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Yes, it is necessary, there are regulations.
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This is not clear, but I personally think it should be.
Building Electrical Design and Construction Manual
Generally, it is meters, and the national standard "Equipotential Bonding Installation" (02D501-2). >>>More
The grounding wire of the building itself is the ground wire of the iron wire box of the bathroom, which is connected with the ground wire of the distribution box.
Its main purpose is to prevent electric shock, so that the possible conductive parts of the toilet are connected to the earth, and the voltage is 0.
I can tell you responsibly that it doesn't have to be because they don't have a strong sense of security. Equipotential bonding of metal objects in the bathroom will reduce the possibility of electric shock. There is some truth to his design.