to the 16th Edition IEE Regulations

 chapter 1 The IEE Regulations chapter 2 Installation Requirements and Characteristics chapter 3 Installation Control and Protection chapter 4 Cables, Conduits and Trunking chapter 5 Earthing chapter 6 Circuits chapter 7 Special Installations chapter 8 Testing and Inspection chapter 9 Data cabling and Networks
 Cables, conduits and trunking
 4.1 - Cable insulation materials 4.4 - Cable supports, joints and terminations 4.2 - Cables 4.5 - Cable enclosures 4.3 - Cable choice 4.6 - Conductor and cable identification
 ------------------------------------------------------------------ 4.3.1 - Cable types 4.3.8 - Protection by semi-enclosed (rewirable) fuses 4.3.2 - Current carrying capacity of conductors 4.3.9 - Cable rating calculation 4.3.3 - Methods of cable installation 4.3.10 - Special formulas - grouping factor calculation 4.3.4 - Ambient temperature correction factors 4.3.11 - Cable volt drop 4.3.5 - Cable grouping correction factors 4.3.12 - Harmonic currents and neutral conductors 4.3.6 - Thermal insulation correction factors 4.3.13 - Low smoke-emitting cables 4.3.7 - When a number of correction --------- factors applies 4.3.14 - The effects of animals, insects and plants

4.3.10 - Special formulas for grouping factor calculation

In some cases the conductor sizes where cables are grouped and determined by the methods shown in {4.3.9} can be reduced by applying some rather complex formulas given in [Appendix 4].

Whilst it is true that in many cases the use of these formulas will show the installer that it is safe for him to use a smaller cable than he would have needed by simple application of correction factors, this is by no means always the case. There are many cases where their application will make no difference at all. Since this book is for the electrician, rather than for the designer, the rather complicated mathematics will be omitted.