All you electricians Reply #15 – May 03, 2008, 10:49:16 AM The number of phases does not matter. Yes there was a formula to figure it out many years ago. But as he told you it was too complicated for most and most of the rest were too lazy so they made a chart for all to use. Back 30 years ago when I took the test to be a electrican you had to know the formula but now I couldn't even begin to try to remember it. Quote Selected