ELECTRICAL SAFETY DESIGN

Wiring Design and Protection - Grounded and Grounding Conductors

In a common 120-volt outlet with a portable hand tool attached, the black conductor supplies power to the motor. The grey (or white) conductor is used as a circuit grounded conductor for the motor. This ground is needed to trigger the circuit breaker, thus stopping the motor if a fault occurs. The green wire is used as the equipment grounding conductor to protect employees handling metal enclosures that may be energized by an internal fault. The graphic at the left illustrates the proper grounding for a hand tool.

An incorrectly connected circuit can cause dangerous situations. You can inspect three examples and their outcomes by clicking on the examples below.

Reversed Polarity with Circuit Ground
Reversed Polarity with Equipment Ground
Reversed Circuit and Equipment Ground

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