Updated July 2023

I bet you’ve heard the term – a consumer unit – multiple times. But what is actually? How does it look? What’s inside, how to look after it, and what to do in an emergency.

As electricians, we must educate our customers about the various components of their electrical systems. The consumer unit, also known as a fuse box or distribution board, is the central point of control for the electrical system in a home. It is responsible for protecting the house and its inhabitants from electrical hazards by controlling the flow of electricity and tripping the circuit when an overload or fault is detected.

Consumer Unit
Consumer Unit

In this blog, we will look in-depth at the consumer unit, its components, and why you need to understand them.

The main components of a consumer unit are:

Consumer unit components

Main switch

The main switch is the primary point of control for the consumer unit. It is used to turn off the power to the entire house in an emergency. When the main switch is turned off, it will stop the flow of electricity to all the electrical circuits in the home.

Close-up of the main switch
Close-up of the main switch

RCD (Residual Current Device)

An RCD is a device that monitors the electrical current flowing in a circuit and will trip the circuit if it detects an imbalance, which indicates a fault in the circuit. This helps to protect against electric shock and electrocution. RCDs are an essential component of the consumer unit and are required by law in many countries to ensure the electrical system's safety.

Close-up of the RCD
Close-up of the RCD

MCB (Miniature Circuit Breaker)

MCBs protect individual circuits from overloading or short-circuiting by tripping the circuit when an overload is detected. They are typically found in mini-switches and control the flow of electricity to different areas of the house, such as the kitchen, living room, and bedrooms. 

Close-up of the MCB
Close-up of the MCB

RCBO (Residual Current Breaker with Overcurrent Protection)

It is a unique device that, in one body, combines the functions of both RCD and MCB, protecting against both overload and earth leakage. Test the RCBOs within your consumer unit every 6 months to ensure they work and protect you.

Close-up of RCBO
Close-up of RCBO

SPD (Surge Protection Device)

This device protects against surges into the electrical installation from outside the property. Usually caused by lightning strikes. But it can be caused by power surges from elsewhere as well. Such strikers or surges into your domestic fuse board can devastate your electronic devices at your home. 

Close-up of SPD
Close-up of SPD

AFDD (Arc Fault Detection Device)

AFDD protects you from the fire caused by an arc fault. If the current is high enough, electrical currents jump the gap between two conductive materials, then we talk about arc faults. AFDDs will likely become mandatory to protect against fires caused by faulty domestic wiring.  

Close-up of AFDD

Different types of consumer units

The latest 18th Edition Wiring Regulations require all new electrical installations and designs to have metal-clad consumer units or casing to prevent fire risk. It’s due to connections overheating and containing the fire within the metal-clad consumer unit or cabinet.

Older generations of consumer units are plastic and are still commonly found in homes across the UK. However, plastic ones are considered less safe compared to new-generation metal-clad units. That is why we recommend an inspection by a qualified electrician to ensure that the consumer unit is secure and does not pose a fire risk. 

Main types of consumer units

There are many different types of consumer units, but we recommend different ones depending on the situation.

Dual RCD Consumer Unit

A Dual RCD Consumer Unit is an electrical safety device that provides additional protection to the electrical system of a building. It is called a "dual" RCD consumer unit because it contains two residual current devices (RCDs) designed to detect and disconnect the electrical supply in case of a fault, such as an overload or a short circuit. The dual RCD design provides an extra layer of safety for the electrical system, allowing for separate protection for different building areas. This type of consumer unit is commonly used in homes and other buildings in the UK, and it is a requirement for new installations to meet the latest electrical safety standards.

High Integrity Consumer Unit

A High Integrity Consumer Unit, also known as a HICU, is a type of electrical safety device that provides the highest level of protection to the electrical system of a building. Unlike a standard consumer unit, a HICU is designed to withstand and contain any electrical faults that may occur, such as an overload or short circuit. This helps to prevent electrical fires and other dangerous situations.

RCBO

An RCBO (Residual Current Breaker with Overload protection) Consumer Unit is an electrical safety device that combines two essential functions in one unit - residual current protection and overload protection. This consumer unit provides more protection for a building's electrical system than a standard one.

The residual current function detects electrical faults, such as a short circuit, and quickly disconnects the electrical supply to prevent damage or fire. The overload protection function protects against overloading, which occurs when too much current flows through the system.

RCBO Consumer Units are becoming increasingly popular in the UK and are used in homes and commercial buildings. They are a requirement for new installations and upgrades to meet the latest electrical safety standards, ensuring a safer and more reliable electrical system for the building.

What we, as electricians, would recommend

As professional electricians, we suggest using a complete RCBO consumer unit instead of a dual RCD consumer unit. It is because when you have RCBOs, you only lose power to the circuit when there is a problem. From the customers' perspective, RCBOs offer a better solution.  If there is a fault in an electrical installation, the loss of power will be restricted to the faulty circuit only, as opposed to dual RCD-protected circuits, where you can lose power in half of the courses.

Why is it important to do regular maintenance?

You must understand the importance of regular inspection, testing and maintenance of your consumer unit and its components. This will ensure that your electrical system is functioning safely and as intended. In the event of an emergency or a power outage, it's also essential for you to know how to locate and turn off the main switch in your consumer unit.

In conclusion, the consumer unit is crucial to any home's electrical system. It plays a vital role in protecting the home and its inhabitants from electrical hazards by controlling the flow of electricity and tripping the circuit when an overload or fault is detected. As electricians, it's important for us to educate our customers about the consumer unit and its components to ensure the safety and reliability of your electrical system. Regular inspection, testing and maintenance of the consumer unit and its components will also help ensure that the electrical system functions safely and as intended.