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Hi! I hope you have
found my newsletters informative and helpful in the field.
Introduction
This months newsletter is the first of a three part series on
residential electrical wiring. The articles are designed to better
educate you on electrical wiring itself; i.e. the gauge of a wire
and their specific uses, the different types of insulators, the
different types of wire sheathing, and more importantly information
that will inform you on potential issues.
To accommodate this series I am sending you this information in May,
June and July, instead of my normal format of every other month. The
first article will discuss wire gauge, conductors, and insulators
since the days of Edison and the first light bulb. Everyday, here in
Fairfield County, we work with older homes that are built in the
late 1800s to the mid 1900s. This means that some of the houses
wiring can be up to 100 years old, so this information is very
important.
I have been receiving quite a few questions on tankless water
heaters. Remember all past newsletters can be found on my website
under the “About Us” section, or as a portion of the specific
section of the website that the article is relevant too. Ex. Arc
Fault Breakers are under the electrical section.
Residential Electrical Wiring Part 1
On New Years Eve 1879, Thomas Edison held a practical
demonstration of his newly invented electric lighting system in a
few homes in the town of Menlo Park, New Jersey. From this small
beginning with the electric light bulb, we are able to gaze around
our homes at the myriad of inventions that have followed in the last
129 years. From iPods to air conditioning, to home stereo systems,
this burgeoning display of electronics all had there beginning with
the electrification of the homes we live in and its meager
beginnings with the light bulb. By the end of the 1800’s electricity
in the home was becoming a reality for more and more people, today
it is expected.
A brief history on the invention of some electrical appliances.
|
| 1905 – electric iron |
1947 – room air conditioner |
| 1905 – Christmas
tree lights |
1951 - hand held hair dryer |
| 1907 – motor-driven
phonograph |
1956 – electric can opener |
| 1909 – vacuum
cleaner |
1959 – lighted telephone |
| 1911 – electric
toaster |
1967 – microwave oven |
| 1921 – refrigerator |
1972 – drip type coffee maker |
| 1924 – blender
|
1973 – garage door opener |
| 1925 – electric
mixer |
1975 – video game system |
| 1927 – coffee
percolator |
1975 – videotape recorder |
| 1927 – electric saw
|
1978 – personal computer |
| 1930 – heat lamp |
1982 – CD player |
| 1935 – electric fan |
1984 – phone answering machine
|
| 1937 – washing
machine |
1997 – DVD player |
| 1938 – garbage
disposer |
1999 – plasma TV |
| 1939 – television
set |
2002 – wireless router |
|
|
Edison must have realized early on that in order for his light bulb
to become a household item, the homes we live in had to be “wired”
for electricity to accommodate electrical use. He also realized the
dangers of electricity and that this wiring had to protect against
the possibility of a red-hot electrical wire starting a fire. The
insulating cover encasing the wire had to protect both against
burning this insulator itself and the framing and contents of a
house from catching on fire. The following is a discussion of this
wiring system that we as homeowners pay so little attention too or
concern about.
So what is a wire?
A wire is a single, usually cylindrical, elongated strand of “drawn”
metal. Our homes have different types and sizes of wires. Each size
and type of wire has a specific use that it is designed to
accommodate. Wire is sized by the American Wire Gauge (AWG) system.
The gauge (size) of the wire is determined by its end source,
appliance, or what the wire is feeding electricity too. The smaller
the number of the gauge (ex. 12 vs. 14) the larger the ampacity the
wire (end use item) it is servicing. The first attempt to adopt a
geometrical system was in 1855. This system established 39 steps
progressing with increasing gauge numbers giving smaller diameters.
This system was the predecessor to the AWG. Wire is made by
“drawing” it through a series of increasingly smaller dies or
“drawplates” to create its final size. It is believed that wire
gauge numbers were originally based on the number of dies that the
wire was drawn through. For example, No. 1 was the original “rod.” A
12 gauge wire starts with this number one size wire and then the
wire is passed through the draw plates 12 separate times to reduce
the size of the wire to a 12-gauge wire. If two more dies are added,
it becomes a 14-gauge wire. Therefore, the larger the gauge number,
the smaller the wire.
A device for measuring standard wire gauge
The wire that is used for a residential electrical system must be a
good transporter or “conductor” of electricity. It must be able to
efficiently move electricity from one point to another. Some metal
used for wire conductors, or wires, move electricity better than
others. Copper is the most common material used for residential and
commercial electrical wiring. Gold and silver are better conductors
of electricity, but they are far too expensive to be produced in
large enough quantities to be used for household wiring. Gold is
used in computer connections to make the computer run and respond
faster. That is why there are companies that recycle old computers
and recapture the gold that is used in the hardware.
A good “conductor” implies that the outer electrons of atoms are
loosely bound and free to move through the wire. The opposite of a
good conductor of electricity would be one where the electrons are
not able to move as freely like the heating elements for an electric
range cooktop and oven, or electric strip or wall heaters. For an
electric range or heater the control knob--or rheostat--determines
how much electricity you want to pass through the heating elements.
The more electricity that you ask for, the more the element glows
red and gets hot. The metal’s glow is because the electrons are not
able to flow freely, they are being transported poorly. They meet
resistance as they move through the element freely and the element
turns red. Another example of wiring getting hot is in older houses
when we have an insufficient quantity of electrical receptacles in a
room, and we plug too many of our modern electrical devices into an
outlet. We are asking for a large quantity of electricity to power
all these devices, and the wire gets hot. Many electrical fires are
started because we ask too much of the wiring in our walls. This,
and the over dependency on extension cords, is why the electrical
code over the years has decreased the required distance between
outlets, so that more receptacles are present in a room and so that
we do not overheat the wiring in the wall. (The extension cord has
historically been a large source of home fires). The electrical code
has adapted as we invent more and more uses for electricity.
Some specific applications with wire size: |
|
Function |
AMP |
Wire Size |
Outlets/Circuits |
Volts |
|
Lights |
15 |
14 gauge |
10 |
120 |
|
Outlets |
15 |
14 gauge |
10 |
120 |
|
Kitchen Counter Outlets |
20 |
12 gauge |
4 |
120 |
|
Refrigerator |
20 |
12 gauge |
1 |
120 |
|
Hot Water Heater |
30 |
10 gauge (3) |
1 |
240 |
|
Clothes Dryer |
30 |
10 gauge (3) |
1 |
240 |
|
Electric Range |
50 |
8 gauge (3) |
1 |
240 |
|
To protect the surrounding environment from the electricity passing
along the wiring the conductor must be wrapped in an insulator. An
insulator, also called a dielectric, is a material that contains no
free electrons so it will not permit the flow of electricity from
passing through it. An insulator protects anything that can
potentially come in contact with the wire from the electrical
current present in the cable.
Electrical wiring manufactured up to about 1925 used only naturally
occurring products such as asphalt, rubber, mica, cotton thread or
fabric as wiring insulators. Edison’s original wiring used
insulation made of gum rubber. This “rubber” insulation was actually
a mixture of ingredients and additives that included sulfur for a
vulcanizing agent. These elements, especially the sulfur, had a very
corrosive effect on the copper wiring, so the wiring was eventually
coated in tin to protect the copper from the corrosives. Rubber was
also very soft when first vulcanized, so cotton wrapping referred to
as “rag” or “cloth coating” was added as an outer coating for
protection of the rubber. Rubber insulators have lower toughness,
are brittle, can dry out and crack and offer a lower level of heat
resistance. Many older houses with cloth coated rubber wiring have
fewer outlets as well, and as mentioned before, this places a
greater stress on this existing wiring by asking it to provide
electricity to a greater array of electrical appliances. This
increased demand can create dangerous overheating conditions that
can possibly lead to electrical fires.
In the early 1950’s the wire industry moved away from rubber to the
newly developed thermoplastics (PVC). PVC does not dry out as
readily as rubber so the insulator does not become brittle and crack
with age. It also does not have the sulphur additives that rubber
required, so the copper wire does not have to be coated in tin to
protect the wire from corrosion. In the mid 1980’s the chemical
formulation for the PVC thermoplastic insulators was modified so
that the insulator was capable of withstanding far higher wire
temperatures than before. Thermoplastic insulators installed from
1984 to today can withstand temperatures of 90 degrees Celsius
versus the 75 degrees just prior to 1984, or the 60 degrees Celsius
of the rubber insulators of the past. This increased protection,
because of the increase in temperature capabilities of PVC, and
because plastic of the same thickness as rubber is a better
insulator, allows for the same size wire to carry more current
without damaging the insulator.
To learn more about electrical, visit our
website's
Anatomy of a Home section.
View part II or part III
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