Grounding

To simplify the earlier discussion of circuits only two conductors were used, hot and neutral. To meet current wiring codes a complete wiring system uses at least three conductors; hot, neutral, and ground. The ground conductor (equipment ground) is attached to the case of metal-cased tools and it must provide a complete low resistance circuit to the earth, Figure 26.10.

This is usually accomplished by attaching it to the grounding bar in the service entrance panel. If a short occurs between the electrical components and the case or frame, the low-resistance ground circuit will permit a current flow greater than the circuit over-current protection (fuse or circuit breaker), causing the circuit to open. If a short occurs and the ground circuit is not continuous from the case or frame of the tool to the earth, the operator's body or body parts may complete the circuit resulting in a potentially fatal electric shock.

Metal case tool

Ground connection to case

FIGURE 26.10. Case of equipment ground.

Ground connection to case

FIGURE 26.10. Case of equipment ground.

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