A guide to Consumer Units

24th January 2022

A guide to Consumer Units

Consumer units are the heart of the home in terms of electricity, and our guide will tell you all you need to know about installing them.

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A consumer unit is the beating heart behind the home, or in real terms, the big piece of kit that makes all the electrics work. It’s an essential part of a building’s infrastructure, so we look at all you need to know before installing or replacing one. 

What are consumer units?

A consumer unit, or fuse box, is connected to every piece of electrical wiring in a building. It contains things like the mains switch, circuit breakers, RCD testing button and earthing cable. Domestically, people will visit their consumer unit if a fuse blows or there’s a power surge, while on an industrial scale consumer units could be responsible for hundreds of applications. You’re likely to find them in the utilities cupboard, or up on the garage wall. 

How many consumer units can you have?

In some cases, you might need to fit a second consumer unit. This is most common when working on an extension to an existing building, or powering something like a workshop, shed or garage. Consumer units can only provide a certain amount of wattage. By exceeding the safe electrical load capacity, you risk blowing all the fuses and potentially causing serious damage to a property. You’ll also void any insurance claims, never something you want to have to explain to a client. 

If installing a second consumer unit, it’s vital to earth it and get all connections checked before running it. Only when it’s fully approved within regulations can it be activated. 


Do consumer units have to be metal?

Since regulations changed in 2016, all domestic consumer units must be either enclosed in a non-combustible material or housed in a cabinet made from a non-combustible material.  

These rules were put in place to contain any fires that broke out in the consumer unit within their casing, stopping the spread of flames. Consumer units made out of non-combustible metals such as steel would pass these regulations. 

The rules only apply to consumer units positioned within domestic buildings, so anything installed outside wouldn’t be covered. 

Do plastic consumer units have to be replaced?

Old style plastic consumer units no longer meet new regulations, however they don’t need to be replaced. So long as their safety features are up to date (such as old MCBs updated to RCBOs) and they are fully enclosed in a non-combustible casing, they can remain in the property. 

Are plastic consumer units legal?

Yes. You can buy a brand new plastic consumer unit, so long as it’s housed in a non-combustible casing. Any old plastic consumer units are still legal too, they’ll just need new casing to make them meet regulations. 

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