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Electrical Safety and Grounding Essentials Copyright © Texas Education Agency, 2011. All rights reserved.
2 Objectives Working safely in a construction environment. Electrical Hazards in the workplace. Conditions that affect the severity of electrical shock Helping a shock Victim Grounding Theory Equipment Grounding System Grounding Bonding GFCIs Copyright © Texas Education Agency, 2011. All rights reserved.
3 A Safe Working Environment Observe the general safety practices in doing all electrical work Avoid damp working areas. Never handle electrical equipment with wet hands or while standing in a wet or damp place. Protect each circuit. Be certain that each circuit is protected with either a circuit breaker or a fuse of proper amperage. Ground each circuit properly. Each circuit must have a ground (neutral) wire and a grounding wire to be properly grounded Copyright © Texas Education Agency, 2011. All rights reserved.
4 Avoid Electrical Hazards in the work place Install all electrical wiring according to the National Electrical Code. Open the circuit before touching any point on the circuit. Do not touch bare wires with hands or tools while the circuit is closed. Do not touch wires together to see if they are hot. Do not touch switches or fixtures with wet hands or while standing on wet ground. Do not connect a new circuit to the breaker box until all the wiring is completed. Do not install fuses or breakers with an amperage larger than recommended, or they will not protect the circuit from overheating Do not overload a circuit with too many fixtures and outlets. Copyright © Texas Education Agency, 2011. All rights reserved.
5 Electrical Hazards Shock and fire are hazards associated with electric current. Shock refers to the body's reaction to the passing of electrical current through it. Shock occurs from a fall in blood pressure resulting in a decrease of blood supply, and therefore oxygen, to the brain. The increasing levels of electrical shock caused by increasing amperage makes it clear that voltage is not the killer, rather amperage is. Fire may occur when electrical conductors overheat or when a spark is produced when an electric current jumps an air gap between conductors. Copyright © Texas Education Agency, 2011. All rights reserved.
6 The Dangers of Electrical Shock The severity of injury from electrical shock depend on the amount of electrical current and the length of time the current passes through the body. Copyright © Texas Education Agency, 2011. All rights reserved.
7 Helping a Shock Victim Shutoff the power immediately If you can not cut off the power, the victim should be removed from contact with the energized circuit. Do not touch the victim if he or she is in contact with the energized circuit. Use a dry board, rope, leather belt, coat, overalls, or some other nonconductive material. Call local emergency service (911) and give CPR until help arrives. Copyright © Texas Education Agency, 2011. All rights reserved.
8 Grounding Circuits and Equipment The most important element in wiring safety is grounding. Grounding refers to the connection of all parts of a wiring installation to ground or to other systems that are well grounded. Grounding protects by limiting the possibility of damage to electrical equipment and conductors and be preventing shock to persons contacting electrical equipment. The deliberate and purposeful connecting of the system and the earth provides for the safety and protection of: 1. Persons installing or testing the system. 2. The electrical system itself. 3. Persons using power tools, appliances, or other devices Copyright © Texas Education Agency, 2011. All rights reserved.
9 Bonding and Grounding Electrical Equipment Grounding is connecting a electrical system to the > earth with a wire. Excess or stray current travels through this wire to a grounding device deep into the earth. Grounding prevents unwanted voltage on electrical components. Metal plumbing is often use as a ground. When plumbing is used as a grounding conductor, it must also be connected to a grounding device such as a conductive rod. Rods used for grounding must be driven at least 8 feet into the ground. Bonding means joining all metal parts of the wiring > system-boxes, cabinets, enclosures, and conduit. It ensures having good, continuous metallic connections throughout the grounding system Copyright © Texas Education Agency, 2011. All rights reserved.
10 A Ground Fault Circuit Interrupter (GFCI) is a fast- acting switch that detects any difference in current between two circuit conductors. If either conductor come in contact-either directly or through part of your body-with a ground (a situation known as a ground fault), the GFCI open the circuit in a fraction of a second. Copyright © Texas Education Agency, 2011. All rights reserved.
11 If a current as small as 4 to 6mA does not pass through both wires properly, but instead leaks to the ground, the GFCI is tripped. The current is shut off. Copyright © Texas Education Agency, 2011. All rights reserved.
12 Summary To ensure a safe working environment is to recognize the hazards around you. Next is to identify possible hazard and evaluate the risk of injury. Once electrical hazards has been recognize and evaluated, these hazards are controlled in two ways: 1. create a safe working environment and, 2.use safe work practices. The danger from electrical shock depends on : the amount of the shocking current through the body, the duration on the shocking current through the body, and the path of the shocking current through the body. All electrical equipment and systems must be grounded to protect persons and electrical equipment. To assure a continuous, reliable electrical path to ground, a bonding jumper wire is used to connect all metal components. GFCIs are use to protect people in damp locations (bathroom, garage, and kitchens within six feet of the sink etc). Copyright © Texas Education Agency, 2011. All rights reserved.
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