Electrical Terminology

Electrical terms are often difficult to understand.  Here are some definitions in plain English meant to help everyone understand what is being discussed.

Accessory – switches, sockets, ceiling roses etc. found in most installations.

BS7671 – the UK national safety standard for electrical installation work (The Regulations or “Regs”).

Chasing – making slots or grooves into walls in order to allow the installation of cables or wiring systems.

Circuit breaker – a device that switches off the current to a circuit in the case of a fault, normally a short circuit or a when too much demand is put on the circuit (too many lights/power tools/electric showers/etc) are being used at the same time (an Overload).  Can be reset by switching back on.

Consumer Unit – a consumer unit or fuse box is used to control and distribute electricity around the home or business. It usually contains a main switch, fuses or circuit breakers and one or more residual current devices (see RCD).

Earthing – the purpose of earthing is to minimise the risk of a person or animal receiving an electric shock.  Earthing metal parts of an installation (pipes, conduit, metal parts of electrical devices) allows current to flow briefly through the earthing cables which will trigger the fuse, circuit breaker, or RCD to switch the circuit off, removing the danger.  An electrician will check that the earthing and bonding is satisfactory before starting any work. Earthing cables (also known as Circuit Protective Conductors or CPCs are normally coloured green and yellow).

Electrical Installation Certificate – A safety certificate issued by the electrician on completion of a new electrical installation or after completing work on  an existing electrical installation. The certificate confirms that the installation had been designed, built, inspected and tested to the British Standard of BS7671.

Flush Fitted – electrical accessories such as switches or sockets installed so that their back boxes are contained in a wall, floor or ceiling and only the front plates are visible. Flush fitting is more aesthetically pleasing but usually involves chasing (see chasing).

Fuse Box – see consumer unit.

Fused Connection Unit – enables electricity to be supplied to an item of equipment or appliance providing its own method of circuit protection (by fuse), and sometimes includes a switch. Fused connection units are sometimes referred to in the electrical trade as fused spurs (see spurs)

LED – Light Emitting Diode.  A semiconductor that emits light. A low energy light alternative that uses extra-low voltage DC current to operate.  Requires a transfomer and a driver, but these devices are often incorporated into light bulbs so they can be used at mains voltage.

Main Bonding – connecting metal pipes (gas, water or oil) entering premises to the main earthing terminal (MET) of the electrical installation via low resistance conductors.

Mains Voltage – the voltage normally found throughout electrical installations in the UK, normally 240 volts.  Some parts of installations may have reduced voltages for safety purposes (lighting in bathrooms, fans in bathrooms, outdoor lighting).  Reducing the voltage requires the use of a transformer.

Making Good – restoring the finish of a wall or ceiling that has been damaged and replacing floor boards which have been lifted during the electrical installation work. Usually does not cover full redecoration, but will be the filling in of chases (see chasing) and holes. You may agree with the electrician to leave the making good of walls and ceilings to another person such as a plasterer.

MCB – Miniature circuit breaker (see circuit breaker).

Minor Works Certificate – a safety certificate (see Electrical Installation Certificate) used when only an addition or alteration is made to an electrical installation.

Partial Rewire – a common situation where it has not been possible or necessary to fully rewire (see rewire) the electrical installation. For example when cabling has been confirmed as being suitable for continued use to minimise the degree of damage and disruption to the decoration. Or where only a part of an electrical installation has suffered damage from a burst water pipe or similar. If you are considering a partial rewire or it is offered to you as an option by an electrician it is very important that you agree and understand exactly what work is and is not being undertaken before the work starts.

Part P – the specific section of the Building Regulations for England and Wales which relates to electrical installations in domestic properties.

Periodic Inspection Report (PIR) – A report on the condition of an existing electrical installation. Containing an overall assessment of the safety of the installation, observations on its condition, and a number of recommendations (in order of priority) for actions, if any required, to restore the installation to a satisfactory condition for continued service. ****Replaced in 2011 by the Condition Report****

RCD – Residual current device. This is a sensitive switching device that trips a circuit when an earth fault is detected. RCD protection is protects people and animals from electric shock.  Circuit breakers do not protect against shock, they only protect against thermal (heat) damage. Older homes benefit the most by having new consumer units installed that incorporate RCDs, making the installation much safer for the people that live or work there.

Rewire –  the process of installing new cables, circuits and accessories and carrying out the inspection and testing before putting the installation into service. A full rewire should mean that all parts of the electrical installation are new. However you may wish for items such as switches and light fittings to be re-used and the electrician may wish to re-use part of the installation which is electrically sound, due to it being difficult to remove and replace. It is very important that you agree and understand with the electrician exactly what work is, and is not, being done before the work starts (see partial rewires).

Spur – an additional connection often taken from an existing accessory such as a socket. It may provide a supply to a new socket or a fused connection unit (see fused connection unit)

Supplementary Bonding – the connecting together of the metal parts of electric equipment (such as a heated towel rail) and the metal parts of a non-electric item (such as pipes) to prevent a dangerous voltage between them, if a fault occurs. May be required in bath and shower rooms.

Surface Mounted – this is where wiring or electrical accessories such as switches or sockets are installed so that they are on top of the surface or front of a wall, floor or ceiling. This causes less disruption to the decoration but is not as aesthetically pleasing as flush fitting (see flush fitted).

Trunking – a plastic enclosure having one removable side that is used to install cable on the surface of walls and ceilings.

If you’re unsure of anything, do not hesitate to get in touch with us with any questions. 

Information taken from the Electrical Safety Council working in partnership with The Institution of Engineering and Technology.