Code of Practice for the Electricity (Wiring) Regulations - 2009 Edition

(c) Values of k for protective conductor incorporated in a cable or bunched
with cables, where the assumed initial temperature is 70°C or greater
Material of conductor
Copper
Aluminium
Assumed initial temperature
Final temperature
* Above 300mm 2
70°C
thermoplastic
115/103*
76/68*
70°C
160°C/140°C*
Insulation material
90°C
thermoplastic
100/86*
66/57*
90°C
160°C/140°C*
90°C
thermosetting
143
94
90°C
250°C
(d) Values of k for protective conductor as a sheath or armour of a cable
Material of conductor
Aluminium
Steel
Lead
Assumed initial temperature
Final temperature
70°C
thermoplastic
93
51
26
60°C
200°C
Insulation material
90°C
thermoplastic
85
46
23
80°C
200°C
(e) Values of k for steel conduit, ducting and trunking
as the protective conductor
90°C
thermosetting
85
46
23
80°C
200°C
Material of protective conductor
70°C
Insulation material
90°C
90°C
thermoplastic thermoplastic thermosetting
Steel conduit, ducting and trunking 47 44 58
Assumed initial temperature
50°C
60°C
60°C
Final temperature
160°C
160°C
250°C
78