What is the purpose of an RCBO?

Residual current operated circuit-breakers with integral overcurrent protection for household and similar uses, or RCBOs, are intended to protect people against earth fault current under the protective measure Automatic Disconnection of Supply (ADS) as well as additional protection. RCBOs also provide protection against both short-circuit and overload.

The standard to which RCBOs conform is BS EN 61009-1 and the United Kingdom has a special national condition (SNC) whereby RCBOs providing protection for circuits having neutral conductors reliably at Earth potential are permitted to have an unswitched neutral; that is in the UK where the Earthing System is TN-S or TN-C-S RCBOs are permitted to be single-pole devices.

It is important to select for use the correct type of RCBO for the nature of the installation. There will be instances where single-pole devices will need to be replaced with either single-pole and neutral or double-pole devices.

To find out more about RCBOs and other protective devices go to https://www.youtube.com/watch?v=Hn9Mz7v58pg where Jake Green and Tim Benstead discuss how protective devices have evolved over the years.