An rcd trips because you have a current leaking to earth which is greater than 30ma. Computers , ovens, and fridges generally leak a small amount of current to earth.
Solution. Unplug all appliances or isolate if they have double pole switching (oven, shower). If rcd still trips then it is likely the fault is to be found in the ring final circuit and not an appliance. If this is the case you will need to turn off the circuit and inspect it. Look behind each socket for loose wires. The cause in either L or N leaking to earth. For instance I came across this the other day. What I found was the installer had not used rubber grommets to pass the cable through the back boxes. Inside 1 of the boxes the insulation on a N wire had made contact with the the back box. As the back box is earthed this current leakage caused the RCD to trip and imposssible to reset. A simple insulation test by a sparkiy will confirm this. Other causes...a L or N wire has become detached inside a socket box and is touching the metal of a box thus causing a leak to earth, perhaps an immersion element or washing machinne element.
petef, June 2010
