The Consumer Unit or Fuse board is the most important electrical safety device in the home or workplace, it has two vital functions;

1) Protecting cables (and subsequently appliances) from overload which can cause fire, and

2) Protecting humans from the electric shock caused by earth leakage.

All homes are different, from one-bedroom apartments in the city to larger country houses and all of them use electricity in various different ways. Some have electric showers, some have electric hobs, others have tropical fish tanks, some have outdoor lighting and water pumps while others have workshops and machinery. There are some homes that solely rely on electricity for heat and particularly in these current times, many people are working from home and are using significantly more electricity than ever!

For this reason, there is no such thing as a 'standard consumer unit', but while the number of sizes, brands and combinations of configurations is almost infinite, there are in fact only four main types of consumer units.

Used in conjunction with the circuit protection devices (RCD, RCBO, MCB) these four types of consumer units offer the homeowner and electrician huge flexibility of circuit design and budget. It is important to understand that in most domestic properties it would be possible to use any one of the four types of consumer unit, the decision being governed by budget and attitude to circuit separation.

The four main types of consumer unit

  • Dual RCD Consumer Unit​​​​​​​   

A dual RCD Consumer Unit is supplied with the main switch and two RCDs and offers a cheaper solution.

Consideration must be given to circuit design in this situation. You should not, for example, put all of the lighting circuits on the same RCD as an earth leakage fault on one of those circuits will cut power to the entire bank leaving your home with no lighting.

Despite the limitations of dual RCD consumer units, they remain extremely popular due to the cost. Most 'fully loaded' consumer units are dual RCD configurations.

  • High Integrity Consumer Unit  

​​​​​​​With three neutral bars, which in essence gives three banks of circuits a high integrity consumer unit offers the best of both worlds.

Allowing for the use of RCBOs and two banks of MCBs they offer total circuit separation for critical circuits and highly cost-effective protection for standard circuits.

High integrity consumer units are becoming increasingly popular with electricians- because they make circuit design easier and homeowners- because they offer excellent protection without breaking the bank. They are particularly good in projects requiring 12 or more circuits.

  • Main Switch Consumer Unit 

​​​​​​​A Main Switch Consumer Unit is so-called because it is supplied empty of all protection devices except the main switch. Whilst it may be populated with an RCD and MVBs.

Many electricians consider this the best circuit protection solution as each circuit is protected from overload and earth leakage individually, thus preventing nuisance tripping caused by earth leakage on other circuits.

  • RCD Incomer Consumer Unit  

​​​​​​​An RCD Income Consumer Unit is a special type of protection device., generally used in workshops, garages, garden offices and sheds which use small amounts of circuits.

The defining difference between this and other types of consumer units is the fact that it does not have a 'main switch'. Isolation to the board is handled by a single RCD. In other words, all incoming electricity is managed by the RCD, hence the name.

This type of consumer unit offers no circuit separation as it may only be populated with MCBs. Earth leakage on every circuit in the arrangement is dealt with by the one RCD. That means that residual current fault on any circuit will cut power to all other circuits. For this reason, they are almost never used in the main dwelling.