Electrical Safety "Shocking Statistics“  There are approximately 290 accidental electrocutions each year.  An additional 800 people die in fires caused by faulty electrical systems every year.  Thousands are shocked and burned as the result of accidental contact with electricity every year.  An estimated $1.2 billion in property damage occurs each year due to faulty use of electricity.

Electricity  Electricity is the flow of electrons in a conductor.  The electrons must have a path to and from its source.  This path is called a circuit.

Electricity  Various electrical devices are used as a part of the circuit.  These devices are used for a variety of activities, such as turning the electricity off and on, providing electricity to various lights or appliances, etc.

Types of Electrical Currents  Electrical current comes in two forms: –Direct current (DC) Flows in only one direction. It is usually generated by battery-base electrical systems and used in the electrical systems of internal combustion engines or flashlight batteries. –Alternating current (AC) Reverses the direction of flow of current many times each second. AC is the type used in homes, factories, etc.

Electrical Service  Service is provided to homes, businesses and other small users of electricity by three wires from a utility pole.  Two of the wires are “hot,” each carrying 120 volts.  The other wire is “neutral,” and provides the return path for electricity.

Electrical Service (cont.)  These wires are connected to a service entrance, which is where the electricity enters a building.  A meter is used in the service entrance to measure the amount of electricity being used.

Electrical Service (cont.)  The service entrance is grounded with a wire connected to a ground rod driven several feet into the ground.  It is needed to provide a return path to the ground and to carry away stray electrical current out of the system.

Service Panel  Follows the meter.  It houses the circuit breakers for the system and is used to distribute the power to individual circuits throughout the system.

Overcurrent  When a circuit uses too much electricity, an overcurrent causes a circuit breaker to trip, shutting down the power to that circuit.  The excessive heat caused by an overcurrent condition may burn or damage a conductor’s insulation and cause a fire.  A circuit breaker is a heat-sensitive switch, which automatically trips when electricity demand is too great which causes the temperature in the conductor to get too hot.

Amps Volts Watts The following relationship exists between Amps, Volts and Watts.   Amperes are a measure of the rate of flow of electricity in a conductor.   Volts are a measure of electrical pressure.   Watts are a measure of the amount of energy or work that can be done by amperes and volts.

What symbols are used in drawing various electrical devices? In order to successfully draw a wiring circuit on paper, one needs to use various symbols that represent the equipment. Identify and draw various symbols used in drawing wiring diagrams or schematics.

Cable Types

One is 14/2 with ground, which has one black conductor, one white conductor, and a bare ground conductor.

Cable Types (cont.) A third type of cable is 14/3 with ground, which has one black conductor, one white conductor, one red conductor, and one bare ground conductor.

Additional symbols are used to identify terminals and indicate if wires are spliced or just crossing over.

Symbols (cont.)

MARRETTE External cap made of tough, durable polypropylene. Threaded entry helps guide large wire bundles into the spring chamber. Unique copper-coated spring helps resist corrosion. Approved for circuits up to 600 V, and lighting fixtures and sings up to 1,000 V.

Diagramming  Generally, black and red conductors carry “hot” power or current from the source to the devices within the circuit.  The white conductor is always used to carry the current back to the source.

Two and Three wire

How to wire a receptacle All receptacles should be wired such that the hot or live (black) lead is connected to a specific side of the outlet, and the neutral (white) lead to the other.