Conductors must be clearly identified by position or labelling at a distribution board or consumer unit.
Sometimes it is found that the neutral or protective conductors of outgoing circuits have been indiscriminately connected at a consumer unit or a distribution board. This can lead to danger if, as a result, an incorrect neutral for example, is disconnected.
Solution
Conductors must be so arranged or marked that they can be identified for inspection, testing, repair or alteration of the installation (Regulations 314.1.4 and 514.1.2 refer).
In a single-phase installation, neutral and protective conductors will normally be connected to their respective bars in sequence. For example, the neutral and protective conductor of the first terminal, the second to the second etc. so that additional marking would not be needed.
In a three-phase and neutral installation, identification of neutral and protective conductors can be difficult if the arrangement of terminals on the neutral and protective conductor bars does not correspond exactly with that of the line terminals. In such a case, additional marking of the conductors by, for example, numbering, would be needed.
Some manufacturers provide a neutral bar and protective conductor bar chart in addition to the chart for protective devices.
A clear indication of the neutral and protective conductor connections is necessary and should always be provided when the layout of the associated bars differ from the layout of the protective devices.
Regulation 314.4
Where an installation comprises more than one final circuit, each final circuit shall be connected to a separate way in a distribution board. The wiring of each final circuit shall be electrically separate from that of every other final circuit, so as to prevent the indirect energising of a final circuit intended to be isolated.
Regulation 514.1.2
As far as is reasonably practicable, wiring shall be so arranged or marked that it can be identified for inspection, testing, repair or alteration of the installation.
This article is extracted from Snags and Solutions Part 1 or Part 2 published by NICEIC
