Re: [tlug] Japanese Electrical Wiring

[Kalin KOZHUHAROV <me.kalin@example.com>]

minates On Mon, Jan 9, 2017 at 11:51 PM,  <jep200404@example.com> wrote:
> On Mon, 9 Jan 2017 11:55:50 +0100, Kalin KOZHUHAROV <me.kalin@example.com> wrote:
>
>> Many Japanese houses are not wired with earth, just phase+null.
>
> I have long been curious about this kind of stuff in Japan
> and elsewhere. I have taken pictures of outlets and measured
> voltages when travelling.
>
> Please explain the details of phase+null.
>
The grid provides at least two connections, I suppose called phase and
null/zero. Or live (black) and neutral (white). In Japan, in
apartments, there is a separate ground/earth wire (green) that is
connected to some high-power/constantly on appliances outlets on a
sparate screw-on bolt (washer/dryer, microwave, airconditioner, etc.).
This is a separate (3rd) connection that starts(terminates) in/under
the building and does not directly go back to the grid. Most outlets
though are simple non-polarized ones. Practically all extension cords
I've seen used extensively have non-polarized sockets as well.
See https://en.wikipedia.org/wiki/NEMA_connector#NEMA_1

OT: I replaced a light in my apartment once and was terrified to see a
red wire connected to the metal case, but it turned out to be mis-used
for ground. So don't trust the color coding always, or trust but
verify as we say in security.

> What country and/or language is that terminology native to?
>
None, I suppose :-) I am from Bulgaria, lived 18 years in Japan, now
in Germany...

> Obviously, there is 100 VAC at either 50 Hz or 60 Hz,
> with the frequency depending on which end of Japan one is at.
> Do either "phase" or "null" have an electrical connection to dirt somewhere?
>
Yes, in transformer stations I suppose.

> Are all two prong outlets polarized in Japan?
>
Most are not.

> For polarized two prong outlets,
> how common is it for the polarity to be reversed?
>
I have not detected one in 18 years, but I have not been actively
seeking. Given that polarized sockets are rare (1-2%?) and Japanese
are strict in following rules, I'd say very rare.


>> ... touch the case on exposed metal (some of the
>> bolts, if not painted) with a sensitive skin (back of your palm, or
>> cheek if you dare). If you feel any tickle, you have a problem.
>
> I experienced that East Asia, and knew what it meant. It scared me.
> I was meeting with electrical engineers so I asked them about
> grounding practices. None of them had any clue whatsoever about
> how buildings were wired for electrical power and/or ground.
> They were also not the least bit concerned.
> This was in a brand new building in the early 2000s.
>
Yes, they don't learn that in school/university unfortunately...

> After that, I tried to touch only one metal thing at a time.
>
It doesn't help much in the dry season (winter) when your shoes are
wet from the rain...
Install a tester in your sleeve if you are worried ;-)
But hey, those are far from lethal to humans. Electronics are often
damaged though.

Last thing I remember was a NAS plugged in the wrong socket that was
refusing to turn on, I measured 20-25V between case and ground after a
colleague complained about occasional "zaps"...

Being a HAM myself, I am always paying attention to wiring and
grounding, RFI and all the "transient shit" that most people ignore.
It is often a pain that helps in the long run (eventually) :-)

Cheers,
Kalin.

/Sent from 220V/50Hz grounded socket, via the ungrounded cloud/