145
Copyright Goodheart-Willcox Co., Inc.
Technical Terms
Objectives
After completing this chapter, you will be able to:
Identify the feeder and branch circuit portions of a
distribution system.
Describe the various types of branch circuits.
Define the functions of a feeder and the functions of
branch-circuit conductors.
Calculate lighting and receptacle loads using Code
requirements.
Size branch circuits in accordance with the Code.
Determine branch circuit overcurrent protection
required by the Code.
Use the Code to size feeder conductors.
In an electrical system, power must be transferred
from the service equipment to the lights, machines, and
outlets. Regardless of the wiring methods used, the
conductors carrying the power fall into one of two cate-
gories: feeders or branch-circuit conductors. This chapter
will explore the characteristics of these two conductor
types.
Definitions
Several definitions are essential to understanding
branch circuits and feeders. The following items are illus-
trated in Figure 12-1:
• Service conductors—These conductors extend
from the power company terminals to the main
service disconnect.
• Feeder—A conductor that originates at the main
distribution or main disconnect device and termi-
nates at another distribution center, panelboard,
or load center.
• Subfeeders—These conductors originate at distri-
bution centers other than the main distribution
center and extend to panelboards, load centers, and
disconnect switches that supply branch circuits.
• Panelboard—This can be a single panel or
multiple panels containing switches, fuses, and
circuit breakers for switching, controlling, and
protecting circuits.
• Branch circuits—The portion of the wiring
system extending past the final overcurrent
device. These circuits usually originate at a panel
and transfer power to load devices.
Branch Circuits
Any circuit that extends beyond the final overcurrent
protective device is called a branch circuit. This includes
circuits servicing single motors (individual) and circuits
serving many lights and receptacles (multiwire). Branch
circuits are usually low current (30 amps or less), but can
also supply high currents.
A basic branch circuit is made up of conductors
extending from the final overcurrent protective device to
the load. Some branch circuits originate at safety switches
(disconnects), but most originate at a panelboard. The
following are several branch circuit classifications
(Figure 12-2):
• Individual branch circuit—A branch circuit
that supplies a single load.
• Multioutlet branch circuit—A branch circuit
with multiple loads.
• General purpose branch circuit—A multi-
outlet branch circuit that supplies multiple outlets
for appliances and lighting.
Branch circuit
Continuous load
Feeders
General lighting load
Show-window lighting
load
Track lighting
Branch
Circuits and
Feeders
CHAPTER
12