- RCBO stands for
Residual Current Breaker with Overload
- In simple terms an RCBO is a combined MCB and RCD.
- By combining the MCB and RCD functions we have the advantage of not only saving space in the consumer unit allowing more circuits to be accommodated if required, but it also allows greater control over individual circuits when a fault occurs.
- To explain this a little further, consider the separate MCB and RCD arrangement shown below. If an overload occurs which would cause an MCB on that circuit to trip, the only circuit affected is the circuit which that MCB is connected to. All pretty straightforward, but if a fault occurs causing the RCD to trip, ALL of the circuits that RCD protects will be impacted.
- By removing the RCD and having the MCBs replaced with RCBOs, this will allow RCD protection for each individual circuit, meaning that if one of the circuits has a fault which trips the RCD, all other circuits can remain functional you wait for the fault to be fixed.
- This is not only a convenience factor, but from a safety perspective it could mean that a fault with a mains socket or appliance does not plunge the house into darkness by the RCD also disabling a lighting circuit. Of course the fault could be due to a fire which has just started, and to have had a lighting circuit disabled as a result of a fault on a separate circuit could spell disaster.
- In conclusion the recommendation that when having a new consumer unit installed, RCBOs should be fitted instead on separate RCDs and MCBs. This is not mandatory, just a recommendation based on the reasons described above.
- Other devices typically found in a domestic consumer unit include MCBs and RCDs.
