There is a similar exception for motor circuits123 said:. 4-006 When it comes to de-rating a 90 degree conductor because the circuit breaker is only 75 degree rated, the conductor has to be de-rated only at the connection to the breaker. The rest of the run is fine. I can splice the wires in a junction box 3 feet before the breaker and run larger conductor the last 3 feet. I would like to see the code allow running the conductor without de-rating, and find a way to cool the conductors before the breaker. like running larger conduit last couple of feet, or have a longer loop of the wire in the panel, before its connection.
(2) Where Table 37 requires insulation temperature ratings in excess of 75 °C, the motor supply conductors shall be not less than 1.2 m long and shall terminate in a location not less than 600 mm from any part of the motor except that for motors rated 100 hp or larger, their terminations shall be not less than 1.2 m from any part of the motor.