This is a question about electrical safety in Japan. I know this isn’t a Japanese forum, but my Japanese isn’t up to much, and everyone I can ask either knows nothing about electrical safety or nothing about Japan.
I come from the UK, where every plug is three-pronged and ordinary consumers like me don’t have to think about matters like grounding.
Here in Japan, most plugs are two-pronged. Risky devices like washing machines and dishwashers come with an extra green and yellow ground wire bolted onto the back. In my 80s apartment there are a couple of power sockets with a little metal plate where I can attach a ground wire; one is in the place where you’d expect a refrigerator to go, and the other is for the washing machine. It seems that the builders didn’t anticipate other kinds of home appliance.
So now I have a dishwasher, and it’s nowhere near any of the grounding plates. But it is near the kitchen range, and the kitchen range has a couple of gas taps attached. I am vaguely aware that gas pipes should be grounded, so I considered connecting the ground wire to the sink, but on closer inspection, it appears that the gas taps and the sink do not make electrical contact — a 1 inch ring of uPVC separates the two.
The pipe work is safely sealed away from incompetent amateurs like me, so I can’t start hunting for evidence of grounding work there. However, the kitchen range does appear to have electrical contact (through metal pipes) to a gas water heater just above the kitchen range. The gas water heater is, in turn, connected to one of the gas taps via what appears to be a rubber hose. I don’t see any other signs of grounding, and the water heater was professionally installed so, at first glance, this suggests that the kitchen range is grounded.
So, what should I do? Shall I just connect the dishwasher to the sink, or am I going to have to bite the bullet and run a long wire to the refrigerator’s ground plate?
Many thanks for taking the time to read this.
Best Answer
You can't rely on the integrity of the ground/earth on the pipework of the sink. For all you know it could be connected to PVC pipework further down. In the U.K all pipework is meant to be cross-bonded which is then taken to the earthing bar. However in Japan I am unsure if this is what is done. Regardless you should be earthing/grounding it back to the incoming supply.
In a lot of countries that use two pronged devices they are actually fed from centre-tapped transformers or are double insulated devices. Either way they should not become dangerously live.
In short don't connect to the sink run it back to the earthing/grounding bar.