Copyright Goodheart-Willcox Co., Inc.
Protective Grounding System
The modern house wiring system has an equipment grounding
system. This system is independent of the grounded neutral (white
wire). It provides an unbroken electrical path from a tool or appliance,
through the receptacle, to the branch circuit, through the entrance panel,
and from there to ground. An electrical short in a tool or appliance will
pass harmlessly to ground instead of causing an electrical shock.
A grounded receptacle has the usual two slots plus a third U-shaped
slot that is grounded to the rest of the circuit. See Figure 10-15. The third
prong of an electrical plug is connected to the metal case of the tool or
appliance by a third wire.
In the receptacle, the third opening is electrically connected to a
third terminal. The terminal screw is color-coded green.
The grounding system provides for continuity from outlet box to
ground by:
1. Using metal boxes and metallic conduit as conductors.
2. Using metal boxes and a third (base) grounding wire in
electrical cable. Connecting the third wire to the metal outlet
box gives continuity. On a conduit system the conduit itself
provides the ground if it runs back to the entrance panel.
76 House Wiring Simplified
Green
bonding
jumper
Green
bonding
jumper
Conduit
Cable
Connecting grounding wire to box.