Branch Circuits vs Feeders

The one question to ask first

Ask this before the calculator comes out: where is the final overcurrent device protecting the load?

• After the final breaker or fuse: branch circuit.
• Before the final breaker or fuse: feeder.
• If the conductor supplies a panel that has the branch breakers, you are usually in feeder territory.
• If the conductor leaves the breaker and runs to receptacles, lighting, equipment, or one motor, you are usually in branch-circuit territory.

For the conductor-sizing rule itself, the dedicated NEC 210.19 branch-circuit guide goes deeper on continuous loads and termination limits.

Branch circuit worked example

A 277 V branch circuit feeds a 16 A continuous lighting load and a 6 A noncontinuous load. What minimum conductor ampacity does the sizing step require before selecting from the ampacity table?

1. Name the conductor: branch circuit, because it is after the final breaker and feeds the loads.
2. Use the continuous-load pattern: 125% of continuous load plus 100% of noncontinuous load.
3. Continuous portion: 16 A x 1.25 = 20 A.
4. Noncontinuous portion: 6 A.
5. Minimum ampacity before conductor selection: 20 A + 6 A = 26 A.

Feeder worked example

A feeder supplies a small panel with 24 A of continuous load and 40 A of noncontinuous load after any allowed demand factors. What is the minimum feeder ampacity before conductor selection?

1. Name the conductor: feeder, because it supplies the panel with the final branch-circuit breakers.
2. Continuous portion: 24 A x 1.25 = 30 A.
3. Noncontinuous portion: 40 A.
4. Minimum feeder ampacity before conductor selection: 30 A + 40 A = 70 A.
5. If the question is a dwelling feeder or service, check whether Article 220 demand factors or 310.12 apply before choosing the final conductor.

What changes between Article 210 and Article 215

• Article 210 owns branch-circuit requirements such as required circuits, outlet rules, and branch-circuit conductor sizing.
• Article 215 owns feeder requirements such as feeder conductor sizing, feeder overcurrent context, and feeder neutral rules.
• Article 220 often supplies the calculated load for either one.
• Article 310 still supplies ampacity and adjustment rules after you know the load.

Wrong answers the exam wants you to pick

Calling every panel conductor a branch circuit

The conductors feeding a panel are not branch circuits just because the panel has branch breakers inside it. They are feeders until those final breakers protect the load-side circuits.

Using demand factors on a simple branch circuit

Demand factors live in load calculations. A single branch circuit serving a known continuous load usually does not get a dwelling demand shortcut.

Forgetting the continuous-load step

The branch-versus-feeder decision does not remove the 125% step when the rule calls for it. Name the conductor, then size the load.

How to drill this for the exam

Draw one line on scratch paper: source, feeder, final breaker, branch circuit, load. Put the conductors from the problem on that line. Once the conductor has a name, the code article usually stops being a guessing game.