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

All Newsletters >>

 
ABOUT US SERVICES CONTACT US HOME

COPYRIGHT© 2002-2011 INQUIRING EYE HOME INSPECTIONS   |   TERMS OF USE