A feeder is everything between the service and the last overcurrent device
Article 215 is brief because most of what governs a feeder lives in other articles. Knowing which ones is the skill.
On this page
The definition does the work
A feeder is the conductors between the service equipment, or another power source, and the final branch-circuit overcurrent device.
So the panel-to-panel run is a feeder. The transformer secondary to the first panel is a feeder. The service conductors are not.
Getting the definition right matters because it decides which article you are in, and several rules differ between feeders and branch circuits.
Where the sizing actually comes from
Article 215 gives you the minimum ampacity requirement, but the calculation feeding it comes from Article 120 and the conductor sizing comes from Article 310.
For a feeder serving motors, Article 430 supplies its own sum which supersedes the general approach.
So a feeder question is usually a load calculation question, a conductor sizing question, or a motor question wearing different clothes.
The requirements that genuinely live here
- Minimum rating and size relative to the calculated load.
- Identification of the grounded conductor and, in some cases, of the ungrounded conductors where a building has more than one nominal voltage system.
- Ground-fault protection requirements for certain feeders.
- Diagrams required in some circumstances.
The identification requirement is the one most often tested, because it applies whenever a building has more than one voltage system and people forget it exists.
Feeder versus branch circuit, on the exam
If the conductors end at an overcurrent device, they are a feeder. If they end at a load or a receptacle, they are a branch circuit.
A question that describes a run without saying which it is expects you to classify it, and the classification changes the answer.
What this page cites
- NEC 215.4 Minimum feeder rating and size.
- NEC 215.12 Identification of feeder conductors.
- NEC 120.41 The service and feeder calculation figure.
- NEC 430.24 The motor feeder sum that supersedes the general approach.