I am going to an electricians course to augment my field experience with theory and "book learning". We are currently using "Stallcup's Journeyman Electricians Study Guide based on the 2202 natioal electrical code"
In chapter 10 there are several examples for doing comercial load calculations and in Appendix A there are several blank calculation sheets for residential and commercial.
The example on page 10-19 (figure 10-20) shows "Calculating largest motor load" (halfway down the second column) as being 9540VA x 25%.
It gives NEC references of 220.14 and 430.24. NEC 220.14 basically refers you to 430.24. The way I read 430.24 is that I should use the motor with the largest full load current and multiply that by 125% and then add the sum of full load current rating for any other motors that may be on that circuit.
My questions are:
Am I reading this properly, and if so, where does the 25% figure come from in the examples ?
If I am not reading this properly, could some one give me a simple (I'm a retired Marine - grin) explanation of what I should be understanding, and again, where does the 25% in the example come from?
Thanks so much.