An RCD is a safety device designed to quickly disconnect electrical circuits when it detects an imbalance in the flow of electric current caused by a fault (such as leakage to earth). This helps prevent electric shocks and reduce the risk of electrical fires.

RCDs are commonly used in consumer units (fuse boxes) and electrical outlets in the UK. They are installed to protect circuits supplying sockets, outdoor power points, bathroom circuits, and other areas where there is a higher risk of electrical shock.

RCDs provide additional protection beyond that offered by circuit breakers (MCBs). They can detect small leakage currents (typically 30mA or less) that MCBs may not respond to, thereby offering enhanced safety against electric shock.

Yes, RCD protection is mandatory in certain circuits and situations according to UK electrical regulations (BS 7671). For example:

• Circuits supplying socket outlets up to 32A in domestic premises.
• Circuits supplying socket outlets up to 20A in non-domestic premises.
• Circuits supplying mobile equipment for outdoor use (e.g., portable tools).

If an RCD trips frequently, it could indicate a fault in the circuit or a problem with connected appliances. Consulting with a qualified electrician is crucial to identify and rectify the underlying issue to maintain electrical safety.