Cornelius Cretu
Hi Alex, Ib= P/V = 750w / 230V = 3.26 Amps Ib - designed current Because the run is quite long and then you either bury the cable or clip it onto a wall or a fence, you have to take into account the derating factors, which I'm not going to do but I'll consider that the current is 5 Amps. Next step is to calculate the voltage drop. The maximum admissible voltage drop is 5% for power circuits so in our case 5% out of 230V is 11.5V Vd= mv/A/m x Ib x length / 1000 , Vd - voltage drop mV/A/m - represents the voltage drop per amp per meter and this value is 19 mohms for a 2 core 2.5mm2 armored cable. Vd = 19 x 5 Amp x 100m / 1000 Vd = 9.5 V So a 2 core plus earth 2.5mm2 armored cable should be enough for that pump. If you think you'll add more consumers in the future, go for a 4mm2 cable. Don't forget that cable has to be RCD protected at it's starting point. Enjoy! Cornelius Cretu
