When might an RCBO be preferred over a standard MCB?

• A. It provides higher current rating than MCBs in all situations.
• B. It combines residual current protection with overcurrent protection to reduce shock risk.
• C. It is cheaper and easier to install than MCBs.
• D. It protects only against short circuits.

Answer: (B)

An RCBO combines two protective actions in one device: it trips on overcurrent just like a standard MCB, and it also trips if there’s earth leakage that could cause a shock. This means it can both stop a short circuit or overload and cut off supply if current leaks to earth, reducing the risk of electric shock and fire. Because of this dual role, an RCBO is preferred in circuits where leakage might occur or when you want both protections in a single unit.

The idea that it always provides a higher rating isn’t correct, and RCBOs aren’t inherently cheaper or easier to install than MCBs. Also, an RCBO doesn’t protect only against short circuits; its residual-current protection addresses earth leakage as well.