RCDs are designed for protection from electrocution or electrical fires. They do this by automatically cutting off the supply of electricity whenever an electric current leakage is sensed. The RCDs allow for continuous monitoring of the current level passing through a wire in one single direction, and again in the reverse direction. The circuit will be automatically broken in the event that there is a difference of 300mA or less in some instances. This provides the assurance of protection against electrical shocks.
You should be aware that RCDs will not react to overloads or short circuits. They will have a standard rating that may be anywhere from 32A to 64A. However, this rating corresponds with the internal contact and switching mechanism. The device will not trip out when the standard rating is exceeded. You will also see an indication of the imbalance that will need to occur for the device to trip.
All RCDs come complete with a test button, allowing for the simulation of an event involving disparity in the electricity supply. If the device doesn’t trip during such a simulation, then it will have to be replaced.
There are some key differences between RCDs and RCBOs. The RCBOs are integrated with an electronic switch and designed for the transfer and breakage of currents under normal service conditions for the opening of contacts when the residual current is of a certain level under defined conditions. These devices are also designed for protection against overloading and short-circuiting.
The RCBO will break the circuit if the current demand exceeds a particular level. An overload may be sensed in the event of a short circuit, or excessive demand due to the connection of multiple devices. This will automatically cause the circuit to break. There would be a considerable risk of the wires melting and catching fire if the circuit wasn’t broken. The RCBO thereby provides protection for people, equipment, and property.