Level: Middle to H.S.
Time involvement: 15-20 minutes.
The story of “home” electricity is a relatively modern one. Barely 25 years before the Wright Brothers flew the first successful airplane (1903), small electrical power generating stations began to appear in very limited areas near factories or in cities. The great Chicago World’s Fair of 1893 featured huge exhibits of the wonders of electrical power. Although electricity came first to cities, electricity for rural area had to wait. In 1935 Congress passed the Rural Electrification Act (REA) which funded many rural CO-OPs to build the distribution networks required. Hundreds of small regional companies built power plants, mostly hydro (water) powered, and strung power lines first along highways and eventually to the more remote customers.
Shortly before the 1893 Fair, a “War of the Currents” had bee waged between Thomas Edison, who famously invented a successful electric light bulb in 1879, and George Westinghouse over whether Direct Current (DC) or Alternating Current (AC) would be the dominant method of sending power many miles to customers. Because 4 miles was about the maximum distance that DC power could be sent without huge energy losses, AC current eventually won out.
Another problem that had to be worked out was how to share the “load” between two neighboring companies. If company A had trouble with it generators and Company B had excess power to spare there was no practical way to share customers. Today that problem has been largely solved and the “grid” virtually covers the entire United States and parts of Canada and Mexico.
This lesson will touch briefly on the details of the power distribution system and focus on “Watts” inside the walls of your house. Power generating stations can be sited almost anywhere. They need to purchase fuel, which today is becoming less dependent on coal, and more on Nuclear, Natural Gas, Hydro, and increasingly on Renewable Wind and Solar. Getting the power long distances is accomplished by High Voltage (approaching a million volts) tall transmission towers and lines. Many sub-stations step down the voltage to about 25 thousand volts and send it down high-ways and streets to your house where it is further stepped down at a pole or ground transformer to a customer safe 110-240volts.
Because electricity is a commodity like gasoline, milk, or water, it has a price. Before it even enters your home it passes through a meter, which records your usage. Once it enters your house it must first go through a “Distribution Panel” sometimes called a “Load Center”. The distribution panel has two jobs: first to protect the wires in the house from becoming overloaded and causing a fire, and dividing up the power into a dozen or more branch circuits. The first job of safeguarding the wires is done by circuit breakers. Years ago replaceable fuses were used. If an overload occurred the fuse would “blow” and something would have to be unplugged, and the fuse would have to be replaced with a new one. Today, circuit breakers will “trip” and the homeowner must determine what appliance or light caused the overload and shift it to another branch circuit. The circuit breaker then is simply “re-set”.
Like any modern task a vocabulary has evolved to explain or understand the task. Terms like re-boot, download, or wifi did not exist before the computer age. Products today carry electrical specifications that aid the purchaser to understand power consumption and operating limitations. So, here are a few basic terms and what they mean.
Voltage = how much electrical pressure is available. Regardless if the house is using a little or a lot of energy the power company will continue to deliver power at a certain voltage. In general, lights and small appliance will operate at 110 to 120- volts. Electric stoves, Water heaters, and clothes dryers will be supplied with heavier wires and use 220-240 service.
Current is like the flow of water, a flow rate of ten gallons a minute would be a strong flow compared to a gallon an hour. Electrical current is measured in “Amps” which is short for Amperes. A hundred watt light bulb would use about one “amp” A hair dryer could use 10 amps or more, and a stove might use 30 amps on a 220 volt circuit.
Regardless if you fill your car’s gas tank slowly or quickly, if you put in 15 gallons you pay for only 15 gallons. Watt-hours are like the gallons. Your electric bill will tell you how many watt-hours you used for the month. So, a light bulb in the attic left on for a month may use more electricity than a hair dryer used for only a few minutes a day.
The last term you will see on appliance labels is the required frequency of the device. 50-75 years ago appliances might specify that the device could use or AC or DC electricity. With the exception of incandescent light bulbs, today, virtually all appliances will specify Alternating Current (AC) at a frequency of 60Hz. This simply means that the voltage reverses the direction of flow 60 times per second. If you have ever noticed a hum or buzz from electrical devices it is likely that the frequency of that sound was 60 Hz.
The next section will describe in some detail what you will find inside the walls of your house. It is not meant as a guide to do-it-yourself repairs but as an education about the “nuts and bolts” of house wiring. A very strict National Electrical Code (NEC) exists that must be followed by all licensed electricians in addition to complying with any local codes. Although a homeowner is allowed some freedom in making repairs it is best to consult a licensed electrician if in doubt.
In addition to electrical power wiring all houses will have many smaller wires for telephones, computers, TVs, thermostats, door bells, security systems, intercoms, etc. These are best left to trained personnel not because of any shock hazard but because the wires are often color coded and a mix-up could result in damage to equipment. A word about safety with the 110 volt or higher wiring. It can not only shock, and burn but can cause death. Improper wiring can lead to sparks and fires.
Today house wiring is enclosed in a protective color-coded “jacket”. The color indicates the maximum safe current. For example white indicates a maximum current of 15 amps, yellow: 20 amps. Higher ratings have other colors. Properly wired the wire size must not be lower than the circuit breaker protecting them. Older houses built before about 1960 may have two wire un-grounded systems. Newer houses now all have 3 wire grounded wires. The reason the code changed was to prevent electrical shock from faulty appliances. For example with the old wiring a toaster with a certain electrical fault could allow 110 volts to be in contact with the outer case. The risk is obvious. The key to the “new” 3-wire system is the plug. The longer center “prong” is the ground connection. When used in an older house with only 2 holes for the plug a special adaptor must be used. Removing the ground prong is not only illegal, it is foolish. With the 3-wire grounded system the case is always connected to the safety ground wire. The photograph shows several different sizes and applications of wire, in addition to common electrician tools and test equipment. Code requirement are specific about how wires must be supported, for example long dangling wires must be enclosed in an electrical conduit or supported at certain intervals. Plastic or metal boxes provide secure mounts for switches, outlets, and lights. Removing the protective covers can be done for painting but should promptly replaced.
Master, licensed electricians have years of training and have to pass rigid exams. Electricians take pride in their work and gladly give advice to customers.
Note: Nothing in this lesson is intended as technical advice but as information that will raise awareness about the benefits and risks of electrical power and how to ask better questions.