This section outlines electrical distribution through the example of what happens when you turn on a light switch and what elements you need to make that light bulb light up.  The three primary elements are:

1. A power supply.  The electrical company
2. A switch and wiring.  The components of our house
3. A load or demand.  Lights, stereos, and electric ranges

		When you turn on a light a supply of electricity from a distant power generation plant gives us its product. The light switch closes a gate and a constant flow of electricity is allowed to flow through the wiring, and a circuit is completed. The switch completes a circuit (a loop) and makes a complete path for the energy to travel and illuminate the light bulb In that statement you have the basic elements needed. 1.) The supply from the generator. This can also be produced by direct current, for example, from a battery. 2.) The switch that allows the circuit to be created. The switch is closed. 3.) The bulb is the demand, or the item that needs the electricity, and the demand is met by the bulb illuminating. But how is that electricity made. How is it generated? Electricity is a basic part of nature. In its basic form, we think of the lightning bolt. Ben Franklin started the process of experimenting with, and trying to understand electricity. Remember the drawings of him flying a kite with a key attached to the string, in a thunder storm. This culminated with Thomas Edison who gave us the first full use for electricity with the invention of the electric light bulb in 1879. At a power plant many miles from your house is a generator that gives us our supply of electrical current. The basics of a generator are a large rotating magnet and a stationary conductor that is wrapped with a continuous piece of wire. As  the magnet rotates it creates a small current of electrons at each strand of wire. When all the small amounts of current
produced at each strand of wire wrap are added together, you come up with an electrical current of considerable size. This total current is more than one house can use by itself. Depending on the production capacity of the generator it may supply our neighborhood, our town, or our county.
Transformers are located at telephone poles, on our street, that turn or “transform” this large quantity of electricity into a usable amount for a house. A transformer is designed to increase or decrease the volts present. This electrical energy has to be reduced and controlled to be usable in our house with our appliances.   This balance for what is used and how it is used or installed  in our houses is determined by the National Electrical Code. The National Electrical Code is an electrical safety standard containing rules affecting a products’ installation and the use of electrical equipment. The NEC provides the formula and guidelines for our electrical contractor to determine what size our electrical service will
be and how to properly and safely wire from the panel to the light, receptacle or switch. The key here is the proper installation of a system of wiring and control devices to distribute this energy. This is determined by the type of lights and appliances that are needed at the house. When properly followed and installed this electrical system will safely protect the home owner.  When an electrical contractor is hired for the installation of an electrical system, his first job is to determine what he is going to install. General switches and outlets will fall into only one portion of his installation. He must determine if the house will have dishwashers, clothes washers, air conditioning systems, or whole house fans to name just a few. All of these components have specific wiring needs that when added together will be used to determine the total “demand” of the house.  This is important in calculating how big our electrical service, and wire, from the street must be. The electrician will add together the need of all these electrical appliances and lights and from there determine the demand for the house, the electrical service size from the pole, and the electrical panel size. The minimum (smallest) acceptable service size today is 100 AMPs. (Ampacity is the term for the amount of current carrying capacity of a wire). The current carrying capacity depends on the “area” of the wire. The larger the wire the larger the current, or AMPs the wire can handle.  Think of AMPs as a pipe: the larger the pipe, the more volume can be handled. Electricity will come to our house in a three wire system, called the service entry. Two hot lines of 120 volts a piece and a neutral. A single “Hot” wire provides 120-volt current for conventional lights and receptacles. Volts are the force that the electricity is being pushed through the wire from the original source of the power plant. When both hot wires are used together, with the neutral, they can power a 240-volt appliance such as an oven, electric hot water heater or air conditioner. So when you hear of a 120/240 volt electrical system this is what is being referred to: two hot wires with 120 volts a piece, and a neutral. If your electrical service line comes in overhead from the pole you can see these three lines as they attach to your house. Finally, there are Ohms, or resistance. The wiring in your wall is most commonly copper. Copper is a good conductor of electricity. Then think of the metal used in the coils for an electric range burner or oven element. The metal used in an electric range is not a good conductor of electricity and the element gets red hot when you turn on the controls to medium heat. This red glow is because the electricity passing through the wire is having a tough time. When you run up a hill you work harder. The same is true with electricity that is trying to pass through a wire that is not a good conductor of electricity.  The better the metal wire is at allowing electricity to be conducted, the less “resistance” is.
Once in the house the electrical panel is our key distribution or router source for the houses electrical needs. It takes the large amount of energy coming in from the street transformer and makes it usable at an individual location. Our three service wires from our pole enter the exterior of the house and are attached at the panel. All homes built today will pass through or start the individual circuit by connecting to a circuit breaker. A circuit breaker is a magnetic device that will “trip” or turn off if it detects a short or overload condition. The size of our panel, the number of circuits needed, is again determined by how many electrical devices we are intending to have. A 100 Amp panel will provide for 24-32 circuits, a 200 AMP panel will provide 32-40 circuits. In our panel the electricity is conveyed from our service wire to our circuit breaker by a bus bar. There are two bus bars in an electrical  panel, one for each 120 volt line. They do not touch each other. Circuit breakers are mounted/fastened to the bus bar. The circuit breaker controls the amount of current forced into a circuit. The electricity passes through the circuit breaker and passes through to our appliance. You can have single pole or double pole circuit breakers. Single pole breakers are for 120 volt   items like lights or the refrigerator. Double pole breakers are for items that require greater amounts of electricity to operate, like central air conditioner or electric hot water heater. A double pole breaker is actually two single breakers tied together. They are connected so they act as a single unit. A double pole draws its electricity from both bus bars, or 240 volts of service. (learn more about Arc Fault Circuit Breakers; March 2009 Newsletter.)

A key item to remember is that everything must match its intended use. The NEC code dictates that if you have a circuit breaker panel designed for 200 AMP use it must be matched with a corresponding service entry wire that is designed to handle a 200 AMP panel. In the house a 20 Amp circuit is matched with an appliance or outlet of specific 20 AMP need, and the wire size is 12 gauge, the size for 20 AMP use. This 20 AMPs is the maximum amount of electric current that should be drawn through the wire. Manufacturers determine the electrical need for their appliance, and the wiring in the wall and the circuit breaker must match these requirements. The wiring has to be of matching size, because if it is too small it will overheat and can start a fire in the wall. The objective is to have the properly sized wire to carry the electrical current that the appliance or light needs to operate.

We hear of wire fires in older houses where there may be an insufficient number of electrical outlets in a room. Adapters and extension cords are used to make up for this shortfall and they all tie into one receptacle. The demand is too much energy for the one receptacle to handle and the wire in the wall overheats and starts a fire. Or fuse systems where the fuse kept blowing and was eventually replaced with a larger size fuse than the system was intended to handle.  So now the wiring in the wall is again the weakest part of the system. Remember electricity is energy and energy is heat. Too much energy in the wrong place can be a problem.

So, what is a circuit? Electricity is designed to travel in a circle, or loop. Just like in any circle it starts at one point and finishes at the same point. Like a necklace with beads but in our case the bead wire is our conductor and our lights are the beads. It comes in at the panel and heads towards our light or appliance on our “hot” black wire of 120 volts, lights a bulb or powers our appliance, then returns along the neutral wire back to the panel. This complete path is our circuit. If you’ve heard of Reverse Polarity in an inspection report it is when the wiring has been crossed and the electricity isn’t traveling in a loop or circuit. This is also why outlets are designed to receive plugs in only one way. One prong is bigger than the other so that the plug can only be put in the receptacle one way, again so our electricity can only travel in a properly designed loop.

Some specific circuit specifications are:
 

The key to an electrical installation is that everything matches in size properly, as per the manufacturer’s requirements, and the electrical code, and that the electrical code was properly used as to the installation of the electrical system.

With this article I hope you can understand the basics of how electrical wiring should be installed. When you here at an inspection that the wire size was found to be incorrect or that reverse polarity was mentioned, you should have a better understanding of what that means.

One of the single largest safety issues within homes constructed 50 or more years ago is the quality of the original wiring (for more information on Residential Electrical Wiring, review our May, June, and July 2009 newsletters).  It is estimated that 50 percent of the wiring systems installed in these houses may not be keeping up with the increased demands placed on them. Just think of the number of electrical devices or modern conveniences invented in the last 30 years. The protective insulator will degrade with time. Heat, light and temperature can affect insulators, with oxidation and temperatures affecting the wiring itself.

Fuse panels are a portion the residential electrical system that is no longer considered safe. As we increase the number of electrical devices used in our homes over the years, we put a greater stress on the in wall wiring and electrical service panels. A common part of inspections in Fairfield County is fuse panels where the size of the fuse has been increased beyond its designed AMP requirements.
 

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