Transcript Bonding and Grounding Electrical Equipment Grounding

Electrical Safety and Grounding
Essentials
Copyright © Texas Education Agency, 2011. All rights reserved.
Objectives
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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
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Equipment Grounding
System Grounding
Bonding
GFCIs
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A Safe Working Environment
Observe the general safety practices in doing all electrical work
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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
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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
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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.
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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
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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
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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.
Copyright © Texas Education Agency, 2011. All rights reserved.
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 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
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A Ground Fault Circuit Interrupter (GFCI) is a fastacting 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
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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).
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