Is derate required for 1 motor with supply and load in same pipe

[sgtsparky]

My question is I have a local motor disconnect 3phase wiring coming from the control to a local disconnect then the wiring going out to the motor same circuit. I believe in the past we did this from a gutter where the conduit to the disconnect was only 24" so no derate would be required but with a longer run is a disconnect required? I thought they 2 runs would not be additive we have done it this way for years but my apprentice asked me where it is in code and I cannot find it are we doing it wrong or is there an exception for conductors of the same circuit entering and exiting (I thought I remembered some terminology like that)

 

[drcampbell]

Each wire carrying current dissipates heat, regardless of which direction the power's going, and heat is the basis for derating.
That doesn't change when two wires are carrying equal amounts of power in opposite directions.

 

[infinity]

Since you have 6 CCC's conductors in the raceway if it's longer than 24" you must derate. {310.15(B)(3)}

 

[tom baker]

And just a reminder, you are derating from 90 deg C (if THHN) so with 6 conductors you may be OK).