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accessible (as applied to wiring methods) capable of being

removed or exposed without damaging the building structure

or finish or not permanently closed in by the structure or

finish of the building


accessible, readily (readily accessible) capable of being

reached quickly for operation, renewal, or inspections

without requiring a person to climb over or remove obstacles

or to use portable ladders


ambient temperature the temperature of the air that surrounds

an object on all sides


American Wire Gauge (AWG) a scale of specified diameters

and cross sections for wire sizing that is the standard

wire-sizing scale in the United States

ammeter (clamp-on) a measuring instrument that has a

movable jaw that is opened and then clamped around a current-

carrying conductor to measure current flow

ammeter (in-line) a measuring instrument that is connected

in series with a load and measures the amount of current

flow in the circuit


ampacity the current in amperes that a conductor can

carry continuously under the conditions of use without exceeding

its temperature rating

  ampere the unit of measure for electrical current flow

analog meter a meter that uses a moving pointer (needle)

to indicate a value on a scale


approved when a piece of electrical equipment is approved,

it means that it is acceptable to the authority having jurisdiction



arc the flow of a high amount of current across an insulating

medium, like air


arc blast a violent electrical condition that causes molten

metal to be thrown through the air


arc fault circuit interrupter (AFCI) circuit breaker a

device intended to provide protection from the effects of

arc faults by recognizing characteristics unique to arcing

and by functioning to deenergize the circuit when an arc

fault is detected


arc fault circuit interrupter (AFCI) receptacle a receptacle

device designed to control dangerous arcs that occur

at receptacles and other outlets in residential bedrooms


architect a qualified person who creates and designs drawings

for a residential construction project


auger a drill bit type with a spiral cutting edge used to

bore holes in wood


auto-ranging meter a meter feature that automatically

selects the range with the best resolution and accuracy


backboard the surface on which a service panel or subpanel

is mounted; it is usually made of plywood and is

painted a flat black color


backfeeding a wiring technique that allows electrical

power from an existing electrical panel to be fed to a new

electrical panel by a short length of cable; this technique is

commonly used when an electrician is upgrading an existing

service entrance


back-to-back bend a type of conduit bend that is formed

by two 90-degree bends with a straight length of conduit between

the two bends


ballast a component in a fluorescent lighting fixture that

controls the voltage and current flow to the lamp

balloon frame a type of frame in which studs are continuous

from the foundation sill to the roof; this type of framing

is found mostly in older homes


band joist the framing member used to stiffen the ends of

the floor joists where they rest on the sill


bandwidth identifies the amount of data that can be

sent on a given cable; it is measured in hertz (Hz) or megahertz

(MHz); a higher frequency means higher data-sending



bathroom branch circuit a branch circuit that supplies

electrical power to receptacle outlets in a bathroom; lighting

outlets may also be served by the circuit as long as other receptacle

or lighting outlets outside the bathroom are not

connected to the circuit; it is rated at 20 amperes


bender a tool used to make various bends in electrical conduit



bimetallic strip a part of a circuit breaker that is made

from two different metals with unequal thermal expansion

rates; as the strip heats up, it will tend to bend

blueprint architectural drawings used to represent a residential

building; it is a copy of the original drawings of the



bonding the permanent joining of metal parts to form an

electrically conductive path that ensures electrical continuity

and the capacity to conduct safely any current likely to be

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imposed on the metal object; the purpose of bonding is to

establish an effective path for fault current that facilitates

the operation of the overcurrent protective device


bonding jumper a conductor used to ensure electrical

conductivity between metal parts that are required to be

electrically connected


bottom plate the lowest horizontal part of a wall frame

which rests on the subfloor


box fill the total space taken up in an electrical box by devices,

conductors, and fittings; box fill is measured in cubic



box offset bend a type of conduit bend that uses two

equal bends to cause a slight change of direction for a conduit

at the point where it is attached to an electrical box


branch circuit the circuit conductors between the final

overcurrent device (fuse or circuit breaker) and the outlets

break lines lines used to show that part of the actual object

is longer than what the drawing is depicting


buried box an electrical box that has been covered over

with sheetrock or some other building material


bushing (insulated) a fiber or plastic fitting designed to

screw onto the ends of conduit or a cable connector to provide

protection to the conductors


cabinet an enclosure for a panel board that is designed for

either flush or surface mounting; a swinging door is provided

cable a factory assembly of two or more insulated conductors

that have an outer sheathing that holds everything together;

the outside sheathing can be metallic or nonmetallic


cable hook also called an “eyebolt”; it is the part used to

attach the service drop cable to the side of a house in an

overhead service entrance installation

  candlepower a measure of lighting intensity

cartridge fuse a fuse enclosed in an insulating tube that

confines the arc when the fuse blows; this fuse may be either

a ferrule or a blade type


category ratings on the bandwidth performance of UTP cable;

categories include 3, 4, 5, 5e, and 6; Category 5 is rated

to 100 MHz and is the most widely used


ceiling joists the horizontal framing members that rest on

top of the wall framework and form the ceiling


centerline a series of short and long dashes used to designate

the center of items, such as windows and doors


checkout the process of determining if all parts of a recently

installed electrical system are functioning properly


chuck key a small wrench, usually in a T shape, used to

open or close a chuck on a power drill

circuit breaker a device designed to open and close a circuit

manually and to open the circuit automatically on a predetermined

overcurrent without damage to itself when

properly applied within its rating

circuit (electrical) an arrangement consisting of a power

source, conductors, and a load


circular mils the diameter of a conductor in mils (thousandths

of inches) times itself; the number of circular mils is

the cross-sectional area of a conductor


Class P ballast a ballast with a thermal protection unit

built in by the manufacturer; this unit opens the lighting

electrical circuit if the ballast temperature exceeds a specified



coaxial cable a cable in which the center signal-carrying

conductor is centered within an outer shield and separated

from the conductor by a dielectric; used to deliver video signals

in residential structured cabling installations

combination switch a device with more than one switch

type on the same strap or yoke


computer-aided drafting (CAD) the making of building

drawings using a computer


concentric knockout a series of removable metal rings that

allow the knockout size to vary according to how many of the

metal rings are removed; the center of the knockout hole stays

the same as more rings are removed; some standard residential

wiring sizes are 1⁄2, 3⁄4, 1, 114, 112, 2, and 212 inches


conductor a material that allows electrical current to flow

through it; examples are copper, aluminum, and silver


conduit a raceway with a circular cross section, such as

electrical metallic tubing, rigid metal conduit, or intermediate

metal conduit;


conduit “LB” a piece of electrical equipment that is connected

in-line with electrical conduit to provide for a 90°

change of direction


connector a fitting that is designed to secure a cable or

length of conduit to an electrical box

continuity tester a testing device used to indicate

whether there is a continuous path for current flow through

an electrical circuit or circuit component


copper-clad aluminum an aluminum conductor with an

outer coating of copper that is bonded to the aluminum core


cord-and-plug connection an installation technique

where electrical appliances are connected to a branch circuit

with a flexible cord with an attachment plug; the attachment

plug end is plugged into a receptacle of the proper size

and type


counter-mounted cooktop a cooking appliance that is

installed in the top of a kitchen countertop; it contains surface

cooking elements, usually two large elements and two

small elements


crimp a process used to squeeze a solderless connector

with a tool so that it will stay on a conductor


critical loads the electrical loads that are determined to

require electrical power from a standby power generator

when electrical power from the local electric utility company

is interrupted

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  current the intensity of electron flow in a conductor

cutter a hardened steel device used to cut holes in metal

electrical boxes


detail drawing a part of the building plan that shows an

enlarged view of a specific area


deteriorating agents a gas, fume, vapor, liquid, or any

other item that can cause damage to electrical equipment


device a piece of electrical equipment that is intended to

carry but not use electrical energy; examples include

switches, lamp holders, and receptacles


device box an electrical device that is designed to hold devices

such as switches and receptacles


die the component of a knockout punch that works in conjunction

with the cutter and is placed on the opposite side

of the metal box or enclosure


digital meter a meter where the indication of the measured

value will be given as an actual number in a liquid crystal

display (LCD)


dimension a measurement of length, width, or height

shown on a building plan


dimension line a line on a building plan with a measurement

that indicates the dimension of a particular object

dimmer switch a switch type that raises or lowers the

lamp brightness of a lighting fixture


disconnecting means a term used to describe a switch that

is able to deenergize an electrical circuit or piece of electrical

equipment; sometimes referred to as the “disconnect”

  DMM a series of letters that stands for “digital multimeter”

double insulated an electrical power tool type constructed

so the case is isolated from electrical energy and is

made of a nonconductive material

double-pole switch a switch type used to control two

separate 120-volt circuits or one 240-volt circuit from one



draft-stops also called “fire-stops”; the material used to

reduce the size of framing cavities in order to slow the

spread of fire; in wood frame construction, it consists of fullwidth

dimension lumber placed between studs or joists


drip loop an intentional loop put in service entrance conductors

at the point where they extend from a weatherhead;

the drip loop conducts rainwater to a lower point than the

weatherhead, helping to ensure that no water will drip down

the service entrance conductors and into the meter enclosure


dry-niche luminaire a lighting fixture intended for installation

in the wall of a pool that goes in a niche; it has a

fixed lens that seals against water entering the niche and

surrounding the lighting fixture


dual-element time-delay fuses a fuse type that has a

time-delay feature built into it; this fuse type is used most

often as an overcurrent protection device for motor circuits


duplex receptacle the most common receptacle type used

in residential wiring; it has two receptacles on one strap;

each receptacle is capable of providing power to a cord-andplug-

connected electrical load


dwelling unit one or more rooms for the use of one or

more persons as a housekeeping unit with space for eating,

living, and sleeping and permanent provisions for cooking

and sanitation


eccentric knockout a series of removable metal rings that

allow a knockout size to vary according to how many of the

metal rings are removed; the center of the knockout hole

changes as more metal rings are removed; common sizes are

the same as for concentric knockouts


Edison-base plug fuse a fuse type that uses the same standard

screw base as an ordinary lightbulb; different fuse sizes

are interchangeable with each other; this fuse type may only

be used as a replacement for an existing Edison-base plug fuse


efficacy a rating that indicates the efficiency of a light



EIA/TIA an acronym for the Electronic Industry Association

and Telecommunications Industry Association; these organizations

create and publish compatibility standards for the

products made by member companies


EIA/TIA 570-A the main standard document for structured

cabling installations in residential situations


electric range a stand-alone electric cooking appliance

that typically has four cooking elements on top and an oven

in the bottom of the appliance


electrical drawings a part of the building plan that shows

the electrical supply and distribution for the building electrical



electrical shock the sudden stimulation of nerves and

muscle caused by electricity flowing through the body

elevation drawing a drawing that shows the side of the

house that faces in a particular direction; for example, the

north elevation drawing shows the side of the house that is

facing north


enclosure the case or housing of apparatus or the fence or

walls surrounding an installation to prevent personnel from

accidentally contacting energized parts or to protect the

equipment from physical damage


equipment a general term including material, fittings, devices,

appliances, luminaires (lighting fixtures), apparatus, and

other parts used in connection with an electrical installation


equipment-grounding conductor the conductor used to

connect the non-current-carrying metal parts of equipment,

raceways, and other enclosures to the system-grounded conductor,

the grounding electrode conductor, or both at the

service equipment


exothermic welding a process for making bonding connections

on the bonding grid for a permanently installed

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swimming pool using specially designed connectors, a form,

a metal disk, and explosive powder; this process is sometimes

called “Cad-Weld”


extension lines lines used to extend but not actually

touch object lines and have the dimension lines drawn between



feeder the circuit conductors between the service equipment

and the final branch-circuit overcurrent protection device


field bend any bend or offset made by installers, using

proper tools and equipment, during the installation of conduit



fish the process of installing cables in an existing wall or



fitting an electrical accessory, like a locknut, that is used

to perform a mechanical rather than an electrical function


floor joists horizontal framing members that attach to the

sill plate and form the structural support for the floor and


floor plan a part of the building plan that shows a bird’seye

view of the layout of each room


fluorescent lamp a gaseous discharge light source; light

is produced when the phosphor coating on the inside of a

sealed glass tube is struck by energized mercury vapor


foot-candle the unit used to measure how much total light

is reaching a surface; 1 lumen falling on 1 square foot of surface

produces an illumination of 1 foot-candle


footing the concrete base on which a dwelling foundation

is constructed; it is located below grade


forming shell the support structure designed and used with

a wet-niche lighting fixture; it is installed in the wall of a pool


foundation the base of the structure, usually poured concrete

or concrete block, on which the framework of the

house is built; it sits on the footing


four-way switch a switch type that, when used in conjunction

with two three-way switches, will allow control of a

120-volt lighting load from more than two locations

framing the building “skeleton” that provides the structural

framework of the house


F-type connector a 75-ohm coaxial cable connector that

can fit RG-6 and RG-59 cables and is used for terminating

video system cables in residential wiring applications

fuse that opens a circuit when the fusible link is melted

away by the extreme heat caused by an overcurrent


ganging the joining together of two or more device boxes

for the purpose of holding more than one device


general lighting circuit a branch-circuit type used in residential

wiring that has both lighting and receptacle loads

connected to it; a good example of this circuit type is a bedroom

branch circuit that has both receptacles and lighting

outlets connected to it

generator a rotating machine used to convert mechanical

energy into electrical energy


girders heavy beams that support the inner ends of floor



ground a conducting connection, whether intentional or

accidental, between an electrical circuit or equipment and

the earth or to some conducting body that serves in place of

the earth

ground fault an unintended low-resistance path in an

electrical circuit through which some current flows to

ground using a pathway other than the intended pathway;

it results when an ungrounded “hot” conductor unintentionally

touches a grounded surface or grounded



ground fault circuit interrupter (GFCI) a device that

protects people from dangerous levels of electrical current by

measuring the current difference between two conductors of

an electrical circuit and tripping to an open position if the

measured value exceeds 6 milliamperes


grounded connected to earth or to some conducting body

that serves in place of the earth


grounded conductor a system or circuit conductor that is

intentionally grounded


grounding an electrical connection to an object that conducts

electrical current to the earth


grounding conductor a conductor used to connect equipment

or the grounded conductor of a wiring system to a

grounding electrode or electrodes


grounding electrode a part of the building service entrance

that connects the grounded service (neutral) conductor

to the earth


grounding electrode conductor the conductor used to

connect the grounding electrode to the equipment-grounding

conductor, to the grounded conductor, or to both at

the service


handy box a type of metal device box used to hold only

one device; it is surface mounted


hardwired an installation technique where the circuit conductors

are brought directly to an electrical appliance and

terminated at the appliance


harmonics a frequency that is a multiple of the 60 Hz fundamental;

harmonics cause distortion of the voltage and current

AC waveforms

  hazard a potential source of danger

heat pump a reversible air-conditioning system that will

heat a house in cool weather and cool a house in warm



hidden line a line on a building plan that shows an object

hidden by another object on the plan; hidden lines are drawn

using a dashed line


high-intensity discharge (HID) lamp another type of

gaseous discharge lamp, except the light is produced without

the use of a phosphor coating


home run the part of the branch-circuit wiring that originates

in the loadcenter and provides electrical power to the

first electrical box in the circuit


horizontal cabling the connection from the distribution

center to the work area outlets


hydraulic a term used to describe tools that use a pressurized

fluid, like oil, to accomplish work

hydromassage bathtub a permanently installed bathtub

with recirculating piping, pump, and associated equipment; it

is designed to accept, circulate, and discharge water each use


hydronic system a term used when referring to a hot water

heating system


IDC an acronym for “insulation displacement connection”; a

type of termination where the wire is “punched down” into a

metal holder with a punch-down tool; no prior stripping of

the wire is required


impulse a type of transient voltage that originates outside

the home and is usually caused by utility company switching

or lightning strikes


incandescent lamp the original electric lamp; light is produced

when an electric current is passed through a filament;

the filament is usually made of tungsten


individual branch circuit a circuit that supplies only one

piece of electrical equipment; examples are one range, one

space heater, or one motor


inductive heating the heating of a conducting material in

an expanding and collapsing magnetic field; inductive heating

will occur when current-carrying conductors of a circuit

are brought through separate holes in a metal electrical box

or enclosure


insulated refers to a conductor that is covered by a material

that is recognized by the National Electrical Code® as

electrical insulation


insulator a material that does not allow electrical current

to flow through it; examples are rubber, plastic, and glass


interconnecting the process of connecting together smoke

detectors so that if one is activated, they all will be activated


interrupting rating the highest current at rated voltage

that a device is intended to interrupt under standard test



inverse time circuit breaker a type of circuit breaker

that has a trip time that gets faster as the fault current

flowing through it gets larger; this is the circuit breaker type

used in house wiring

  jack he receptacle for an RJ-45 plug

jacketed cable a voice/data cable that has a nonmetallic

polymeric protective covering placed over the conductors

jet pump a type of water pump used in home water systems;

the pump and electric motor are separate items that

are located away from the well in a basement, garage, crawl

space, or other similar area


jug handles a term used to describe the type of bend that

must be made with certain cable types; bending cable too

tightly will result in damage to the cable and conductor insulation;

bending them in the shape similar to a “handle” on

a “jug” will help satisfy NEC® bending requirements


junction box a box whose purpose is to provide a protected

place for splicing electrical conductors


kilowatt-hour meter an instrument that measures the

amount of electrical energy supplied by the electric utility

company to a dwelling unit


knockout (KO) a part of an electrical box that is designed

to be removed, or “knocked out,” so that a cable or raceway

can be connected to the box


knockout plug a piece of electrical equipment used to fill

unused openings in boxes, cabinets, or other electrical


knockout punch a tool used to cut holes in electrical

boxes for the attachment of cables and conduits


laundry branch circuit a type of branch circuit found in

residential wiring that supplies electrical power to laundry

areas; no lighting outlets or other receptacles may be connected

to this circuit


leader a solid line that may or may not be drawn at an angle

and has an arrow on the end of it; it is used to connect a

note or dimension to a part of the building


legend a part of a building plan that describes the various

symbols and abbreviations used on the plan

level perfectly horizontal; completely flat; a tool used to

determine if an object is level


lighting outlet an outlet intended for the direct connection

of a lamp holder, a luminaire (lighting fixture), or a

pendant cord terminating in a lamp holder


line side the location in electrical equipment where the incoming

electrical power is connected; an example is the lineside

lugs in a meter socket where the incoming electrical

power conductors are connected


load (electrical) a part of an electrical circuit that uses

electrical current to perform some function; an example

would be a lightbulb (produces light) or electric motor (produces

mechanical energy)


load side the location in electrical equipment where the

outgoing electrical power is connected; an example is the

load-side lugs in a meter socket where the outgoing electrical

power conductors to the service equipment are connected


loadcenter a type of panelboard normally located at the

service entrance in a residential installation and usually containing

the main service disconnect switch


lug a device commonly used in electrical equipment used

for terminating a conductor

  lumen the unit of light energy emitted from a light source

luminaire a complete lighting unit consisting of a lamp or

lamps together with the parts designed to distribute the

light, to position and protect the lamps and ballast (where

applicable), and to connect the lamps to the power supply


Madison hold-its thin metal straps that are used to hold

“old-work” electrical boxes securely to an existing wall or ceiling

main bonding jumper a jumper used to provide the connection

between the grounded service conductor and the

equipment-grounding conductor at the service


manual ranging meter a meter feature that requires the

user to manually select the proper range

mast kit a package of additional equipment that is required

for the installation of a mast-type service entrance; it

can be purchased from an electrical distributor

Material Safety Data Sheet (MSDS) a form that lists

and explains each of the hazardous materials that electricians

may work with so they can safely use the material and

respond to an emergency situation


megabits per second (Mbps) refers to the rate that digital

bits (1s and 0s) are sent between two pieces of equipment


megahertz (MHz) refers to the upper frequency band on

the ratings of a cabling system

megohmmeter a measuring instrument that measures

large amounts of resistance and is used to test electrical

conductor insulation


meter enclosure the weatherproof electrical enclosure

that houses the kilowatt-hour meter; also called the “meter

socket” or “meter trim”


mil 1 mil is equal to .001 inches; this is the unit of measure

for the diameter of a conductor


multimeter a measuring instrument that is capable of

measuring many different electrical values, such as voltage,

current, resistance, and frequency, all in one meter


multiwire circuit a circuit in residential wiring that consists

of two ungrounded conductors that have 240 volts between

them and a grounded conductor that has 120 volts

between it and each ungrounded conductor


nameplate the label located on an appliance that contains

information such as amperage and voltage ratings, wattage

ratings, frequency, and other information needed for the correct

installation of the appliance


National Electrical Code® (NEC®) a document that establishes

minimum safety rules for an electrician to follow

when performing electrical installations; it is published by

the National Fire Protection Association (NFPA)


National Electrical Manufacturers Association (NEMA)

an organization that establishes certain construction standards

for the manufacture of electrical equipment; for example, a

NEMA Type 1 box purchased from Company X will meet the same

construction standards as a NEMA Type 1 box from Company Y


new work box an electrical box without mounting ears;

this style of electrical box is used to install electrical wiring

in a new installation


nipple an electrical conduit of less than 2 feet in length

used to connect two electrical enclosures


noncontact voltage tester a tester that indicates if a

voltage is present by lighting up, making a noise, or vibrating;

the tester is not actually connected into the electrical

circuit but is simply brought into close proximity of the energized

conductors or other system parts


no-niche luminaire a lighting fixture intended for above or

below the water-level installation; it does not have a forming

shell that it fits into but rather sits on the surface of the pool

wall; it can be located above or below the waterline


nonlinear loads a load where the load impedance is not

constant, resulting in harmonics being present on the electrical



object line a solid dark line that is used to show the main

outline of the building


Occupational Safety and Health Administration

(OSHA) since 1971, OSHA’s job has been to establish and

enforce workplace safety rules


offset bend a type of conduit bend that is made with two

equal-degree bends in such a way that the conduit changes

elevation and avoids an obstruction

  ohm the unit of measure for electrical resistance

ohmmeter a measuring instrument that measures values of



Ohm’s law the mathematical relationship between current,

voltage, and resistance in an electrical circuit


old work box an electrical box with mounting ears; this

style of electrical box is used to install electrical wiring in

existing installations

open circuit a circuit that is energized but does not allow

useful current to flow on the circuit because of a break in

the current path


outlet a point on the wiring system at which current is

taken to supply electrical equipment; an example is a lighting

outlet or a receptacle outlet


outlet box a box that is designed for the mounting of a receptacle

or a lighting fixture


overcurrent any current in excess of the rated current of

equipment or the ampacity of a conductor; it may result from

an overload, a short circuit, or a ground fault


overcurrent protection device (OCPD) a fuse or circuit

breaker used to protect an electrical circuit from an overload,

a short circuit, or a ground fault


overload a larger-than-normal current amount flowing in

the normal current path


panelboard a panel designed to accept fuses or circuit breakers

used for the protection and control of lighting, heating,

and power circuits; it is designed to be placed in a cabinet and

placed in or on a wall; it is accessible only from the front


patch cord a short length of cable with an RJ-45 plug on

either end; used to connect hardware to the work area outlet

or to connect cables in a distribution panel


permanently installed swimming pool a swimming pool

constructed totally or partially in the ground with a water depth

capacity of greater than 42 inches (1 m); all pools, regardless of

depth, installed in a building are considered permanent


pigtail a short length of wire used in an electrical box to

make connections to device terminals


platform frame a method of wood frame construction in

which the walls are erected on a previously constructed floor

deck or platform


plumb perfectly vertical; the surface of the item you are

leveling is at a right angle to the floor or platform you are

working from


polarity the positive or negative direction of DC voltage or



polarized plug a two-prong plug that distinguishes between

the grounded conductor and the “hot” conductor by

having the grounded conductor prong wider than the hot conductor

prong; this plug will fit into a receptacle only one way

pool cover, electrically operated a motor-driven piece

of equipment designed to cover and uncover the water surface

of a pool


porcelain standoff a fitting that is attached to a service

entrance mast, which provides a location for the attachment

of the service drop conductors in an overhead service entrance


power source a part of an electrical circuit that produces

the voltage required by the circuit


pryout (PO) small parts of electrical boxes that can be

“pried” open with a screwdriver and twisted off so that a cable

can be secured to the box


pulling in the process of installing cables through the

framework of a house


punch-down block the connecting block that terminates

cables directly; 110 blocks are most popular for residential



raceway an enclosed channel of metal or nonmetallic materials

designed expressly for holding wires or cables; raceways

used in residential wiring include rigid metal conduit, rigid

nonmetallic conduit, intermediate metal conduit, liquid-tight

flexible conduit, flexible metal conduit, electrical nonmetallic

tubing, and electrical metallic tubing


rafters part of the roof structure that is supported by the

top plate of the wall sections; the roof sheathing is secured

to the rafters and then covered with shingles or other roofing

material to form the roof


rain-tight constructed or protected so that exposure to a

beating rain will not result in the entrance of water under

specified test conditions

receptacle a device installed in an electrical box for the

connection of an attachment plug


receptacle polarity when the white-colored grounded

conductor is attached to the silver screw of the receptacle

and the “hot” ungrounded circuit conductor is attached to

the brass screw on the receptacle; this results in having the

long slot always being the grounded slot and the short slot

always being the ungrounded slot on 125-volt, 15- or 20-

amp-rated receptacles used in residential wiring

  reciprocating to move back and forth

redhead sometimes called a “red devil”; an insulating fitting

required to be installed in the ends of a Type AC cable

to protect the wires from abrasion

reel a drum having flanges on each end; reels are used for

wire or cable storage

  resistance the opposition to current flow

RG-59 a type of coaxial cable typically used for residential

video applications; EIA/TIA 570A recommends that RG-6

coaxial cable be used instead of RG-59 because of the better

performance characteristics of the RG-6 cable


RG-6 (Series 6) a type of coaxial cable that is “quad

shielded” and is used in residential structured cabling systems

to carry video signals such as cable and satellite television


ribbon a narrow board placed flush in wooden studs of a

balloon frame to support floor joists


ring one of the two wires needed to set up a telephone

connection; it is connected to the negative side of a battery

at the telephone company; it is the telephone industry’s

equivalent to an ungrounded “hot” conductor in a normal

electrical circuit


ring wave a type of transient voltage that originates inside

the home and is usually caused by home office photocopiers,

computer printers, the cycling on and off of heating, ventilating,

and air-conditioning equipment, and spark igniters

on gas appliances like furnaces and ranges


riser a length of raceway that extends up a utility pole and

encloses the service entrance conductors in an underground

service entrance

  RJ-11 a popular name for a six-position UTP connector

RJ-45 the popular name for the modular eight-pin connector

used to terminate Category 5 UTP cable


Rome Xa trade name for nonmetallic sheathed cable (NMSC);

this is the term most electricians use to refer to NMSC


roof flashing/weather collar two parts of a mast-type

service entrance that, when used together, will not allow water

to drip down and into a house through the hole in the

roof that the service mast extends through


rough-in the stage in an electrical installation when the raceways,

cable, boxes, and other electrical equipment are installed;

this electrical work must be completed before any construction

work can be done that covers wall and ceiling surfaces


running boards pieces of board lumber nailed or screwed

to the joists in an attic or basement; the purpose of using

running boards is to have a place to secure cables during the

rough-in stage of installing a residential electrical system


saddle bend a type of conduit bend that results in a conduit

run going over an object that is blocking the path of

the run; there are two styles: a three-point saddle and a

four-point saddle


safety switch a term used sometimes to refer to a disconnect

switch; a safety switch may use fuses or a circuit

breaker to provide overcurrent protection


scaffolding also referred to as staging; a piece of equipment

that provides a platform for working in high places; the

parts are put together at the job site and then taken apart

and reconstructed when needed at another location


scale the ratio of the size of a drawn object and the object’s

actual size

schedule a table used on building plans to provide information

about specific equipment or materials used in the

construction of the house

  sconce a wall-mounted lighting fixture

sectional drawing a part of the building plan that shows

a cross-sectional view of a specific part of the dwelling


secured (as applied to electrical cables) fastened in place

so the cable cannot move; common securing methods include

staples, tie wraps, and straps


self-contained spa or hot tub a factory-fabricated unit

consisting of a spa or hot tub vessel having integrated water-

circulating, heating, and control equipment


service the conductors and equipment for delivering electric

energy from the serving utility to the wiring system of

the premises served


service center the hub of a structured wiring system with

telecommunications, video, and data communications installed;

it is usually located in the basement next to the

electrical service panel or in a garage; sometimes called a

“distribution center”

service conductors the conductors from the service point

to the service disconnecting means


service disconnect a piece of electrical equipment installed

as part of the service entrance that is used to disconnect the

house electrical system from the electric utility’s system


service drop the overhead service conductors from the last

pole to the point connecting them to the service entrance

conductors at the building

service entrance conductors, overhead system the

service conductors between the terminals of the service

equipment and a point usually outside the building where

they are joined by tap or splice to the service drop

service entrance conductors, underground system

the service conductors between the terminals of the service

equipment and the point of connection to the service lateral


service entrance the part of the wiring system where

electrical power is supplied to the residential wiring system

from the electric utility; it includes the main panelboard, the

electric meter, overcurrent protection devices, and service



service equipment the necessary equipment connected to

the load end of the service conductors supplying a building

and intended to be the main control and cutoff of the supply


service head the fitting that is placed on the service drop

end of service entrance cable or service entrance raceway

and is designed to minimize the amount of moisture that can

enter the cable or raceway; the service head is commonly referred

to as a “weatherhead”


service lateral the underground service conductors between

the electric utility transformer, including any risers at

a pole or other structure, and the first point of connection to

the service entrance conductors in a meter enclosure


service mast a piece of rigid metal conduit or intermediate

metal conduit, usually 2 or 212 inches in diameter, that provides

service conductor protection and the proper height requirements

for service drops


service point the point of connection between the wiring

of the electric utility and the premises wiring


service raceway the rigid metal conduit, intermediate

metal conduit, electrical metallic tubing, rigid nonmetallic

conduit, or any other approved raceway that encloses the

service entrance conductors


setout the distance that the face of an electrical box protrudes

out from the face of a building framing member; this

distance is dependent on the thickness of the wall or ceiling

finish surface material


shall a term used in the National Electrical Code® that

means that the rule must be followed


sheath the outer covering of a cable that is used to provide

protection and to hold everything together as a single unit


sheathing boards sheet material like plywood that is fastened

to studs and rafters; the wall or roofing finish material

will be attached to the sheathing


sheetrock a popular building material used to finish off walls

and ceilings in residential and commercial construction; it is

available in standard sizes, such as 4 by 8 feet, and is constructed

of gypsum sandwiched between a paper front and back


short circuit an unintended low-resistance path through

which current flows around rather than along a circuit’s intended

current path; it results when two circuit conductors

come in contact with each other unintentionally


sill a length of wood that sets on top of the foundation and

provides a place to attach the floor joists


sill plate a piece of equipment that, when installed correctly,

will help keep water from entering the hole in the side

of a house that the service entrance cable from the meter

socket to the service panel goes through


single receptacle a single contact device with no other

contact device on the same strap (yoke)

single-pole switch a switch type used to control a 120-

volt lighting load from one location

small-appliance branch circuit a type of branch circuit

found in residential wiring that supplies electrical power to

receptacles located in kitchens and dining rooms; no lighting

outlets are allowed to be connected to this circuit type

spa or hot tub a hydromassage pool or tub designed for

immersion of users; usually has a filter, heater, and motordriven

pump; it can be installed indoors or outdoors, on the

ground, or in a supporting structure; a spa or hot tub is not

designed to be drained after each use


specifications a part of the building plan that provides

more specific details about the construction of the building


spliced connecting two or more conductors with a piece of

approved equipment like a wirenut; splices must be done in

approved electrical boxes


split-wired receptacle a duplex receptacle wired so that

the top outlet is “hot” all the time and the bottom outlet is

switch controlled


stab a term used to identify the location on a loadcenter’s

ungrounded bus bar where a circuit breaker is snapped on


standby power system a backup electrical power system

that consists of a generator, transfer switch, and associated

electrical equipment; its purpose is to provide electrical

power to critical branch circuits when the electrical power

from the utility company is not available

storable swimming pool a swimming pool constructed

on or above the ground with a maximum water depth capacity

of 42 inches (1 m) or a pool with nonmetallic, molded

polymeric walls (or inflatable fabric walls) regardless of size

or water depth capacity


STP an acronym for “shielded twisted pair” cable; it resembles

UTP but has a foil shield over all four pairs of copper

conductors and is used for better high-frequency performance

and less electromagnetic interference


strap (yoke) the metal frame that a receptacle or switch is

built around; it is also used to mount a switch or receptacle

to a device box

  strip to damage the threads of the head of a bolt or screw

structure in a two-story house, the first-floor ceiling joists

are the second floor’s floor joists


structured cabling an architecture for communications

cabling specified by the EIA/TIA TR41.8 committee and used

as a voluntary standard by manufacturers to ensure compatibility


stub-up a type of conduit bend that results in a 90-degree

change of direction


subfloor the first layer of floor material that covers the

floor joists; usually 4-by-8-plywood or particleboard

submersible pump a type of water pump used in home

water systems; the pump and electric motor are enclosed in

the same housing and are lowered down a well casing to a

level that is below the water line


supplemental grounding electrode a grounding electrode

that is used to “back up” a metal water pipe grounding electrode


supported (as applied to electrical cables) held in place so

the cable is not easily moved; common supporting methods

include running cables horizontally through holes or notches

in framing members or using staples, tie wraps, or straps after

a cable has been properly secured close to a box according

to the NEC®


switch box a name used to refer to a box that just contains



switch loop a switching arrangement where the feed is

brought to the lighting outlet first and a two-wire loop run

from the lighting outlet to the switch


symbol a standardized drawing on the building plan that

shows the location and type of a particular material or component


take-up the amount that must be subtracted from a desired

stub-up height so the bend will come out right; the take-up

is different for each conduit size

  tempered treated with heat to maximize the metal hardness

thermostat a device used with a heating or cooling system

to establish a set temperature for the system to achieve;

they are available as line voltage models or low-voltage

models; some thermostats can also be programmed to keep a

home at a specific temperature during the day and another

temperature during the night


thinwall a trade name often used for electrical metallic


threaded hub the piece of equipment that must be attached

to the top of a meter socket so that a raceway or a

cable connector can be attached to the meter socket


three-way switch a switch type used to control a 120-volt

lighting load from two locations


tip the first wire in a pair; a conductor in a telephone cable

pair that is usually connected to the positive side of a battery

at the telephone company’s central office; it is the telephone

industry’s equivalent to a grounded conductor in a

normal electrical circuit

  top plate the top horizontal part of a wall framework

torque the turning or twisting force applied to an object

when using a torque tool; it is measured in inch-pounds or



transfer switch a switching device for transferring one or

more load conductor connections from one power source to



transformer the electrical device that steps down the 120-

volt house electrical system voltage to the 16 volts a chime

system needs to operate correctly


transient voltage surge suppressor (TVSS) (receptacle

or strip) an electrical device designed to protect sensitive

electronic circuit boards from voltage surges


troffer a term commonly used by electricians to refer to a

fluorescent lighting fixture installed in the grid of a suspended



troubleshooting the process of determining the cause of a

malfunctioning part of a residential electrical system


true RMS meter a type of meter that allows accurate

measurement of AC values in harmonic environments


twistlock receptacle a type of receptacle that requires

the attachment plug to be inserted and then turned slightly

in a clockwise direction to lock the plug in place; the attachment

plug must be turned slightly counterclockwise to release the plug so it
can be removed from the receptacle


Type IC a light fixture designation that allows the fixture

to be completely covered by thermal insulation


Type Non-IC a light fixture that is required to be kept at

least 3 inches from thermal insulation


Type S plug fuse a fuse type that uses different fuse

bases for each fuse size; an adapter that matches each Type

S fuse size is required; this fuse type is not interchangeable

with other Type S fuse sizes


utility box a name used to refer to a metal single gang,

surface mounted device box; also called a handy box


utility pole a wooden circular column used to support

electrical, video, and telecommunications utility wiring; it

may also support the transformer used to transform the high

utility company voltage down to the lower voltage used in a

residential electrical system


UTP an acronym for “unshielded twisted pair” cable; it is

comprised of four pairs of copper conductors and graded for

bandwidth as “categories” by EIA/TIA 568; each pair of wires

is twisted together


ventricular fibrillation very rapid irregular contractions

of the heart that result in the heartbeat and pulse going out

of rhythm with each other

  volt the unit of measure for voltage

voltage the force that causes electrons to move from atom

to atom in a conductor


voltage tester a device designed to indicate approximate

values of voltage or to simply indicate if a voltage is present


volt-ampere a unit of measure for alternating current electrical

power; for branch-circuit, feeder, and service calculation

purposes, a watt and a volt-ampere are considered the same


voltmeter a measuring instrument that measures a precise

amount of voltage


VOM a name sometimes used in reference to a “multimeter”;,

the letters stand for “volt-ohm milliammeter”


wall studs the parts that form the vertical framework of a

wall section


wallboard a thin board formed from gypsum and layers of

paper that is used often as the interior wall sheathing in residential

applications; commonly called “sheetrock”


wall-mounted oven a cooking appliance that is installed

in a cabinet or wall and is separated from the countermounted



wet location installations underground or in concrete slabs

or masonry in direct contact with the earth in locations subject

to saturation with water or other liquids, such as in unprotected

areas exposed to the weather


wet-niche luminaire a type of lighting fixture intended

for installation in a wall of a pool; it is accessible by removing

the lens from the forming shell; this luminaire type is

designed so that water completely surrounds the fixture inside

the forming shell

Wiggy a trade name for a solenoid type of voltage tester

wirenut a piece of electrical equipment used to mechanically

connect two or more conductors together


wiring a term used by electricians to describe the process

of installing a residential electrical system


work area outlet the jack on the wall that is connected to

the desktop computer by a patch cord