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For some months, I'm renting an apartment in the Canary Islands. It looks like the plugs are not grounded. For example, when I connect my laptop, a ThinkPad T420si, then I feel an unpleasant sensation on my bare legs when connected to mains (220V/50Hz). A similar sensation I get when touching certain parts, incl. plastic parts (!), of my smartphone when connected to the laptop. Contrary to what I wrote before: When connected to the USB charger, I do not get that sensation when touching the smartphone.

My guess is that the outlets are not properly grounded. While I assume there is no risk for my health, I am a bit worried about my electronic devices. Also, I may want to do some electronics soldering, and I don't like the idea of the soldering iron's tip possibly being on a different potential than ground.

What options do I have to remedy the problem? An isolating transformer?

Update as of 2014-10-15 WEST

After removing the Schuko (fype F) multiplier, and upon close inspection of the outlet, I realized that the center hole is not a screw hole. It is ground, i.e. this outlet is of type L. So I bought an adapter, and yesterday the problem was gone:

Photo of adapter type L to type F

Facepalm!

But wait, today the problem is back, and in the entire apartment! For the first time, I felt a potential when touching the washing machine in the bathroom, and this one is connected with a Schuko plug to a Schuko outlet:

Photo of washing machine plug type F in outlet of the same type

Something is wrong here. Probably unrelated: Some days ago there was a power outage, I think affecting several houses, i.e. not just the one I'm living in.

feklee
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    Correct me if I'm wrong, but a laptop's brick power supply and a cell phone power supply each already have an isolation transformer. They are Class II. –  Oct 12 '14 at 17:18
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    @NickAlexeev But, if they are equipped with a ground-pin that ground may be coupled to the negative terminal with a high resistor and/or a capacitor. If the ground then is wired, but never anywhere connected to ground, the ground pin may inductively/capacitively be swinging anywhere between 10VAC and 230VAC with enough "zapp" to tingle. – Asmyldof Oct 12 '14 at 17:29
  • Why the downvote? Are questions concerning mains OT? –  Oct 12 '14 at 17:39
  • @feklee As far as I am aware, they are not OT. But... – Asmyldof Oct 12 '14 at 17:42
  • @NickAlexeev brick PSU and cell phone PSU are usually class III (SELV), because designers cant prevent you from touching live parts of the secondary winding, e.g. the barrel connector. But even those usually have an Y-capacitor as referred to in my answer. –  Oct 12 '14 at 17:58
  • @Ariser They draw power from mains AC, how can they be SELV? Laptop brick PSUs and cell phone PSUs are usually Class II. When they have the 3rd prong for earth, it's usually used for EMI suppression. –  Oct 12 '14 at 18:33
  • @NickAlexeev Ok, you are right, the PSU itself can't be SELV. They are something often called SELV-equivalent, because the secondary output has to conform SELV regulations. –  Oct 12 '14 at 18:38
  • @feklee off-topic→use might be the reason why this question will get closed. Synopsis: "Questions on the use of electronic devices are off-topic as this site is intended specifically for questions on electronics design." –  Oct 12 '14 at 18:45
  • @NickAlexeev But OP actually asked for how to fix a potential malwiring. This is beyond the scope of usage :). –  Oct 12 '14 at 19:10
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    @Ariser If the O.P. wants to fix the wiring of his apartment in the Canary Islands, then this question belongs on DIY.SE (home improvement stack). –  Oct 12 '14 at 19:15
  • It needs to be noted that the OP is discussing a 220V line, whereas in the US standard line voltage is 120V. In the US one "leg" of the 120V line is grounded, whereas in 220V systems (depending on the specific standard used) one leg may be grounded or both legs may be "hot". If nothing else, using a 220V system (except for a "balanced" hot-hot scheme) creates twice as much leakage current as 120V, possibly enough to put one over the threshold of sensation. – Hot Licks Oct 12 '14 at 22:55
  • (No standard soldering iron/gun that I've ever seen puts voltage on the soldering tip. It is electrically isolated.) – Hot Licks Oct 12 '14 at 22:56
  • (And note that if one is standing in bare feet on a concrete floor they're much better "grounded" than standing on a dry wood floor. The nature of the floor may be involved here.) – Hot Licks Oct 12 '14 at 22:57
  • @HotLicks: I live in Europe and I can tell you for sure, that 230V/50Hz Systems here (220V are gone since 20 years now) have only one hot leg. If you experience more than one hot leg, something is broken or you sit in front of a 5-pin CEE-Connector. But then you will measure 400V between two hot legs, not 230V. –  Oct 13 '14 at 15:11
  • @Ariser - In the US ordinary residential power is 240V, which is delivered as two 120V "legs", 180 degrees out of phase. The "center" is grounded. (The "balanced hot-hot" scheme.) So there are all sorts of different schemes. No telling (without looking it up) what the standard is in the Canary Islands. – Hot Licks Oct 13 '14 at 15:18
  • @HotLicks Canary Islands are part of Spain hence belong to Europe. In CENELEC-Countries only three phase systems (230V/400V) are used in residential, industrial and office areas. This is standardised with only few exemptions. The only networks with single phase, two leg earth symmetric as in the US, are used for railway systems, so you won't encounter a wall outlet with such a configuration anywhere in Europe. –  Oct 13 '14 at 15:47
  • @Ariser - There are islands off the US coast that have different standards from "standard" US power (or at least did 30 years ago). And there were some parts of Canada that were likewise "odd" until about 30 years ago (when an effort was made to standardize in Canada). In any event, the Canarys are not like the mainland US, which is the significant point relative to the question -- the peak voltage is twice as high, meaning twice as much leakage current. – Hot Licks Oct 13 '14 at 15:51
  • @HotLicks: You are right. I wandered from the subject. Double line voltage means double leakage current. –  Oct 13 '14 at 16:12
  • And while I trust most desktop computers and your better laptop power supplies to be "auto-adjusting" and safe at 240V, I'm not so trusting of your cheap phone chargers and USB chargers. (I don't really trust the USB chargers that much on 120V US power.) – Hot Licks Oct 13 '14 at 16:28
  • @Ariser Sorry the link in my question pointed to the English Wikipedia page about "Mains electricity by country". I just updated the link, and now it points to the German version, which states that the Canary Islands ("Kanarische Inseln") have 220V/50Hz. –  Oct 13 '14 at 20:53
  • Looking at that Wikipedia article again, I get the feeling that I should be disqualified from electronics.stackexchange: My laptop's type C plug (Schuko) is connected via an extension cord to a type L outlet. My plan for tomorrow: Get an adapter... –  Oct 13 '14 at 21:16
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    Please have a look at my recently updated answer. Your health may be at risk under certain circumstances. –  Oct 17 '14 at 11:13

2 Answers2

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This is not about grounding, or perhaps it is...

Lets start with your connectors: Do you have AC-connectors at your devices with or without grounding pin? Laptop psu may have a protective earth connection, a phone charger won't have one. I've never seen a phone charger with protective earth connection.

Both PSUs are doubly insulated, I'm pretty sure, which means primary side is galvanically separated from secondary side, which includes everything which can be touched with bare hands.

How does this sensation of 50 Hz AC come over to touchable parts? There's something calle Y-Capacitor between primary and secondary side in these PSUs. It is used to provides a stable potential for the regulating circuitry of the PSU, i.e. it prevents the secondary side from "floating". It can be described by two small capacitors in series between neutral lead and live lead on primary side with the middle node connected to the ground of the secondary side. Hence, on a 230V system, the secondary side gets a level of 115 V AC. The capacitor is designed to permit a maximum current of 0,35 mA to flow, if shorted to ground. This is a current you can sense, but which cannot harm you or your equipment.

If something with earthing in your mansion was wrong, it would not change this effect in my opinion.

In the rare case, your PSUs really have a protective earth connector you should not be able to sense that voltage as it was conducted away. In this rare case you should get an electrician soon, because if you touch your oven or washing machine there is no such limiting capacitor to protect you in case of an failure.

I have a different theory why you feel somthing you do not know at home. On canary islands it is rather warm and carpets are rare while most homes have tiled floor. If you live somewhere cold the rest of the year you probably have carpets or wooden floor which reduce capacitive coupling by orders of magnitude. You just may not feel the phenomenon while it is there, too.

Update

Relating to your updates: Now you do have a problem. When you feel a tickling sensation when touching devices like a washing machine there is one possible conclusion: the potential of protective earth connected with the housing of your devices differs from the potential of your house. Which can mean different things.

  • You have only 2-wire conduits in your house. The neutral and protective earth in your wall outlets are connected to one common wire (usually blue in EU). Some connections in your house have too high ohmic resistance. When under heavy load, voltage on N and PE rises, hence you can feel the influenced voltage.
  • Protective Earth is somewhere broken, effectively. This is really bad, as all Class 1 equipment relies on working PE and a short to housing, which especially water bearing devices are prone to, will put the full voltage to touchable parts of the defective devices.
  • And if PE is interrupted at the equipotential bus bar it gets even worse. Not only a faulty potential from one defective device will propagate through your complete building and be present on every Schuko (PE contact), but will also be induced by assymetric load in the 3-phase-network between the next transformer station and your house. Which means, even if all devices in your house are depowered properly, PE-conductors may conduct harmful voltages.

For the last two options, your life is at risk. You should get an electrician to prove me wrong. The first possibility can be verified by opening a wall outlet (of course after opening the circuit breaker, securing it against reconnecting, verifying all pins in the outlet are deenergised and so on). If there are two wires only and one of them connects to N and PE you have a “bootleg ground”, which renders even ground fault interruptors partially useless.

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Ariser
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  • Good point. Did not consider. Will leave my answer in case of ground problems anyway :-) +1 – Asmyldof Oct 12 '14 at 17:47
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    I experienced an identical issue on a 220V/50Hz system in a different country. In that scenario, I experienced the "tingly" sensation when touching the metal chassis of a MacBook Pro. I did some sleuthing and found that it only occurred on one particular outlet. With the same floor and footwear, even standing in the same place, connecting to any other outlet did not exhibit those symptoms. The problem outlet was a surface-mounted extension outlet that had three prongs, even though it suspiciously had only 2 wires leading back to the non-tingle-inducing mains outlet it was connected to... –  Oct 13 '14 at 00:23
  • Apple devices tend to have a functional earth node which connects to protective earth when connected to a properly grounded wall outlet. Grounding of Apple PSUs is not mandatory, as the 3 wire cord can easily be replaced by 2 wire cords in Europe. But functional earthing brings this unpleasant leakage current directly down to the wall outlet, without bothering you. Aside from that a three-prong wall outlet without proper protective earthing is a real hazard and must be fixed ASAP. –  Oct 13 '14 at 16:19
  • Sorry, I initially provided wrong information. My question is now updated: The problem only appears with the laptop, which does have an power connector with grounding pin (Mickey Mouse cord). The phone charger does not have a grounding pin, and the problem does not exist. When I connect the phone by USB cable to the laptop, however, then I get that unpleasant sensation when touching. –  Oct 13 '14 at 21:00
  • Thanks a lot for the update! At the moment the problem is not there. Could be that it was fixed today: There was some construction work, and also there was a strong smell in the air that I know from burnt electronics. Some days ago, I saw workers with cables, though I think that was telecom, looked like fiber. –  Oct 17 '14 at 18:45
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Steps to go through:

  1. Turn off the power to an outlet that is causing you problems. (Fusebox/main switch)
  2. Check the exterior of the outlet for presence of a metal grounding element/grounding pin/whatever you have over there.
  3. Open the outlet, check to see if there's proper wiring: all three pins connected.
  4. Close the outlet.

If the answer in 3 was: yup, all's well, next:

  1. Connect a multimeter to the ground of one outlet, connect the other side to another outlet somewhere else in a wall (not the same box, of course).
  2. Set the multimeter to "resistance" or "continuity" (the setting that beeps) and verify that the resistance is very low. (very very).

If the answer to that is: yup, low resistance:

  1. Verify that the power to the outlet is still safely turned off.
  2. Set the multimeter to voltage AC (high, at least 250VAC should be possible).
  3. Connect one terminal to Groung, the other to one outlet power wire (phase or neutral)
  4. Turn on the power to the outlet.
  5. Check the multimeter without touching. Measurement One
  6. Turn off the power to the outlet again
  7. Get the terminal from the power carrying wire and put it in the other, leaving the other terminal connected to ground.
  8. Turn on the power again.
  9. Check the multimeter without touching. Measurement Two.
  10. Turn off power.
  11. Remove the multimeter from the outlet.
  12. Turn on power.

Now, if one measurement says "230VAC" or close to it and the other says "0VAC" or something very close (no more than 1 or 2VAC), it's very likely the power ground is properly connected. It's no guarantee, but without being there myself I'm not getting any immediate other inspiration to do further verification.

If any of the earlier steps failed, obviously something is not right.

Asmyldof
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    I would just like to add that a multimeter with the correct category MUST always be used. Do not go sticking a $3 multimeter in a plug socket! – George Oct 12 '14 at 19:32
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    If there's an RCD, you'll probably trip it while measuring like this. – Bob Oct 12 '14 at 22:15
  • @Bob Only if your RCD triggers at 0.23mA or less. – Asmyldof Oct 12 '14 at 23:40
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    @George The key there is the "not touch" part. If I'm using my fluke I'll be measuring live running 380V, but a cheap toy can do these measurements no problem. 1. It will arc if it's really bad (it isn't) -> fuse cuts off. 2. It'll stray out -> You're not touching it with live power. – Asmyldof Oct 12 '14 at 23:42
  • I have a problem with step #3. He suspects serious miswiring, I wouldn't dream of opening an outlet without first using a meter on it--or much easier: http://www.amazon.com/GE-3-Wire-Receptacle-Tester-50542/dp/B002LZTKIA – Loren Pechtel Oct 13 '14 at 01:44
  • @LorenPechtel If the house is so badly wired that the main fuse box doesn't shut off the outlets, it needs to be condemned until a qualified engineer fixes that. – Asmyldof Oct 13 '14 at 15:27
  • @Asmyldof Yeah, but we don't know it's that badly miswired. I'm just saying that if I suspected any serious miswiring I wouldn't touch any outlet I hadn't confirmed was cold. – Loren Pechtel Oct 14 '14 at 03:30
  • Investigation of the outlet did the trick. The solution was embarrassingly simple: Removing the outlet multiplier revealed a socket with three holes. Originally, I assumed that the center hole is simply for a screw, but it isn't: That's ground! The outlet is of type L. So I bought an adapter from type L to type F (Schuko), and now the tingling sensation is gone. By the way, it was not just a little tingling: That really hurt! –  Oct 14 '14 at 18:42
  • Strange, now the problem is back, even with adapter. Also, since today, I I feel a potential when I touch the waching machine the in the bathroom which is connected to a Schuko outlet. –  Oct 15 '14 at 15:19