Transcript Electrical Wiring Residential

Electrical Wiring Residential
Unit 6
Ground Fault Circuit
Interrupters and Similar
Devices
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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GFCI’s In Residential Circuits
3) 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.
4) 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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GFCI’s In Residential Circuits (cont.)
•
Warning: If the line and load connections on a
GFCI receptacle are reversed, newer GFCI’s will
not permit you to energize the outlet. On older
GFCI’s, the load circuit will shut off when the
GFCI trips, but the GFCI device will remain “live”
and provide no protection.
•
When hooking up GFCI’s, 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 branchcircuit, 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
3) It does not sense solid short-circuits between the
hot and neutral conductor. The branch-circuit fuse
or circuit breaker provides this protection.
4) It does not provide overload protection for branchcircuit 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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GFCI’s 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.
(A) Dwelling Units. All 125-volt, single-phase, 15- and 20ampere receptacles installed in the locations specified in (1)
through (8) shall have ground-fault circuit-interrupter
protection for personnel.
(1) 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
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similar use
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) Non–grounding-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 non–grounding-type receptacle(s) shall be permitted
to be replaced with another non–grounding-type receptacle(s).
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Replacement Of Existing Receptacles
(b) A non–grounding-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 non–grounding-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 groundfault 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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GFCI’s 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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GFCI’s For Temporary Wiring
3) 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.
4) 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 GFCI’s
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Immersion Detection Circuit
Interrupters (IDCI’s)
1) 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 (IDCI’s)
2) 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.
3) 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 (AFCI’s)
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:
1) 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.
2) 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 AFCI’s 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?
3) An AFCI is designed to sense the rapid fluctuations
of current flow typical of an arcing condition.
4) Once again, never share the neutral of a multi-wire
branch-circuit when wiring GFCI’s or AFCI’s.
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Transient Voltage Surge Suppressors
(TVSS’s)
1) Voltage transients, called surges or spikes, can
stress, damage, or otherwise destroy electrical and
electronic components.
2) These surges can cause loss of memory or freezes
of microprocessors.
3) 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 Ω resistance for a
period of one second.
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Transient Voltage Surge Suppressors
(TVSS’s)
4) Line surges can be line-to-neutral, line-to-ground,
and line-to-line.
5) TVSS devices are available in plug-in strips and as
part of a desktop computer hardware backup power
unit (UPS - Uninterruptible power supply)
6) 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
(TVSS’s)
7) “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.
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