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basic electrical wiring

Electrical Safety. "Shocking Statistics

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basic electrical wiring

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    1: Basic Electrical Wiring Agricultural Science and Technology

    2: 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.

    3: 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.

    4: 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.

    5: 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.

    6: 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.

    7: 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.

    8: 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.

    9: 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.

    10: 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.

    11: 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.

    12: Amps Volts Watts (cont.) Thus, the following relationship exists. Work = Pressure x Flow Or Watts = Volts x Amperes

    13: Amps Volts Watts (cont.) This formula is commonly referred to as the West Virginia Formula W=VA When we know any two variables of the formula, we can calculate the other.

    14: Amps Volts Watts (cont.)

    15: Calculating Amperage

    16: Calculating Watts

    17: Calculating Volts

    18: 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.

    19: Cable Types

    20: Cable Types (cont.) In cable, there are four different colors or kinds of wire that one will use depending on the type of wire that is being used. Using 12-gauge wire as the example, there are four types of cable that one may buy.

    21: Cable Types (cont.) One is 12/2 with ground, which has one black conductor, one white conductor, and a bare ground conductor.

    22: Cable Types (cont.) A second cable is 12/2 without ground, which is the same as 12/2 with ground except that no bare ground conductor exists.

    23: Cable Types (cont.) A third type of cable is 12/3 with ground, which has one black conductor, one white conductor, one red conductor, and one bare ground conductor.

    24: Cable Types (cont.) The last type is 12/3 without ground which is like the 12/2 without ground. It has the three colored conductors, but no bare conductor.

    25: The symbols used for conductors and their respective colors are:

    26: Symbols Various devices are used as lamp holders, switches, and receptacles.

    27: Symbols (cont.)

    28: Symbols (cont.)

    29: Symbols (cont.)

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

    31: Symbols (cont.)

    32: Symbols (cont.)

    33: 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.

    34: Diagramming (cont.) When completing the diagram, it may be helpful to draw the white, neutral conductor from the source to its final destination within the circuit, first. Duplex receptacles and pull-chain lamp holders are normally wired so that they have “hot” or un-switched power at all times.

    35: Diagramming-3 way switches 3-way switches are always used in pairs. They are needed when one wishes to control a light from two different locations.

    36: Diagramming-3 way switches (cont.) 3-way switches have three screws or terminals, one is called control or common terminal. It is often darker colored than the other two terminals. The other two terminals are called traveler terminals.

    37: Diagramming-3 way switches (cont.) When the toggle switch is in one position, the common terminal carries current to one traveler terminal. When the toggle switch is in the other position, the common terminal carries current to the other traveler terminal.

    38: Diagramming-3 way switches (cont.) When diagramming and wiring 3-way switches, the hot current always enters the control terminal of one of the switches and always exits out of the control terminal of the other switch. The traveler terminals from one of the switches must connect to the traveler terminals of the other switch with no interference.

    39: Diagramming a Single Pole Switch

    42: Diagramming a Three Way Switch

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