An RCBO is a residual current circuit breaker with over-current protection and monitors electrical circuits to keep them running safely disconnecting the circuit if it's unbalanced. These devices are commonly used where there is a need to combine protection against overload, short-circuit and earth leakage currents.

What is the difference between RCD and RCBO?

RCDs can protect against electric shocks, residual currents and earth faults. On the other hand, RCBOs can do what RCDs can do and protect a circuit from short circuits and overload.

RCBO stands for 'Residual Current Breaker with Over-Current'. As the name suggests it protects against two types of faults and in essence combines the functionality of an MCB and RCD.

Residual current or earth leakage- occurs when there is an accidental break in a circuit through poor electrical wiring or DIY accidents such as drilling through a cable when mounting a picture hook or cutting through a cable with the lawnmower. In this instance, the electricity must go somewhere and choosing the easiest route travels through the lawnmower or drill to the person causing electric shock.

Over-current takes two forms;

Overload- occurs when too many devices are in use on the circuit, drawing an amount of power that exceeds the capacity of the cable.

Short-circuit- occurs when there is a direct connection between the live and neutral conductors. Without the resistance provided by the normal circuit integrity, electrical current rushes around the circuit in a loop and multiplies the amperage by many thousand times in just milliseconds and is considerably more dangerous than overload.

Whereas an RCD is designed solely to protect against earth leakage and an MCB protects only against over-current, an RCBO protects against both types of faults.