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. .

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:

  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  

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. 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.


Glossary of Key Terms

To Top>>

  AMP or Ampere: A measure of electrical current flow.
  Appliance: A non-lighting item. A device that consumes electricity (by its Resistance).
  Arcing: Electrical current passing across the gap, or space (through air) between two pieces of electrical wiring. Arcing uses the air itself like it is a piece of wire to conduct electricity.
  Armored Cable: A type of electrical wiring that uses a stainless steel or galvanized strip that is wound around the electrical conductors (wires). The wiring is protected from damage by this exterior metal shell.

  Arc-Fault Circuit Interrupter (AFCI): A circuit breaker that provides protection from fires that are caused by arcing, (see Arcing). An AFCI breaker is required at any bedroom circuit installed since 2002, and most rooms since 2008.
  Breaker or Circuit Breaker: An automatic safety device that shuts off the electrical power when the current (or amount of electricity or heat) becomes a greater volume of electricity than the breaker is designed to handle.

  Busbar: A piece of rigid metal found in an electrical panel. A busbar distributes electricity from the service entry cable to the various circuits by means of their connection to the busbar. There are two busbars in the standard residential electrical panel.
  Circuit: The path (usually a wire) through which current flows between an electrical energy source and an electrical device, appliance or fixture.
  Conductor: A material that offers a low resistance to an electric current flowing through it. Also, the wire used in the home’s electrical system as in the grounding conductor, service conductor etc.
  Conduit: A metal or plastic pipe through which electrical wires are run. Conduit protects wires from damage and are usually used in exposed locations, such as along the outer surface of a exterior house wall.
  Current: The organized flow of electrons (electricity) from one point to another or the flow (movement) of electricity through an electrical conductor. The standard unit of measure for electric current is the ampere (AMP).
  Double Tap: When a second circuit is added to a circuit breaker, in the electrical panel, so additional circuits can be added to the electrical system. This condition is not allowed, except with specific breakers that are designed to handle more than one circuit, and only when the circuit is properly wired to handle the flow (demand) of more than one circuit.
  Drip Loop (at the service entrance): Slack in the overhead electrical entrance wires (at the masthead) which prevents water from running down the service entrance wires and into the electrical panel. The entry of water into a service panel can create shorts, or breakers that may not trip or fault as designed. The entry of water into an electrical service panel is a very dangerous condition.
  Fuse: A safety device found in an electrical service panel designed to interrupt the flow of electrical current when an overload (too much demand) is detected. Fuses may be either a cartridge or screw in type. When the fuse detects an overload, a thin strip of metal inside the fuse melts and cuts off the flow of electricity, preventing further problems.
  Gauge: The standard, scale or size of measuring for circuit conductors (the size of the wire). In other words, every end use appliance requires a predetermined amount of electricity to operate as it was designed. A clothes washer needs more electricity to operate than a standard 60 WATT light bulb. The clothes washer needs a larger size of wire to operate safely than a light bulb would. The size of a wire (or wire gauge) is determined by what the wire is sending electricity to, for example a light.
  Ground Fault (GFI or GFCI) Outlet: An outlet which has a monitoring device that will trip (shut off the flow of electricity) when a dangerous condition is detected.

  Grounding: The process of connecting all home electrical devices, appliances and wiring, whether intentional or accidental, so that they are connected to the earth, at the outside of the house. This interconnected grid means that excess electrical current will seek and be absorbed by the ground. This is typically done by connecting the ground wire to the water service entrance, or to a metal rod buried in the earth. If home electrical systems were not grounded, errant (wayward) electricity could seek a person instead, and cause an electrical shock. Ben Franklin proved that electricity would seek the ground with his kite and key experiment, in the electrical storm. Ben Franklin is the father of the lighting rod.
  Hot: An electrically charged wire, black or red wire carrying a charge of 120 volts in home circuits. This is the wire that you would get a shock from. When the circuit breaker is closed, and electrical current is present.
  Insulator: A material that offers a high resistance to an electric current flowing through it. For in house wiring, an insulator is the coating on the outside of the wire that protects you from contact with the electricity being conducted through the wire.
  Junction Box: A covered metal or plastic box used to protect wire connections (or junctions) in an electrical circuit.

  Knob & Tube Wiring: Old branch, circuit, wiring using ceramic knobs to secure wire to surfaces and ceramic tubes to pass wires through framing members.

  Mast Head: The upper part of the metal conduit pipe, at the outside of the house, above the electric meter, where the electrical service wires from the street attach to the house.
  Neutral: The return conductor (white wire) of a circuit connected ultimately to the earth to receive flow “back” from a light or appliance. Contact with neutral wire should not give you a shock.
  Ohm: The measure of electrical resistance. (see Resistance).
  Outlet or Receptacle: An electrical-connecting device at which a consumer of electricity (for example , a light) is plugged into and is now “hard wired.” The light receives electricity, for the appliance to operate from an outlet.
  Overload or Overcurrent: When a larger than intended amount of electrical current flows through a conductor (wire). This leads to the generation of too much heat in the electrical system, which can lead to a fire. Circuit breakers are designed to protect from overloads. They trip or fault if too much electricity
passes through.
  Resistance: Resistance is the measure of how easily electricity passes through a conductor. It is measured in OHMS. Everything has the ability to conduct (allow) electricity to pass through it. Some objects allow electricity to flow (pass through) better than others. The best conductors of electricity are gold and silver which offer the least amount of resistance. They conduct electricity very well but are too expensive to use in our house as wiring. Copper and aluminum are the next best conductors, which is why the electrical wiring in our houses is copper.  Electric cook tops and electric strip heaters are designed to slow the flow of electricity. When you want to boil water, on your electric cooktop, you set the dial to HIGH and the burner eventually turns red. The metal in the burner is not the most efficient conductor of electricity, so the burner glows red hot as electricity is forced through it.
  Reverse Polarity: When the “Hot” conductor and the “Neutral” conductor wiring are reversely installed. The opposite of how the wires should be installed.
  Romex (NM) wiring: Refers to electrical wiring that is sheathed (or protected) by a plastic coating that houses the wiring. When you see the letters “NM” on the exterior plastic casing it refers to a “Non-Metallic” outer sheathing and not the wire inside. This type of wiring carries a hot, a neutral, and a ground wire. The name of the wiring comes from the Rome Wire Co. Romex is a generic term, just like XEROXing a copy.

  Service Conductors: The wires that bring electricity from the street to the house. The equipment and conductors that provide a connection with the power generation source (power plant).
  Service Drop: When the service conductors (wires), from the street to the house, are overhead.
  Service Entrance: That portion of a home’s electrical system from the utility pole to the home’s main electrical disconnect. The main electrical service disconnect is the circuit breaker that turns all of the house’s electrical power off at one point.
  Service Lateral: When the service conductors (wires), from the street to the house, are underground.
  Service Panel, Panel Box, Breaker Box: The large metal box that contains the individual circuit breakers for the house’s electrical needs. The electrical panel serves as the central distribution source for a houses electrical system. The “service panel” receives its power from the main electrical service conductors, which are supplied from the electric utility company. A service panel distributes this electricity to the individual circuits for lights, dishwashers and clothes dryers. It is very possible to have additional, smaller, “sub panel(s)” that further distribute electricity throughout the house.
  Short or Short Circuit: The accidental connection between two wire (conductors). The unintended continuity from a hot wire to something of different voltage. A short will not trip a breaker if its path has resistance.
  Switch: A device used to interrupt the flow of electrical current to its intended source. An example would be a light switch that stops (interrupts) the flow of electricity to the light when the light is “turned off.”
  Tapping Before the Main: Adding an additional electrical service to panels (circuits) before the house’s main electrical service disconnect switch. This is not allowed.
  Two Prong Outlet: Two prong outlets are connected to wiring that does not provide a ground wire. The grounding wire is present to protect you from electric shock. With the older “two prong” outlets, if something goes wrong with an ungrounded electrical appliance, you will receive an electric shock.
  Volt or Voltage: The electrical pressure (force) from an electrical generation plant to a house (like a battery to a flashlight). An example of the volt service supplied to a home today is a 120 volt service, but most commonly two separate120 volts service lines supplying the house with a 120/240 volt source.
  Watt or Wattage: The rate of electrical energy used by lights or appliances. When applied to devices, it indicates the maximum watts the device is designed to deliver or control.
  Wire: A bendable metal wire used for conducting electrical current. The size of the wire can vary and is determined by how much electricity an appliance needs to operate as the manufacture has designed. An electric clothes dryer needs more electricity to operate than an electric light bulb would. The need for more electricity means that the clothes dryer needs a larger wire to conduct electricity than an electric light bulb.

Next Section >>