Mains sockets with no earth

[michael@metgen.tech]

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 solution
• Without 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 live
• And yes, you're right, at 100V (15A max) a kettle never boils, watched or otherwise

I'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

[james_s]

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.

[tom66]

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.

[Daixiwen]

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.

[tszaboo]

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)

[themadhippy]

You still have RCD protection without an earth.

if 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

[exe]

Please don't ground to the heating radiator.

[dzseki]

You still have RCD protection without an earth.

if 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

I think he meant Protective Earth, right after the quoted sentence he follows with this:

RCDs work by detecting L-N imbalance,  not earth current.

remove your main incoming earth and  bonding and  short earth to live or neutral somewhere on the consumers side

I 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...

[nightfire]

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_system

As 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...

[JohnnyMalaria]

Am I missing something or are the standards here strangely lax?

I would consult the standards first and certainly don't assume that the US way of wiring would necessarily work out well.

[bdunham7]

if 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.

GFI 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. 

[Red Squirrel]

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.

[bdunham7]

• Without an earth connection I don't have RCD protection - is that right?

GFI/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.

[themadhippy]

I don't know how is the PE and N overthere, but at my place they certainly very close to eachother Ohmic wise

The 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 ohm

without any strapping. I wouldn't advise to anyone to try that...

If 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 earth

GFI 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.

whilst 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?

[bdunham7]

whilst 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?

True, 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.

[james_s]

You still have RCD protection without an earth.

if 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

Sure 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.

[JohnnyMalaria]

You still have RCD protection without an earth.

if 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

Sure 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.

Earthing arrangements vary significantly across the - well - earth.

https://en.wikipedia.org/wiki/Earthing_system

I 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.

[bdunham7]

I 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.

The 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.

[amyk]

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.

[themadhippy]

Sure it will

so 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 earth

Neutral is tied to earth somewhere in the domestic wiring system of every developed nation as far as I'm aware

not on the consumers side,otherwise your rcd/gfi would be permanently tripped

[JohnnyMalaria]

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.

The 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.

[themadhippy]

The 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

slowly 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

[Monkeh]

Sure it will

so 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 earth

You 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.

The 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

slowly 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

It's worth moving away for the sheer time saved in testing and future fault finding. Most circuits do not need to be 32A anyway.

[JohnnyMalaria]

The 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

slowly 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

I relate to this: https://youtu.be/l5Mmz1OnCR8

[michael@metgen.tech]

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