This glossary explains some of the terms and acronyms you may see in electrical reports and manuals.


NICEIC Area Engineer
  BS British Standard
  Circuit An assembly of electrical equipment supplied from the same origin and protected against overcurrent by the same protective device(s).

Circuit-breaker 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 (see BS 2754). Class I equipment has exposed metallic parts, e.g. the metallic enclosure of washing machine.

  Class II equipment Equipment 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 (see BS 2754). Class II equipment is identified by construction mark:
  Class III equipment Equipment in which protection against electric shock relies on supply at SELV and in which voltages higher than those of SELV are not generated (see BS 2754). Class III equipment is identified by construction mark:
  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 Any assembly of associated electrical equipment supplied from a common origin to fulfil a specific purpose and having certain co-ordinated characteristics.

  IEE Institution of Electrical Engineers
  IU Inspection Unit (half-day visit)
  LV Low Voltage
  mA Milliamp or 1/1000 part of an amp
  NICEIC National Inspection Council for Electrical Installation Contracting
Overcurrent A current exceeding the rated value. For conductors the rated value is the current-carrying capacity.
  PAT Portable Appliance Testing
  PIR Periodic Inspection Report
  PLI Public Liability Insurance
  Portable equipment
Electrical equipment which is moved while in operation or which can easily be moved from one place to another while connected to the supply.
  PQS Prospective Qualified Supervisor
  Prospective fault current The value of overcurrent at a given point in a circuit resulting from a fault of negligible impedance between live conductors having a difference of potential under normal operating conditions, or between a live conductor and an exposed-conductive-part.
  QS Qualified Supervisor
  RCD Residual current device
  Ring final circuit A final circuit arranged in the form of a ring and connected to a single point of supply
  SELV 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.

  Voltage, extra-low Normally not exceeding 50 V a.c. or 120 V ripple-free d.c., whether between conductors or to earth.