Copyright Goodheart-Willcox Co., Inc.
Continuity between a properly grounded outlet box using
either cable or conduit and the grounding circuit of the receptacle
should be established by using a bonding jumper between the
box and the grounding screw of the receptacle. Look again at
Figure 10-15.
The jumper is usually not required if the construction and
installation of the receptacle is such that direct metal-to-metal contact
is established between the receptacle (of approved type) and the box
in which it is installed.
Ground-Fault Circuit Interrupters
Ground-fault circuit interrupters are commonly referred to as
GFCIs. The GFCIs are connected between the power line and the tool
or appliance being used. These devices sense ground (leakage)
currents. When the currents entering and leaving the circuit are not
identical, they automatically turn off the primary power within 25 to
30 milliseconds.
GFCIs should be installed wherever moisture is present or there
is any chance that a tool or appliance being used might contact a
grounded metal surface. All 120-volt single-phase 15- and 20-ampere
receptacle outlets installed outdoors, in bathrooms, in laundry areas,
in basements, and at kitchen counters need to have ground-fault
circuit protection.
Arc Fault Circuit Interrupters
The National Electrical Code requires that all outlets not protected
with a GFCI be protected by an arc fault circuit interrupter
(AFCI). AFCIs are designed to prevent fires by stopping the flow of
electricity when arcing is detected in the circuit. AFCIs provide
protection from faulty wiring, damaged extension cords, and defec-
tive appliances.
While there are receptacle-type GFCIs, there are no receptacle-
type AFCIs. The AFCI breaker must be located in the electrical panel.
This provides protection for the entire circuit.
Unit 10 Basic Wiring Systems 77