Specifications

10
Residential Applications
Power, generated at a power plant and stepped up to a high
transmission voltage, is brought to a local substation. Here, it is
stepped down to a lower distribution voltage. When it reaches
its final destination at a residential customer, it is stepped
down to 240 volts. Only single-phase power is used in a typical
residential application.
Power Supply The most common supply system used in U.S. residential
applications today is a single-phase, three-wire supply
system. In this system, the voltage between either hot wire and
neutral is 120 volts and the voltage between the two hot wires
is 240 volts. The 120 volt supply is used for general-purpose
receptacles and lighting. The 240 volt supply is used for heating,
cooling, cooking, and other high-demand loads.
Step-down Transformer
Hot Wire
Hot Wire
Distribution Voltage
120 Volts
120 Volts
Neutral
240 Volts
Service Entrance Power, purchased from a utility company, enters the house
through a metering device and is applied to a load center. This
is the service entrance. Residential service can come from
an overhead utility transformer or from a lateral service run
underground.
Load Center
Meter
Transformer
Lateral ServiceOverhead Service
Load Center
Meter
Transformer