Earthing Conductor Size- Good?

Cookie · Jan 31, 2021

Alright, so what do you think of these CPC sizes in relation to the phase conductors?

90*C insulation, TN-C-S supply

MCB / Live / CPC / Multiplier

15 - 2.08mm2 - 2.08mm2 - X 1

20 - 3.31mm2 - 3.31mm2 - X 1

60 - 13.30mm2 - 5.261mm2 - X 0.3955

100 - 26.67mm2 - 8.367mm2 - X 0.3137

200 - 85.01mm2 - 13.30mm2 - X 0.1564

300 - 177mm2 - 21.15mm2 - X 0.1195

400 - 304mm2 - 26.67mm2 - X 0.0877

500 - 456mm2 - 33.62mm2 - X 0.0737

600 - 760mm2 - 42.41mm2 - X 0.0558

0.3, 0.1 and 0.05 multiplier difference ever encountered in the UK?

pc1966 · Feb 3, 2021

If you paste these in to spreadsheet cells it should give you the k-values for copper, aluminium and iron/steel:

=226*SQRT(LN(1+(C6-C5)/(234.5+C5)))

=148*SQRT(LN(1+(C6-C5)/(228+C5)))

=78*SQRT(LN(1+(C6-C5)/(202+C5)))

Assuming your start temperature is located in cell C5 and your stop temperature in cell C6 (both deg C)

pc1966 · Feb 3, 2021

For example, typical PVC has start 70 and stop 160 (deg C) for the adiabatic change. The above equations (if set for 1 significant digit) should give you: