I make this post about every year or so. I have 23 programs that run in a web page. They require MS Internet Explorer version 5.0, 6.0 or
7.0. The programs took about a year to write and cover NEC Table
310.16, Voltage Drop, Cable Pulling Tension, NEC Ranges, and more. There is also a link to the Neher McGrath paper (PDF) and related papers and a link to some classic grounding diagrams. They are at
formatting link
formatting link