As Don notes, no single conductor can be in compliance with both definitions... concurrently.
OK, what about the wiring configuration jap proposed in post 19?
60A OCPD
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60A conductors A
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J-Box -- 60A conductors B -- 20A OCPD -- 20A conductors C -- 20A load
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60A conductors D
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60A load
There are no taps here. To obviate any load calculation issues, let's say that the 20A and 60A loads are non-coincident.
Those 60A conductors A meet both NEC definitions for a feeder and a branch circuit:
2011 NEC said:
Branch Circuit. The circuit conductors between the final overcurrent device protecting the circuit and the outlet(s).
Conductors A are between the 60A OCPD and the 60A load, the 60A OCPD is the final OCPD for the outlet at the 60A load, so Conductors A are branch circuit conductors.
2011 NEC said:
Feeder. All circuit conductors between the service equipment, the source of a separately derived system, or other power supply source and the final branch-circuit overcurrent device.
Conductors A are between the 60A OCPD and the 20A OCPD, and the 20A OCPD is the final OCPD for the 20A load. So Conductors A are between the power supply source and the final branch-circuit OCPD, and Conductors A are a feeder.
Please explain how this installation is not NEC-compliant, or how I've misread the definitions above.
Thanks,
Wayne
P.S. As to the OP, conductors B above are definitely a feeder. So regardless of what you call conductors A, you can apply the feeder tap rules to conductors B, and downsize them to 20A conductors if you comply with the feeder tap rules.