Feeder vs branch circuit: what it means for the Texas exam

Use this diagram

Copy this HTML to show the diagram with a credit link<img src="https://bondingjumper.com/charts/bondingjumper/feeder-vs-branch-circuit.svg" alt="Power running from the service conductors into a service panel, out through a feeder breaker on a feeder to a subpanel, then through a branch breaker on a branch circuit to an outlet, with a second branch circuit leaving the service panel straight to a water heater" width="100%"><p><a href="https://bondingjumper.com/guides/feeder-vs-branch-circuit?utm_source=embed&amp;utm_medium=referral&amp;utm_campaign=figure_embed&amp;utm_content=feeder-vs-branch-circuit.svg">The last breaker before the load decides the name, not the panel. by Bonding Jumper</a></p>

Find the last overcurrent device

Walk the circuit backward, from the load toward the source. The first breaker or fuse you reach protects the branch circuit, and every conductor on its load side is branch circuit wiring. Every conductor on its supply side, back to the service or the source, is feeder. A run from the service panel to a subpanel is a feeder, because more overcurrent devices sit at its far end. A run from that same service panel straight to a water heater is a branch circuit, because nothing else protects it before the load. Where the panel sits does not decide the name. The device does.

Why the name matters

• Different articles. Branch circuits are in Article 210 and feeders are in Article 215, and the terms themselves are defined in Article 100. A question that says feeder sends you to a different article from one that says branch circuit. Protection for either sits under Article 240; see overcurrent protection.
• Different sizing. A feeder carries the combined calculated load of everything downstream of it, so it is sized from a load calculation. A branch circuit is sized for the load it serves. Both have to allow for a continuous load.
• Different voltage drop budgets. The voltage drop recommendations in the NEC sit in informational notes and treat feeders and branch circuits separately, so you need to know which run you are checking. Work a run of each kind in the voltage drop calculator and compare.

A worked example

The numbers are invented. A shop's main panel has a 100 A breaker feeding a subpanel across the building. In the subpanel, a 20 A breaker feeds four receptacles on a workbench. Back in the main panel, a 30 A two-pole breaker feeds a water heater directly.

• Main panel to subpanel: feeder. It ends at a panel full of overcurrent devices.
• Subpanel 20 A breaker to the receptacles: branch circuit.
• Main panel 30 A breaker to the water heater: branch circuit, even though it starts in the main panel.

If the owner later adds a second subpanel fed from the first one, the conductors between the two subpanels are a feeder too.

Common mix-ups

• Calling every run from the main panel a feeder. A circuit from the main panel straight to a load is a branch circuit.
• Calling a big circuit a feeder because it is big. A heavy circuit to a single piece of equipment is still a branch circuit when no overcurrent device sits between its breaker and the load.
• Treating service conductors as a feeder. The conductors from the utility to the service disconnect are service conductors, which have their own article.
• Forgetting a transformer can start a feeder. The conductors leaving a transformer for the panel it supplies are feeder conductors. See separately derived system.

On the Texas journeyman exam

Under the PSI bulletin, electrical feeders carry 6 scored items across both portions, 3 on NEC Knowledge and 3 on Calculations. Branch circuits and conductors carry 14, 10 and 4, the most of any subject area. Feeder load calculations, feeder overcurrent protection, and feeder grounded conductors and grounding and bonding are listed under feeders. Study to name each run first, then pick the article and the calculation that goes with it.

Sitting a master exam on the 2023 NEC outside Texas? Start with the master electrician exam outline or take the free NEC master check.

Practice it

Every term in this set is in the electrical terms glossary.

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