Electrical Consumer Units

Consumer units have been called many different names over the years, such as fuse box, fuse board and dis-board. They are typically installed in domestic premises to provide control, distribution and protection to the various final circuits within the installation.

Modern electrical consumer units contain residual circuit devices (RCDs) and miniture circuit breakers (MCBs) which detect potential electrical overloads and shut down specific circuits, greatly reducing the risk of fire.

They now incorporate surge protection devices (SPD's) which - depending on the type of SPD - protect your electrical installation from direct or indirect lightning strikes, limiting the transient overvoltage to levels which are safe for connected equipment. This is a requirement for electricians to install. Although a customer may reject and it will be documented on the electrical installation certificate (EIC).

There are also Arc Fault Detection Devices (AFDD's) which are intended to protect against the effects of arcing faults by disconnecting the circuit when arc faults are detected. These are currently a requirement for:

● Higher Risk Residential Buildings (HRRB)

● Houses in Multiple Occupation (HMO)

● Purpose-built student accommodation

● Care homes

So you can see, some older fuse boxes do not have these features, which means you could unknowingly be at risk of fire or electric shocks, so it’s important a modern one is installed by a qualified, competent electrician.

Fuse board replacement & upgrade

If you are planning to carry out any electrical work in your property, now would be the right time to consider upgrading or a fuse board replacement. The new electrical circuit will most likely require to be RCD protected and your existing fuse box may not have an option for this.

No one likes the additional expense that this may add to your installation. However, to comply with the latest regulations (and to put it into perspective how quickly regulations have been changing - the current regs has been published and amended three times in the last six years) as well as to ensure that your property is safe, fuse board replacement may be mandatory in some cases.

It will also provide you with the opportunity to meet current regulations, install the ;latest protection devices, meet fire safety requirements, and provide additional capacity to future proof yourself for upcoming technologies ( solar PV, EV charging

Step by step to your consumer unit replacement

Planned or agree the consumer unit change
Undertake EICR or pre-work survey to ascertain if there are any immediate or potential dangers or any condition that would cause unwanted tripping of the RCD's. The survey should include:
- Enquire with customer if there are any known defects, faults or damages,
- An internal visual inspection of the existing consumer unit to determine, amongst other things, type and condition of the wiring and number of circuits.
- An external visual inspection of readily accessible parts, including suppliers service head, main earth size and tails, and customer bonding arrangements.
- Confirm if safe isolation can be achieved, otherwise customer must contact their supplier and request them to install an isolator before any work can commence.
Provide quote and confirm cost for the consumer unit replacement and agree date.
The day of replacement
- Initially, a measurement of external earth fault loop impedance, measurement of each final circuits earth fault loop impedance and circuit protective conductor continuity will be taken. If any tests indicate a danger then work will be ceased unless the defective circuits are left disconnected from the new consumer unit.
- Safe isolation and stripping out existing consumer unit
- Installing and wiring the new consumer unit including any upgrade of tails, main earth and protective bonding.
- Testing of existing circuits and their protection devices shall be performed.
Issue of the Electrical Installation Certificate (EIC) with any recommendations identified in the comments section on existing installation section, any defects which exist in the reconnected circuits.
Notification of the work done to building control shall be made on your behalf.