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Using a simple multimeter I have discovered around this home (what I may be mistakenly calling) "stray voltages", i.e voltage potentials across appliances' metallic parts that should not have a voltage potential.

The home is located in Eastern Europe, Romania. Where outlet voltage is 220-240 VAC. It does not have a protective earth / grounding system installed (tested using a simple socket tester, and confirmed by the home owner it was never installed).

At the breaker panel there is an RCBO which should trip upon detection of any residual current or ground fault larger than 300mA, or an overload larger than 20A (which may be a rather big limit considering the wires in the walls appear to be at most 2.5 sq-mm cross sectional area).

I am not an electrician, nor the home owner. I am just a temporary guest, observing and trying to assess the safety of the place (which looks concerning to me), while I'm staying.

I tried my best to describe and present the suspicious measurements in this video. Make sure to enable subtitles. https://www.youtube.com/watch?v=bflTOGjgSKM

The sparks in the video were produced with the multimeter set to measure 10A DC max current, so it allowed current to pass through the probes. I don't know what the current was, because my multimeter does not measure AC current, but the RCBO did not break the circuit. No sparks were produced when measuring voltage.

The stray voltages around the kitchen sink are all caused by the washing machine being plugged in. With the washing machine plugged out the sink-gas cooker, sink-gas pipe, and sink-radiator voltages turn to 1 or 2 volts. I think the reason is that the washing machine has water hoses connected under the sink.

Sneaking a peek inside a wall junction box reveals this wiring:

wiring

I don't know what the code specifies, but things don't seem to be looking pretty inside here. I don't think it was done by a professional, and I don't forsee a profesional electrician being called by the home owner anytime soon, nor a protective earth installed in the near future.

In spite of that, what safety measures can I still take to make sure I don't die while staying here?

Would it be a good idea to bring the appliances' casings to the same potential somehow? Pluging them into the same extension cord, which has a ground pin connection? Even though they will not ultimately be connected to ground, would that bring their casing potentials to the same level and reduce the risk of an electric shock? Or rather increase the risk?

Could the voltage found at the casings be induced by an electromagnetic field inside the appliance, without direct contact, and therefore not dangerous because it won't produce high enough current (hence the RCBO not tripping)? Or is it just that the RCBO is not sensitive enough?

Is it common to have stray voltages like these in homes without a grounding system?

Update 1: Using another multimeter capable of measuring alternating current I found the maximum current when producing the sparks to be 3.3mA leak current

Update 2: I installed a 10mA C16 RCBO externally, dedicated to this outlet. Inline with an extension cord which will be used to supply power to the washing machine, fridge, and some other appliances. I don't think this is an ideal solution. But it has the advantage of being portable, and was the best I could do for now, since it is not my home.

About the inexistent grounding system I'm not sure there's much I can do at the moment. I could be able, for example, to use external wires and bring the ground of this extension cord outsie and connect it to a metal rod driven into the soil. But I cannot do that for every outlet, and I will end up with some grounded and some ungrounded appliances around the house, which I'm not sure is a good idea. And after some more research I think is not a good idea from other reasons too, and even illegal in some countries.

externally installed rcbo

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    \$\begingroup\$ Consider wearing insulating gloves and insulating boots whenever operating any of the appliances involved. Disconnect/unplug them when not in use. \$\endgroup\$
    – KristoferA
    Commented Dec 12, 2022 at 3:31
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    \$\begingroup\$ Best guess: Y-capacitor leakage from SMPSes connected and high ohmic multimeter gives high voltage readings. \$\endgroup\$
    – winny
    Commented Dec 12, 2022 at 5:53
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    \$\begingroup\$ What bothers me is the rating of the RCBO. 300 mA can be fatal, and it would be desirable for the RCBO to trip at a level that actually prevents electrocution. :-( \$\endgroup\$ Commented Dec 12, 2022 at 9:49
  • \$\begingroup\$ Thank you for the useful observations. Yes, indeed 300mA is a very poor sensibility. The RCBO is the first thing that I'd love to have upgraded here. Considering the information given here: elcosh.org/document/1624/888/d000543/section2.html , anything above 25mA is dangerous to the human body. In my local shops there are RCBOs for sale with low sensibility of 10mA. Which I would prefer to have installed, but the guy at the store said 10mA is "too low" and "it would be tripping all the time", "only suitable for jacuzzi" and recommended the next value of 30mA. What do you think? \$\endgroup\$
    – Robert Lee
    Commented Dec 12, 2022 at 16:40
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    \$\begingroup\$ According to this website, 30mA sounds like good enough, "IEC 60364 standards only ask for 30mA" se.com/eg/en/faqs/FA177318 \$\endgroup\$
    – Robert Lee
    Commented Dec 12, 2022 at 16:49

2 Answers 2

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I wasn't so bothered by seeing 20 or 30 VAC using a voltmeter. Especially in older homes with aging ground rods where there may be more than a few Ohms resistance in the grounding to Earth. A voltmeter doesn't present much of a load and voltages at that level can be passed along for several different reasons.

You might feel something, but I've seen over 60 VAC using a Microsoft Surface laptop through a power brick. I could certainly "feel" it when brushing my fingers lightly across the laptop! I elected to run it through the process of getting an official response from Microsoft. Took a while but they finally wrote back, calling it "normal" and "don't worry." (It's a balancing act for situations where there are only two prongs to the mains that can be flipped either way without knowing which of the two prongs is provided with neutral and there's a special power supply "type" for this kind of power brick.)

Your situation is different, of course. And I really hated seeing that picture of the wall junction box. Worse, you were able to show well over 100 VAC with the voltmeter and significant sparking just running an ammeter lead across the metal. That signifies to me that there is too much voltage and too much current available at that voltage to be considered safe.

So some things worry me more than others. If possible, in the cases where there is over 100 VAC showing up on the washing machine chassis, for example, if it is possible to rotate the plug and flip the neutral and line prongs to opposite positions then you can try that to see if it improves your situation. It may. But it didn't look easy to do from what I saw there.

If I were in this situation and knew in advance that the owner wasn't going to help me, I'd set about carefully tracing everything all the way back to where power arrives from the supplier company. If there is a power pole, then all the way back to there. I'd be looking to see if there is a grounding rod at the power pole, if so, and how far away my home was from there. (You've already said the home itself isn't Earthed.) I'd then carefully draw out all of the information I could possibly gather up, write it out in a clearly drawn set of diagrams, and then sit down to work out a strategy to alter the system to make it safe. And I'd pay for the parts and do the work, myself, testing things as I went from A to B to C, etc. It's just not worth the risks, otherwise.

I'd definitely get a grounding rod (about a meter long and pounded deep into the ground near the home.) That, unless you already have access to some rebar that extends out of the concrete house pad that you can attach to (called a "Ufer ground" if you do have such access.) You absolutely want to have one side of your power at the home tied as closely as possible to the voltage at the power pole (or underground line that arrives at a ground-level box.) It's just not good to have your home and nearby ground "floating" with respect to the supplier's power source ground. In a storm situation, your local ground can be elevated quite high and be quite unsafe. So you just don't want that situation to occur. And this means strapping the house "neutral" as close as is possible to the power source's mains lines (neutral and line) wherever they are located away from the home.

If you don't feel capable of the design and work yourself, post up what you can about the details at your location. This will mean you have to work for it. Not just photographs. But you need to try and also draw out a diagram for us because otherwise we are guessing a lot about details you should and can resolve for us. Pictures help, here and there, to make your points. But we really very much need to know what you can work out about your situation, conceptually and practically. Even then, it's asking a lot from us to make safety guesses. So providing as much detail as possible is vital. It needs to be convincingly good. So whatever that takes to do.

That said, you've already made a good point that things aren't safe there. So be careful!! Please be careful. I don't usually worry that much about being shocked with 120 VAC. I've been hit with that enough times already. I'm older now and more at risk, so I'm more careful than I once was. But it still doesn't scare me and I do take chances. But my situation is 'convenience' of changing out an active plug or something. Your situation is an everyday "I need to use the washing machine" kind of thing. So it's a lot more often and there are just that many more chances of something dire happening.

So take your time. Work out the details as best you can. Let us know more. And, likely when you do so, this question will be moved to some kind of 'home improvement' site, rather than here. But that's okay, too. They are pretty helpful when they can be.

Keep up the good work and document as best you can. And I think you will find someone willing to try and make some practical and useful suggestions. You have my best wishes, for what its worth. And thanks for the video. It helped me see better what you are seeing there.

I wish there were a 'bright line' answer for you. But there isn't. Not with what we know now, anyway.

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  • \$\begingroup\$ Oh, I have a laptop that does that too when I brush the back of my fingers lightly across it. I always assumed it is not dangerous since the power brick brings the voltage down and removes any direct connection with the 230VAC socket, using primary and secondary coils, right? \$\endgroup\$
    – Robert Lee
    Commented Dec 12, 2022 at 12:51
  • \$\begingroup\$ For that washing machine I tried what you suggested, flipping the prongs and inserting into the socket the other way around, swapping the live and neutral that go into the machine. The result was the same. Still 113VAC, on the same places. Is this good or bad news? Maybe the voltage is present there by design, to allow for detecting when the door is shut? But I believe that could be done in safer ways. \$\endgroup\$
    – Robert Lee
    Commented Dec 12, 2022 at 13:07
  • \$\begingroup\$ @RobertLee The laptop case is safe. The voltage is leaked through capacitors that are intentionally installed and where there are tradeoffs being made. But not so that it would be dangerous. So don't worry there. The fact that you measure the same thing either way with the plug tells me there is some other problem than the one I was thinking about. So it eliminates one idea. That's all. It doesn't tell me what the real problem actually is. \$\endgroup\$
    – jonk
    Commented Dec 12, 2022 at 17:44
  • \$\begingroup\$ @RobertLee That's a 220V/240V country? If you have any appliance (like a desktop PC for example) with Y caps from neutral and live prongs to earth prong, but you don't have earth connection, the earth wire and all the metal casing that should be earthed via mains plug now happily floats at 110/120V which is what is measured here. However, leakage current of 3 mA would require relatively large 47nF caps at 50 Hz. It would explained if you have 10 appliances with 4.7nF each, but that is a bit high. Maybe a damaged Y capacitor. Or, the washing machine just has big filter caps. \$\endgroup\$
    – Justme
    Commented Dec 12, 2022 at 20:33
  • \$\begingroup\$ @Justme Yes, it is a 220V/240V country. \$\endgroup\$
    – Robert Lee
    Commented Dec 12, 2022 at 22:46
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I suspect that somewhere there is a faulty ground or neutral connection. Normally, the safety ground and neutral should have only a few volts between them (and almost nothing if there is no load on the branch.

This is a dangerous condition and needs to be fixed by an electrician.

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  • \$\begingroup\$ Your suspicion is right; the question did mention that there is no grounding installed. Such are old houses; grounded sockets may only be in areas like kitchen or bathroom. Or in this case, never installed. And as usual, equiment with Y caps and no ground means metal case capacitively floats at half mains voltage. \$\endgroup\$
    – Justme
    Commented Dec 13, 2022 at 18:06
  • \$\begingroup\$ The video shows them measuring a fridge and a washer, which should both be grounded. Even if the ground is tied to neutral, it should still only be a few volts. It’s telling that the voltage shift is less with the washer ‘off’ (no load) compared to the fridge (load) - big drop on neutral. \$\endgroup\$ Commented Dec 13, 2022 at 18:19
  • \$\begingroup\$ That said, with no ground the appliance cases will float depending on leakage in their power supplies and wiring. \$\endgroup\$ Commented Dec 13, 2022 at 18:30
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    \$\begingroup\$ Yes, that is the problem with old installations. The plugs and sockets used are commonly used in many countries. Old houses can use old mains sockets with only live and neutral (except maybe in kitchen/bathroom ground was mandatory). You can freely connect anything with a grounded plug to the old socket and the device will have ground absolutely floating without being connected to anywhere. And many devices with grounded plugs expect to be connected to a grounded socket, and forbid connecting to an ungrounded socket. Explains laptops and desktops having a buzz on them via Y caps to ground. \$\endgroup\$
    – Justme
    Commented Dec 13, 2022 at 23:02

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