How to determine a branch circuit?

A branch circuit is a portion of an electrical wiring system that extends from the final overcurrent protection device, such as a circuit breaker in a main panel, to the outlets, switches, or devices it powers.

To determine a branch circuit, you start by identifying its origin at the main panel, where the circuit breaker connects to the hot bus bars (L1 and L2 in the diagram) and the neutral bus (N), along with a ground (G) for safety.

The diagram illustrates a 240V, single-phase supply from the utility, feeding into the main panel, where the branch circuit begins.

From the breaker, the circuit extends through wiring—typically consisting of a hot wire (black or red), a neutral wire (white), and a ground wire (green or bare)—to various loads like a light fixture controlled by a switch and an outlet.

The path from the breaker to the first device is the branch circuit's starting point, and it ends where the load is connected, such as the light or outlet. In the image, the branch circuit is shown powering a light fixture through a switch and an outlet, demonstrating how the circuit branches out to serve multiple devices while being protected by a single breaker, ensuring safe distribution of electricity within a building.