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S A F E T Y M O D E L S TAG E 1 — r E C O G N I Z I N G H A Z A r D S

If you touch a defective live component that is not grounded, you will be shocked.

device that is not grounded (or grounded improperly), you will be shocked. You need to recognize that an improperly grounded elec- trical system is a hazard.

Electrical systems are often grounded to metal water pipes that serve as a continuous path to ground. If plumbing is used as a path to ground for fault current, all pipes must be made of conductive material (a type of metal). Many electrocutions and fires occur because (during renova- tion or repair) parts of metal plumbing are replaced with plastic pipe, which does not conduct electricity. In these cases, the path to ground is interrupted by nonconductive material.

GFCI—ground fault circuit interrupter—a device that detects current leakage from a circuit to ground and shuts the current off

leakage current—current that does not return through the intended path but instead "leaks” to ground

ground fault—a loss of current from a circuit to a ground connection

A ground fault circuit interrupter, or GFCI, is an inexpensive life- saver. GFCIs detect any difference in current between the two circuit wires (the black wires and white wires). This difference in current could happen when electrical equipment is not working correctly, causing leakage cur- rent. If leakage current (a ground fault) is detected in a GFCI-protected circuit, the GFCI switches off the current in the circuit, protecting you from a dangerous shock. GFCIs are set at about 5 mA and are designed to protect workers from electrocution. GFCIs are able to detect the loss of current resulting from leakage through a person who is beginning to be shocked. If this situation occurs, the GFCI switches off the current in the circuit. GFCIs are different from circuit breakers because they detect leakage currents rather than over- loads. GFCI receptacle.

Circuits with missing, damaged, or improperly wired GFCIs may allow you to be shocked. You need to recognize that a circuit improperly protected by a GFCI is a hazard.

Overload hazards

overload—too much current in a circuit

An overload can lead to a fire or electrical shock.

Overloads in an electrical system are hazardous because they can produce heat or arcing. Wires and other compo- nents in an electrical system or circuit have a maximum amount of current they can carry safely. If too many devic- es are plugged into a circuit, the electri- cal current will heat the wires to a very high temperature. If any one tool uses too much current, the wires will heat up.

Overloads are a major cause of fires.

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Section 5

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