Consumer Unit & Fuse Board Replacements

Consumer unit (CU) = board = fuse board = fuse box = distribution board (DB).

Reasons to Replace

There are multiple reasons that you might decide to replace your consumer unit (CU), such as RCD protection (for safety), metal enclosures (for fire safety), MCB/RCBO switches instead of fuses (for convenience and safety), or to aid in compliance of new or future electrical installation work. Another benefit is that all circuits must pass testing, meaning that existing faults on the installation must be rectified before completion of a replacement consumer unit. Although this may incur additional cost to rectify, it is ensuring better safety of the installation.

Circuit Breakers

Circuit breakers, such as Minatare Circuit Breakers (MCB) and fuses are used to turn a circuit on and off, as well as providing overload protection and short circuit fault protection.

RCDs

A Residual Current Device (RCD) is a life-saving electrical safety switch designed to protect people from fatal electric shocks and reduce the risk of electrical fires. They work by monitoring the incoming (line) and outgoing (neutral) wire’s current on a circuit, and if they are not balanced then the RCD will automatically operate and switch off – in other words, when the current on the circuit is going somewhere it shouldn’t, like earth faults from damaged cables or a person touching a live cable. RCDs are very sensitive compared to circuit breakers and fuses – additional protection RCDs are rated at 30mA (0.03 amps). As a comparison, the current needed to trip a common type B 32A circuit breaker in a short circuit fault can be up to 160A.

Consumer Unit Types

There are two main types of modern consumer unit available, split load RCD boards and RCBO boards. Split load boards are the less expensive older type where the circuit breakers are split in half and one RCD covers each half. This means if an earth fault occurs on one circuit or RCD it will turn off half of your home electrics. RCBOs are the more expensive newer type which consist of a circuit breaker and RCD in one device, meaning every circuit has it’s own RCD. If an earth fault occurs it will turn off only that circuit.

Here’s an example of a split-load RCD consumer unit (the RCDs are the two devices with yellow test buttons):

Surge Protection

Surge Protection Devices (SPD) are replaceable cartridges that divert electrical surges that could otherwise damage sensitive electrical equipment and expensive electronics. The ones found in consumer units are Type 2 which divert surges from the incoming mains electrical grid. Clients can opt-out of having SPDs by signing a form, but it’s worth having in modern homes, and SPDs come integrated in most new CUs.

The Process

To quote a consumer unit replacement the property needs to be visited to check the number of existing circuits, the condition of the installation, and if protective bonding is present. This is because when a board is replaced it is classed as new work so needs to meet certain safety standards. Each circuit must pass a number of tests such as CPC continuity, that class 1 equipment is earthed, continuity of ring circuits, polarity, insulation resistance, Zs values, and RCD trip times. If any circuit has faults below a certain standard, they will need to be rectified or the circuit isolated before completion can happen. With older existing properties and electrical installations, it’s very possible to find multiple faults on an installation – or none at all!

The consumer unit replacement itself can be quoted for fairly accurately, but finding faults is charged by the hour, as it’s impossible to guess how long it will take to find and fix it, it could be quick, it could take all day. It is recommended to at least book in a hour or two of labour to roughly test the installation for any faults, so that the homeowner can make an informed decision on whether they want to go ahead with the consumer unit replacement, and get the faults fixed beforehand. The other option is to risk it, replace the board, and if there are any faults found, put the money that would have been spent on the few hours pre-testing labour into any fault finding and rectification after the board has been replaced.

Price

See the pricing page for example consumer unit replacement prices, or get in touch for a free quote!