230VAC outlet measures 100VAC against grounding contact. WTF? - Page 1
Forum section: electronics / general

author: frozenfrogz
author_rank: Frequent Contributor
timestamp: July 29, 2018, 10:06:52 am
content: When I moved into this apartment some years ago (2013ish) I found, that the electrical installation was everything but up to par.There is no RCD and all wall outlets have strictly been wired L + PEN without even tying the grounding contacts of the outlets to neutral.On top of it all, everything sits on a single circuit breaker.How on earth did they even manage to not have fatal accidents??I had a certified electrician check most outlets and he rewired those back then to at least have the grounding contacts wired to neutral. Today I found another outlet that I think he might have missed, because of a piece of furniture. To see if it had been tied to neutral I measured between the contacts and I am getting around 100VAC between either plug contact and grounding contacts of the outlet. ...the F*** ?!?Edit: Removed some hatred.

author: sokoloff
author_rank: Super Contributor
timestamp: July 29, 2018, 10:11:08 am
content: In the US, theonlyplace the ground and neutral contacts are bonded together is at the first service entrance to the house.I’m surprised (and more than a little skeptical) that EU standard is to cross-connect them at each outlet.Such cross-connections seem unsafe to me.

author: frozenfrogz
author_rank: Frequent Contributor
timestamp: July 29, 2018, 10:16:47 am
content: Yes, it is unsafe and shite. Sadly, for buildings erected pre 1974/75, it is absolutely fine* to only have two-strand wiring running in the walls.For what you are proposing a third strand is needed.*fine as in that’s how you did it at the time (state of the technology rule), therefore you do not have to change a thing unless you are making major changes to the installation. In that case you are legally bound by whatever is current IEC standard procedure at that time.

author: senso
author_rank: Frequent Contributor
timestamp: July 29, 2018, 01:37:22 pm
content: Are you calling earth/PE ground?Because the protective earth contacts should not be wired to ground..

author: frozenfrogz
author_rank: Frequent Contributor
timestamp: July 29, 2018, 03:13:50 pm
content: Quote from: senso on July 29, 2018, 01:37:22 pmYou would be correct if there was a separate PE wire. However, this is electrical installation from the 1950s (actual date unknown) and we are talking two-wire system L+PEN.How is that called? TN-C system?Regarding color coded wiring: There are all the colors in all different positions. Prime example of a SNAFU. This is a mess.

author: TERRA Operative
author_rank: Super Contributor
timestamp: July 29, 2018, 04:21:24 pm
content: Come to Japan, we don't even have earthed outlets in most domestic installations outside the kitchen/bathroom.I had to pay a dollar or two extra for each outlet to upgrade them all to earthed types throughout the house when I built my place.... (We use a 200v/100v split phase system similar to the US)I also had to upgrade the supply to 100A (50A per phase), the usual is more around 30A per phase, not enough for my future workshop!Coming from Australia with super strict electrical regulations and 80A, 230V 3-Phase supply, it blows my mind how loose things are here.

author: Benta
author_rank: Super Contributor
timestamp: July 29, 2018, 04:56:35 pm
content: What you have is a Live/Neutral installation (2 wires). Nothing wrong with that, as long as you have a GFCI/RCCD.Earth/ground/PE do not even come into play here, you don't have them.If you want to rewire the whole apartment, feel free, but it's to my mind unnecessary.

author: helius
author_rank: Super Contributor
timestamp: July 29, 2018, 05:03:59 pm
content: Quote from: frozenfrogz on July 29, 2018, 10:16:47 amIt may be legal to leave the existing two-conductor wiring in place. What is NOT okay is to bond neutral to PE at the outlet, since that puts live electricity on the chassis of connected equipment.

author: Benta
author_rank: Super Contributor
timestamp: July 29, 2018, 05:15:45 pm
content: Quote from: helius on July 29, 2018, 05:03:59 pmYeah, missed that one. Wiring the earth terminal to Neutral is a certain recipe for disaster. Leave the earth terminal unconnected at the receptacle. I'm astounded that an electrician would even consider doing this.

author: tooki
author_rank: Super Contributor
timestamp: July 29, 2018, 05:26:32 pm
content: Quote from: senso on July 29, 2018, 01:37:22 pmIn English electrical terminology, "earth" and "ground" are absolute synonyms. North America tends to say "ground", the other countries say "earth", but they mean the same thing, in that they can be used to mean either a protective earth conductor, or a local earth connection (like a rod in the soil), as well as the zero-voltage point in a circuit. That's why usually you specify exactly what you mean, if there's any ambiguity in context. (One tip: if we say "earth" or "ground" without "the", we likely mean an earth conductor or zero-voltage point, but not the soil. Whereas if we say "theearth" or "theground", it could also mean the soil. It's not a 100% guarantee, but it often gives you a hint. E.g. "the green wire is the ground" means the green wire is the PE conductor, "connect this to ground" means "connect to the PE or zero-V point", and "connect this to the ground" could be either, but context would give you more clues.)Readhttps://en.wikipedia.org/wiki/Earthing_systemto get an idea how the terminology is used in context.As I understand the OP's post, when they originally moved in, the sockets had the L contact connected to the L conductor, the N contact connected to PEN conductor, and the PE contact connected to nothing. The OP had an electrician rewire them so that the PE contacts are connected to the PEN conductor as well.Quote from: senso on July 29, 2018, 01:37:22 pmThis is identical to saying "because the protective earth contacts should not be wired to earth". So what do you mean, since earth alone can mean a PE conductor, or a local earth connection?1. PE contacts should not be connected to a PE conductor at all?2. PE contacts should not be connected to a PE conductor that is locally earthed with an earth rod at the service entrance?3. PE contacts should not be connected to a local earth connection (with no connection to a PE conductor)?Or something else?

author: sokoloff
author_rank: Super Contributor
timestamp: July 29, 2018, 05:47:43 pm
content: Quote from: Benta on July 29, 2018, 05:15:45 pm@helius and @Benta: yes, exactly my point. OP made his apartment more dangerous with this change, not less...

author: amyk
author_rank: Super Contributor
timestamp: July 29, 2018, 05:48:16 pm
content: Quote from: TERRA Operative on July 29, 2018, 04:21:24 pmCurious to know what the (accidental) electrocution rate is in Japan. I've seen the two-pole unpolarised plugs there too, they are the norm.(Is the 20 fewer volts significant in reducing the risk of electrocution? Probably not...)

author: frozenfrogz
author_rank: Frequent Contributor
timestamp: July 29, 2018, 06:22:41 pm
content: For further clarification, I appended a picture (sorry, it’s in German).As you might have guessed, I am not an electrician, but from my understanding the situation is as follows:In case there was only L + N available, (D: SchuKo) wall outlets with ground contact would not have been allowed to install at any time. Only outlets for insulation protected devices would be suitable. -> square in a square symbolIf L + PEN was available, L has to be wired to the outlet socket, PEN has to be wired to the ground contact and then to the other outlet contact. Reason: In case the connection between outlet contact and ground contact fails, ground contact is still connected to PEN.If L + PE + N is available, the issue is clear in regard to wiring, but you have also an easy option to retrofit an RCD (GFCI/RCCD however the correct term is - on a side note, the RCD won’t save you if PEN breaks before the RCD).In this case we are looking at L + PEN (I guess, since outlets with ground contact would have never been allowed otherwise).Failure mode 1: Ground contact not connected to PEN, connected device fails, housing gets shorted to live -> people will die.Failure mode 2: Ground contact not connected to PEN, PEN breaks inside the wall, device won’t work, defective device still could kill someone.Failure mode 3: Ground contact connected to PEN, connected device fails, housing gets shorted to live -> circuit breaker might trip, people might survive.Failure mode 4: Ground contact connected to PEN, PEN breaks inside the wall, housing gets live -> people will die.Both options are both not satisfying, but connecting the ground contact to PEN inside the outlet favors the odds of a device failing over the odds of PEN failing inside the wall.At least that is as far as my understanding goes. In case you disagree: Please elaborate, I am willing to learn more about all of this.

author: Benta
author_rank: Super Contributor
timestamp: July 29, 2018, 06:59:55 pm
content: A 50s installation may have been made like your drawing back then. I interpret your drawing as Live plus PEN (SL/Mp = Schutzleiter/Massenpotenzial).However, you have no idea what is being supplied from the utility today. It could be that you get L + N, and I always treat L + N as are both "live".The '59/'69 workarounds are not regarded as safe today. A L + N with RCD is regarded as safe. Wiring N to PE is NOT safe and not something you should do. Connecting N to PE is a task only for the utility at their distribution point.

author: tpowell1830
author_rank: Frequent Contributor
timestamp: July 29, 2018, 07:01:52 pm
content: Quote from: frozenfrogz on July 29, 2018, 10:06:52 amIf you are at all concerned that the wiring in the walls are prone to break or are broken, that is not in the outlet box, your battle is already lost and you should rewire the entire house. You have to trust the wiring is sound inside the walls and no amount of "safety" wiring at outlet will save this situation. In my experience, the biggest dangers happen when a home is determined to have the 2 wire system and owner decides to upgrade to the modern version. Wiring gets disconnected or cross-connected or other mistakes are made that makes the wiring 10 times more dangerous than if you had only left it alone.There are many threads on this forum that discuss safe home wiring setups and practices, as well as the configuration of different earth grounding techniques. If your house is not setup properly then there is concern. In the USA, the early 2 wire wiring in homes did not have an earth ground. The proper way in which to update/upgrade these homes to current standards is to start over and remove all wiring and replace them with proper wiring with proper ground configurations with a licensed contractor that follows all of the proper codes. Sometimes this is impossible without tearing down parts of the home structures, so is often deemed to be not economically viable.IMHO, the early 2 wire home wiring decisions were the worst possible decisions and we are all still suffering from this. I understand it was all new technology back in the day, but the fact that there are so many legacy homes with this system is a monumental problem. I have seen many homes here in the US that the decision was made to modernize the wiring and the result were almost always the same, very compromised and unsafe at best. The better decision would have been to let sleeping dogs lie if there were no obvious problems.Just my 2 cents...

author: PartialDischarge
author_rank: Super Contributor
timestamp: July 29, 2018, 07:09:09 pm
content: Quote from: TERRA Operative on July 29, 2018, 04:21:24 pmRight

author: frozenfrogz
author_rank: Frequent Contributor
timestamp: July 29, 2018, 07:35:03 pm
content: Just so you are not under a wrong impression: I am not going to rewire anything on my own. That is the job for an electrician paid by the owner.However, I am trying to understand what makes what unsafe for what reason (i.e. how not to get killed in my own rooms).Quote from: Benta on July 29, 2018, 06:59:55 pmHow would one implement an RCD if there is no separate PE? From what I am reading DIN VDE 0100-530 strictly forbids installing an RCD on a TN-C system.If it was possible to put an RCD on L + N in the circuit breaker / control cabinet and running L + N to the outlets from there without connecting the grounding contacts, than most of the old installations would have been updated that way. I have never heard of that possibility though. Or what am I not getting here?Thanks and kind regards!P.S. getting a Beha 9080D tester some time next week.

author: Benta
author_rank: Super Contributor
timestamp: July 29, 2018, 09:05:03 pm
content: Quote from: frozenfrogz on July 29, 2018, 07:35:03 pmAn RCD does not need PE. The RCD measures current in L minus current in N. If there is a difference, you have a ground fault.Simple.Also, TN-C is not applicable to your apartment. This is the utility's responsibility.Apparently you know just enough to be very dangerous.

author: amyk
author_rank: Super Contributor
timestamp: July 29, 2018, 09:12:37 pm
content: It is interesting to look at the wiring standards in different countries and wonder just how much effect they have on safety - as a comment above mentioned, ungrounded 2-wire sockets are still common in Japan yet I'm not sure if they have a higher electrocution rate. At the other end of the scale there's the British huge fused plugs and sockets, but are they actually all that much safer? Really makes you think...

author: Bratster
author_rank: Frequent Contributor
timestamp: July 29, 2018, 10:00:28 pm
content: Well here in the US while I have grounded three prong Outlets at my house,I would say half maybe even two-thirds of the devices that I have are just two prong, some polarized some non-polarized plugs.So just having two prong outlets itself is not necessarily an issue.But with that being said I would always want a 3-prong grounded receptacle.Sent from my Fi Moto x4 using Tapatalk

author: frozenfrogz
author_rank: Frequent Contributor
timestamp: July 29, 2018, 10:09:31 pm
content: Quote from: Benta on July 29, 2018, 09:05:03 pmI am not claiming to know what it takes to be an electrician - which is why I am not rewiring stuff on the mains side etc.Maybe it is dangerous smattering - I somehow managed to survive to this day though.I know how an RCD works and that PE is not needed for the measuring side of things, but my question is how you would be able to implement what you propose in practice? -> In regard to VDE et.al.You are claiming, TN-C would not be applicable in my apartment. That would be correct if PEN got split into PE and N for the building, forming TN-S, but that is simply not happening. In that case retrofitting an RCD would also be no problem and there would be no discussion in the first place.If the house electric system was only two-wire L+N, CEE 7/3 outlets would be illegal to install there in the first place.Outlets with grounding contact have to be grounded all the time. An RCD on that system would mean, that PEN would also be switched, thus breaking the grounding rule. That is why PEN gets split before the RCD and all grounded outlets have to be tied to PE and the building needs a separate grounding rod (obligatory for all TN-C-S).I might be wrong here, but that is my state of knowledge in regard to VDE 0100-410.Please elaborate. I really try to understand your arguments.

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 29, 2018, 10:55:43 pm
content: Quote from: helius on July 29, 2018, 05:03:59 pmThere was a recent video from Fran Blanche doing just that. Her claim was that it was allowed in that specific instance because the place is very old.

author: Zucca
author_rank: Unknown
timestamp: July 30, 2018, 07:46:49 am
content: Quote from: Benta on July 29, 2018, 09:05:03 pmUh? And where is the difference L-N current suppose to go if there is no wire PE to carry that current away?Confused.

author: Benta
author_rank: Super Contributor
timestamp: July 30, 2018, 09:21:11 am
content: Quote from: zucca on July 30, 2018, 07:46:49 amTo ground, of course, eg, a water pipe or whatever. That's why it's called a ground fault.

author: Jeroen3
author_rank: Super Contributor
timestamp: July 30, 2018, 09:26:28 am
content: For an RCD to work, somewhere upstream of the RCD something must be connected to ground. Otherwise a fault will not make a circuit capable of tripping the RCD.Eg: A RCD on the output of a transformer has no effect. One of the output terminals must be grounded.I think we can all agree on this?

author: Benta
author_rank: Super Contributor
timestamp: July 30, 2018, 09:30:45 am
content: Quote from: Jeroen3 on July 30, 2018, 09:26:28 amYes, of course. This usually happens at the utility transformer and depending on code/country at the building. A fully floating supply would not require an RCD, as no ground fault is possible.

author: Zucca
author_rank: Unknown
timestamp: July 30, 2018, 10:12:34 am
content: Quote from: Benta on July 30, 2018, 09:21:11 amThat's why a RDC with PE is much better than a RDC without PE because the faulty current will find his way through the PE cable.On top of that with PE the RCD will trip without you touching the faulty device and carring the current to the ground with your body. Worst case of course.Nobody will die, because the RDC should be designed properly; still you will feel the 220VAC on your body. Not nice.This is why I think a RDC must have a PE to work properly at 100%, yes it will work also without but in a safety point of view the two system are not even comparable.

author: Jeroen3
author_rank: Super Contributor
timestamp: July 30, 2018, 10:52:35 am
content: Theoretically an RCD can still work without any ground, current just has to run trough some different path around the RCD. Some other live or neutral for example.But these faults are rare.

author: capt bullshot
author_rank: Super Contributor
timestamp: July 30, 2018, 11:40:46 am
content: Quote from: helius on July 29, 2018, 05:03:59 pmConnecting the PE pin to Neutral is the usual way to deal with 2wire-wiring here. You'll find many homes using this old standard. Of course, one cannot use this wiring for new installations, but there's no obligation to change it.So if you're working on such old installations, always triple check, don't expect anything to conform to todays conventions.

author: sokoloff
author_rank: Super Contributor
timestamp: July 30, 2018, 11:43:05 am
content: Quote from: frozenfrogz on July 29, 2018, 10:09:31 pmThis is not the case in the US under National Electric Code. In legacy buildings, we are allowed to use a ground fault interrupter to protect circuits which have 3-prong (grounding) outlets downstream. Those outlets need to have a sticker saying “No equipment ground” on/near them. NEC 250.114(3).It is not permissible to cross-connect ground and neutral in such outlets (or anywhere other than the initial service entrance).It is true that grounded outlets with connected grounds need a full-time (unswitched) ground, but your exact situation is covered as an exception to that rule under NEC.

author: amyk
author_rank: Super Contributor
timestamp: July 30, 2018, 11:53:59 am
content: https://en.wikipedia.org/wiki/Ground_and_neutralhttps://en.wikipedia.org/wiki/Earthing_systemSome good reading for those interested. It's interesting how different it is across countries.