Everything you need to know about consumer units


Consumer units are central to the electric system of every building, whether commercial or domestic. If your building uses electricity, it will have a consumer unit. And they’re there for a reason; consumer units are crucial to keep you and your home or workplace safe. But what exactly are they? 

In this article, we’ll take you through everything you need to know about consumer units, from what they are to how they work and what they can do for you. 


What is a consumer unit?

You probably know exactly where your consumer unit is and what it looks like, without even knowing it. You may know it as your switchboard or fuse box. 

Basically, a consumer unit is the point where all the energy coming into the building passes through before it goes out into the building to power your lights, electrical appliances and power sockets. 

A consumer unit allows you to take control of your supply of electricity and distribute it around the building in a safe and controlled way. One of its main purposes is to keep you and your building safe by regulating and monitoring your electricity flow and, crucially, stopping any accidents or dangerous incidents from happening. A consumer unit can detect any abnormalities in your electricity and so can prevent electrical dangers such as short-circuiting, sparking, fires and electric shocks. 

Your consumer unit does a lot of heavy lifting in keeping you safe. 


What is a consumer unit made up of? 

There are three main components in a consumer unit; the main switch to control the flow of electricity to the entire building, then Residual Current Devices (RCDs) and circuit breakers to control the flow of electricity in specific areas of the building such as particular rooms of the house of even specific appliances. 


The main switch

The main switch is, as the name suggests, the main switch to the whole power supply to a building. It controls the flow of electricity to the whole building. Very simply put, when the main switch is on there will be power in the building, and when it’s off there won’t be. 

Whilst RCDs and circuit breakers can flick on and off automatically, the main switch can only be turned on and off manually. It’s rare that you would ever need to turn it off, but there are some occasions where it might be useful or even necessary to cut the power supply to a building off. You might want to turn off the main switch if you were leaving a building empty for a long period of time and didn’t want to use any power. The most common reason for turning the main switch off is during repairs or renovations which affect a building’s electrics. You don’t want to be messing with the electrics when the power is on! 


Residual Current Devices (RCDs)

Residual Current Devices or RCDs are some of the smaller switches you will find inside your consumer unit.

The power supply in any building is split into several different circuits. Each circuit in a building will supply electricity to different areas or rooms, and will power different electrical appliances and power sockets. RCDs control these circuits. They also constantly monitor the levels of power going through the circuits, making sure they don’t go over safe levels. These levels are normally set at 80 amps, which makes sure they don’t go high enough to cause serious danger or injury to humans. 

When an RCD detects an incorrect level of power going through a particular circuit, they automatically switch off and stop the electric current in its tracks. This is called tripping. It can happen either when the levels get too high, or if it senses an abnormality or fault. This is particularly good news as it means an RCD would automatically shut off the power supply if, for example, someone touched a live wire. 


Circuit breakers 

Circuit breakers are similar to RCDs in that they also control and monitor the flow of electricity through specific circuits. 


Bus bar

The bus bar is a long piece of copper with long teeth on it, which hold the main switch, RCD and circuit breaker switches in place. The bus bar is normally covered up by a casing so you may never see it unless an electrician comes to do work on your consumer unit, but it does the very important job of keeping everything in place. 


How do you use a consumer unit? 

Your consumer unit does most of the work without any input from you at all, but there are a few occasions when you will need to use your unit manually. The most common times when you might need to get involved are when a switch trips and you need to turn a circuit back on again. You might also need to turn your unit off with the main switch if there are repairs or electrical works to be done. 


Main Switch 

As we know, the main switch is used to cut off the power supply to your building when you need it off, usually for safety reasons when someone needs to get into your electrics system, or potentially if a building is being left empty for a long time. 

The main switch couldn’t be simpler to operate. It’s the biggest switch in a consumer unit, usually separate from all the others, and should be left on almost all the time. To turn it off, you simply flick the switch, and vice versa. 


Circuit breakers and RCDs

These are laid out in rows of switches. Often they will be labelled with which areas they control the power supply to. If they aren’t already labelled, it’s a good idea to label them as it makes it much easier to keep on top of what’s going on with your electricity. You can work out which switch controls which rooms/appliances by turning them off and back on one at a time. 

When a switch trips it will automatically jump to the off position. To reset and turn the power to that circuit back on, all you need to do is turn the switch back on. 

Circuit breaker and RCD switches work in just the same way as the main switch; you simply flick them on and off like a normal light switch. 


When should you repair or replace your consumer unit?

Whilst consumer units are pretty tough and durable, like anything else they go through some wear and tear and so they do need a bit of maintenance to keep them in top condition. 

There are a few easy things to keep an eye out for which can let you know if your consumer unit needs a bit of TLC.


Very frequent tripping 

Occasional tripping is normal and all part of the effective working of your consumer unit, but if tripping starts to occur more frequently, especially the same circuit or circuits over and over again, it may be a sign that something’s wrong and it might be time to get an electrician round to have a look. 

Whilst you can just keep flicking the switches back to turn the power back on, this can just make any damage worse if it’s done too regularly. 


Crackling sounds

One of the most potentially dangerous warning signs that your consumer unit is faulty is hearing a crackling or buzzing sound coming from the unit itself. The sound could be coming from electricity “arcing” or jumping between connections. Arcing can be extremely dangerous as it can lead to electric shocks varying in strength which could cause burns, nerve damage or collapse. 

If you hear crackling or buzzing coming from your consumer unit don’t touch it, just get a professional to come and investigate. 


Burn marks

If you see any scorch marks on your consumer unit it could mean something is wrong with a connection, which could be dangerous.  


Exposed wiring 

Exposed wiring is a small issue if you catch it quickly, but can lead to more serious problems if left exposed for a while. 


Warped or broken cover 

Similarly to exposed wiring, a warped or broken cover to your consumer unit isn’t a big problem by itself but can be a sign of something else being wrong. If you spot damage to your consumer unit’s cover, it’s a good time to get someone to look at it as you can get ahead of any bigger issues before they materialise. 

Of course, sometimes repairs aren’t enough and you need to replace your consumer unit with a new one. When that time comes you can look online at Electrical Supermarket at all the units we have to offer. 

For more information or advice on consumer units, you can get in touch with our team of experts. We’ll be more than happy to put our experience and expertise to good use and help you out.