Table one of Ch 9 says if we have one conductor we can fill the conduit to 53%, 2 conductor to 31% and more than 2 conductors the conduit can be filled to 40%.
My question is why 31% for 2 conductors and 40% for more than 2 conductors? what is rational behind it.
An IAEI instructor once told me it is because of the heat dissipation. But he did not explain in details why?