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30

Chapter

Electrical Wiring

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Objectives

  • Define basic electrical terms.
  • Explain what is included in an electrical wiring system.
  • List the tools, devices, and materials required to do electrical wiring in a residential building.
  • Demonstrate the proper use of tools and handling of materials.

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Objectives (Cont.)

  • Demonstrate an understanding of basic circuit theory.
  • Use approved methods for simple wiring installation tasks.
  • Perform simple electrical troubleshooting.
  • Describe the components of a home security alarm system.

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Mechanical Systems

  • Building is constructed and closed in
  • Then mechanical systems are installed
    • Electrical wiring
    • Plumbing
    • Heating/ventilating/air conditioning (HVAC)
  • Electricity can be extremely dangerous
  • Qualified electrician must install electrical wiring according to national and local codes

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Tools and Equipment

  • Proper tools, equipment, and materials are essential when installing electrical wiring
    • Hammers
    • Saws and wood chisels
    • Pliers
    • Tape measures
    • Circuit testers

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Electrical System Components

  • Circuit is path through which current flows
  • Conductors are wires that carry current
  • Boxes and box covers enclose devices that control electric current
  • Circuit breakers and fuses protect conductors from overload

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Ground-Fault Circuit Interrupter

  • Safety device installed as protection against electrical shock
  • May be built into circuit breakers or receptacles
  • Required by electrical code for some areas of home

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Arc-Fault Circuit Interrupter

  • Electrical safety device helps prevent houses from catching fire
  • Monitors circuit and detects erratic forms of current
  • Detects arcing and stops all current before fire is started

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Switches and Receptacles

  • Various types are used in residential and light commercial applications
  • Switches control current to lights and appliances
  • Receptacles (outlets) allow connection of appliances and lights to circuits

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Conduits

  • Pipes or enclosed channels through which conductors are run
  • Made of steel or PVC rigid tubing
  • Lengths can be cut and bent to fit space
  • Wire nuts form sound connection between conductors

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Basic Electrical Wiring Theory

  • Electricity is generated when metal conductor is passed through magnetic field
  • Alternating current (ac) is form of electric current found in homes
  • Direct current (dc) is another form used for other purposes

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Electric Power Stations

  • Alternating current is generated at electric power stations
  • It travels through transmission lines
  • Transformers are used to increase or decrease voltage

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Kinds of Transformers

  • Substations serve whole areas, such as towns
  • Distribution transformers serve one residence or group
  • Small transformers are used within houses to reduce current
  • Service brings electricity to residence

Dauphin Island

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Safety Note

  • Electrical current can be extremely dangerous
    • Make certain circuit is off before working on it
    • Use only tools with insulated handles
    • Remove all jewelry and other metal objects
    • Keep work areas dry and clean
    • Wear rubber boots or rubber-soled shoes
    • Use only wood or fiberglass ladders
    • Wear safety glasses when using striking tools

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Installing Service

  • Electrical service consists of conductors that bring power from transformer to building
  • Entrance panel houses main breaker and circuit breaker or fuse for each of home’s circuits

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Three-Wire Service to Building

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Ground Faults

  • When current-carrying conductor contacts path to ground, ground fault occurs
  • Person coming in contact with unintended current path may get dangerous shock
  • Proper grounding will minimize possibility of short circuit causing shock
  • In properly grounded circuit, every device is connected to ground

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Grounding

  • Conductors or ground wire provide path for current to neutral bar in service panel
  • Neutral bus bar is connected to grounding bus bar in service panel
  • Grounding completed by connecting grounding bus bar to grounding electrode

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Reading Prints

  • Symbols on electrical prints show conductors and devices to install at each location
  • Electrical print symbols are standardized
  • Electrician may draw wiring layout for each room

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Circuit Path

  • Circuit is path from source of power, through energy-using devices, back to power source

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Running Branch Circuits

  • Branch circuits include all loads on one run of conductors
  • Conductors are run to each box and securely connected
  • Electrical cables must be securely fastened to framing members

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Device Wiring

  • To connect wires to one another
    • Strip several inches of jacket away
    • Strip insulation from about 5/8″ of conductors
    • Twist bare wires together
    • Install wire nut around twisted wires

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Connecting Switches

  • Terminal connections are usually screws
  • Screws are tightened to grip conductors
  • Single pole switch is simple to wire
  • Three-way and four-way switches can be more complicated

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Connecting Receptacles

  • Receptacles allow transfer of electrical energy from circuit conductors to devices
  • Hot wire is attached to copper-colored terminal
  • Neutral (white) wire is attached to lighter, silver-colored terminal

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Electrical Troubleshooting

  • Problems often involve
    • Receptacles, switches
    • Lighting fixtures
    • Circuit breakers, fuses
  • Complex problems
    • Open circuits
    • Broken conductors
    • Voltage fluctuation
    • Ground faults

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Testing Receptacles

  • Insert leads of circuit tester into receptacle
  • If tester does not light, check line conductors
  • Check for voltage at terminals of receptacle
  • Test for open neutral
  • Check other receptacles on circuit

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Testing Fixtures

  • Check to see that switch is on
  • Place probes of circuit tester onto supply conductors
  • If tester lights, voltage is present
  • Repair or replace fixture

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Home Security and Automation Wiring

  • Installing wiring is most efficient when walls are still open
  • Most installations are done in new homes or as part of major remodeling projects
  • Building “smart houses” with advanced communication and automation features is growing trend

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Home Security Installation

  • Installation of home security system wiring is relatively simple
  • System typically includes phone connection to monitoring agency or police and fire stations

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Home Automation Wiring

  • More complex than home security installation
  • Wiring distribution panels and runs of multiple cables are used
  • Several types of wiring are used
    • Twisted-pair cables
    • Shielded coaxial cable
    • Fiber optic cables
  • Specialized subcontractors usually install security system wiring and structured wiring

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General Considerations

  • Install structured wiring after electrical and plumbing work are done
  • Set up all wiring as home runs
  • Place distribution panel in accessible location
  • Use two or more distribution panels in larger homes
  • Carefully label every cable in panel

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Construction Careers �Electricians

  • Install electrical systems in new or existing structures
  • Work in construction or maintenance roles
  • Learn by completing apprenticeship and on-job training

Lisa F. Young/Shutterstock

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