (not that such a thing has any business being used), which would indeed explain matters. Whether that is safe or not depends on further details we are lacking.

author: wraper
author_rank: Unknown
timestamp: April 06, 2022, 06:35:30 pm
content: Quote from: Monkeh on April 06, 2022, 06:26:31 pmAs you said this, yeah. Looks like some extremely outdated garbage even with no recess for a plug, not to say earth connection. I don't think anything like this can be possibly legal these days. Electrician most likely won't be able to do anything with this as cable in the wall most likely does not contain an earth conductor. And therefore cannot be fixed without doing total rewiring.

author: MarcusFunt
author_rank: Contributor
timestamp: April 06, 2022, 06:57:02 pm
content: Thanks you for your answers. Do you rekkon something is wrong with the pc supply? I know i need to have an electrician look at it. In fact it's not even that Long ago i had an electrician say that everything was fine. i just couldnt help but doubt him because og All the shocks that i got. (You where right about the video. Im just a 13yo kid/ee hobbyist that thought something was wrong. It's the first time im working with house wiring. As a 100% self taught engineer i just thought that it couldt be good to get shocked constantly. Sorry for dumb questions and Spelling mistakes as i said im 13, still lerning and it's the first time im doing this kinda stuff. But one time gotta be the first one and i have learned a Lot!! Thanks for that.) "The Expert in anything was once a Beginner" -Helen Hayes

author: Monkeh
author_rank: Super Contributor
timestamp: April 06, 2022, 07:37:57 pm
content: Quote from: MarcusFunt on April 06, 2022, 06:57:02 pmNot likely.

author: tooki
author_rank: Super Contributor
timestamp: April 07, 2022, 05:20:39 am
content: This question gets asked every year or so: “I feel (and/or can measure) a tingly voltage. What’s wrong?” and the answer remains the same: it’s the class-Y interference suppression caps in a switching power supply doing their job. If it can be felt or measured, it’s not grounded, be it because the power supply doesn’t have a ground, or because the outlet in use is not grounded.

author: Berni
author_rank: Super Contributor
timestamp: April 07, 2022, 06:08:04 am
content: This is quite a common issue with non eathed appliances, nothing to worry about.Whenever your device has just a mains plug with only 2 connections that means it is not earthed so the current from the Y capacitors in the PSU can't flow back to ground. This can be made even worse when you plug together multiple equipment with no ground as the currents can add up to something that can give a slight shock.The issue goes away as soon as you plug in a earthed device, such as for example connecting a external monitor with a earthed plug into the laptop. That device pulls the ground potential down to earth potential.It is also possible to buy a different laptop power adapter that does have earth (typically if they have a 3 pin power connector they connect ground to earth inside).The only reason you would call an electrician over this is if you have devices with 3 pin power plugs (plugged directly into a wall) that still give you shocks. In that case you might have the earth wire interrupted in your house wiring. That is indeed VERY dangerous and should be fixed.

author: langwadt
author_rank: Super Contributor
timestamp: April 08, 2022, 11:39:11 pm
content: Quote from: MarcusFunt on April 06, 2022, 05:53:15 pmthe microwave probably has a shuko plug so it isn't grounded (as it probably should be) get a shuko to 3 pin danish plug adapter and plug it into a grounded outlet

author: coppercone2
author_rank: Super Contributor
timestamp: April 09, 2022, 04:17:31 am
content: https://www.grainger.com/know-how/safety/electrical-hazard-safety/advanced-electrical-maintenance/kh-ghost-voltageshttps://www.fluke.com/en-us/learn/blog/digital-multimeters/dual-impedance-digital-multimetersTo a novice at probing, this is useful.You might want a old 100K input impedance meter, if you don't want to buy a fluke for low-z, but I recommend it. Just be sure to verify the low-z mode agrees with high z mode on a stiff source once in a while. If you think about it, the signal should be current limited. This is good to know, but high Z measurements are also good to know about (i.e. it might be associated with the risk of unpleasant tactile shocks).You could do noise related modifications to equipment possibly to reduce this leakage in some things, but its quite advanced work (you still need to obey FCC and other government agency regulations on earth).

author: amyk
author_rank: Super Contributor
timestamp: April 09, 2022, 06:25:19 am
content: Quote from: MarcusFunt on April 06, 2022, 06:14:32 pmFor fixed grounded equipment I believe the relevant standard for leakage current ("touch current") is IEC 60950-1 and allows up to 3.5mA.

author: wraper
author_rank: Unknown
timestamp: April 09, 2022, 06:42:16 am
content: Quote from: wraper on April 06, 2022, 06:35:30 pmOn other thought I googled for Danish plug and it uses an earth prong unlike a usual Schuko socket. However plug in the video seems to be a usual Schuko. Therefore socket may actually have an earth contact but a wrong plug was used so there is no earth connection.

author: Monkeh
author_rank: Super Contributor
timestamp: April 09, 2022, 10:18:56 pm
content: Quote from: wraper on April 09, 2022, 06:42:16 amI think what we're looking at is one of these on the right:Conveniently takes a CEE 7/4, 7/6, or 7/7 while providing no earth contact. There's a reason I regard that entire series as a fatal mistake.

author: langwadt
author_rank: Super Contributor
timestamp: April 09, 2022, 10:24:30 pm
content: Quote from: Monkeh on April 09, 2022, 10:18:56 pmlots of stuff doesn't have or need earth, as long as you only use Danish plugs in Danish sockets something that has a ground pin won't fit in a socket without ground

author: Monkeh
author_rank: Super Contributor
timestamp: April 09, 2022, 10:26:18 pm
content: Quote from: langwadt on April 09, 2022, 10:24:30 pmUnfortunately, lots of equipment comes with non-Danish plugs, does not have an earth pin, and will fit readily into those sockets.This is also not the only scenario in which the CEE 7 series allows a dangerous combination. But it will happily prevent you plugging a non-earthed plug into an earthed socket!

author: langwadt
author_rank: Super Contributor
timestamp: April 09, 2022, 10:27:24 pm
content: Quote from: wraper on April 09, 2022, 06:42:16 amthat's correct, and that why for stuff shuko that needs earth you should either replace the plug or get on of these:https://elektronik-lavpris.dk/images/user_uploaded/2016/studio_2016-07-08_10:47:22.jpg