I am installing a small electrical board for a home renovation. There is a single RCD 30mA, EU standards (I am in France). There are ~20 circuits, each with their own differential, most are OFF, I am only using the lights and some power points.
One circuit is posing a problem since yesterday when I was pulling another cable through the box, it is causing the RCD to trip ever since.
The problem is strange, only the +ve cable of this circuit trips the RCD (neutral does not even need to be connected). If I connect the live cable to live terminal of another differential, or directly to RCD I have the same problem (CONCLUSION 1 : the circuit's differential is not faulty)
The RCD does not trip the other circuits (CONCLUSION 2 : the RCD is not faulty)
If I take (only) the live cable from the circuit and connect it to the neutral terminal of a differential, or RCD the RCD does not trip. (CONCLUSION 3: something strange is happening, why does earth fault only trip RCD live ?)
This circuit has several power points connected in parallel with some solder points along the way. The solder points are wrapped in tape and embedded in a stone wall. While the concrete was drying the circuit used to trip, but I let it dry for a few days and no problems since, until yesterday. I cut the cable close to the entry of the wall to check whether the fault was in the wall, or between the wall and circuit board. There is definitely bad insulation inside the wall connection. But it is hard to access and I would at least like a temporary fix that does not require breaking into the wall.
Is there any.
- Why does the RCD trip when the earth fault is connected to RCD live, and not RCD neutral?
- Why was this not a problem until yesterday?