|What are we talking about?
||How long does it typically take to replace
a consumer unit of fuse box?
||8hrs, excluding any fault finding for a standard e.g.
10 way unit
||The power will be off for most of the day. Freezers
will be fine if closed. Temporary lighting may be required in the
|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
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. The main change at the consumer unit is caused
by 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 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
For a pictorial view of equipotential bonding
and consumer units click