commercial wiring final exam 8 to 16
An inverse-time circuit breaker allows as much as ____ times the overload current before opening the circuit.
10
The NEC ____ rule allows a feeder conductor of smaller ampacity to be tapped without overcurrent protection at the tap.
10 ft tap
The minimum vertical clearance of service-drop conductors ranges from ____.
10¢ to 24.5¢
The NEC requires at least one receptacle outlet for every ____ feet of show-window space, measured horizontally.
12
In hotel rooms, circuits supplying small receptacle loads cannot exceed ____ amps.
120
Provides a highly efficient, economical, and flexible supply for small commercial establishments. Both single- and three-phase loads can be supplied.
120/208 V
Used primarily for lighting, small appliance, and motor circuits in homes, small stores, and light commercial facilities.
120/240 V
Often used for large industrial plants because of its tremendous versatility. Voltage supply is fed to substations within the plant that step-down the voltage to various levels, depending on the load requirements.
13,800 V three phase
Grounded-neutral and step-down transformers are used to supply a wide variety of voltages for motors, lighting, and substations in industrial plants.
2400/4160 v
Provides power to panelboards, busways, and wireways supplying motor branch circuits in commercial and industrial facilities. Adding a grounded center tap to one of the phase legs creates a neutral for circuits such as lighting.
240V three phase
Type of distribution that provides power for substantial motor loads, as well as power for large fluorescent lighting loads commonly found in large commercial and industrial complexes.
277/480 V three phase
Branch circuits are usually ____ amps or less.
30
Electrical service equipment requires a minimum of ____ clear horizontal space in front of the equipment.
30²
Primarily used in industrial complexes to feed substations for motors and lighting. The supply is stepped down at substations and transformers in order to supply lower-voltage requirements.
4800 v three phase
For commercial and industrial facilities that have fairly large motor power requirements. Voltage can be reduced with a step-down transformer for lighting and receptacle loads.
480V three phase
The smallest service-drop conductor is ____ AWG copper.
8
Neutral service conductor
A
Neutral busbar
B
Main bonding jumper
C
Grounded circuit conductors (neutral)
D
Grounding busbar
E
Grounding electrode conductor
F
Grounding electrode
G
The device that is designed to open the circuit when current-to-ground exceeds 6 milliamperes is a(n) ____.
GFCI
The minimum number of receptacles required in a commercial installation is ____.
The NEC does not have a minimum requirement.
Service feeders can be directly buried using ____ cable.
USE
Which of the following lighting loads must be calculated using the actual load?
all above
Circuit breakers can be operated ____.
all the above
Mercury-vapor lighting installed 25¢ high in a warehouse can be supplied by ____ volts.
all the above
The means of disconnecting all power feeders from the service-entrance conductors can be ____.
all the above
AFCI stands for ____.
arc-fault circuit-interrupter
The mechanical joining of metallic parts to form an electrically conductive path is called ____.
bonding
Conductors used for bonding are called ____.
bonding jumpers
According to the Code, overcurrent protection devices must be ____.
both A and B
Overcurrent protective devices are rated for ____.
both A and B
The portion of the wiring system extending past the final overcurrent device is ____.
branch circuits
The two general types of fuses are plug and ____.
catrigde
The only externally wired fixtures allowed in a show window is a(n) ____.
chain-supported fixture
These fuses can be renewable or nonrenewable. They have a low interrupting rating of only 10,000 amperes and are not current limiting.
class H
These fuses are nonrenewable and current limiting with an interrupting rating of 200,000 amperes. They are not interchangeable with any other class. A compact "cube" style is available.
class J
These are nonrenewable, current-limiting fuses with an interrupting rating of 200,000 amperes. These fuses have a rejection feature so no other type of fuse can be installed in the same fuse holder.
class R
A nonrenewable, current-limiting fuse with an interrupting rating of 200,000 amperes. There is no time delay and they are not interchangeable with any other fuse.
class T
Sign lighting is considered to be a ____ load.
continuous
The connection between two or more portions of the equipment grounding conductor is a(n) ____.
equipment bonding jumpers
The connection of noncurrent-carrying metal items to the ground is ___.
equipment grounding
A neutral busbar is also called a grounding busbar
false
All circuits require grounding.
false
Because a service drop is installed high above the ground, the service-entrance conductors do not require insulation.
false
Circuit breakers are not permitted to serve as a disconnecting switch.
false
Circuit breakers have to be replaced after they detect an overcurrent.
false
Service conductors are always run overhead
false
Service-drop conductors are not allowed to pass over swimming pools.
false
Single-element fuses are designed for circuits with transient surge currents.
false
The main bonding jumper may be spliced.
false
These conductors originate at the main distribution panel and terminate at a load center.
feeders
The path from a circuit to earth is called a ____.
ground
When a circuit is connected to earth, it is said to be ____.
grounded
A grounding electrode conductor is connected between the ____.
grounding busbar and the grounding electrode
The conductor used to connect noncurrent-carrying metallic parts to the system grounding busbar is a ____.
grounding conductor
The device that establishes an electrical connection to earth is a ____.
grounding electrode
A sensor in a GFCI monitors the balance between the ____ conductors.
hot and neutral
Edison-base fuses are ____.
interchangeable
The highest fault current an OCPD is designed to handle is the device's ____ rating
interrupt
The connection between the grounded circuit conductor and the equipment grounding conductor at the service is a(n) ____.
main bonding jumpers
Time-delay fuses allow for ____.
momentary overloads
In system grounding, the grounded conductors are connected to the ____.
neutral busbar
When a conductor contacts grounded metal equipment, the ____ will trip.
overcurrent protection device
Too many devices on one circuit could cause a type of overcurrent known as ____.
overload
The conductors extending from the utility pole to the facilities equipment are called the ____.
service
When run overhead, the service is called the ____.
service drop
n a service-drop installation, the service conductors are connected to the SE conductors at the ____.
service head
When the service conductors are routed underground, it is called a ____.
service lateral
Conductors in a service drop are supported by a ____.
service mast
These conductors originate at distribution centers other than the main distribution center and extend to panelboards.
subfeeders
The connection between the grounded circuit conductor and the equipment grounding conductor at a separately derived system is a(n) ____.
system bonding jumpers
The connection of a circuit to the ground is ____.
system grounding
To determine track lighting load requirements, you must know the ____.
total length of track lighting
A drip loop is an extra 24² to 36² of service-entrance conductors right before the service head.
true
A phase conductor may be used as a grounded circuit conductor.
true
All electrical circuits are required to be protected against overcurrent.
true
An AFCI will detect arcing faults that are not detected by standard breakers or GFCIs.
true
As a general rule, devices that are double-insulated, guarded, or isolated are exempt from grounding.
true
Cartridge fuses are used in circuits over 120 volts or over 30 amps.
true
Current above 0.006 amps is enough to cause injury
true
Service conductors run underground are called a service lateral.
true
The Code requires any 125 V, 15 or 20 A branch circuit that is not GFCI protected be protected by an AFCI.
true
The ampere rating of an overcurrent protection device is usually the same as the current-carrying capacity of the circuit conductor.
true
The bonding jumpers must be the same size or larger than the grounding electrode conductor.
true
The fusible link can be replaced in renewable fuses.
true
The grounded conductor of a multiconductor cable is permitted to be bare.
true
The handle of the disconnect switch or main breaker must be mounted no higher than 6¢-6² above the floor.
true
The minimum vertical clearance of service-drop conductors depends on the service voltage and what is below the conductors.
true
The service head is connected to the meter enclosure.
true
The two types of grounding are system grounding and equipment grounding.
true
The voltage rating of a fuse should never be lower than the circuit rating.
true
Type S fuses must be used on all new installations and for replacement installations.
true
Typically, branch-circuit overcurrent devices are located in the power panel.
true
Voltage supply to large industrial plants can be as high as 13,800 V.
true
You may use a grounding wedge if you cannot use a bonding jumper.
true