Cornelius Cretu
Hi Colin, Ib = P/V = 10800W / 230V = 46.95 Amp Ib - designed current P- power of the shower V - nominal voltage The current carrying capacity for a 10mm2 3 core flat cable (conductor operating temperature 70 C, ambient temperature 30C, run above plasterboard ceiling, covered by thermal insulation not exceeding 100mm) is 45 Amp. Without taking into account all the other correction factors, you have to run a 16mm2 cable which in the same conditions has a current carrying capacity of 57Amp. To see what's the voltage drop for this length of cable: Vd= mV/Amp/m x Ib x length / 1000 mv/Amp/m represent the voltage drop per amp per meter which is basically the resistance of the cable and is 2.8mv/amp/m Vd = 2.8 x 46.95 Amp x 16m / 1000 Vd = 2.1V which is within range. (5% for power circuits off 230V) In conclusion, a 16mm2 3 core flat cable would be the best choice for that shower in terms of size and price. An armored cable of the same size can be used too. Hope this helps, Cornelius Cretu
