Don,
You asked me what fill rules was I talking about?! None. You are talking from the Code's viewpoint, I am reasoning why the Code is not logical or consistent, or why their rules defie common sense due to the historical development of the document. I am only trying to present a scenario how it could be reworked in a conscise fashion.
Simply,
- Deal with fill first and anchor it to the conduit,(eg. fill is determined by the sum of crossectional area of the conductors, regardless of their insulation thickness. I think that the % of available fill area should be consistent, not dependent on the # of conductors)
- deal with fittings second, minimum fill is equivalent to the connecting conduit,
- Increase fitting size when:
- terminations or
- directional changes required.
Next step would be ampacity. based on the current desity and thermal dissipation ability of the raceway profile and ambient temperature. We have new energy efficiency rules, yet the motor table did not change. Size the cables and overloads to the nameplate!
All these can be built into a small handheld calculator along with other code related formulas and tables on a replaceable chip, so it can be replaced as the Code changes. It would allow the electricians to perform what is called today 'engineering calculations' to use the optimum size equipment ALL the times.
This can revolutionize the trade since with the reduction of material to the optimum needed will enble the industry to spend more money as they get more for the bang, ergo more $ is left for labor. Inspectors work would be simplified and the electricians would greatly improve their installations' accuracy.