Electrical Wiring Residential

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Electrical Wiring Residential

• Unit 6
• Ground Fault Circuit Interrupters and Similar
  Devices

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The GFCI Receptacle
Shown in Graphic 15A GFCI Recept. (L) 20A GFCI
Recept. (R) Note difference in plug
configuration in 20A device.
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What A GFCI Does

1. A GFCI monitors the current balance between the
   ungrounded (hot) conductor and the grounded
   (neutral) conductor.
2. When the current flowing through the (hot)
   conductor is in the range of 4-6 milliamps more
   than the current flowing in the (grounded) return
   path conductor, the GFCI senses this unbalance
   and trips. (opens the circuit)

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GFCIs In Residential Circuits

• A GFCI will operate properly only on grounded
  electrical systems. They will operate in the
  absence of a true equipment ground since the
  neutral is a grounded conductor.
• Other important considerations
• Never ground a system neutral conductor at any
  point past the location of the main service
  equipment.
• Never connect the neutral of one circuit to the
  neutral of another circuit.

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GFCIs In Residential Circuits (cont.)

• Warning If the line and load connections on a
  GFCI receptacle are reversed, newer GFCIs will
  not permit you to energize the outlet. On older
  GFCIs, the load circuit will shut off when the
  GFCI trips, but the GFCI device will remain
  live and provide no protection.
• When hooking up GFCIs, never share a neutral
  such as when using a multi-wire branch-circuit.
  The GFCI will not work. In my own experience with
  multi-wire circuits, a GFCI pigtailed to the line
  side terminals only on a multi-wire
  branch-circuit, will still operate correctly.

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Internal Diagram
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What A GFCI Does Not Do

1. It does not protect against electric shock when a
   person comes into contact with both circuit
   conductors at the same time, because the current
   flowing through both conductors is the same.
   There is no unbalance for the GFCI to detect.
2. It does not limit the amount of ground-fault
   current. It does limit the length of time that a
   ground fault will flow. The severity of the
   shock remains the same, but the duration is
   limited.

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What A GFCI Does Not Do

1. It does not sense solid short-circuits between
   the hot and neutral conductor. The branch-circuit
   fuse or circuit breaker provides this protection.
2. It does not provide overload protection for
   branch-circuit wiring. Once again, this is
   handled by the overcurrent device. (Fuse or
   circuit breaker)

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Electrical Hazards
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Effect Of Electric Shock
This Could Be You!!!!!
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GFCIs In Residential Circuits

1. It is up to the electrician to decide how the
   provide the required GFCI personnel protection
   based on NEC Art. 210.8.
2. They can be wired at individual outlet points
   (line side only), or wired as feed-through
   devices (line/load wiring), to protect other
   outlets connected to the load terminals.
3. Swimming pools have special requirements for GFCI
   protection and those are covered in NEC Art. 680.

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Sample Layout
Here, one GFCI receptacle is protecting several
other devices downstream.
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NEC 210.8 Requirements
See Handout

• 210.8 Ground-Fault Circuit-Interrupter Protection
  for Personnel.
• FPN See 215.9 for ground-fault
  circuit-interrupter protection for personnel on
  feeders.
• Dwelling Units. All 125-volt, single-phase, 15-
  and 20-ampere receptacles installed in the
  locations specified in (1) through (8) shall have
  ground-fault circuit-interrupter protection for
  personnel.
• Bathrooms
• (2) Garages, and also accessory buildings that
  have a floor located at or below grade level not
  intended as habitable rooms and limited to
  storage areas, work areas, and areas of similar
  use

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NEC 210.8(2) Exceptions
Exception No. 1 to (2) Receptacles that are not
readily accessible. Exception No. 2 to (2) A
single receptacle or a duplex receptacle for two
appliances located within dedicated space for
each appliance that, in normal use, is not easily
moved from one place to another and that is
cord-and-plug connected in accordance with
400.7(A)(6), (A)(7), or (A)(8). Receptacles
installed under the exceptions to
210.8(A)(2) shall not be considered as meeting
the requirements of 210.52(G)
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NEC 210.8(3) (4)
(3) Outdoors Exception to (3) Receptacles that
are not readily accessible and are supplied by a
dedicated branch circuit for electric
snow-melting or deicing equipment shall be
permitted to be installed in accordance with
426.28. (4) Crawl spaces at or below grade
level
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NEC 210.8(5)
(5) Unfinished basements for purposes of this
section, unfinished basements are defined as
portions or areas of the basement not intended as
habitable rooms and limited to storage areas,
work areas, and the like. Exception No. 1 to
(5) Receptacles that are not readily accessible.
Exception No. 2 to (5) A single receptacle or a
duplex receptacle for two appliances located
within dedicated space for each appliance that,
in normal use, is not easily moved from one place
to another and that is cord-and-plug connected in
accordance with 400.7(A)(6), (A)(7), or (A)(8).
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NEC 210.8(5) Ex. 3
Exception No. 3 to (5) A receptacle supplying
only a permanently installed fire alarm or
burglar alarm system shall not be required to
have ground-fault circuit-interrupter
protection. Receptacles installed under the
exceptions to 210.8(A)(5) shall not be considered
as meeting the requirements of 210.52(G).
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NEC 210.8(6), (7), (8)
(6) Kitchens where the receptacles are
installed to serve the countertop surfaces (7)
Laundry, utility, and wet bar sinks where the
receptacles are installed within 1.8 m (6 ft) of
the outside edge of the sink (8) Boathouses
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The Feed-through GFCI Receptacle
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The Feed-through GFCI Receptacle
Here the GFCI only protects itself and the
outlets connected to the load terminals.
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The End-of-Line GFCI Receptacle
Here the GFCI only protects itself. The same
result is accomplished by pigtailing the hots and
neutrals and connecting the pigtails to the line
terminals.
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Replacement Of Existing Receptacles
(D) Replacements. Replacement of receptacles
shall comply with 406.3(D)(1), (D)(2), and (D)(3)
as applicable. (1) Grounding-Type Receptacles.
Where a grounding means exists in the receptacle
enclosure or a grounding conductor is installed
in accordance with 250.130(C), grounding-type
receptacles shall be used and shall be connected
to the grounding conductor in accordance with
406.3(C) or 250.130(C).
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Replacement Of Existing Receptacles
(2) Ground-Fault Circuit Interrupters.
Ground-fault circuit-interrupter protected
receptacles shall be provided where replacements
are made at receptacle outlets that are required
to be so protected elsewhere in this Code. (3)
Nongrounding-Type Receptacles. Where
grounding means does not exist in the receptacle
enclosure, the installation shall comply with
(D)(3)(a), (D)(3)(b), or (D)(3)(c). (a) A
nongrounding-type receptacle(s) shall be
permitted to be replaced with another
nongrounding-type receptacle(s).
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Replacement Of Existing Receptacles
(b) A nongrounding-type receptacle(s) shall be
permitted to be replaced with a ground-fault
circuit interrupter-type receptacle(s). These
receptacles shall be marked No Equipment
Ground. An equipment grounding conductor shall
not be connected from the ground-fault circuit
interrupter- type receptacle to any outlet
supplied from the ground-fault circuit-interrupter
receptacle.
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Replacement Of Existing Receptacles
(c) A nongrounding-type receptacle(s) shall be
permitted to be replaced with a grounding-type
receptacle(s) where supplied through a
ground-fault circuit interrupter. Grounding-type
receptacles supplied through the ground-fault
circuit interrupter shall be marked GFCI
Protected and No Equipment Ground. An
equipment grounding conductor shall not be
connected between the grounding type receptacles.
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Replacement Of Existing Receptacles
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GFCIs For Temporary Wiring

1. All 125V., 15-,20-,and 30-ampere receptacles that
   are not part of the permanent building and that
   will be used by workers on a construction site
   must be GFCI protected.
2. Receptacle outlets that are part of the actual
   permanent wiring of a building and are used by
   personnel for temporary power are also required
   to be GFCI protected.

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GFCIs For Temporary Wiring

1. Portable GFCI devices are available with manual
   reset, which is useful should a power outage
   occur of if the GFCI is unplugged, so that
   equipment will not start up again when power is
   restored.
2. There are portable devices that will reset
   automatically. These are useful for lighting,
   engine heaters, sump pumps, and other equipment
   that may be unattended should power be
   interrupted.

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2 Types of Portable GFCIs
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Immersion Detection Circuit Interrupters (IDCIs)

• These devices are often identifiable as the large
  plug caps on personal grooming appliances such as
  hair dryers and curling irons.
• These devices are for protection of personnel
  should a grooming appliance be dropped in a sink
  or tub full of water.
• An IDCI is required to open the circuit
  regardless of whether the appliance switch is the
  on or off position.

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Immersion Detection Circuit Interrupters (IDCIs)

• Like a GFCI, an IDCI must open the circuit when
  the sensor detects a leakage current to ground in
  the range of 4-6 mA.
• An IDCI protected appliance can be plugged into a
  GFCI receptacle which will give you double
  protection.

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Arc-Fault Circuit Interrupters (AFCIs)

1. Electrical arcing is one of the leading causes of
   electrical fires in homes.
2. The temperature of an arc can reach 10,000ºF or
   more. Remember, an electrical arc is hotter than
   the surface of the sun.
3. Arcing faults can be line-to-line,
   line-to-neutral, or line-to-ground. Electrical
   arcing is considered an early event in the
   progression of a typical electrical fire.

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How Does An AFCI Work

• When arcing occurs between the black hot
  conductor and the white grounded neutral
  conductor, or between the black hot conductor
  and ground, it is referred to as a parallel arc.
• This can be caused from a nail being driven
  through a wire, or even if wires are stapled too
  tightly.
• Branch/Feeder AFCI Installed at the panel.
  Protects the branch-circuit wiring.
• Outlet/Feedthrough AFCI Some AFCIs are
  available that can sense upstream as well as
  downstream arcing in the branch-circuit.
  Unfortunately, these are not yet in production.

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How Does An AFCI Work?

1. An AFCI is designed to sense the rapid
   fluctuations of current flow typical of an arcing
   condition.
2. Once again, never share the neutral of a
   multi-wire branch-circuit when wiring GFCIs or
   AFCIs.

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Transient Voltage Surge Suppressors (TVSSs)

• Voltage transients, called surges or spikes, can
  stress, damage, or otherwise destroy electrical
  and electronic components.
• These surges can cause loss of memory or freezes
  of microprocessors.
• Voltage transients cause abnormal current to flow
  through the sensitive electronic components. This
  energy is measured in joules.
• A joule is the unit of energy when 1 ampere of
  current passes through a one ? resistance for a
  period of one second.

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Transient Voltage Surge Suppressors (TVSSs)

1. Line surges can be line-to-neutral,
   line-to-ground, and line-to-line.
2. TVSS devices are available in plug-in strips and
   as part of a desktop computer hardware backup
   power unit (UPS - Uninterruptible power supply)
3. A TVSS on a branch-circuit will provide surge
   suppression for all of the receptacles on the
   same circuit.

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Transient Voltage Surge Suppressors (TVSSs)

1. Whole-House surge protectors are available that
   offer surge suppression for the entire house.
   When whole-house surge protectors are installed,
   it is still a good idea to install spot location
   surge protectors to more closely protect against
   low-level surges at the computer or other
   delicate electronic equipment.

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Noise

1. Noise is recognized as snow on a TV screen, or
   static on a radio or telephone.
2. Noise comes from electromagnetic interference
   (EMI) and radio frequency interference (RFI).
3. Undesirable noise can be reduced by reducing the
   number of ground reference points on a system.
   This can also be done by installing an isolated
   ground receptacle (IGR). These are often seen in
   hospitals and other locations with highly
   sophisticated electronic equipment critical to
   security and/or life-support.