Fuse box / consumer unit

Most commonly it is near the meter: in a hallway, under the stairs, in a cupboard, in the garage, or in an external meter box. In flats it is often in the entrance hall or a service cupboard.

It should be reachable without moving furniture or standing on something. If yours is behind stored items or boxed in, clearing access is worth doing before any electrical visit.

It matters practically and it is expected: circuits should be identified so anyone can isolate the right one in a hurry. Unlabelled or wrongly labelled boards are a frequent observation on inspection reports.

Circuit identification is normally produced as part of testing, because the circuits have to be proven rather than guessed from the old labels.

Common reasons an upgrade is considered: an old board with rewireable fuses, no RCD protection, a plastic enclosure in a domestic property, no spare ways for new circuits, signs of overheating, or an inspection report recommending it.

Age alone is not the deciding factor. The existing earthing and bonding, the condition of the circuits and the reason for the change all need checking first, because a new board on defective circuits can reveal faults rather than fix them.

Since January 2016, consumer units installed in domestic premises have been required to have a non-combustible enclosure — in practice, metal — or to be enclosed in a non-combustible cabinet. That rule applies to new installations.

An existing plastic board is not automatically unlawful or dangerous, and it does not have to be ripped out on that basis alone. It is assessed on its condition and on whether it still provides suitable protection.

Rewireable fuse boards give no earth-leakage (RCD) protection, are easy to fit with the wrong fuse wire, and usually sit alongside other dated arrangements such as missing main bonding. They are a very common reason for an upgrade recommendation.

The sensible order is an inspection first: it establishes the state of the circuits and earthing, so the replacement is specified on evidence rather than assumption.

On a dual-RCD or split-load board, one RCD covers a group of circuits, so a fault on any one of them takes the whole group off — including, often, your lights and your freezer.

With RCBOs, each circuit has its own combined device, so a fault only disconnects the affected circuit. It costs more but it contains the inconvenience, and it makes fault finding much simpler.

A surge protective device limits transient overvoltages — from lightning on the network or from switching events — that can damage electronics, boilers, EV equipment and smart devices. Since the 2018 regulations plus amendments, SPDs are expected in most new installations unless a documented risk assessment decides otherwise.

Fitting one is normally considered when a consumer unit is being replaced, since it mounts in the board.

An arc fault detection device looks for the electrical signature of arcing — the kind produced by a damaged cable or a loose terminal — and disconnects before it can start a fire. Normal protective devices do not detect that condition.

They are recommended rather than universally required in domestic work, and are most often discussed for higher-risk situations such as sleeping accommodation or buildings with timber construction.

Tails are the two large cables between the meter and the consumer unit. Older installations often have undersized tails, no separate isolator, or tails that are too long, all of which get picked up when a board is replaced.

A main switch isolator between the meter and the board is often fitted at the same time, so the installation can be switched off in future without the supplier being involved.

Yes — the supply has to be off for the changeover, and the circuits are then tested before being put back into service. Plan for the fridge and freezer to be closed and for any medical or work equipment that needs power to be arranged around it.

The actual duration depends on the size of the installation and what the testing finds, so it should be confirmed as part of the written scope rather than assumed.

A modern board applies protection the old one did not. Circuits that were quietly leaking to earth for years — damp outdoor lighting, an ageing shower, a failing appliance — now trip an RCD that previously was not there.

This is why circuits are tested before and after a change, and why a pre-existing fault should be identified and priced as separate remedial work rather than discovered on the day.