Electrical Wiring ResidentialElectrical Wiring Residential

Unit 6Ground Fault Circuit

Interrupters and Similar Devices

Unit 6Ground Fault Circuit

Interrupters and Similar Devices

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The GFCI ReceptacleThe 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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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)

What A GFCI DoesWhat A GFCI Does

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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.

GFCI’s In Residential CircuitsGFCI’s In Residential Circuits

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• 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 branch-circuit, will still operate correctly.

GFCI’s In Residential Circuits (cont.)GFCI’s In Residential Circuits (cont.)

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Internal DiagramInternal Diagram

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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.

What A GFCI Does Not Do

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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 branch-circuit wiring. Once again, this is handled by the overcurrent device. (Fuse or circuit breaker)

What A GFCI Does Not DoWhat A GFCI Does Not Do

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Electrical HazardsElectrical Hazards

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Effect Of Electric Shock

Effect Of Electric Shock

This Could Be You!!!!!

This Could Be You!!!!!

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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.

GFCI’s In Residential Circuits

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Sample LayoutSample Layout

Here, one GFCI receptacle is protecting several other devices downstream.

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NEC 210.8 RequirementsSee Handout

NEC 210.8 RequirementsSee 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 20-ampere 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 similar use

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NEC 210.8(2) ExceptionsNEC 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 of210.52(G)

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NEC 210.8(3) & (4)NEC 210.8(3) & (4)

(3) Outdoors

Exception to (3): Receptacles that are not readily accessibleand are supplied by a dedicated branch circuit forelectric 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)NEC 210.8(5)

(5) Unfinished basements — for purposes of this section,unfinished basements are defined as portions or areas of thebasement not intended as habitable rooms and limited tostorage areas, work areas, and the like.

Exception No. 1 to (5): Receptacles that are not readilyaccessible.

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. 3NEC 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 of210.52(G).

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NEC 210.8(6), (7), & (8)NEC 210.8(6), (7), & (8)

(6) Kitchens — where the receptacles are installed to servethe countertop surfaces

(7) Laundry, utility, and wet bar sinks — where the receptacles are installed within 1.8 m (6 ft) of the outsideedge of the sink

(8) Boathouses

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The Feed-through GFCI Receptacle

The Feed-through GFCI Receptacle

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The Feed-through GFCI ReceptacleThe 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 ReceptacleThe 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 groundingmeans exists in the receptacle enclosure or a groundingconductor is installed in accordance with 250.130(C),grounding-type receptacles shall be used and shall beconnected 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-faultcircuit-interrupter protected receptacles shall be providedwhere replacements are made at receptacle outlets that arerequired to be so protected elsewhere in this Code.

(3) Non–grounding-Type Receptacles. Where groundingmeans does not exist in the receptacle enclosure, the installationshall comply with (D)(3)(a), (D)(3)(b), or (D)(3)(c).

(a) A non–grounding-type receptacle(s) shall be permittedto 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 ground-fault circuit interrupter shall be marked “GFCI Protected”and “No Equipment Ground.” An equipment groundingconductor shall not be connected between the grounding type receptacles.

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Replacement Of Existing Receptacles

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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.

GFCI’s For Temporary WiringGFCI’s For Temporary Wiring

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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.

GFCI’s For Temporary WiringGFCI’s For Temporary Wiring

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2 Types of Portable GFCI’s2 Types of Portable GFCI’s

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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.

Immersion Detection Circuit Interrupters (IDCI’s)

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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.

Immersion Detection Circuit Interrupters (IDCI’s)

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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.

Arc-Fault Circuit Interrupters (AFCI’s)Arc-Fault Circuit Interrupters (AFCI’s)

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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.

How Does An AFCI Work:How Does An AFCI Work:

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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.

How Does An AFCI Work?How Does An AFCI Work?

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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.

Transient Voltage Surge Suppressors (TVSS’s)

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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.

Transient Voltage Surge Suppressors (TVSS’s)

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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.

Transient Voltage Surge Suppressors (TVSS’s)

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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.

NoiseNoise