Your fuse box (consumer unit) has two very important parts: RCDs and MCBs. These keep your home safe from electric shocks and fires. Let’s understand what they are, how they work, and why you need them.

What is an RCD?

RCD stands for Residual Current Device. It monitors the flow of electricity and cuts off power instantly if it detects any imbalance—such as electricity leaking through a damaged cable or faulty appliance. This helps protect you from electric shocks and can even save lives.

RCDs are often marked with a 'T' or 'Test' button. Pressing this button allows you to check if the device is working correctly. If it doesn’t trip, call an electrician.

What is an MCB?

MCB stands for Miniature Circuit Breaker. It protects your home’s wiring from overheating by turning off the power when there’s too much current. This might happen due to a short circuit or too many devices on one socket.

Each MCB is connected to a specific part of your home: for example, one for the kitchen, another for upstairs lights, and so on.

Differences Between RCDs and MCBs

• RCD: Protects people from electric shocks
• MCB: Protects wiring and appliances from overcurrent

Why Are They Important?

• Reduce fire risks: Faulty circuits can overheat, but MCBs prevent that.
• Prevent electric shocks: RCDs cut off the power if something goes wrong.
• Protect appliances: Avoid damage from overloads or faults.

How to Stay Safe

• Test your RCDs every 3 months using the test button.
• Don’t ignore frequent tripping. It means there’s a problem that needs checking.
• Never replace an MCB or RCD yourself. Always hire a professional.

Are They Required in the UK?

Yes. Modern UK wiring regulations (18th Edition) require RCD protection on most circuits. This is especially important in wet areas like bathrooms or kitchens.

Final Thought:

RCDs and MCBs are small but powerful safety devices that protect your home. If you’re unsure about your current setup, have a registered electrician inspect your consumer unit.