RCD and Circuit Protection

Front

What does an RCD detect?

Back

An RCD detects imbalance in the currents of the supply and neutral conductors of a circuit.

Front

Can an RCD protect against overcurrent or short circuit?

Back

No, an RCD cannot protect against overcurrent (overload) or short circuit like a fuse or a miniature circuit breaker (MCB) does, except for the special case of a short circuit from live to earth.

Front

What is the primary function of an RCD?

Back

The primary function of an RCD is to prevent electric shock by breaking the circuit when it detects an imbalance between the live and neutral currents.

Front

How does an RCD differ from a circuit breaker?

Back

An RCD is designed to detect earth faults and protect against electric shock, while a circuit breaker is designed to protect against overcurrent and short circuits.

Front

Can an RCD provide protection against electrical fires?

Back

Yes, an RCD can help prevent electrical fires by detecting earth faults that could lead to overheating and ignition.

Front

What is the difference between an RCD and an RCCB?

Back

An RCD (Residual Current Device) and an RCCB (Residual Current Circuit Breaker) are essentially the same, both designed to detect earth faults and prevent electric shock. The term RCCB is often used to emphasize the circuit-breaking capability.

Front

How often should RCDs be tested?

Back

RCDs should be tested every three months by pressing the test button to ensure they are functioning correctly. This is to verify that the device can trip and cut off the power supply in case of a fault.

Front

What is the typical tripping current for an RCD?

Back

The typical tripping current for a domestic RCD is 30 milliamperes (mA). This level is considered safe for preventing electric shock while minimizing nuisance tripping.

Front

What is the response time of an RCD?

Back

An RCD typically trips within 30 milliseconds to prevent electric shock, providing rapid disconnection of the electrical supply.

Front

Can an RCD be used in DC circuits?

Back

Standard RCDs are designed for AC circuits. Special types of RCDs, known as DC-sensitive RCDs, are required for DC circuits.