How much

What are we talking about?

How long does it typically take to replace a consumer unit of fuse box?

Typical time

8hrs, excluding any fault finding for a standard e.g. 10 way unit

Translate time to cost for your postcode by clicking on: Practical services and charges

Dependencies

The power will be off for most of the day. Freezers will be fine if closed. Temporary lighting may be required in the winter

Questions to ask

We usually need to inspect the existing installation (or see a photograph of the existing fuse box or consumer unit) as the space available can vary considerably. Knowing the size of the property helps

Comments

Replacing a consumer unit (or fuse box as the devices were previously known) can only be undertaken by a competent person. The work comes under Part P of the Building Regulations and must be certified and registered with Building Control. In order for the installation to be certified the installer must undertake a series of checks and test including:

• ensuring the earthing including the equipotential bonding is to a suitable standard. This means the main earth and the earths to the gas and water
• the installation as a whole including the wiring connected to the consumer unit is of a suitable standard. The installer effectively inherits what has gone before. Problems with ring mains, spurs on spurs and other issues can show up during the test and inspection phase.

The IEE 17th Edition (BS7671) came into effect in 2008. This introduced the requirement that cables in walls typically need to be RCD protected. As a result most 17th Edition most consumer units have two RCD's to ensure not everything trips at once. There are other solutions including RCBO's (circuit breakers and RCDs incorporated in a single unit) but these tend to cost more. The 18th Edition (2018 - by coincidence) effectively made RCDs compulsory and introduced SPDs (surge protection devices) and AFDDs (arc fault detection devices). Both are recommendations in domestic installations but are becoming the norm and SPDs, if not installed, require a risk assessment justifying the reason unless the value of the installation and electrical equipment fails to justify the provision.

The person carrying out the works may need to arrange temporary lighting. If the consumer unit is in an awkward place e.g. high up on the wall under a ceiling then the work may take longer. If it's under the stairs remember to clear out the cupboard and note that part of the rules dictate that adequate access is available at all times.

For a pictorial view of equipotential bonding and consumer units click here