Understanding Your Consumer Unit: A Homeowner's Guide

Your consumer unit (often called a fuse box) is the heart of your home's electrical system. Understanding how it works can help you stay safe and know when to call a professional.

What is a Consumer Unit?

A consumer unit is the central point where your home's electrical supply is distributed to different circuits. It contains protective devices that automatically disconnect the power if there's a fault, preventing electric shocks and fires.

Key Components

Main Switch

The main switch controls power to your entire property. Turn this off before doing any electrical work or in an emergency. It's usually rated at 80A or 100A for domestic properties.

Circuit Breakers (MCBs)

Miniature Circuit Breakers protect individual circuits from overload. If too much current flows through a circuit, the MCB "trips" and cuts the power. Common ratings include:

• 6A - Lighting circuits
• 16A - Immersion heaters
• 32A - Ring main circuits (sockets)
• 40A - Cookers
• 45A - Showers

RCDs (Residual Current Devices)

RCDs provide life-saving protection against electric shock. They detect tiny imbalances in electrical current and disconnect the power in milliseconds. Modern consumer units have RCD protection on all circuits.

RCBOs

RCBOs combine the functions of MCBs and RCDs in a single device, providing both overload and shock protection. They're increasingly common in modern installations.

Modern vs Old Consumer Units

Old Fuse Boxes

If your property still has an old fuse box with rewirable fuses, it should be upgraded. These offer minimal protection and don't meet current safety standards.

Modern Consumer Units

Modern units feature:

• RCD protection on all circuits
• Circuit breakers instead of fuses
• Metal enclosures (fire-resistant)
• Surge protection (optional)
• Clear labelling of circuits

When to Upgrade Your Consumer Unit

Consider upgrading if:

• You have an old fuse box with rewirable fuses
• There's no RCD protection
• The unit is damaged or corroded
• You're adding new circuits
• You're having major electrical work done
• An EICR recommends it

Common Problems

Tripping RCDs

If your RCD keeps tripping, there's a fault somewhere. Common causes include faulty appliances, damaged cables, or moisture in outdoor sockets.

Tripping MCBs

Individual circuit breakers trip when there's an overload or short circuit. If it happens repeatedly, call an electrician to investigate.

Safety Tips

• Never attempt to work inside your consumer unit
• Test your RCDs quarterly using the test button
• Label all circuits clearly
• Keep the area around your consumer unit clear
• Call a qualified electrician for any repairs