Electrical Design and Drawings

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Electrical Design and Drawings

• Electrical Principles
• Power Distribution
• Sources Wind, water, nuclear, fossil fuel,
  solar, and geothermal.
• Transformers Used to increase electrical power
  to high voltages for transmission over long
  distances. They also decrease voltage when the
  electricity enters businesses or residential
  communities.
• The usual voltage that enters a home is 110 and
  220 volts

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Electrical Design and Drawings

• Electrical Principles
• Volt The unit of electrical pressure or
  potential. This pressure makes electricity flow
  through a wire.
• Ampere (amp) The flow of electricity is
  current. The ampere is the unit used to measure
  the magnitude of an electric current. An Amp is
  the specific quantity of electrons passing a
  point in one second.
• The current will determine the wire size.

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Electrical Design and Drawings

• Electrical Principles
• Watts The amount of power required to do work.
  (Light lamps, heat water, turn motors).
• Power (watts) is current (amps) multiplied by
  potential (volts).
• Amperes x volts watts
• Kilowatt-hour The unit used to measure the
  consumption of electrical energy.
• A Kilowatt is 1000 Watts
• A 1000-watt iron operating for one hour uses 1
  Kilowatt-hour (kWh)

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Electrical Design and Drawings

• Electrical Principles
• Insulators Wood, glass, and some plastics have
  a high resistance to electricity.
• Conductors Copper, aluminum, and silver have
  low resistance allowing electricity to flow
  freely through them.
• Wiring
• Copper
• Aluminum
• Covered with insulation

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Electrical Design and Drawings

• Electrical Principles
• Ohms The amount of electrical resistance
• IE/R
• EIR
• RE/I
• I Current (amperes)
• E Electromotive force (volts)
• R Resistance (ohms)
• RE/I
• R120/10
• R12 ohms

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Electrical Design and Drawings

• Electrical Principles
• Service Entrance
• The electrical entrance to a building
• Wires come from the utility company and connect
  to a transformer near the building. An
  electrical Drop extends from the utility pole to
  the house. See Fig. 31-1 pg. 618
• Conduit Metal tubing used for wiring.
• Grounding Electrical systems must be grounded
  through the service entrance.

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Electrical Design and Drawings

• Electrical Principles
• Service Distribution
• Service panel
• The size of the service panel is determined by
  the total load requirements (watts) of the entire
  building.
• Watts can be converted to amperes by dividing the
  total (and future) watts needed by the amount of
  voltage delivered to the distribution box.
• Watts/Volts Amperes
• W Metric symbol for watts
• V Metric symbol for volts
• A metric symbol for amperes

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Electrical Design and Drawings

• Electrical Principles
• Service Distribution
• Most residential construction requires a
  distribution panel with a capacity of 100 to 200
  amps.
• The National Electrical Code (NEC) minimum for
  new construction is 60 amps.

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Electrical Design and Drawings

• Electrical Principles
• Branch Circuits
• Electricity is routed from the distribution panel
  to the rest of the building through branch
  circuits.
• Circuit A circular path that electricity
  follows from the power supply source to a light,
  appliance, or other electrical device and back
  again to the panel. See Fig. 31-4, pg. 620
• A number of branch circuits are required in a
  building to prevent overloading a circuit.
• Circuit Breaker A device that opens
  (disconnects) a circuit when the current exceeds
  a certain amount.

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Electrical Design and Drawings

• Electrical Principles
• Branch Circuits
• If the sum of the current drawn by the branch
  circuits exceeds the rating of the main circuit
  breaker, the main breaker will trip (open). If a
  breaker trips then it must be reset.
• Three types of branch circuits
• Lighting circuits
• Small-appliance circuits
• Individual circuits

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Electrical Design and Drawings

• Electrical Principles
• Lighting Circuits
• Different lights in each room are usually on
  different circuits so that if one circuit breaker
  trips, the room will not be in total darkness.
• NEC requirements
• A minimum general lighting load of 3 watts per
  square foot of floor space.
• 100 for first 3000 watts
• 35 for the second 17,000 watts
• 25 for wattage over 120,000
• Each branch circuit can supply only 2400 watts
  (120V x 20A 2400W)

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Electrical Design and Drawings

• Electrical Principles
• Small-Appliance Circuits
• Power to outlets where small appliances are
  located.
• Toasters, electric skillets, irons, electric
  shavers, portable tools, computers, blenders,
  etc.
• NEC requires a minimum of two small-appliance
  circuits in a house. (1500-watt load)
• Individual Circuits
• Dedicated circuits. Electric ranges, water
  heaters, dryers, washers, garbage disposals,
  dishwashers, etc.

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Electrical Design and Drawings

• Electrical Principles
• Individual Circuits
• GFCI ground fault Circuit Interrupt receptacle
• Used when water source is near receptacle
• When a GFCI receptacle detects and change in
  current it immediately trips.
• Electrical Conductors
• Wires are classified by
• the wire material
• the insulation material
• the wire size

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Electrical Design and Drawings

• Electrical Principles
• Electrical Conductors
• Metered voltage is 120V and 240V, however because
  of resistance the delivered voltage is
  approximately 110V and 220V.
• 240V service entrance and circuits
• Wire sizes 6 through 2/0
• 120V and 240V lighting and small-appliance
  circuits
• Wire sizes 10 through 14
• Thermostats and doorbells
• Wire sizes 16 and 18
• See Fig 31-7 31-7B, pg 624

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Electrical Design and Drawings

• Electrical Principles
• Lighting Design
• Incandescent
• Filament type
• Fluorescent
• The central element in a fluorescent lamp is a
  sealed glass tube. The tube contains a small bit
  of mercury and an inert gas, typically argon,
  kept under very low pressure. The tube also
  contains a phosphor powder, coated along the
  inside of the glass. The tube has two electrodes,
  one at each end, which are wired to an electrical
  circuit.

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Electrical Design and Drawings

• Electrical Principles
• Light Measurements
• Footcandle (see Fig. 31-8, pg 626)
• The amount of light a candle casts on an object
  one foot away.
• Ten foot-candles (10fc) equals the amount of
  light that ten candles throw on a surface one
  foot away.
• Lux metric system of illumination
• Types of Lighting
• General
• Specific
• Decorative

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Electrical Design and Drawings

• Electrical Principles
• Types of Lighting
• Where possible, daylight should be included as
  part of the general lighting plan
• Specific Lighting
• Light directed to a location (reading, track
  lighting)
• Decorative Lighting
• Create atmosphere Bookcases, fireplaces, etc.
• Light Distribution
• Direct
• Indirect (reflected from surfaces)
• Semi-direct (Shines down but also upward)
• Semi-indirect (most reflected but some directly)
• Diffused (spread evenly in all directions)

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Electrical Design and Drawings

• Electrical Principles
• Reflection
• White surfaces can reflect 94 of the light that
  strikes them.
• Black surfaces may only reflect 2 of the light
  that strikes them with the rest absorbed.
• Light Fixtures
• Plug-in lamps
• Structural (attached to building)
• Soffit Lighting
• Wall Fixtures
• Ceiling Fixtures (see Fig. 31-16, pg 630)
• Exterior Lighting Fixtures

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Electrical Design and Drawings

• Electrical Principles
• Switches
• Single-pole switch
• Control one fixture, device, or outlet.
• Three-way
• Controls lights from two different locations.
  (Staircase, hallway, etc.)
• Location (see pg. 632)
• 4 above floor level
• Latch side of doors, no closer that 2-1/2 from
  casing.
• Use four-way switches for rooms with more that
  two exists. (see Fig. 31-22, pg 633)

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Electrical Design and Drawings

• Electrical Principles
• Outlets (Receptacles)
• Convenience receptacles
• Single, double, or multiple units
• Lighting outlets (split wire)
• Locations
• Average one every 6 of wall space.
• Kitchen is one every 4 of wall space and located
  over countertops
• Hallway outlets are every 15
• No further than 6 from each room corner when
  possible.

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Electrical Design and Drawings

• Electrical Principles
• Outlets (Receptacles)
• An outlet should be placed on any wall between
  doors regardless of space.
• Outlet height is 12 to 18 from the floor
• Countertop heights are normally 4 above the
  floor line.
• At lease one outlet should be placed above each
  bathroom countertop. A minimum of two outlets
  should be in each bathroom.
• An outdoor weatherproof outlet should be provided
  on each side of a house.

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Electrical Design and Drawings

• Electrical Drawings
• Symbols
• See Fig. 31-25, pg. 635 637
• Place electrical symbols on a floor plan that
  contains only the wall outlines (abbreviated
  floor plan)
• Place the electrical symbols on the floor plan at
  the proper locations.
• Switches
• Light Fixtures
• Special Purpose Receptacles

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Electrical Design and Drawings

• Electrical Drawings
• Symbols
• Connect the switches to fixtures or devices by
  drawing a dashed spline from each switch to the
  outlet, fixture, or device that the switch
  controls.
• This line shows connectivity, not actual wiring.

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Electrical Design and Drawings

• Electrical Drawings

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Electrical Design and Drawings

• Electrical Drawings

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Electrical Design and Drawings

• Electrical Drawings