When should a fuse box or consumer unit be replaced?

An old board is not automatically unsafe

There is no rule that a fuse box has to be replaced after a certain number of years, and an older board is not illegal. Rewireable fuses, cartridge fuses and older circuit breakers can still protect circuits against overload when they are correctly rated and in good condition. Electrical Safety First’s guidance is that a consumer unit without RCDs or circuit breakers is not necessarily unsafe, and does not automatically need upgrading.

The wiring regulations are updated from time to time, and each change applies to new work. An installation is not required to be upgraded every time the standard moves on. What matters is whether it is still safe, and that is what an inspection establishes. If you already know the board needs changing, consumer unit replacement explains how the work is done.

Reasons a replacement is worth considering

Damage or signs of heat

Scorch marks, discoloured or melted plastic, a burning smell, crackling or buzzing, a cracked casing or a board that feels warm are reasons to have it looked at promptly, whatever its age. If there is a burning smell or visible scorching, switch off at the main switch if you can reach it safely, do not touch anything that looks damaged, and get an electrician out.

No RCD protection

An RCD disconnects the supply when it detects current leaking to earth, for example through a person touching something live. Current standards require 30 mA RCD protection for most socket-outlets and for cables concealed in walls in new work, and many older boards have none. On its own that does not make a board dangerous, and there can be ways of adding protection without a new board, but it is one of the strongest reasons to replace. In the meantime, a plug-in RCD is a sensible precaution for anything used outdoors.

An inspection has found a problem with the board

If an EICR has recorded an observation against the consumer unit, a replacement may be the answer, but not always. A single faulty device or a damaged component can sometimes be dealt with on its own. Ask what the observation is and what the options are before assuming the whole board has to go.

New circuits with nowhere to go

A new shower, cooker, extension, garden office, heat pump or car charger usually needs its own circuit, and that circuit needs a suitable protective device and, in most cases, RCD protection. If the board has no spare space, or cannot provide that protection, changing it at the same time as adding the circuit is often the practical answer.

One RCD taking out half the house

Many boards use a single RCD to protect a group of circuits. A fault or leakage on any one of them switches off all of them, sometimes including the lights. A board with separate RCD protection for each circuit limits a trip to the circuit with the problem. A new board does not cure the fault causing the trips, though; that needs finding first. Why does my RCD keep tripping? explains the likely causes.

A patchwork of boards and add-ons

Some properties have an old fuse box with extra switches and small boards added beside it over the years. Each addition may have been reasonable at the time, but the result can be hard to understand, label and maintain. Rationalising it into one consumer unit is often done as part of a larger job such as a rewire.

Plastic consumer units

Since 1 January 2016, consumer units installed in homes have had to have an enclosure made of non-combustible material, usually steel, or be housed in a non-combustible cabinet. The requirement applies when a consumer unit is installed or replaced. An existing plastic unit is judged on its condition at inspection, like any other part of the installation, rather than being replaced simply because of what it is made of.

What replacement involves

In England, replacing a consumer unit is notifiable work under the Building Regulations. It has to be notified to building control, or carried out and self-certified by an electrician registered with a competent person scheme. The existing circuits are tested as part of the job, because a modern board can reveal faults an older one did not react to. Expect the power to be off for much of the day, and to receive an Electrical Installation Certificate and confirmation of Building Regulations compliance afterwards.

Replace, repair or leave it?

• Leave it and keep an eye on it if it is in good condition, a recent inspection was satisfactory and nothing new is planned.
• Repair it if the problem is one device or component and the rest of the board is sound.
• Replace it if it is damaged, cannot give new circuits the protection they need, has been coded in a way a repair will not resolve, or the house is being rewired.

The difference between a fuse box, a consumer unit and the devices inside them is explained in Fuse box vs consumer unit.

Getting a straight answer

If you are unsure whether yours needs replacing, ask. I will tell you if the board can stay, and if it cannot, the reason. Local pages for Southampton and Eastleigh cover the work in those areas.