The acronym IEC is used by a number of different organisations. The one that issues standards is called International Electrotechnical Commission. The main area is equivalent to NEMA standards, but there are also code standards, e.g. IEC 60364. There is a comparison between this standard and the NEC on the NEMA website. (108 pages) http://www.nema.org/publications/ei/jun99/iec_nec_comparison2.pdf