what is the fuse rating for a 9 kw electric shower

Hi, The size of the circuit breaker you would need for this is 40 amp which would require at least a 6mm cable run up to it. To be on the safe side though, I'd probably advise using 10mm cable to make sure that the resistance isn't too high when you start thinking about things like the length of the cable. I hope that's helpful, Rupert Rupert Johnson Electrical Solutions

40 Amp fuse would be sufficient

40A on 6mm T+E surface lipped or 10mm T+E buried cables.

This question should be posted to electrician, not bathroom fitter. 25.55555 is the fuse rate. Fit a 32amp RCB should do the job with 10mm cable connected to the unit. This MUST be installed outside the bathroom. Electricity and gas at not DIY jobs, this staff can kill you. Seek for professional installer. Tiziano