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ONLY CONNECT
answers some of your basic electrical questions-both
practical and theoretical. We strongly recommend
that you seek trained and qualified help when
you need electrical repairs or improvements. Please
let us know which answers are helpful. Contact
us for more details or with other questions at
eFAQs@onlyconnectelectricians.com
or at 617-484-2828. And, of course, call us to
explore solutions to your electrical problems
and set up an appointment for the work.
Knob-and-Tube
Wiring: What's the Big Deal?
- What is
Knob-and-Tube ?
The
oldest wiring system you're likely to encounter
is called "knob-and-tube". Knob-and-tube uses
individual wires supported by porcelain insulators
(knobs) and run inside porcelain cylinders (tubes)
when going through wood beams. Until the mid-1930s,
knob-and-tube wiring was installed in many homes.
It required real skill to install. Most installations
that we see are high quality work.
- Insurance
and Insulation
At
ONLY
CONNECT, we have been replacing larger
amounts of knob-and-tube wiring than ever before,
and none of these projects were impulse buys.
Homeowners did not really have much choice.
Understanding the issues is key. For
many sellers, buyers, and other homeowners,
replacing knob-and-tube wiring is not an option
or a choice. Here's why..
Insurers are driving the change. Nearly
all insurance companies refuse to insure knob-and-tube
wiring. In our experience, insurers require
a home to be free of knob-and-tube wiring before
a sale or very soon afterwards. They ask about
knob-and-tube wiring in the application form.
Insurers may see knob-and-tube wiring during
a claim inspection and ask about it. And they
can ask at yearly policy renewal time. Knowing
the issues can prevent a big surprise.
Planning to insulate to save on heating costs?
Insulation contractors cannot insulate near
live knob-and-tube wiring. Utility companies
offering insulation rebates require a licensed
electrician to certify that there is no live
knob-and-tube wiring. Over-heated wires can
cause fires, so the Mass. Electrical Code prohibits
covering live knob-and-wiring. Replacing knob-and-tube
is the only real solution.
What to do? We test a home's wiring
to determine if any live knob-and-tube requires
action. We look for hidden knob-and-tube that
may have been only partially replaced. We offer
solutions that meet your deadlines. We have
worked on small and large knob-and-tube projects,
but they are never a quick and simple day's
work.
- Is Knob-and-Tube
Safe?
Like
other electricians we know, we believe that
knob-and-tube wiring properly installed and
in good condition is both reliable and safe.
As with any type of wiring, damage or illegal
modifications can create safety hazards. We
do see installations where modern wiring has
been added to knob-and-tube in unsafe ways.
This is a problem.
Dangers. The biggest danger that we have
heard about starts at the connections between
wires in a knob-and-tube system. Knob-and-tube
splices are not contained inside an electrical
box. If the insulating tape that covers
splices loses its stickiness, it may not cover
the splice well. If the splice loosens up over
the years, it may heat up and create a fire
hazard.
To date, we have been unable to locate any
data about how often knob-and-tube wiring is
actually implicated in causing fires.
Appropriate Uses. Knob-and-tube has no ground
wire and is not appropriate for electrical equipment
that requires grounding (e.g., appliances like
washers, microwaves, refrigerators or electronic
equipment like TVs, computers, music systems).
Installing a new modern circuit can solve
this problem for a specific piece of equipment.
On the other hand, lamps, like many items, typically
have 2-pronged plugs and do not utilize a ground.
For more about knob-and-tube wiring, go to Cables
and Wires below.
- Electrical
Project Strategy
- How can
I keep the cost of electrical work down?
Planning. Any time you are going to paint a
room, it's time to think about electrical repairs
and any new receptacles, switches, networks
you may want. When an electrician works just
before the painter or plasterer comes, the work
goes a bit faster and therefore costs less.
Professional painters and plasterers can repair
the unavoidable holes needed for pulling new
wires into your walls and the crumbling of old
plaster around a new outlet. A slightly larger
hole or an extra hole goes quickly for them.
Going to extremes to minimize holes in your
walls can slow the electrician dramatically.
Get the electrician in just before the painting.
Circuit Breaker Panel Schedules. Having a complete
list of which receptacles and lights are controlled
by each circuit breaker saves the electrician
time-and you money.
- Is
upgrading my Electric Service to 200 Amps worthwhile?
In classic form, we'll give you a "definite
maybe" on this one. Our experience shows
that upgrading a service to 200 Amperes is rarely
particularly useful to customers. If you are
having trouble with individual circuit breakers
tripping, a new service is probably not the
answer. Most often, we find, that adding new
circuits and circuit breakers provides the needed
improvement. For example, a toaster over and
a microwave may be too large for a single circuit.
A treadmill may require its own 20 Ampere circuit.
A portable electric heater added to a circuit
with other things running make push the current
draw over the limit. A new, upgraded service
will not correct any of these problems. Most
often, we find that adding new circuits in key
locations in your home is the most effective
and cost-effective solution for many situations
like these.
We believe that service upgrades are sometimes
justified, usually by major renovations or additions
to a home or by additions of major new pieces
of electrically powered equipment like central
air conditioning or large installations of electric
heat. If your current services is 30 or 60 Amperes,
it is more common that an upgrade can be useful.
Ask yourself this question, "Have we ever
tripped the main circuit breaker?" If the
answer is yes, the likelihood is higher that
a service upgrade will be beneficial.
In thinking about a service upgrade, consider
the following: A 200 Ampere service, fully loaded
draws 48,000 Watts or 48 Kilowatts. Depending
on your power company, this electricity will
cost you 50¢ to 70¢ per hour. For
4 hours a day, 48 KW will cost you about $75
a month. Most people don't use that much electricity
in 4 hours-ever. There are, of course, exceptions
to every generalization.
- Useful
Terms for Educated Consumers
Three Way Switch: a switch used when
you want to be able to turn lights on and off
from two or more locations.
Ground Fault Outlet: a receptacle designed
protect human life by detecting small amounts
of electricity leaking from its normal path
and creating a safety hazard.
Ampere. measures the amount of electricity
that flows past a given point on a circuit (each
second).
Breaker Box (breaker panel): houses the
circuit breakers or fuses that protect and distribute
power to various parts of your house.
Circuit: all wiring controlled by one
a single fuse or circuit breaker.
Circuit breaker: a protective device
for each circuit that automatically cuts off
power from the main breaker to the circuit in
the event of an overload or short. The ampere
rating of the breaker tells how much current
can pass through the breaker before it will
"trip."
Main breaker: protects your entire house
by turning the power entering your home through
the breaker box on or off. The "main" is sometimes
found in the breaker box, or it may be in a
separate box and at another location.
Volt: measures the current pressure at
receptacles and lights. Think of it as analogous
to water pressure at a faucet. Average household
voltage is 120.
Watt:
the rate at which an electrical device (light
bulb, appliance, etc.) consumes energy. Watts
= Volts x Amperes. Watts measure power for electricity.
Horsepower, on the other hand, measures power
for automobiles. 550 watts = 1 horsepower.
Back To Top
Grounding
- So what
is grounding anyway?
When we "ground" a box or a piece
of equipment, we are actually connecting its
potentially dangerous pieces of metal to the
ground, the earth. The grounding electrode system
is a method to connect the neutral and grounding
conductors to the earth. The connection from
the electrical system to the grounding system
is made in only one place to avoid ground loops.
Ground fault electric currents (hot wire to
grounded case shorts) are conducted down the
ground wire to where it is interconnected with
the neutral and to the earth. Enough current
should flow to trip the circuit breaker or blow
the fuse.
- What
is the receptacle with the buttons in my bathroom?
Why do I need it? And how does it work?
Ground fault receptacles (Ground Fault Circuit
Interrupters or GFCIs) help protect you against
shocks that may kill you. Whenever there is
a short-circuit in hair dryer or any other piece
of equipment, electricity may flow to its case.
If you are holding the equipment and touch a
faucet or pipe, electric currents can cross
your heart on the way to the faucet and ultimately
to the ground. Only a few milliamperes of electricity
can cause your heart to malfunction.
To protect people from this danger, the Massachusetts
Electrical Code (the law), requires GFCIs in
renovations, new construction, and when replacing
certain receptacles. Receptacles near sinks
in bathrooms and kitchens, in unfinished basements,
and near pools or outdoors must be GFCI-protected.
GFCIs can shut off the electricity to the receptacle
much more quickly than a circuit breaker, typically
within a few cycles. The electronics in the
GFCI compare the electric current on the two
main wires to the outlet (the hot and neutral).
If the currents are not the same, the GFCI trips
and turns off the power.
- What
should grounding look like in a properly installed
switch, receptacle, or lighting box?
Every switch or receptacle should have a grounding
wire. Every metal box should have a grounding
wire. All the ground wires should be connected
together and connected to a grounding wire going
back to the circuit breaker panel or fuse box.
Any metal part that might accidentally be touched
by a live wire-due to insulation failure, deterioration,
or a loose wire-should be grounded.
Metal
boxes.
Both the metal box and the switch, receptacle,
or light fixture attached to the box must be
grounded. It is good practice never to rely
on the mounting screws to ground the switch,
receptacle, or light fixture to the box.
Plastic
boxes.
Plastic is mostly and insulator; the plastic
box itself does not need to be grounded. The
switch, receptacle, or light fixture attached
to the box does need to be grounded. Here are
three ways to do it correctly.
- How
does grounding work when a lamp has a 2-prong
plug?
This is a great question because most electric
things we have in our houses to day have 2-prong
plugs. The answer is: 2-prong plugs and 2-hole
receptacles provide NO GROUNDING PROTECTION.
Many pieces of electrical equipment manufactured
today have no exposed metal parts and are constructed
to prevent users from touching live parts.
Properly constructed table lamps and the like
should have "polarized" plugs. The
larger prong is inserted into the larger hole
in the receptacle and connects with the "neutral"
wire. The smaller prong connects to the "hot"
wire. Inside the lamp, the neutral connects
to the threaded shell that you screw your lightbulb
into. The hot connects to the little tab in
the bottom of the lightbulb socket and is harder
to reach with a finger. This arrangement lessens
the chance that you will touch a hot part of
the lamp and risk getting shocked.
Whenever any electrical equipment, from a vacuum
cleaner to a drill or a lamp, has a 3-prong
plug, you need a 3-hole, grounded outlet to
plug it in safely.
- What
is 2-wire Romex? And what is it for?
Two-wire Romex cable is old and does not have
a ground. It is no longer installed. It should
be replaced if you need a ground. Replace it
when you need a ground.
- I
know what a "hot" wire is. I found
out the hard way. What is the difference between
a neutral and a ground wire?
Let's start at the beginning. Three wires connect
to the receptacle in your living room, where
a computer with a 3-prong plug is attached.
Technically speaker, these three wires are the
hot wire (black), grounded wire which is commonly
called the neutral (white), and the grounding
wire commonly call the ground wire (bare, green,
or green with yellow stripe).
When your computer is running, electricity flows
through the hot and the neutral. Back at the
circuit breaker panel, the neutral is attached
to a wire to the earth or to a water pipe going
into the earth. DON'T TRY THIS-AT HOME OR ELSEWHERE.
If everything is perfect, you can attach a wire
from the neutral hole at the outlet to the earth
and no electricity will flow. ESPECIALLY DON'T
TRY THIS. In fact, if you touch the neutral
and touch the earth, you should not get a shock.
Creating this safe situation is a major reason
for the grounded neutral. But remember, everything
is rarely perfect. Do not experiment with the
neutral or any live wire.
Even when your computer is running, no electricity
should flow through the grounding wire. The
grounding wire is there for the occasional times
that something goes wrong and a hot wire connects
with the case of equipment or a outlet box.
It then provides a path to complete the circuit
and trip the breaker. It is an important safety
device. NEVER USE THE GROUNDING WIRE FOR ANY
OTHER PURPOSE.
- Does knob-and-tube
wiring or 2-wire cloth-covered cable have a
grounding wire?
No.
- What
do banks think about knob-and-tube?
Some banks get nervous about knob-and-tube.
They may insist that you replace it before they
give you a mortgage.
Back To Top
Computers
and Networks
- How
important are surge suppressors/protectors?
Are they worth the money?
In two words: very and yes.
Surge suppressors protect the delicate electronics
in everything from refrigerators to computers.
In normal circumstances, the voltage in your
house can vary enough to destroy electronics.
During lightning storms, the risk is higher
and more immediate.
You've seen the snow on your television when
you run an old vacuum cleaner. Computers and
anything with a computer in it can be affected
by motors turning on or off in your house. Plugging
your computer into a surge suppressor plugged
into the wall can protect against the snow (noise)
and help protect against voltage surges from
outside your house.
Whole house surge suppressors (installed at
your circuit breaker panel) help protect everything
against voltage surges from outside but don't
stop the noise generated inside the house. Depending
on your situation, you may want one or both.
Surge suppressors are absolutely worth the money.
We know people who've lost computers, televisions,
hifi equipment, and refrigerators during storms.
Even though surge suppressors won't protect
against huge voltage surges, they are cost-effective
insurance.
- I
need a computer network in my house. Should
we run wires or go wireless?
We did a back of the envelope calculation and
decided that new wireless equipment can support
High Definition Television signals. That's enough
speed for almost everybody. And wireless will
only get better.
At this point in history, wired networks are
for special situations. Wireless networks are
getting faster and more reliable every week.
If you are running a data-intensive business
from your home, you may need the speed of CAT6
cable or Gigabit Ethernet. But even if your
teenager plays graphics-intensive games online
or you download massive amounts of data from
work each night, wireless will probably do just
fine. After all, a wireless network at home
is faster than any Internet connection you can
afford.
Some houses interfere with wireless network
signals to the point where you cannot go this
way. Often the problem is plaster with wire
mesh lathe (after wood lathe, but before wallboard).
In these cases, it is worth explore powerline
and phoneline networks, which both use wires
already in your walls. As a last resort, there's
installing Ethernet wiring in your walls.
Why do we try to avoid wired networks? Simply
because it can get expensive, and you often
don't get much extra value for your investment.
Do you need the speed or copper wires? (usually
not). Are wires more convenient? (absolutely
the opposite). Installing wires of any kind
in the walls of an existing house is one of
the most expensive parts of any electrical or
network project. The wire itself is cheap, but
it takes a lot of time.
Back To Top
Extension
Cords
- Extension
cords and over-stuffed outlets: Are they safe?
What should I do? Do I need extra outlets or
extra circuits?
Extension cords are really for temporary use.
The equipment cord should be long enough, and
an outlet close enough, to plug it in directly.
Surge protectors seem to contradict this, but
they are not extension cords, they are safety
devices to protect your equipment. Note they
don't have very long cords.
An additional outlet may solve the problem.
If the problem is overloading a specific outlet,
you may need an additional circuit - not a new
service.
- Extension
Cord "Do's and Don'ts"
Never
run an extension cord under a rug.
Never
cover an extension cord with carpet, pillows,
or other material.
Never
connect an extension cord to the house or furniture
with tape, staples or nails.
Never
connect one extension cord to another unless
you know how to calculate electrical loads.
Never
use extension cords to "solve" the shortcomings
of a house with one or two receptacles per room.
Never
use a long cord before uncoiling it.
Use an extension cord ONLY
as a temporary measure and install and CONNECT
a permanent solution SOON.
The Massachusetts Electric Code helps reduce
or eliminate the need for extension cords by
specifying requirements for how many outlets
belong in a room and where they should be located.
Back To Top
Cables
and Wires
- What do
the different colors on wire insulation mean?
The colors are for safety. They indicate the
purpose of the wire and the voltage that should
run through the wire. Observing the colors-and
then testing to be certain the color-coding
is correct-helps keep human fingers out of places
they don't belong also help speed the electrician's
work.
In houses, apartments, and condos with 120 and
240 power, all the wire insulation is black,
red, blue, white, or green. Sometimes, the wires
are marked with colored tape. The blacks, reds,
and blues are the "hot" wires; the
whites are grounded or "neutral" wires,
and the greens are grounding wires.
To confuse you a bit more, the color of wires
going to switches may be different.. Plastic
covered cables (leading brand name: Romex™)
come with two insulator wires (black and white)
and one uninsulated wire (the grounding wire).
In the diagram below, a cable from the circuit
breaker panel brings power to a ceiling light.
Another cable (the switch leg) connects the
ceiling light with a wall switch. Correct color-coding
is shown below. Talk with your electrician for
a more detailed explanation.
- Knob-and-tube,
Romex™, BX, UF cables: What is 2-wire Romex,
and what is it for?
Knob-and-tube
The oldest wiring system you're likely to encounter
is called "knob-and-tube" (K&T).
It was installed as recently as the mid-1930s.
Individual wires are mounted on ceramic posts
(knobs) and run along joists or studs. When
the wires run through a joist or stud, ceramic
tubes (tubes) protect the insulation from the
wood. Wires are connected or spliced by twisting
them together, soldering, and wrapping with
tape. When K&T isn't color-coded, a tester
is required to identify "hot" and
"neutral" wires.
In general, electricians installing knob-and-tube
were careful; the workmanship tends to be pretty
good. The wire, insulation and insulators tend
to stand up very well. Most K&T I've seen,
for example, is in quite good condition. The
distance between the wires added another safety
factor: squirrels gnawing cables in your attic
or basement cannot chew through the insulation
in one bite and short out the hot and neutral.
Since
it tends to be in pretty good condition, knob-and-tube
does not need to be replaced merely because
it is knob-and-tube. Renovations that may have
damaged it are a cause for concern and replacement.
If your insurance company insists that you remove
the knob-and-tube or you want to insulate walls
that contain knob-and-tube, you many not have
much choice.
There
are two major shortcomins to knob-and-tube wiring.
First, there is no ground, and it is difficult
and usually impractical to install grounding
for a knob-and-tube circuit. It is typically
more cost-effective to replace the K&T with
modern wiring. See the section on grounding
for a discussion of when grounding is valuable.
The second problem with K&T has to do with
building insulation. It is both unsafe and a
violation of the National Electrical Code to
run K&T wiring where building insulation
surrounds the wires. While the insulation keeps
you warm by trapping heat in your home, it also
traps heat generated in the wire; this extra
heat can cause the wire insulation to deteriorate
more quickly and create electrical and fire
hazards. Because splices between wires are not
contained inside boxes, faulty splices that
may heat up can ignite the building insulation.
Replacing knob-and-tube wiring typically involves
installing new cables in the walls and ceilings
of your home. This can be time consuming and
expensive. When you are painting or replastering,
or better yet renovating a section of your house,
it is much easier and faster to install cable
in the walls. It is the most economical time
to consider replacing knob-and-tube. Talk with
your electrician or municipal wiring inspector
about the best course of action for each individual
situation.
Multi-conductor
cables
In the 1940s and 1950s, 2-wire cables, sheathed
in a cloth and varnish insulation were used.
These cables look similar to the plastic sheathed
cable used today. Like knob-and-tube, they have
no grounding conductor. Major problems are brittle
insulation that crumbles when touched and the
lack of a ground wire. Not infrequently, cables
that look like modern Romex™ (a brand name)
are actually 2-wire cables with no ground. They
often cause extra work when re-wiring or changing
2-hole receptacles to 3-hole grounding receptacles.
BX
Cable
BX, properly called armored cable or Type AC
cable, has a flexib le, spiral steel or aluminum
jacket. Much of it is very old, but BX and similar
types of cables are still installed today to
provide physical protection to the wires. The
metal jacket acts as the grounding wire. Sometimes,
old BX cable also has crumbling insulation problems,
especially in boxes above ceiling lights, where
it can get over heated. It is not unusual for
vibrations in a building to loosen the insulation
and cause the hot wire to short circuit to the
cable jacket or wiring boxes. If the jacket
is rusted, it the jacket is rusted or the fittings
are loose, BX may not provide a good grounding
connection and may pose a fire hazard.
Because the insulation may be brittle, replacing
a receptacle or switch fed by BX can turn into
a several hour effort to re-insulate the exposed
wires with electrical tape or heat-shrink tubing.
http://www.nexans.ca/egy/images/AC90BX.jpg
Non-metallic
Sheated Cable
Often called Romex™, a popular brand, this
is the cable most commonly used in homes today.
Except for wet locations and areas where physical
damage is a danger, non-metall sheathed cable
is suitable for most residential uses.
UF
Cable
Underground feeder cable is rated for dry, damp,
wet or corrosive locations, and for direct burial
in the earth. The sheathing on UF cable is also
designed to resist deterioration from the ultra-violet
light in sunlight. UF cable is a necessity for
outdoor wiring. When buried, it must meet depth
requirements to protect it from accidental damage
from shovels, roto-tillers, and the like.
- Why does
it take so much time to "snake" new
cables into walls?
Getting wire into walls when there's no plaster
or sheetrock is pretty fast and easy. When electricians
want to limit the number and size of holes in
the walls of your intact house, the situation
is different. Some small holes are usually unavoidable,
but getting wire from one hole to another requires
wiggling a spring steel "snake" into
the wall and aiming for the next hole. Sometimes,
all to rarely, it flies right in and pops out
the next hole. Usually, it's more art than science,
putting one snake in and then working to "catch"
it with another snake at the next hole.
On top of this, electricians discover wood supports
hidden inside the walls when snaking. In old
houses, lots of wood substituted wood for engineering:
keeping adding wood until it feels safe and
strong. Hidden wood means more holes in the
walls and more drilling to allow the wire through.
At the same time, it is important to keep the
holes small and easily patchable.
The best way to speed the snaking process is
to do electrical work before the painters come.
That way there can be more, larger holes-made
with less care and more speed. When the professional
prepare the walls for painting, they can patch
the holes quickly and more economically.
Back To Top
Circuit
Breakers and Fuses
- What's
the difference between 110 volt, 115 volt, and
120 volt circuits?
Simply
put, they are all the same. The actual voltage
is typically between 117 volts and 124 volts;
110, 115, and 120 (and 220, 230, and 240) are
just names that come out of history.
-
One of my circuit breakers tripped, but I could
not reset it. What's the problem?
The
first thing to check is
whether you have removed the problem that tripped
the breaker. If you were doing something, like
plugging something into an outlet on the circuit,
remove it. Then reset the breaker.
Resetting the breaker: Most circuit breakers
move to a middle position when they trip-not
"on" but not fully "off." First, push the handle
all the way to off; it should stay there. Then,
reset the handle to the "on" position. If the
breaker won't stay in the "on" position now,
you may need help locating the problem.
-
What is a circuit breaker panel schedule, and
why do I need one?
A circuit breaker panel schedule is simply a
list of which receptacles and lights are controlled
by each circuit breaker. They are often posted
on the inside of the panel cover. They are most
often either blank or scribbled over and illegible.
It is worth making a complete, easy to read
list: it will save you time and energy when
a circuit breaker trips, and it will save an
electrician time-and you money. You probably
have better things to do with your money than
pay an electrician to map out the circuits in
your house. And it puts most electricians in
a better mood.
- Are
circuit breakers better than fuses? Should we
replace our fuse box?
If you still have fuses, it may mean you have
old wiring-that may have crumbling insulation
or may just not be good enough for modern demands.
But the fuses themselves are pretty good for
many situations. Unless there is a particular
problem with your fuses, allocate your money
to electrical work that will make your house
safer, more comfortable, more convenient, or
more fun.
Old may mean worn out for many things, but fuse
technology lives almost forever. Fuses break
an electrical circuit when a metal link gets
hot and melts. It's low tech; there are no moving
parts; there's nothing to jam or fail: metal
melts when it gets hot enough. Period. It may
be inconvenient because you need to keep a supply
of fuses on hand and change them. But fuses
are reliable.
We have heard claims that statistics show that
fuse panels have a significantly higher risk
of causing a fire than breaker panels, usually
because a fuse is not screwed in properly, or
because the contacts have corroded, or because
the wrong size fuse has been installed. A penny
or aluminum foil under the fuse is a dangerous
trick. We have not seen the research ourselves.
- What's
the difference between and overloaded circuit
and a short? Does it matter?
Plug
a 2000 watt toaster oven into a 15 Amp circuit
and the a fuse takes a little time to blow,
a circuit breaker takes some time to trip. It's
drawing 16-2/3 Amps, just a little too much
current, which takes time to heat up and melt
the fuse or set off the breaker.
Drop a big kitchen knife on the counter and
cut through the cord. When the knife blade connects
the two wires in the cord, you get a spark.
It draws a lot of current and melts the fuse
or trips the circuit breaker immediately.
In both cases, the circuit breaker or the fuse
does its job; it acts as an over-current protection
device and shuts down the electricity.
- I've
heard about a new kind of breaker, Arc Fault
Circuit Interrupters. What are they and do I
need them?
Arc Fault Circuit Interrupters (AFCI) are designed
to detect early signs of trouble in a circuit
and turn off the circuit to prevent possible
fires. They are required by the Massachusetts
Electrical Code in some situations, like newly
constructed bedrooms.
If there is a loose connection in a wire in
your wall or in something you've plugged in,
there may be small sparks that could start a
fire. The sparks affect the shape of the 60
cycle waves in your electricity in very specific
ways. AFCIs have electronics to detect this
change, the signature of sparking (or arcing)
and turn off the power more quickly than circuit
breakers.
-
Why are some of the handles of circuit breakers
in my panel connected together?
Equipment like electric baseboard heaters require
240 volts (also called 220 volts, 215 volts,
and 210 volts, but don't worry about that) to
operate. The circuit feeding 240 volt equipment
requires two circuit breakers. To assure that
all power to the equipment is turned off at
the same time, the handles are tied together;
if one goes, they both go.
Also, often two separate circuits in the same
part of your house are fed by a single cable
with 3 wires and a ground. One "hot"
wire for each circuit, a shared "neutral,"
and a shared "ground." Say, for instance,
that the two receptacles in a box are on different
circuits. Most often, only one of the circuits
might have trouble at any given time. When the
circuit breaker for that circuit trips, you
might think that it's safe to open the box and
fix something. If the breaker handles for the
two circuits were not tied together, there would
still be electric power in the box. The "handle
tie" is to keep you alive.
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Fans
and Fixtures of all Sorts
- What
does it take to repair or replace an old, noisy
bathroom fan?
Bathroom fans get old. Sometimes they stop running
altogether, which can sometimes be an enormous
relief from the noise. Typically, bathroom fans
have two parts: 1) the case that mounts in a
hole cut in the ceiling (the rough), and 2)
the fan and motor that attach to the case, and
the cover.
If replacement fans were the same size as the
originals, it would be easy to remove the cover,
unplug and unbolt the fan or light, and replace
them. Unfortunately, and we are suspicious that
this is no accident, new models rarely fit exactly.
Sometimes you can obtain replacement parts direct
from the manufacturer, often at higher prices
than an entire brand new. Unit. It work out
cheaper because, with a little handiness, some
scraped knuckles, and a knowledge of electrical
safety procedures, you may be able to replace
the part yourself.
If replacement parts are not available, you
may find a new fan unit that has fits the existing
hole in the ceiling, but avoiding real damage
to the ceiling will require careful carpentry-and
there is still rewiring to do. Most often, new
fans are a different size and require electrical
work, patching, and painting. Replacing a bathroom
fan is rarely a project that fits into a ½-hour
home improvement TV show.
-
I've seen ceiling fans from $100 to $500 or
more. What's the difference, and what does it
take to install them?
Cheap to expensive: style, reliability, convenience.
Getting a lot of choice on what it looks like
costs money. More expensive fans allow controlling
the fan a light over the 2 switch wires that
are already there. Cheaper models often require
a third wire, which requires getting new wires
in the wall (A more expensive fan is often cheaper.)
Convenience: more expensive fans have more elaborate
controls: speed, forward-reverse, dimming; and
hand held remotes (hand-held remotes also eliminate
the need for extra wires.
-
Fixtures:
why do they specify maximum wattage for the
bulbs? (which electricians call lamps)
Lights generate heat. The wattage limit is to
avoid damaging the lamp socket or the wiring
and risking a fire. If you've ever looked at
old wires when a ceiling fixture is removed,
the insulation is often crumbling. It's gotten
too hot for too long, dried out, and become
brittle. New fixtures have fiberglass insulation
that is supposed to protect the wires up to
the maximum wattage on the label. Over time,
they will still become brittle, but more slowly.
Nothing is forever. Obey the label. Low wattage
compact fluorescents, if they fit, are sometimes
a good solution to getting more light.
-
What are
the good and bad points of compact fluorescents?
Compact fluorescents are miniature fluorescent
lamps, with all the electronics attached. The
common, garden variety compact fluorescent is
designed to be screwed into a regular light
bulb socket. The advantages are that they use
less electricity to run, they last longer and
have to be replaced less often, and they generate
less heat. The disadvantages are that you cannot
use a dimmer with them and that some people
do not like the color of the light. But color
choices are getting better every year.
- How
do I tell which is the hot wire and which is
the neutral in a table lamp?
The Plug: On newer table lamps, the prongs on
the plug are different sizes. The larger prong
is (should be) the neutral. The receptacle in
the wall has different sized slots; the longer
slot is (should be) the neutral. For safety,
the plug should fit in only one way.
The cord: If you rub your fingers along the
two sides of the cord, one should be smooth
while the other has little ridges. The ridges
are (should be) on the neutral wire side.
Strictly speaking, the neutral wire is called
the identified conductor. That's why the neutral
has the larger prong and the ridged side of
the cord.
The lamp socket: The shell of the socket, the
threaded part where you screw the light bulb
in, is (should be) attached to the neutral.
The tab in the center of the bottom of the socket,
is (should be) attached to the hot wire. This
arrangement makes the part that can give you
a shock harder to reach with your fingers.
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Do-It-Yourself
- Always
wear safety goggles or glasses when working
on your house. They protect against flying pieces
when cutting wire, against sparks and hot flying
metal, and against chips and plaster when you
drill or cut. Whenever you are not absolutely
certain that you know how to do something safely
and are capable of doing it safely, don't do
it.
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Disclaimer
Although we've
done a fair bit of wiring, these eFAQ comments
are necessarily limited and incomplete. We cannot
and will not be responsible for what you do.
We do not recommend that you perform any work
for which you are not adequately trained and
skilled. If you are at all uncertain about what
is correct or safe, don't do it. Contact someone
qualified -- a licensed electrician or your
local electrical inspector. Electricity is no
joke; mistakes can result in shocks, fires,
mutilation, or death.
Our comments are based on the U.S. National
Electrical Code (NEC) and our own experience.
Our explanations are intended to provide general
background information as a starting point for
further study. We want you to be an informed,
educated consumer of electrical services. Know
what you want, and know what you are buying.
If you have questions or doubts about what we
say, please let us know.
The NEC has the force of law only when local
or state governments adopt it. Massachusetts
has adopted the National Electrical Code as
the law, with some significant changes and additions.
Remember that the Massachusetts Electrical Code
is a set of minimal standards; it is not a project
design guide. Meeting Code requirements will
not necessarily provide the convenience you
desire. It is often smart to go beyond its minimal
requirements.
Contact us
for more details or with other questions at
eFAQs@onlyconnectelectricians.com
or at 617-484-2828. And, of course, call us
to explore solutions to your electrical problems
and set up an appointment for the work.
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