im sure this question will have been asked many time before but i cannot find the answer on here.
i am currently working on a project, and when calculating a cable size through amtech for a motor cable, it is coming out at a very large cable size purely down to earth loop impedance.
in the past i have simply used the "add RCD" button and enabled earth fault protection through the intelligent starter.
however, this client does not want to do this.
the circuit in question has a power to the motor, and a control cable to the local control station (both armored cables), these are then equipotentially bonded, also bonded to the pump base, the pump base is locally bonded to a local earth bar which is connected to multiple other earth bars and multiple earth pots, these earth bars also have other pumps connected to them, which go back to the MCC.
as you can appreciate, the earth loop impedance on this circuit is going to be minimal as there is so many earth paths, however, amtech (As far as im aware) cannot compute this and just looks at the one cable.
i am happy to write in my report something along the lines of "calculation fails due to Earth Loop Impedance, however considering XYZ, the cable is considered sufficient and shall be tested on site prior to energisation to ensure that it meets all criteria from BS7671".
however, i am wondering if 1. any body knows a way around this in amtech, 2. is there a statement in any standards or guides that details this i can reference and 3, any issues that anybody can see.
