General > General Technical Chat
Mains sockets with no earth
(1/10) > >>
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)
Navigation
Message Index
Next page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod