Hello and welcome to Just Answer. My name is ***** ***** I will be happy to assist you with your electrical question.
1) I suggest to temporarily "roll" ,,,,ie,,,,,,,,move the circuit onto another RCD of the same amperage and see if the tripping follows onto another known working RCD breaker or if the trouble goes away.
2) If the trouble goes away after a 24 hour time period, then the original RCD is faulty and needs to be replaced. If the trouble follows onto another known working RCD of the same amperage, then either a problem within the circuit wiring or a problem with the connected loads and the loads and/or wiring needs to be isolated to determine the actual cause.
3) Another option to confirm if a faulty RCD is to install a replacement RCD for the circuit. Then leave the original RCD installed but disconnect the circuit conductors. See if the problem RCD still trips under a "no load" connection (load side wires are disconnected from RCD) for a 24 hour time period. If still tripping, then replace the RCD. If no tripping, then the problem needs to be isolated.
4) Leakage current within any of the connected loads as well as a loose wire inside the wall boxes can also cause the RCD to trip.
Hope this helps………If you have any additional questions, let me know and I’ll be glad to answer them for you.
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The next time you have an electrical question, you can also request for me at: http://www.justanswer.com/home-improvement/expert-your-electrician ……….Thanks…………..Kevin!