Electrical Principles and Wiring Materials

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Electrical Principles and Wiring Materials
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Principles of Electricity

• Electricity is a form of energy that can produce
  light, heat, magnetism, chemical changes
• Resistance tendency of a material to prevent
  electrical flow
• Conductor if electricity flows easily
• Insulator material that provides great resistance

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Common Terms

• Amperes measure of the rate of flow of
  electricity in a conductor
• Volts measure of electrical pressure
• Watts measure of the amount of energy or work
  that can be done
• Ohms measure of electrical resistance to flow
• Cable two or more conductors (wires) grouped in
  a single unit by a protective sheath
• Circuit path through which electrical current
  flows
• Circuit Breaker safety device that provides
  overcurrent protection for a circuit

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Common Terms

• Conductor safety device used to control the
  flow of electricity in a circuit
• Current movement of electrons through an
  electrical conductor
• Grounding Conductor conductor (wire) which
  transmits electrical current to the earth in
  event of a short circuit
• Grounded Circuit Conductor conductor, white in
  color, that returns current under zero pressure
  from the load to the power source.
• Load electrical equipment and devices connected
  to an ungrounded conductor

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Common Terms

• Ground Fault Circuit Interrupter (GFCI) device
  that provides protection against shock from a
  short circuit
• Hot Conductor ungrounded conductor that carries
  electrical current to the load
• Neutral Conductor conductor that carries only
  the ampere imbalance between two ungrounded
  conductors

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Common Terms

• Outlet point on the circuit at which current is
  utilized for receptacles, switches, appliances,
  lighting, etc.
• Receptacles device that allows access to a
  circuit by plu-in
• Pigtail short wire (conductor) used for
  connecting two or more conductors to a single
  screw terminal on a receptacle. Also a jumper

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Ohms Law

• Ohm R
• Volts E
• Amps I
• Ohms Law E IR
• IE/R
• RE/I

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Electrical Safety

• Shock and Fire
• Never disconnect any safety device
• Dont touch electrical items with wet hands or
  feet
• Dont remove ground plug prong
• Use GFI in wet areas
• Discontinue use of extension cord that feels warm
• Dont put extension cords under carpet

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Electrical Safety

• Install wiring according to NEC
• Blown fuse or breaker, determine cause
• Dont replace fuse with larger fuse
• Dont leave heat producing appliances unattended
• Heaters lamps away from combustibles
• Dont remove back of TV (30,000v when off)
• Electric motors lubricated, free of grease etc.

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Electrical Safety

• Keep appliances dry
• Dont use damaged switches, outlets, fixtures,
  extension cords
• Follow manufacturers instructions for
  installation and use of electrical equipment

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Parts of a Circuit

• Service Entrance
• Electric Meter
• Service Entrance Panel (SEP)
• Sub-panel
• Circuit Breakers
• Switches
• Receptacles
• Electrical Cables/Conductors

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Service Entrance

• Power from from power company
• Transformer drops volts from 25,000 volts to 240
  volts
• Service drop wires etc from transformer to house
• Entrance head weather-proof at house
• Meter
• Service Entrance Panel (SEP) box with fuses or
  breakers

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Electric Meter

• Kilowatthours how electricity is sold
• Kilo 1000
• Watthour use of 1 watt for one hour
• 100 watt light bulb for 1 hour - 100 watthours
• Kilowatthour 1000 watts for one hour

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Types of Basic Circuits

• Branch
• Feeder

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Branch Circuits

• Usually begin at Service Entrance Panel (SEP) and
  supply power to all parts of floor-plan.
• Branch out from a circuit breaker to a variety of
  circuits that include outlets such as lights,
  receptacles, etc.
• Will have several branch circuits which is more
  efficient
• Use of correct size wire and circuit protection
  is required
• Contains main circuit breaker

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Feeder Circuits

• Circuit that runs between the SEP and a
  sub-panel.
• Could also start at a generator or battery
• Guards against voltage drop
• May or may not be equipped with main circuit
  breaker

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Types of Branch Circuits

• General Purpose
• Small Appliance
• Individual Equipment

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General Purpose

• Major portion of circuits
• Include lighting outlets, and most convenience
  receptacles
• Typical wire size used is either No. 14 AWG or
  No. 12 AWG (American Wire Gauge, pp 72-75)
• Typically require 15-amp and 20 amp over-current
  protection devices (breakers or fuses)

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Small Appliance Branch Circuits

• Generally used to supply power to kitchen
  counter tops and dining room areas
• Minimum wire No. 12-2 AWG with ground
• 20-amp circuit breaker
• Outlets other than specified by NEC are not
  permitted on small appliance circuits.

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Individual Equipment Circuits

• Dedicated circuits that supply power to only
  one appliance
• Typically require 240-volts or a combination of
  120/240-volts
• Typically require larger size conductors
  (cables/wire)
• Require larger size over-current protection

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Individual Equipment Circuits

• Exceptions
• Garbage disposals, dishwashers, trash compacters,
  some room air conditioners, and refrigerators
  require only 120-volt circuits with No. 12 AWG
  conductors and 20-amp circuit breakers.

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Bathroom Circuits

• NEC requires bathrooms be served by a
  designated special 20-amp circuit.
• All bathroom receptacles must be GFCI protected
• NEC allow for 2 bathrooms to be on one circuit
  but it may be best to have each bathroom on a
  separate circuit.

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Types of Cable

• Nonmetallic sheathed cable copper or aluminum
  wire covered with paper, rubber, or vinyl for
  insulation
• Armored cable flexible metal sheath with
  individual wires inside. Wires are insulated
• Conduit tubing with individually insulated wires

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Wire Type and Size

• copper
• No 14 (14 gauge) 15 amp circuits
• No 12 20 amps
• No 10 30 amps
• aluminum use one size larger
• lower gauge number larger wire
• No 8 and larger use bundles of wires
• current travels on outer surface of wire, so a
  bundle of smaller wires can carry more

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Voltage Drop

• loss of voltage as it travels along a wire
• lights dim, motors overheat
• larger wires have less voltage drop for a given
  amount of current
• longer wire greater problem
• must increase wire size as distance increases

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Wire Identification

• Type of outer covering, individual wire covering,
  cable construction, number of wires
• Wire type stamped on outer surface

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Wire Identification

• Color coded black, red, blue positive or hot
  wires which carry current to appliances
• White neutral wires carry current from
  appliance back to source
• Green or Bare ground all metal boxes and
  appliances

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Wire Identification

• Wire Size 12-2 has two strands of No. 12 wire
  (black white)
• 12-2 w/g same, with one green or bare
• 12-3 has three strands of No. 12 (black, red,
  white)
• 12-3 w/g same, with green or bare

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Wire Types

• Type T - dry locations
• Type TW - dry or wet
• THHN - dry, high temps
• THW and THWN - wet, high temps
• XHHW - high moisture heat resistance
• UF - direct burial in soil but not concrete