CHAPTER 2 OCCUPANT PROTECTION Flashcards
___________ occurs when a small amount of electrical current flows through the heart for 1-3 seconds.
Electrocution
• resemble regular receptacles, but they’re so much more.
• provide a permanent solution to CHILDHOOD SHOCK caused by tampering with electrical outlets.
• feature built-in safety shutters that block FOREIGN from being inserted into the receptacle.
Tamper-Resistant Receptacles
• Unintentional flow of electrical current between a power source, such as ungrounded (hot) wire, and a grounded surface.
• Occurs when electrical current leaks or escapes to the ground.
ground fault interruption
Water leaking into an electrical box can cause a ground fault since water is a conductor of electricity.
Common Causes of Ground Faults
Worn hot wires or hot wires that are not completely seated into their terminals may contact ground wires or grounding devices or boxes.
Common Causes of Ground Faults
Without proper insulation, power tools or appliances can cause a ground fault if faulty wiring causes current to flow directly to the ground.
Common Causes of Ground Faults
Hot and neutral wires touch
Short Circuit
Blows fuse and circuit
-Causes sparks or smoke
Short circuit
Hot wires touches ground
-Blows fuses or circuit breaker
-GFCI outlets can send alert
Ground Fault
• an electrical device that detects an EXTREMELY LOW LEAK (6 mA) of electrical current (called ground faults) and acts quickly to shut off the power.
• It works by comparing the amount of current going to and returning from equipment along the circuit conductors.
Ground Fault Circuit Interrupter (GFCI)
• designed to protect the user of an electrical appliance much like a circuit breaker or fuse safeguards the wiring in an electrical system.
GFCI
• generally used in place of STANDARD DUPLEX CONVENIENCE OUTLETS that are commonly found throughout the house.
• The most often used “receptacle type” GFCI, similar to a common wall outlet, is the type with which most consumers are familiar.
RECEPTACLE OUTLET TYPE
• can be installed in the panelboard in buildings equipped with circuit breakers.
• gives protection to the entire branch circuit.
• By providing overcurrent protection as a circuit breaker and serving to provide GFCI protection, the GFCI circuit breaker serves a dual purpose:
it will interrupt power in the event of a ground fault – it will trip when a short circuit or a power overload occurs.
it will trip when a short circuit or a power overload occurs
CIRCUIT BREAKER TYPE
• frequently used in construction and outdoor settings with electric tools, mowers, trimmers, and similar devices.
• It should not be used as a permanent alternative to a regular GFCI.
• They are intended to be used when you must bring power from an UNPROTECTED OUTLET INTO A HAZARDOUS SITUATION
PORTABLE TYPE (GFCI)
• unintentional electrical discharge characterized by the LOW and ERRATIC current.
• _______ generates high-intensity heat and expels burning particles, which can easily ignite/ combustible materials. • caused by loose, damaged, or corroded wires and terminals.
• Current residential breakers only detect and react to power overloads, not _____________
ARC FAULT
• Occur across the break of a single conductor
• For example, in the case of an electrical wire cut by a nail or screw used to mount a wall hanging.
Series Arcing Faults ( types of arc faults)
• Result from direct contact of TWO WIRES OF OPPOSITE POLARITY
• Frayed/ruptured appliances or extension cords • staples or other fasteners that pierce or pinch insulation on construction wire and appliance or extension cords
• Cracked wire or cord insulation caused by age, heat, corrosion, or bending stress
PARALLEL ARCING FAULTS
• Arcs between a SINGLE CONDUCTOR and GROUND, such as:
• wire or cords that touch vibrating metal;
• in appliances, wall plugs, or switches where the internal wires are not installed correctly
• where connections became loose
GROUND ARCING FAULTS
provides enhanced protection from fires resulting from arc faults.
AFCI
• It uses electronics to recognize an arc fault and interrupts the circuit when the fault occurs.
AFCI
• detects low-level arc faults that traditional overcurrent protective devices (fuses and circuit breakers) cannot see.
AFCI
A branch/feeder AFCI breaker with protection provided to branch-circuit wiring in the form of a circuit breaker.
circuit breaker type
An OUTLET AFCI for protecting connected cord sets and power supply cords in the form of an outlet receptacle.
convenience type
_________ AFCI for protecting connected cord sets and power-supply cords that can be moved from outlet to outlet.
portable type
______________ are for protecting the power-supply cord connected to it
cord-mounted type
• The tendency of GFCIs and AFCIs to trip frequently because both of them are extremely sensitive. This can be caused by:
• Appliances that are beginning to fail – should be repaired or replaced.
• ___________ – for this reason, it is not a recommended practice to connect essential equipment and appliances that contain perishable products into an outlet with GFCI or AFCI protection.
Nuisance tripping
silent, invisible magnetic fields produced any time electricity runs through a wire, an appliance, or piece of equipment.
Extremely low - frequency electromagnetic fields
Produced by high levels of EMF.
• Are visible screen jitter in video displays,
• humming in telephone/audio equipment and data errors.
• Higher levels of EMF can cause computer monitor interference and raise potential health concerns • In the United States, EMF is measured in units called __________ (mG).
• In most of the world and in scientific community, it is measured in ____________ (μT).
1 μT = _________
EMI ( electromagnetic interference), milligauss, microtesla, 10 mG
Instrument used in measuring EMF radiation levels from fans, electrical appliances, wiring, and power lines.
• The most significant exposure to EMFs is from household appliances or business equipment, not power lines in the US.
ELF (extremely low-frequency) meter
• Shielding of magnetic fields to reduce EMF levels include:
passive and active shielding
By using a conductive sheet material in front of the appliance or equipment
Passive shielding
uses a system that senses the existence of a magnetic field in the building area to be shielded.
active shielding
