An RCD is a Residual Current Device, that will save your life in an event of a fault. It detects fault currents that MCB’s and fuses will not detect. For example if you for whatever reason come into contact with a live cable an RCD will trip in less than 40 milliseconds.
I advise, if you don’t have one you should strongly consider having one installed and upgrade your current system. In fact, for any electrical additions or alterations to meet latest regulationd an RCD will be required.
