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Introduction to Electrical Design

Day 3

Calculations

Journey of Electricity

Wiring Three Way Switch

This Photo by Unknown Author is licensed under CC BY

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Unit EQ:

How would you determine if an electrical system is wired properly?

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Lesson EQ:

How can you determine the proper wiring scheme for a three-way switch?

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Lesson Objectives

The student will be able to:

  1. Compare and contrast volts, amperage, watts, and ohms
  2. Interpret an electricity bill and determine the cost of usage
  3. Explain how electrical energy travels from the power plant to the consumer
  4. Differentiate between gauges of wire
  5. Construct a three-way switch model

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Review

  • Draw and label the following parts for each of the following circuits:
    • Part: load, wire, source, switch
    • Circuit: open, closed, short, parallel, series
  • Draw, label and color coded the proper wiring diagram for a single pole switch and a duplex receptacle
    • Parts that should be color: wire and screws
    • Labels: single-pole switch, keyless lamp holder, duplex receptacle, gauge/type of wire

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Measurements

Watts (W)

Amperes (Amps)

Volts (E)

Ohms (Ω)

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Measurements

  • Amperes (Amps)
    • Rate of flow of electricity in a conductor
    • Number of electrons that pass a given point in 1 second
  • Watts (W)
    • Amount of energy or work that can be done by amps and volts
    • Unit of power equal to 1 Joule per second that is used to quantify energy transfer
  • Voltage (E) / Volts (V)
    • Measure of electrical pressure
    • Potential energy used to move electrons between two points
  • Ohms (Ω)
    • A unit of measure that represents electrical resistance

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Equations

Watts = Volts x Amps

West Virginia (WVA)

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Example: If a 200-watt light bulb operates at 120 volts, it will draw how many amps of electricity?

200 = 120 / A

A = 200/120

A = 1.67

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Equations – Your Turn

Watts = Volts x Amps

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Example: If a 60 watt light bulb operates at 120 volts, it will draw how many amps of electricity?

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60 = 120 x A

A = 60 / 120

A = 0.5

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Ohm Ω

  • Electrical resistance unit
  • Electrical Resistance
    • Ability of a material to oppose electron flow in an electrical circuit
  • Equal to the resistance when 1 A of current is driven by 1 V
  • Higher Resistance
    • Lower Current
  • Lower Resistance
    • Higher Current

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Ohm’s Law Ω

  • Relationship between E, I, and R
    • E (voltage), I (current), R (resistance)
  • States:
    • If voltage in a circuit remains constant, current in a circuit decreases with and increase in resistance, and current in the circuit increases with a decrease in resistance
    • If the resistances in a circuit remains constant, a change in current is directly proportional to the change in voltage

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Ohm’s Law Ω

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Ohm’s Law

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How Does Electrical Power Get to Us?

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Video

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Electric’s Journey

  1. Power Plant (coal, water, nuclear)
  2. Substation
  3. High Voltage Transmission Lines
  4. Power substation
  5. Power poles with transformers
  6. Transformer drum
  7. Meter
  8. Breaker Box
  9. Light/Receptacle

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Electric’s Journey

  • Power from electric company = high voltages (power)
  • Transformers: drop volts from 25,000 volts (substation) or 7,200 (outside house) to 240 volts (enters house

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Service Entrance

  • Service Entrance Head: provides weatherproof entrance of the service cable
  • Electrical meter: measures electrical usage in KWHR

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Power Bills

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My Electric Power Bill

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Kilowatt Hours

 

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Kilowatt Hours => Watt Hours

  • Kilo = 1000
  • 1 Kilowatt = 1000 watts

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Calculation Worksheet

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Wire Gauges and Types

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Gauge of Wire

  • Smaller number = thicker wire
  • Larger number = thinner wire

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Wire Gauge

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Wire

14 -2 ground

Number of other wires

Gauge of Wire

Ground Wire is included

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Selecting a Cable

  • Single Pole Switch: 14 -2 ground
  • Three-Way Switch: 14-3 ground
  • Duplex Receptacle: 14-2 ground

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Hint: how many screws are there to attach wire to a fixture? White always goes straight to the light

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3-Way Switch Wiring Demonstration

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Proper Steps

  1. Secure the power source cable and Romex wire in the metal box
  2. Using cable rippers, remove approximately 6 inches of the outside plastic sheath of the Romex and power source cable
  3. Separate the wires and papers
  4. Using the diagonal cutting or linemen’s pliers cut the paper/plastic sheath
  5. Using the wire strippers remove approximately 1 in of the plastic sheath on each of the wires

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5 Simple Three-Way Switch Wiring Rules

  1. Black from power source to common terminal on 1st switch
  2. Black from light connects to common on last switch
  3. Connect traveler wires
    • Red and Black between switches
  4. Connect white wire to light receptacles
    • White straight to the light
  5. Connect grounds

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Direction Matters!

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5 Simple Three-Way Switch Wiring Rules

  1. Black from power source to common terminal on 1st switch
  2. Black from light connects to common on last switch
  3. Connect traveler wires
    • Red and Black between switches
  4. Connect white wire to light receptacles
    • White straight to the light
  5. Connect grounds

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Your Turn

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Lesson Objectives

The student will be able to:

  1. Compare and contrast volts, amperage, watts, and ohms
  2. Interpret an electricity bill and determine the cost of usage
  3. Explain how electrical energy travels from the power plant to the consumer
  4. Differentiate between gauges of wire
  5. Construct a three-way switch model

​

38 of 38

Introduction to Electrical Design

Day 3

Calculations

Journey of Electricity

Wiring Three Way Switch

This Photo by Unknown Author is licensed under CC BY