Electrical Theory Week 3

The word "bathroom" is defined in NEC Article 100 as an area including a sink (basin) with one or more of the following: a toilet, a urinal, a tub, a shower, a bidget, or similar plumbing fixtures.

Bathroom (A)(1)

Some circuits of less than ____ volts must be grounded according to 250.20(A)

50

All AC systems (with few exceptions) of _______ volts that supply premises wiring are required to be grounded.

50 to 1000

Voltages ___ volts and _______ are considered lethal.

50, greater

It does not provide overload protection for the branch-circuit wiring, it provides ___________.

ground-fault protection only

If the circuit is supplied by a transformer where the primary supply is _________.

ungrounded

GFCI circuit breakers break only the ___________ conductor

ungrounded ("hot")

A GFCI monitors the current balance between?

ungrounded (hot) conductor and the grounded conductor.

If the circuit is supplied by a transformer where the primary exceeds ______ volts to ground

150

Arc-Fault Circuit Interrupter (AFCI)

A device intended to provide protection from the effects of arc faults by recognizing characteristics unique to arcing and by functioning to de-energize the circuit when an arc fault is detected.

Outlet

A point on the wiring system at which current is taken to supply utilization equipment.

Device

A unit of an electrical system, other than a conductor, that carries or controls electric energy as its principal function.

Do not connect fire and smoke alarms to a circuit that is protected by a GFCI breaker. A nuisance tripping of the GFCI would render the fire alarm and smoke detectors inoperative. This requirement is found in NFPA 72. The National Fire Alarm code, as well as in NEC 760.41(B) and 760.121(B)

Fire Alarm

GFCI receptacles break both the ungrounded ("hot") and grounded conductors. This is a requirement of UL 943, the safety stander for GFCI receptacle will provide the necessary protection if the receptacle is connected with reverse polarity

GFCI Receptacles and Breakers

To protect against electric shocks, 210.8(A) requires that ground-fault circuit interrupter (GFCI) protection be provided for all 125-volt through 250-volt receptacles installed in the location specified in 210.8(A)(1) through (A)(11) and supplied by single-phase branch circuits rated 150 volts or less to ground.

How to protect against electric shock

GFCI protection is required for dishwashers installed in dwelling unit locations. See NEC 422.5(A)(7). This section requires Class A GFCI protection for personnel for circuits that are rated 150 volts to ground and 60 amperes or less and single - or three phase. The GFCI requirements apply whether the dishwasher is supplied by a receptacle or from an outlet.

Kitchen Dishwasher

An area containing or designed to contain a laundry, tray, clothes, washer, or clothes dryer.

Laundry Areas

All outdoor outlets for dwellings, other than those covered in 210.8(A)(3), Exception to (3), that are supplied by single-phase branch circuits rated 150 volts to ground or less, 50 amperes or less, shall have ground-fault circuit interrupter protection for personnel.

Outdoor Outlets 210.8(F)

An exception is that GFCI protection is not required for a receptacle that is not readily accessible and is supplied by a dedicated branch circuit for snow melting or deicing equipment.

Outdoors (A) (3)

Capable of being reached quickly for operation, renewal, or inspections without requiring those to whom ready access is requisite to actions such as to use tools (other than keys) to climb over or under, to remove obstacles or to resort to portable ladders, and so fourth

Readily Accessible Location

Informational Note: Use of keys is a common practice under controlled or supervised conditions and a common alternative to the ready access requirements under such supervised conditions as provided elsewhere in the NEC.

Readily Accessible Location Fun Fact

For the purposes of this section, when determining distance from receptacles the distance shall be measured as the shortest path the supply cost of an appliance connected to the receptacle would follow without piercing a floor, wall, ceiling, or fixed barrier, or the shortest path without passing through a window.

Sinks (A)(7)

In the case of a metal raceway such as EMT, it provides the equipment grounding path through armor. Listed Type MC cable also provides an equipment grounding conductor path by either the armor or the equipment grounding conductor. Listed Type NM cable also provides an equipment grounding conductor.

What GFCI does not do

Voltages of ________ volts to ground are considered safe.

less than 50

It does not limit the magnitude of ground-fault current.

*

It does not protect against electrical shock when a person touches both circuit conductors at the same time (two "hot" wires or one "hot" wire and one grounded neutral conductor), because the current flowing in both conductors is the same. Thus, there is not unbalance of current for the GFCI to sense and trip.

*

It does not sense and protect against the damaging effects of arcing faults, such as would occur with frayed extension cords.

*

It does not sense solid short circuits between the "hot" conductor and the grounded "neutral" conductor.

*

Never ground a system ____________ except the service equipment. A GFCI would be inoperative or trip unneccessarily.

neutral conductor

Never connect the neutral conductor or _____ circuit to the neutral conductor of another circuit.

one

It does not sense solid short circuits between two "hot" conductors.

*

Class A GFCI devices are the most common. They are designed to

- Trip when the current imbalance is 6 milliamperes (6/1000 of an ampere) or greater - Not trip when the current imbalance is less than 4 milliamperes (4/1000 of an ampere) - May or may not trip when the current imbalance is between 4 and 6 milliamperes. - Open very quickly, in approximately 25 milliseconds

All 120-volt, single phase, 15- and 20-ampere branch circuits supplying outlets installed in dwelling unit family rooms, dining rooms, living rooms, parlors, libraries, dens, bedrooms, sunrooms, recreation rooms, closets, hallways, or similar rooms or areas shall be protected by this electrical device. Until recently this device was only required in rooms where people sleep like the bedrooms.

-Arc fault breaker (AFCI) -Ground Fault Interrupter (GFCI) -Push Button -Circuit Breaker

Three of Six different methods of providing AFCI protection

1 ) A listed combination type arc-fault circuit interrupter, installed to provide protection of the entire branch circuit. 2 ) A listed branch/feeder type AFCI installed at the origin of the branch circuit in combination with a listed outlet branch circuit type arc-fault circuit interrupter installed at the first outlet box on the branch circuit. The first outlet box in the branch circuit is required to be marked to indicate that it is the first outlet of the circuit. 3 ) A listed supplemental arc protection circuit breaker installed at the origin of the branch circuit in combination with a listed outlet branch circuit type arc-fault circuit interrupter installed at the first outlet box on the branch circuit where all of the following conditions are met: (a) The branch circuit wiring is continuous from the branch circuit overcurrent device to the outlet branch circuit are arc-fault circuit interrupter. (b) The maximum length of the branch circuit wiring from the branch circuit overcurrent device to the first outlet does not exceed 50 ft (15.2 m) for a 14 AWG wire or 70 ft (21.3 m) for a 12 AWG wire.

Where receptacles are installed within 6 feet (1.8m) or the outside edge of the bathtub or shower stall.

Bathtub and Shower stalls (A)(9)

Shock-painful-severe- can't let go - muscles immobilized - breathing stops

Men = 23.0 milamps Women = 5.0 milamps @ 60 Hertz

It does not provide overload protection for the branch-circuit wiring. It provides _______________ only.

ground-fault protection