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Electrical Wiring. Lesson #1: Understanding Circuits. What is a circuit?. Two or more conductors (wires) through which a current flows from a source to one or more outlets. The source is where the electrical current originates within the house. Usually the breaker box or breaker panel.
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Electrical Wiring Lesson #1: Understanding Circuits
What is a circuit? • Two or more conductors (wires) through which a current flows from a source to one or more outlets. • The source is where the electrical current originates within the house. Usually the breaker box or breaker panel. • A conductor is any type material used to carry electrical current. May also be called a wire.
A cable is when two or more insulated wires are bound together. • An outlet is any device that allows for the escape of electricity. This may be a receptacle or light fixture, etc.
Types of Circuits • Branch Circuits • A circuit that runs from a breaker to one or more outlets. • Most circuits installed in homes are branch circuits. • Feeder Circuits • A circuit between the breaker box and a sub-panel.
Electrical “Load” • Electrical Load is the total amount of electrical current required. • Different types of circuits are needed to carry the load in each room. • Wiring in each circuit is protected by an overcurrent device, either a fuse or breaker. • If a circuit becomes overloaded, or a short circuit develops, the breaker will open to stop the current flow.
By providing several branch circuits within a house, it keeps costs down and allows for safe operation. • The load carrying capacity of a wire is measured in amperes and stated as ampacity. • If the ampacity is exceeded, the wire will burn and melt. • Larger wire has a higher ampacity. • Items that have higher electrical needs will require larger wire with a higher ampacity.
AWG (American Wire Gage) Ratings • All wire is given an AWG rating to describe its diameter. • The smaller the number is, the larger the wire. • No. 8 wire is larger than No. 10 but smaller than No. 6.
3 Types of Branch Circuits • General Purpose • Small Appliance • Individual Equipment
What is a General Purpose Circuit? • Makes up the largest part of the wiring system for a home. • Includes all lighting outlets and most receptacles. • Sometimes called lighting circuits. • They do supply lighting but many other items are connected to them such as vacuum cleaners, radios, televisions, etc.
The Code requires at least 1 general purpose circuit for every 500 square feet of floor space. • Either No. 12 or No. 14 wire may be used. • If No. 12 wire is used, a 15 or 20 amp breaker may be used. • If No. 14 wire is used, only a 15 amp breaker may be used.
What is a Small Appliance Circuit? • Circuits in the kitchen area to supply power to mixers, toasters, blenders, and other small appliances. • Code requires at least 2- 20 ampere small appliance circuits in a home to supply power to countertop receptacles. • Wire must be at least No.12 and protected by a 20 ampere breaker. • No lights are included on a small appliance circuit, only receptacles.
Individual Branch Circuits • A circuit that is wired directly from the breaker panel to only one appliance or piece of equipment. • It is used for items that require larger loads. • Often called a “dedicated circuit”. • Examples are: Range, central heat, A/C, water heater, garbage disposal, dishwasher.