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PostPosted: Thu Dec 07, 2017 3:33 am 
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So I've finished a move to Japan for a job as a translator here and I was lent a house to live in by my company. I know from my past experience as an exchange student in Japan that three-prong wall outlets are not standard and may only appear in rooms that has water pipes, like the kitchen, bathroom and toilet.
In my new house however all wall outlets are two-pronged, even in the bathroom. A very few number of wall outlets in the kitchen and bathroom (but not the toilet) has special earth outlets (bellow the normal two-pronged outlets) for connecting things like refrigerators and washing machines, but neither the washing machine nor the refrigerator are using it! The washing machine do have a green & yellow earth cable but it's just tucked in behind the washing machine on the floor and it doesn't even have cable shoe terminal in the end.

While the refrigerator doesn't seem to be grounded it is connected through a device with a big red lamp that says 警報停止 (which means "alarm stop" or something like that). I guess it could be some kind of ground fault circuit interrupter or something but I have no idea really.

The floor in the house is wooden in all rooms except the bedrooms that are covered in broadloom rugs and the bathroom and toilet that are covered in plastic mats. It's not a Japanese style house, although some things like the bathroom is quite typical Japanese with separate bathtub and shower area.

I'm a little worried that this could be dangerous, especially that the washing machine isn't grounded, it does have a plastic chassis though. Another problem is the fact that my Swedish laptop I bring with me to Japan uses a grounded plug which can't be connected to a non-grounded travel-adapter. I do have a grounded travel adapter as well but it use the three-pronged type of connector that this house totally lacks. The laptop has a plastic cover so I guess it's quite safe to use ungrounded but I'd better be safe than sorry.

Anyone that know about this kind of stuff? Any good advice is appreciated!


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PostPosted: Thu Dec 07, 2017 3:57 am 
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Can't you just connect the fridge and washing machine to the ground outlet? I would say it's probably a very good idea to do this, and I can't think of any disadvantage.

For your laptop you don't need to connect the ground plug. Some laptops have them by default on their PSUs, but I've never heard of any that needed them. My own laptop came with two separate cables for plugging into the PSU, one with the ground leg and one without. I don't know why I'd use the one with it.


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PostPosted: Thu Dec 07, 2017 4:22 am 
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For the refrigerator I can't because there is no earth cable from what I can see. For the washing machine I'll probably need a new cable shoe as it's just a loose fringe harness of copper threads. Unless you can just screw it in under the screw thingy that covers the earth outlet or something. I'll have to look into that.

For the laptop I guess it might be safe without the earth lead (Japanese laptops has a separate earth cable that comes from the PSU and they usually just leave it hanging in the air since there's most often nowhere to connect it too) but since it has a three-pronged cable going in to the PSU I'm not 100% sure. Also the only way for me to connect it is to use a modified (by cutting plastic tabs inside it) travel adapter that allows my grounded plug (type F) and converts it to a two-pronged USA/Japanese plug.


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PostPosted: Thu Dec 07, 2017 4:33 am 
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It's very rare for a laptop to need the ground even though they always make it a possibility. I'm pretty sure you are fine. :)
If there IS an issue (due to improper design of the laptop), you should feel a slight buzz when touching certain surfaces on the laptop while it's been turned on for a while. If you don't, I can't imagine you need to worry about it.

Pokun wrote:
For the refrigerator I can't because there is no earth cable from what I can see.

Isn't there a screw terminal on the back of it? (probably with this icon) You could just find som isolated copper wire and screw it on there. That's what I did with my New Astro City cabinet, which is coincidentally Japanese hardware, so I imagine it's the standard there. If there isn't one, then it's not needed for the refridgerator.

Quote:
For the washing machine I'll probably need a new cable shoe as it's just a loose fringe harness of copper threads. Unless you can just screw it in under the screw thingy that covers the earth outlet or something.

You can just do that, and you're probably expected to do it like that. I would make sure the power is off before doing it though :P
In fact, you might even want to discharge it into the ground plug before touching the uninsulated part, just to be sure! I wouldn't be surprised if this kind of thing builds up a lot of static.


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PostPosted: Thu Dec 07, 2017 8:02 am 
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For both of them, you need to put the stranded copper cable under the screw. This is how appliances work in Japan. The cable is either green or yellow/green.

I just took a picture of our washing machine and once done it would look like this:

Attachment:
WashingMachineGround.png
WashingMachineGround.png [ 159.29 KiB | Viewed 419 times ]


If there is none for the fridge near the outlet it would be not normal. In that case I would ask the landlord about it.


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PostPosted: Thu Dec 07, 2017 4:09 pm 
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Thank you both for all advices.

I took a closer look and it's a screw with a plastic head that says アース (earth) in front of a metal plate. So it's just a matter of screwing the metal plate on the fringe. No need for a cable shoe.

The refrigerator though really doesn't have an earth cable. It does have two really short green & yellow cables connecting something on the backside of it to the chassis but there are none going out of it that can be used to connect to the earth outlet. OK I will ask my landlord about it.


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earth.jpg
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PostPosted: Fri Dec 08, 2017 3:15 am 
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When I asked they said that washing machines should be grounded or it could be dangerous (they had no explanation why earth wasn't connected when I moved in though), but they weren't sure about the refrigerator. Not sure what to do about that one. :?

I also noticed that the microwave oven has a green & yellow earth cable hanging loose. There are no earth outlet anywhere near it. I could move it to another spot closer to the fridge so that it can use one of those. But I heard it can be dangerous to have grounded and ungrounded devices near each other if you touch them both and your body becomes the bridge to the ground for the ungrounded one.


Another thing I wonder about, desktop computers often have a metal chassis and high power, should they be grounded in a house like this? I didn't bring my desktop computer to Japan but it may be good to know.


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PostPosted: Fri Dec 08, 2017 3:34 am 
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Quote:
But I heard it can be dangerous to have grounded and ungrounded devices near each other if you touch them both and your body becomes the bridge to the ground for the ungrounded one.

Yes, if the chassi of the ungrounded device is/gets electric, then this is dangerous. Avoid! Just to be sure/safe.

I've felt the current in the casing of a number of devices - fridges, metallic lampshades, computers (including both desktops and laptops). It is generally more perceptible if you stroke the surface slowly - Then you might feel a stronger 50/60hz buzz/tingle. (warning: this method is however of course not a guaranteed way to rule out if a chassi is electrified or not, and i've found that people are differently susceptible to this sensation).

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PostPosted: Fri Dec 08, 2017 3:46 am 
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Old AT computers lead the full voltage to the power button, with those it was crucial you used a grounded outlet. Modern ATX and so on ones only lead 3-5V to the power button, so the risk of any significant voltage going to the chassis is low. Not having grounding would mainly cause hum if you connect a mic.


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PostPosted: Sat Dec 09, 2017 4:12 pm 
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I see so computers are generally quite safe.

FrankenGraphics wrote:
Quote:
But I heard it can be dangerous to have grounded and ungrounded devices near each other if you touch them both and your body becomes the bridge to the ground for the ungrounded one.

Yes, if the chassi of the ungrounded device is/gets electric, then this is dangerous. Avoid! Just to be sure/safe.
OK this is problem then. I guess I'd just have to put the microwave in a place where it's not close to grounded devices, radiator or water pipes. In Sweden, houses built after 2000 (I think) have earth tabs in all wall outlets regardless if they are near water or not to avoid this potential problem (although that makes some certain older TVs and other devices not to be connectible in new houses). But I don't see that happening in Japan any time soon, and grounded devices are always possible to connect without the earth. This house is probably built in the 80s anyway.

I might look into getting some ground fault circuit interrupters for use with high power devices as well.


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