Building System Voltages

Question 1

expressed as a nominal voltage
because it varies slightly. __________ can vary from about ______% of the nominal voltage under
normal conditions. Variations from
nominal voltages are caused by a
number of reasons, including
variations in load and changes in
conditions in the power supply system.

Answer 1

Supply voltage, nominal voltage, Supply voltage, 90 to
105%

Question 2

The principle voltages available in
a building.

Answer 2

SYSTEM VOLTAGE

Question 3

Carry voltages above 600 V may be used in special cases such as fo large signage

Answer 3

Medium and high voltage systems

Question 4

carry voltages less than 600 V are
typically used in buildings.

Answer 4

Low voltage systems

Question 5

is expressed as a nominal voltage because it
varies slightly for the reasons mentioned earlier.

Answer 5

System voltage

Question 6

is the initial current-carrying
conductor in an AC system.
Is
frequently known as the hot
or live conductor because it
feeds current to the circuit.

Answer 6

UNGROUNDED (HOT)
CONDUCTOR

Question 7

is required to complete a
single-phase circuit by
connecting the ungrounded
(hot) conductor to ground.

Answer 7

GROUNDED (NEUTRAL)
CONDUCTOR

Question 8

grounded conductor that
serves more than one circuit.

Answer 8

The neutral conductor

Question 9

A third conductor that provides
supplementary but important
grounding protection. Not normally
a current-carrying conductor, but is
energized only on a temporary,
emergency basis when there is a
fault between an ungrounded (hot)
conductor and any metal
associated to the electrical
equipment.

Answer 9

GROUNDING (GROUND) CONDUCTOR

Question 10

The most basic system voltage used. It was
used in the first electrical services to
buildings; however, nearly all have since
been upgraded.

Answer 10

120 Volt, Alternating Current,
Single-Phase, Two-Wire System
(120 V AC, 1-2W)

Question 11

The ___________
provided to the switch-board or panelboard is
by two conductors: one ungrounded (hot)
conductor carrying 120 V and one neutral
conductor. Volt-age measured between the
ungrounded (hot) and neutral conductors is
______.

Answer 11

service entrance, 120V

Question 12

The most common residential
electrical service in use today. It is also used
on a limited basis in light commercial
buildings such as small office buildings,
churches, and retail shops and stores

Answer 12

120/240 Volt, Alternating Current,
Single-Phase, Three-Wire System
(120/240 V AC, 1-3W)

Question 13

a 120 V branch circuit
provides electrical energy to convenience
outlets, small appliances, and light fixtures.

Answer 13

120/240 V system

Question 14

A _______ branch circuit serves large
appliances and equipment such as electric-
resistance baseboard heaters, water heaters,
and air conditioning equipment.

Answer 14

240 V

Question 15

___________
branch circuit provides both 120 V and 240 V to
an appliance such as a range and clothes dryer;
controls, and lightfixtures.

Answer 15

120/240 V

Question 16

_______ run on 120 V and ________
operate on 240 V.

Answer 16

small
motors, heating elements

Question 17

A ___________ runs
continuously through all branch circuits and
serves as a Safety circuit incase of a shot
circuit.

Answer 17

grounding conductor

Question 18

An older electrical service found in small
commercial buildings and high-rise buildings
where three-phase motors, above about _________, and equipment such as large air
conditioners are used. It is not used very
often in industry because a ________ is
more economical for largeCmotor loads.

Answer 18

208 Y/120 Volt, Alternating Current,
Three-Phase, Four-Wire System
(208Y/120 V AC, 3-4W), 1/2
horsepower, 480 V system

Question 19

Is a common electrical service in most modern
medium to large commercial buildings.

Answer 19

480 Y/277 Volt, Alternating
Current, Three-Phase, Four-Wire
System(480Y/277 V AC, 3-4W)

Question 20

used to power specially
designed heavy machinery.

Answer 20

480 V three-phase power

Question 21

fluorescent lighting and other single-phase devices have also been developed specifically for use with this system.

Answer 21

high-voltage, 277 V

Question 22

has economic advantages from the standpoint of equipment and conductor

Answer 22

480 Y/277 Volt, Alternating
Current, Three-Phase, Four-Wire
System(480Y/277 V AC, 3-4W)

Question 23

ls a less common electrical service in large
commercial and industrial buildings that is
used to power specially designed heavy
machinery.

Answer 23

600Y/346 Volt, Alternating
Current, Three-Phase, Four-Wire
System(600Y/346 V AC, 3-4W)

Question 24

has additional
economic advantages from the standpoint of
equipment and conductor sizing in
comparison to the 208Y/120 V and 480Y/277
V systems.

Answer 24

600Y/346 Volt, Alternating
Current, Three-Phase, Four-Wire
System(600Y/346 V AC, 3-4W)

Question 25

ls another fairly common electrical service
found in commercial and industrial buildings where three-phase motors, above about 1/2 horsepower, and equipment such as large air conditioners are used.

Answer 25

240/120 Volt, Alternating Current, Three-Phase, Four-Wire System(240/120 V AC, 3-4W)

Question 26

Between _________ there is 208 V
available.

Answer 26

Phase Y and ground

Question 27

is known as the high leg
or wild leg because it has a higher voltage to
ground than the other legs.

Answer 27

Phase Y

Question 28

The relationship between the building system voltage, current ( Amperage),
and required conductor size for a 20 KVA load and a power factor of 1.0
higher voltage means _________ (and smaller conductor size) for a
__________.

Answer 28

lower amperage, specific load

Question 29

is the target voltage entering the service
panel.will vary slightly
for different buildings because of
variations of voltage available at the
transformer and voltage drop in the
service conductors.

Answer 29

System Voltage

Question 30

The standard for the
system voltage is actually _______

Answer 30

120/240 V.

Question 31

A voltage drop occurs as current flows
from the service equipment through the
branch circuit conductors to the outlet.

Answer 31

Utilization Voltage

Question 32

On a _________, approximately
115/230 V is available at the outlet of the
Branch Circuit.

Answer 32

120/240 V system

Question 33

Measured voltage at an
outlet or connection is called the ________

Answer 33

line
voltage

Question 34

The
highest voltage to which a wiring device can be exposed is known as the _______

Answer 34

Maximum Voltage