AS/NZS 3000:2007 Section C3 (Protective Device Sizing for Cables) Extract

Sections C3 provide "simplified" selections of protective device ratings for a given cable size in a given range of situations, and calculation of voltage drop.

As discussed above, all cables installed in domestic housing should be treated as "bulk thermal insulation - partially surrounded".

The ratings here are more conservative than those in AS/NZS3008, in the sense that the protective device rating is the limiting factor on cable current capacity rather than the cable itself.

The voltage drop may be slightly over estimated. This is not a problem if the simplified calculation is below any target voltage drop. Bear in mind that in many cases a calculated result that is slightly over the allowed design value is ok if the full conditions of diversity and maximum demand are taken into account.