What is an RCBO?

• A. residual current device
• B. residual current device with overcurrent protection
• C. residual current breaker only
• D. residual current device with surge protection

Answer: (B)

An RCBO combines residual current protection with overcurrent protection in one unit. It constantly monitors the current flowing in the live and neutral conductors and will trip if it detects a leakage current to earth, protecting against electric shock. It also acts as a circuit breaker for overcurrent events, such as overloads or short circuits, disconnecting the circuit when the current exceeds its rated value. This dual protection makes it safer and more convenient than using a separate RCD plus a separate overcurrent device.

The other options aren’t the same: a device that only detects residual current (an RCD) doesn’t provide overcurrent protection, a “residual current breaker only” phrasing still describes leakage protection without overload protection, and a device with surge protection handles voltage transients rather than overcurrent or earth leakage.