Throughout the course of our job, we address numerous fuse box and circuit board tripping issues. One of the commonest faults or problems would be a tripping "residual current device". A residual current device is also known as an RCD, RCCB, or occasionally an RCBO (an RCD combined with a miniature circuit breaker).
When an RCD trips, it is generally because the device has detected a fault in your wiring system that has resulted in a current imbalance between the live and neutral conductors. This is an essential safety device that detects that some current is now flowing to earth, thus causing the RCD to trip incredibly fast. If resetting the device causes the RCD to trip again, the stray current needs to be investigated and the problem resolved before the circuit can be re-energised. If the RCD trips intermittently, this could be due to poor circuit design, where the combined use of appliances, computer equipment, etc. exceeds the acceptable standards.
Quite often, the device does not trip at all, even when the small test button is pressed (it is recommended that the test button be pressed every six months to ensure mechanical operation). A faulty residual current device or one that doesn't trip when tested definitely requires further investigation. Looking deeper into the problem, one could find that the RCD has been operated frequently past its rated current (again through poor circuit design).