Amendment 1 of the 17th edition of the Wiring Regulations brought changes to Appendix 4: selection of conductor cross sectional area (article excludes voltage drop and fault current calculations)
The current-carrying capacity of a cable corresponds to the maximum current that can be carried in specified conditions without the conductors exceeding the permissible limit of steady-state temperature for the type of insulation concerned. The values of current tabulated represent the effective current-carrying capacity only where no rating factor is applicable.
A rating factor has to be applied where the installation conditions differ from those for which values of current-carrying capacity are tabulated in Tables 4D1A to Tables 4J4A of Appendix 4. The first significant change introduced in the 17th edition, compared with the 16th edition, is the large number of rating factors related to cables buried in the ground.
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Autumn 2012 Issue of Wiring Matters Features:
Appendix 4 Conductor cross sectional area
Construction sites and CDM
What is an electrician?
Electric vehicles and PME
Electric vehicle charging
In-service Inspection and Testing
LED lighting
Wall socket protectors