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

(f) Values of k for bare conductor where there is no risk of damage to any
neighbouring material by the temperatures indicated
Material of conductor
Copper
Aluminium
Steel
Assumed initial temperature
Final temperature
Copper conductors
Aluminium conductors
Steel conductors
Visible and in
restricted areas
228
125
82
30°C
500°C
300°C
500°C
Conditions
Normal conditions Fire risk
159
105
58
30°C
200°C
200°C
200°C
Table 11(3)
Minimum Cross-sectional Area of Protective Conductor for
Circuits Protected by HBC Fuses to BS88 Part 2
138
91
50
30°C
150°C
150°C
150°C
Fuse Rating (Amp)
Minimum
cross-sectional
6 10 16 20 32 50 63 80 100 160 200 250 315 400
area (sq. mm)
of protective
Copper 1 1 1 1.5 2.5 4 6 10 10 16 25 25 35 50
conductor for
5 sec.
disconnection
Aluminium 16 16 16 16 16 16 16 16 16 25 35 50 50 70
Minimum
cross-sectional
area (sq. mm)
of protective
conductor for
0.4 sec.
disconnection
Copper 1 1 1 1 1 2.5
79