Consumer Units / Fusebox
What you need to know
From 1st January 2016, all consumer units installed or replaced in domestic properties are required to be made of or be enclosed by a non-combustible material, typically a ferrous metal such as steel.
Existing plastic consumer units can be retained for alterations and additions, unless they show signs of thermal damage or the manufacturer’s design has been altered. This does not mean your existing plastic consumer unit is necessarily unsafe but it does mean if you are having it replaced, it will need replacing by a non-combustible one.
Benefits of a modern Consumer Unit:
RCD (Residual Current Device): a safety device designed to protect against personal electric shock. These trip when a circuit overloads, protecting the wiring from burning out and your family from nasty electrical shocks.
Circuit Breakers: In the event of an electrical wiring fault the circuit breakers will trip whereas in the old type of fusebox there is the potential that the electricity supply would stay connected until a fire occurs. The built in circuit breakers will trip within 40 millionths of a second if you accidentally touch any live cables, this will save the life of the person touching them.
SPD (Surge Protection Device): The surge protective device (SPD) is a kind of product that protects valuable electrical and electronic equipment against transients, originating from lightning and also from switching sources. Surge protective devices are devices consisting mainly of voltage-controlled resistors (varistors, suppressor diodes) and/or spark gaps (discharge paths).
RCD (Residual Current Device) Information
The UK standard for safety – Since July 2008 virtually all circuits in new or rewired homes have been required to include an RCD under the latest edition of BS 7671.
What does an RCD DO?
An RCD is a sensitive safety device that switches off electricity automatically if there is a fault.
An RCD is designed to protect against the risks of electrocution and fire caused by earth faults. For example, if you cut through the cable when mowing the lawn and accidentally touched the exposed live wires or a faulty appliance overheats causing electric current to flow to earth.
How does it work?
An RCD constantly monitors the electric current flowing through one or more circuits it is used to protect. If it detects electricity flowing down an unintended path, such as through a person who has touched a live part, the RCD will switch the circuit off very quickly, significantly reducing the risk of death or serious injury.
SPD (Surge Protected Device) Information
The whole nature of how electrical equipment is used in homes and at work has evolved; with everyday activities relying on electronic equipment.
Products such as computers, printers, televisions, industrial control equipment such as PLC’s, alarms, microwaves and washing machines are common place. These can all be vulnerable to transient overvoltages, which can significantly reduce the equipment’s lifespan through degradation and damage.
A transient overvoltage or surge is a short duration increase in voltage measured between two or more conductors. In short this means anything from microseconds (millionths of a second) to a few milliseconds (thousandths of a second) in duration.
From January 2019, the 18th Edition of the IET Wiring Regulations require all new electrical system designs and installations, as well as alterations and additions to existing installations, to be assessed against the risk from surge voltage damage and where necessary, protected using SPDs (Surge Protected Devices).
Contractors will need to install SPDs (Surge Protected Devices) to protect against transient overvoltages in situations where there may be serious consequences. These are listed as loss of life or serious injury, interruption to public services, interruption of commercial activity, damage to cultural heritage, or impact on sites with large numbers of people.
At all other sites (apart from single dwellings in some situations) a simplified risk assessment will determine the need for SPDs (Surge Protected Devices).
SPD (Surge Protected Device) FAQ:
What does surge protection do?
A surge protection device is designed to protect electrical devices such as computers and TV's from voltage spikes. The surge protection device (SPD) attempts to lessen the voltage supplied to an electrical device by either blocking or shorting to ground any unwanted voltages above a safe standard.
Do you really need surge protection?
If electrical equipment is used then a surge protection device is definitely needed as electrical equipment comes with sensitive components that could be damaged very easily. A surge protection device will increase the longevity of electrical equipment.
Can a power surge damage a TV?
Yes, electrical surges have the capacity to overload and short out any electrical equipment in a home, significantly degrading the life of the equipment. Anything that is plugged into a wall can be affected by electrical surges.
AFDD (Arc Fault Detection Devices) Information
AFDDs are protective devices installed in consumer units to provide protection from arc faults. They use microprocessor technology to analyse the waveform of the electricity being used to detect any unusual signatures which would signify an arc on the circuit. This will cut off power to the affected circuit and could prevent a fire. They are far more sensitive to arcs than conventional circuit protective devices.
Arcs are visible plasma discharges caused by electrical current passing through a normally nonconductive medium, such as, air. This is caused when the electrical current ionizes gases in the air, temperatures created by arcing can exceed 6000 °C. These temperatures are sufficient to start a fire. An arc is created when the electrical current jumps the gap between two conductive materials. The most common causes of arcs include, worn contacts in electrical equipment, damage to insulation, break in a cable and loose connections, to mention a few.
AFDD (Arc Fault Detection Devices) FAQ:
Do I need to install Arc Fault Detection Devices?
The electrical designer/installer is best placed to offer advice on the installation of AFDDs.
In the current edition of the IET Wiring Regulations, BS 7671:2018, it is a recommendation to install
AFDDs but the customer can choose to omit them. However, this decision should be based
considering any relevant risk and safety factors against the cost of installation.
Do I need to install an AFDD on every circuit?
In some cases, it may be appropriate to protect particular final circuits and not others but if the risk is
due to fire propagating structures, for example, a timber framed building, the whole installation should
Many older fuse boxes use a piece of fuse wire which is designed to burn out under load. These wires need replacing every time they are overloaded - additionally they can become brittle and break due to everyday usage.
If you have a fuse box like those shown below you would benefit from an upgrade to a new modern consumer unit (fuse box) with circuit breakers instead of fuse wires, and RCDs for additional protection.
A Residual Circuit Device (RCD) protects by constantly monitoring the current flowing in the live and neutral wires supplying a circuit or an individual item of equipment.