Mains sockets with no earth - Page 1
Forum section: electronics / general

author: michael@metgen.tech
author_rank: Contributor
timestamp: January 18, 2021, 06:19:48 am
content: I live in Japan (100V 50Hz here - it's 60Hz in West Japan). In my flat I have a range of electrical sockets. The distribution board appears to work in much the same way as I understand it does in the US - 0V Ground, +100V for most circuits and 200V (+100V to -100V with ground at 0V) for larger appliances. All connections fused and an RCD.The problem that I am struggling with is that only the sockets in the kitchen and bathroom have earth connections (I don't think that the earth wire even runs to the back boxes) while many of my instruments run off three-pin plugs.My thoughts and actions so far:It seemed like a bad idea to link up all the earth wires without having a connection to earth at the distribution box (I presume that one short and every metal case goes live)I run a three-core/pin extension cord from my kitchen for those devices that aren't fully insulated/have metal cases - not a tidy solutionWithout an earth connection I don't have RCD protection - is that right?Just removing the earth wires or not connecting them runs the risk that individual uninsulated cases go liveAnd yes, you're right, at 100V (15A max) a kettle never boils, watched or otherwiseI'm moving in a few weeks and am considering what changes I should make to the electrics in my new place (everywhere seems to be wired similarly). Tearing all the walls apart to put cable through batons every 30cm is not my preferred option.Does anyone have any thoughts or suggestions?Am I missing something or are the standards here strangely lax?Thanks!Mike

author: james_s
author_rank: Super Contributor
timestamp: January 18, 2021, 06:43:42 am
content: I would just plug them in with an adapter that doesn't connect the ground pin to anything. It isn't ideal, but it isn't a rare thing to do. Just make sure your gear is in good shape. If you want to be safer, find a ground somewhere in the place and run a wire from that to a power strip you plug your equipment into.

author: tom66
author_rank: Super Contributor
timestamp: January 18, 2021, 09:49:03 am
content: You still have RCD protection without an earth. RCDs work by detecting L-N imbalance, not earth current. If you touch a live terminal while your feet are wet on a conductive floor, current flows between L, through you, and into earth. The RCD will register L-N imbalance and trip, hopefully before your heart does...An earth connection is primarily there to protect you against cabling/heating elements becoming loose and energising the case, which would not be detected by an ordinary RCD if the earth was not connected, and could present a serious electric shock hazard. You can probably guess that the chances of this happening in an oscilloscope are practically nil, but higher for power tools, washing machines, etc.The earth connection does also perform a useful task for EMI reduction, so many larger electrical appliances (e.g. computers, big TVs, etc.) use it as well - and in many cases this also allows these appliances to be Type I single-insulated so the earth is important from a regulatory point of view (double insulated conductors and design processes are not used) but again the likelihood of a cable becoming loose and energising the appliance case is quite low.

author: Daixiwen
author_rank: Frequent Contributor
timestamp: January 18, 2021, 11:49:47 am
content: Not having the earth connected can also cause a minor discomfort when you touch the metallic casing of a device, if it's earth is not connected but it has a filter on the power input. In that case the Y capacitors in the filter will put the chassis at a voltage between live and neutral. The impedance is high so there is no danger, but you can feel a tingle when you touch the chassis. I remember having this problem with an old aluminium macbook, and it took me a while to realize it was because the cord was connected to a socket without earth.

author: tszaboo
author_rank: Super Contributor
timestamp: January 18, 2021, 12:01:29 pm
content: I don't know how they run wire in Japan, but I have to assume the wires are in a conduit.I was in similar situation in my house when I bought it. I had the entire fusebox replaced with modern stuff, and had them install earth in all the plugs. They also replaced all the outlets, fixed all the wiring that was't up to code. I took about 8 hours, and payed about 2000 EUR for it. The most expensive part was the 2 electrician's hourly rate, after that the new fuse box. There was no chiseling or anything like that, minimal dust. Now everything is up to the latest electical code, and I sleep good.Do you rent or is the flat yours? (I know that flat usually means rental)

author: themadhippy
author_rank: Super Contributor
timestamp: January 18, 2021, 12:59:59 pm
content: Quoteif you dont have an earth your rcd will not work.were does the fault current go as there is no path for it to travel.Dont believe me then remove your main incoming earth and bonding and short earth to live or neutral somewhere on the consumers side and see how long it takes for the rcd to trip

author: exe
author_rank: Unknown
timestamp: January 18, 2021, 01:11:30 pm
content: Please don't ground to the heating radiator.

author: dzseki
author_rank: Frequent Contributor
timestamp: January 18, 2021, 01:22:07 pm
content: Quote from: themadhippy on January 18, 2021, 12:59:59 pmI think he meant Protective Earth, right after the quoted sentence he follows with this:QuoteQuote from: themadhippy on January 18, 2021, 12:59:59 pmI don't know how is the PE and N overthere, but at my place they certainly very close to eachother Ohmic wise, even without any strapping. I wouldn't advise to anyone to try that...

author: nightfire
author_rank: Frequent Contributor
timestamp: January 18, 2021, 02:02:31 pm
content: It might as well be that the net system there is no TN-System like in West Europe or USA, but most likely a TT system. Here you have no PE connection directly to the mains transformer, but a local ground connection with RCD to protect you.https://en.wikipedia.org/wiki/Earthing_systemAs I have seen, TT is mostly the official way to do that in Japan, like IT in norway...Anecdote: early in germany, you had in the 1950ies such "Kraftstrom" Outlets in the kitchen, because more powerful appliances like heaters and ovens were expected. And heating elements cause leakage currents, that had to be dealt with. More important, most appliances in a kitchen were nearby, so you need protection against faults that would involve earth to clear a fault.In the living room etc., you had "Schweineschnäuzchen" (pigs noses) as outlets: L+N, no ground. AND you had to allow for (IIRC) more than 2.5 Meter distance between outlets. Because: In case of failure of maybe some lamp or radio, even when you would touch it, as long as you could not touch ground/earth (maybe the metal housing of a radio), everything was fine.Of course, if you had central heating, you had to install grounded outlets, which lots of people did not do...

author: JohnnyMalaria
author_rank: Super Contributor
timestamp: January 18, 2021, 03:41:12 pm
content: Quote from: michael@metgen.tech on January 18, 2021, 06:19:48 amI would consult the standards first and certainly don't assume that the US way of wiring would necessarily work out well.

author: bdunham7
author_rank: Super Contributor
timestamp: January 18, 2021, 03:52:07 pm
content: Quote from: themadhippy on January 18, 2021, 12:59:59 pmGFI does not depend on having an earth connection, nor does it care what the path is for current to travel outside of the two wires it monitors. If a current is flowing through you, then that amount of current will be missing from the return current in the neutral. GFI sees the imbalance and trips.

author: Red Squirrel
author_rank: Super Contributor
timestamp: January 18, 2021, 03:56:18 pm
content: You could try to ground to the water line but these days with pex that can be hit and miss as the line might turn to pex at some point before it goes into the actual ground. Worse case scenario run stuff off a GFCI, it will at least protect you from ground faults. I've tested this and it does work. For Christmas light stuff I often need to convert from 2 prong to 3 prong because stuff like timers only have 2 prong and the extension cord, power bars etc are 3, so I just made a converter box that has a GFCI.

author: bdunham7
author_rank: Super Contributor
timestamp: January 18, 2021, 04:11:38 pm
content: Quote from: michael@metgen.tech on January 18, 2021, 06:19:48 amGFI/RCD does not depend on there being a ground wire, although if the circuit is totally isolated (not ground referenced) the behavior may be unpredictable in fault situations. You would want to know what your RCD trip level is. US-style GFIs trip at 5mA or so, which gives good protection against electric shocks. You could add a GFI socket to your workbench outlet if you wanted the extra protection--if they are available there.

author: themadhippy
author_rank: Super Contributor
timestamp: January 18, 2021, 04:33:23 pm
content: QuoteThe neutral -earth link is done on the suppliers side in the uk,well apart from the rare TNC arrangement, so disconnecting the consumer side main earth there is no path to earth via neutral,in fact when carrying out a test of an electrical installation one of the tests is to confirm the resistance between earth and neutral is greater than 1 Meg ohmQuoteIf your of a nervous disposition use a resistor, a value upto 1666.6667 ohms should work on a 30ma trip in the uk between neutral and earthQuotewhilst the rcd dosnt have an earth connection it still relies on the circuit somewhere being connected to earth,otherwise theirs nowhere for the imbalance current to flow.If the experiment mentioned above is to scary try putting an rcd on the secondary of an isolating transformer and connect the output to earth ,what happens?

author: bdunham7
author_rank: Super Contributor
timestamp: January 18, 2021, 05:08:39 pm
content: Quote from: themadhippy on January 18, 2021, 04:33:23 pmTrue, in a truly isolated system the RCD won't trip because there is no fault current. But since there's no fault current, there's no shock and nothing to protect from.

author: james_s
author_rank: Super Contributor
timestamp: January 18, 2021, 11:51:46 pm
content: Quote from: themadhippy on January 18, 2021, 12:59:59 pmSure it will. The ground wire in a GFCI/RCD passes straight through and does not connect to any of the active circuitry. Neutral is tied to earth somewhere in the domestic wiring system of every developed nation as far as I'm aware, and the GFCI works by detecting an imbalance between live and neutral current which indicates a leakage path. Since neutral is bonded to earth somewhere, the live is always referenced to earth whether you've got a safety earth or not.

author: JohnnyMalaria
author_rank: Super Contributor
timestamp: January 19, 2021, 12:23:01 am
content: Quote from: james_s on January 18, 2021, 11:51:46 pmEarthing arrangements vary significantly across the - well - earth.https://en.wikipedia.org/wiki/Earthing_systemI find it very disturbing that predominantly North American advice is being given for a situation using a different earthing system. Before modifying any electrical wiring in a country you aren't familiar with, educate yourself.I moved to the US from the UK. The electrical systems are utterly different. If I started (re)wiring something in a US house using my UK understanding of electricity, I'd probably be either (i) dead or (ii) in prison for killing someone.

author: bdunham7
author_rank: Super Contributor
timestamp: January 19, 2021, 01:04:35 am
content: QuoteThe OP is in Japan. Split-phase, likely what you would call 'TT' earthing. RCD (not really a 'North American' term) is highly appropriate and effective.For some reason the US system seems hard to understand for those who haven't seen it. OTOH, I have no problem understanding other systems in theory--including India, Japan and continental Europe with their need for two-pole appliance switches--I do find the actual installations in the UK to be a bit odd. But none of it should be all that hard theoretically, at least in a home installation. The specifics just take a bit of study.

author: amyk
author_rank: Super Contributor
timestamp: January 19, 2021, 01:06:41 am
content: Oddly enough, the first thing I thought of when I read the title was "Japan"...As far as I know, they are the newest country to still have predominantly ungrounded outlets. They are also the only country to have "metric" mains voltage.

author: themadhippy
author_rank: Super Contributor
timestamp: January 19, 2021, 01:14:31 am
content: Quoteso if we don't need an earth why don't we use an rcd on the secondary of an isolating transformer?after all thats a circuit without an earthQuotenot on the consumers side,otherwise your rcd/gfi would be permanently tripped

author: JohnnyMalaria
author_rank: Super Contributor
timestamp: January 19, 2021, 01:14:52 am
content: Quote from: bdunham7 on January 19, 2021, 01:04:35 amThe UK uses a ring circuit for the most part since it allows a narrower gauge of wire to be used for a given power requirement. Radial/spur/star is less common. You'll find both in a given home.

author: themadhippy
author_rank: Super Contributor
timestamp: January 19, 2021, 01:48:33 am
content: Quoteslowly the uk is moving away from ring finals,more and more sparks ,mainly the younger ones or those new to the trade ,dont like em and would rather struggle getting 2 larger conductors into a terminal,there fear is of the cable being overloaded if one leg is broken,which whilst true,the chance of a broken wire happening without somebody fiddling were they shouldn't or a badly installed installation are fairly low

author: Monkeh
author_rank: Super Contributor
timestamp: January 19, 2021, 02:17:02 am
content: Quote from: themadhippy on January 19, 2021, 01:14:31 amYou need a path to 'earth'. That doesn't have to be the CPC. Technically you need a path to the other side of the winding at the transformer, which happens to be intentionally connected to the literal earth.Quote from: themadhippy on January 19, 2021, 01:48:33 amIt's worth moving away for the sheer time saved in testing and future fault finding. Most circuits do not need to be 32A anyway.

author: JohnnyMalaria
author_rank: Super Contributor
timestamp: January 19, 2021, 02:17:13 am
content: Quote from: themadhippy on January 19, 2021, 01:48:33 amI relate to this:https://youtu.be/l5Mmz1OnCR8

author: michael@metgen.tech
author_rank: Contributor
timestamp: January 19, 2021, 02:26:50 am
content: Wow! I must admit that I thought I had missed something simple but actually there are a lot of different views. Thank you all very much!I should probably have said that I originally come from the UK and have struggled to get my head around the local regulations (they are, after all, in Japanese). I could read about the US regs and started to build my understanding of Japan from those.So, it sounds to me as though I should install some three-pin sockets (US style), on extension cords, with the earth connectors disconnected from each other - that would produce the same effect as cutting off the three-pin plugs and putting on two-pin plugs. Then I need to stop worrying about the absence of an earth connector?On the RCD front, I always thought that they were to guard against earth faults... so I don't understand how they can work without a reference to earth.Best,Mike

author: JohnnyMalaria
author_rank: Super Contributor
timestamp: January 19, 2021, 02:28:19 am
content: Quote from: michael@metgen.tech on January 19, 2021, 02:26:50 am"Mains sockets" and "earth" gave you away

author: Monkeh
author_rank: Super Contributor
timestamp: January 19, 2021, 02:30:13 am
content: Quote from: michael@metgen.tech on January 19, 2021, 02:26:50 amThey are to protect against current returning to its source (the side of the transformer winding connected to neutral) via a path other than the neutral. Said winding is also connected to earth, and returning via the earth conductor or the greater mass of earth is called an 'earth fault'. They need no reference to this - they measure the difference in current between the line and neutral conductors. Any difference must be returning via an alternate path.Quote from: JohnnyMalaria on January 19, 2021, 02:28:19 amAt least he didn't call them plug sockets..

author: james_s
author_rank: Super Contributor
timestamp: January 19, 2021, 03:17:39 am
content: Quote from: themadhippy on January 19, 2021, 01:48:33 amI have mixed thoughts on the ringmain concept. It has clear advantages, although the concerns you mention are valid. Lots of things are ok *IF* properly installed and nobody has mucked with them but that's a big IF, especially in older houses where the likelihood of somebody having messed with something only increases with time. On the other hand it's not like those concerns apply only to a ringmain, over here we have these stupid spring loaded backstab terminals on receptacles and switches, or rather on the cheap hardware sold for domestic use, commercial "spec grade" and hospital grade forbids them. I've had problems on several occasions with those, once in my own house and several I fixed for other people, one that very, very nearly set the house on fire. I can only wonder how many house fires of indeterminate and "electrical" cause have originated with those. The annoying arc fault breakers the NEC mandates now for new construction are a band-aid over the problem, the tradesmen love those push-in terminals because they're so quick and easy to install but I bet most don't use them in their own house.

author: vk6zgo
author_rank: Super Contributor
timestamp: January 19, 2021, 07:26:27 am
content: Quote from: bdunham7 on January 18, 2021, 03:52:07 pmYes, another name for such devices is "core balance relay".If the current flow in the L & N lines is equal, the relay is "balanced" & does not operate.If the currents are not equal, the relay operates, opening the circuit for both L & N.

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: January 19, 2021, 08:34:51 am
content: Quote from: bdunham7 on January 18, 2021, 05:08:39 pmIf you somehow manage to connect your arms/hands to either terminal, even a portion of any isolated mains will do you in. All it takes is enough to fibrillate the heart. However, if the supply is earth bonded and protected with a RCD, chances are much higher that you wont be sitting there becoming burnt toast.

author: Brumby
author_rank: Unknown
timestamp: January 19, 2021, 09:37:25 am
content: Quote from: vk6zgo on January 19, 2021, 07:26:27 amNow you're showing your age.....

author: tooki
author_rank: Super Contributor
timestamp: January 19, 2021, 09:56:42 am
content: Quote from: themadhippy on January 19, 2021, 01:14:31 amUhhhh… what? No. The RCD isn't looking at what's happening upstream of it (i.e. in the power grid). It simply has inputs and outputs for the L and N, and if the current that flows in isn't the same as what flows out, it trips. If N and PE are tied together at the consumer unit, that's still upstream of the RCD, and thus irrelevant to it.In fact, RCDs are used when it's impractical to add an actual protective earth conductor, precisely because theydoadd protection when earth is missing.

author: themadhippy
author_rank: Super Contributor
timestamp: January 19, 2021, 12:24:33 pm
content: the post that started it allQuotewithout earth there is no return path so would the experts like to explain how a current can flow in what is effectively an open circuitQuotei meant the consumers side,or output, of the rcdQuoteagain i ask,if earth is missing how does a fault current flow?

author: bdunham7
author_rank: Super Contributor
timestamp: January 19, 2021, 02:36:52 pm
content: Quote from: themadhippy on January 19, 2021, 12:24:33 pmIf there truly is no ground reference for both the voltage and your feet, indeed no current will flow and the RCD will not trip. But it doesn't need to--because there's no fault current to worry about. The RCD is still standing by for any faults that develop that result in current flowing through you other than those that result from you touching both sides of the power.

author: Monkeh
author_rank: Super Contributor
timestamp: January 19, 2021, 03:20:57 pm
content: Quote from: themadhippy on January 19, 2021, 12:24:33 pmAre we accidentally equating earth with the CPC?The neutral, sort of by definition of being neutral, is connected to earth (the 'greater mass of earth', the soil under your feet). You do not need an earth wire in an installation for current to flow via the literal earth.

author: Someone
author_rank: Super Contributor
timestamp: January 19, 2021, 09:47:57 pm
content: Quote from: michael@metgen.tech on January 19, 2021, 02:26:50 amNo, equipment that has a mains earth pin usually relies on it for safety and/or EMC. Removing that connection is a very very bad idea.If you don't understand the standards/requirements (which is plainly obvious from your posts so far) then suck it up and hire a professional to do the job. Just ask an electrician to put modern grounded points everywhere and its done.

author: jmelson
author_rank: Super Contributor
timestamp: January 19, 2021, 11:47:22 pm
content: Quote from: michael@metgen.tech on January 19, 2021, 02:26:50 amThey compare current on line and neutral. If the current is the same, the devices must be OK, all current flows out one outlet prong and back on the other. If the currents DO NOT match, then the current MUST be flowing out of the device somewhere, and typically that would be through a person's body.The comparison is done by passing both L and N wires through a ferrite core. Only equal and opposite currents cancel out.Japan generally has no ground pin on any residential sockets, but they do in industrial and lab settings.Jon

author: michael@metgen.tech
author_rank: Contributor
timestamp: January 20, 2021, 03:38:36 am
content: Quote from: Someone on January 19, 2021, 09:47:57 pmYour comment doesn't really make sense - obviously not coming at this from a Japan perspective.The standard in Japan is to NOT have any earthing. There are no "modern grounded points". The problem I have is that I have equipment that is not Japanese, has earth connectors and, for some, an uninsulated metal case. So "hiring a professional" won't change anything. I am trying to better understand of the risks that I am actually exposed to by following the local standards and if there are any workable mitigations.Mike

author: michael@metgen.tech
author_rank: Contributor
timestamp: January 20, 2021, 03:42:15 am
content: Quote from: jmelson on January 19, 2021, 11:47:22 pmThanks. Obvious now that I look at the insides of one.Quote from: jmelson on January 19, 2021, 11:47:22 pmMy experience too.Thanks,Mike

author: Zero999
author_rank: Super Contributor
timestamp: January 20, 2021, 09:21:02 am
content: It's true that RCDs will work, if the appliance lacks an earth connection, but an earth is required at the supply side. RCDs need the mains supply to be earth referenced, so they won't work if the entire circuit lacks an earth connection. Try connecting an RCD to the secondary of an isolation transformer and note that it won't trip, if either conductor is connected to earth.

author: nctnico
author_rank: Super Contributor
timestamp: January 20, 2021, 10:03:53 am
content: Quote from: themadhippy on January 18, 2021, 12:59:59 pmIn that case you don't have a problem. If there is no ground the current can flow into then you can't get a shock!Quote from: Zero999 on January 20, 2021, 09:21:02 amAlmost right. RCDs need the neutral to be earth referenced at the primary side. But after that you don't need earth in the installation. It is assumed the building is somehow grounded (and in 'wet' rooms like the bath room it is often mandatory to ground the floor and every metal object).

author: Someone
author_rank: Super Contributor
timestamp: January 20, 2021, 11:38:09 am
content: Quote from: michael@metgen.tech on January 20, 2021, 03:38:36 amhttps://ja.wikipedia.org/wiki/%E9%85%8D%E7%B7%9A%E7%94%A8%E5%B7%AE%E8%BE%BC%E6%8E%A5%E7%B6%9A%E5%99%A8QuoteSo yeah, there is that whole its the recommended way to do it thing, in your specific country, according to their specific standards. Some of us havedohave a solid international view.

author: Zero999
author_rank: Super Contributor
timestamp: January 20, 2021, 01:24:40 pm
content: Quote from: nctnico on January 20, 2021, 10:03:53 amThat's what I said. Read it again.

author: michael@metgen.tech
author_rank: Contributor
timestamp: January 21, 2021, 02:00:13 am
content: Quote from: Someone on January 20, 2021, 11:38:09 amExcellent, I had not found that, thank you. The only issue with my new place is that it was built in 2002 - pre the 2005 changes. Also, unless you have lived here, you would find it hard to believe how tradesmen, and anyone else for that matter, apply regulation. Dealing with them generally feels like pushing a ball up hill with a piece of wet spaghetti!It turns out that I may have to have new cables run for an electric oven. If so I can ask the electrician to run an earth wire as well.I presume that with a 200V supply the Earth is at the mid point?

author: bdunham7
author_rank: Super Contributor
timestamp: January 21, 2021, 10:16:11 pm
content: Quote from: Ed.Kloonk on January 19, 2021, 08:34:51 amThis has been raised before in discussions about isolation transformers. Yes, if you grabbothsides, you get buzzed. And if you grab both sides of an earth-referenced RCD/GFI protected circuit, you still get buzzed but if your feet are sufficiently grounded so that additional current also goes to ground through your toes, you might get lucky and have the power shut off. This is why although I advocate the proper use of isolation transformers, I don't advocate using them in a general 'safety zone' sort of way.However, the point remains that no ground is needed for RDC/GFI, although they are a bit pointless if the power source is truly isolated and remains that way with no faults. You can dream up corner case scenarios even for ground-referenced power. Imagine grabbing both sides of a split-phase system with both hands and bare feet on concrete. The leakage to ground may be balance out and thus the GFI won't trip.

author: james_s
author_rank: Super Contributor
timestamp: January 21, 2021, 10:49:12 pm
content: A GFCI is a lot like a seatbelt. It's there to provide some protection in the event that you end up in a really bad situation where you are the most convenient path to ground. It's not there to enable one to be careless with electricity, if you touch a GFCI protected circuit you will probably still get a shock, but hopefully the power will cut quickly enough that it won't be lethal.