I live in Spain so this is a radial circuit. I have had a problem for some time with random RCD trips, so I bought an auto resettable RCD. On installing it, I set it to on and it immediately tripped I found that if I set any of my MCB’s to off I could set it to on and it would stay up. Thinking I had a cumulative earth leakage and the new RCD was more sensitive than the old one I was replacing I tested the current flowing through the earth wire at the consumer unit, this was less than 0.5 mA. The earth comes into the house and is connected to two earth wires in the house, one goes upstairs the other feeds the rest of the house. I found if I disconnected the upstairs earth wire I could get all the circuits powered up and the RCD would stay up. After a bit of fault finding I traced the earth issue to the upstairs office. The odd thing was if I plugged my UPS in and connected anything to it, it would trip the RCD the computer did not even have to be switched on! Plugging everything into the wall socket allowed the RCD to stay armed, so I suspected something wrong with my UPS. Sadly after about four hours it tripped again. Pulled the plug out of the wall in the office and then the RCD rearmed, this lasted till next morning then tripped again. In desperation I totally disconnected the earth from the house, my theory being that if it tripped now it can’t be an earth leakage fault. It lasted about ten hours then tripped again! I have now reconnected the original RCD at least that trips every two or three weeks not every day. What possibly can be the problem! Are there any electricians out there that can offer a explanation as to what is going on.