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Most homes have two incoming voltages: 120 volts for lighting and
appliance circuits and 240 volts for larger air conditioning and electric dryer
circuits.
When an appliance switch is turned on, electrical current flows
through the wire, completing the electrical "circuit" and causing the
appliance to operate. The amount of flowing current is called
"amperage." Most lighting circuits in the home are 15 amp circuits.
Most electric dryers and air conditioners require larger 30 amp circuits.
The amount of electrical power needed to make an appliance operate
is called "wattage" and is a function of the amount of current flowing
through the wire (amperage), and the pressure in the system (voltage).
Mathematically speaking, volts x amps = watts. So, if we have a 120
volt system and a 15 amp current, we can flow a maximum of 120 x 15 or 1,800
watts on a typical lighting or appliance circuit. When too many lights or
appliances are attached to the electrical system, it will overload and overheat.
This can cause the wire insulation to melt and ignite, resulting in an
electrical fire. The amount of electrical current flowing through wire is
affected by resistance. This is known as "ohms." Resistance causes
increased heat in the wire. Heat is the byproduct that makes some appliances
work, such as an iron, toaster, stove or furnace. Large current faces high
resistance when moving through a small wire. This generates lots of heat. That's
how an incandescent light bulb works. Resistance through the light filament
causes it to heat up which gives off a bright light. Electrical resistance also
is affected by the length of a wire. Operating an electrical hedge clipper with
a long extension cord increases resistance and might cause the cord to overheat,
melt or ignite. The same occurs if too many strands of Christmas lights are
connected together.
The size of electrical wire is dependent upon the amount of current
required to operate a particular appliance. Wiring to the air conditioner,
electric stove and electric dryer is much larger to handle the increased voltage
(240) volts) and amperage (30 amps). Wiring is covered with a protective
material called "insulation."
Electrical circuits in homes are designed so that all components
are compatible. The size of the wire, outlets and circuit breakers are designed
for an anticipated electrical load. A circuit is said to be overloaded when too
much current flows causing heat build up or wiring to break down. When two bare
wires touch, a "short circuit" is said to occur. This can lead to
sparks and fire. Deteriorated insulation is one of the most frequent causes of
short circuits.
A "circuit breaker" or "fuse" is a safety
device designed to prevent accidental overloading of electrical circuits. They
are set at a specific amperage. When that amperage is exceeded, it trips and
shuts off the flow of electricity, stopping the circuit from continued
overheating. When a fuse or circuit breaker trips, it is important to find the
cause and correct it. Often, people will just reset the breaker or put in larger
fuse. NEVER USE OVERSIZED FUSES ON CIRCUIT BREAKERS. NEVER SUBSTITUTE A PENNY OR
FOIL-WRAPPED FUSE. This could cause a fire!
When a house is under construction, city inspectors visit to make
sure the electrical system is in compliance with the City Building Code and the
National Electrical Code. Only licensed electricians are permitted to install
electrical systems. During home remodeling, when electrical circuits are added
or changed, make sure to use a licensed electrician whose work complies with the
electrical code. Add enough outlets in every room to avoid using multiple plugs
or extension cords. Use a ground fault interrupter (G.F.I.) on circuits in the
bathroom, or outdoors where water or moisture is present. G.F.I. is a type of
very sensitive circuit breaker and is required by the Phoenix Construction Code.
When choosing an electrical appliance, be sure it is approved by a
safety-testing laboratory. This insures that it has been constructed in
accordance with nationally-accepted electrical standards and has been evaluated
for safety. Use the appliance only according to manufacturer's specific
instructions.
If you touch an electrical appliance, wall switch or electrical
cord while you are wet or standing in water, it will increase the chance of
electrical shock.
When using an extension cord, be sure it is designed to carry the
intended load. Most cannot carry as much current as permanent wiring and tend to
overheat. Do not use an extension cord in place of permanent wiring, especially
if a tripping hazard exists or where there is high physical abuse, such as under
a carpet. Keep electrical cords away from infants and toddlers and use
tamperproof inserts on wall outlets to prevent them from sticking objects into
the outlets. The cord must be protected from damage. Do not run it around
objects or hang on a nail. Inspect it periodically for worn insulation and
overall condition.
The potential for electrical shock or fire from an electrical
appliance is very real, especially when safety recommendations are not followed.
Before buying an appliance, look for the label of a recognized
testing laboratory such as Underwriters Laboratory or Factory Mutual.
Keep space heaters, stoves, irons and other heat-producing
appliances away from furniture, curtains, bedding or towels. Also, give
televisions, stereos and computers plenty of air-space so they won't overheat.
Never use an appliance with a damaged cord, and be sure to use
three-pronged electrical devices in three-pronged outlets. These outlets may not
be available in older homes, so use a three-pronged adapter, and screw the tab
onto the grounded outlet box cover. Never cut off or bend the grounding pin of
the plug. If you have a polarized plug (with one side wider than the other),
never file it down or try to make it reversible.
Keep electrical cords out of the path of traffic. If you put cords
under carpets or rugs, wires can be damaged and might result in fire.
An electrical cord should never be wrapped around an appliance
until the appliance has cooled. Because hair care equipment is often used in
bathrooms near sinks and bathtubs, it is extremely important to be especially
careful that the appliances do not come in contact with water. If one drops into
water, do not touch it until you have pulled the wall plug.
Protect young children by putting plastic inserts in receptacle
outlets not in use to keep them from putting anything into outlets.
Never put a kitchen knife or other metal object in a toaster to
remove stuck bread or bagels unless it is unplugged and cooled. Install
television and radio antennas where they cannot fall across power lines. Use
caution when operating a tree-pruning device or using a metal ladder around
power lines.
Inspect appliances regularly to make sure they operate properly. If an appliance smells funny when in use, makes unusual sounds or the cord feels warm to touch, repair or replace the unit. Don't repair it yourself unless you are qualified. Keep appliances in a cool, dry place to prevent rusting.
Electrical Emergencies
When an electrical emergency occurs, there are several survival
actions that can be taken. You should know how to trip the main circuit breaker
at the electrical panel to turn off all power to the house.
If an appliance smells funny or operates improperly, pull the plug
if it can be done safely. If arcing, burning or smoking from an appliance
occurs, turn off the power at the circuit breaker and CALL THE FIRE DEPARTMENT.
Winds accompanying thunderstorms may knock down power lines or
utility poles. Keep people away from the area, and call the fire department. If
power lines come in contact with a vehicle, do not touch it or the vehicle. If
people are inside, tell them to stay inside. If they try to exit, they may
complete a grounded electrical circuit and be instantly killed. They must stay
inside until the power is shut by the utility company.
If a serious electrical malfunction occurs in your home, school or
workplace, it is the same as a fire. Notify others, activate the fire alarm and
exit promptly. If you are familiar with the operation of a fire extinguisher,
you can use only a "Class C" Fire Extinguisher on an electrical fire.