How can I calculate the cable size for given load current? With out using any tables or charts.

Hi , Im mike, 29 years old, I live in Mauritius. I would like to know how to size my eathing wire since my supply wire is 6 mm2. Thanks

I am upgrading from a 100 to 200 amp service and will be upgrading my sec cable to a 2/0 or 3/0 thhn. Ive been told that nec permits downsizing of the neutral wire. Is this true and if so what size is acceptable?

I am replacing an overhead feeder & panel to my garage. The old overheads were 12ga strung between porcelain insulators that the insulation had completely fallen off from. I am replacing the fuse box with my old 100 amp service panel from the house. I am trying to find wire marked sunlight...

If I have a steam room shower, that is run off water, but I need an electric cable to feed the steamer and the light inside, the shower is 3KW and in an en suite bathroom. What size cable and what size fuse would I need??