I'm trying to understand the cable OCPD relationship when it comes to derating the ampacity and therefore choosing the proper wire size and OCPD. In 310 there is a lot of jumping between columns i.e. 90 degree C to 75 degree to match the wire with the breaker. I understand the math but was hoping that someone could help with a simple "down and dirty" system to get through the derating equations. Thank you.