Double Insulated Cable Selection

The cable must be rated for the maximum possible current on the incoming mains supply. The rating of the downstream stuff (in this case your fuseblock) is irrelevant.

thanks but im looking to understand the values on a standard refrence sheet we are provided. I am aware the max current must be accounted for and as the fuse switch is also rated for full current capacity we use its size as a refrence .I am required to ensure the double insulated cable going from the (busbar/droppers/mains) to the fuseswitch is able to handle the same as the fuseswitch, and as you said the fuses render anything downstream of the fuseswitch irrelevant.

to be more clear im looking for the calculation used to obtain the following data taken from are standard reference sheet.

(fuseswitch direct to riser,double insulated cable) .

Up to 20A = 6mm2

Up to 32A = 10mm2

Up to 63A = 16mm2

Up to 100A = 35mm2

Up to 160A = 2 x 25mm2

Up to 200A = 2 x 35mm2

thanks for your help

Refer cable manufacturer's literature