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First off, I'm talking about European Schuko sockets, 220V AC.

There is this one outlet with 2 sockets in the corner of the room, and both of them have caused problems. Over the past few months they've fried 3 USB chargers and when I try to watch a movie on a pico-projector (5V DC) it causes flickering and blacks out from time to time (usually right when the movie gets interesting). I should have isolated the problem to that outlet earlier, but I thought the whole house was electrically haunted.

Finally we stopped using those sockets, and I took it apart today. Nothing unusual in the wiring, no sign of burnt anything, no exposed wires. I put it back, turned the power back on to the apartment and measured it with a multimeter. Phase–neutral was OK, 220V, but ground–neutral was showing a 1..2V reading.

The thing is I think this stray voltage varies (based on the projector problems during a 2h movie). This is why I was a bit reluctant to call an electrician, I don't want someone to come, stay for a few minutes, notice nothing unusual and say everything is fine. Then charge me without fixing the issue.

I'd really like to use that outlet, it's well placed for the projector. Otherwise the room would be criss-crossed with extension cords. What could I do?

Later edit

I think the renovation was done by a hack electrician...

  • There's an electrical panel with 10 switches in the hallway. I thought wow, how nice, such granular control. Turns out the mapping is completely haphazard. They're not labeled.
  • When a guy came to install gas sensors he asked me to turn off the power to the apartment because he was getting zapped by the gas pipes!
  • The 2 bathroom fans have been improperly installed... You can't turn them on just like that, or it'll work for a few seconds then turn off. If you fiddle with the OTHER's switch twice you will get the second one to respond to its switch. (Mayhem, I know. Found this out through trial and error)
  • Brought in an old stereo amplifier and I now notice it sometimes jolts with a loud static noise, as if I had taken out and touched the audio cable at loud volume.
  • Sometimes the WiFi router or the wireless audio receiver go offline for a few seconds

That's all the suspicious details I could conjure up for now.

Answers to comments

I don't have enough reputation to create value for the StackExchange community by answering bloody comments.

I haven't checked ALL the receptacles, but two of them look perfectly fine. Tidy wiring even.

One phase of 220V, I believe...

The USB chargers weren't particularly cheap ones, in fact. If overheating is a measure of poor quality, they didn't do that. May they rest in peace.

The outlets don't have built-in USB. One of them has a built-in TV coax plug. Some light switches (SHOULD be different circuit) had light indicators that don't work. Could have been they all burnt out before I moved in, which would have been a problem. But the owner came by today and told me she's certain they had never connected those. I had issues with these before, and recall how I systematically tore out these little duplicitous "conveniences" and spat on their worthless corpse.

We have CFL lights in other rooms, yeah. The washing machine has a regular Schuko plug.

Later-er edit

I had an electrician come check it out. He brought in a voltage stabilizer (with servo-motor) and measured between 210V and 230V. The dips are probably the cause, and it means the electrical issues are for the whole apartment, not just that power outlet. He replaced it to be sure.

His recommendation was to but a voltage stabilizer and plug valuables into that... I find that extremely cumbersome, and quite expensive, all for a "fix" that doesn't address the core issue.

What other recourse do I have to get cleaner power to the entire flat? I'll try to talk to the building's administrator and to the power company, but what should I be aware of?

  • Only if all loads are off will there be no deviation between earth and neutral. The higher the load, the higher the deviation on a circuit, it's even possible to use that as a test. 1V is a sensible value. – Harper Mar 20 '18 at 15:05
  • Is your house wired with one phase of 220V, or two phases? If two, there is a possibility of 385V on a socket. No USB charger made will appreciate this. – Harper Mar 20 '18 at 15:39
  • I have seen 3v ground to neutral cause switching powersupplys to have problems in a light industrial plant. We had to install a huge grounding grid to eliminate the problems this was on 120v 60hz system. I would not expect less than 2v ground to neutral to be a problem but you may try monitoring while in use it is possible the voltage will increase under load then you would need to find the bad connection. – Ed Beal Mar 20 '18 at 20:32
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You should only do the following if you are electrically competent. Working live is dangerous and could lead to ventricular fibrillation and death.

There are a couple of things to try. However, these are only basic checks that in all honestly will probably reveal little. A more comprehensive set of tests should be carried out but are beyond the scope of most people.

Firstly checking all the terminals are tightly connected as arcing and overheating is a possibility of loose terminations.

Check the phase to neutral, phase to earth/ground and neutral to earth/ground are correct. You seem to have done a part of that. However, earth/ground to neutral voltages are not uncommon depending on what is connected and certainly 1-2V is nothing to be worried about.

It is highly doubtful the outlet is at fault. Most outlets are at their fundamental level mechanical electrical switches, they posse no ability to inherently damage appliances.

That being said if the socket is one of these new USB chargers that are built directly into the sockets plate then it is certainly a possibility the transformer has become faulty as this is actually quite common from experience as they are always overloaded by larger devices such as iPads.

The real cause is more likely to be one of the following but is difficult to diagnose as it requires specialist tools.

It could be electrical surges coming in through your main supply even though it is supposed to be regulated against such surges it is certainly a possibility. In these cases it tends to wipeout several appliances that are not protected against such surges but this doesn't seem to be the case here.

Do not use cheap or fake/imitation USB chargers (I cannot stress this enough). There are a thousand articles out there about them. They use cheap sub-standard electronics that produce horrible rippled direct current output and introduce harmonics back into the alternating current supply side. They also tend to overheat a lot.

While on the topic of harmonics it is actually one that not many people truly appreciate or understand yet it is a likely cause of electronics to fail. Harmonics can come from within the property or from outside. These harmonics can be produced by other electronics and devices such as switched mode power supplies, fluorescent lighting, UPS, magnetic cored devices. Without analysing the supply you would not be able to tell other than devices overheating and prematurely failing.

In the end it is difficult to diagnose your issue over the internet without more information.

  • I wouldn't agree, outlets (meaning receptacles) often fail, typically with an arc fault of one kind or another. DO agree on the cheap Cheese USB charger blocks, for me in America I find I can get genuine Apple iPad charging blocks cheaply on eBay (schools buy iPads by the thousands and provide their own charging and sell off their excess). – Harper Mar 20 '18 at 15:38

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