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Electricity
in your Home
How
does electricity get where you need it?
Electricity in your
home is not rocket surgery, but there are some basics
and some details that will help you deal with issues
on your own, know when to call an electrician, and what
to tell her or him when you call. In this introduction
to electricity in your home, we'll add enough details
about things you may already know and about house wiring
issues that affect you everyday - especially on the
days when something goes wrong.
Over
time, we will add short articles about specific electrical
topics to our website. If you would like us to answer
your questions about electricity, lighting, telephone,
or computer networking in our website's Electrical Education
section, email us at TechnologyForTheRestOfUs@onlyconnectelectricians.com.
Source
 After
the meter, the service entrance conductors continue
into your home to the circuit breaker or fuse panel
(the service panel) in your basement. The service panel
is really where the story of how electricity works in
your home begins. Behind the panel cover door or cover,
you will find a switch or a fuse at the very top that
regulates all of the electricity that comes into your
home. Below it, you will see a series of switches (circuit
breakers) or fuses that regulate each of the circuits
that run through your house.
The Main
In the service panel,
the service entrance conductors attach to "the main,"
a circuit breaker or a set of fuses that protects your
entire house. Typically sized from 60 to 200 Amperes,
the main shuts off the power to the entire house when
you are drawing more power, through every plug, lamp,
or appliance than you have available. Without the main
to protect you, your wires could get too hot, melting
their insulation and igniting nearby wood or other combustibles.
If the main keeps tripping, and this rarely happens,
it means that you don't have enough power coming into
your home.
Circuits and
Circuit Breakers
Once the power passes
through the main it is divided into individual circuits.
In the service panel, the power is divided up and runs
through circuit breakers or fuses that protect each
of the wires (circuits) that leave the panel to do something
useful. A circuit is exactly what it sounds like, a
smaller pair of insulated wires, with a ground, that
run through your home to a number of outlets, lights,
fans, or other appliances. Each circuit is protected
by a smaller circuit breaker that is usually safe for
only 15 or 20 Amperes.
There are a number
of different circuits running through your home; some
might power a string of lights or outlets, while others
may go to a single large appliance like a stove or the
heating system. When there's a problem on one circuit,
the breaker turns off the power (trips) on just
that one circuit; the rest of the house continues to
have electricity to run your lights, TV, computer, heat,
and other good things.
When Do Circuit
Breakers Trip?
It sounds like a dumb
question, but it's not. There are two ways your wiring
can get too hot and cause problems: overloads and short-circuits.
If you have an outlet
above your kitchen counter, it should be on a 20 Ampere
circuit with a 20 Ampere circuit breaker. The wires
can safely carry 1920 watts before overheating.
If you run a toaster
(often 1200 watts) and a microwave (often 1250 watts)
on that circuit at the same time without a circuit breaker,
they use 2450 watts: enough to overload the circuit,
overheat the wires, and damage the insulation. A 20-Ampere
circuit breaker on the line prevents this by slowly
warming up with the wires and then saves the day by
shutting off the power before the wires get too hot,
and preventing damage to their insulation, or the house.
It's a pain in the neck that should and can be fixed,
but in the meantime, you still have a house.
Another way a circuit
breaker can be tripped is if you accidentally drop a
kitchen knife on the toaster cord and connect the two
wires in the cord. You would have a short-circuit, and
you would probably see a spark. When a short circuit
occurs, the power goes out through one wire and then
back on the other, without ever reaching the toaster.
Unlike a toaster, the wires have very little resistance.
Suddenly, a huge electrical current flows through the
wire. If allowed to continue, it would heat the wire
and cause damage very quickly. In this situation, the
circuit breaker trips very quickly. Short circuits like
this can also occur inside a fan you have plugged in
or in the electrical boxes and cables in your walls.
Circuit breakers and
fuses are designed to prevent damage or fire from both
overloads and short-circuits.
If a particular circuit
breaker keeps tripping it probably means that you have
too many appliances or lights on that circuit. It may
be time to add a new circuit and divide the appliances
and lights between the two circuits. It rarely means
that you need to increase the power available in your
home with an expensive "service upgrade."
If you find that the
main fuses are blowing or the main circuit breaker in
the panel is tripping, you may need more power than
is available to the entire house. Then it's time to
investigate whether a service upgrade may be in order.
How
good are circuit breakers?
 With
so much depending on circuit breakers, the natural question
is, "How good are circuit breakers?" And if you have
an old fashioned fuse box, "Is it necessary to upgrade
to a panel with circuit breakers?"
Circuit breakers are
very reliable, but they are not perfect. We cannot live
safely without them, but like all electrical-mechanical
devices, circuit breakers are built in ordinary manufacturing
plants. Only a miniscule percentage of them leave the
factory defective, but all of them get old. Eventually
a few of them don't work so well.
Defective breakers
may trip when there's no problem or may fail to trip
when there is a problem, but they are typically extremely
reliable and absolutely worth using. Fuses, which are
much older technology, are less convenient because you
have to keep a supply of replacements on hand and change
them when they blow. But fuses are much simpler and
even more reliable: when there is a problem, they get
hot; the lead melts, the circuit is off. So, unless
there is something wrong with your fuse box, or the
bank with the mortgage money insists, you might not
need to replace a fuse box with circuit breakers.
A
New Circuit or More Power?
You've probably had
a circuit breaker trip at some time. Your cat gnawed
through a lamp cord, and poof (that's a technical term),
half the lights in your house went off. Everything that
went off was on the same circuit. This is one way to
understand where each circuit goes in your house, but
it is probably not the best way.
Older houses were
built for simpler times: fewer electric appliances and
very few circuits. All the lights and receptacles on
a floor were often on the same circuit. We were recently
in a house that had the basement lights and the receptacles
in the front hall, living room, and one bedroom on the
same circuit.
Even if the service
panel was upgraded to 100 or 200 Amperes, the old circuits
may have been merely reattached to the new circuit breakers.
In other words all of the plugs, lights and appliances
in the kitchen may still be on that same 20 amp circuit.
All that additional power coming into the service panel
won't do any good if you don't split it up into new
circuits. And if you add new circuits, odds are you
won't need that service upgrade.
This is the big reason
why we believe that it is often better to spend your
money on getting more circuits than getting more power
into the house.
Newer houses often
have more circuits that are divided up more sensibly.
Keeping lights and receptacles on different circuits
means that the overhead light still works when the receptacle
circuit goes off. Although it's a tedious task, it is
a good idea to make an accurate list of which lights,
receptacles, and equipment are controlled by each circuit
breaker. A good list will help you figure out what's
going on when a circuit breaker trips. And a good list
will save you money when you need to call an electrician.
You don't him or her to spend a lot of time figuring
out what is controlled by each circuit breaker.
What
is Grounding, and Why Should I Care About It?
Short circuits happen. Equipment gets old and fails.
Microwaves, vacuum cleaners, washing machines, and televisions
get old. Trucks bouncing down the street and kids running
up and down the stairs jiggle wires loose. Insulation
dries out and crumbles, allowing live wires to electrify
metal parts. Short-circuits can destroy equipment and
create dangerous situations. Grounding reduces the chances
of danger.
An example to make
the value of grounding a little clearer: Look at your
microwave; it has a 3-prong plug, with an "equipment
grounding wire." If a wire inside your microwave jiggles
loose or the insulation melts, a live wire may touch
the metal appliance case. If you now touch the metal
case and the stove or a faucet at the same time, you
can receive a bad shock.
To prevent this shock,
the grounding wire from the cord is attached to the
metal case and to the grounding terminal (the round
hole) in the wall plug. The grounding terminal in the
outlet connects to a grounding wire that goes back to
the service panel. The grounding wire provides a low-resistance
path for electricity to get back to the panel. allowing
large amounts of current to flow through the circuit
and trip the circuit breaker.
The house doesn't
burn down, and you don't touch a live metal case and
get injured. The 3-wire grounding plug and the 3-hole
grounding receptacle save the day.
On the other hand,
very few of the lamps in your house have 3-prong plugs.
Take a look around. Some appliances on your kitchen
counter do and others don't. Those with 2-prog plugs
cannot connect the live metal case to the house wiring:
in this situation, replacing a 2-hole receptacle with
a 3-hole grounding outlet offers no additional protection.
What are those
buttons on my bathroom receptacle?
In some situations,
grounding plugs and receptacles do not provide the edge
of safety you need. The solution is a ground fault receptacle
(Ground Fault Circuit Interrupter-GFCI) that
provides extra and faster protection. The buttons are
for testing the GFCI and then resetting it.
We've all heard about
the dangers of the hair dryer that falls into the bath
water. As we have learned from early childhood water
and electricity don't mix. When a hair dryer falls into
the water, some of the current continues to travel back
through the cord to the receptacle in the normal way,
but some of it may "leak" and flow through the water
to the pipes and back to the ground (the real earth
ground). GFCIs are designed to detect the tiniest amount
current leakage and shut off the power extremely quickly.
In new installations, they are required in kitchens,
bathrooms, basements, garages, and outside your house.
If you are in the
tub, some of that current may flow through you-not a
great idea. The problem is that very small amounts of
current flowing across your heart can destroy the normal
rhythms of the heart. Because there is no huge surge
of electricity, the circuit breaker may not trip quickly
enough, or not at all.
The same danger exists
when your microwave's metal case get livened up. If
you touch the microwave and put your other hand on the
stove or a faucet, you can get livened up along with
it. But you may not stay alive for long.
GFCIs are designed
to detect the tiniest amount current leakage (in this
case, through you) and shut off the power quickly. In
new installations, they are required in kitchens, bathrooms,
basements, garages, and outside your house.
When
should I call an electrician?
Safety
First: the emergencies.
You plug in a radio and you see sparks. You go to turn
on a light, and the switch plate seems very hot. You
cannot get the thermostat to turn on the heat. Call
for help right away.
You turn on a light
switch; nothing happens, and then you notice that three
other rooms are also dark. So you turn the switch back
off, get out a flashlight, and reset the circuit breaker
or change the fuse. Still nothing. You remove the light
bulbs from the ceiling fixture and unplug everything
on the circuit; reset the breaker again. Still nothing.
It's time to talk with an electrician for advice. If
all goes well, you may be able to track down the problem
and maybe fix it. Last resort, you need a house call.
Safety Second:
the dangerous inconveniences.
The circuit breaker keeps tripping when you forget and
use the toaster and the coffee maker at the same time.
There are extension cords running under the living room
rug because there's no outlet near the TV. Your new
treadmill requires a 20 Ampere circuit, and you need
to run an extension cord to the closest 20 Amp outlet,
two rooms away. You've tripped on the kids' toys on
the unlit basement steps more than once; one of these
times, you're going to get hurt. Not necessarily cause
for an immediate call for help, but it's time for a
temporary fix and thinking about a permanent improvement.
Safety Third: comfort
and convenience.
Your fourth grader wants a computer in her room for
homework (and IM'ing, of course); you need a wireless
connection to your internet modem. You'd really like
a ceiling fan on the porch. You can't use your new heavy-duty
drill to mount shelves in the living room because all
the outlets have two holes and no ground. Wouldn't it
be nice (and cheaper to run) if the outdoor lights had
motion detectors? New light fixtures that make the kitchen
look a bit more modern or maybe bright enough to read
the morning paper? And then there's always the luxury
of central air conditioning or home theater.
Only rarely does an
improvement require more power to the house and the
dreaded, but popular and expensive, service upgrade.
There's usually a circuit than can support the new installations.
Powering up the enclosed porch or a home theater may
need a new circuit and breaker in the panel, but we're
not talking about rewiring your whole house to get another
light.
Still
have questions?
We're always looking
to answer your questions about electricity and any related
topic. Call us any time; we'd love to talk and maybe
use your question as the basis of an article in the
coming ONLY
CONNECT "Technology
for the Rest of Us" section.
ONLY CONNECT
specializing
in small electrical projects that should wait no longer
Voice:
617.484.2828
Email: TechnologyForTheRestOfUs@onlyconnectelectricians.com
www.onlyconnectelectricians.com
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