A tripped circuit breaker or RCD is your fuse board's protective mechanism responding to a detected fault or overload condition on that circuit. When a miniature circuit breaker (MCB) trips, it has sensed a current above its design threshold — either a short circuit or an overload from too many appliances drawing power simultaneously.
When the residual current device (RCD) trips, it has detected an imbalance between the live and neutral currents, indicating that current is escaping through an unintended path — possibly through a damaged cable, a faulty appliance, or a connection fault to earth. A single trip that resets and holds is often caused by a momentary overload.
Repeated tripping, or a breaker that will not hold when reset, points to an ongoing fault that needs to be traced and cleared before the circuit can be safely restored. Before contacting an electrician, note which breaker has tripped, what was in use on that circuit when the trip occurred, and whether the breaker holds for any length of time after reset.
Do not continue to force a breaker back on if it keeps tripping. An electrician will carry out a visual check of the consumer unit and the affected circuit, use insulation resistance and continuity test equipment to locate the fault, and advise on repairs before restoring the circuit.
If the consumer unit itself shows damage or is found to be out of date, they will advise on whether the board requires replacement.