Which devices are commonly housed in a consumer unit to protect circuits?

• A. MCBs
• B. RCDs
• C. RCBOs
• D. MCBs RCDs and RCBOs

Answer: (D)

In a consumer unit, the protection of circuits is provided by devices that interrupt faulty or dangerous conditions. Miniature circuit breakers (MCBs) protect against overloads and short circuits on individual circuits, stopping excessive current from heating wires or causing faults. Residual current devices (RCDs) monitor the balance between live and neutral; if they detect leakage to earth (which could indicate a shock risk), they trip to cut the supply. Some installations use RCBOs, which combine both protections in a single device, giving per-circuit protection against both overload/short circuits and earth leakage.

Because a modern consumer unit may use MCBs, RCDs, or RCBOs depending on the level of protection and wiring, the common arrangement is to have all of these types available in the board. That’s why the best answer is that MCBs, RCDs, and RCBOs can all be housed in a consumer unit to protect circuits.