Re: question from student
Yes and no.
While 250.122(C) explains how to size the grounding conductor when used for multiple circuits.
250.122(C) Multiple Circuits. Where a single equipment grounding conductor is run with multiple circuits in the same raceway or cable, it shall be sized for the largest overcurrent device protecting conductors in the raceway or cable.
That is only allowed per raceway as 300.3(B) requires all conductors (including the grounding conductor) of a circuit to be in the same raceway.
If you have 3 raceways between the load center and the junction box each containing multiple circuits you will only be required to run one grounding conductor in each raceway sized to the largest circuit in that raceway.