Whether you are just having some new lights or sockets fitted or you’re having your whole house rewired, it will help to have an idea of the terms your electrician will use and the difference between a consumer unit and a RCD.  To help you and us talk a common language we’ve put together a list of common industry terms that will help to put you at ease.

BS 7671 – British Standard

Also known as the IEE (Institute of Electrical Engineering) wiring regulations and is the standard that all electrical installations must adhere to.

Building Compliance Certificate
Might also be referred to as a Part P certificate.  It is confirmation sent to the householder that the contractor has notified the work to the local authority via their competent person scheme.  It is an importnat document that states the work is compliant to the building regulations and will be needed when the property is due to be sold.

An assembly of electrical equipment (socket outlets, lighting points and switches) supplied from the same origin and protected against over current by the same protective device(s).
Circuit Breaker or RCD
A device capable of making, carrying and breaking normal load currents and also making and automatically breaking, under pre-determined conditions, abnormal currents such as short-circuit currents. It is usually required to operate infrequently although some types are suitable for frequent operation.
Class I Equipment
Equipment in which protection against electric shock does not rely on basic insulation only, but which includes means for the connection of exposed-conductive-parts to a protective conductor in the fixed wiring of the installation. Class I equipment has exposed metallic parts, e.g. the metallic enclosure of washing machine.
Class II Equipment
Class II equipment, such as music systems, television and video players, in which protection against electric shock does not rely on basic insulation only, but in which additional safety precautions such as supplementary insulation are provided, there being no provision for the connection of exposed metalwork of the equipment to a protective conductor, and no reliance upon precautions to be taken in the fixed wiring of the installation.
Class III Equipment
Class III equipment, for example for medical use, in which protection against electric shock relies on supply at SELV (Safety extra low voltage) and in which voltages higher than those of SELV are not generated. Class III equipment must be supplied from a safety isolating transformer.
Consumer Unit
Also known as a fusebox, consumer control unit or electricity control unit. A particular type of distribution board comprising a co-ordinated assembly for the control and distribution of electrical energy, principally in domestic premises, incorporating manual means of double-pole isolation on the incoming circuit(s) and an assembly of one or more fuses, circuit-breakers, residual current operated devices or signalling and other devices purposely manufactured for such use.
Distribution Board
An assembly containing switching or protective devices (e.g. fuses, circuit-breakers, residual current operated devices) associated with one or more outgoing circuits fed from one or more incoming circuits, together with terminals for the neutral and protective circuit conductors. It may also include signalling and other control devices. Means of isolation may be included in the board or may be provided separately.
Electrical Installation Certificate
Any electrician installing a new electrical installation (including a single circuit), altering, extending or adapting an existing circuit should issue the homeowner with electrical installation certificate or minor electrical installation works certificate to confirm the work complies with the requirements of BS 7671.

Electrical Installation Condition Report (EICR)

Formerly called a Periodic Inspection Report (or PIR). A report to establish the overall condition of all the electrics in a building, stating whether it is satisfactory for continued use and detailing any work that might need to be done.
Electrical Installation
Any assembly of electrical equipment supplied by a common source to fulfil a specific purpose.
Extension Leads
An extension cable, also known as a power extender, extension cord or an extension lead, is a length of flexible electrical power cable or flex with a plug on one end and one or more sockets on the other end – usually of the same type as the plug. However use of extension leads should be avoided where possible, as there is a chance of overloading the circuit.
Extra Low Voltage (ELV)
Normally not exceeding 50 V a.c. or 120 V ripple-free d.c. whether between conductors or to earth.
Milliamp or 1/1000 part of an amp – a unit of electric current.
Electrical current (in amps) that exceeds the maximum limit of a circuit. May result in risk of fire or shock from insulation damaged from heat generated by overcurrent condition.
Part P
The specific section of the Building Regulations that provides minimum safety standards for domestic electrical installations.  The Building Regulations are a devolved power so the actual requirements may vary across the UK dependent on which country the work is being done in.
Portable Appliance Testing (PAT)
Inspection and testing of electrical equipment including portable appliances, moveable equipment, hand held appliances, stationary equipment, fixed equipment/appliances, IT equipment and extension leads.
Periodic Inspection Report (PIR)
An electrical survey to reveal if electrical circuits are overloaded, find potential hazards in the installation, highlight any lack of earthing or bonding and carry out tests on the fixed wiring of the installation. The report is known as an Electrical Installation Condition Report (EICR) and will establish the overall condition of all the electrics, state whether it is satisfactory for continued use and detail any work that might need to be done.
Platinum Promise
Platinum Promise is NICEIC’s commitment to making sure that all work undertaken by NICEIC registered contractors is to standard. If work is found to be sub-standard within six years of completion, the Platinum Promise will ensure the original contractor puts the work right or commission an alternative contractor up to the value of £25,000 per installation.
Portable equipment
Electrical equipment which is less than 18 kg in mass and is intended to be moved while in operation or which can easily be moved from one place to another, such as a toaster, food mixer, vacuum cleaner, fan heater.Prospective fault current
The value of overcurrent at a given point in a circuit resulting from a fault between live conductors.

RCD – Residual Current Device
Residual current device is a safety device that switches off the electricity automatically when it detects an earth fault, providing protection against electric shock.
Ring final circuit/ring main
A final circuit connected in the form of a ring and connected to a single point of supply.
Separated Extra-Low Voltage. An extra-low voltage system, which is electrically separated from Earth and from other systems in such a way that a single fault cannot give rise to the risk of electric shock.