Electrical Wiring

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Electrical Wiring

• Lesson 1
• Understanding Circuits

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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.

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• 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.

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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.

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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.

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• 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.

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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.

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3 Types of Branch Circuits

• General Purpose
• Small Appliance
• Individual Equipment

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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.

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• 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.

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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.

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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.