I entered into a 32-years-old apartment. I checked all sockets with a super-tester. All of them are OK, except two sockets in a single room, where the super-tester shows "no grounding".

I talked with an electrician and he said that it might be related to the "control box" of the room, which is hidden somewhere behind one of the wall. EDIT: This is NOT the fuse-box of the entire apartment, which is visible just outside the door of the apartment. It is a control box for this specific room - a box that collects the wires from the general fuse-box and distributes them to the electricity points inside the room (two sockets and one light-bulb).

To detect this mysterious "control box", I used a radiation-tester. The radiation-tester shows electric radiation of several hundreds V/m near the socket, but, it shows no radiation in a circle of radius 1 meter around the socket, so I do not know how to find the control box.

My questions are:

  • How can I find the control box of the room?
  • Is this control box really the reason for the lack of grounding in the room? Or is there a different solution?
  • 1
    You could try attaching a load to the socket so that some current is being drawn through the wires in the wall. This may allow the tester to detect the wires better. (Note that I have no way to know how this "radiation tester" actually works but loading the circuit is still worth a try). – Michael Karas Sep 29 '16 at 11:04
  • Hi Erel, We need to know what country you are in to get a better idea of your wiring setup. No ground implies that the earth ground conductor is either not present or has become disconnected. I'm from the US but the term control box sounds like it could be the panel box, where the circuit breakers or fuses are located. I would first talk with the landlord and find the location of the control box so you can safely check the wiring with power turned off. Depending on building codes or age, it could be located in the apartment close to the entrance or remotely in the basement or utility closet. – Mister Tea Sep 29 '16 at 12:34
  • @MichaelKaras I did this. I plugged in a battery charger. The radiation tester indeed showed larger radiation, but I still could not follow it along the wall. – Erel Segal-Halevi Sep 29 '16 at 17:56
  • @MisterTea I live in Israel, and all buildings built in the last 40 years must have grounding by law. This apartment also has grounding in most of the rooms - there is only one room where the two sockets have no grounding. The fuse-box of the entire apartment is visible just outside the main door, but, the electrician claims that there is a smaller control-box for each room, which is hidden behind the wall of that room. I did not know about such control boxes before. – Erel Segal-Halevi Sep 29 '16 at 18:02
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    @ErelSegal-Halevi In the USA and I'd imagine other places, electrical boxes of any type must always be accessible. Perhaps the practice of placing junction or control boxes in each room was/is an Israeli code or electrician practice. If the build is new enough to have mandatory grounding, then you have a broken ground connection somewhere. Given that the outlets will see more mechanical stress, I would start there, pull them out and check their grounding conductors. They could have come loose. Make sure to kill the power at the fuse-box first! – Mister Tea Sep 29 '16 at 19:18

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