As always thanks for the reply.wwhitney wrote:I've not actually studied Article 220 in the NEC on load calculations, but I do know that almost always the optional method described in Part IV of the article (starting at 220.80) is almost always a lower number. So be sure your calculator is using the optional method. The result is still quite conservative.
Yes, I got into the whole thing about the "optional method" and low and behold the answer on the spreadsheet came out at exactly 100A. That's using the commonly available 4500W heaters, not the 3800W. The only part I'm not sure I did right was the range... it says to use the nameplate rating, which I neglected to check. This is your garden variety electric range which apparently has a nameplate rating around 11-12kW but for whatever reason calculations commonly peg them at 8000W. I'm not sure which number I should be using in the optional method calculation. They say these can be installed on 40A circuits, so the 8000 number makes sense.