Just a quickie. Just reading the instructions for a new 6kW water heater and it says to calculate cable section as 5A/mm2 for runs under 20m. The existing cable is 4mm2 but by this reckoning it's too lightweight. I thought 4mm2 cable was 30A?
Am I wrong, and therefore need to replace the existng cable with 6mm2, or is 4mm2 fine for a 6kW load?