electrical safety and grounding essentials copyright © texas education agency, 2011. all rights...

Electrical Safety and Grounding Essentials

Copyright © Texas Education Agency, 2011. All rights reserved.

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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


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A Safe Working EnvironmentObserve 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


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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.


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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.


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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.


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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.


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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


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Bonding and Grounding Electrical Equipment

Grounding is connecting a electrical system to the >earth with a wire. Excess or stray current travelsthrough this wire to a grounding device deep intothe earth. Grounding prevents unwanted voltage onelectrical components. Metal plumbing is often useas a ground. When plumbing is used as a groundingconductor, it must also be connected to a groundingdevice such as a conductive rod. Rods used forgrounding must be driven at least 8 feet into theground. Bonding means joining all metal parts of the wiring >system-boxes, cabinets, enclosures, and conduit. Itensures having good, continuous metallic connections throughout the grounding system


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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.


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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.


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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).


electrical safety and grounding essentials copyright © texas education agency, 2011. all rights...

Documents

electrical wiring

electrical hazards shock

electrical equipment

electrical safety

severity of electrical

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dangers of electrical