When should a consumer unit be replaced?

The consumer unit (often still called the fuse box) is where your home’s electricity supply is divided into circuits, and where each circuit is protected. Modern units protect people as well as cables. Older boards often protect only the cables.

Signs it is time to replace it

• It has rewireable fuses: a carrier with a length of fuse wire.
• There is no RCD protection. A residual current device detects current leaking to earth, for example through a person, and disconnects in a fraction of a second. Older boards often have none.
• It has a plastic enclosure and you are having work done. For consumer units in homes, the current wiring regulations require a non-combustible enclosure, usually steel.
• There is no space for new circuits, and you are planning a kitchen, extension, garden room, heat pump or EV charger.
• An EICR has recommended replacement.
• It shows signs of damage or overheating: discolouration, a burning smell, crackling or buzzing.

If you see scorching, smell burning or hear crackling, do not wait. Switch off at the main switch if it is safe to do so, and get it checked.

What a modern consumer unit provides

• RCD protection for circuits, arranged so a single fault does not cut power to the whole house. Many installers use RCBOs, which combine a circuit breaker and an RCD for each circuit.
• Circuit breakers that disconnect faster and more consistently than fuses, and are reset rather than rewired.
• Surge protection, which the current wiring regulations require to be assessed for new installations.
• Arc fault detection devices (AFDDs), which the current regulations recommend for many final circuits and require in some higher-risk types of building. Whether they are right for your home is worth discussing.
• Clear labelling of every circuit.

Why testing comes first

A new consumer unit with RCD protection is far more sensitive to faults than an old fuse box. Existing faults that went unnoticed, such as damaged insulation or a neutral shared between circuits, will cause RCDs to trip, sometimes as soon as the power is restored.

That is why a proper replacement starts with checks of:

• the earthing arrangement and main protective bonding to gas and water pipes
• the insulation resistance of each circuit
• the condition of the existing wiring

If something is found, you can decide how to deal with it before the day, rather than partway through.

Is it notifiable?

In England, replacing a consumer unit is notifiable building work under Part P of the Building Regulations. A registered competent person can self-certify the work and notify building control for you. Otherwise, you must notify building control before the work starts. See electrical work and Building Regulations.

Should you rewire instead?

If the wiring itself is old (rubber or fabric-insulated cable, or a mix of several generations), replacing only the consumer unit may not be the right investment. An EICR will tell you. If a rewire is likely in the next few years, it usually makes sense to do both together.

For consumer unit replacement in Harrogate, York and Wetherby, see our consumer unit upgrades service.